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Warehouse execution systems ( WES ) [ 1 ] [ 2 ] are computerized systems used in warehouses and distribution centers to manage and orchestrate the physical flow of products from receiving through shipping. Warehouses are storage facilities for raw materials and parts used in manufacturing operations; distribution centers (DCs) are facilities that store and distribute finished goods to retail locations, consumers, and other end customers.
WES software organizes sequences and directs DC resources - both people and automation systems - necessary to move goods within a warehouse or DC, including: receiving, checking and sorting inbound products for storage (receiving); putaway of received goods into storage; replenishment of picking locations from storage; picking of customer orders; order assembly, checking and packing; loading and shipping. WES works in real time to enable the control of multiple elements of a warehouse process (e.g. inventory, personnel, machines and support services) where changing conditions in one work area or process may require changes in other areas or upstream/downstream processes (reactive).
WES is an intermediate step between an enterprise resource planning (ERP) system or warehouse management system WMS and the resources necessary to perform the various warehouse processes. These resources include workers as well as the process control systems used for warehouse automation, often referred to as warehouse control systems or WCS. The WES communicates with inventory and order management systems (such as an ERP or WMS) and the personnel and machinery (including conveyor systems and sorters) that perform the physical tasks involved in the warehouse processes.
WES emerged as a hybrid system that combined specific WMS functionality for picking and other material movement processes with warehouse control system (WCS) functionality for automated warehouses. [ 3 ] WCS is the software that controls the conveyor, sortation and other automated material handling systems that move cases, cartons, totes or pallets. In automated warehouses that deploy those types of material handling equipment, WES adds business process logic for planning, optimization and coordination of the work processes or work execution, including work sequencing and release. Many WES systems are tightly integrated with automated systems such as conveyors, sortation, pick-to-light, etc..
More recently, some WES systems have incorporated advanced process modeling and Artificial Intelligence technology that enable real-time adjustments in warehouse processes. As a result, warehouses become more flexible and agile in response. [ 4 ]
A WES has the ability to span across multiple areas of warehouse functionality that are traditionally managed by a variety of specialized software systems. WES can be deployed to encompass warehouse management functionality, warehouse control system functionality, material handling equipment (MHE) control, business intelligence and integration with host ERP systems. Encompassing this broad range of functionality is a distinct advantage for WES. As a result, the WES can leverage its visibility of lower level warehouse data to quickly adapt functionality needs for current conditions. This is especially true in facilities with automated systems. The WES can utilize its WCS roots to access connections to advanced picking and sortation systems thus offering an agile approach to optimizing operations in near real-time.
Another benefit of leveraging the visibility of lower level data across a broad range of warehouse functionality is the ability to provide unprecedented automated business intelligence . WES' access to and collection of data from various warehouse points can be utilized to provide not only advanced reporting and live dashboard functionality but business intelligence tools such as predictive analysis, prescriptive analysis, and issue detection. The WES can feed data into its business intelligence engine to be mined in near real-time so that DC operations can move beyond just being agile in response to changing conditions, to being proactive in making adjustments before conditions change. WES data can be analyzed to identify trends and predict operational conditions. For example, if operation peaks occur at the end of every month, warehouses can use WES feedback to ramp up staffing and equipment needs more efficiently to reduce overall costs. WES data can also be used to predict issues such as potential stock-outs or order fulfillment delays. Issue detection can also relate to preventative maintenance of warehouse equipment such as lift trucks, conveyor systems, etc. To illustrate this point, through analyzing vast amounts of data, the WES can predict when a conveyor motor may need to be replaced or when a lift truck may need servicing to reduce downtime. By collecting and analyzing data from various lower level warehouse points and taking proactive action, operation leads can use this functionality – which is unique to a WES – to make their facilities more efficient, safe and responsive to increasing customer service requirements.
There are a number of voices in the material handling industry that disagree with the creation of a separate term to define WES functionality.
"The new term being used by material handling software providers, integrators, and pretty much anyone associated with the warehousing industry is Warehouse Execution System (WES). According to a March article in DC Velocity, Warehouse Execution Systems can replace both the WMS and WCS by maintaining warehouse inventory records and driving the mechanization. It certainly seems like a very tasty fry sauce! What's important to remember when exploring options for a Warehouse Execution System is that the functionality is the same functionality that has always been offered! The key to finding the best system for your facility is not a flashy new name offering a combination or best of both worlds mix of solutions, but rather a modularized solution that allows you to define the functionality required." [ 5 ]
"Why invent a new term? ... there is no such thing as a WES, WCS, or WMS. (There is) simply Warehouse Software functionality needed to suit a business requirement. If the term WES fits fine, but as soon as you draw too many boundaries you create is another layer of interface and support." [ 6 ]
This is not a view held by all parties and many analysts in supply chain are touting the benefits of a stand alone WES for legacy systems and WMS software that is costly and time consuming to repurpose. Both WMS and WCS providers claim to have WES capabilities to varying degrees. In many cases a flexible WES is a great solution and is being used by midsize to Fortune 100 companies globally.
Right or wrong to create a new term, the term WES is being used in the material handling and distribution industry. The creation of the term arose as a "gap" was identified in the previous divisions of functionality required to operate a distribution facility. "As the demands of omni-channel distribution continue to pressure facilities and supply chains to run more efficiently, many distributors are realizing that the current functionalities of WMS and WCS are insufficient to align, automate, and synchronize the discrete processes needed to optimally control their order-fulfillment needs." [ 7 ]
A common occurrence in a large distribution center is that there are multiple varying types of large equipment and work processes provided by multiple vendors. The control of these complex and sometimes intricate functions is provided by the equipment supplier that control software is often called warehouse control system or WCS software. This situation leads to some facilities have multiple WCS software packages running. Without a WES layer this presents a terminology problem: The operation of all the equipment and process functions need to be coordinated and synchronized to provide the required facility objectives. This will require either a "Master WCS" or the WMS or ERP system to perform the function. A WES is the master WCS.
As in a manufacturing execution system (MES), the line between higher level and lower level control is blurred and not well defined, so it is with a WES. Manufacturing operations are significantly more mature than distribution when considering lean practices. [ 8 ] This is evidenced by the total lack of a Wikipedia article on "Lean distribution". Manufacturing operations face the same challenges of distribution operations having many different work cells or processes controlled by vendor provided control systems. A special category of software was created for manufacturing to integrate the overall production and coordinate the efforts of all production resources.
One of the byproducts of the rise of e-commerce, is the need for software to support the complexities of omni-channel fulfillment. "The omni-channel environment places enormous pressure on DCs to keep up with higher order volumes including rapid processing of small e-commerce orders." [ 9 ] The market for WES solutions continue to grow as DC operators seek productivity and support a high throughput.
Emerging functionality such as waveless processing is drawing attention to WES. Waveless processing requires constantly taking customer orders from a host system and releasing the work to the warehouse floor efficiently. This is in direct contrast to the typical WMS approach of batching the orders in waves. Waveless processing also allows orders to be worked as received, ensuring a faster turnaround time, and takes advantage of the WES grasp of near real-time information.
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Warida or Al Warida is an asterism of the Arabs. In the star catalogue of Al Achsasi al Mouakket , four stars are mentioned as belonging to it: Gamma Sagittarii , Delta Sagittarii , Epsilon Sagittarii and Eta Sagittarii .
The name is short for Arabic النعامة الواردة Al Naʽāma al Wārida , meaning "the ostrich going down to the water". This ostrich was thought of as going down to the river (the Milky Way) to drink, and another ostrich (σ, φ, τ, and ζ Sagittarii, al Sadira ) was thought of as coming back up. [ 1 ]
This constellation -related article is a stub . You can help Wikipedia by expanding it .
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In number theory , Waring's prime number conjecture is a conjecture related to Vinogradov's theorem , named after the English mathematician Edward Waring . It states that every odd number exceeding 3 is either a prime number or the sum of three prime numbers. It follows from the generalized Riemann hypothesis , [ 1 ] and ( trivially ) from Goldbach's weak conjecture .
This number theory -related article is a stub . You can help Wikipedia by expanding it .
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In number theory , Waring's problem asks whether each natural number k has an associated positive integer s such that every natural number is the sum of at most s natural numbers raised to the power k . For example, every natural number is the sum of at most 4 squares, 9 cubes, or 19 fourth powers. Waring's problem was proposed in 1770 by Edward Waring , after whom it is named. Its affirmative answer, known as the Hilbert–Waring theorem , was provided by Hilbert in 1909. [ 1 ] Waring's problem has its own Mathematics Subject Classification , 11P05, "Waring's problem and variants".
Long before Waring posed his problem, Diophantus had asked whether every positive integer could be represented as the sum of four perfect squares greater than or equal to zero. This question later became known as Bachet's conjecture, after the 1621 translation of Diophantus by Claude Gaspard Bachet de Méziriac , and it was solved by Joseph-Louis Lagrange in his four-square theorem in 1770, the same year Waring made his conjecture. Waring sought to generalize this problem by trying to represent all positive integers as the sum of cubes, integers to the fourth power, and so forth, to show that any positive integer may be represented as the sum of other integers raised to a specific exponent, and that there was always a maximum number of integers raised to a certain exponent required to represent all positive integers in this way.
For every k {\displaystyle k} , let g ( k ) {\displaystyle g(k)} denote the minimum number s {\displaystyle s} of k {\displaystyle k} th powers of naturals needed to represent all positive integers. Every positive integer is the sum of one first power, itself, so g ( 1 ) = 1 {\displaystyle g(1)=1} . Some simple computations show that 7 requires 4 squares, 23 requires 9 cubes, [ 2 ] and 79 requires 19 fourth powers; these examples show that g ( 2 ) ≥ 4 {\displaystyle g(2)\geq 4} , g ( 3 ) ≥ 9 {\displaystyle g(3)\geq 9} , and g ( 4 ) ≥ 19 {\displaystyle g(4)\geq 19} . Waring conjectured that these lower bounds were in fact exact values.
Lagrange's four-square theorem of 1770 states that every natural number is the sum of at most four squares. Since three squares are not enough, this theorem establishes g ( 2 ) = 4 {\displaystyle g(2)=4} . Lagrange's four-square theorem was conjectured in Bachet 's 1621 edition of Diophantus 's Arithmetica ; Fermat claimed to have a proof, but did not publish it. [ 3 ]
Over the years various bounds were established, using increasingly sophisticated and complex proof techniques. For example, Liouville showed that g ( 4 ) {\displaystyle g(4)} is at most 53. Hardy and Littlewood showed that all sufficiently large numbers are the sum of at most 19 fourth powers.
That g ( 3 ) = 9 {\displaystyle g(3)=9} was established from 1909 to 1912 by Wieferich [ 4 ] and A. J. Kempner , [ 5 ] g ( 4 ) = 19 {\displaystyle g(4)=19} in 1986 by R. Balasubramanian , F. Dress, and J.-M. Deshouillers , [ 6 ] [ 7 ] g ( 5 ) = 37 {\displaystyle g(5)=37} in 1964 by Chen Jingrun , [ 8 ] and g ( 6 ) = 73 {\displaystyle g(6)=73} in 1940 by Pillai . [ 9 ]
Let ⌊ x ⌋ {\displaystyle \lfloor x\rfloor } and { x } {\displaystyle \{x\}} respectively denote the integral and fractional part of a positive real number x {\displaystyle x} . Given the number c = 2 k ⌊ ( 3 / 2 ) k ⌋ − 1 < 3 k {\displaystyle c=2^{k}\lfloor (3/2)^{k}\rfloor -1<3^{k}} , only 2 k {\displaystyle 2^{k}} and 1 k {\displaystyle 1^{k}} can be used to represent c {\displaystyle c} ; the most economical representation requires ⌊ ( 3 / 2 ) k ⌋ − 1 {\displaystyle \lfloor (3/2)^{k}\rfloor -1} terms of 2 k {\displaystyle 2^{k}} and 2 k − 1 {\displaystyle 2^{k}-1} terms of 1 k {\displaystyle 1^{k}} . It follows that g ( k ) {\displaystyle g(k)} is at least as large as 2 k + ⌊ ( 3 / 2 ) k ⌋ − 2 {\displaystyle 2^{k}+\lfloor (3/2)^{k}\rfloor -2} . This was noted by J. A. Euler , the son of Leonhard Euler , in about 1772. [ 10 ]
The Ideal Waring Theorem would be an unconditional strengthening of Euler's observation:
Work by Dickson and Pillai in 1936, Rubugunday [ 11 ] in 1942, Niven in 1944 [ 12 ] and many others has proved that
Dickson's 1936 proof [ 13 ] applies when k > 6, and Pillai's [ 14 ] when k > 7, leaving g(4), g(5), and g(6) to be resolved as documented above.
No value of k {\displaystyle k} is known for which 2 k { ( 3 / 2 ) k } + ⌊ ( 3 / 2 ) k ⌋ > 2 k {\displaystyle 2^{k}\{(3/2)^{k}\}+\lfloor (3/2)^{k}\rfloor >2^{k}} . Mahler [ 15 ] proved that there can only be a finite number of such k {\displaystyle k} , and Kubina and Wunderlich [ 16 ] have shown that any such k {\displaystyle k} must satisfy k > 471 600 000 {\displaystyle k>471\,600\,000} , extending work of Stemmler. [ 17 ] Thus it is conjectured that this never happens, that is, g ( k ) = 2 k + ⌊ ( 3 / 2 ) k ⌋ − 2 {\displaystyle g(k)=2^{k}+\lfloor (3/2)^{k}\rfloor -2} for every positive integer k {\displaystyle k} .
The first few values of g ( k ) {\displaystyle g(k)} are:
From the work of Hardy and Littlewood , [ 18 ] the related quantity G ( k ) was studied with g ( k ). G ( k ) is defined to be the least positive integer s such that every sufficiently large integer (i.e. every integer greater than some constant) can be represented as a sum of at most s positive integers to the power of k . Clearly, G (1) = 1. Since squares are congruent to 0, 1, or 4 (mod 8), no integer congruent to 7 (mod 8) can be represented as a sum of three squares, implying that G (2) ≥ 4 . Since G ( k ) ≤ g ( k ) for all k , this shows that G (2) = 4 . Davenport showed [ 19 ] that G (4) = 16 in 1939, by demonstrating that any sufficiently large number congruent to 1 through 14 mod 16 could be written as a sum of 14 fourth powers (Vaughan in 1986 [ 20 ] and 1989 [ 21 ] reduced the 14 biquadrates successively to 13 and 12). The exact value of G ( k ) is unknown for any other k , but there exist bounds.
The number G ( k ) is greater than or equal to
In the absence of congruence restrictions, a density argument suggests that G ( k ) should equal k + 1 .
G (3) is at least 4 (since cubes are congruent to 0, 1 or −1 mod 9); for numbers less than 1.3 × 10 9 , 1 290 740 is the last to require 6 cubes, and the number of numbers between N and 2 N requiring 5 cubes drops off with increasing N at sufficient speed to have people believe that G (3) = 4 ; [ 22 ] the largest number now known not to be a sum of 4 cubes is 7 373 170 279 850 , [ 23 ] and the authors give reasonable arguments there that this may be the largest possible. The upper bound G (3) ≤ 7 is due to Linnik in 1943. [ 24 ] (All nonnegative integers require at most 9 cubes, and the largest integers requiring 9, 8, 7, 6 and 5 cubes are conjectured to be 239, 454, 8042, 1 290 740 and 7 373 170 279 850 , respectively.)
13 792 is the largest number to require 17 fourth powers (Deshouillers, Hennecart and Landreau showed in 2000 [ 25 ] that every number between 13 793 and 10 245 required at most 16, and Kawada, Wooley and Deshouillers extended [ 26 ] Davenport's 1939 result to show that every number above 10 220 required at most 16). Numbers of the form 31·16 n always require 16 fourth powers.
68 578 904 422 is the last known number that requires 9 fifth powers (Integer sequence S001057, Tony D. Noe, Jul 04 2017), 617 597 724 is the last number less than 1.3 × 10 9 that requires 10 fifth powers, and 51 033 617 is the last number less than 1.3 × 10 9 that requires 11.
The upper bounds on the right with k = 5, 6, ..., 20 are due to Vaughan and Wooley . [ 27 ]
Using his improved Hardy–Ramanujan–Littlewood method , I. M. Vinogradov published numerous refinements leading to
in 1947 [ 28 ] and, ultimately,
for an unspecified constant C and sufficiently large k in 1959. [ 29 ]
Applying his p -adic form of the Hardy–Ramanujan–Littlewood–Vinogradov method to estimating trigonometric sums, in which the summation is taken over numbers with small prime divisors, Anatolii Alexeevitch Karatsuba obtained [ 30 ] in 1985 a new estimate, for k ≥ 400 {\displaystyle k\geq 400} :
Further refinements were obtained by Vaughan in 1989. [ 21 ]
Wooley then established that for some constant C , [ 31 ]
Vaughan and Wooley's survey article from 2002 was comprehensive at the time. [ 27 ]
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In physical cosmology , warm inflation is one of two dynamical realizations of cosmological inflation . The other is the standard scenario, [ 1 ] [ 2 ] [ 3 ] sometimes called cold inflation. [ 4 ]
In warm inflation radiation production occurs concurrently with inflationary expansion. This is consistent with the conditions necessary for inflation as given by the Friedmann equations of general relativity , which simply require that the vacuum energy density dominates the energy content of the universe at time of inflation, and so does not prohibit some radiation to be present. As such the most general picture of inflation would include a radiation energy density component. The presence of radiation during inflation implies the inflationary phase could smoothly end into a radiation-dominated era without a distinctively separate reheating phase, [ 5 ] thus providing a solution to the graceful exit problem of inflation. [ 1 ] [ 2 ] [ 6 ] [ 7 ] [ 8 ]
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A warning system is any system of biological or technical nature deployed by an individual or group to inform of a future danger . Its purpose is to enable the deployer of the warning system to prepare for the danger and act accordingly to mitigate or avoid it. [ how? ] [ citation needed ]
Warnings cannot be effective unless people react to them. People are more likely to ignore a system that regularly produces false warnings (the cry-wolf effect ), but reducing the number of false warnings generally also increases the risk of not giving a warning when it is needed. [ 2 ] Some warnings are non-specific: for instance, the probability of an earthquake of a certain magnitude in a certain area over the next decade. Such warnings cannot be used to guide short-term precautions such as evacuation. Opportunities to take long-term precautions, such as better building codes and disaster preparedness , may be ignored. [ 3 ] [ better source needed ]
Historical beacon-based systems:
Space-based missile early warning systems :
Airborne early warning systems:
Ground-based early warning radar systems :
Optical sensors:
Emergency broadcasting:
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The warp-weighted loom is a simple and ancient form of loom in which the warp yarns hang freely from a bar, which is supported by upright poles which can be placed at a convenient slant against a wall. Bundles of warp threads are tied to hanging weights called loom weights which keep the threads taut. [ 1 ]
Evidence of the warp-weighted loom appears in the Neolithic period in central Europe. It is depicted in artifacts of Bronze Age in Greece. Loom weights from the Bronze Age were excavated in Miletos , a Greek city in Anatolia. [ 2 ] The warp-weighted looms were common throughout Europe, remaining in use in some areas of Scandinavia into the modern era.
In Sápmi , the warp-weighted loom is a living cultural heritage today, particularly in use for weaving of traditional blankets among the Sea Sami. [ 3 ]
The warp tension needed on a loom is roughly proportional to yarn diameter, and loom weights must be positioned in an even, level row, with all the threads hanging nearly straight down, for smooth weaving. This means that the shape of a loom weight limits a loom to certain thread counts , and the mass of the loom weight is related to the yarn used. This means that loom weights can be used to calculate the density and other properties of the fabric made on them. [ 4 ]
The warp-weighted loom may have originated in the Neolithic period. The earliest evidence of warp-weighted looms comes from sites belonging to the Starčevo culture in modern Serbia and Hungary from late Neolithic sites in Switzerland. [ 5 ] This loom was used in Ancient Greece , and spread north and west throughout Europe thereafter. [ 6 ] It was extensively used in the north among Scandinavian people. [ 7 ] For yet unknown reasons, the warp-weighted loom diminished in popularity and disappeared from common use. [ 8 ] The arrival of mechanized looms and industry may have contributed to this decline. It remained in use longest in Scandinavia; researcher Marta Hoffman found warp-weighted looms still in use on an isolated island off the coast of Norway and among the Sami of Norway and Finland in the 1950s. [ 9 ] Today, the warp-weighted loom is used as a hobby and in historic preservation societies. [ 10 ]
A warp-weighted loom has two upright posts (C); they support a horizontal beam (D), which is cylindrical so that the finished cloth can be rolled around it, allowing the loom to be used to weave a piece of cloth taller than the loom, and preserving an ergonomic working height. The warp threads (F, and A and B) hang from the beam and rest against the shed rod (E). The heddle-bar (G) is tied to some of the warp threads (A, but not B), using loops of string called leashes (H). So when the heddle rod is pulled out and placed in the forked sticks protruding from the posts (not lettered, no technical term given in citation), the shed (1) is replaced by the counter-shed (2). By passing the weft through the shed and the counter-shed, alternately, cloth is woven. [ 11 ]
The warp-weighted loom is used in a near-vertical position, and the fabric is woven from the top of the loom toward the ground. This allows the weaver to walk back-and-forth while working, so that wider cloth can be woven than is practical on a ground loom. On Ancient Greek vase paintings , two weavers, most often women, are shown working side-by-side on the warp-weighted loom. [ 10 ] This is unusual because most other looms require a resting position of standing or sitting. According to Artemidorus , if one dreams of a warp-weighted loom it means an upcoming journey. If one dreams of any other type of loom, one should expect rest. [ 12 ]
Additionally, extra warp thread can be wound around the weights. When a weaver has reached the bottom of the available warp, the completed section can be rolled around the top beam, and additional lengths of warp threads can be unwound from the weights to continue. This frees the weaver from vertical size constraints. [ 11 ]
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Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions is the debut non-fiction book by Lisa Randall , published in 2005, about particle physics in general and additional dimensions of space (cf. Kaluza–Klein theory ) in particular. The book has made it to top 50 at amazon.com , making it the world's first successful book on theoretical physics by a female author. [ citation needed ] She herself characterizes the book as being about physics and the multi-dimensional universe. [ 1 ] The book describes, at a non-technical level, theoretical models Professor Randall developed with the physicist Raman Sundrum, in which various aspects of particle physics (e.g. supersymmetry) are explained in a higher-dimensional braneworld scenario. These models have since generated thousands of citations.
She comments that her motivation for writing this book was her "thinking that there were people who wanted a more complete and balanced vision of the current state of physics." She has noticed there is a large audience that thinks physics is about the bizarre or exotic. She observes that when people develop an understanding of the science of particle physics and the experiments that produce the science, people get excited. "The upcoming experiments at the Large Hadron Collider (LHC) at CERN near Geneva will test many ideas, including some of the warped extra-dimensional theories I talk about." Another motivation was that she "gambled that there are people who really want to understand the physics and how the many ideas connect." [ 1 ]
Randall is currently a professor at Harvard University in Cambridge, Massachusetts , focusing on particle physics and cosmology . She stays current through her research into the nature of matter's most basic elements , and the forces that govern these most basic elements. Randall's experiences, which qualify her as an authority on the subject of the book, are her original "contributions in a wide variety of physics studies, including cosmological inflation , supersymmetry, grand unified theories , and aspects of string theory ". "As of last autumn, she was the most cited theoretical physicist in the world during the previous five years." In addition her most recent work involved extra dimensions . [ 2 ]
Her background research for the book, on the theories and experiments of extra dimensions and warped geometries, was published in the peer-reviewed Science magazine in 2002. [ 3 ]
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Warped linear predictive coding ( warped LPC or WLPC ) is a variant of linear predictive coding in which the spectral representation of the system is modified, for example by replacing the unit delays used in an LPC implementation with first-order all-pass filters . This can have advantages in reducing the bitrate required for a given level of perceived audio quality/intelligibility, especially in wideband audio coding.
Warped LPC was first proposed in 1980 by Hans Werner Strube.
This signal processing -related article is a stub . You can help Wikipedia by expanding it .
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Warren Richard Gish is the owner of Advanced Biocomputing LLC. He joined Washington University in St. Louis as a junior faculty member in 1994, and was a Research Associate Professor of Genetics from 2002 to 2007. [ 2 ] [ 3 ]
After initially studying physics, Gish obtained an A.B. degree in Biochemistry from University of California, Berkeley , and completed work for his Ph.D. degree in Molecular Biology at the same institution in 1988. [ 1 ]
Gish is primarily known for his contributions to NCBI BLAST , [ 4 ] [ 5 ] his creation of the BLAST Network Service and nr (non-redundant) databases, his 1996 release of the original gapped BLAST ( WU-BLAST 2.0 ), and most recently his development and support of AB-BLAST . At Washington University in St. Louis , Gish also led the genome analysis group which annotated all finished human, mouse and rat genome data produced by the University's Genome Sequencing Center from 1995 through 2002.
As a graduate student, Gish applied the Quine-McCluskey algorithm to the analysis of splice site recognition sequences. In 1985, with a view toward rapid identification of restriction enzyme recognition sites in DNA, Gish developed a DFA function library in the C language . The idea to apply a finite-state machine to this problem had been suggested by fellow graduate student and BSD UNIX developer Mike Karels . Gish's DFA implementation was that of a Mealy machine architecture, which is more compact than an equivalent Moore machine and hence faster. Construction of the DFA was O( n ), where n is the sum of the lengths of the query sequences. The DFA could then be used to scan subject sequences in a single pass with no backtracking in O( m ) time, where m is the total length of the subject(s). The method of DFA construction was recognized later as being a consolidation of two algorithms, Algorithms 3 and 4 described by Alfred V. Aho and Margaret J. Corasick . [ 6 ]
While working for U.C. Berkeley in December 1986, Gish sped up the FASTP program [ 7 ] (later known as FASTA [ 8 ] ) of William R. Pearson and David J. Lipman by 2- to 3-fold without altering the results. When the performance modifications were communicated to Pearson and Lipman, Gish further suggested that a DFA (rather than a lookup table) would yield faster k-tuple identification and improve the overall speed of the program by perhaps as much as 10% in some cases; however such marginal improvement even in the best case was deemed by the authors to not be worth the added code complexity. Gish also envisioned at this time a centralized search service, wherein all nucleotide sequences from GenBank would be maintained in memory to eliminate I/O bottlenecks—and stored in compressed form to conserve memory—with clients invoking FASTN searches remotely via the Internet.
Gish's earliest contributions to BLAST were made while working at the NCBI , starting in July 1989. Even in early prototypes BLAST was typically much faster than FASTA . Gish recognized the potential added benefit in this application of using a DFA for word-hit recognition. He morphed his earlier DFA code into a flexible form that he incorporated into all BLAST search modes. Others of his contributions to BLAST include: the use of compressed nucleotide sequences, both as an efficient storage format and as a rapid, native search format; parallel processing; memory-mapped I/O; the use of sentinel bytes and sentinel words at the start and end of sequences to improve the speed of word-hit extension; the original implementations of BLASTX , [ 9 ] TBLASTN [ 4 ] and TBLASTX (unpublished); the transparent use of external (plug-in) programs such as seg , xnu , and dust to mask low-complexity regions in query sequences at run time; the NCBI BLAST E-mail Service with optional public key-encrypted communications; the NCBI Experimental BLAST Network Service; the NCBI non-redundant ( nr ) protein and nucleotide sequence databases, typically updated on a daily basis with all data from GenBank , Swiss-Prot , and the PIR . Gish developed the first BLAST API , which was used in EST [ 10 ] annotation and Entrez data production, as well as in the NCBI BLAST version 1.4 application suite (Gish, unpublished). Gish was also the creator of and project manager for the earliest NCBI Dispatcher for distributed services (inspired by CORBA 's Object Request Broker ). First opened to outside users in December 1989, the NCBI Experimental BLAST Network Service, running the latest BLAST software on SMP hardware against the latest releases of the major sequence databases, quickly established the NCBI as a convenient, one-stop shop for sequence similarity searching.
At Washington University in St. Louis , Gish revolutionized similarity searching by developing the first BLAST suite of programs to combine rapid gapped sequence alignment
with statistical evaluation methods appropriate for gapped alignment scores.
The resulting search programs were significantly more sensitive but only marginally slower than ungapped BLAST ,
due to novel application of the BLAST dropoff score X during gapped alignment extension.
Sensitivity of gapped BLAST was further improved by the novel application
of Karlin-Altschul Sum statistics [ 11 ] to the evaluation of multiple, gapped alignment scores in all BLAST search modes.
Sum statistics were originally developed analytically for the evaluation of multiple, ungapped alignment scores.
The empirical use of Sum statistics in the treatment of gapped alignment scores was validated in collaboration with Stephen Altschul , from 1994 to 1995.
In May 1996, WU-BLAST version 2.0 with gapped alignments was publicly released in the form of a drop-in upgrade for existing users of ungapped NCBI BLAST and WU-BLAST (both at version 1.4, after having forked in 1994).
Little NIH funding was received for his WU-BLAST development, with an average of 20% FTE starting in November 1995, and ending shortly after the September 1997 release of the NCBI gapped BLAST (“blastall”).
As an option to WU-BLAST, Gish implemented a faster, more memory-efficient and more sensitive two-hit BLAST algorithm than was used by the NCBI software for many years.
In 1999, Gish added support to WU-BLAST for the Extended Database Format (XDF), the first BLAST database format capable of accurately representing the entire draft sequence of the human genome in full-length chromosome sequence objects.
This was also the first time any BLAST package introduced a new database format transparently to existing users, without abandoning support for prior formats, as a result of abstracting the database I/O functions away from the data analysis functions.
WU-BLAST with XDF was the first BLAST suite to support indexed-retrieval of NCBI standard FASTA-format sequence identifiers (including the entire range of NCBI identifiers); the first
to allow retrieval of individual sequences in part or in whole, natively, translated or reverse-complemented; and the first able to dump the entire contents of a BLAST database back into human-readable FASTA format .
In 2000, unique support for reporting of links (consistent sets of HSPs; also called chains in some later software packages) was added,
along with the ability for users to limit the distance between HSPs allowed in the same set to a biologically relevant length ( e.g., the length of the expected longest intron in the species of interest)
and with the distance limitation entering into the calculation of E -values.
Between 2001 and 2003, Gish improved the speed of the DFA code used in WU-BLAST.
Gish also proposed multiplexing query sequences to speed up BLAST searches by an order of magnitude or more (MPBLAST); implemented segmented sequences with internal sentinel bytes, in part to aid multiplexing with MPBLAST and in part to aid analysis of segmented query sequences from shotgun sequencing assemblies;
and directed use of WU-BLAST as a fast, flexible search engine for accurately identifying and masking genome sequences for repetitive elements and low-complexity sequences (the MaskerAid [ 12 ] package for RepeatMasker).
With doctoral student Miao Zhang, Gish directed development of EXALIN, [ 13 ] which significantly improved the accuracy of spliced alignment predictions,
by a novel approach that combined information from donor and acceptor splice site models with information from sequence conservation.
Although EXALIN performed full dynamic programming by default, it could optionally utilize the output from WU-BLAST to seed the dynamic programming and speed up the process by about 100-fold with little loss of sensitivity or accuracy.
In 2008, Gish founded Advanced Biocomputing, LLC, where he continues to improve and support the AB-BLAST package. [ citation needed ]
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Warren Richard Roper FRS FRSNZ FNZIC (born 1938) is a New Zealand chemist and Emeritus Professor at the University of Auckland .
Roper was educated at Nelson College from 1952 to 1956, and was dux in his final year. [ 1 ] He then studied chemistry at the University of Canterbury , and undertook his PhD under the supervision of CJ Wilkins. He completed his PhD in 1963, and spent three years undertaking postdoctoral research at the University of North Carolina in the United States before returning to New Zealand. At that point Roper was appointed as lecturer at the University of Auckland, where he remained until his retirement (apart from visiting lectureships at other institutions). He mentored several notable students, including Anthony Hill and Penelope Brothers .
Roper's research has focused on synthetic and structural organometallic chemistry , [ 2 ] and particularly compounds with metal-carbon, - silicon , - tin or - boron bonds. [ 3 ] As his postdoctoral research group had an interest in Vaska's complex , Roper too developed a program on M-PPh 3 -CO complexes of the platinum metals. A recurring themes of the work was the reactivity of coordinated ligands, especially simple ligands. These ligands included dichlorocarbene , carbonyl sulfide , carbonyl selenide , and carbonyl telluride , and PH 2 . Prior to his work, metal carbene complexes were restricted to early metals. Roper greatly expanded the scope of carbene ligands with his preparation of Os(CH 2 )(NO)(Cl)(PPh 3 ) 2 . [ 4 ]
He was made a fellow of the Royal Society of New Zealand (RSNZ) in 1984, [ 5 ] and a fellow of the Royal Society in 1989. [ 2 ] The RSNZ awarded Roper the Hector Memorial Medal in 1991. [ 6 ] He gave a valedictory address at the 2006 New Zealand Institute of Chemistry Conference in honour of his retirement. [ 7 ]
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The Warsak Canal Project is an initiative focused on enhancing agricultural practices in the Peshawar and Nowshera districts of Khyber Pakhtunkhwa , Pakistan.
The Warsak Canal Project, also recognized as the Remodeling of Warsak Canal System Project, is projected to augment the water flow in the Warsak canal to a capacity of up to 1250 cusecs. [ 1 ] [ 2 ] This heightened water flow is expected to significantly enhance farming and agricultural activities in the region. [ 3 ]
The initiative aims to provide irrigation to numerous acres of land in Peshawar and Nowshera . This effort will not only convert arid land into fertile grounds but also address water scarcity challenges for local farmers. [ 4 ] [ 5 ]
As of June 2023, the project is in the construction phase, being supervised by Fazal Elahi , the Caretaker Minister for Irrigation. The project encompasses the refurbishment of the Warsak canal and the establishment of a new tunnel. [ 5 ] [ 2 ] [ 3 ] The anticipated completion date for the project is set for February 2027. [ 1 ]
The former Chief Minister of Khyber Pakhtunkhwa , Mahmood Khan , has communicated his wish for the updated project plan (referred to as PC-1) to be sanctioned during the forthcoming meeting of the executive committee of the National Economic Council . [ 3 ]
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In computer network security, warshipping is using a physical package delivery service to deliver an attack vector to a target. This concept was first described [ 1 ] in 2008 at the DEF CON hacking convention by Robert Graham and David Maynor as part of a talk entitled “Bringing Sexy Back: Breaking in with Style”, that included various penetration testing methods. In their implementation, an iPhone box was modified to include a larger battery, which powered a jailbroken iPhone. A first-generation iPhone was chosen for this attack based on the reported run-time of 5 days when coupled with an external battery, whereas newer 3G iPhones of the era would reportedly run for 1½ days. A social engineering pretext was described that would trick the recipient into believing they had won an iPhone, in order to explain the shipment.
The advancement of low-power electronics, thanks in part to maker culture , has greatly increased the effectiveness of this methodology as a credible method of attacking networks. In 2019, IBM X-Force Red coined the name “Warshipping” and described an attack platform that included several low-cost components that could be combined, shipped to targets, and controlled remotely for 2–3 weeks. A solar component was also described to allow the devices to run indefinitely. [ 2 ] [ 3 ]
Aspects of a modern warshipping attack include the following:
The increasing use of large, online retailers contributes to the relevancy of this attack. In 2019, the United States Postal Service reports that they deliver 484.8 million mailpieces per day. [ 4 ] The name is by analogy with wardriving and wardialling . [ 5 ]
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Warwick Bowen is an Australian quantum physicist and nanotechnologist at The University of Queensland . He leads the Quantum Optics Laboratory, [ 1 ] is Director of the UQ Precision Sensing Initiative [ 2 ] and is one of three Theme Leaders of the Australian Centre for Engineered Quantum Systems. [ 3 ]
Bowen attended the University of Otago in New Zealand, where he received a Bachelor of Science degree with Honours in Physics in 1999. He went on to earn a PhD in Physics at the Australian National University in 2004, and was awarded the 2004 Bragg Gold Medal for Excellence in Physics from the Australian Institute of Physics , which recognizes the best PhD thesis in physics by a student from an Australian university. [ 4 ]
Bowen went on to become Moore Postdoctoral Fellow at the California Institute of Technology in 2004 and 2005.
In 2005, Bowen was recruited to a faculty position in the Department of Physics at the University of Otago. Then, in 2008, he commenced a faculty position at the School of Mathematics and Physics at the University of Queensland, where he became a full Professor in 2016.
He was awarded a five-year Australian Research Council (ARC) [ 5 ] Queen Elizabeth II Fellowship in 2009, and went on to become an ARC Future Fellow in 2015. [ 6 ]
Since 2013, while based at the University of Queensland, Bowen has been a Principal Investigator in the US Air Force Office of Scientific Research (AFOSR) in Biophysics Program. [ 7 ]
In 2017 Bowen established and became Director of the University of Queensland Precision Sensing Initiative. [ 2 ] In 2018, Bowen was also awarded an Adjunct Professorship at the Australian Institute for Bioengineering and Nanotechnology at the University of Queensland.
Bowen’s research focusses on the interface of nanotechnology and quantum science, including nanophotonics, nanomechanics, quantum optomechanics and photonic/quantum sensing. His work spans from addressing very fundamental questions about how quantum physics transitions into our everyday world at large scales, to the development of novel applications in navigation, biomedical diagnostics, quantum communications and computation. He has worked with industry partners including Boeing, NASA Glenn Laboratories and Lockheed Martin.
In particular, Bowen has focussed on quantum-enhanced sensing and communication technologies, including development of the first prototype quantum light source at gravitational wave frequencies, planned to be installed in the Laser Interferometry Gravitational Wave Observatory (LIGO) in 2018. [ 8 ] [ 9 ] Recently, his research group has pioneered the application of quantum optomechanical techniques in magnetometry, ultrasound sensing and microscopy of biological systems. [ 10 ] [ 11 ] [ 12 ] This includes the first demonstrations that quantum correlations could improve the sensitivity and resolution of light microscopes, [ 13 ] [ 14 ] experiments that also were the first to apply quantum corrections to improve biological measurements; and the first demonstration of absolute quantum advantage in sensing that employs quantum correlations, [ 15 ] showing that quantum correlations can provide image clarity beyond the usual photodamage limits of microscopy. These were longstanding challenges widely recognised in the field of quantum optics. [ 16 ] with the latter being a key milestone in the UK Quantum Technologies Roadmap. [ 17 ]
Prof Bowen is also developing nanophotonic techniques to control superfluid helium, an exotic quantum liquid and building block for future quantum technologies. Using these techniques, his research lab demonstrated direct laser cooling of a liquid [ 18 ] and the tracking of quantum vortices in two-dimensional superfluid helium, both for the first time, [ 19 ] and showed that very low threshold lasing of superfluid sound waves was possible. [ 20 ]
In 2020 Warwick Bowen founded the company Elemental Instruments with co-founder Dr Glen Harris. Elemental Instruments develops scientific instrumentation for quantum technologies, chemical and material analysis, medical imaging, and university/school laboratories and demonstrations. A key focus of the company is compact low-power solutions to generate strong, uniform and tuneable magnetic fields.
Warwick Bowen has received a range of awards and honours, including
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A washaway is a particular kind of landslide that can affect construction structures such as cuttings , embankments and bridges . They are thus a hazard to railways and road traffic.
The biggest danger with washaways is that they may be difficult to spot in time to stop short of the point where one falls over the edge and/or into the water where one may drown.
An embankment that is washed away can be repaired or restored by replacing the washed away earth, which is necessarily large because embankments have a gentle slope.
A quicker method is to replace the washed out earth with a criss-cross structure of timber steepers called a pigsty which is only slightly wider than the track itself. The pigsty has alternating layers of transverse and longitudinal layers of these sleepers, which contains a lot of air which saves weight. [ 1 ] [ 2 ] Steel and concrete sleepers are not necessarily suitable for this purpose as they are either not square or fragile.
The sleepers in the pigsty can be reused when the washaway is fully repaired. Rails can substitute for the sleepers. The hollow space inside the pigsty should be able to act as a culvert. [ 3 ]
A mechanical railway signal that is normally "green" can be put to "red" if a link in the pulling wire is disengaged by a slump of the earth beneath.
An electrical railway signal that is normally green can be put to red if a contact is opened circuited by a slump of the earth beneath. One side of contact might be attached to the sleepers , while the other side is buried in the ballast beneath. To protect against a false feed keeping the warning signal green, the circuit should be double cut so that false feeds will connect positive to negative and blow a fuse, forcing the warning signal to red. A similar setup might be used to protect bridges likely to be hit by ship collisions, as with the 1993 Big Bayou Canot train wreck .
Railway accidents involving bridge washaways include:
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Washboarding or corrugation [ 1 ] is the formation of periodic, transverse ripples in the surface of gravel and dirt roads. Washboarding occurs in dry, granular road material [ 2 ] with repeated traffic, traveling at speeds above 8.0 kilometres per hour (5 mph). [ 3 ] Washboarding creates an uncomfortable ride for the occupants of traversing vehicles and hazardous driving conditions for vehicles that travel too fast to maintain traction and control. [ 4 ]
Washboarding or corrugation of roads comprises a series of ripples, which occur with the passage of wheels rolling over unpaved roads at speeds sufficient to cause bouncing of the wheel on the initially unrippled surface and take on the appearance of a laundry washboard . Most studies of washboarding pertain to granular materials, including sand and gravel. [ 1 ] [ 5 ] However, other work suggests that the phenomenon may occur in material which has some binding of particles, e.g. clay-like soils. [ 6 ]
Highway department experts in the mid-1920s were aware that traffic volume and speed were primary causes of corrugations on gravel roads and cited the role of drive wheels tossing material as a factor. [ 7 ] [ 8 ]
Laboratory-scale studies of the phenomenon typically employ a wheel or a blade, which is towed behind a pivot point, tracing a circular path through a pan of the material under examination. These studies have investigated a variety of granular and viscous, even fluid, materials. [ 1 ] [ 6 ] In the laboratory, washboarding has been studied for a range of parameters, including the thickness and grain size of the material for varied wheel sizes, shapes, and masses. Experiments produced ripples for each parameter, above a threshold speed, when the wheel (or blade) began to bounce. [ 1 ] Experiments also show that the pattern can move either against the direction of motion or in the direction of motion. They also show that a passive, non-driving wheel suffices to create corrugations and that displacement of material, rather than ejection, is the dominant mechanism. [ 1 ]
Several articles about real-life washboarding on roads cite South Dakota Local Transportation Assistance Program (LTAP) Special Bulletin #29, “Dealing with Washboarding,” by Ken Skorseth. [ 2 ] [ 9 ] Those sources attribute washboarding to three causes: dry granular materials, vehicle speeds, and the quality of the granular material. Other factors cited include vehicle speed, traffic volume, and hard acceleration or braking. The sources also claim that light vehicles are more likely to cause washboarding than heavy trucks. [ 9 ]
Highway department guidance suggests that choice of gravel can be key to mitigating washboarding. They cite "sieve analysis" tests that use a series of screens or sieves to characterize the sizes of particles contained within a gravel sample. Highway department guidance suggests a range of particle sizes from stones that are in the 1-inch (25 mm) range, mixed with progressively finer particles to include a small fraction of fine particles that bind the larger particles together. They also mention the role of equipment that can re-blend and smooth surfaces that have corrugated.
In 1925, the Nevada Department of Highways advocated mitigating corrugations with crushed pit-run gravel, using material 1 inch (25 mm) and smaller, including only the fines from crushing. [ 7 ] Contemporaneous advice from Colorado was to use a well-graded gravel, not exceeding 1.25 inches (32 mm) and including 25–40% fines passing a 0.25-inch (6.4 mm) sieve, but not more than 5% passing a #10 (2.0-mm) [ 10 ] sieve. [ 11 ] The maintenance advice from Colorado was to drag or grade the road frequently, applying light volumes of new gravel with minimal sand content and providing good drainage with a crown. The same source advises reduction of traffic speed. [ 8 ]
Guidance based on South Dakota LTAP Special Bulletin #29 and FHWA guidance (2000) from the same source [ 12 ] suggests that the surface gravel "should be a blend of stone, sand and fines that will compact into a dense, tight mass with an almost impervious surface ." It emphasizes the proper gradation of gravel—100% [ 12 ] passing the 0.75 inches (19 mm)) sieve—to have fractured stone to "interlock" and 4–15% fines [ 12 ] passing the #200 (75-μm) [ 10 ] sieve [ 11 ] to act as a binder and create cohesiveness in the gravel; substituting other binders, such as clay is also recommended. Alternately, one can incorporate reclaimed asphalt in a half-and-half blend with quarried gravel to improve the binding properties of the surface. For existing washboarded surfaces, the bulletin recommends using a grader to cut and blend existing material to a depth one inch or more below the bottom of the washboarded segment and then add the new material into the top layer. Useful equipment includes a blade with rotating scarifying teeth or a replaceable bit-type cutting edge attached to the moldboard blade of the earth-moving equipment. [ 9 ]
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In physics , Washburn's equation describes capillary flow in a bundle of parallel cylindrical tubes; it is extended with some issues also to imbibition into porous materials. The equation is named after Edward Wight Washburn ; [ 1 ] also known as Lucas–Washburn equation , considering that Richard Lucas [ 2 ] wrote a similar paper three years earlier, or the Bell-Cameron-Lucas-Washburn equation , considering J.M. Bell and F.K. Cameron's discovery of the form of the equation in 1906. [ 3 ]
In its most general form the Lucas Washburn equation describes the penetration length ( L {\displaystyle L} ) of a liquid into a capillary pore or tube with time t {\displaystyle t} as L = ( D t ) 1 2 {\displaystyle L=(Dt)^{\frac {1}{2}}} , where D {\displaystyle D} is a simplified diffusion coefficient. [ 4 ] This relationship, which holds true for a variety of situations, captures the essence of Lucas and Washburn's equation and shows that capillary penetration and fluid transport through porous structures exhibit diffusive behaviour akin to that which occurs in numerous physical and chemical systems. The diffusion coefficient D {\displaystyle D} is governed by the geometry of the capillary as well as the properties of the penetrating fluid.
A liquid having a dynamic viscosity η {\displaystyle \eta } and surface tension γ {\displaystyle \gamma } will penetrate a distance L {\displaystyle L} into the capillary whose pore radius is r {\displaystyle r} following the relationship:
L = γ r t cos ( ϕ ) 2 η {\displaystyle L={\sqrt {\frac {\gamma rt\cos(\phi )}{2\eta }}}}
Where ϕ {\displaystyle \phi } is the contact angle between the penetrating liquid and the solid (tube wall).
Washburn's equation is also used commonly to determine the contact angle of a liquid to a powder using a force tensiometer . [ 5 ]
In the case of porous materials, many issues have been raised both about the physical meaning of the calculated pore radius r {\displaystyle r} [ 6 ] and the real possibility to use this equation for the calculation of the contact angle of the solid. [ 7 ] The equation is derived for capillary flow in a cylindrical tube in the absence of a gravitational field , but is sufficiently accurate in many cases when the capillary force is still significantly greater than the gravitational force.
In his paper from 1921 Washburn applies Poiseuille's Law for fluid motion in a circular tube. Inserting the expression for the differential volume in terms of the length l {\displaystyle l} of fluid in the tube d V = π r 2 d l {\displaystyle dV=\pi r^{2}dl} , one obtains
where ∑ P {\displaystyle \sum P} is the sum over the participating pressures, such as the atmospheric pressure P A {\displaystyle P_{A}} , the hydrostatic pressure P h {\displaystyle P_{h}} and the equivalent pressure due to capillary forces P c {\displaystyle P_{c}} . η {\displaystyle \eta } is the viscosity of the liquid, and ϵ {\displaystyle \epsilon } is the coefficient of slip, which is assumed to be 0 for wetting materials. r {\displaystyle r} is the radius of the capillary. The pressures in turn can be written as
where ρ {\displaystyle \rho } is the density of the liquid and γ {\displaystyle \gamma } its surface tension . ψ {\displaystyle \psi } is the angle of the tube with respect to the horizontal axis. ϕ {\displaystyle \phi } is the contact angle of the liquid on the capillary material. Substituting these expressions leads to the first-order differential equation for
the distance the fluid penetrates into the tube l {\displaystyle l} :
The Washburn constant may be included in Washburn's equation.
It is calculated as follows:
In the derivation of Washburn's equation, the inertia of the liquid is ignored as negligible. This is apparent in the dependence of length L {\displaystyle L} to the square root of time, L ∝ t {\displaystyle L\propto {\sqrt {t}}} , which gives an arbitrarily large velocity dL/dt for small values of t . An improved version of Washburn's equation, called Bosanquet equation , takes the inertia of the liquid into account. [ 10 ]
The penetration of a liquid into the substrate flowing under its own capillary pressure can be calculated using a simplified version of Washburn's equation: [ 11 ] [ 12 ]
where the surface tension-to-viscosity ratio [ γ η ] 1 2 {\displaystyle \left[{\tfrac {\gamma }{\eta }}\right]^{\frac {1}{2}}} represents the speed of ink penetration into the substrate. In reality, the evaporation of solvents limits the extent of liquid penetration in a porous layer and thus, for the meaningful modelling of inkjet printing physics it is appropriate to utilise models which account for evaporation effects in limited capillary penetration.
According to physicist and Ig Nobel prize winner Len Fisher , the Washburn equation can be extremely accurate for more complex materials including biscuits . [ 13 ] [ 14 ] Following an informal celebration called national biscuit dunking day, some newspaper articles quoted the equation as Fisher's equation . [ 15 ]
The flow behaviour in traditional capillary follows the Washburn's equation. Recently, novel capillary pumps with a constant pumping flow rate independent of the liquid viscosity [ 16 ] [ 17 ] [ 18 ] [ 19 ] were developed, which have a significant advantage over the traditional capillary pump (of which the flow behaviour is Washburn behaviour, namely the flow rate is not constant). These new concepts of capillary pump are of great potential to improve the performance of lateral flow test .
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Washdown (also wash down ) is the process of cleaning or washing a surface for appearance, sanitation, or removal of contamination. It may involve pressure washing . Sometimes wash down involves rinsing with fresh water; other times it involves use of detergents and other chemicals.
Regulations for processing sensitive products such as food and pharmaceuticals require periodic thorough washing and sanitizing. Some equipment can be moved to a central washing facility. Other machinery must be cleaned in place using portable specialized washing equipment. High-pressure cleaning is used with water and cleaning chemicals. [ 1 ] [ 2 ] A washdown is usually a manual operation and is designed to kill bacteria and other microorganisms . Automatic cleaning of industrial equipment is often carried out by clean-in-place (CIP) and/or steam-in-place (SIP) operations. CIP ( CIP ) systems often make use of programmable logic controllers and SCADA software.
Washdown is the process of using a stream of water to clean a flat or nearly flat outdoor surface. Typically the area cleaned is a large expanse of concrete or asphalt. The area is cleaned of dirt and debris with the force and dissolving power of stream of water projected from a hose. Generally, one person holds and aims the hose, though if the hose is longer than 300 feet then another person may be required to help move the hose itself. Water is typically squirted from the hose at a pressure of 300 psi. The hose itself can vary in length from 75 to 425 feet. Typically the hose when used by a single person is 300 feet long. The hose itself carries water from a water main which attaches to the hose through what is called a “stinger“. The stinger screws into the water main pipe and is held there.
Also, the stinger as it is pushed down into the water supply pipe opens a seal which releases the water into the hose. At the other end of the hose a nozzle regulates the flow of water and allows for a large fanned-out spray, as well as a more concentrated stream termed a needlepoint.
Military and civil defense have exercises to remove chemical and radioactive contamination from vehicles, buildings, people, etc. [ 3 ] [ 4 ]
This industry -related article is a stub . You can help Wikipedia by expanding it .
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A washout is the sudden erosion of soft soil or other support surfaces by a gush of water , usually occurring during a heavy downpour of rain (a flash flood ) or other stream flooding . These downpours may occur locally in a thunderstorm or over a large area, such as following the landfall of a tropical cyclone . If a washout occurs in a crater -like formation, it is called a sinkhole , and it usually involves a leaking or broken water main or sewerage pipes . Other types of sinkholes, such as collapsed caves , are not washouts.
Widespread washouts can occur in mountainous areas after heavy rains, even in normally dry ravines . A severe washout can become a landslide , or cause a dam break in an earthen dam . Like other forms of erosion, most washouts can be prevented by vegetation whose roots hold the soil and/or slow the flow of surface and underground water. Deforestation increases the risk of washouts. Retaining walls and culverts may be used to try to prevent washouts, although particularly severe washouts may even destroy these if they are not large or strong enough.
In road and rail transport , a washout is the result of a natural disaster where the roadbed is eroded away by flowing water, usually as the result of a flood . [ 1 ] When a washout destroys a railroad's right-of-way , the track is sometimes left suspended in midair across the newly formed gap, or it dips down into a ditch. This phenomenon is discussed in more detail under the term erosion . Bridges may collapse due to bridge scour around one or more bridge abutments or piers.
In 2004, the remnants of Hurricane Frances , and then Hurricane Ivan , caused a large number of washouts in western North Carolina and other parts of the southern Appalachian Mountains , closing some roads for days and parts of the Blue Ridge Parkway for months. Other washouts have also caused train wrecks where tracks have been unknowingly undermined. Motorists have also driven into flooded streams at night, unaware of a new washout on the road in front of them until it is too late to brake , sometimes prompting a high-water rescue .
Major washouts can also ruin pipelines or undermine utility poles or underground lines, interrupting public utilities .
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Waste-to-energy (WtE ) or energy-from-waste ( EfW ) refers to a series of processes designed to convert waste materials into usable forms of energy, typically electricity or heat. As a form of energy recovery, WtE plays a crucial role in both waste management and sustainable energy production by reducing the volume of waste in landfills and providing an alternative energy source.
The most common method of WtE is direct combustion of waste to produce heat, [ 1 ] which can then be used to generate electricity via steam turbines. This method is widely employed in many countries and offers a dual benefit: it disposes of waste while generating energy, making it an efficient process for both waste reduction and energy production.
In addition to combustion, other WtE technologies focus on converting waste into fuel sources. [ 2 ] For example, gasification and pyrolysis are processes that thermochemically decompose organic materials in the absence of oxygen to produce syngas, a synthetic gas primarily composed of hydrogen, carbon monoxide, and small amounts of carbon dioxide. This syngas can be converted into methane , methanol , ethanol , or even synthetic fuels , which can be used in various industrial processes or as alternative fuels in transportation.
Furthermore, anaerobic digestion , a biological process, converts organic waste into biogas (mainly methane and carbon dioxide) through microbial action. This biogas can be harnessed for energy production or processed into biomethane, which can serve as a substitute for natural gas.
The WtE process contributes to circular economy principles by transforming waste products into valuable resources, reducing dependency on fossil fuels, and mitigating greenhouse gas emissions. However, challenges remain, particularly in ensuring that emissions from WtE plants, such as dioxins and furans , are properly managed to minimize environmental impact. Advanced pollution control technologies are essential to address these concerns and ensure WtE remains a viable, environmentally sound solution.
WtE technologies present a significant opportunity to manage waste sustainably while contributing to global energy demands. They represent an essential component of integrated waste management strategies and a shift toward renewable energy systems. As technology advances, WtE may play an increasingly critical role in both reducing landfill use and enhancing energy security.
The first incinerator or "Destructor" was built in Nottingham , UK, in 1874 by Manlove, Alliott & Co. Ltd. to the design of Alfred Fryer. [ 3 ] The USA's first incinerator was built in 1885 on Governors Island in New York, New York . [ 4 ] In 1903 first waste-to-energy unit in Denmark was built in Frederiksberg , Copenhagen . [ 5 ] The first facility in the Czech Republic was built in 1905 in Brno . [ 6 ]
Gasification and pyrolysis processes have been known and used for centuries and for coal as early as the 18th century.... Development technologies for processing [residual solid mixed waste] has only become a focus of attention in recent years stimulated by the search for more efficient energy recovery. (2004) [ 7 ]
Incineration, the combustion of organic material such as waste with energy recovery, is the most common WtE implementation. All new WtE plants in OECD countries incinerating waste (residual MSW , commercial, industrial or RDF ) must meet strict emission standards, including those on nitrogen oxides (NO x ), sulphur dioxide (SO 2 ), heavy metals and dioxins . [ 8 ] [ 9 ] Hence, modern incineration plants are vastly different from old types, some of which neither recovered energy nor materials. Modern incinerators reduce the volume of the original waste by 95-96 percent, depending upon composition and degree of recovery of materials such as metals from the ash for recycling. [ 5 ]
Incinerators may emit fine particulate , heavy metals, trace dioxin and acid gas , even though these emissions are relatively low [ 10 ] from modern incinerators. Other concerns include proper management of residues: toxic fly ash , which must be handled in hazardous waste disposal installation as well as incinerator bottom ash (IBA), which must be reused properly. [ 11 ]
Critics argue that incinerators destroy valuable resources and they may reduce incentives for recycling. [ 11 ] The question, however, is an open one, as European countries which recycle the most (up to 70%) also incinerate to avoid landfilling . [ 12 ]
Incinerators have electric efficiencies of 14-28%. [ 11 ] In order to avoid losing the rest of the energy, it can be used for e.g. district heating ( cogeneration ). The total efficiencies of cogeneration incinerators are typically higher than 80% (based on the lower heating value of the waste).
The method of incineration to convert municipal solid waste (MSW) is a relatively old method of WtE generation. Incineration generally entails burning waste (residual MSW, commercial, industrial and RDF) to boil water which powers steam generators that generate electric energy and heat to be used in homes, businesses, institutions and industries. One problem associated is the potential for pollutants to enter the atmosphere with the flue gases from the boiler. These pollutants can be acidic and in the 1980s were reported to cause environmental degradation by turning rain into acid rain . Modern incinerators incorporate carefully engineered primary and secondary burn chambers, and controlled burners designed to burn completely with the lowest possible emissions, eliminating, in some cases, the need for lime scrubbers and electro-static precipitators on smokestacks.
By passing the smoke through the basic lime scrubbers, any acids that might be in the smoke are neutralized which prevents the acid from reaching the atmosphere and hurting the environment. Many other devices, such as fabric filters, reactors, and catalysts destroy or capture other regulated pollutants. [ 13 ] According to the New York Times, modern incineration plants are so clean that "many times more dioxin is now released from home fireplaces and backyard barbecues than from incineration". [ 14 ] According to the German Environmental Ministry, "because of stringent regulations, waste incineration plants are no longer significant in terms of emissions of dioxins, dust, and heavy metals". [ 15 ]
Compared with other waste to energy technologies, incineration seems to be the most attractive due to its higher power production efficiency, lower investment costs, and lower emission rates. Additionally, incineration yields the highest amount of electricity with the highest capacity to lessen pile of wastes in landfills through direct combustion. [ 16 ]
One process that is used to convert plastic into fuel is pyrolysis , the thermal decomposition of materials at high temperatures in an inert atmosphere. It involves change of chemical composition and is mainly used for treatment of organic materials. In large scale production, plastic waste is ground and melted and then pyrolyzed. Catalytic converters help in the process. The vapours are condensed with oil or fuel and accumulated in settling tanks and filtered. Fuel is obtained after homogenation and can be used for automobiles and machinery. It is commonly termed as thermofuel or energy from plastic. [ 17 ]
A new process uses a two-part catalyst, cobalt and zeolite, to convert plastics into propane . It works on polyethylene and polypropylene and the propane yield is approximately 80%. [ 18 ]
There are a number of other new and emerging technologies that are able to produce energy from waste and other fuels without direct combustion. Many of these technologies have the potential to produce more electric power from the same amount of fuel than would be possible by direct combustion. This is mainly due to the separation of corrosive components (ash) from the converted fuel, thereby allowing higher combustion temperatures in e.g. boilers , gas turbines , internal combustion engines , fuel cells . Some advanced technologies are able to efficiently convert the energy in the feedstocks into liquid or gaseous fuels, using heat but in the absence of oxygen, without actual combustion, by using a combination of thermal technologies. Typically, they are cleaner, as the feedstock is separated prior to treatment to remove the unwanted components:
Thermal treatment technologies include:
Non-thermal technologies:
During the 2001–2007 period, the waste-to-energy capacity increased by about four million metric tons per year.
Japan and China each built several plants based on direct smelting or on fluidized bed combustion of solid waste. In China there were about 434 waste-to-energy plants in early 2016. Japan is the largest user in thermal treatment of municipal solid waste in the world, with 40 million tons annually.
Some of the newest plants use stoker technology and others use the advanced oxygen enrichment technology. Several treatment plants exist worldwide using relatively novel processes such as direct smelting, the Ebara fluidization process and the Thermoselect JFE gasification and melting technology process. [ 20 ]
As of June 2014, Indonesia had a total of 93.5 MW installed capacity of waste-to-energy, with a pipeline of projects in different preparation phases together amounting to another 373MW of capacity. [ 21 ]
Biofuel Energy Corporation of Denver, Colorado, opened two new biofuel plants in Wood River, Nebraska , and Fairmont, Minnesota , in July 2008. These plants use distillation to make ethanol for use in motor vehicles and other engines. Both plants are currently reported to be working at over 90% capacity. [ citation needed ]
Fulcrum BioEnergy, which started in 2007 in Pleasanton, California , built a WtE plant near Reno, NV to convert waste to sustainable aviation fuel (SAF). [ 22 ] The plant was in commissioning from 2022 to May 2024 under the name Sierra BioFuels. Fulcrum predicted that the plant would produce approximately 10.5 million gallons per year of Fischer-Tropsch products from nearly 200,000 tons per year of MSW. [ 23 ] The total exported product amounted to just 350 gallons of syncrude which were transported to Marathon Petroleum 's refinery for conversion into jet fuel . [ 22 ] [ 24 ] The plant had issues including damage from unexpected generation of nitric acid and deposits of a concrete-like substance up to 10 feet thick in its gasification system. [ 24 ] In 2024 Fulcrum BioEnergy ceased operations at the plant after defaulting on $290 million bonds issued through the Nevada Department of Business and Industry used to fund the plant's construction. [ 22 ] [ 25 ]
Waste-to-energy technology includes fermentation , which can take biomass and create ethanol , using waste cellulosic or organic material. [ 19 ] In the fermentation process, the sugar in the waste is converted to carbon dioxide and alcohol, in the same general process that is used to make wine. Normally fermentation occurs with no air present.
Esterification can also be done using waste-to-energy technologies, and the result of this process is biodiesel . The cost-effectiveness of esterification will depend on the feedstock being used, and all the other relevant factors such as transportation distance, amount of oil present in the feedstock, and others. [ 26 ] Gasification and pyrolysis by now can reach gross thermal conversion efficiencies (fuel to gas) up to 75%, however, a complete combustion is superior in terms of fuel conversion efficiency. [ 7 ] Some pyrolysis processes need an outside heat source which may be supplied by the gasification process, making the combined process self-sustaining.
In thermal WtE technologies, nearly all of the carbon content in the waste is emitted as carbon dioxide (CO 2 ) to the atmosphere (when including final combustion of the products from pyrolysis and gasification; except when producing biochar for fertilizer). Municipal solid waste (MSW) contain approximately the same mass fraction of carbon as CO 2 itself (27%), so treatment of 1 metric ton (1.1 short tons) of MSW produce approximately 1 metric ton (1.1 short tons) of CO 2 .
In the event that the waste was landfilled , 1 metric ton (1.1 short tons) of MSW would produce approximately 62 cubic metres (2,200 cu ft) methane via the anaerobic decomposition of the biodegradable part of the waste. This amount of methane has more than twice the global warming potential than the 1 metric ton (1.1 short tons) of CO 2 , which would have been produced by combustion. In some countries, large amounts of landfill gas are collected. However, there is still the global warming potential of the landfill gas being emitted to atmosphere. For example, in the US in 1999 landfill gas emission was approximately 32% higher than the amount of CO 2 that would have been emitted by combustion. [ 27 ]
In addition, nearly all biodegradable waste is biomass . That is, it has biological origin. This material has been formed by plants using atmospheric CO 2 typically within the last growing season. If these plants are regrown the CO 2 emitted from their combustion will be taken out from the atmosphere once more.
Such considerations are the main reason why several countries administrate WtE of the biomass part of waste as renewable energy . [ 28 ] The rest—mainly plastics and other oil and gas derived products—is generally treated as non-renewables .
The CO 2 emissions from plastic waste-to-energy systems are higher than those from current fossil fuel-based power systems per unit of power generated, even after considering the contribution of carbon capture and storage . Power generation using plastic waste will significantly increase by 2050. Carbon must be separated during energy recovery processes. Otherwise, the fight against global warming would fail due to plastic waste. [ 29 ]
MSW to a large extent is of biological origin (biogenic), e.g. paper, cardboard, wood, cloth, food scraps. Typically half of the energy content in MSW is from biogenic material. [ 30 ] Consequently, this energy is often recognised as renewable energy according to the waste input. [ 31 ]
Several methods have been developed by the European CEN 343 working group to determine the biomass fraction of waste fuels, such as Refuse Derived Fuel /Solid Recovered Fuel. The initial two methods developed (CEN/TS 15440) were the manual sorting method and the selective dissolution method . A detailed systematic comparison of these two methods was published in 2010. [ 32 ] Since each method suffered from limitations in properly characterizing the biomass fraction, two alternative methods have been developed.
The first method uses the principles of radiocarbon dating . A technical review (CEN/TR 15591:2007) outlining the carbon 14 method was published in 2007. A technical standard of the carbon dating method (CEN/TS 15747:2008) was published in 2008. In the United States, there is already an equivalent carbon 14 method under the standard method ASTM D6866.
The second method (so-called balance method ) employs existing data on materials composition and operating conditions of the WtE plant and calculates the most probable result based on a mathematical-statistical model. [ 33 ] Currently the balance method is installed at three Austrian and eight Danish incinerators.
A comparison between both methods carried out at three full-scale incinerators in Switzerland showed that both methods came to the same results. [ 34 ]
Carbon 14 dating can determine with precision the biomass fraction of waste, and also determine the biomass calorific value . Determining the calorific value is important for green certificate programs such as the Renewable Obligation Certificate program in the United Kingdom. These programs award certificates based on the energy produced from biomass. Several research papers, including the one commissioned by the Renewable Energy Association in the UK, have been published that demonstrate how the carbon 14 result can be used to calculate the biomass calorific value. The UK gas and electricity markets authority, Ofgem , released a statement in 2011 accepting the use of Carbon 14 as a way to determine the biomass energy content of waste feedstock under their administration of the Renewables Obligation. [ 35 ] Their Fuel Measurement and Sampling (FMS) questionnaire describes the information they look for when considering such proposals. [ 36 ]
A 2019 report commissioned by the Global Alliance for Incinerator Alternatives (GAIA), done by the Tishman Environment and Design Center at The New School , found that 79% of the then 73 operating waste-to-energy facilities in the U.S. are located in low-income communities and/or "communities of color", because "of historic residential, racial segregation and expulsive zoning laws that allowed whiter, wealthier communities to exclude industrial uses and people of color from their boundaries." [ 37 ] In Chester, Pennsylvania , where a community group is actively opposing their local waste-to-energy facility, Sintana Vergara, an assistant professor in the Department of Environmental Resources Engineering at Humboldt State University in California, commented that community resistance is based on both the pollution and the fact that many of these facilities have been sited in communities without any community input, and without any benefits to the community. [ 38 ]
In other countries WtE facilities are located adjacent to residental housing without significant conflicts, also in high-income areas. One prominent example is Amager Bakke in central Copenhagen, Denmark
According to a 2019 United Nations Environment Programme report, there are 589 WtE plants in Europe and 82 in the United States. [ 39 ]
The following are some examples of WtE plants.
No industrial liquid fuel producing gasification plants are currently operational, but two are under erection/commissioning in Varennes (CA) and Swindon (UK).
The US Air Force once tested a Transportable Plasma Waste to Energy System (TPWES) facility (PyroGenesis technology) at Hurlburt Field, Florida. [ 42 ] The plant, which cost $7.4 million to construct, [ 43 ] was closed and sold at a government liquidation auction in May 2013, less than three years after its commissioning. [ 44 ] [ 45 ] The opening bid was $25. The winning bid was sealed.
Besides large plants, domestic waste-to-energy incinerators also exist. For example, the Refuge de Sarenne has a domestic waste-to-energy plant. It is made by combining a wood-fired gasification boiler with a Stirling motor . [ 46 ] [ 47 ]
Renergi will scale up their system of converting waste organic materials into liquid fuels using a thermal treatment process in Collie, Western Australia. The system will process 1.5 tonnes of organic matter per hour. Annually the facility will divert 4000 tonnes of municipal waste from landfill and source an additional 8000 tonnes of organic waste from agricultural and forestry operations. Renergi’s patented “grinding pyrolysis” process aims to converts organic materials into biochar, bio-gases and bio-oil by applying heat in an environment with limited oxygen. [ 48 ]
Another project in the Rockingham Industrial Zone, roughly 45 kilometres south of Perth will see a 29 MW plant built with capacity to power 40,000 homes from an annual feedstock of 300,000 tonnes of municipal, industrial and commercial rubbish. As well as supplying electricity to the South West Interconnected System, 25 MW of the plant’s output has already been committed under a power purchase agreement. [ 49 ]
The Reppie waste to energy plant in Ethiopia was the first such plant in Africa. The plant became operational in 2018. [ 50 ]
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The Waste Incineration Directive , more formally Directive 2000/76/EC of the European Parliament and of the Council
of 4 December 2000 on the incineration of waste (OJ L332, P91 – 111), was a Directive issued by the European Union and relates to standards and methodologies required by Europe for the practice and technology of incineration . The aim of this Directive is to minimise the impact of negative environmental effects on the environment and human health resulting from emissions to air, soil, surface and ground water from the incineration and co-incineration of waste. The requirements of the Directive were developed to reflect the ability of modern incineration plants to achieve high standards of emission control more effectively. [ 1 ] The Directive has been replaced by the Industrial Emissions Directive since 7 January 2014. [ 2 ]
This waste -related article is a stub . You can help Wikipedia by expanding it .
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Waste heat is heat that is produced by a machine , or other process that uses energy , as a byproduct of doing work . All such processes give off some waste heat as a fundamental result of the laws of thermodynamics . Waste heat has lower utility (or in thermodynamics lexicon a lower exergy or higher entropy ) than the original energy source. Sources of waste heat include all manner of human activities, natural systems, and all organisms, for example, incandescent light bulbs get hot, a refrigerator warms the room air, a building gets hot during peak hours, an internal combustion engine generates high-temperature exhaust gases, and electronic components get warm when in operation.
Instead of being "wasted" by release into the ambient environment, sometimes waste heat (or cold) can be used by another process (such as using hot engine coolant to heat a vehicle), or a portion of heat that would otherwise be wasted can be reused in the same process if make-up heat is added to the system (as with heat recovery ventilation in a building).
Thermal energy storage , which includes technologies both for short- and long-term retention of heat or cold, can create or improve the utility of waste heat (or cold). One example is waste heat from air conditioning machinery stored in a buffer tank to aid in night time heating. Another is seasonal thermal energy storage (STES) at a foundry in Sweden. The heat is stored in the bedrock surrounding a cluster of heat exchanger equipped boreholes, and is used for space heating in an adjacent factory as needed, even months later. [ 1 ] An example of using STES to use natural waste heat is the Drake Landing Solar Community in Alberta , Canada, which, by using a cluster of boreholes in bedrock for interseasonal heat storage, obtains 97 percent of its year-round heat from solar thermal collectors on the garage roofs. [ 2 ] [ 3 ] Another STES application is storing winter cold underground, for summer air conditioning. [ 4 ]
On a biological scale, all organisms reject waste heat as part of their metabolic processes , and will die if the ambient temperature is too high to allow this.
Anthropogenic waste heat can contribute to the urban heat island effect. [ 5 ] The biggest point sources of waste heat originate from machines (such as electrical generators or industrial processes, such as steel or glass production) and heat loss through building envelopes. The burning of transport fuels is a major contribution to waste heat.
Machines converting energy contained in fuels to mechanical work or electric energy produce heat as a by-product.
In the majority of applications, energy is required in multiple forms. These energy forms typically include some combination of heating, ventilation, and air conditioning , mechanical energy and electric power . Often, these additional forms of energy are produced by a heat engine running on a source of high-temperature heat. A heat engine can never have perfect efficiency, according to the second law of thermodynamics , therefore a heat engine will always produce a surplus of low-temperature heat. This is commonly referred to as waste heat or "secondary heat", or "low-grade heat". This heat is useful for the majority of heating applications, however, it is sometimes not practical to transport heat energy over long distances, unlike electricity or fuel energy. The largest proportions of total waste heat are from power stations and vehicle engines. [ citation needed ] The largest single sources are power stations and industrial plants such as oil refineries and steelmaking plants. [ citation needed ]
Conventional air conditioning systems are a source of waste heat by releasing waste heat into the outdoor ambient air whilst cooling indoor spaces. This expelling of waste heat from air conditioning can worsen the urban heat island effect. [ 5 ] Waste heat from air conditioning can be reduced through the use of passive cooling building design and zero-energy methods like evaporative cooling and passive daytime radiative cooling , the latter of which sends waste heat directly to outer space through the infrared window . [ 6 ] [ 7 ]
The electrical efficiency of thermal power plants is defined as the ratio between the input and output energy. It is typically only 33% when disregarding usefulness of the heat output for building heat. [ 8 ] The images show cooling towers , which allow power stations to maintain the low side of the temperature difference essential for conversion of heat differences to other forms of energy. Discarded or "waste" heat that is lost to the environment may instead be used to advantage.
Industrial processes, such as oil refining , steel making or glass making are major sources of waste heat. [ 9 ]
Although small in terms of power, the disposal of waste heat from microchips and other electronic components, represents a significant engineering challenge. This necessitates the use of fans, heatsinks , etc. to dispose of the heat.
For example, data centers use electronic components that consume electricity for computing, storage and networking. The French CNRS explains a data center is like a resistor and most of the energy it consumes is transformed into heat and requires cooling systems. [ 10 ]
Humans, like all animals, produce heat as a result of metabolism . In warm conditions, this heat exceeds a level required for homeostasis in warm-blooded animals, and is disposed of by various thermoregulation methods such as sweating and panting . [ 11 ]
Low temperature heat contains very little capacity to do work ( Exergy ), so the heat is qualified as waste heat and rejected to the environment. Economically most convenient is the rejection of such heat to water from a sea , lake or river . If sufficient cooling water is not available, the plant can be equipped with a cooling tower or air cooler to reject the waste heat into the atmosphere. In some cases it is possible to use waste heat, for instance in district heating systems.
There are many different approaches to transfer thermal energy to electricity, and the technologies to do so have existed for several decades.
An established approach is by using a thermoelectric device, [ 12 ] where a change in temperature across a semiconductor material creates a voltage through a phenomenon known as the Seebeck effect .
A related approach is the use of thermogalvanic cells , where a temperature difference gives rise to an electric current in an electrochemical cell. [ 13 ]
The organic Rankine cycle , offered by companies such as Ormat , is a very known approach, whereby an organic substance is used as working fluid instead of water. The benefit is that this process can reject heat at lower temperatures for the production of electricity than the regular water steam cycle. [ 14 ] An example of use of the steam Rankine cycle is the Cyclone Waste Heat Engine .
Waste of the by-product heat is reduced if a cogeneration system is used, also known as a Combined Heat and Power (CHP) system. Limitations to the use of by-product heat arise primarily from the engineering cost/efficiency challenges in effectively exploiting small temperature differences to generate other forms of energy. Applications utilizing waste heat include swimming pool heating and paper mills . In some cases, cooling can also be produced by the use of absorption refrigerators for example, in this case it is called trigeneration or CCHP (combined cooling, heat and power).
Waste heat can be used in district heating . Depending on the temperature of the waste heat and the district heating system, a heat pump must be used to reach sufficient temperatures. These are an easy and cheap way to use waste heat in cold district heating systems, as these are operated at ambient temperatures and therefore even low-grade waste heat can be used without needing a heat pump at the producer side. [ 15 ]
Waste heat can be forced to heat incoming fluids and objects before being highly heated. For instance, outgoing water can give its waste heat to incoming water in a heat exchanger before heating in homes or power plants .
Anthropogenic heat is heat generated by humans and human activity. The American Meteorological Society defines it as "Heat released to the atmosphere as a result of human activities, often involving combustion of fuels. Sources include industrial plants, space heating and cooling, human metabolism, and vehicle exhausts. In cities this source typically contributes 15–50 W/m 2 to the local heat balance, and several hundred W/m 2 in the center of large cities in cold climates and industrial areas." [ 16 ] In 2020, the overall anthropogenic annual energy release was 168,000 terawatt-hours; given the 5.1×10 14 m 2 surface area of Earth, this amounts to a global average anthropogenic heat release rate of 0.04 W/m 2 . [ 17 ] [ 18 ]
Anthropogenic heat is a small influence on rural temperatures, and becomes more significant in dense urban areas. [ 19 ] It is one contributor to urban heat islands . Other human-caused effects (such as changes to albedo , or loss of evaporative cooling) that might contribute to urban heat islands are not considered to be anthropogenic heat by this definition.
Anthropogenic heat is a much smaller contributor to global warming than greenhouse gases are. [ 20 ] In 2005, anthropogenic waste heat flux globally accounted for only 1% of the energy flux created by anthropogenic greenhouse gases. The heat flux is not evenly distributed, with some regions higher than others, and significantly higher in certain urban areas. For example, global forcing from waste heat in 2005 was 0.028 W/m 2 , but was +0.39 and +0.68 W/m 2 for the continental United States and western Europe, respectively. [ 21 ]
Although waste heat has been shown to have influence on regional climates, [ 22 ] climate forcing from waste heat is not normally calculated in state-of-the-art global climate simulations. Equilibrium climate experiments show statistically significant continental-scale surface warming (0.4–0.9 °C) produced by one 2100 AHF scenario, but not by current or 2040 estimates. [ 21 ] Simple global-scale estimates with different growth rates of anthropogenic heat [ 23 ] that have been actualized recently [ 24 ] show noticeable contributions to global warming, in the following centuries. For example, a 2% p.a. growth rate of waste heat resulted in a 3 degree increase as a lower limit for the year 2300. Meanwhile, this has been confirmed by more refined model calculations. [ 25 ]
A 2008 scientific paper showed that if anthropogenic heat emissions continue to rise at the current rate, they will become a source of warming as strong as GHG emissions in the 21st century. [ 26 ]
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A waste heat recovery unit ( WHRU ) is an energy recovery heat exchanger that transfers heat from process outputs at high temperature to another part of the process for some purpose, usually increased efficiency. The WHRU is a tool involved in cogeneration . Waste heat may be extracted from sources such as hot flue gases from a diesel generator, steam from cooling towers , or even waste water from cooling processes such as in steel cooling .
Waste heat found in the exhaust gas of various processes or even from the exhaust stream of a conditioning unit can be used to preheat the incoming gas. This is one of the basic methods for recovery of waste heat. Many steel making plants use this process as an economic method to increase the production of the plant with lower fuel demand. There are many different commercial recovery units for the transferring of energy from hot medium space to lower one: [ 1 ]
A waste heat recovery boiler (WHRB) is different from a heat recovery steam generator ( HRSG ) in the sense that the heated medium does not change phase.
According to a report done by Energetics Incorporated for the DOE in November 2004 titled Technology Roadmap [ 2 ] and several others done by the European Commission , the majority of energy production from conventional and renewable resources are lost to the atmosphere due to onsite (equipment inefficiency and losses due to waste heat) and offsite (cable and transformers losses) losses, that sums to be around 66% loss in electricity value. [ 3 ] Waste heat of different degrees could be found in final products of a certain process or as a by-product in industry such as the slag in steelmaking plants. Units or devices that could recover the waste heat and transform it into electricity are called WHRUs or heat to power units :
The recovery process will add to the efficiency of the process and thus decrease the costs of fuel and energy consumption needed for that process. [ 5 ]
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Waste oil is defined as any petroleum -based or synthetic oil that, through contamination, has become unsuitable for its original purpose due to the presence of impurities or loss of original properties. [ 1 ]
The U.S. EPA defines the term "used oil" as any petroleum or synthetic oil that has been used, and as a result of such use is contaminated by physical or chemical properties. [ 2 ] "Used oil" is a precise regulatory term. "Waste oil" is a more generic term for oil that has been contaminated with substances that may or may not be hazardous. [ 1 ] Any oil contaminated with hazardous waste may itself be a hazardous waste, and if so, must be managed subject to hazardous waste management standards. Both used oil and waste oil require proper recycling or disposal to avoid creating an environmental problem.
Some examples of types of products that after use, can be labeled as used oil are: hydraulic oil , transmission oil, brake fluids, motor oil , crankcase oil, gear box oil, synthetic oil , [ 3 ] and grades 1, 2, 3 and 4 fuel oil . [ 4 ]
Waste oil can be disposed of in different ways, including sending the used oil off-site (some facilities are permitted to handle the used oil such as local garages and local waste disposal facilities), burning used oil as a fuel (some used oil is not regulated by burner standards, but others that are off-specification used oil can only be burned in either industrial furnaces, certain boilers, and permitted hazardous waste incinerators), and marketing the used oil (claims are made that the used oil is to be burned for energy recovery, and then it is shipped to a used oil burner who burns the used oil in an approved industrial furnace or boiler).
Oils that are off-specification typically contain: Arsenic 5 ppm, Cadmium 2 ppm, Chromium 10 ppm, Lead 100 ppm, Flash point 100 °F, minimum (i.e., FP must be greater than 100 °F), Total Halogens >4,000 ppm [ 5 ]
For on-site burning of used oil, the oil must be stored in tanks or containers, above or underground. The containers must be in good condition with no leaks, the tanks/containers must be labeled with the words “used oil”, and there must be a spill prevention plan (or a control and countermeasures plan).
In 1984 the Florida Department of Environmental Protection (DEP) implemented a used oil management program under Sections 403.75 through 403.769, Florida Statutes. Florida’s Used Oil Recycling Program has grown to become one of the most successful in the United States and has received national recognition.
Waste oil furnace is a type of furnace used for heating purposes and is fueled by used oil that is free of hazardous contaminants, as described by the EPA . Waste-oil-fueled boilers can be used for various industrial purposes as well as heating.
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A waste pond or chemical pond is a small impounded water body used for the disposal of water pollutants , and sometimes utilized as a method of recycling or decomposing toxic substances. Such waste ponds may be used for regular disposal of pollutant materials or may be used as upset receivers for special pollution events. [ 1 ] [ full citation needed ] Often, chemical ponds themselves are addressed for cleanup action after their useful life is over or when a risk of groundwater contamination arises. [ 2 ] [ full citation needed ] Contamination of waterways and groundwater can be damaging to human, animal and environmental health. These health effects bring into question the best engineering solutions to mitigate waste ponds' environmental impact.
The bacteria , pathogens , and excess nutrients stored in waste ponds can damage the environment and harm human health. In storms and heavy rainfall, waste ponds can overflow spilling sewage water and contaminating waterways . [ 3 ] The contamination of surrounding watersheds causes negative impacts to both the ecosystems and surrounding populations. A survey carried out in Eastern North Carolina found that there was a twenty-one percent increase in cases of acute gastrointestinal illness in rural areas surrounding hog farms which stored waste in waste ponds compared to areas without. The results also showed a stronger association following periods of heavy rain. [ 4 ] This suggests that the waste ponds, particularly during heavy rainfall, may play a significant role in the contamination of surrounding environments, warranting further investigation into their impact on public health in rural areas. Overall, these findings highlight the potential risks associated with waste ponds, creating a potential for innovation to improve management practices and continue research to mitigate their environmental and public health effects.
Peak usage of waste ponds in the United States occurred in the period 1955 to 1985, after which the environmental risks of pond technology were sufficiently understood, [ 5 ] such that alternative technologies [ clarification needed ] for waste disposal gradually began to displace many of the waste ponds. Waste ponds often have pond liners, such as concrete or robust synthetic polymeric materials, to prevent infiltration of chemicals to soil or groundwater.
Designing and managing waste ponds in an environmentally responsible way requires a comprehensive approach that integrates site selection, chemical balancing, and the establishment of long-term sustainability practices. By employing effective chemical treatments, and monitoring systems, it is possible to significantly reduce the environmental impact of waste ponds. [ 6 ] Additionally, using strategies such as waste minimization, pond closure, and the use of containment systems ensure that these ponds can serve as a safe and effective solution for waste management without putting the health of surrounding ecosystems at risk. [ 7 ]
Union Carbide used the pond at its Piscataway, New Jersey plant while in operation. The pond's primary use was chemical drainage. Hazardous chemicals would flow through drains inside the plant and into the pond. They were later pumped back to the factory via two large pumps, distilled to remove acetone and other hazards. Overall, this process was harmful to the environment and polluted the groundwater. [ 8 ] [ better source needed ]
The United States Oak Ridge National Laboratory in Oak Ridge, Tennessee operated for more than 50 years, and was decommissioned in the mid 1960s. Plant waste, collected in a pond, was found to contain radioactive waste, including strontium-90 , caesium-137 ; tritium , and transuranics . [ citation needed ]
In the mid 1990s, Department of Energy officials installed a cryogenic stabilization system at the waste pond, freezing the soil and groundwater, forming a barrier to groundwater leaching. In February 2004, the cryogenic system was dismantled, and the pond was excavated. The soil surrounding the frozen pond contained lower levels of contamination than the pond itself, but enough contamination that it had to be removed. [ 9 ] This demonstrates the lasting environmental impact of waste disposal in waste ponds. [ citation needed ]
While there are many wastewater treatment options available, some are more accessible or effective in different parts of the world. In Kenya , waste stabilization ponds are one of the most effective wastewater treatment methods, and one of the few that work in Kenya, specifically. [ 10 ]
Across Europe , waste ponds are a common method of wastewater treatment. In France there are an estimated 2,500 waste ponds. [ 11 ] There are approximately 1,500 in Bavaria and approximately 3,000 in Germany , overall. [ 12 ] The United Kingdom has only recorded the existence of 40 waste ponds, but this may be due to the limited research has been done on the UK's waste ponds. [ citation needed ]
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Waste stabilization ponds ( WSPs or stabilization ponds or waste stabilization lagoons ) are ponds designed and built for wastewater treatment to reduce the organic content and remove pathogens from wastewater . They are man-made depressions confined by earthen structures. Wastewater or "influent" enters on one side of the waste stabilization pond and exits on the other side as "effluent", after spending several days in the pond, during which treatment processes take place.
Waste stabilization ponds are used worldwide for wastewater treatment and are especially suitable for developing countries that have warm climates. [ 2 ] They are frequently used to treat sewage and industrial effluents , but may also be used for treatment of municipal run-off or stormwater . The system may consist of a single pond or several ponds in a series, each pond playing a different role in the removal of pollutants . After treatment, the effluent may be returned to surface water or reused as irrigation water (or reclaimed water ) if the effluent meets the required effluent standards (e.g. sufficiently low levels of pathogens ).
Waste stabilization ponds involve natural treatment processes which take time because removal rates are slow. Therefore, larger areas are required than for other treatment processes with external energy inputs. Waste stabilization ponds described here use no aerators. High-performance lagoon technology that does use aerators has much more in common with the activated sludge process. Such aerated lagoons use less area than is needed for traditional stabilization ponds and are also common in small towns. [ 3 ]
Sewage and many types of industrial wastewaters contain organic matter. If wastewater is discharged untreated into surface water bodies (for instance, rivers and lakes), their organic matter serves as food for microorganisms living in the surface waters. These organisms use the organic matter for energy generation for their growth and reproduction. This is done via their respiration , in which they convert the organic matter into carbon dioxide and water. These stable components do not cause water pollution problems. Therefore this is frequently called "stabilization" of the organic matter. [ citation needed ]
However, these organisms use oxygen in their respiration, thus reducing the oxygen concentration in the surface waters. This is one of the main water pollution problems, which may affect the surface water biota , including fish. [ 4 ] [ 5 ]
Waste stabilization ponds reproduce these biological phenomena before they take place in the receiving surface water and cause the pollution problems due to oxygen consumption. The ponds receive wastewater, and, by natural processes similar to those that take place in the surface waters, carry out stabilization of the organic matter inside them, as part of the treatment. This is why they received the name of waste stabilization ponds. [ 6 ]
The reactions take place by the joint participation of several microorganisms living within the pond. The organic matter is measured as biochemical oxygen demand (BOD). BOD values in the pond effluent are lower than in the influent, reflecting the removal of organic matter. This pond biome uses organic matter from the wastewater as food. [ citation needed ]
Nutrients are converted to cell material and energy for life processes including reproduction and growth of living cells. Some of these living cells will be consumed by organisms at higher trophic levels within the pond. In ponds, the most important group of microorganisms are bacteria , which utilize most of the organic matter from the wastewater, but also consume oxygen. [ citation needed ]
Algae are another essential group of microorganisms. They do not depend on the organic material from the influent. Instead, they undertake photosynthesis , in which they produce the organic matter for their own consumption and, very importantly here, they release oxygen. The excess oxygen released supports the respiration done by the aerobic organisms in the pond. Atmospheric oxygen is also dissolved into the liquid, which assists in maintaining an aerobic layer on the top of the pond surface. [ citation needed ]
The oxygen concentration varies in the liquid column: Close to the surface, concentrations are high and support the growth of aerobic organisms. Close to the pond bottom, sunlight penetration is low, and thus photosynthetic activity is reduced. This causes oxygen concentrations to be low there. Finally, inside the sediments in the bottom layer, there is no oxygen at all. Here, organic matter is removed by digestion undertaken by anaerobic organisms . [ 6 ]
Pathogens can be efficiently removed in waste stabilization ponds. The process relies mostly on maturation ponds for removal of pathogens, although some removal also takes place in the other ponds of the system. The higher the number of ponds in the series, the more efficient the pathogen removal. [ citation needed ]
Removal of pathogenic bacteria and viruses occurs mainly by inactivation. Pathogens are inactivated as a result of a complex interaction of mechanisms that involve pH (the pH value in ponds is high because of algal photosynthesis), temperature, ultraviolet radiation present in the sunlight that reaches the pond surface and photooxidative reactions taking advantage of high dissolved oxygen concentrations. [ 7 ] [ 8 ]
Protozoan pathogens are present in the wastewater in the form of cysts or oocysts. Helminths (worms) are present in the form of eggs. The protozoan and helminth pathogens can be removed by the mechanism of sedimentation. [ 8 ] Very high removal efficiencies may be achieved, especially if maturation ponds are part of the treatment system. In that case, the final pond effluent may be in compliance with World Health Organization guidelines for irrigating with treated wastewaster (or " reclaimed water "). [ 9 ] However, sludge (sediment) from the ponds may be heavily contaminated with helminth eggs, which may survive even after several years of storing the sludge inside of the pond. [ 10 ]
Waste stabilization ponds consist of man-made basins comprising a single or several series of anaerobic, facultative or maturation ponds. [ 11 ] The presence or absence of oxygen varies with the three different types of ponds, used in sequence. Anaerobic waste stabilization ponds have very little dissolved oxygen, thus anaerobic conditions prevail. The second type of pond, facultative stabilization ponds, sustain an aerobic surface habitat above an anaerobic benthic habitat. [ 12 ] Maturation ponds offer aerobic conditions throughout, from the surface to the bottom.
The main configurations of pond systems are: [ 4 ] [ 13 ]
If an anaerobic pond is present, part of the suspended solids from the wastewater settles, thus removing the organic matter ( BOD ) contributed by these solids. Additionally, some of the dissolved organic matter is removed by anaerobic digestion . During the second stage in the facultative pond , most of the remaining BOD is removed mainly by the heterotrophic bacteria that receive oxygen from the photosynthesis undertaken by algae. The main function of the tertiary stage in maturation ponds is the removal of pathogens, although it may also assist in nutrient reduction (i.e. nitrogen ). [ 12 ] However, nitrogen fixation by algae living in stabilization pond systems may increase nitrogen levels in stabilization pond effluent. [ 6 ]
Anaerobic ponds receive raw wastewater . They have a smaller surface area compared to facultative ponds and are also deeper (usually 3.0 to 5.0 m). The depth decreases the influence of oxygen production by photosynthesis, leading to anaerobic conditions. Depending on loading and climatic conditions, these ponds are able to remove between half to two thirds of the influent BOD. This significantly decreases the load of organic matter that goes to the facultative ponds, and thus decreases their required size. [ 4 ] Anaerobic stabilization ponds have the disadvantage of potentially releasing malodorous gases. This especially includes hydrogen sulfide with an odor of rotten eggs, if the system has operational problems. [ 14 ]
The first pond biome in a series of stabilization ponds digests the putrescible solids suspended in the wastewater being treated. Anaerobic ponds allow solids to settle down at the bottom as sludge. This settling removes a portion of the particulate organic material. [ 14 ] A large fraction of the settled solids will accumulate close to the point where wastewater enters the pond. Therefore, anaerobic ponds must be designed to be far deeper than either aerobic or facultative ponds. The depth decreases the oxygen levels so anaerobic bacteria can efficiently digest the waste. [ 14 ] Anaerobic ponds contain anaerobic organisms which are able to break down complex organic waste into basic compounds that are less harmful to the environment. [ 15 ] Because anaerobic organisms can only thrive in warm temperatures, anaerobic ponds are not suitable in temperate or cold climates. [ citation needed ]
Sludge accumulates at the bottom of the anaerobic ponds and needs to be removed every few years. [ citation needed ]
Facultative stabilization ponds that receive raw wastewater are called primary facultative ponds. If they are receiving wastewater that has already been treated in anaerobic ponds, they are called secondary facultative ponds. Facultative stabilization ponds may also be used for treatment following other types of treatment processes such as upflow anaerobic sludge blanket (UASB) reactors, oxidation ditches or aerated lagoons . Compared with anaerobic ponds, facultative ponds are shallower (1.5 to 2.5 m deep) and have much larger surface areas. The surface area is important because it allows atmospheric oxygen to dissolve and sunlight radiation to penetrate the water. This allows for photosynthetic activity to occur which produces more oxygen. [ citation needed ]
In most ponds both bacteria and algae are needed in order to maximize the decomposition of organic matter and the removal of other pollutants. [ 15 ] Algae produce oxygen (photosynthesis) and also consume oxygen (respiration), but they leave an excess of oxygen that can then be used by aerobic bacteria for respiration and for the processes of oxidation (or stabilization) of the organic matter in the wastewater. [ citation needed ]
Several types of invertebrates are present in the ponds where they control the population of algae , which then settles to the bottom. [ 15 ] Heavy algal growth may block sunlight from penetrating into the pond. This decreases the potential for photosynthesis to contribute oxygen to the pond. [ citation needed ]
In the treatment of sewage, systems composed of anaerobic ponds followed by facultative ponds usually have overall BOD removal efficiencies between 75 and 85%. Higher efficiencies are difficult to achieve because the effluent contains high concentrations of particulate organic matter, in the form of algae, naturally produced during treatment. [ citation needed ]
The sludge comprising the sediment layer in the pond undergoes anaerobic digestion, and may accumulate for several years without needing removal. [ citation needed ]
Some additional removal of organic matter and other pollutants may be achieved in maturation ponds. These ponds are only included in the treatment line when high efficiencies of pathogen removal are required, either for discharge of the treated effluent in surface water bodies, or for use for irrigation or aquaculture . They are usually used after facultative ponds, but may also follow other treatment processes, such as upflow anaerobic sludge blanket (UASB) reactors. [ 16 ] They could also be placed after an activated sludge process.
Maturation ponds must be shallow (around 1.0 m depth or less) with a great surface area so that more oxygen can dissolve into the water giving the bacteria enough oxygen to properly function. [ 14 ] Shallow ponds benefit from high photosynthetic activity arising from the penetration of solar radiation. The pH values are high because of intense photosynthesis, and ultraviolet radiation penetration takes place in the upper layers. Both of these factors promote the removal of pathogenic bacteria and viruses. Given the high surface area of the maturation ponds, protozoan cysts and helminth eggs are also removed, with sedimentation as the main mechanism. [ 8 ] [ 6 ]
Sludge accumulation is very low in maturation ponds. [ citation needed ]
Very high pathogen removal efficiencies may be achieved, depending on several factors: temperature, hydraulic retention time (the amount of time the liquid remains in the system - from entrance to exit), the number of ponds in the series, the presence of baffles and the depth of ponds. [ 8 ]
Maturation ponds may be used in combination with a rainwater reservoir to form an ecological, self-purifying irrigation reservoir. [ 17 ] [ 18 ]
Waste stabilization ponds are very efficient in their primary objective of removing organic matter and, under some conditions, pathogenic organisms. Their design criteria have changed very little over the years. [ 15 ] Ponds are simple to design, build, operate and maintain, which is very important in remote areas and in developing countries where sophisticated equipment and highly skilled labor is not easily available. Construction may be done by local contractors in small towns. [ citation needed ]
Waste stabilization ponds work well in nearly all environments and can treat most types of wastewater . [ 6 ] They are particularly well-suited for tropical and subtropical countries because the intensity of the sunlight and temperature are key factors for the efficiency of the removal processes. [ 6 ] Ponds are used throughout the world. In many countries and regions ponds are the most widely used treatment process. For this reason, they are one of the processes recommended by WHO for the treatment of wastewater for reuse in agriculture and aquaculture, especially because of their effectiveness in removing nematodes (worms) and helminth eggs. [ 9 ]
Ponds cannot achieve very high efficiencies in the removal of organic matter, and usually have low capacities for removing nitrogen and phosphorus . The effluent usually has high concentrations of suspended solids , resulting from algal production in the ponds. Therefore, ponds are not a suitable technology in areas where stringent discharge standards exist, unless additional stages of post treatment are included. [ 19 ] [ 14 ]
Since ponds require large areas, they may not be practical in proximity to towns where land is expensive. A suitable topography and a suitable soil structure are also desired, in order to reduce construction costs. [ citation needed ]
Regarding operation and maintenance, the tasks performed by the operational staff are very simple and do not require special skills. Additionally, there is no energy consumption for aeration, no need of heavy equipment maintenance and no frequent sludge removal, sludge treatment and disposal. [ citation needed ]
Ponds require very little maintenance, since there is no heavy electric or mechanical equipment that requires attention. The only routine maintenance needed is on the preliminary treatment (cleaning of screens and removal of sand), routine checking of pipes, weirs and other hydraulic structures, and removal of unwanted vegetation growth in embankments. [ 6 ] [ 4 ]
Sludge accumulates inside the ponds. It needs to be removed only in the interval of several years. This is an important advantage of the system. However, when removal is necessary, it is usually an expensive and labor-intensive operation. Removal is more frequent in anaerobic ponds (every few years), because of their smaller volume and lower capacity to store the sludge, compared with facultative ponds. In facultative ponds, sludge removal may be necessary only in intervals around 15 to 25 years. In maturation ponds, sludge accumulation is very low. [ 6 ]
Sludge removal, also called desludging, may be done in two basic ways: (i) interrupting the operation of the pond for desludging or (ii) keeping the pond in operation while desludging. [ 6 ] In the first case, the influent wastewater to the pond to be desludged is closed. Afterwards, the pond is drained and the bottom sludge is left for open drying for several weeks. During this period, the wastewater to be treated needs to be diverted to other ponds in the system. After the sludge has dried, its removal may be done manually (very laborious in large ponds) or mechanically using tractors or mechanical scrapers. In the second alternative, when the pond is left in operation during desludging, the removed sludge will be wet and will require further drying. This is undertaken outside the pond. Sludge removal can be by suction and pumping using vacuum trucks (only for small ponds), dredging, pumping from a raft or involving other mechanical equipment. In either case, the amount of sludge to be removed is very high, considering its accumulation over a period of years. This process is very laborious, expensive and requires careful planning. [ 6 ]
In the selection of a wastewater treatment process, besides the technical aspects that are relevant to each alternative, also cost factors play a very important role. The latter can be basically divided into (i) construction costs and (ii) operation and maintenance costs. Waste stabilization ponds are usually considered a cheap alternative in terms of construction costs. However, the final costs will depend essentially on the size of ponds, presence of maturation ponds in the process configuration, topography, soil conditions, groundwater level and land cost. [ 6 ]
Because all these elements are site-specific, it is difficult to generalize overall construction costs. In most cases these will be lower compared with other wastewater treatment alternatives. [ 20 ] [ 4 ] Depending on the specific situation of the area, construction costs can increase and level up with other technologies. [ citation needed ]
Waste stabilization ponds are one of the cheapest wastewater treatment processes in terms of operation and maintenance. [ 6 ]
The following types of water and wastewater infrastructure may superficially resemble waste stabilization ponds, but are not the same: [ citation needed ]
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Wastebasket taxon (also called a wastebin taxon , [ 1 ] dustbin taxon [ 2 ] or catch-all taxon [ 3 ] ) is a term used by some taxonomists to refer to a taxon that has the purpose of classifying organisms that do not fit anywhere else. They are typically defined by either their designated members' often superficial similarity to each other, or their lack of one or more distinct character states or by their not belonging to one or more other taxa. Wastebasket taxa are by definition either paraphyletic or polyphyletic , and are therefore not considered valid taxa under strict cladistic rules of taxonomy. The name of a wastebasket taxon may in some cases be retained as the designation of an evolutionary grade , however.
There are many examples of paraphyletic groups, but true "wastebasket" taxa are those that are known not to, and perhaps not intended to, represent natural groups, but are nevertheless used as convenient groups of organisms. The acritarchs are perhaps the most famous example. Wastebasket taxa are often old (and perhaps not described with the systematic rigour and precision that is possible in the light of accumulated knowledge of diversity) and populous. [ 4 ]
Fossil groups that are poorly known due to fragmentary remains are sometimes grouped together on gross morphology or stratigraphy , only later to be found to be wastebasket taxa, such as the crocodile-like Triassic group Rauisuchia . [ 11 ]
One of the roles of taxonomists is to identify wastebasket taxa and reclassify the content into more natural units. Sometimes, during taxonomic revisions, a wastebasket taxon can be salvaged after doing thorough research on its members, and then imposing tighter restrictions on what continues to be included. Such techniques "saved" Carnosauria and Megalosaurus . Other times, the taxonomic name contains too much unrelated "baggage" to be successfully salvaged. As such, it is usually dumped in favour of a new, more restrictive name (for example, Rhynchocephalia ), or abandoned altogether (for example, Simia ). [ citation needed ]
A related concept is that of form taxon , "wastebasket" groupings that are united by gross morphology. This is often result of a common mode of life, often one that is generalist , leading to generally similar body shapes by convergent evolution . [ citation needed ]
The term wastebasket taxon is sometimes employed in a derogatory fashion to refer to an evolutionary grade taxon. [ citation needed ]
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Wastewater discharge standards protect water sources from pollution and mismanagement. Each country in Latin America has its own set of standards, and these vary according to types of water use, agricultural, industrial or recreational use. Water quality is maintained by controlling the physicochemical and bacteriological parameters . The majority of water laws include fines for noncompliance. In many cases fines are inadequate and do not stop offending. In other cases the standards are lax and monitoring is sub-par.
This article summarizes the majority of wastewater discharge standards in Latin America, complemented with a country ranking considering the quantity and severity of their regulations. Also, a comparative analysis of relevant standards is made, and a real case description for each country when the regulation was not accomplished.
In Chile, the Ministry of Publics Works developed the standard, the decrete number 609, [ 1 ] approved on May 7, 1998. This norm was created with the aim to control the effluents discharged into the sewer system . This norm establishes the maximum discharge concentration in sewer systems and also the different parameters that will be monitored, depending on the economic activity developed by each industry. It also establishes the methods that must be used for taking samples of each parameter.
The control of the norm is responsibility of the company that provides the service of recollection of wastewater, being the regulator of sanitary services companies the main responsible. If a company produces disruption in the service, in terms of quality or quantity of the recollection, the companies of recollection of wastewater could suspend the service to that company.
Case description
In May 2009 Aguas Andinas, controlled by the Spanish Enterprise Agbar , will pay a fine because of a lawsuit presented against it by a group of neighbors because of the foul smells coming from the "La Farfana", a waste water treatment plant . This is one of the waste water recycling plants of Aguas Andinas. The bad odors caused digestive and psychological problems. The organization announced that it will appeal this judgement, based on the argument that it was due to a couple of precise episodes beyond its control that did not cause any environmental or personal harm. [ 2 ]
In June 2007, the Sanitary Services Superintendent's Office (SISS) started a lawsuit against the paper company Licancel after "not complying with the 90 Supreme Decrete, that regulates waste water disposal".
As the Superintendent's Office said, this decision is based on the investigation been forwarded that confirmed that this organization discharged its waste water without complying with the norm. As legislation establishes this office can propose and apply the corresponding sanctions , such as fines between one and a thousand Annual Tributary Units (UTA). This means around 392 Million Pesos . [ 3 ]
The norm for discharge is under the Law 1333, approved on April 27, 1992. This law is the general law of environment, and for the specific case was created a regulation for water pollution . [ 4 ]
This regulation is applied to every entity that produces contamination in the water. In the case of the discharge over sewer systems the regulation is under Chapter IV. It is stated that every company must agree with the company that provides the service of recollection of wastewater and the limits of discharge. The limits presented in this article, are those for new companies and for companies in process of identification of the type of body water that the company will discharge.
Case description
In August 2003, all the mining producers working in the city of Potosí must discharge their waste waters to a specific dike; otherwise they will be obliged to stop their operations. This statement, made by the director of Environment and Sustainable development, Limbert Paredes, who pointed out that this agreement was taken between the Mining Engineers Association of Potosí, law representatives and authorities of Potosí County.
These companies installed in the upper side of the city must build a pipeline to discharge their waste water by the end of June 2003, which was not done. Because of this, a new meeting was held and a new deadline was given, August 9. [ 5 ]
In February 2009, the neighbors of the "Mercado Walter Khon" have demanded attention from local authorities because streets were flooded with waste water coming out from the sewers. Because of this social pressure , the city council made the maintenance and cleaning of the sewers close by the area where waters arose.
Besides some maintenance facts that helped in the flooding, the city council does not restore the S-2 pumping station. Therefore, the wastewater is not properly pumped into the treatment plant.
According to the city's responsible, Marcelo Vidal, because of the constant rain added to garbage and plastic bags , the sewer system is not working properly. Even though he pointed that the main problem's origin is in the pumping station , the situation has not been solved up to date. [ 6 ]
In Peru , the norm has only few parameters with limits. [ 7 ] These parameters are: temperature (35 °C (95 °F)), fats and oil (100 mg/lt), PH (5 – 8.5), BOD (1000 mg/lt) and settleable solids . [ 7 ] However a more comprehensive norm was developed by the ministry of housing, which now is under review and analysis of the Ministry of the Environment . [ 8 ] In the present article, the values presented are the ones under approval. [ 9 ] This new regulation was developed because of the damage that industrial wastewater is causing to the sewer system. For example, in year 2006 a study showed that 58% of the sample (24 companies) surpassed the limit of BOD5 established in the current norm. [ 9 ] In the same year other study showed that 57% of the sample (9 companies) surpassed the same norm. [ 9 ]
Case description
In 2010, water quality was one of the main problems of Peru. Only 25% of the domestic water is treated, and the rest of it is thrown into rivers and lakes. This is why a series of measures have been addressed by government. In April 2010, the "National Authority of Water" will implement different laboratories in order to determine the pollution degree [ clarify ] of wastewater from industries. Penalties of up to 36 million Soles have been announced for companies that do not treat their residual water. [ 10 ]
In Brazil, the parameters presented correspond to the federal district . The regulation of the parameters is under the decree N°18.328 of June 8, 1997. [ 11 ] In the norm is established the maximum limit for industrial effluents in the federal district. Also it's stated the fines applied in the case the companies surpass the norm. Also the decree indicates the type of industry and the types of parameters, that each of them must control.
The norm that regulates the limits of discharge in Ecuador , is under the general law of environmental management, [ 12 ] and was created with the aim of regulate the discharge over sewer systems, criteria of water quality for several uses and the procedures for measuring the parameters on the water. [ 13 ] Also the norm establishes that companies must keep a record of the generated effluents with the main operational data related to the effluents. [ 12 ]
Case description
In December 2009, the Environment Ministry fined on November 25, five companies of Manta and Montecristi with US$43,600 after the failure to execute the environmental policy. These companies: SEAFMAN C.A., Treatment plant IROTOP S.A., LA FABRIL S.A., EUROFISH S.A., Y GONDI S.A. have to pay immediately. The results of laboratory samples proved that levels of different substances were over the limits that were established in the Environment Quality and Waste Water Regulations. An action plan has been implemented to avoid the surpass of the limits. [ 14 ]
In December 2007, in "Manglares" of "El Salvado", the fauna and flora which are extremely varied are being affected by households and companies, because of loads coming from thermal power plants. Such discharges generate high temperatures (more than 35 °C (95 °F)) that exceed the accepted and established limits, and in consequence the ecosystem is suffering irreversible damage.
Companies like "Categ" and "Electroguayas" have been forced to pay US$1000 fine, but this has not stopped this situation. Other company called "Interagua" has announced a new project that considers water treatment system for this area. The same is planned for Puerto Azul and the rest of the nearby cities. [ 15 ]
The national law that regulates water resource in Argentina is the Decree 674 of 1989, [ 16 ] established by the National Executive Power and applies to the Federal Capital and all the parties of Buenos Aires Province that are subscribed to the National Sanitary Works Entity regime. The aim of the law is to protect national water resources in means of good water usage, water pollution and the good functioning of the National Sanitary Works Entity installations.
As well, it's applied the Resolution 79179 of 1990, [ 17 ] which includes the instrumental arrangements for the Decree 674 implementation. This Resolution includes wastewater discharging parameters to sewer system, water course and rainwater collectors, which are included in Annex A of the law.
Case Description
In June 2006, in Argentina the concentration of different natural heavy materials , bacteria, nitrates and hydrocarbons exceed by much the figures considered dangerous. It is not by chance that rivers like the Paraná, Salado del Norte , Salado del Sur , Carcarañá , de la Plata and Colorado are among the most polluted on Earth. Argentina does not have control means for wastewater treatment or disposal. There is information that relates about important and numerous water bodies being affected by wastewater disposal, with intense eutrophication processes due to the lack of treatment.
One out of four hospital beds is occupied by someone with a water related illness. In some inner areas of the country, like Rosario and Córdoba , water bodies are so polluted that the work in the water treatment plants has been affected. There are some projects to build treatment plants in the main locations, but discharges keeps growing.
Disposals from companies added to the domestic ones in the Riachuelo-Matanza sum up to 368,000 cubic metres (13,000,000 cu ft) per day, which is double of the minimum average flow of the river. The mud in it has great concentrations of Chrome, Copper, Mercury , Zinc , and Lead. In addition, the highest concentrations of Lead and Chrome are located in the border between the councils of Avellaneda and Lanús , in the Buenos Aires province.
The given treatments are not sufficient by any means, moreover, the treatments done by companies to their waste water are between deficient and non-existing. Most of the water consumed by population comes from the same water bodies in which waste and domestic water is dumped, and because of the lack of treatment these populations ends up drinking water of doubtful quality or at a high purification cost. [ 18 ]
In May 2005, a report generated by the Nation's General Audit (AGN) states that the plants that produce water drinkable are also polluting with elements contained in their waste water, which are over the national and provincial legislation. [ 19 ]
Mexican Law of National Waters regulates water exploitation, use, distribution, control, and the preservation of water quantity and quality. [ 20 ]
To manage the wastewater disposal and control water sources quality, it was created in 1996 by the Environmental, Natural Resources and Fishing Secretarial, the official norm NOM-002-ECOL that establishes the maximum permissible limits of pollutants in wastewater discharges in urban sewer system. The norm specifies the permissible concentrations of pollutants per day, per month and instantaneous sampling, which are included in Chapter 4 of this norm. [ 21 ]
Case Description
In January 2010, members of the Ducks Unlimited Association of Mexico warned of the death of more than 5,000 migratory birds . The specialist from the association assured that the main cause of this episode was the non-treated waste waters from industrial polluters. He pointed out the real problem of pollution existing in the "De Silva" dam, and in some others dams in the state. He demanded intervention of the National Water Commission (Conagua) and from SEMARNAR, in order to regulate the discharge of waste water that ends up in the Turbio River . [ 22 ]
In April 2010, the Municipal Commission of Water and Sewer System of Altamira (COMAPA) was fined by the National Water Commission, between 40 and 50 thousand pesos, for not having a water treatment plant as stated by law for all municipalities of the state of Tataulipas. The next stage would be built a pumping station in "La Pedrera" and the facility must be finished this year. [ 23 ]
The main regulator norm for water management is the Decree 1594 of 1984, [ 24 ] which normalizes water usages and wastewater disposal through the country. The decree establishes water quality standards, which are guides to be used as a basis for decision making in assignation of water uses and determination of water characteristics for each application. Water discharging parameters to public sewage are described in Chapter VI of this decree.
Also, it was considered the Resolution 3957 of 2009 [ 25 ] to enlarge the water parameters comparison in Colombia. This resolution establishes the technical norm, for wastewater discharges management and control in public sewage for the capital district.
Case Description
A report published by the National University confirms the presence of Lead, Cadmium , Mercury and Arsenic in plants watered with the polluted water of the Bogotá River . According to it, vegetables have high levels of heavy metals that can be dangerous for human health.
For the Regional Autonomous Corporation (CAR) this is due to industrial downloads. In general, levels found in water, soil and vegetables of this area are much higher than the limits allowed by the World Health Organization . The authors, Soacha y Mosquera show figures much higher than the European Union limits. [ 26 ]
In August 2008, the industrial firm " Coca-Cola Femsa " was fined $111,000 USD due to its illegal discharge of industrial water in Bogotá, as informed by the District Environmental of the Capital District of Columbia. A technical report conducted by the Aqueduct and Sewer system of Bogotá proved the existence of some waste water disposal that does not go through the company's treatment plant.
The former Administrative Environmental Department (Dama) has given to the company an allowance for having a downloading point in October 2006, but the Aqueduct and Sewer system of Bogotá found that place has already four discharge points, none of them registered or authorized. Since January 2008, those four points were closed down and conducted to a treatment plant. [ 27 ]
The Environmental Organic Law of Venezuela gives the guidelines in terms of water management, as a duty of the state for the protection of watersheds . This in terms of classification and control of the quality of water bodies, control of effluent discharges or fluids susceptible of degrading the aquatic environment and alters the levels of quality required to preserve and improve the environment. The Decree 883 follows these guidelines, being Venezuela's national norm for water classification and control, created in 1995.
The Decree regulates the quality of water bodies and wastewater discharges. This law establishes the different types of water and the permissible parameters for water discharges in accordance to the final water use. Wastewater discharging parameters to public sewer system are contained in section V of Decree 883. [ 28 ]
The Congress of Paraguay created Law 1614 of 2000 as the general regulatory and tariff framework for drinking water and sanitary sewer supply. [ 29 ] Following the law's guidelines, was created the Quality Regulation for drinkable water supply and sanitation, which applies to the entire country. This regulation includes in its Title VI, all what refers to quality of the performance of sanitary sewer supply. In Annex 10 are shown the maximum limits for physicochemical parameters, specifying discharge values for the type of wastewater treatment applied. [ 30 ]
For purposes of having an idea of the requirements of the regulation, an index was created with the aim to rank the countries. This concept assumes that if a country has tighten limits than other, or if it declares explicitly a limit, then the regulation could be considered more stringent.
This index takes in account all the parameters listed in the table, assuming the following criteria. If a country doesn't have any regulation, then it will get 1, from a scale of 10. If the country has the minimum limit it will get 10 points, if it has the maximum then it will get 5 points. Later, an average is taken from all the parameters of the country, giving the index a relative position of all the countries. Afterwards, all the values are classified using quartiles .
A summary with the values of each country is presented below.
The pH is a chemical parameter that measures the acidity or basicity of the water and is commonly measured in situ . Distilled water has a pH of 7, [ 35 ] where less than 7 is considered acid and greater than 7 is considered basic. In most cases, low pH is due to organic overloading and low oxygen conditions in the water. This characteristic is strictly controlled because it has a direct effect on water ecosystems and sewer systems materials.
Usually, pH standard is between 6 and 9 and can vary easily depending on the discharge content. In this case, Peru was the country with the smallest range (6–8) and Argentina and Mexico were the ones with the widest range (5.5–10). No limit was found for Canada Regulation.
A low concentration of suspended solids in water or even complete removal after treatment is crucial to maintain water ecosystems development. High concentrations of suspended solids can slow down photosynthesis , reduce dissolved oxygen and increase water temperature.
That is why suspended solids is a relevant parameter in wastewater discharge, that can be attributed to both industrial and domestic wastewater. When comparing wastewater regulations, it was found that Bolivia has the strictest limit for this parameter (60 mg/L) while Colombia presented the highest limit (600 mg/L). The value presented for Colombia was extracted from the technical norm for wastewater discharges management and control in public sewage for the capital district. Within these two limit values is shown a big difference among the two countries regulations for these standard, whereas for Canada was encountered an average value of 350 mg/L.
The BOD 5 standard is also an indicator of the presence of settleable solids in water, but specifically for organic matter . BOD 5 represents the amount of oxygen required by microorganisms to stabilize organic material present in wastewater. A higher concentration of BOD 5 means a high load of organic matter to be stabilized by microorganisms.
Chile has the stricter regulation for BOD 5 permitting wastewater discharges with a value between 33 and 55 mg/L. Also, Chile was the only country that presented a range for the limit of this parameter. By the other hand, Colombia has the higher limit with 800 mg/L. In this case, is also taken the value from the Capital District Regulation, because there wasn't a specific value presented in the national norm, just said that BOD 5 removal must be greater than 80% for a new user. In comparison with Canada and the other countries, Chile's limit is a very strict value.
Arsenic is considered as a substance of sanitary interest and at the same time is one of the most toxic elements that exist. Arsenic can be found naturally in the environment and also be an essential trace element for some animals. Due to human activities, mainly through mining and melting, Arsenic can now be found on many more places than where they existed naturally.
World production of arsenic, in the form of its oxide , is around 50,000 tons per year. Chile and Mexico are primary exporters of arsenic. Also, it is mainly emitted by copper producing industries, but also during lead and zinc production and in agriculture. Arsenic can't be destroyed once it has entered the environment, which causes severe health effects on humans and animals. [ 36 ]
As mentioned before, Chile and Mexico are primary producers of arsenic and when checking arsenic limit values in their regulations aren't the more severe ones. Mexico and Brazil are the countries with a higher limit value and Ecuador stays with the lower limit. As Arsenic is also linked with agriculture; it is important to emphasize that the majority of the Latin-American countries are characterized by having an agricultural economy. As a result, limit values encountered for Arsenic in all the regulations varies from a small range of 0,1 to 1 mg/L.
Cadmium is also considered as a substance of sanitary interest. It can be found naturally in the environment and it always occurs in combination with zinc. In industry is a by-product of zinc, lead and copper extraction. It is also found in many manures and pesticides . [ 37 ]
Cadmium can easily end up in soils and transported to surface waters when using manures and pesticides. Regulations for Cadmium are strict, and thus little Cadmium enters the water through disposal of wastewater.
The main producing country is of zinc is Canada, with Mexico and Peru also being ones of the major suppliers. [ 38 ] In the regulations comparison, Cadmium standard was more severe in Ecuador with an acceptance of 0,02 mg/L, whilst Brazil was the laxer one with 1,5 mg/L. For the case of Canada, Mexico and Peru, the latter has the stricter limit among them with 0,2 mg/L, while the other two remain in the average with 0,7 mg/L.
Cyanide , a substance of sanitary concern, is only present in wastewater due to use and discharge from the industrial sector. Cyanide has severe effects both in human health and ecosystems. The severity of the harmful effects following cyanide exposure depends in part on the form of cyanide, such as hydrogen cyanide gas or cyanide salts. It becomes more dangerous when exposure concentrations are high. [ 39 ] Cyanide has been a major component of metal plating solutions and is mainly produced for the mining of gold and silver mining . [ 40 ]
In terms of Latino-American regulations, Argentina is the country that presents the harsher limit value with 0,1 mg/L. By the contrary, Mexico was the one with the higher limit value with 1,5 mg/L.
Among the Latin-American countries, Colombia is the only one that is mentioned as having gold mining industry. [ 38 ] The limit value for Cyanide is quite high (1 mg/L) to the limit value of Argentina. However, three more other countries have the same limit value for Cyanide.
Hexavalent chromium is a toxic component that can cause allergic reactions on the skin and also several problems in the respiratory system. [ 41 ] This is a component present in the industries of chemicals, leather, textiles , and electro painting , among others. [ 41 ]
The minimum requirement for this element is presented in Bolivia (0.1 mg/L), and the maximum is presented in Mexico (0.75 mg/L). Despite Brazil being one of the main producers of chromium, it doesn't have a maximum limit as do other countries.
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Sanitary engineering or sanitation engineering , also known as public health engineering or wastewater engineering , is the application of engineering methods to improve sanitation of human communities, primarily by providing the removal and disposal of human waste, and in addition to the supply of safe potable water . Traditionally a branch of civil engineering and now a subset of building services engineering and environmental engineering , in the mid-19th century, the discipline concentrated on the reduction of disease, then thought to be caused by miasma . This was accomplished mainly by the collection and segregation of sewerage flow in London specifically, and Great Britain generally. [ 1 ] These and later regulatory improvements were reported in the United States as early as 1865. [ 2 ]
It is also concerned with environmental factors that do not have an immediate and clearly understood effect on public health. Areas outside the purview of sanitary engineering include aesthetic concerns such as landscaping , and environmental conservation as it pertains to plants and animals .
Skills within this field are usually employed for the primary goal of disease prevention within human beings by assuring a supply of healthy drinking water , treatment of waste water, and removal of garbage from inhabited areas.
Compared to (for example) electrical engineering or mechanical engineering which are concerned primarily with closed systems , sanitary engineering is a very interdisciplinary field which may involve such elements as plumbing , fire protection , hydraulics , life safety, constructive modelling, information technology , project design, microbiology , pathology and the many divisions within environmental science and environmental technology . In some cases, considerations that fall within the field of social sciences and urban planning must be factored in as well.
Although sanitary engineering may be most associated with the design of sewers , sewage treatment and wastewater treatment facilities, recycling centers, public landfills and other things which are constructed, the term applies equally to a plan of action to reverse the effects of water pollution or soil contamination in a specific area.
Irrigation systems were invented five to seven thousand years ago as a means of supplying water to agriculture-based societies. Aqueducts and irrigation systems were among the first forms of wastewater engineering. As population centers became more dense, they were used to remove sewage from settlements. The Romans were among the first to demonstrate the effectiveness of the aqueduct. The Dark Ages marked a period where progress in water management came to a halt. [ 3 ]
As populations grew, the management of human waste became a growing concern and a public health threat. By the 1850s in London, more than 400,000 tons of sewage were flushed into the River Thames each day - around 150 million tons per year. [ 4 ] Diseases such as smallpox , diphtheria , measles , scarlet fever , typhus , cholera , and typhoid were spread via the contaminated water supply. [ 5 ] During the 19th century, major cities started building sewage systems to remove human waste out of cities and into rivers.
During the 1900s, the activated sludge process was invented. [ 6 ] The activated sludge process is a form of water purification that uses bacteria to consume human feces. Chlorine is used later in the process to kill off the bacteria. In the 1950s, the public health reports provided plans for supplying clean water for the public by first looking at potential hazards. The organization looked carefully at water contamination as well as how drinking water was being treated. They also prioritized finding methods that were effective, yet not too costly. [ 7 ] Sanitation cost is the main issue for many foreign (not the United States) countries. The average cost of home water and sanitation systems start at $50 a month, when many citizens don't make enough money to use on non-necessities. [ 8 ]
Over the centuries, much has changed in the field of wastewater engineering. Advancements in microbiology, chemistry, and engineering have drastically changed the field. Today, wastewater engineers also work on the collection of clean water for drinking, chemically treating it, and using UV light to kill off micro-organisms. They also treat water pollution in wastewater ( blackwater and greywater ) so that this water may be made safe for use without endangering the population and environment around it. Wastewater treatment and water reclamation are areas of concern in this field.
Prior to modern forms of sanitation in neighborhoods and cities, people would simply leave their trash on the street. In 1892, it was such an issue, that a man named Harm Huizenga volunteered to clean up the mess by himself. The Dutch man went around the streets in his wagon, picking up the garbage of the city of Chicago. Little efforts like that were present throughout the early 1900s, until around 1968. Huizenga's grandson, Wayne Huizenga, made his grandfather's idea into a business, Waste Management. By the seventies, waste management as a whole was seen as a necessary practice by the public. [ 9 ]
In the early 1940s, many counties in the state had problems with their disposal of waste, especially in the Lake Tahoe area. Citizens of these towns feared that their city's poor sewage systems would cause outbreaks in illnesses, like poliomyelitis , cholera , and hepatitis , to name a few. Cholera in particular is the biggest health risk attached to waste management. The illness is caused by bacteria, especially when a person ingests food or water that contain the bacteria. In poorer areas, this is extremely likely due to the cross contamination of waste and drinking water.
Wastewater engineering is not usually its own degree course, but a specialization from degrees such as environmental and sanitary engineering, sanitary engineering, civil engineering , environmental engineering , bio-chemical engineering, or chemical engineering . Formal education for wastewater engineers begins in high school with students taking classes such as chemistry, biology, physics, and higher mathematics including calculus. After high school most jobs require certification from a state agency. Those wanting to advance in the industry should pursue a sanitary engineering, environmental and sanitary engineering, civil engineering, mechanical engineering , environmental engineering, or a facilities engineering degree. Gaining experience through internships and working while in college is a common pathway toward advancement.
Education about waste treatment requires course work in systems design, machinery design principles, water chemistry, and similar coursework. Other classes may include Chemistry of Plant Processes, and various plant operations courses.
Wastewater engineers may advance in their careers through additional education and experience. With additional knowledge and experience one can become the manager of an entire plant. The accreditation body certifying the education for the degree and license is the Accreditation Board for Engineering and Technology (ABET). Over time, some companies may require the wastewater engineer to continue their education to keep up with any changes in technology.
Obtaining one's master's degree is encouraged since many companies list it as a preference in selection. [ 12 ] [ 13 ]
In this field 76 percent of those employed have a bachelor's degree, 17 percent have a master's degree and three percent have a post-doctoral degree as of 2013. [ 14 ] The average annual salary is approximately $83,360. [ 15 ]
Initial employment in wastewater engineering can be obtained by those with and without advanced formal education. The California State Water Resources Control Board (SWRCB), for example, shows how individuals can advance through a progression of certifications as Waste Water Treatment Operators. [ 16 ] The Board uses a five level classification system to classify water treatment facilities into categories I-V according to the population served and the complexity of the treatment system. [ citation needed ]
The Operator Certification requirements for water treatment operators and waste water treatment operators are described in detail by State law. To meet certification requirements, operators must submit an application to SWRCB, have the necessary work experience, meet the educational requirements, and pass an examination based on the knowledge, skill, and abilities described in the regulations. Operators are required to renew their certificates every three years. To be eligible for renewal, certified operators must complete a specified number of continuing education hours after the previous issuance of a certificate. [ 17 ]
Important job types working in sanitary engineering include sanitation workers , waste collectors and wastewater engineers. [ citation needed ]
Wastewater engineers use a variety of skills and must have knowledge of mechanical and environmental engineering. They are required to perform tasks and demonstrate knowledge in design, mathematics, English, construction, physics, chemistry, biology, management, and personnel. Wastewater engineers must have skills in complex problem solving, critical thinking, mathematics, active listening, judgement, reading comprehension, speaking, writing, science, and system analysis. [ 14 ] Typical work activities include problem solving, communication with management and staff, gathering information, analyzing data, evaluating standards and complying with them, and communicating with others in the field. [ citation needed ]
Wastewater engineers perform these activities by combining their knowledge and skills to perform tasks. These tasks are to understand computer-aided design programs, and to conduct studies for the construction of facilities, water supply systems and collection systems. They may design systems for wastewater collection machinery, as well as system components. They may perform water flow analysis, then select designs and equipment based on government and industry standards. [ 18 ] Some are involved with a specific area of concern such as waste collection or the maintenance of waste water facilities and stormwater drainage systems within an area. Others cover a broader scope of activities that might include maintenance of the public water supply , collection of residential yard waste program, disposal of hazardous waste , recycling strategies and even community programs where individuals or businesses "adopt" an area and either maintain it themselves or donate funds for doing so. [ citation needed ]
Wastewater engineers may also map out topographical and geographical features of Earth to determine the best means of collection, design pipe and pumped collection systems, and design treatment processes for collected wastewater. [ citation needed ]
Wastewater engineers work for private companies, state and local governments, and special districts.
Water managers confront new challenges and the need for new technology as water levels decrease due to increasingly frequent and extended droughts. Technologies such as sonar mapping are being used in wells to determine the volume of water that they can hold. For example, the United States Geological Survey and the State of New York worked together to map underground aquifers since the 1980s. [ 19 ] Today they have thorough maps of these aquifers to assist in water management.
Desalination plants may be required in the future for those regions hardest hit by water scarcity . Desalination is a process of cleaning water by means of evaporation. Water is evaporated and it passes through membranes. The water is then cooled and condenses allowing it to flow either back into the main water line or out to sea. [ 20 ]
Smart Sanitation: Advances in sensor technology, data analytics, and automation are enabling the development of smart sanitation systems that can monitor water quality, detect leaks, optimize treatment processes, and improve overall efficiency. Sanitary engineers need to leverage these technologies to enhance the performance and reliability of sanitation infrastructure. [ 21 ]
Wastewater treatment contributes to global warming in many ways. One of the factors that contributes to global warming is wastewater treatment facilities and their emissions of greenhouse gases . Some of those gases are carbon dioxide, methane, and nitrous oxide . These gases occur because of the decomposition of organic material from the anaerobic bacteria. These bacteria clean the leftover waste. Even if the anaerobic bacteria decomposition produces these gases, the percentage of greenhouse gases that other equipment produce is still greater than the contribution of the anaerobic bacteria. Also, the power usage from those machinery is very high. That is why many facilities are undergoing renovation to use higher levels of anaerobic bacteria compared to other types of equipment. [ 22 ]
Impacts of climate change on sanitary engineering vary based on region and the sanitation solutions employed there. In the Arctic, permafrost melting has caused damage to pipes and other infrastructure. [ 23 ] In the Northeastern United States, increased precipitation has overwhelmed aging infrastructure not equipped to handle the massive volume of water from heavy precipitation. [ 24 ] In the Western United States, prolonged drought has decreased water availability. This has led some wastewater facilities to expand recycled and reclaimed water programs. [ 25 ] Climate change has also affected water distribution pipes. Physical stress from climate change-related conditions such as extreme rainfall or drought increases the rate of pipe corrosion, adding to facility cost. [ 26 ]
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Wastewater quality indicators are laboratory test methodologies to assess suitability of wastewater for disposal, treatment or reuse. The main parameters in sewage that are measured to assess the sewage strength or quality as well as treatment options include: solids, indicators of organic matter, nitrogen, phosphorus, indicators of fecal contamination. [ 1 ] : 33 Tests selected vary with the intended use or discharge location. Tests can measure physical, chemical, and biological characteristics of the wastewater. Physical characteristics include temperature and solids. Chemical characteristics include pH value, dissolved oxygen concentrations, biochemical oxygen demand (BOD) and chemical oxygen demand (COD), nitrogen, phosphorus, chlorine. Biological characteristics are determined with bioassays and aquatic toxicology tests.
Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of pollution effect. Any oxidizable material present in an aerobic natural waterway or in an industrial wastewater will be oxidized both by biochemical (bacterial) or chemical processes. The result is that the oxygen content of the water will be decreased.
Aquatic organisms cannot survive outside of specific temperature ranges. Irrigation runoff and water cooling of power stations may elevate temperatures above the acceptable range for some species. Elevated temperature can also cause an algae bloom which reduces oxygen levels. ( See thermal pollution .) Temperature may be measured with a calibrated thermometer . [ 2 ] : 125–126
Solid material in wastewater may be dissolved, suspended, or settled. Total dissolved solids or TDS (sometimes called filterable residue) is measured as the mass of residue remaining when a measured volume of filtered water is evaporated . The mass of dried solids remaining on the filter is called total suspended solids (TSS) or nonfilterable residue. Settleable solids are measured as the visible volume accumulated at the bottom of an Imhoff cone after water has settled for one hour. [ 2 ] : 89–98 Turbidity is a measure of the light scattering ability of suspended matter in the water. [ 2 ] : 131–137 Salinity measures water density or conductivity changes caused by dissolved materials. [ 2 ] : 99–100
Virtually any chemical may be found in water, but routine testing is commonly limited to a few chemical elements of unique significance.
Water ionizes into hydronium (H 3 O + ) cations and hydroxyl (OH − ) anions . The concentration of ionized hydrogen (as protonated water) is expressed as pH . [ 2 ] : 406–407
Most aquatic habitats are occupied by fish or other animals requiring certain minimum dissolved oxygen concentrations to survive. Dissolved oxygen concentrations may be measured directly in wastewater, but the amount of oxygen potentially required by other chemicals in the wastewater is termed as oxygen demand. Dissolved or suspended oxidizable organic material in wastewater will be used as a food source. Finely divided material is readily available to microorganisms whose populations will increase to digest the amount of food available. Digestion of this food requires oxygen, so the oxygen content of the water will ultimately be decreased by the amount required to digest the dissolved or suspended food. Oxygen concentrations may fall below the minimum required by aquatic animals if the rate of oxygen utilization exceeds replacement by atmospheric oxygen. [ 3 ]
Basically, the reaction for biochemical oxidation may be written as:
Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows:
Since all natural waterways contain bacteria and nutrient, almost any waste compounds introduced into such waterways will initiate biochemical reactions (such as shown above). Those biochemical reactions create what is measured in the laboratory as the BOD.
Oxidizable chemicals (such as reducing chemicals) introduced into a natural water will similarly initiate chemical reactions (such as shown above). Those chemical reactions create what is measured in the laboratory as COD.
Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of pollution effect. The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygen demand of oxidizable pollutants.
The so-called 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period. The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the "Ultimate BOD". Because the Ultimate BOD is so time consuming, the 5-day BOD has been almost universally adopted as a measure of relative pollution effect.
There are also many different COD tests of which the 4-hour COD is probably the most common.
There is no generalized correlation between the 5-day BOD and the ultimate BOD. Similarly there is no generalized correlation between BOD and COD. It is possible to develop such correlations for specific waste contaminants in a specific wastewater stream but such correlations cannot be generalized for use with any other waste contaminants or wastewater streams. This is because the composition of any wastewater stream is different. As an example an effluent consisting of a solution of simple sugars that might discharge from a confectionery factory is likely to have organic components that degrade very quickly. In such a case, the 5 day BOD and the ultimate BOD would be very similar since there would be very little organic material left after 5 days. However a final effluent of a sewage treatment works serving a large industrialised area might have a discharge where the ultimate BOD was much greater than the 5 day BOD because much of the easily degraded material would have been removed in the sewage treatment process and many industrial processes discharge difficult to degrade organic molecules.
The laboratory test procedures for the determining the above oxygen demands are detailed in many standard texts. American versions include Standard Methods for the Examination of Water and Wastewater. [ 4 ]
Any oxidizable material present in an aerobic natural waterway or in an industrial wastewater will be oxidized both by biochemical (bacterial) or chemical processes. The result is that the oxygen content of the water will be decreased.
Nitrogen is an important nutrient for plant and animal growth. Atmospheric nitrogen is less biologically available than dissolved nitrogen in the form of ammonia and nitrates . Availability of dissolved nitrogen may contribute to algal blooms . Ammonia and organic forms of nitrogen are often measured as Total Kjeldahl Nitrogen , and analysis for inorganic forms of nitrogen may be performed for more accurate estimates of total nitrogen content. [ 2 ] : 406–407
Phosphates enter surface waters through both nonpoint sources and point sources . Nonpoint source (NPS) pollution refers to water pollution from diffuse sources. Nonpoint source pollution can be contrasted with point source pollution, where discharges occur to a body of water at a single location. The nonpoint sources of phosphates include natural decomposition of rocks and minerals, stormwater runoff , agricultural pollution , erosion and sedimentation , atmospheric deposition , and direct input by animals/wildlife. Point sources of phosphorus may include municipal sewage treatment plants and industrial dischargers. In general, the nonpoint source pollution typically is significantly higher than the point sources of pollution. Therefore, the key to sound management is to limit the input from both point and nonpoint sources of phosphate. High concentration of phosphate in water bodies is an indication of pollution and largely responsible for eutrophication . [ 5 ]
Phosphates are not toxic to people or animals unless they are present in very high levels. Digestive problems could occur from extremely high levels of phosphate.
The following criteria for total phosphorus were recommended by the U.S. Environmental Protection Agency .
Phosphorus is normally low (< 1 mg/L) in clean potable water sources and usually not regulated; [ 7 ] [ 8 ]
Chlorine has been widely used for bleaching , as a disinfectant , and for biofouling prevention in water cooling systems. Remaining concentrations of oxidizing hypochlorous acid and hypochlorite ions may be measured as chlorine residual to estimate effectiveness of disinfection or to demonstrate safety for discharge to aquatic ecosystems. [ 2 ] : 309–315
Water may be tested by a bioassay comparing survival of an aquatic test species in the wastewater in comparison to water from some other source. [ 2 ] : 685–689 Water may also be evaluated to determine the approximate biological population of the wastewater. Pathogenic micro-organisms using water as a means of moving from one host to another may be present in sewage. Coliform index measures the population of an organism commonly found in the intestines of warm-blooded animals as an indicator of the possible presence of other intestinal pathogens. [ 2 ] : 875–877
Aquatic toxicology tests are used to provide qualitative and quantitative data on adverse effects on aquatic organisms from a toxicant. Testing types include acute (short-term exposure), chronic (life span) and bioaccumulation tests. [ 9 ] Many industrial facilities in the US conduct "whole effluent toxicity" (WET) tests on their wastewater discharges, typically in combination with chemical tests for selected pollutants. [ 10 ]
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Wastewater treatment is a process which removes and eliminates contaminants from wastewater . It thus converts it into an effluent that can be returned to the water cycle . Once back in the water cycle, the effluent creates an acceptable impact on the environment. It is also possible to reuse it. This process is called water reclamation . [ 1 ] The treatment process takes place in a wastewater treatment plant. There are several kinds of wastewater which are treated at the appropriate type of wastewater treatment plant. For domestic wastewater the treatment plant is called a Sewage Treatment . Municipal wastewater or sewage are other names for domestic wastewater . For industrial wastewater, treatment takes place in a separate Industrial wastewater treatment , or in a sewage treatment plant. In the latter case it usually follows pre-treatment. Further types of wastewater treatment plants include Agricultural wastewater treatment and leachate treatment plants.
One common process in wastewater treatment is phase separation , such as sedimentation. Biological and chemical processes such as oxidation are another example. Polishing is also an example. The main by-product from wastewater treatment plants is a type of sludge that is usually treated in the same or another wastewater treatment plant. [ 2 ] : Ch.14 Biogas can be another by-product if the process uses anaerobic treatment. Treated wastewater can be reused as reclaimed water . [ 3 ] The main purpose of wastewater treatment is for the treated wastewater to be able to be disposed or reused safely. However, before it is treated, the options for disposal or reuse must be considered so the correct treatment process is used on the wastewater.
The term "wastewater treatment" is often used to mean " sewage treatment ". [ 4 ]
Wastewater treatment plants may be distinguished by the type of wastewater to be treated. There are numerous processes that can be used to treat wastewater depending on the type and extent of contamination. The treatment steps include physical, chemical and biological treatment processes. [ citation needed ]
Types of wastewater treatment plants include:
Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage discharges. [ 5 ] Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater . There are a high number of sewage treatment processes to choose from. These can range from decentralized systems (including on-site treatment systems) to large centralized systems involving a network of pipes and pump stations (called sewerage ) which convey the sewage to a treatment plant. For cities that have a combined sewer , the sewers will also carry urban runoff (stormwater) to the sewage treatment plant. Sewage treatment often involves two main stages, called primary and secondary treatment , while advanced treatment also incorporates a tertiary treatment stage with polishing processes and nutrient removal. Secondary treatment can reduce organic matter (measured as biological oxygen demand ) from sewage, using aerobic or anaerobic biological processes. A so-called quaternary treatment step (sometimes referred to as advanced treatment) can also be added for the removal of organic micropollutants , such as pharmaceuticals. This has been implemented in full-scale for example in Sweden. [ 6 ]
A large number of sewage treatment technologies have been developed, mostly using biological treatment processes. Design engineers and decision makers need to take into account technical and economical criteria of each alternative when choosing a suitable technology. [ 7 ] : 215 Often, the main criteria for selection are: desired effluent quality, expected construction and operating costs, availability of land, energy requirements and sustainability aspects. In developing countries and in rural areas with low population densities, sewage is often treated by various on-site sanitation systems and not conveyed in sewers. These systems include septic tanks connected to drain fields , on-site sewage systems (OSS), vermifilter systems and many more. On the other hand, advanced and relatively expensive sewage treatment plants may include tertiary treatment with disinfection and possibly even a fourth treatment stage to remove micropollutants. [ 6 ]
Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants . Most industrial processes, such as petroleum refineries , chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans . [ 9 ] : 1412 This applies to industries that generate wastewater with high concentrations of organic matter (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds ) or nutrients such as ammonia . [ 10 ] : 180 Some industries install a pre-treatment system to remove some pollutants (e.g., toxic compounds), and then discharge the partially treated wastewater to the municipal sewer system. [ 11 ] : 60
Agricultural wastewater treatment is a farm management agenda for controlling pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer , pesticides , animal slurry , crop residues or irrigation water. Agricultural wastewater treatment is required for continuous confined animal operations like milk and egg production. It may be performed in plants using mechanized treatment units similar to those used for industrial wastewater . Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs for seasonal use conditions from breeding or harvest cycles. [ 13 ] : 6–8 Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes.
Leachate treatment plants are used to treat leachate from landfills . Treatment options include: biological treatment, mechanical treatment by ultrafiltration , treatment with active carbon filters, electrochemical treatment including electrocoagulation by various proprietary technologies and reverse osmosis membrane filtration using disc tube module technology. [ 14 ]
The unit processes involved in wastewater treatment include physical processes such as settlement or flotation and biological processes such oxidation or anaerobic treatment. Some wastewaters require specialized treatment methods. At the simplest level, treatment of most wastewaters is carried out through separation of solids from liquids , usually by sedimentation . By progressively converting dissolved material into solids, usually a biological floc or biofilm , which is then settled out or separated, an effluent stream of increasing purity is produced. [ 2 ] [ page needed ] [ 15 ]
Phase separation transfers impurities into a non-aqueous phase . Phase separation may occur at intermediate points in a treatment sequence to remove solids generated during oxidation or polishing. Grease and oil may be recovered for fuel or saponification . Solids often require dewatering of sludge in a wastewater treatment plant . Disposal options for dried solids vary with the type and concentration of impurities removed from water. [ 16 ]
Solids such as stones , grit, and sand may be removed from wastewater by gravity when density differences are sufficient to overcome dispersion by turbulence . This is typically achieved using a grit channel designed to produce an optimum flow rate that allows grit to settle and other less-dense solids to be carried forward to the next treatment stage. Gravity separation of solids is the primary treatment of sewage , where the unit process is called "primary settling tanks" or "primary sedimentation tanks". [ 17 ] It is also widely used for the treatment of other types of wastewater. Solids that are denser than water will accumulate at the bottom of quiescent settling basins . More complex clarifiers also have skimmers to simultaneously remove floating grease such as soap scum and solids such as feathers, wood chips, or condoms . Containers like the API oil-water separator are specifically designed to separate non-polar liquids. [ 18 ] : 111–138
Oxidation reduces the biochemical oxygen demand of wastewater, and may reduce the toxicity of some impurities. Secondary treatment converts organic compounds into carbon dioxide , water , and biosolids through oxidation and reduction reactions. [ 19 ] Chemical oxidation is widely used for disinfection. [ 20 ]
Advanced oxidation processes are used to remove some persistent organic pollutants and concentrations remaining after biochemical oxidation. [ 18 ] : 363–408 Disinfection by chemical oxidation kills bacteria and microbial pathogens by adding hydroxyl radicals such as ozone , chlorine or hypochlorite to wastewater. [ 2 ] : 1220 These hydroxyl radical then break down complex compounds in the organic pollutants into simple compounds such as water, carbon dioxide, and salts . [ 22 ]
Anaerobic wastewater treatment processes (for example UASB , EGSB ) are also widely applied in the treatment of industrial wastewaters and biological sludge.
Polishing refers to treatments made in further advanced treatment steps after the above methods (also called "fourth stage" treatment). These treatments may also be used independently for some industrial wastewater. Chemical reduction or pH adjustment minimizes chemical reactivity of wastewater following chemical oxidation. [ 18 ] : 439 Carbon filtering removes remaining contaminants and impurities by chemical absorption onto activated carbon . [ 2 ] : 1138 Filtration through sand (calcium carbonate) or fabric filters is the most common method used in municipal wastewater treatment.
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watchOS is the operating system of the Apple Watch , developed by Apple . It is based on iOS , the operating system used by the iPhone , and has many similar features. [ 4 ] It was released on April 24, 2015, along with the Apple Watch, the only device that runs watchOS. watchOS exposes an API called WatchKit for developer use.
The second version, watchOS 2, included support for native third-party apps and other improvements, and was released on September 21, 2015. [ 5 ] [ 6 ] [ 7 ] The third version, watchOS 3, was released on September 13, 2016, to emphasize better performance and include new watch faces and stock apps. The fourth version, watchOS 4, was released on September 19, 2017. The fifth version, watchOS 5, was released on September 17, 2018, [ 8 ] to add more third-party support and new workouts, along with the " Walkie-Talkie " feature. [ 9 ] The sixth version, watchOS 6, was released on September 19, 2019. [ 10 ] The seventh version, watchOS 7, was released on September 16, 2020, to support handwashing and sleep tracking. [ 11 ] [ 12 ] The eighth version, watchOS 8, was released on September 20, 2021, with updates in health monitoring, visuals, and apps. [ 13 ] The ninth version, watchOS 9, was released on September 12, 2022. The tenth version, watchOS 10, was released on September 18, 2023. The 11th and the latest version, watchOS 11, was released on September 16, 2024.
The home screen, rendered by and also known as "Carousel", [ 4 ] consists of circular application icons that can be zoomed in and out with the Digital Crown and launched by touching the display, allowing users to access their favorite apps.
Prior to watchOS 3, "Glances" offered quick access to summaries of the most frequently used native and third-party applications. [ 14 ] The Glances view was opened with a swipe-up gesture from the watch face screen. In watchOS 3, Glances were replaced with a redesigned Control Center that mirrors the functionality seen in iOS, providing a more unified experience across Apple devices. The Control Center is accessed with a swipe-up gesture from the watch face screen. Additionally, the friends menu, previously activated with the side button, was repurposed as a dedicated dock for apps, enhancing multitasking and app management.
Prior to watchOS 7, different actions and options appeared depending on whether the user taps or deep-presses, which an Apple Watch detects with its pressure-sensitive ( Force Touch ) Display. [ 15 ] Force Touch was completely removed in watchOS 7, and all actions requiring the feature were moved to specific options in the Settings app or to long-press actions. [ 16 ] With the launch of watchOS 7, Force Touch technology was phased out. This feature was replaced by additional options in the Settings app and extended press gestures to accommodate all necessary interactions. This change streamlined the interaction model, making it more consistent with other Apple devices that do not support Force Touch.
As of watchOS 10, the interface has been further refined to enhance user accessibility and interaction. New customization features allow users to personalize their Carousel with greater ease, and improvements in app responsiveness and animation enrich the overall user experience. These updates demonstrate Apple's ongoing commitment to enhancing usability while maintaining the sleek, minimalist design that users appreciate.
Since its inception, watchOS has supported an increasing number and variety of health metrics for measurement and tracking. These include:
For several years, Apple has been developing its HealthKit product in an attempt to penetrate the lucrative healthcare and wellness industry, which CB Insights believe holds a huge growth opportunity for Apple. [ 25 ] This was confirmed by Jony Ive , Apple's former chief designer, in an interview. He said that health was a crucial element in the Apple Watch since the day of its inception and that the developmental trajectory of the hardware and the watchOS were geared towards health-based capabilities. [ 26 ] Ive pointed out that one of the primary apps that shipped with the first watchOS allowed users to track and communicate as well as encourage them to move, exercise, and stand. He said:
Many of us have our phones with us all the time, but they aren't connected to you. Imagine having something this powerful with you at all times, and what opportunities that might present to the user. The opportunity is phenomenal. Particularly when [you] don't understand just where we are today in terms of technology and capability, but where we are headed. [ 26 ]
Applications have been developed for watchOS that not only keep users active but also diagnose illnesses. For example, the app called DeepHeart, a deep-learning network that can detect atrial fibrillation , hypertension , sleep apnea, and diabetes . [ 27 ] It taps into the HealthKit platform to collect data, particularly those collected by the Apple Watch's heart sensor. [ 28 ]
The first version of watchOS 1 was 1.0 and was based on iOS 8.2. The second version of watchOS 1 was 1.0.1 and was based on iOS 8.3.
Initial release on Apple Watch (1st Generation).
New Watch faces
Siri
Activity and Workout
Apple Pay and Wallet
Friends
Maps
Music
Miscellaneous
Developer
Navigation
New Watch faces
Activity
Workout
For Wheelchairs
Breathe app
Communication
Scribble
Emergency SOS
Home
Miscellaneous
Update withdrawn due to reports of Apple Watches no longer working after the update [ 37 ]
Limited support on the Apple Watch (1st generation) . Some features are not supported on the Apple Watch Series 1 and Apple Watch Series 2
Initial release on Apple Watch Series 3
Drops support for iPhone 5 and iPhone 5C
New Watch faces
Activity
Workout
Heart Rate
Music
Miscellaneous
watchOS 5 was first shown to the public at the 2018 San Jose WWDC developer conference held on June 4, 2018 by Apple. It had an instant watch-to-watch Walkie-Talkie mode. [ 39 ] With this release, Apple dropped support for the first generation Apple Watch. watchOS 5 was the first version of watchOS to bring 64-bit support.
Some features are not supported on the Apple Watch Series 1 and Apple Watch Series 2 .
Initial Release on Apple Watch Series 4
Drops support for the Apple Watch (1st generation)
Improvements and bug fixes
No published security notes. [ 48 ]
No published security notes. [ 48 ]
Security notes
No published security notes. [ 48 ]
Security notes
Apple announced a new version of watchOS that would contain features such as the App Store, a calculator with tip tools, an audiobooks app, noise level monitoring, and Apple's Voice Memos app, at WWDC 2019 held on 3 June 2019. [ 49 ] [ 50 ] [ 51 ] It also enables special games that can only be played on the Watch interface. With this release, Apple dropped support for iPhone 5s, 6 and 6 Plus. However, watchOS 6 has limited support on Apple Watch Series 1 and 2 . watchOS 6.3 is the final release supported on the Apple Watch Series 1 and 2 .
Limited support on the Apple Watch Series 1 and Apple Watch Series 2 .
Initial Release on Apple Watch Series 5
Not released for Apple Watch Series 1 and 2
Drops support for iPhone 5s , iPhone 6 and iPhone 6 Plus
Improvements and bug fixes
Security notes
No published security notes. [ 48 ]
Security notes
No published security notes. [ 48 ]
Security notes
Security notes
Security notes
Security notes
Security notes
Apple announced watchOS 7 at the 2020 Worldwide Developers Conference on June 22, 2020. With watchOS 7, Apple dropped support for Apple Watch Series 1 and 2 . watchOS 7 has limited support on the Apple Watch Series 3 .
Limited support on the Apple Watch Series 3 .
Initial Release on Apple Watch SE and Apple Watch Series 6
Drops support for the Apple Watch Series 1 and Apple Watch Series 2
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No published security notes. [ 48 ]
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No published security notes. [ 48 ]
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Apple announced watchOS 8 at the 2021 Worldwide Developers Conference on June 7, 2021. Apple Watch models supporting watchOS 7 can also support watchOS 8. However, like watchOS 7, watchOS 8 has limited support on Apple Watch Series 3 . It is also the last version of watchOS to be supported on Apple Watch models with 32-bit processors .
Limited support on the Apple Watch Series 3 .
19R346
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No published security notes. [ 48 ]
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Apple announced watchOS 9 at the 2022 Worldwide Developers Conference on June 6, 2022. With this release, Apple dropped support for the Apple Watch Series 3 , which was the last Apple Watch model with a 32-bit processor, making watchOS 9 the first version of watchOS to run exclusively on Apple Watch models with 64-bit processors .
Drops support for the Apple Watch Series 3, iPhone 6S, 6S Plus, SE (1st gen), 7 and 7 Plus
Security notes
No published security notes. [ 48 ]
No published security notes. [ 48 ]
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Apple announced watchOS 10 at the 2023 Worldwide Developers Conference on June 5, 2023. With this release, Apple dropped support for iPhone 8, 8 Plus and X. All Apple Watch models supporting watchOS 9 also support watchOS 10. [ 58 ]
Limited support on the Apple Watch SE (1st generation).
Drops support for the iPhone 8, 8 Plus and X
Apple announced watchOS 11 at the 2024 Worldwide Developers Conference on June 10, 2024. With this release, Apple drops support for the Apple Watch Series 4 and Apple Watch Series 5 . [ 61 ] This marks the first time 64-bit Apple Watch devices were dropped.
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A watchclock is a mechanical clock used by security guards as part of their guard tour patrol system which require regular patrols. The most commonly used form was the mechanical clock systems that required a key for manual punching of a number to a strip of paper inside with the time pre-printed on it. Recently, electronic systems have increased in popularity due to their light weight, ease of use, and downloadable logging capabilities. [ 1 ]
This increase in the electronic systems led the largest U.S. manufacturer of watchclocks, Detex, to discontinue all of their mechanical watchclocks on December 31, 2011, including the Detex Newman which had been manufactured for 130 years.
Watchclocks often had a paper or light cardboard disk or paper tape placed inside for a set period of time, usually 24 hours for disk models, and 96 hours for tape models. The user would carry the clock to each checkpoint where a numbered key was mounted (typically chained in place, ensuring that the user was present). That key was then inserted into the clock and turned, which would imprint the disk with the key number. The paper disk or tape had the times pre-printed and the key impressed the key number on the corresponding time. After the shift (or a specified time period, up to 96 hours in the case of the Detex Guardsman clocks), an authorized person (usually a supervisor), would unlock the watchclock and retrieve the disk or tape and insert a new one. In the case of Detex brand clocks, each time the cover is opened or closed, a mechanical device would puncture the disk or tape at the current time; if a disk had more than two perforations on it, it proved that the clock had been opened and possibly tampered with, or records forged.
The approximately five pound circular watchclock was enclosed in a black leather pouch attached to a leather strap and carried over the shoulder. Inside buildings mounted near doors, were watchclock stations consisting of a small metal box with a hinged lid, which contained a numbered key affixed by a twelve-inch chain. The watchman would insert the key into the clock, rotate it and a numeric stamp would be pressed onto a roll or disk of paper locked inside the clock.
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The Watchman Problem is an optimization problem in computational geometry where the objective is to compute the shortest route a watchman should take to guard an entire area with obstacles given only a map of the area. The challenge is to make sure the watchman peeks behind every corner and to determine the best order in which corners should be visited in. The problem may be solved in polynomial time when the area to be guarded is a simple polygon . [ 1 ] [ 2 ] [ 3 ] The problem is NP-hard for polygons with holes , [ 1 ] but may be approximated in polynomial time by a solution whose length is within a polylogarithmic factor of optimal. [ 4 ]
This geometry-related article is a stub . You can help Wikipedia by expanding it .
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https://en.wikipedia.org/wiki/Watchman_route_problem
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Water, Air, & Soil Pollution is a monthly peer-reviewed scientific journal covering the study of environmental pollution . It was established in 1971 and is published by Springer Science+Business Media . The editor-in-chief is Jack T. Trevors. According to the Journal Citation Reports , the journal has a 2017 impact factor of 1.769. [ 1 ]
This article about an environment journal is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page .
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https://en.wikipedia.org/wiki/Water,_Air,_&_Soil_Pollution
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The Water, Sanitation and Hygiene Monitoring Program or WaSH MP is a local initiative that is responsible for monitoring the enduring crisis in the water sector in the Palestinian territories (oPt).
In a region already suffering severe water stress, the ongoing political, economic and social crisis in the oPt has resulted in near catastrophic consequences for the water, sanitation and hygiene (WaSH) situation. Local and international non-governmental organizations (NGOs) working in the water sector, in tandem with the Palestinian Water Authority (PWA), are trying, under restrictive political conditions and within limited budgets, to ensure that all Palestinians are able to access sufficient water supplies and sanitation services. [ citation needed ]
The Palestinian Hydrology Group (PHG), as the leading Palestinian NGO working in the water sector, has undertaken the responsibility for initiating the program. In June 2002 the WaSH MP was launched in response to the urgent need for increased information, resources and action related to the deteriorating WaSH situation in the West Bank and Gaza Strip . The need for quantitative data to support ongoing advocacy and humanitarian initiatives by donors, international NGOs, and local NGOs working in the water sector in the oPt has been the main driving force behind the initiation and further development of the WaSH MP. [ citation needed ]
The main objective of the WaSH MP is to respond to the water crisis in the oPt by increasing local and international awareness of the WaSH situation while further encouraging mobilization around the emergency needs of the most vulnerable communities. Additionally, the hope is that this will help to stimulate political and environmental change through the use of timely and pertinent information (data) in order to help remedy the dire WaSH situation. These efforts are inline with achieving the UN Millennium Development Goals (MDG’s) [ 1 ] in relation to water and sanitation (UN MDG 7 – Target 10). [ 2 ] As part of the WaSH MP, PHG has taken the responsibility for monitoring the extent to which Target 10 can be realized under these deteriorating conditions in the oPt, and for identifying the limitations in its achievement. In the process of identifying the main constraints facing the realization of this goal, and in addressing water issues and crises afflicted on Palestinian communities in the West Bank and Gaza Strip, reliable water related data collection has become of paramount importance. [ citation needed ]
In the current phase of the program, the WaSH MP managed to collect data from 660 of the 708 Palestinian communities [ 3 ] and had disseminated the information through annual, monthly and weekly reports. This program covers the overwhelming majority of communities in the oPt and spans across all governorates throughout the West Bank and Gaza Strip. A total of 660 communities are now surveyed during each annual monitoring period. The remaining 48 communities which are not surveyed as part of the ongoing monitoring process are left out due to various reasons including: religious locality with limited access, East Jerusalem communities (limited access to municipal information), no people due to Israeli planned transfer, seasonal community, and or a community with services that are an integral part of another locality. [ citation needed ]
Information quality of WaSH MP data outputs is defined in terms of its "fitness for use" by the end user. The six dimensions of data quality are relevance, accuracy, timeliness, accessibility, interpretability, and coherence. The information is collected from the field, by means of a standardized questionnaire, and is checked as part of a quality assurance process by Technical Field Monitors (TFMs) who are located in the West Bank and Gaza Strip. In order to provide this service the WaSH MP has further refined its data criteria by creating twelve indicators. The twelve indicators currently used are as follows: status of households with year-round access to a water source, per capita water supply, wastewater network coverage, cesspit and septic tank coverage, availability of solid waste collection system, prevalence of water-borne diseases , status of operation and maintenance of water supply facilities, cost recovery for water supply services, unaccounted-for water within the water supply system, monthly household income spent on water supply, monthly household income spent on sanitation, as well as a compilation of major community problems and needs. The commitment on behalf of the WaSH MP to the continuous improvement of data will ensure that international organizations, donors, INGO’s, NGO’s, academics and all interested persons receive WaSH-related data that meets the growing needs of the Palestinian people, as well as the development and humanitarian sectors. [ citation needed ]
The WaSH MP has been alerting organizations working in the water sector in the oPt to problems that require urgent and longer-term attention. Furthermore, the WaSH MP has striven in educating those outside the Palestinian water sector nationally and internationally on the WaSH crisis in the oPt. The program also provides a direct channel for WaSH related information regarding the most vulnerable areas to be disseminated to the humanitarian sector and the international community in order for them to stay abreast of emergency needs. As part of the program deliverables an annual report is published along with quarterly based need assessment reports, monthly data sets, and pilot monitoring of selected Palestinian communities. Additionally emergency alerts are posted on a need be basis and are identified as part of the continuous monitoring process. The WaSH MP website comprises an archive of all published material, including reports, alerts and photographs to serve as a reference source. [ citation needed ]
In the past, WaSH related data collection in the oPt has been difficult to source, disparate in nature, and generally incomplete. The data available failed to describe, accurately, the reality on the ground for many communities — much less has it served as a tool for improving the dissemination of critical information. It also failed to provide a comprehensive indication of the vulnerability of numerous communities, and could not be relied upon to assess whether these communities had the capacity and coping mechanisms to solve WaSH related problems. This can be attributed to the difficulties in acquiring a consistent source of data while under occupation. The unpredictable nature of life in the oPt is primarily due to the lack of control Palestinians have over their own affairs. This creates numerous obstacles to planning and implementing a monitoring program.
In the past financial support has been awarded by Oxfam-GB and UNICEF . [ citation needed ]
1 United Nations Millennium Development Goals (MDG’s) United Nations Millennium Development Goals 2 UN MDG 7 – Target 10: United Nations Millennium Development Goal 7 aims to ensure environmental sustainability. Among the targets related to Goal 7, is Target 10: “To cut in half, by 2015, the proportion of people without sustainable access to safe drinking water and basic sanitation”. United Nations Millennium Development Goals 3 The Palestinian Central Bureau of Statistics (PCBS) identified 708 communities within the oPt as part of the only comprehensive census in 1997. PCBS.ORG
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A water-based pipe coating is an environmentally friendly coating that is applied to the inner and outer surfaces of ductile iron pipe . The coating serves to protect the water supply lines from corrosion whether from the outside or the inside. It also serves to protect the drinking water from contamination . The coating is an emulsion manufactured using asphaltene and water primarily, with other raw materials according to the manufacturer's specifications.
Water-based coatings began development in the late 1980s. In the early 1990s they began to be widely used, specifically marketed towards drinking water supply lines. Previously, water supply lines were coated using a harmful solvent-based coating, using such solvents as benzene , toluene , hexane and other volatile organic compounds (VOC).
These coatings are manufactured using a batching system. A solution of raw materials and water is prepared, and the solution is milled with an asphaltene, which serves as a clean building block and a base resin. After the material is processed, it goes through a series of let-down, filtering, and quality control tests.
The major use of water-based pipe coating is for ductile iron pipe that comprises water supply lines infrastructure . It can also be utilized for pipe flanges and fittings, gray iron pipe (sewer lines), stormwater sealing, utility box sealing, and septic tank and vault sealing.
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https://en.wikipedia.org/wiki/Water-based_pipe_coating
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Water-in-water (W/W) emulsion is a system that consists of droplets of water-solvated molecules in another continuous aqueous solution; both the droplet and continuous phases contain different molecules that are entirely water-soluble. [ 1 ] As such, when two entirely aqueous solutions containing different water-soluble molecules are mixed, water droplets containing predominantly one component are dispersed in water solution containing another component. [ 2 ] Recently, such a water-in-water emulsion was demonstrated to exist and be stable from coalescence by the separation of different types of non- amphiphilic , but water-soluble molecular interactions. [ 3 ] These molecular interactions include hydrogen bonding , pi stacking , and salt bridging . This w/w emulsion was generated when the different water-solvated molecular functional groups get segregated in an aqueous mixture consisting of polymer and liquid crystal molecules.
This water-in-water emulsion consists of liquid crystals suspended as water-solvated droplets dispersed in a solution of polymer whose solvent is also water. The liquid crystal component of the emulsion is disodium cromolyn glycate (DSCG). This molecule is an anti-asthmatic drug, but also exists as a special type of liquid crystal when the concentration of DSCG is ~9-21 wt%. Unlike conventional lyotropic liquid crystals which consist of oily molecules such as 5CB , DSCG molecules are not amphiphilic, but entirely water-soluble. Thus, the separation of hydrophobic / hydrophilic groups cannot be applied to DSCG. The polymer solution serves as the medium or continuous phase of the w/w emulsion. Apart from being water-soluble, one important criterion for the generation of this w/w emulsion system is that the polymer cannot bear functional groups that interact strongly with DSCG. As such, ionic polymer when mixed with DSCG does not form w/w emulsion, but gives rise to a homogeneous solution or a precipitate solution. Consequently, the known polymers that afford w/w emulsion include polyacrylic amides and polyols . Surprisingly, some of these water-in-water emulsions can be exceptionally stable from coalescence for up to 30 days.
Because molecules of liquid crystal assume a preferred common orientation among themselves, the overall orientation of liquid crystals in a droplet is only stable in certain configurations (Fig. 3). As water solvated droplets in a w/w emulsion, DSCG molecules would align in a preferred direction on the surface of the droplet. To minimize the overall energy of the system, the DSCG molecules in the droplet prefer to align either parallel or perpendicular to the surfaces of the droplets.(Fig. 4A,B).
The stability of this water-in-water emulsion from coalescence is attributed to three molecular forces:
1. The separation of different molecular forces at the beginning of the droplet formation. Similar forces tend to stay together: pi-stacking and salt bridging are the two dominant forces in the liquid crystal droplet phase, while hydrogen bonding governs in the continuous polymer phase.
2. As the droplet size increases, the molecular interactions at the interface of the droplet phase and the continuous phase become stronger through multivalent interactions. The strengthening of interfacial molecular interactions in w/w emulsions results in the formation of a layer of polymer that coats the surface of the droplet which consequently prevents droplets from clumping together.
3. In addition, it is also proposed that when two liquid crystal droplets merge (coalescence), the orientation of the liquid crystal molecules in the two merging droplets must change to “adapt” to each other, and thus incur an energy penalty which prevent the occurrence of coalescence.
This w/w emulsion also represents a new class of polymer dispersed liquid crystals(PDLC). Traditionally known PDLC consists of oil-in-water emulsion where the oily droplet is a thermotropic liquid crystal such as 4-pentyl-4'-cyanobiphenyl (5CB), and the water phase contains certain polymers. In comparison, this water-in-water emulsion consists of Polymer-Dispersed Lyotropic Liquid Crystals, where the lyotropic liquid crystal is DSCG molecules solvated in water. Traditional PDLCs have found application, from switchable windows to projection displays. The water-in-water emulsion of polymer-dispersed lyotropic liquid crystals has the potential for building highly bio-functional materials because of its compatibility with protein structure.
Other known types of water-in-water emulsions involve the separation of different biopolymers in aqueous solution.
4. (a) Terentjev, E. M. Europhys. Lett. 1995, 32, 607–612. (b) Poulin,P.; Stark, H.; Lubensky, T. C.; Weitz, D. A. Science 1997, 275, 1770–1773.
5. Scholten, E.; Sagis, L. M. C.; Van der Linden, E., Effect of Bending Rigidity and Interfacial Permeability on the Dynamical Behavior of Water-in-Water Emulsions. Journal of Physical Chemistry B 2006, 110, (7), 3250–3256.
1. Salt bridging and example of salt bridges http://www.cryst.bbk.ac.uk/PPS2/projects/day/TDayDiss/SaltBridges.html
2. Tutorial on liquid crystals http://outreach.lci.kent.edu/
3. Introduction to polymer dispersed liquid crystals (PDLC)
4. Droplet configuration of PDLC’s http://plc.cwru.edu/tutorial/enhanced/files/pdlc/droplet/droplet.htm
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The water-pouring algorithm is a technique used in digital communications systems for allocating power among different channels in multicarrier schemes. It was described by R. C. Gallager in 1968 [ 1 ] along with the water-pouring theorem which proves its optimality for channels having Additive White Gaussian Noise (AWGN) and intersymbol interference (ISI).
For this reason, it is a standard baseline algorithm for various digital communications systems. [ 2 ]
The intuition that gives the algorithm its name is to think of the communication medium as if it was some kind of water container with an uneven bottom. Each of the available channels is then a section of the container having its own depth, given by the reciprocal of the frequency-dependent SNR for the channel. [ 1 ] [ 3 ] To allocate power, imagine pouring water into this container (the amount depends on the desired maximum average transmit power). After the water level settles, the largest amount of water is in the deepest sections of the container. This implies allocating more power to the channels with the most favourable SNR. Note, however, that the ratio allocation to each channel is not a fixed proportion but varies nonlinearly with the maximum average transmit power.
This article related to telecommunications is a stub . You can help Wikipedia by expanding it .
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Water-reactive substances [ 1 ] are those that spontaneously undergo a chemical reaction with water, often noted as generating flammable gas. [ 2 ] Some are highly reducing in nature. [ 3 ] Notable examples include alkali metals , lithium through caesium , and alkaline earth metals , magnesium through barium .
Some water-reactive substances are also pyrophoric , like organometallics and sulfuric acid. The use of acid-resistant gloves and face shield is recommended for safe handling; fume hoods are another effective control of such substances. [ 4 ]
Water-reactive substances are classified as R2 under the UN classification system and as Hazard 4.3 by the United States Department of Transportation . In an NFPA 704 fire diamond's white square, and in similar contexts, they are denoted as " W ". The classification of substances as water-reactive is largely a consideration for the safety of firefighting and transportation operations. [ 5 ]
All chemicals that react vigorously with water or liberate toxic gas when in contact with water are recognized for their hazardous nature in the "Approved Supply List", [ 6 ] or the list of substances covered by the international legislation on major hazards [ 7 ] many of which are commonly used in manufacturing processes.
The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table - they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.
The Group 1 metal (M) is oxidised to its metal ions , and water is reduced to hydrogen gas (H 2 ) and hydroxide ion (OH − ), giving a general equation of:
The Group 1 metals or alkali metals become more reactive as their number of energy levels inceases.
The alkaline earth metals (Be, Mg, Ca, Sr, Ba, and Ra) are the second most reactive metals in the periodic table, and, like the Group 1 metals, have increasing reactivity with increasing numbers of energy levels. Beryllium (Be) is the only alkaline earth metal that does not react with water, though it reacts with steam if it is heated to high enough temperatures. [ 9 ] Additionally, beryllium has a resistant outer oxide layer that lowers its reactivity at lower temperatures.
Magnesium shows insignificant reaction with water, but burns vigorously with steam or water vapor to produce white magnesium oxide and hydrogen gas: [ 10 ]
Magnesium has a mild reaction with cold water. The reaction is short-lived because the magnesium hydroxide layer formed on the magnesium is almost insoluble in water and prevents further reaction.
Mg(s) + 2H 2 O(l) ⟶ Mg(OH) 2 (s) + H 2 (g) [ 11 ]
A metal reacting with cold water will produce a metal hydroxide and hydrogen gas. However, if a metal reacts with steam, like magnesium, metal oxide is produced as a result of metal hydroxides splitting upon heating. [ 12 ]
The hydroxides of calcium, strontium and barium are only slightly water-soluble but produce sufficient hydroxide ions to make the environment basic , giving a general equation of:
Radium reacts similarly to the rest of the alkaline earth metals (other than magnesium), forming radium hydroxide and hydrogen gas. [ 14 ] Notably, radium hydroxide is the most soluble out of all alkaline earth hydroxide species. [ 15 ]
Hydrogen is always produced when a metal reacts with cold water or steam. [ 16 ]
Halogens are so named due to their potential to form salts , and form many simple strong acids with hydrogen. Out of the four stable halogens, only fluorine and chlorine have reduction potentials higher than that of oxygen , allowing them to form hydrofluoric acid and hydrochloric acid directly through reaction with water. [ 17 ] The reaction of fluorine with water is especially hazardous, as an addition of fluorine gas to cold water will produce hydrofluoric acid, oxygen gas, and ozone . [ 18 ] However, the reaction is fairly slow. [ 19 ]
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Water-use efficiency (WUE) refers to the ratio of plant biomass to water lost by transpiration , can be defined either at the leaf , at the whole plant or a population/stand/field level:
Research to improve the water-use efficiency of crop plants has been ongoing from the early 20th century, however with difficulties to actually achieve crops with increased water-use efficiency. [ 5 ]
Intrinsic water-use efficiency W i usually increases during soil drought , due to stomatal closure and a reduction in transpiration, and is therefore often linked to drought tolerance . Observatios from several authors [ 3 ] [ 6 ] [ 7 ] [ 8 ] have however suggested that WUE would rather be linked to different drought response strategies, where
Increases in water-use efficiency are commonly cited as a response mechanism of plants to moderate to severe soil water deficits and have been the focus of many programs that seek to increase crop tolerance to drought . [ 9 ] However, there is some question as to the benefit of increased water-use efficiency of plants in agricultural systems , as the processes of increased yield production and decreased water loss due to transpiration (that is, the main driver of increases in water-use efficiency) are fundamentally opposed. [ 10 ] [ 11 ] If there existed a situation where water deficit induced lower transpirational rates without simultaneously decreasing photosynthetic rates and biomass production, then water-use efficiency would be both greatly improved and the desired trait in crop production .
Water-use efficiency is also a much studied trait in Plant ecology , where it has been used already in the early 20th century to study the ecological requirements of Herbaceous plants [ 12 ] or forest trees , [ 13 ] and is still used today, for example related to a drought-induced limitation of tree growth [ 14 ]
This plant physiology article is a stub . You can help Wikipedia by expanding it .
This geochemistry article is a stub . You can help Wikipedia by expanding it .
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https://en.wikipedia.org/wiki/Water-use_efficiency
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Water ( Russian : Вода ), also released as The Great Mystery of Water (Russian: Великая тайна воды ) is a 2006 pseudoscientific documentary television film directed by Anastaysia Popova about the memory of water . The film was part of television channel Rossiya 1 's project The Great Mystery of Water .
In the film, scientists and pseudoscientists from various countries (including Kurt Wüthrich , Masaru Emoto , Rustum Roy , and Konstantin Korotkov) present their work on the theme of water . Additionally, clergy from major religions (including Metropolit of Smolensk Kirill , Shamil Alyautdinov , and Pinchas Polonsky ) discuss the importance of water in their faith . The film also presents experiences of water, including the emotions of humans interacting with the water (using kirlian photography ).
In November 2006 the film won three television awards at TEFI , including for the best documentary film . [ 1 ]
Water faced sharp criticism from the Russian scientific community, which condemned the movie as pseudoscience.
Wüthrich distanced himself from the film, saying that although he was interviewed, his statements were taken out of context. He was not informed that the interview was to be used for a film. He later wrote: "It is much more problematic that the film, by presenting a Nobel Prize winner, suggests to the viewer that the nonsense presented is actually scientific consensus." [ 2 ]
Water includes many pseudoscientific and dubious claims, including:
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This page provides supplementary data to the article properties of water .
Further comprehensive authoritative data can be found at the NIST Chemistry WebBook page on thermophysical properties of fluids. [ 1 ]
88.00 at 0 °C 86.04 at 5 °C 84.11 at 10 °C 82.22 at 15 °C 80.36 at 20 °C 78.54 at 25 °C 76.75 at 30 °C 75.00 at 35 °C 73.28 at 40 °C 71.59 at 45 °C 69.94 at 50 °C 66.74 at 60 °C 63.68 at 70 °C 60.76 at 80 °C 57.98 at 90 °C 55.33 at 100 °C
Vapor pressure formula for steam in equilibrium with liquid water: [ 14 ]
where P is equilibrium vapor pressure in k Pa , and T is temperature in kelvins .
For T = 273 K to 333 K: A = 7.2326; B = 1750.286; C = 38.1.
For T = 333 K to 423 K: A = 7.0917; B = 1668.21; C = 45.1.
Data in the table above is given for water–steam equilibria at various temperatures over the entire temperature range at which liquid water can exist. Pressure of the equilibrium is given in the second column in k Pa . The third column is the heat content of each gram of the liquid phase relative to water at 0 °C. The fourth column is the heat of vaporization of each gram of liquid that changes to vapor. The fifth column is the work P Δ V done by each gram of liquid that changes to vapor. The sixth column is the density of the vapor.
Data obtained from CRC Handbook of Chemistry and Physics 44th ed., p. 2390.
‡ Ice XI triple point is theoretical and has never been obtained
Note: ρ is density, n is refractive index at 589 nm, [ clarification needed ] and η is viscosity, all at 20 °C; T eq is the equilibrium temperature between two phases: ice/liquid solution for T eq < 0–0.1 °C and NaCl/liquid solution for T eq above 0.1 °C.
The data that follows was copied and translated from the German language Wikipedia version of this page (which has moved to here ). It provides supplementary physical, thermodynamic, and vapor pressure data, some of which is redundant with data in the tables above, and some of which is additional.
In the following tables, values are temperature-dependent and to a lesser degree pressure-dependent, and are arranged by state of aggregation (s = solid, lq = liquid, g = gas), which are clearly a function of temperature and pressure. All of the data were computed from data given in "Formulation of the Thermodynamic Properties of Ordinary Water Substance for Scientific and General Use" (IAPWS , 1984) (obsolete as of 1995). [ 22 ] This applies to:
In the following table, material data are given for standard pressure of 0.1 M Pa (equivalent to 1 bar). Up to 99.63 °C (the boiling point of water at 0.1 MPa), at this pressure water exists as a liquid. Above that, it exists as water vapor. Note that the boiling point of 100.0 °C is at a pressure of 0.101325 MPa (1 atm ), which is the average atmospheric pressure.
In the following table, material data are given with a pressure of 611.7 Pa (equivalent to 0.006117 bar). Up to a temperature of 0.01 °C, the triple point of water, water normally exists as ice, except for supercooled water, for which one data point is tabulated here. At the triple point, ice can exist together with both liquid water and vapor. At higher temperatures, the data are for water vapor only.
The following table is based on different, complementary sources and approximation formulas, whose values are of various quality and accuracy. The values in the temperature range of −100 °C to 100 °C were inferred from D. Sunday (1982) and are quite uniform and exact. The values in the temperature range of the boiling point of water up to the critical point (100 °C to 374 °C) are drawn from different sources and are substantially less accurate; hence they should be used only as approximate values. [ 23 ] [ 24 ] [ 25 ] [ 26 ]
To use the values correctly, consider the following points:
The table values for −100 °C to 100 °C were computed by the following formulas, where T is in kelvins and vapor pressures, P w and P i , are in pascals .
Over liquid water
For temperature range: 173.15 K to 373.15 K or equivalently −100 °C to 100 °C
Over ice
For temperature range: 173.15 K to 273.15 K or equivalently −100 °C to 0 °C
At triple point
An important basic value, which is not registered in the table, is the saturated vapor pressure at the triple point of water. The internationally accepted value according to measurements of Guildner, Johnson and Jones (1976) amounts to:
Accepted standardized value of the magnetic susceptibility of water at 20 °C (room temperature) is −12.97 cm 3 /mol. [ 27 ]
Accepted standardized value of the magnetic susceptibility of water at 20 °C (room temperature) is −0.702 cm 3 /g. [ 27 ]
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The Water Environment Federation (WEF) is a not-for-profit technical and educational organization of more than 34,000 individual members and 75 Member Associations (MAs) representing water quality professionals around the world. [ 1 ] WEF, which was formerly known as the Federation of Sewage Works Associations and later as the Water Pollution Control Federation, and originated in 1928. [ 2 ] WEF members include experts and specialists in the fields of:
and related disciplines. [ 3 ]
WEF is headquartered in Alexandria, Virginia , United States . [ 4 ]
In addition to books, technical reports, and conferences proceedings, WEF publishes the peer-reviewed journal, Water Environment Research, and the magazine, Water Environment Technology. WEF sponsors local and national speciality meetings, as well as the world's largest annual water conference: WEFTEC - Water Environment Federation Technical Exposition and Conference. [ 5 ]
To recognize individuals and groups in a number of areas, WEF sponsors awards in the categories of: Published Papers; Operational and Design Excellence; Education; Individual Service and Contribution; Fellows; Organization and Association Recognition; National Municipal Stormwater and Green Infrastructure, as well as Committee Chair Service Appreciation. [ 6 ] [ 7 ]
This article about a professional association is a stub . You can help Wikipedia by expanding it .
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In food science, water activity ( a w ) of a food is the ratio of its vapor pressure to the vapor pressure of water at the same temperature, both taken at equilibrium. [ 1 ] Pure water has a water activity of one. Put another way, a w is the equilibrium relative humidity (ERH) expressed as a fraction instead of as a percentage. As temperature increases, a w typically increases, except in some products with crystalline salt or sugar .
Water migrates from areas of high a w to areas of low a w . For example, if honey ( a w ≈ 0.6) is exposed to humid air ( a w ≈ 0.7), the honey absorbs water from the air . If salami ( a w ≈ 0.87) is exposed to dry air ( a w ≈ 0.5), the salami dries out , which could preserve it or spoil it. Lower a w substances tend to support fewer microorganisms since these get desiccated by the water migration.
Water activity is not simply a function of water concentration in food. The water in food has a tendency to evaporate, but the water vapor in the surrounding air has a tendency to condense into the food. When the two tendencies are in balance— and the air and food are stable—the air's relative humidity (expressed as a fraction instead of as a percentage) is taken to be the water activity, a w . Thus, water activity is the thermodynamic activity of water as solvent and the relative humidity of the surrounding air at equilibrium.
The definition of a w is a w ≡ p p ∗ {\displaystyle a_{w}\equiv {\frac {p}{p^{*}}}} where p is the partial water vapor pressure in equilibrium with the solution , and p* is the (partial) vapor pressure of pure water at the same temperature.
An alternate definition can be a w ≡ l w x w {\displaystyle a_{w}\equiv l_{w}x_{w}} where l w is the activity coefficient of water and x w is the mole fraction of water in the aqueous fraction.
Relationship to relative humidity :
The relative humidity (RH) of air in equilibrium with a sample is also called the Equilibrium Relative Humidity (ERH) and is usually given as a percentage. [ 2 ] It is equal to water activity according to E R H = a w × 100 % . {\displaystyle \mathrm {ERH} =a_{w}\times 100\%.} The estimated mold-free shelf life (MFSL) in days at 21 °C depends on water activity according to [ 3 ] M F S L = 10 7.91 − 8.1 a w {\displaystyle \mathrm {MFSL} =10^{7.91-8.1a_{w}}}
Water activity is an important characteristic for food product design and food safety. [ citation needed ]
Food designers use water activity to formulate shelf-stable food . If a product is kept below a certain water activity, then mold growth is inhibited. This results in a longer shelf life . [ citation needed ]
Water activity values can also help limit moisture migration within a food product made with different ingredients . If raisins of a higher water activity are packaged with bran flakes of a lower water activity, the water from the raisins migrates to the bran flakes over time, making the raisins hard and the bran flakes soggy. Food formulators use water activity to predict how much moisture migration affects their product. [ citation needed ]
Water activity is used in many cases as a critical control point for Hazard Analysis and Critical Control Points (HACCP) programs. Samples of the food product are periodically taken from the production area and tested to ensure water activity values are within a specified range for food quality and safety. Measurements can be made in as little as five minutes, and are made regularly in most major food production facilities. [ citation needed ]
For many years, researchers tried to equate bacterial growth potential with water content . They found that the values were not universal, but specific to each food product. W. J. Scott first established that bacterial growth correlated with water activity, not water content, in 1953. [ 4 ] It is firmly established that growth of bacteria is inhibited at specific water activity values. U.S. Food and Drug Administration (FDA) regulations for intermediate moisture foods are based on these values.
Lowering the water activity of a food product should not be seen as a kill step . Studies in powdered milk show that viable cells can exist at much lower water activity values, but that they never grow. [ citation needed ] Over time, bacterial levels decline.
Water activity values are obtained by either a resistive electrolytic, a capacitance or a dew point hygrometer .
Resistive electrolytic hygrometers use a sensing element in the form of a liquid electrolyte held in between of two small glass rods by capillary force. The electrolyte changes resistance if it absorbs or loses water vapor. The resistance is directly proportional to relative air humidity and therefore also to water activity of the sample (once vapor–liquid equilibrium is established). This relation can be checked by either verification or calibration using saturated salt-water mixtures, which provide a well-defined and reproducible air humidity in the measurement chamber. [ citation needed ]
The sensor does not have any physically given hysteresis as it is known from capacitance hygrometers and sensors, and does not require regular cleaning as its surface is not the effectively sensing element. Volatiles, in principle, influence the measurement performance—especially those that dissociate in the electrolyte and thereby change its resistance. Such influences can easily be avoided by using chemical protection filters that absorb the volatile compound before arriving at the sensor. [ citation needed ]
Capacitance hygrometers consist of two charged plates separated by a polymer membrane dielectric . As the membrane adsorbs water, its ability to hold a charge increases and the capacitance is measured. This value is roughly proportional to the water activity as determined by a sensor-specific calibration . [ citation needed ]
Capacitance hygrometers are not affected by most volatile chemicals and can be much smaller than other alternative sensors. They do not require cleaning, but are less accurate than dew point hygrometers (+/- 0.015 a w ). They should have regular calibration checks and can be affected by residual water in the polymer membrane (hysteresis).
The temperature at which dew forms on a clean surface is directly related to the vapor pressure of the air. Dew point hygrometers work by placing a mirror over a closed sample chamber. The mirror is cooled until the dew point temperature is measured by means of an optical sensor . This temperature is then used to find the relative humidity of the chamber using psychrometrics charts.
This method is theoretically the most accurate (+/- 0.003 a w ) and often the fastest. The sensor requires cleaning if debris accumulates on the mirror.
With either method, vapor–liquid equilibrium must be established in the sample chamber. This takes place over time or can be aided by the addition of a fan in the chamber. Thermal equilibrium must also be achieved unless the sample temperature is measured. [ citation needed ]
Water activity is related to water content in a non-linear relationship known as a moisture sorption isotherm curve. These isotherms are substance- and temperature-specific. Isotherms can be used to help predict product stability over time in different storage conditions. [ citation needed ]
There is net evaporation from a solution with a water activity greater than the relative humidity of its surroundings. There is net absorption of water by a solution with a water activity less than the relative humidity of its surroundings. Therefore, in an enclosed space, an aqueous solution can be used to regulate humidity. [ 5 ]
Water is necessary for life under all its forms presently known on Earth . Without water, microbial activity is not possible. Even if some micro-organisms can be preserved in the dry state (e.g., after freeze-drying ), their growth is not possible without water. [ citation needed ]
Micro-organisms also require sufficient space to develop. In highly compacted bentonite and deep clay formations, microbial activity is limited by the lack of space and the transport of nutrients towards bacteria and the elimination of toxins produced by their metabolism is controlled by diffusion in the pore water. So, "space and water restrictions" are two limiting factors of the microbial activity in deep sediments. [ 13 ] Early biotic diagenesis of sediments just below the ocean floor driven by microbial activity (e.g., of sulfate reducing bacteria ) end up when the degree of compaction becomes too important to allow microbial life development. [ 14 ]
At the surface of planets and in their atmosphere, space restrictions do not apply, therefore, the ultimate limiting factor is water availability and thus the water activity. [ citation needed ]
Most extremophile micro-organisms require sufficient water to be active. The threshold of water activity for their development is around 0.6. The same rule should also apply for other planets than Earth. After the tantalizing detection of phosphine (PH 3 ) in the atmosphere of Venus , in the absence of known and plausible chemical mechanism to explain the formation of this molecule, the presence of micro-organisms in suspension in Venus's atmosphere has been suspected and the hypothesis of the microbial formation of phosphine has been formulated by Greaves et al. (2020) from Cardiff University envisaging the possibility of a liveable window in the Venusian clouds at a certain altitude with an acceptable temperature range for microbial life. [ 15 ]
Hallsworth et al. (2021) from the School of Biological Sciences at Queen's University Belfast have studied the conditions required to support the life of extremophile micro-organisms in the clouds at high altitude in the Venus atmosphere where favorable temperature conditions might prevail. Beside the presence of sulfuric acid in the clouds which already represent a major challenge for the survival of most micro-organisms, they came to the conclusion that the atmosphere of Venus is much too dry to host microbial life. Indeed, Hallsworth et al. (2021) have determined a water activity of ≤ 0.004, two orders of magnitude below the 0.585 limit for known extremophiles. [ 16 ] So, with a water activity in the Venus clouds 100 times lower than the threshold of 0.6 known in Earth conditions, the hypothesis envisaged by Greaves et al. (2020) to explain the biotic origin of phosphine in the Venus atmosphere is ruled out. [ citation needed ]
Direct measurements of the Venusian atmosphere by spatial probes point to very harsh conditions, likely making Venus an uninhabitable world, even for the most extreme forms of life known on Earth. The extremely low water activity of the desiccated Venusian atmosphere represents the very limiting factor for life, much more severe than the infernal conditions of temperature and pressure, or the presence of sulfuric acid.
Astrobiologists presently consider that more favorable conditions could be encountered in the clouds of Jupiter where a sufficient water activity could prevail in the atmosphere provided that other conditions necessary for life are also met in the same environment (sufficient supply of nutrients and energy in a non-toxic medium). [ 17 ] [ 18 ]
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The water associated fraction ( WAF ), sometimes termed the water-soluble fraction ( W.S.F. ), is the solution of low molecular mass hydrocarbons naturally released from petroleum hydrocarbon mixtures in contact with water . Although generally regarded as hydrophobic , many petroleum hydrocarbons are soluble in water to a limited extent. This combination often also contains less soluble, higher molecular mass components, and more soluble products of chemical and biological degradation . [ 1 ]
Low molecular mass compounds account for much of the toxic nature of hydrocarbon spills . In particular, benzene , toluene , ethyl benzene and the xylenes ( BTEX ) are of great environmental interest due to their availability to organisms . This availability, also influenced by volatility and reactivity , impacts on biodegradation and bioremediation in water and soil environments, with even dissolved components within pore water considered bioavailable . [ 2 ]
The WAF is found in greatest concentration in close proximity to the bulk phase of hydrocarbons, the progress of which is often limited by physical containment measures such as booms . The dissolved components of petroleum mixtures such as crude oil can become subject to the transport mechanisms of the bulk aqueous phase. [ 3 ] [ 4 ] [ 5 ] Source identification of these can therefore become problematic without the visual indications usually expected with petroleum hydrocarbon spills. However, after relatively short periods of exposure, the chemical profile of the original oils is still largely intact, allowing chemical analysis to provide identification and discriminate between different petroleum sources. [ 6 ]
In freshwater aquatic environments, dissolution is the greatest physical weathering process after evaporation . [ 7 ] Under the same conditions, the rate of dissolution is between 0.01% and 1% of the rate of evaporation for alkanes and aromatic compounds . [ 8 ] Once dissolved, these components are more available to organisms and therefore susceptible to biodegradation processes and experience increased rates of photochemical and chemical degradation. [ 9 ] These components represent some of the most toxic oil ingredients because of their increased bioavailability, with reduction in toxicity occurring on emulsification or absorption to colloids which restrict availability to organisms. [ 10 ] [ 11 ] [ 12 ]
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The law of water balance states that the inflows to any water system or area is equal to its outflows plus change in storage during a time interval. [ 2 ] [ 3 ] In hydrology , a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological or water domains, such as a column of soil , a drainage basin , an irrigation area or a city.
The water balance is also referred to as a water budget . Developing water budgets is a fundamental activity in the science of hydrology. According to the US Geological Survey: [ 4 ]
An understanding of water budgets and underlying hydrologic processes provides a foundation for effective water-resource and environmental planning and management. Observed changes in water budgets of an area over time can be used to assess the effects of climate variability and human activities on water resources. Comparison of water budgets from different areas allows the effects of factors such as geology, soils, vegetation, and land use on the hydrologic cycle to be quantified.
A general water balance equation is: [ 5 ]
where
This equation uses the principles of conservation of mass in a closed system, whereby any water entering a system (via precipitation), must be transferred into either evaporation, transpiration, surface runoff (eventually reaching the channel and leaving in the form of river discharge), or stored in the ground. This equation requires the system to be closed, and where it is not (for example when surface runoff contributes to a different basin), this must be taken into account.
Extensive water balances are discussed in agricultural hydrology .
A water balance can be used to help manage water supply and predict where there may be water shortages. It is also used in irrigation , runoff assessment (e.g. through the RainOff model [ 6 ] ), flood control and pollution control . Further it is used in the design of subsurface drainage systems which may be horizontal (i.e. using pipes, tile drains or ditches) or vertical ( drainage by wells ). [ 7 ] To estimate the drainage requirement, the use of a hydrogeological water balance and a groundwater model (e.g. SahysMod [ 8 ] ) may be instrumental.
The water balance can be illustrated using a water balance graph which plots levels of precipitation and evapotranspiration often on a monthly scale.
Several monthly water balance models had been developed for several conditions and purposes. Monthly water balance models had been studied since the 1940s. [ 9 ]
“Making water available for its many uses and users requires tools and institutions to transform it from a natural resource to one providing services”. [ 10 ] This means that there are two types of water systems: Water Resource System (WRS) and Water Use System (WUS).
A WRS, such as a river, an aquifer or a lake, must obey water balance. For example, the volume of water that goes into an aquifer must be equal to the amount that leaves it plus its change in storage. Under various drivers, such as, climate change , population increase, and bad management, water storage of many WRS is decreasing, say per decade. This means that the volume of water in a WRS decreased after a decade, i.e., inflow was less than outflow during that time interval. [ 11 ]
In general, a WUS is a water construct of a user, such as a city, an industry, an irrigation zone, or a region, and not a geographic area. The schematic of a WUS shows the inflows and the outflows. For a WUS, change in storage is negligible (relative to its inflow) under a proper time interval, hence water balance becomes inflow equal to outflow with nine Water Path Types (WPT): [ 12 ]
V A + O S + P P = E T + N R + R F + R P {\displaystyle VA+OS+PP=ET+NR+RF+RP}
Of course, instead of a river, it could be an aquifer that supplies water to a WUS as a main source. Let us briefly examine an urban water supply on an annual basis as a simplified example. It has negligible ET and PP (WUS is a piped network), has some limited amount of water from groundwater (OS), has return flow to the main source (RF) after passing through a Wastewater Treatment Plant, and RP type has various Water Path Instances (WPI), such as leakage, and water taken to irrigate green zones. Considering that the annual change in storage of an urban area is negligible, water balance equation becomes
V A r i v + O S g w = N R + R F w w t p + R P l e a k + R P i r r {\displaystyle VA_{riv}+OS_{gw}=NR+RF_{wwtp}+RP_{leak}+RP_{irr}}
Several diagnostic measures in hydrology can be used to select and evaluate the performance of water balance models.
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A water block is the watercooling equivalent of a heatsink . It is a type of plate heat exchanger and can be used on many different computer components, [ 1 ] : 186 including the central processing unit (CPU), GPU , PPU , and northbridge chipset on the motherboard. There are also Monoblocks on the market that are mounted on PC motherboards and cover the CPU and its power delivery VRMs (Voltage Regulator Modules) that surround the CPU socket area. It consists of at least two main parts; the "base", which is the area that makes contact with the device being cooled and is usually manufactured from metals with high thermal conductivity such as aluminum or copper . The second part, the "top" ensures the water is contained safely inside the water block and has connections that allow hosing to connect it with the water cooling loop. The top can be made of the same metal as the base, transparent Perspex , Delrin , Nylon , or HDPE . Most newer high-end water blocks also contain mid-plates which serve to add jet tubes, nozzles, and other flow altering devices.
The base, top, and mid-plate(s) are sealed together to form a "block" with some sort of path for water to flow through. The ends of the path have inlet/outlet connectors for the tubing that connects it to the rest of the watercooling system. Early designs included spiral , zig-zag pattern or heatsink like fins to allow the largest possible surface area for heat to transfer from the device being cooled to the water. These designs generally were used because the conjecture was that maximum flow was required for high performance. Trial and error and the evolution of water block design has shown that trading flow for turbulence can often improve performance. The Storm series of water blocks is an example of this. Its jet tube mid plate and cupped base design makes it more restrictive to the flow of water than early maze designs but the increased turbulence results in a large increase in performance. Newer designs include "pin" style blocks, "jet cup" blocks, further refined maze designs, micro-fin designs, and variations on these designs. Increasingly restrictive designs have only been possible because of increases in maximum head pressure of commercially viable water pumps .
A water block is better at dissipating heat than an air-cooled heatsink due to water's higher specific heat capacity and thermal conductivity . The water is usually pumped through to a radiator which allows a fan pushing air through it to take the heat created from the device and expel it into the air. A radiator is more efficient than a standard CPU or GPU heatsink/air cooler at removing heat because it has a much larger surface area.
Installation of a water block is also similar to that of a heatsink, with a thermal pad or thermal grease placed between it and the device being cooled to aid in heat conduction . [ clarification needed ]
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Water cascade analysis ( WCA ) is a technique to calculate the minimum flowrate target for feedwater and wastewater for continuous water-using processes. [ 1 ]
It is a tabular and numerical alternative to the water surplus diagram in Water Pinch which can be used to identify opportunities for reduction in feedwater usage and the design of water distribution networks. The WCA is done in three steps, a global analysis of water distribution and consumption in the network, establishing baseline minimum water targets and redesign of the water network to achieve these targets.
WCA was first introduced by Manan, Tan and Foo in 2004. [ 2 ] Since then, it has been widely used as a tool for water conservation in industrial process plants. A Time dependent water cascade analysis was presented later on. [ 3 ] A variation of the WCA is the gas cascade analysis (GCA). [ 4 ]
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A water chiller [ 1 ] is a device used to lower the temperature of water. Most chillers use refrigerant in a closed loop system to facilitate heat exchange from water where the refrigerant is then pumped to a location where the waste heat is transferred to the atmosphere . However, there are other methods in performing this action.
In hydroponics , pumps, lights and ambient heat can warm the reservoir water temperatures, leading to plant root and health problems. For ideal plant health, a chiller can be used to lower the water temperature below ambient level; 68 °F (20 °C) is a good temperature for most plants. This results in healthy root production and efficient absorption of nutrients.
In air conditioning , chilled water is often used to cool a building's air and equipment, especially in situations where many individual rooms must be controlled separately, such as a hotel. A chiller lowers water temperature to between 40 °F (4 °C) and 45 °F (7 °C) before the water is pumped to the location to be cooled. [ 2 ]
This article about a mechanical engineering topic is a stub . You can help Wikipedia by expanding it .
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Water chlorination is the process of adding chlorine or chlorine compounds such as sodium hypochlorite to water . This method is used to kill bacteria, viruses and other microbes in water. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera , dysentery , and typhoid . [ 1 ] [ 2 ] [ 3 ]
In a paper published in 1894, it was formally proposed to add chlorine to water to render it "germ-free". Two other authorities endorsed this proposal and published it in many other papers in 1895. [ 4 ] Early attempts at implementing water chlorination at a water treatment plant were made in 1893 in Hamburg , Germany. In 1897 the town of Maidstone , England was the first to have its entire water supply treated with chlorine. [ 5 ]
Permanent water chlorination began in 1905, when a faulty slow sand filter and a contaminated water supply caused a serious typhoid fever epidemic in Lincoln , England. [ 6 ] Alexander Cruickshank Houston used chlorination of the water to stop the epidemic. His installation fed a concentrated solution of so-called "chlorinated lime" (a mixture of calcium hypochlorite , calcium hydroxide and calcium chloride ) to the water being treated. This was not simply modern calcium chloride, but contained chlorine gas dissolved in lime-water (dilute calcium hydroxide) to form calcium hypochlorite (chlorinated lime). The chlorination of the water supply helped stop the epidemic and as a precaution, the chlorination was continued until 1911 when a new water supply was commissioned. [ 7 ]
The first continuous use of chlorine in the United States for disinfection took place in 1908 at Boonton Reservoir (on the Rockaway River ), which served as the supply for Jersey City, New Jersey . [ 8 ] Chlorination was achieved by controlled additions of dilute solutions of chloride of lime ( calcium hypochlorite ) at doses of 0.2 to 0.35 ppm. The treatment process was conceived by John L. Leal , and the chlorination plant was designed by George Warren Fuller. [ 9 ] Over the next few years, chlorine disinfection using chloride of lime (calcium hypochlorite) was rapidly implemented in drinking water systems around the world. [ 10 ]
The technique of purification of drinking water by use of compressed liquefied chlorine gas was developed by a British officer in the Indian Medical Service , Vincent B. Nesfield, in 1903. According to his own account, "It occurred to me that chlorine gas might be found satisfactory ... if suitable means could be found for using it.... The next important question was how to render the gas portable. This might be accomplished in two ways: by liquefying it, and storing it in lead-lined iron vessels, having a jet with a very fine capillary canal, and fitted with a tap or a screw cap. The tap is turned on, and the cylinder placed in the amount of water required. The chlorine bubbles out, and in ten to fifteen minutes the water is absolutely safe. This method would be of use on a large scale, as for service water carts." [ 11 ]
Major Carl Rogers Darnall , Professor of Chemistry at the Army Medical School , gave the first practical demonstration of this in 1910. [ 12 ] This work became the basis for present day systems of municipal water purification . Shortly after Darnall's demonstration, Major William J. L. Lyster of the Army Medical Department used a solution of calcium hypochlorite in a linen bag to treat water. [ citation needed ]
For many decades, Lyster's method remained the standard for U.S. ground forces in the field and in camps, implemented in the form of the familiar Lyster Bag (also spelled Lister Bag). The canvas "bag, water, sterilizing" was a common component of field kitchens, issued one per 100 persons, of a standard 36-gallon capacity that hung from an often-improvised tripod in the field. In use from World War I through the Vietnam War, it has been replaced by reverse osmosis systems that produce potable water by pressure straining local water through microscopic-level filters: the Reverse Osmosis Water Purification Unit (1980) and the Tactical Water Purification System (2007) for large-scale production, and the Light Water Purifier unit for smaller-scale needs that includes ultrafiltration technology to produce potable water from any source and uses automated backwash cycles every 15 minutes to simplify cleaning operations. [ citation needed ]
Chlorine gas was first used on a continuing basis to disinfect the water supply at the Belmont filter plant, Philadelphia , Pennsylvania by using a machine invented by Charles Frederick Wallace [ citation needed ] who dubbed it the Chlorinator. It was manufactured by the Wallace & Tiernan company beginning in 1913. [ 13 ] By 1941, disinfection of U.S. drinking water by chlorine gas had largely replaced the use of chloride of lime. [ 14 ] [ 15 ]
As a halogen , chlorine is a highly efficient disinfectant, and is added to public water supplies to kill disease-causing pathogens, such as bacteria , viruses , and protozoans , that commonly grow in water supply reservoirs, on the walls of water mains and in storage tanks. [ 16 ] The microscopic agents of many diseases such as cholera , typhoid fever , and dysentery killed countless people annually before disinfection methods were employed routinely. [ 16 ]
By far most chlorine is manufactured from table salt (NaCl) by electrolysis in the chlor-alkali process. The resulting gas at atmospheric pressures is liquified at high pressure. The liquefied gas is transported and used as such. [ citation needed ]
As a strong oxidizing agent , chlorine kills via the oxidation of organic molecules. [ 16 ] Chlorine and the hydrolysis product hypochlorous acid are not charged and therefore easily penetrate the negatively charged surface of pathogens. It is able to disintegrate the lipids that compose the cell wall and react with intracellular enzymes and proteins , making them nonfunctional. Microorganisms then either die or are no longer able to multiply. [ 17 ]
When dissolved in water, chlorine converts to an equilibrium mixture of chlorine, hypochlorous acid (HOCl), and hydrochloric acid (HCl):
In acidic solution, the major species are Cl 2 and HOCl, whereas in alkaline solution, effectively only ClO − ( hypochlorite ion) is present. Very small concentrations of ClO 2 − , ClO 3 − , ClO 4 − are also found. [ 18 ]
Shock chlorination is a process used in many swimming pools, water wells , springs , and other water sources to reduce the bacterial and algal residue in the water. Shock chlorination is performed by mixing a large amount of hypochlorite into the water. The hypochlorite can be in the form of a powder or a liquid such as chlorine bleach (solution of sodium hypochlorite or calcium hypochlorite in water). Water that is being shock chlorinated should not be swum in or drunk until the sodium hypochlorite count in the water goes down to three parts per million (ppm) or until the calcium hypochlorite count goes down to 0.2 to 0.35 ppm. [ citation needed ]
As an alternative to shock chlorination, some swimming pools are chlorinated by use of a chlorine-generating filter that electrolyzes common salt . Pools chlorinated by this method generally have lower levels of chlorine than directly chlorinated pools. Such pools are called saltwater pools. [ citation needed ]
Disinfection by chlorination can be problematic in some circumstances. Chlorine can react with naturally occurring organic compounds found in the water supply to produce compounds known as disinfection by-products (DBPs). The most common DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs). Trihalomethanes are the primary disinfection by-products created from chlorination. In high doses, bromoform mainly slows down regular brain activity, which is manifested by symptoms such as sleepiness or sedation. Chronic exposure to both bromoform and dibromochloromethane can cause liver and kidney cancer, as well as heart disease, unconsciousness, or death in high doses. [ 19 ] Due to the potential carcinogenicity of these compounds, drinking water regulations across the developed world require regular monitoring of the concentration of these compounds in the distribution systems of municipal water systems. The World Health Organization has stated that "the risks to health from these by-products are extremely small in comparison with the risks associated with inadequate disinfection". [ 2 ]
There are also other concerns regarding chlorine, including its volatile nature which causes it to disappear too quickly from the water system, and organoleptic concerns such as taste and odor. [ citation needed ]
A dechlorinator is a chemical additive that removes chlorine or chloramine from water. Where tap water is chlorinated, it should be dechlorinated before use in an aquarium , since chlorine can harm aquatic life in the same way it kills micro-organisms . Chlorine will kill fish [ 20 ] and cause damage to an aquarium's biological filter . [ 21 ] Chemicals that serve this function are reducing agents which reduce chlorine species to chloride , which is harmless to life.
Some compounds employed in commercial dechlorinators are sodium thiosulfate , sodium hydroxymethanesulfonate, and sodium hydroxymethane sulfinic acid. [ 22 ]
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Water clarity is a descriptive term for how deeply visible light penetrates through water. In addition to light penetration, the term water clarity is also often used to describe underwater visibility. Water clarity is one way that humans measure water quality , along with oxygen concentration and the presence or absence of pollutants and algal blooms. [ 1 ]
Water clarity governs the health of underwater ecosystems because it impacts the amount of light reaching the plants and animals living underwater. For plants, light is needed for photosynthesis. The clarity of the underwater environment determines the depth ranges where aquatic plants can live. [ 2 ] [ 3 ] [ 4 ] [ 5 ] Water clarity also impacts how well visual animals like fish can see their prey. [ 6 ] [ 7 ] [ 8 ] [ 9 ] Clarity affects the aquatic plants and animals living in all kinds of water bodies, including rivers, ponds, lakes, reservoirs, estuaries, coastal lagoons, and the open ocean.
Water clarity also affects how humans interact with water, from recreation and property values to mapping, defense, and security. Water clarity influences human perceptions of water quality, recreational safety, aesthetic appeal, and overall environmental health. [ 10 ] [ 11 ] Tourists visiting the Great Barrier Reef were willing to pay to improve the water clarity conditions for recreational satisfaction. [ 12 ] Water clarity also influences waterfront property values. In the United States, a 1% improvement in water clarity increased property values by up to 10%. [ 13 ] [ 14 ] [ 15 ] [ 16 ] Water clarity is needed to visualize targets underwater, either from above or in water. These applications include mapping and military operations. To map shallow-water features such as oyster reefs and seagrass beds, the water must be clear enough for those features to be visible to a drone, airplane, or satellite. [ 17 ] [ 18 ] Water clarity is also needed to detect underwater objects such as submarines using visible light. [ 19 ] [ 20 ] [ 21 ]
Water clarity is measured using multiple techniques. These measurements include: Secchi depth , light attenuation, turbidity , beam attenuation, absorption by colored dissolved organic matter , the concentration of chlorophyll-a pigment, and the concentration of total suspended solids . Clear water generally has a deep Secchi depth, low light attenuation (deeper light penetration), low turbidity, low beam attenuation, and low concentrations of dissolved substances, chlorophyll-a, and/or total suspended solids. More turbid water generally has a shallow Secchi depth, high light attenuation (less light penetration to depth), high turbidity, high beam attenuation, and high concentrations of dissolved substances, chlorophyll-a, and/or total suspended solids. [ 22 ]
Secchi depth is the depth at which a disk is no longer visible to the human eye. This measurement was created in 1865 and represents one of the oldest oceanographic methods. [ 23 ] [ 24 ] To measure Secchi depth, a white or black-and-white disk is mounted on a pole or line and lowered slowly down in the water. The depth at which the disk is no longer visible is taken as a measure of the transparency of the water. [ 25 ] [ 26 ] Secchi depth is most useful as a measure of transparency or underwater visibility.
The light attenuation coefficient – often shortened to "light attenuation" – describes the decrease in solar irradiance with depth. To calculate this coefficient, light energy is measured at a series of depths from the surface to the depth of 1% illumination. Then, the exponential decline in light is calculated using Beer’s Law with the equation:
I z I 0 = e − k z {\displaystyle {I_{z} \over I_{0}}=e^{-kz}}
where k is the light attenuation coefficient, I z is the intensity of light at depth z , and I 0 is the intensity of light at the ocean surface. [ 27 ] [ 28 ] Which translates to:
k = l n I z I 0 − z {\displaystyle k={ln{I_{z} \over I_{0}} \over -z}}
This measurement can be done for specific colors of light or more broadly for all visible light. The light attenuation coefficient of photosynthetically active radiation (PAR) refers to the decrease in all visible light (400–700 nm) with depth. Light attenuation can be measured as the decrease in downwelling light (Kd) or the decrease in scalar light (Ko) with depth. [ 29 ] [ 30 ] [ 31 ] Light attenuation is most useful as a measure of the total underwater light energy available to plants, such as phytoplankton and submerged aquatic vegetation .
Turbidity is a measure of the cloudiness of water based on light scattering by particles at a 90-degree angle to the detector. A turbidity sensor is placed in water with a light source and a detector at a 90-degree angle to one another. The light source is usually red or near-infrared light (600–900 nm). Turbidity sensors are also called turbidimeters or nephelometers . In more turbid water, more particles are present in the water, and more light scattering by particles is picked up by the detector. Turbidity is most useful for long-term monitoring because these sensors are often low cost and sturdy enough for long deployments underwater. [ 32 ] [ 33 ] [ 34 ] [ 35 ]
Beam attenuation is measured with a device called a transmissometer that has a light source at one end and a detector at the other end, in one plane. The amount of light transmitted to the detector through the water is the beam transmission, and the amount of light lost is the beam attenuation. Beam attenuation is essentially the opposite of light transmission. Clearer water with a low beam attenuation coefficient will have high light transmission, and more turbid water with a high beam attenuation coefficient will have low light transmission. Beam attenuation is used as a proxy for particulate organic carbon in oligotrophic waters like the open ocean. [ 36 ]
Colored dissolved organic matter (CDOM) absorbs light, making the water appear darker or tea-colored. Absorption by CDOM is one measure of water clarity. Clarity can still be quite high in terms of visibility with high amounts of CDOM in the water, but the color of the water will be altered to yellow or brown, and the water will appear darker than water with low CDOM concentrations. CDOM absorbs blue light more strongly than other colors, shifting the color of the water toward the yellow and red part of the visible light spectrum as the water gets darker. [ 37 ] For example, in lakes with high CDOM concentrations, the bottom of the lake may be clearly visible to the human eye, but a white surface in the same lake water may appear yellow or brown.
Total suspended solids (TSS) concentration is the concentration (dry weight mass per unit volume of water) of all the material in water that is caught on a filter, usually a filter with about a 0.7 micrometer pore size. This includes all the particles suspended in water, such as mineral particles (silt, clay), organic detritus, and phytoplankton cells. Clear water bodies have low TSS concentrations. Other names for TSS include total suspended matter (TSM) and suspended particulate matter (SPM). The term suspended sediment concentration (SSC) refers to the mineral component of TSS but is sometimes used interchangeably with TSS. If desired, the concentrations of volatile (organic) and fixed (inorganic) suspended solids can be separated out using the loss-on-ignition method by burning the filter in a muffle furnace to burn off organic matter, leaving behind ash including mineral particles and inorganic components of phytoplankton cells, with TSS = volatile suspended solids + fixed suspended solids. [ 38 ]
Chlorophyll-a concentration is sometimes used to measure water clarity, especially when suspended sediments and colored dissolved organic matter concentrations are low. Chlorophyll-a concentration is a proxy for phytoplankton biomass, which is one way to quantify how turbid the water is due to biological primary production . [ 39 ] Chlorophyll-a concentration is most useful for research on primary production, the contribution of phytoplankton to light attenuation, and harmful algal blooms . Chlorophyll-a concentration is also useful for long-term monitoring because these sensors are often low cost and sturdy enough for long deployments underwater.
The clearest waters occur in oligotrophic ocean regions such as the South Pacific Gyre , tropical coastal waters, glacially-formed lakes with low sediment inputs, and lakes with some kind of natural filtration occurring at the inflow point. Blue Lake in New Zealand holds the record for the highest water clarity of any lake, with a Secchi depth of 230 to 260 feet. Blue Lake is fed by an underground passage from a nearby lake, which acts as a natural filter. [ 40 ] Some other very clear water bodies are Lake Tahoe between California and Nevada in the United States, [ 41 ] Lake Baikal in Russia, [ 42 ] and Crater Lake in Oregon in the United States. [ 43 ]
In tropical coastal waters, the water is clear thanks to low nutrient inputs, low primary production, and coral reefs acting as a natural buffer that keep sediments from getting resuspended. [ 44 ] The clearest recorded water on Earth is either Blue Lake, New Zealand or the Weddell Sea near Antarctica, both of which claim Secchi depths of 80 meters (230 to 260 feet). [ 43 ] [ 40 ]
Very low water clarity can be found where high loads of suspended sediments are transported from land. Some examples are estuaries where rivers with high loads of sediments empty into the ocean. One example is the Río de la Plata , an estuary in South America between Uruguay and Argentina where the Uruguay River and the Parana River empty into the Atlantic ocean. The Río de la Plata shows long-term mean TSS concentrations between 20 and 100 grams per cubic meter, higher than most estuaries. [ 45 ] Another example is the gulf coast of North America where the Mississippi River meets the Gulf of Mexico . Turbid water from snowmelt and rain washes high loads of sediment downstream each spring, creating a sediment plume and making the water clarity very low. [ 46 ] Water bodies can also experience low water clarity after extreme events like volcanic eruptions. After the eruption of Mount St. Helens , the water of Spirit Lake , Washington was darkened by decaying trees in the lake and had a Secchi depth of only 1 to 2 centimeters. [ 43 ]
Water clarity is more specific than water quality . The term "water clarity" more strictly describes the amount of light that passes through water or an object’s visibility in water. The term "water quality" more broadly refers to many characteristics of water, including temperature , dissolved oxygen , the amount of nutrients , or the presence of algal blooms . How clear the water appears is only one component of water quality. [ 1 ] [ 5 ] [ 47 ]
An underwater ecosystem can have high water clarity yet low water quality, and vice versa. Scientists have observed that many lakes are becoming less clear while also recovering from acid rain . This phenomenon has been seen in the northeastern United States and northern Europe. In the past, some lakes were ecologically bare, yet clear, while acidity was high. In recent years, as acidity is reduced and watersheds become more forested, many lakes are less clear but also ecologically healthier with higher concentrations of dissolved organic carbon and more natural water chemistry. [ 48 ] [ 49 ] [ 50 ]
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In chemistry , a water cluster is a discrete hydrogen bonded assembly or cluster of molecules of water . [ 1 ] [ 2 ] Many such clusters have been predicted by theoretical models ( in silico ), and some have been detected experimentally in various contexts such as ice , bulk liquid water, in the gas phase , in dilute mixtures with non-polar solvents , and as water of hydration in crystal lattices . The simplest example is the water dimer (H 2 O) 2 .
Water clusters have been proposed as an explanation for some anomalous properties of liquid water , such as its unusual variation of density with temperature. Water clusters are also implicated in the stabilization of certain supramolecular structures. [ 3 ] They are expected to play a role also in the hydration of molecules and ions dissolved in water. [ 4 ] [ 5 ]
Detailed water models predict the occurrence of water clusters, as configurations of water molecules whose total energy is a local minimum. [ 6 ] [ 7 ] [ 8 ]
Of particular interest are the cyclic clusters (H 2 O) n ; these have been predicted to exist for n = 3 to 60. [ 9 ] [ 10 ] [ 11 ] At low temperatures, nearly 50% of water molecules are included in clusters. [ 12 ] With increasing cluster size the oxygen to oxygen distance is found to decrease which is attributed to so-called cooperative many-body interactions: due to a change in charge distribution the H-acceptor molecule becomes a better H-donor molecule with each expansion of the water assembly. Many isomeric forms seem to exist for the hexamer (H 2 O) 6 : from ring, book, bag, cage, to prism shape with nearly identical energy. Two cage-like isomers exist for heptamers (H 2 O) 7 , and octamers (H 2 O) 8 are found either cyclic or in the shape of a cube.
Other theoretical studies predict clusters with more complex three-dimensional structures. [ 13 ] Examples include the fullerene -like cluster (H 2 O) 28 , named the water buckyball , and the 280-water-molecule monster icosahedral network (with each water molecule coordinate to 4 others). The latter, which is 3 nm in diameter, consists of nested icosahedral shells with 280 and 100 molecules. [ 14 ] [ 15 ] There is also an augmented version with another shell of 320 molecules. There is increased stability with the addition of each shell. [ 16 ] There are theoretical models of water clusters of more than 700 water molecules, [ 17 ] [ 18 ] but they have not been observed experimentally. One line of research uses graph invariants for generating hydrogen bond topologies and predicting physical properties of water clusters and ice. The utility of graph invariants was shown in a study considering the (H 2 O) 6 cage and (H 2 O) 20 dodecahedron, which are associated with roughly the same oxygen atom arrangements as in the solid and liquid phases of water. [ 19 ]
Experimental study of any supramolecular structures in bulk water is difficult because of their short lifetime: the hydrogen bonds are continually breaking and reforming at timescales faster than 200 femtoseconds. [ 20 ]
Nevertheless, water clusters have been observed in the gas phase and in dilute mixtures of water and non-polar solvents like benzene and liquid helium . [ 21 ] [ 22 ] The experimental detection and characterization of the clusters has been achieved by spectroscopy - far-infrared (FIR) [ 23 ] and vibration-rotation-tunneling (VRT) [ 24 ] - and by H- NMR [ 25 ] [ 26 ] and neutron diffraction . [ 27 ] The hexamer is found to have planar geometry in liquid helium, a chair conformation in organic solvents, and a cage structure in the gas phase. Experiments combining IR spectroscopy with mass spectrometry reveal cubic configurations for clusters in the range n=(8-10).
When the water is part of a crystal structure as in a hydrate , x-ray diffraction can be used. Conformation of a water heptamer was determined (cyclic twisted nonplanar) using this method. [ 28 ] [ 29 ] Further, multi-layered water clusters with formulae (H 2 O) 100 trapped inside cavities of several polyoxometalate clusters were also reported by Mueller et al. [ 30 ] [ 31 ]
Several models attempt to account for the bulk properties of water by assuming that they are dominated by cluster formation within the liquid. [ 32 ] According to the quantum cluster equilibrium (QCE) theory of liquids, n=8 clusters dominate the liquid water bulk phase, followed by n=5 and n=6 clusters. Near the triple point , the presence of an n=24 cluster is invoked. [ 33 ] In another model, bulk water is built up from a mixture of hexamer and pentamer rings containing cavities capable of enclosing small solutes. In yet another model an equilibrium exists between a cubic water octamer and two cyclic tetramers. [ 34 ] However, none of these models yet have reproduced the experimentally-observed density maximum of water as a function of temperature.
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The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity , light penetration) and chemical ( pH , dissolved oxygen , nutrient salts) characteristics of seawater at different depths for a defined geographical point. Generally, vertical profiles are made of temperature, salinity, chemical parameters at a defined point along the water column. [ 1 ] The water column is the largest, yet one of the most under-explored, habitats on the planet; it is explored to better understand the ocean as a whole, including the huge biomass that lives there and its importance to the global carbon and other biogeochemical cycles. [ 2 ] Studying the water column also provides understanding on the links between living organisms and environmental parameters, large-scale water circulation and the transfer of matter between water masses. [ 1 ]
Water columns are used chiefly for environmental studies evaluating the stratification or mixing of thermal or chemically stratified layers in a lake, stream or ocean. Some of the common parameters analyzed in the water column are pH , turbidity , temperature , hydrostatic pressure , salinity , total dissolved solids , various pesticides , pathogens and a wide variety of chemicals and biota .
Descriptively, the deep sea water column is divided into five parts— pelagic zones (from Greek πέλαγος (pélagos), 'open sea')—from the surface to below the floor.
The term water column is also commonly used in scuba diving to describe the vertical space through which divers ascend and descend.
The pelagic zones are as follows:
The epipelagic zone, otherwise known as the sunlit zone or the euphotic zone, goes to a depth of about 200 meters (656 feet). It is the depth of water to which sunlight is able to penetrate. Although it is only 2 to 3 percent of the entire ocean, the epipelagic zone is home to a massive number of organisms. [ 3 ] Among other organisms, the photic zone is home to vital communities of phytoplankton, zooplankton, and algae. [ 4 ] These primary producers become the food source for hundreds of other organisms such as sharks, stingrays, tuna, and sea turtles. [ 5 ] The epipelagic zone is incredibly important due to its productivity and ability to help remove carbon dioxide from the atmosphere. [ 3 ]
The mesopelagic zone is a layer of the oceanic zone lying beneath the epipelagic zone and above the bathypelagic zone , at depths generally between 200 and 1,000 m (656 and 3,280 ft). The mesopelagic zone receives very little sunlight and is home to many bioluminescent organisms. Because food is scarce in this region, most mesopelagic organisms migrate to the surface to feed at night or live off the falling detritus from the epipelagic ecosystem. [ 6 ]
The bathypelagic zone extends from about 1000 to 4000 meters below the surface. The bathypelagic zone receives no sunlight and water pressure is considerable. The abundance and diversity of marine life decreases with depth through this and the lower zones. [ 7 ]
The abyssopelagic zone is the portion of the ocean deeper than about 4,000 m (13,000 feet) and shallower than about 6,000 m (20,000 feet). The zone is defined mainly by its extremely uniform environmental conditions, as reflected in the distinct life forms inhabiting it. [ 8 ] The abyss is largely unexplored, but it is known to contain animals found nowhere else on earth. It is also abundant in minerals frequently used in manufacturing. The bottom at these depths accounts for about one-third of the planet's seafloor. The sheer size of this area, coupled with the challenges of descending to depths where water pressure can reach 600 atmospheres, makes exploration difficult—but by no means impossible. [ 9 ]
The hadopelagic ( or hadal) zone, refers to depths below 6000 meters, which occur mostly in the deep ocean trenches. The term hadal is a reference to the Greek god of the underworld Hades . In these trenches, the temperature is just above freezing, and the water pressure is enormous. For example, the hadopelagic zone extends into the ocean's deepest trench, the Mariana Trench, located in the western Pacific Ocean basin, with a maximum depth of nearly 11,000 meters. At that depth, the water column above is exerting a pressure of over one thousand atmospheres. [ 10 ]
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Water content or moisture content is the quantity of water contained in a material, such as soil (called soil moisture ), rock , ceramics , crops , or wood . Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 (completely dry) to the value of the materials' porosity at saturation. It can be given on a volumetric or mass (gravimetric) basis.
Volumetric water content , θ, is defined mathematically as:
where V w {\displaystyle V_{w}} is the volume of water and V wet = V s + V w + V a {\displaystyle V_{\text{wet}}=V_{s}+V_{w}+V_{a}} is equal to the total volume of the wet material, i.e. of the sum of the volume of solid host material (e.g., soil particles, vegetation tissue) V s {\displaystyle V_{s}} , of water V w {\displaystyle V_{w}} , and of air V a {\displaystyle V_{a}} .
Gravimetric water content [ 1 ] is expressed by mass (weight) as follows:
where m w {\displaystyle m_{w}} is the mass of water and m s {\displaystyle m_{s}} is the mass of the solids.
For materials that change in volume with water content, such as coal , the gravimetric water content, u , is expressed in terms of the mass of water per unit mass of the moist specimen (before drying):
However, woodworking , geotechnics and soil science require the gravimetric moisture content to be expressed with respect to the sample's dry weight:
And in food science , both u ′ {\displaystyle u'} and u ″ {\displaystyle u''} are used and called respectively moisture content wet basis (MC wb ) and moisture content dry basis (MC db ). [ 2 ]
Values are often expressed as a percentage, i.e. u ×100%.
To convert gravimetric water content to volumetric water content, multiply the gravimetric water content by the bulk specific gravity S G {\displaystyle SG} of the material:
In soil mechanics and petroleum engineering the water saturation or degree of saturation , S w {\displaystyle S_{w}} , is defined as
where ϕ = V v / V {\displaystyle \phi =V_{v}/V} is the porosity , in terms of the volume of void or pore space V v {\displaystyle V_{v}} and the total volume of the substance V {\displaystyle V} . [ clarification needed ] Values of S w can range from 0 (dry) to 1 (saturated). In reality, S w never reaches 0 or 1 - these are idealizations for engineering use.
The normalized water content , Θ {\displaystyle \Theta } , (also called effective saturation or S e {\displaystyle S_{e}} ) is a dimensionless value defined by van Genuchten [ 3 ] as:
where θ {\displaystyle \theta } is the volumetric water content; θ r {\displaystyle \theta _{r}} is the residual water content, defined as the water content for which the gradient d θ / d h {\displaystyle d\theta /dh} becomes zero; and, θ s {\displaystyle \theta _{s}} is the saturated water content, which is equivalent to porosity, ϕ {\displaystyle \phi } .
Water content can be directly measured using a drying oven . The oven-dry method requires drying a sample (of soil, wood, etc.) in a special oven or kiln and checking the sample weight at regular time intervals. When the drying process is complete, the sample's weight is compared to its weight before drying, and the difference is used to calculate the sample's original moisture content.
Gravimetric water content, u , is calculated [ 4 ] via the mass of water m w {\displaystyle m_{w}} :
where m wet {\displaystyle m_{\text{wet}}} and m dry {\displaystyle m_{\text{dry}}} are the masses of the sample before and after drying in the oven.
This gives the numerator of u ; the denominator is either m wet {\displaystyle m_{\text{wet}}} or m dry {\displaystyle m_{\text{dry}}} (resulting in u' or u" , respectively), depending on the discipline.
On the other hand, volumetric water content, θ , is calculated [ 5 ] via the volume of water V w {\displaystyle V_{w}} :
where ρ w {\displaystyle \rho _{w}} is the density of water .
This gives the numerator of θ ; the denominator, V wet {\displaystyle V_{\text{wet}}} , is the total volume of the wet material, which is fixed by simply filling up a container of known volume (e.g., a tin can ) when taking a sample.
For wood , the convention is to report moisture content on oven-dry basis (i.e. generally drying sample in an oven set at 105 deg Celsius for 24 hours or until it stops losing weight). In wood drying , this is an important concept.
Other methods that determine water content of a sample include chemical titrations (for example the Karl Fischer titration ), determining mass loss on heating (perhaps in the presence of an inert gas), or after freeze drying . In the food industry the Dean-Stark method is also commonly used.
From the Annual Book of ASTM (American Society for Testing and Materials) Standards, the total evaporable moisture content in Aggregate (C 566) can be calculated with the formula:
where p {\displaystyle p} is the fraction of total evaporable moisture content of sample, W {\displaystyle W} is the mass of the original sample, and D {\displaystyle D} is mass of dried sample.
In addition to the direct and laboratory methods above, the following options are available.
There are several geophysical methods available that can approximate in situ soil water content. These methods include: time-domain reflectometry (TDR), neutron probe , frequency domain sensor , capacitance probe , amplitude domain reflectometry , electrical resistivity tomography , ground penetrating radar (GPR), and others that are sensitive to the physical properties of water . [ 6 ] Geophysical sensors are often used to monitor soil moisture continuously in agricultural and scientific applications.
Satellite microwave remote sensing is used to estimate soil moisture based on the large contrast between the dielectric properties of wet and dry soil. The microwave radiation is not sensitive to atmospheric variables, and can penetrate through clouds. Also, microwave signal can penetrate, to a certain extent, the vegetation canopy and retrieve information from ground surface. [ 7 ] The data from microwave remote sensing satellites such as WindSat, AMSR-E, RADARSAT, ERS-1-2, Metop/ASCAT, and SMAP are used to estimate surface soil moisture. [ 8 ]
In addition to the primary methods above, another method exists to measure the moisture content of wood: an electronic moisture meter .
Pin and pinless meters are the two main types of moisture meters.
Pin meters require driving two pins into the surface of the wood while making sure that the pins are aligned with the grain and not perpendicular to it. Pin meters provide moisture content readings by measuring the resistance in the electrical current between the two pins. The drier the wood, the more resistance to the electrical current, when measuring below the fiber saturation point of wood. Pin meters are generally preferred when there is no flat surface of the wood available to measure
Pinless meters emit an electromagnetic signal into the wood to provide readings of the wood's moisture content and are generally preferred when damage to the wood's surface is unacceptable or when a high volume of readings or greater ease of use is required.
Moisture may be present as adsorbed moisture at internal surfaces and as capillary condensed water in small pores. At low relative humidities, moisture consists mainly of adsorbed water. At higher relative humidities, liquid water becomes more and more important, depending or not depending on the pore size can also be an influence of volume. In wood-based materials, however, almost all water is adsorbed at humidities below 98% RH.
In biological applications there can also be a distinction between physisorbed water and "free" water — the physisorbed water being that closely associated with and relatively difficult to remove from a biological material. The method used to determine water content may affect whether water present in this form is accounted for. For a better indication of "free" and "bound" water, the water activity of a material should be considered.
Water molecules may also be present in materials closely associated with individual molecules, as "water of crystallization", or as water molecules which are static components of protein structure.
In soil science , hydrology and agricultural sciences , water content has an important role for groundwater recharge , agriculture , and soil chemistry . Many recent scientific research efforts have aimed toward a predictive-understanding of water content over space and time. Observations have revealed generally that spatial variance in water content tends to increase as overall wetness increases in semiarid regions, to decrease as overall wetness increases in humid regions, and to peak under intermediate wetness conditions in temperate regions . [ 9 ]
There are four standard water contents that are routinely measured and used, which are described in the following table:
And lastly the available water content , θ a , which is equivalent to:
which can range between 0.1 in gravel and 0.3 in peat .
When a soil becomes too dry, plant transpiration drops because the water is increasingly bound to the soil particles by suction. Below the wilting point plants are no longer able to extract water. At this point they wilt and cease transpiring altogether. Conditions where soil is too dry to maintain reliable plant growth is referred to as agricultural drought , and is a particular focus of irrigation management. Such conditions are common in arid and semi-arid environments.
Some agriculture professionals are beginning to use environmental measurements such as soil moisture to schedule irrigation . This method is referred to as smart irrigation or soil cultivation . [ 10 ]
In saturated groundwater aquifers , all available pore spaces are filled with water (volumetric water content = porosity ). Above a capillary fringe , pore spaces have air in them too.
Most soils have a water content less than porosity, which is the definition of unsaturated conditions, and they make up the subject of vadose zone hydrogeology. The capillary fringe of the water table is the dividing line between saturated and unsaturated conditions. Water content in the capillary fringe decreases with increasing distance above the phreatic surface. The flow of water through and unsaturated zone in soils often involves a process of fingering, resulting from Saffman–Taylor instability . This results mostly through drainage processes and produces and unstable interface between saturated and unsaturated regions.
One of the main complications which arises in studying the vadose zone, is the fact that the unsaturated hydraulic conductivity is a function of the water content of the material. As a material dries out, the connected wet pathways through the media become smaller, the hydraulic conductivity decreasing with lower water content in a very non-linear fashion.
A water retention curve is the relationship between volumetric water content and the water potential of the porous medium. It is characteristic for different types of porous medium. Due to hysteresis , different wetting and drying curves may be distinguished.
Generally, an aggregate has four different moisture conditions. They are Oven-dry (OD), Air-dry (AD), Saturated surface dry (SSD) and damp (or wet). [ 11 ] Oven-dry and Saturated surface dry can be achieved by experiments in laboratories, while Air-dry and damp (or wet) are aggregates' common conditions in nature.
The water adsorption by mass (A m ) is defined in terms of the mass of saturated-surface-dry (M ssd ) sample and the mass of oven dried test sample (M dry ) by the formula:
Among these four moisture conditions of aggregates, saturated surface dry is the condition that has the most applications in laboratory experiments, research, and studies, especially those related to water absorption, composition ratio, or shrinkage tests in materials like concrete. For many related experiments, a saturated surface dry condition is a premise that must be realized before the experiment. In saturated surface dry conditions, the aggregate's water content is in a relatively stable and static situation where its environment would not affect it. Therefore, in experiments and tests where aggregates are in saturated surface dry condition, there would be fewer disrupting factors than in the other three conditions. [ 14 ] [ 15 ]
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Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling . Water is inexpensive and non-toxic; however, it can contain impurities and cause corrosion.
Water cooling is commonly used for cooling automobile internal combustion engines and power stations . Water coolers utilising convective heat transfer are used inside high-end personal computers to lower the temperature of CPUs and other components.
Other uses include the cooling of lubricant oil in pumps ; for cooling purposes in heat exchangers ; for cooling buildings in HVAC and in chillers .
Water is inexpensive, non-toxic , and available over most of the earth's surface. Liquid cooling offers higher thermal conductivity than air cooling. Water has unusually high specific heat capacity among commonly available liquids at room temperature and atmospheric pressure allowing efficient heat transfer over distance with low rates of mass transfer. Cooling water may be recycled through a recirculating system or used in a single-pass once-through cooling (OTC) system. Water's high enthalpy of vaporization allows the option of efficient evaporative cooling to remove waste heat in cooling towers or cooling ponds . [ 1 ] Recirculating systems are open if they rely upon evaporative cooling or closed if heat removal is accomplished in heat exchangers , thus with negligible evaporative loss. A heat exchanger or condenser may separate non-contact cooling water from a fluid being cooled, [ 2 ] or contact cooling water may directly impinge on items like saw blades where phase difference allows easy separation . Environmental regulations emphasize the reduced concentrations of waste products in non-contact cooling water. [ 3 ]
Water accelerates the corrosion of metal parts and is a favorable medium for biological growth. Dissolved minerals in natural water supplies are concentrated by evaporation to leave deposits called scale. Cooling water often requires the addition of chemicals to minimize corrosion and insulating deposits of scale and biofouling. [ 4 ]
Water contains varying amounts of impurities from contact with the atmosphere, soil, and containers. Being both an electrical conductor and a solvent for metal ions and oxygen, water can accelerate corrosion of machinery being cooled. Corrosion reactions proceed more rapidly as temperature increases. [ 4 ] Preservation of machinery in the presence of hot water has been improved by addition of corrosion inhibitors including zinc , chromates and phosphates . [ 5 ] [ 6 ] The first two have toxicity concerns; [ 7 ] and the last has been associated with eutrophication . [ 8 ] Residual concentrations of biocides and corrosion inhibitors are of potential concern for OTC and blowdown from open recirculating cooling water systems. [ 9 ] With the exception of machines with short design life, closed recirculating systems require periodic cooling-water treatment or replacement raising similar concern about ultimate disposal of cooling water containing chemicals used with environmental safety assumptions of a closed system. [ 10 ]
Biofouling occurs because water is a favorable environment for many life forms. Flow characteristics of recirculating cooling water systems encourage colonization by sessile organisms using the circulating supply of food, oxygen and nutrients. [ 11 ] Temperatures may become high enough to support thermophilic populations of organisms such as types of fungi . [ 12 ] Biofouling of heat exchange surfaces can reduce heat transfer rates of the cooling system, and biofouling of cooling towers can alter flow distribution to reduce evaporative cooling rates. Biofouling may also create differential oxygen concentrations increasing corrosion rates. OTC and open recirculating systems are more susceptible to biofouling. Biofouling may be inhibited by temporary habitat modifications. Temperature differences may discourage the establishment of thermophilic populations in intermittently operated facilities, and intentional short-term temperature spikes may periodically kill less tolerant populations. Biocides have been commonly used to control biofouling where sustained facility operation is required. [ 13 ]
Chlorine may be added in the form of hypochlorite to decrease biofouling in cooling water systems, but is later reduced to chloride to minimize the toxicity of blowdown or OTC water returned to natural aquatic environments. Hypochlorite is increasingly destructive to wooden cooling towers as pH increases. Chlorinated phenols have been used as biocides or leached from preserved wood in cooling towers. Both hypochlorite and pentachlorophenol have reduced effectiveness at pH values greater than 8. [ 14 ] Non-oxidizing biocides may be more difficult to detoxify prior to release of blowdown or OTC water to natural aquatic environments. [ 15 ]
Concentrations of polyphosphates or phosphonates with zinc and chromates or similar compounds have been maintained in cooling systems to keep heat exchange surfaces clean enough that a film of gamma iron oxide and zinc phosphate can inhibit corrosion by passivating anodic and cathodic reaction points. [ 16 ] These increase salinity and total dissolved solids, and phosphorus compounds may provide the limiting essential nutrient for algal growth contributing to biofouling of the cooling system or to eutrophication of natural aquatic environments receiving blowdown or OTC water. Chromates reduce biofouling in addition to effective corrosion inhibition in the cooling water system, but residual toxicity in blowdown or OTC water has encouraged lower chromate concentrations and the use of less-flexible corrosion inhibitors. [ 7 ] Blowdown may also contain chromium leached from cooling towers constructed of wood preserved with chromated copper arsenate . [ 17 ]
Total dissolved solids or TDS (sometimes called filterable residue) is reported as the mass of residue remaining when a measured volume of filtered water is evaporated . [ 18 ] Salinity indicates water density or conductivity changes caused by dissolved materials. [ 19 ] Probability of scale formation increases with increasing total dissolved solids. Solids commonly associated with scale formation are calcium and magnesium both as carbonate and sulfate . Corrosion rates initially increase with salinity in response to increasing electrical conductivity, but then decrease after reaching a peak as higher levels of salinity decrease dissolved oxygen levels. [ 4 ]
Some groundwater contains very little oxygen when pumped from wells, but most natural water supplies include dissolved oxygen. Increasing oxygen concentrations accelerate corrosion. [ 4 ] Dissolved oxygen approaches saturation levels in cooling towers. It is beneficial in blowdown or OTC water being returned to natural aquatic environments. [ 20 ]
Water ionizes into hydronium (H 3 O + ) cations and hydroxide (OH − ) anions . The concentration of ionized hydrogen (as protonated water) in a cooling water system is reported as the pH level. [ 21 ] Low pH values increase the rate of corrosion; high pH values encourage scale formation. Amphoterism is uncommon among metals used in water cooling systems, but aluminum corrosion rates increase with pH values above 9. Galvanic corrosion may be severe in water systems with copper and aluminum components. Acid can be added to cooling water systems to prevent scale formation if the pH decrease will offset increased salinity and dissolved solids. [ 22 ]
Few other cooling applications approach the large volumes of water required to condense low-pressure steam at power stations . [ 24 ] Many facilities, particularly electric power plants, use millions of gallons of water per day for cooling. [ 25 ] Water cooling on this scale may alter natural water environments and create new environments. Thermal pollution of rivers, estuaries and coastal waters is a consideration when siting such plants. Water returned to aquatic environments at temperatures higher than the ambient receiving water modifies aquatic habitat by increasing biochemical reaction rates and decreasing the oxygen saturation capacity of the habitat. Temperature increases initially favor a population shift from species requiring the high-oxygen concentration of cold water to those enjoying the advantages of increased metabolic rates in warm water. [ 11 ]
Once-through cooling (OTC) systems may be used on very large rivers or at coastal and estuarine sites. These power stations put the waste heat into the river or coastal water. These OTC systems thus rely upon an ample supply of river water or seawater for their cooling needs. Such facilities are built with intake structures designed for bringing in large volumes of water at a high rate of flow. These structures tend to also pull in large numbers of fish and other aquatic organisms, which are killed or injured on the intake screens . [ 26 ] Large flow rates may trap slow-swimming organisms including fish and shrimp on screens protecting the small bore tubes of the heat exchangers from blockage. High temperatures or pump turbulence and shear may kill or disable smaller organisms that pass through the screens entrained with the cooling water. [ 27 ] : Ch. A2 More than 1,200 power plants and manufacturing facilities in the U.S. use OTC systems; [ 28 ] : 4–4 the intake structures kill billions of fish and other organisms each year. [ 29 ] More-agile aquatic predators consume organisms impinged on the screens; and warm water predators and scavengers colonize the cooling water discharge to feed on entrained organisms.
The U.S. Clean Water Act required the Environmental Protection Agency (EPA) to issue regulations on industrial cooling water intake structures. [ 30 ] EPA issued final regulations for new facilities in 2001 (amended 2003), [ 26 ] [ 31 ] and for existing facilities in 2014. [ 32 ]
As an alternative to OTC, industrial cooling towers may use recirculated river water, coastal water ( seawater ), or well water. Large mechanical induced-draft or forced-draft cooling towers in industrial plants continuously circulate cooling water through heat exchangers and other equipment where the water absorbs heat. That heat is then rejected to the atmosphere by the evaporation of some of the water in cooling towers where upflowing air contacts the downflowing water. The loss of evaporated water into the air exhausted to the atmosphere is replaced by "make-up" fresh river water or fresh cooling water, but the amount of water lost during evaporative cooling may affect the natural habitat for aquatic organisms. Because the evaporated pure water is replaced by make-up water containing carbonates and other dissolved salts, a portion of the circulating water is continuously discarded as "blowdown" water to minimize the excessive build-up of salts in the circulating water; these blowdown wastes may change the receiving water quality. [ 33 ]
The heated coolant mixture can be used to warm the air inside the car by means of the heater core . Also, the water jacket around an engine is very effective at deadening mechanical noises, making the engine quieter.
An open water cooling system makes use of evaporative cooling , lowering the temperature of the remaining (unevaporated) water. This method was common in early internal combustion engines until scale buildup was observed from dissolved salts and minerals in the water. Modern open cooling systems continuously waste a fraction of recirculating water as blowdown to remove dissolved solids at concentrations low enough to prevent scale formation. Some open systems use inexpensive tap water , but this requires higher blowdown rates than deionized or distilled water . Purified water systems still require blowdown to remove the accumulation of byproducts of chemical treatment to prevent corrosion and biofouling. [ 34 ]
Water for cooling has a boiling point temperature of around 100 degrees C at atmospheric pressure. Engines operating at higher temperatures may require a pressurized recycle loop to prevent overheating. [ 35 ] Modern automotive cooling systems often operate at 15 psi (103 kPa) to raise the boiling-point of the recycling water coolant and reduce evaporative losses. [ 36 ]
The use of water cooling carries the risk of damage from freezing. Automotive and many other engine cooling applications require the use of a water and antifreeze mixture to lower the freezing point to a temperature unlikely to be experienced. Antifreeze also inhibits corrosion from dissimilar metals and can increase the boiling point, allowing a wider range of water cooling temperatures. [ 36 ] Its distinctive odor also alerts operators to cooling system leaks and problems that would go unnoticed in a water-only cooling system.
Other less common chemical additives are products to reduce surface tension. These additives are meant to increase the efficiency of automotive cooling systems. Such products are used to enhance the cooling of underperforming or undersized cooling systems or in racing where the weight of a larger cooling system could be a disadvantage. [ citation needed ]
Since approximately 1930 it is common to use water cooling for tubes of powerful transmitters. As these devices use high operation voltages (around 10 kV), the use of deionized water is required and it has to be carefully controlled.
Modern solid-state transmitters can be built so that even high-power transmitters do not require water cooling. Water cooling is however also sometimes used for thyristors of HVDC valves, for which the use of deionized water is required. [ citation needed ]
Liquid cooling techniques are increasingly being used for the thermal management of electronic components. This type of cooling is a solution to ensure the optimisation of energy efficiency while simultaneously minimising noise and space requirements. Especially useful in supercomputers or Data Centers because maintenance of the racks is quick and easy. After disassembly of the rack, advanced-technology quick-release couplings eliminate spillage for the safety of operators and protect the integrity of fluids (no impurities in the circuits). These couplings are also capable of being locked (Panel mounted?) to allow blind connection in difficult-to-access areas. [ citation needed ] It is important in electronics technology to analyse the connection systems to ensure:
Water cooling often adds complexity and cost in comparison to air cooling design by requiring a pump, tubing or piping to transport the water, and a radiator, often with fans, to reject the heat to the atmosphere. Depending on the application, water cooling may create an additional element of risk where leakage from the water coolant recycle loop can corrode or short-circuit sensitive electronic components.
The primary advantage of water cooling for cooling CPU cores in computing equipment is transporting heat away from the source to a secondary cooling surface to allow for large, more optimally designed radiators rather than small, relatively inefficient fins mounted directly on the heat source. Cooling hot computer components with various fluids has been in use since at least the Cray-2 in 1982, which used Fluorinert . Through the 1990s, water cooling for home PCs slowly gained recognition among enthusiasts, but it became noticeably more prevalent after the introduction of the first Gigahertz-clocked processors in the early 2000s. As of 2018, there are dozens of manufacturers of water cooling components and kits, and many computer manufacturers include preinstalled water cooling solutions for their high-performance systems.
Water cooling can be used for many computer components, but usually it is used for the CPU and GPUs . Water cooling typically uses a water block , a water pump , and a water-to-air heat exchanger. By transferring device heat to a separate larger heat exchanger using larger, lower-speed fans, water cooling can allow quieter operation, improved processor speeds ( overclocking ), or a balance of both. Less commonly, Northbridges , Southbridges , hard disk drives , memory , voltage regulator modules (VRMs), and even power supplies can be water-cooled. [ 37 ]
Internal radiator size may vary: from 40 mm dual fan (80 mm) to 140 quad fan (560 mm) and thickness from 30 mm to 80 mm. Radiator fans may be mounted on one or both sides. External radiators can be much larger than their internal counterparts as they do not need to fit in the confines of a computer case. High-end cases may have two rubber grommeted ports in the back for the inlet and outlet hoses, which allow external radiators to be placed far away from the PC.
A T-Line is used to remove trapped air bubbles from the circulating water. It is made with a t-connector and a capped-off length of tubing. The tube n acts as a mini-reservoir and allows air bubbles to travel into it as they are caught into the "tee" connector, and ultimately removed from the system by bleeding. The capped line may be capped with a fill-port fitting to allow the release of trapped gas and the addition of liquid. [ citation needed ]
Water coolers for desktop computers were, until the end of the 1990s, homemade. They were made from car radiators (or more commonly, a car's heater core ), aquarium pumps and home-made water blocks, laboratory-grade PVC and silicone tubing and various reservoirs (homemade using plastic bottles, or constructed using cylindrical acrylic or sheets of acrylic, usually clear) and or a T-Line . More recently [ when? ] a growing number of companies are manufacturing water-cooling components compact enough to fit inside a computer case. [ 38 ] This, and the trend to CPUs of higher power dissipation, has greatly increased the popularity of water cooling.
Dedicated overclockers have occasionally used vapor-compression refrigeration or thermoelectric coolers in place of more common standard heat exchangers. Water cooling systems in which water is cooled directly by the evaporator coil of a phase change system are able to chill the circulating coolant below the ambient air temperature (impossible with a standard heat exchanger) and, as a result, generally provide superior cooling of the computer's heat-generating components. The downside of phase-change or thermoelectric cooling is that it uses much more electricity, and antifreeze must be added due to the low temperature. Additionally, insulation, usually in the form of lagging around water pipes and neoprene pads around the components to be cooled, must be used in order to prevent damage caused by condensation of water vapour from the air on chilled surfaces. Common places from which to obtain the required phase transition systems are a household dehumidifier or air conditioner . [ 39 ]
An alternative cooling scheme, which also enables components to be cooled below the ambient temperature while obviating the requirement for antifreeze and lagged pipes, is to place a thermoelectric device (commonly referred to as a 'Peltier junction' or 'pelt' after Jean Peltier , who documented the effect) between the heat-generating component and the water block. Because the only sub-ambient temperature zone now is at the interface with the heat-generating component itself, insulation is required only in that localized area. The disadvantage of such a system is higher power dissipation. [ citation needed ]
To avoid damage from condensation around the Peltier junction, a proper installation requires it to be "potted" with silicone epoxy. The epoxy is applied around the edges of the device, preventing air from entering or leaving the interior. [ citation needed ]
Apple's Power Mac G5 was the first mainstream desktop computer to have water cooling as standard (although only on its fastest models). Dell followed suit by shipping their XPS computers with liquid cooling [ citation needed ] , using thermoelectric cooling to help cool the liquid. Currently, Dell's only computers to offer liquid cooling are their Alienware desktops. [ 40 ]
Asus are the first and only mainstream brand to have put water-cooled laptops into mass production. Those laptops have a built-in air/water hybrid cooling system and can be docked to an external liquid cooling radiator for additional cooling and electrical power. [ 41 ] [ 42 ]
Water is an ideal cooling medium for vessels as they are constantly surrounded by water that generally remains at a low temperature throughout the year. Systems operating with seawater need to be manufactured from cupronickel , bronze , titanium or similarly corrosion-resistant materials. Water containing sediment may require velocity restrictions through piping to avoid erosion at high velocity or blockage by settling at low velocity. [ 43 ]
Plant transpiration and animal perspiration use evaporative cooling to prevent high temperatures from causing unsustainable metabolic rates .
Machine guns used in fixed defensive positions sometimes use water cooling to extend barrel life through periods of rapid fire, but the weight of the water and pumping system significantly reduces the portability of water-cooled firearms. Water-cooled machine guns were extensively used by both sides during World War I ; however, by the end of the war lighter weapons that rivaled the firepower, effectiveness and reliability of water-cooled models began to appear on the battlefield. Thus water-cooled weapons have played a far lesser role in subsequent conflicts.
A hospital in Sweden relies on snow-cooling from melt-water to cool its data centers, medical equipment, and maintain a comfortable ambient temperature. [ 44 ]
Some nuclear reactors use heavy water as coolant. Heavy water is employed in nuclear reactors because it is a weaker neutron absorber . This allows for the use of less-enriched fuel. For the main cooling system, normal water is preferably employed through the use of a heat exchanger, as heavy water is much more expensive. Reactors that use other materials for moderation (graphite) may also use normal water for cooling .
High-grade industrial water (produced by reverse osmosis or distillation ) and potable water are sometimes used in industrial plants requiring high-purity cooling water. Production of these high-purity waters creates waste byproduct brines containing the concentrated impurities from the source water.
In 2018, researchers from the University of Colorado Boulder and University of Wyoming invented a radiative cooling metamaterial known as "RadiCold", which has been developed since 2017. This metamaterial aids in cooling of water and increasing the efficiency of power generation, in which it would cool the underneath objects, by reflecting away the sun's rays while at the same time allowing the surface to discharge its heat as infrared thermal radiation. [ 45 ]
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Alkaline hydrolysis (also called biocremation , resomation , [ 1 ] [ 2 ] flameless cremation , [ 3 ] aquamation [ 4 ] or water cremation [ 5 ] ) is a process for the disposal of human and pet remains using lye and heat; it is alternative to burial , cremation , or sky burial .
The process is based on alkaline hydrolysis : the body is placed in a pressure vessel which is then filled with a mixture of water and potassium hydroxide , and heated to a temperature of around 160 °C (320 °F) at an elevated pressure which precludes boiling. The body is efficiently broken down into its chemical components, (completely disintegrating its DNA), a process which takes approximately four to six hours. Also, lower temperatures (98 °C (208 °F)) and pressures may be used such that the process takes a leisurely 14 to 16 hours. [ 6 ] At the start, the mixture is very alkaline, with a pH level of approximately 14; this drops to approximately 11 by the end, but the exact value depends on the total operation time and the amount of fat in the body. [ 7 ]
The result is a quantity of green-brown tinted liquid (containing amino acids , peptides , sugars and salts ) and soft, porous white bone remains ( calcium phosphate ) easily crushed in the hand (although a cremulator is more commonly used) to form a white-colored dust. The "ash" can then be returned to the next of kin of the deceased. The liquid is disposed of either through the sanitary sewer system, or through some other method, including use in a garden or green space. [ 8 ] To dispose of 1,000 pounds (450 kg) of biomass, approximately 60–240 US gallons (230–910 L; 50–200 imp gal) of water are used, resulting in 120–300 US gallons (450–1,140 L; 100–250 imp gal) of effluent, which carries a dried weight (inorganic and mineral
content) of 20 pounds (9.1 kg) (approximately 2% of original weight). [ 7 ]
This alkaline hydrolysis process has been championed by a number of ecological campaigning groups, [ 9 ] for using 90 kWh of electricity, [ 10 ] one-quarter the energy of flame-based cremation , and producing less carbon dioxide and pollutants. [ 1 ] [ 5 ] It is being presented as an alternative option at some British crematorium sites. [ 11 ] As of August 2007 [update] , about 1,000 people had chosen this method for the disposal of their remains in the United States . [ 12 ] The operating cost of materials, maintenance, and labor associated with the disposal of 2,000 pounds (910 kg) of remains was estimated at $116.40, [ 7 ] excluding the capital investment cost of equipment.
Alkaline hydrolysis has also been adopted by the pet and animal industry. A handful of companies in North America offer the procedure as an alternative to pet cremation. [ 13 ] Alkaline hydrolysis is also used in the agricultural industry to sterilize animal carcasses that may pose a health hazard, because the process inactivates viruses, bacteria, and prions that cause transmissible spongiform encephalopathy . [ 7 ] [ 14 ] [ 15 ]
The process was patented by Amos Herbert Hobson in 1888 as a method to process animal carcasses into plant food. [ 6 ] [ 16 ] [ 10 ] In 2005, Bio-Response Solutions designed, sold, and installed the first single cadaver alkaline hydrolysis system at the Mayo Clinic , where it was still in use as of 2019. [ 17 ] In 2007, a Scottish biochemist, Sandy Sullivan, started a company making the machines, and calling the process (and company) Resomation. [ 18 ]
In Christian countries and cultures, cremation has historically been discouraged and viewed as a desecration of God's image, and as interference with the resurrection of the dead taught in scripture. It is now acceptable to some denominations. [ 19 ] Desmond Tutu , former Anglican Archbishop of Cape Town , was aquamated, per his wish. [ 20 ] The Eastern Orthodox Church does not allow cremation.
The Roman Catholic Church allows cremation of bodies as long as it is not done in denial of the beliefs in the sacredness of the human body or the resurrection of the dead. [ 21 ] In 2008, Renée Mirkes published the first Catholic moral analysis of alkaline hydrolysis. [ 22 ] [ 23 ] He argued that it is morally neutral and may be an alternative to burial on similar grounds to cremation. [ 23 ] However, the Catholic Church in the United States does not approve of alkaline hydrolysis as a method of final disposal of human remains. In 2011, Donald Cardinal Wuerl , Archbishop of Washington and then chairman of the Committee on Doctrine of the United States Conference of Catholic Bishops (USCCB), determined it "unnecessarily disrespectful of the human body." [ 24 ] The Archdiocese of St. Louis explained that it was considered this way because the Church took concern with the final disposal of the liquid solution, which is typically to the sewer system. [ 25 ] This was considered disrespectful of the sanctity of the human body. [ 25 ] Additionally, when alkaline hydrolysis was proposed in New York state in 2012, the New York State Catholic Conference condemned the practice, stating that hydrolysis does not show sufficient respect for the teaching of the intrinsic dignity of the human body. [ 26 ]
Judaism forbids cremation as it is not in line with the religion’s teachings of respect and dignity for humans, who are believed by the religion to be created in God’s image. Islam also forbids cremation of the deceased. Both religions are likely to reject alkaline hydrolysis as they believe that the body must be laid to rest through burial in order to prepare for the afterlife. [ 22 ] The Baháʼí Faith , like other Abrahamic religions, discourages cremation of the deceased. The human body is seen as having to be treated with respect, and merely wrapped in a shroud before burial no further than an hour from the place of death.
Sikhism , Hinduism , and Buddhism each place theological emphasis on the complete immolation of the corpse. [ 22 ]
Native Hawaiians consider aquamation a way to approximate their traditional burial ritual, which involves removing the bones (iwi) cleanly from the flesh using a beachside underground oven (imu), wrapping the bones, and hiding them. The use of an imu on human bodies is no longer allowed, but aquamation may offer an alternative as it produces similarly clean bones. [ 27 ]
Aquamation based in New South Wales is the only company to provide alkaline hydrolysis in Australia, with the remains being used as fertilizer on plantation forests , due to difficulty with obtaining permits from Sydney Water . [ 28 ]
Water Cremation Aotearoa [ 29 ] has been an advocate for bringing the service to New Zealand (Aotearoa). Water cremation services will be offered in Christchurch by Bell, Lamb and Trotter. [ 30 ]
The Flemish minister of Interior Administration Bart Somers asked in September 2021 the opinion of an advisory bioethics committee on resomation. The advice, received in November 2021, saw no objections. [ 31 ]
Saskatchewan approved the process in 2012, becoming the first province to do so. [ 32 ] Quebec and Ontario have also legalized the process. [ 33 ] A funeral home in Granby, Quebec , was the first in the province to receive an alkaline hydrolysis machine. [ 34 ]
In 2023, water cremation became available in Ireland, making it the first country in Europe to offer this form of burial. [ 35 ]
When the process is complete, the remaining water undergoes further treatment to ensure that it is completely sterile. Analysis is then completed to ensure Water Authority standards are met. At this stage, the water can be recycled back to the Local Authority water treatment plant.
Since 2019, Grupo Gayosso offers alkaline hydrolysis in Baja California . [ 36 ]
In May 2020, the Health Council of the Netherlands issued an advisory report on the admissibility of new techniques of disposing of the dead. The Council proposed a framework to assess alkaline hydrolysis. It concluded that alkaline hydrolysis is safe, dignified and sustainable. [ 37 ] In addition to alkaline hydrolysis, the council also considered human composting as a technique to dispose bodies yet concluded that too little is known about composting and hence it cannot be assessed whether this technique fulfills the conditions. [ 37 ] Taking into account the council's recommendations, the Ministry of the Interior and Kingdom Relations prepared a law proposal to amend the Corpse Disposal Act. Once the proposed law has been submitted to the Parliament, the democratic process to admit alkaline hydrolysis as body disposal technique can be commenced.
In November 2019, Avbob introduced aquamation in South Africa, following the mutual assurance society's recent introduction of the alkaline hydrolysis process at its Maitland agency in Cape Town. [ 38 ] Aquamation has been legal in South Africa since then. Following his death in December 2021 the body of Archbishop Desmond Tutu was aquamated. [ 20 ]
A public crematorium operated by Sandwell Metropolitan Borough Council at Rowley Regis , central England, was the first to receive planning permission to offer the process but in March 2017, the local water utility, Severn Trent Water , refused the council's application for a "trade effluent permit" because there was no water industry standard regulating the disposal of liquefied human remains into sewers. [ 39 ] [ 40 ]
In July 2023, the BBC reported that “[w]ater cremation is set to be made available for the first time in the UK.” [ 41 ]
Alkaline hydrolysis as a method of final disposition of human remains is legal in 24 states as of 2022 [update] . [ 5 ] [ 42 ] Legislation is pending in New Jersey, New York, Ohio, Pennsylvania, and Virginia. [ 43 ] [ 44 ] The process was legal in New Hampshire for several years but amid opposition by religious lobby groups it was banned in 2008 [ 45 ] and a proposal to legalize it was rejected in 2013. [ 46 ] [ 47 ] Alkaline hydrolysis has been used for cadavers donated for research at the University of Florida since the mid-1990s and at the Mayo Clinic [ 1 ] since 2005. [ 48 ] UCLA uses the process to dispose of donor bodies. [ 2 ]
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Water crystal gel or water beads or gel beads is any gel which absorbs and contains a large amount of water . Water gel is usually in spherical form and composed of a water-absorbing superabsorbent polymer (SAP, also known as slush powder in dry form) such as a polyacrylamide (frequently sodium polyacrylate ).
Water gels are used for:
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Water damage describes various possible losses caused by water intruding where it will enable attack of a material or system by destructive processes such as rotting of wood, mold growth, bacteria growth, rusting of steel , swelling of composite woods, damage to laminated materials like plywood , short-circuiting of electrical devices, etc.
The damage may be very slow and minor such as water spots that could eventually mar a surface, or it may be instantaneous and catastrophic such as burst pipes and flooding . However fast it occurs, water damage is a major contributor to loss of property.
An insurance policy may or may not cover the costs associated with water damage and the process of water damage restoration. While a common cause of residential water damage is often the failure of a sump pump, many homeowner's insurance policies do not cover the associated costs without an addendum which adds to the monthly premium of the policy. Often the verbiage of this addendum is similar to "Sewer and Drain Coverage".
In the United States , those individuals who are affected by wide-scale flooding may have the ability to apply for government and FEMA grants through the Individual Assistance program. [ 1 ] On a larger level, businesses, cities, and communities can apply to the FEMA Public Assistance program for funds to assist after a large flood. For example, the city of Fond du Lac Wisconsin received $1.2 million FEMA grant after flooding in June 2008. The program allows the city to purchase the water damaged properties, demolish the structures, and turn the former land into public green space. [ citation needed ]
Water damage can originate by different sources such as a broken dishwasher hose, a washing machine overflow, a dishwasher leakage, broken/leaking pipes, flood waters, groundwater seepage, building envelope failures (leaking roof, windows, doors, siding, etc.) and clogged toilets. According to the Environmental Protection Agency, 13.7% of all water used in the home today can be attributed to plumbing leaks. [ 2 ] On average that is approximately 10,000 gallons of water per year wasted by leaks for each US home. A tiny, 1/8-inch crack in a pipe can release up to 250 gallons of water a day. [ 3 ] According to Claims Magazine in August 2000, broken water pipes ranked second to hurricanes in terms of both the number of homes damaged and the amount of claims (on average $50,000 per insurance claim [ citation needed ] ) costs in the US. [ 4 ] Experts suggest that homeowners inspect and replace worn pipe fittings and hose connections to all household appliances that use water at least once a year. This includes washing machines, dishwashers, kitchen sinks, and bathroom lavatories, refrigerator icemakers, water softeners, and humidifiers. A few US companies offer whole-house leak protection systems utilizing flow-based technologies. A number of insurance companies offer policyholders reduced rates for installing a whole-house leak protection system.
As far as insurance coverage is concerned, damage caused by surface water intrusion to the dwelling is considered flood damage and is normally excluded from coverage under traditional homeowners' insurance. Surface water is water that enters the dwelling from the surface of the ground because of inundation or insufficient drainage and causes loss to the dwelling. Coverage for surface water intrusion [ 5 ] to the dwelling would usually require a separate flood insurance policy.
There are three basic categories of water damage, based on the level of contamination.
Category 1 Water - Refers to a source of water that does not pose a substantial threat to humans. Examples are broken water supply lines, tub or sink overflows or appliance malfunctions that involve water supply lines.
Category 2 Water - Refers to a source of water that contains a significant degree of chemical, biological or physical contaminants and causes discomfort or sickness when consumed or even exposed to. This type carries microorganisms and nutrients of micro-organisms. Examples are toilet bowls with urine (no feces ), sump pump failures, seepage due to hydrostatic failure and water discharge from dishwashers or washing machines.
Category 3 Water is grossly unsanitary. This water contains unsanitary agents, harmful bacteria and fungi , causing severe discomfort or sickness. This category includes water sources from sewage , seawater, rising water from rivers or streams, storm surge, ground surface water or standing water.
Categories of water damage can deteriorate based on environmental conditions, including time and temperature. (e.g., Category 1 water can deteriorate to Category 2 water)
Class of water damage is determined by the potential rate of evaporation based on the type of materials affected by water. For example, carpet pad that is saturated will have a greater potential evaporation rate due to its porosity that a hard wood floor that is saturated with water.
Determing the class of a water loss will help determine how much drying equipment such as air movers and dehumidifiers are required to efficiently dry the structural components.
Class 1 — (least amount of water absorption and evaporation load): Water intrusion where wet,
porous materials (e.g., carpet, gypsum board, fiber-fill insulation, concrete masonry unit (CMU),
textiles) represent less than ~5% of the combined floor, wall and ceiling surface area in the space;
and where materials described as low evaporation materials or assemblies have absorbed minimal
moisture (see definitions for Class 4 and low evaporation assemblies).
Class 2 — (significant amount of water absorption and evaporation load): water intrusion where
wet, porous materials (e.g., carpet, gypsum board, fiber-fill insulation, concrete masonry unit
(CMU), textiles) represent ~5% to ~40% of the combined floor, wall and ceiling surface area in the
space; and where materials described as low evaporation materials or assemblies have absorbed
minimal moisture (see definitions for Class 4 and low evaporation assemblies).
Class 3 — (greatest amount of water absorption and evaporation load): water intrusion where wet,
porous materials (e.g., carpet, gypsum board, fiber-fill insulation, concrete masonry unit (CMU),
textiles) represent more than ~40% of the combined floor, wall and ceiling surface area in the space; and where materials described as low evaporation materials or assemblies have absorbed
minimal moisture (see definitions for Class 4 and low evaporation assemblies).
Class 4 — (deeply held or bound water): water intrusion that involves a significant amount of water
absorption into low evaporation materials (e.g., plaster, wood, concrete, masonry) or low
evaporation assemblies (e.g., multilayer wallboard, multilayer subfloors, gym floors, or other
complex, built-up assemblies). Drying may require special methods, longer drying times, or
substantial water vapor pressure differentials.
Water damage restoration can be performed by property management teams, building maintenance personnel, or by the homeowners themselves; however, contacting a certified professional water damage restoration specialist is often regarded as the safest way to restore water damaged property. Certified professional water damage restoration specialists utilize psychrometrics to monitor the drying process. [ 6 ]
While there are currently no government regulations in the United States dictating procedures, The Institute of Inspection Cleaning and Restoration Certification (IICRC) [ 7 ] is the industry standards and certifying body. The current IICRC standard is ANSI/IICRC S500-2021. [ 8 ] It is the collaborative work of the IICRC, SCRT, IEI, IAQA, and NADCA.
The IICRC Water Restoration Certification (WRT) [ 9 ] teaches students the industry standard, technical drying concepts, categories and classes of water damage, equipment use, and moisutre identification. After students complete and IICRC course, they can become certified after passing an exam. The IICRC does not operate or hold classes, reather, they have IICRC approved schools [ 10 ] who teach certification classes. After completing the course and passing the exam, the IICRC issues students a certification.
Water Restoration companies are regulated by the appropriate state's Department of Consumer Affairs - usually the state contractors license board. While there are generally no contractors license classifications for water damage restoration, the work performed during a restoration project is often covered in adjacent license classifications.
When consumers or businesses hire water restoration companies, they should ensure they are a reputable company by checking reviews, verifying any applicable contractors licenses, IICRC certifications, if they are an IICRC Certified Firm, [ 11 ] and appropriate business insurance.
Water damage restoration is often prefaced by a loss assessment and evaluation of affected materials. The damaged area is inspected with water sensing equipment such as probes and other infrared tools in order to determine the source of the damage and possible extent of areas affected. Emergency mitigation services are the first order of business. Controlling the source of water, removal of non-salvageable materials, water extraction and pre-cleaning of impacted materials are all part of the mitigation process. Restoration services would then be rendered to the property in order to dry the structure, stabilize building materials, sanitize any affected or cross-contaminated areas, and deodorize all affected areas and materials. After the labor is completed, water damage equipment including air movers, air scrubbers, dehumidifiers, wood floor drying systems, and sub-floor drying equipment is left in the residence. The goal of the drying process is to stabilize the moisture content of impacted materials below 15%, the generally accepted threshold for microbial amplification. Industry standards state that drying vendors should return at regular time intervals, preferably every twenty-four hours, to monitor the equipment, temperature, humidity, and moisture content of the affected walls and contents.[6]
In conclusion, key aspects of water damage restoration include fast action, adequate equipment, moisture measurements, and structural drying. Dehumidification is especially crucial for structural components affected by water damage, such as wooden beams, flooring, and drywall.
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A water detector is an electronic device that is designed to detect the presence of water for purposes such as to provide an alert in time to allow the prevention of water leakage . A common design is a small cable or device that lies flat on a floor and relies on the electrical conductivity of water to decrease the resistance across two contacts. The device then sounds an audible alarm together with providing onward signaling in the presence of enough water to bridge the contacts. These are useful in a normally occupied area near any infrastructure that has the potential to leak water, such as HVAC , water pipes , drain pipes , vending machines , dehumidifiers , or water tanks .
Water leak detection is an expression more commonly used for larger, integrated systems installed in modern buildings or those containing valuable artifacts, materials or other critical assets where early notification of a potentially damaging leak would be beneficial. In particular, water leak detection has become a necessity in data centers, trading floors, banks, archives and other mission-critical infrastructure.
The water leak detection industry is small and specialized with only a few manufacturers operating worldwide. The original application was in the void created by "computer room" floors in the days of large main-frame computer systems. These use a modular, raised floor based around a structural "floor tile" usually 600 mm square and supported at the corners by pedestals. The void created gave easy access and routing for the mass of power, networking and other interconnecting cables associated with larger computer systems - processors, drives, routers etc. mainframe computers also generated large amounts of heat so a void under the floor could also be used as a plenum to distribute and diffuse chilled air around the computer room. The void therefore was likely to have chilled water pipes running through it along with the drains for condensates associated with refrigeration plant. In addition, designers found the floor void a very convenient place to route other wet services feeding bathrooms, radiators and other facilities.
A leak occurring within a floor void would therefore go unnoticed until the hydrostatic head of pressure meant that the water found its way through to floors below where its dripping through the ceiling would be noted or, and more disconcerting, the water would penetrate the joints and connectors of the power or network cabling and cause system failure from short circuit.
Current digital water leak detection systems can locate multiple water leaks to within 1 meter resolution over a complex network of cables running several kilometers. This functionality reduces the downtime and potential damage caused by inaccurate reporting that was common with older analogue based systems.
Water leak detection systems can be integrated with Building Management Systems using multiple protocols such as Modbus . Using SNMP protocols leak detection systems can inform IT staff in charge of monitoring data center and server rooms.
The computer room therefore became the early application for systems which would alert the operator to a leaking pipe in sufficient time for remedial action to be taken to prevent a disaster.
As computer rooms could be quite large simple "point of use" detectors were not really appropriate although Point Sensors do have value where simple, single point detection is required in, say, basements and sumps. Most modern leak detection systems developed around the use of a water sensitive cable [ 1 ] which can be laid in long lengths and complex patterns around the base of the floor; around the perimeter of rooms; as a "barrier" over which water has to flow; following, tracing or attached directly to lines of water pipes.
The mainframe computer room has largely been replaced with the Data Centre but the application has remained with almost universal use of "computer-room" style raised floors in nearly all new commercial and office construction. To warrant the installation of leak detection the operator has to perceive the risk in addition to the circumstances but most Mechanical and Electrical Design Engineers will take a view of the risk of damage from a leak in terms of effect on the client's own operations, services and assets and, often as important, those of their adjoining neighbours and those on floors below.
The installation of leak detection systems is therefore becoming more commonplace in most new commercial office construction schemes along with the more obvious targets of museums, galleries and archives.
Leak detection systems must be unobtrusive, effective and robust enough to withstand getting dirty and the moderate physical abuse of other works being carried out under the same floor.
Zoned systems have a reputation for being safe, reliable and not prone to the same types of false alarms which those systems which use cumulative resistance techniques.
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The water dimer consists of two water molecules loosely bound by a hydrogen bond . It is the smallest water cluster . Because it is the simplest model system for studying hydrogen bonding in water, it has been the target of many theoretical [ 1 ] [ 2 ] [ 3 ] (and later experimental) studies that it has been called a "theoretical Guinea pig". [ 4 ]
The ab initio binding energy between the two water molecules is estimated to be 5-6 kcal/mol, although values between 3 and 8 have been obtained depending on the method. The experimentally measured dissociation energy (including nuclear quantum effects) of (H 2 O) 2 and (D 2 O) 2 are 3.16 ± 0.03 kcal/mol (13.22 ± 0.12 kJ/mol) [ 5 ] and 3.56 ± 0.03 kcal/mol (14.88 ± 0.12 kJ/mol), [ 6 ] respectively. The values are in excellent agreement with calculations. [ 7 ] [ 8 ] The O-O distance of the vibrational ground-state is experimentally measured at ca. 2.98 Å; [ 9 ] the hydrogen bond is almost linear, but the angle with the plane of the acceptor molecule is about 57°. The vibrational ground-state is known as the linear water dimer (shown in the figure to the right), which is a near prolate top (viz., in terms of rotational constants [ clarification needed ] , A > B ≈ C). Other configurations of interest include the cyclic dimer and the bifurcated dimer.
The first theoretical study of the water dimer was an ab initio calculation published in 1968 by Morokuma and Pedersen. [ 10 ] Since then, the water dimer has been the focus of sustained interest by theoretical chemists concerned with hydrogen bonding—a search of the CAS database up to 2006 returns over 1100 related references (73 of them in 2005). In addition to serving as a model for hydrogen bonding, (H 2 O) 2 is thought to play a significant role in many atmospheric processes, including chemical reactions, condensation, and solar energy absorption by the atmosphere. [ 11 ] [ 12 ] [ 13 ] In addition, a complete understanding of the water dimer is thought to play a key role in a more thorough understanding of hydrogen bonding in liquid and solid forms of water.
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A water distribution system is a part of water supply network with components that carry potable water from a centralized treatment plant or wells to consumers to satisfy residential, commercial, industrial and fire fighting requirements. [ 3 ] [ 4 ]
Water distribution network is the term for the portion of a water distribution system up to the service points of bulk water consumers or demand nodes where many consumers are lumped together. [ 5 ] The World Health Organization (WHO) uses the term water transmission system for a network of pipes, generally in a tree-like structure, that is used to convey water from water treatment plants to service reservoirs , and uses the term water distribution system for a network of pipes that generally has a loop structure to supply water from the service reservoirs and balancing reservoirs to consumers. [ 6 ]
A water distribution system consists of pipelines, storage facilities, pumps, and other accessories. [ 7 ]
Pipelines laid within public right of way called water mains are used to transport water within a distribution system. Large diameter water mains called primary feeders are used to connect between water treatment plants and service areas. Secondary feeders are connected between primary feeders and distributors . Distributors are water mains that are located near the water users, which also supply water to individual fire hydrants . [ 8 ] A service line is a small diameter pipe used to connect from a water main through a small tap to a water meter at user's location. There is a service valve (also known as curb stop ) on the service line located near street curb to shut off water to the user's location. [ 9 ]
Storage facilities, or distribution reservoirs, provide clean drinking water storage (after required water treatment process) to ensure the system has enough water to service in response to fluctuating demands ( service reservoirs ), or to equalize the operating pressure ( balancing reservoirs ). They can also be temporarily used to serve fire fighting demands during a power outage. The following are types of distribution reservoirs:
Storage facilities are typically located at the center of the service locations. Being at the central location reduces the length of the water mains to the services locations. This reduces the friction loss when water is transported over a water main. [ 4 ]
In general, a water distribution system can be classified as having a grid, ring, radial or dead end layout. [ 13 ]
A grid system follows the general layout of the road grid with water mains and branches connected in rectangles. With this topology, water can be supplied from several directions allowing good water circulation and redundancy if a section of the network has broken down. Drawbacks of this topology include difficulty sizing the system. [ 13 ]
A ring system has a water main for each road, and there is a sub-main branched off the main to provide circulation to customers. This topology has some of the advantages of a grid system, but it is easier to determine sizing. [ 13 ]
A radial system delivers water into multiple zones. At the center of each zone, water is delivered radially to the customers. [ 13 ]
A dead end system has water mains along roads without a rectangular pattern. It is used for communities whose road networks are not regular. As there are no cross-connections between the mains, water can have less circulation and therefore stagnation may be a problem. [ 13 ]
The integrity of the systems are broken down into physical, hydraulic, and water quality. [ 3 ]
The physical integrity includes concerns on the ability of the barriers to prevents contaminations from the external sources to get into water distribution systems. The deterioration can be caused by physical or chemical factors. [ 3 ]
The hydraulic integrity is an ability to maintain adequate water pressure inside the pipes throughout distribution systems. It also includes the circulation and length of time that the water travels within a distribution system which has impacts on the effectiveness of the disinfectants . [ 3 ]
The water quality integrity is a control of degradations as the water travels through distribution systems. The impacts of water quality can be caused by physical or hydraulic integrity factors. The water quality degradations can also take place within the distribution systems such as microorganism growth, nitrification , and internal corrosion of the pipes. [ 3 ]
Analyses are done to assist in design, operation, maintenance and optimization of water distribution systems. There are two main types of analyses: hydraulic, and water quality behavior as it flows through a water distribution system. [ 14 ] Optimizing the design of water distribution networks is a complex task. However, a large number of methods have already been proposed, mainly based on metaheuristics. [ 15 ] Employing mathematical optimization techniques can lead to substantial construction savings in these kinds of infrastructures. [ 16 ]
Hazards in water distribution systems can be in the forms of microbial, chemical and physical. [ 6 ]
Most microorganisms are harmless within water distribution systems. However, when infectious microorganisms enter the systems, they form biofilms and create microbial hazards to the users. Biofilms are usually formed near the end of the distribution where the water circulation is low. This supports their growth and makes disinfection agents less effective. Common microbial hazards in distribution systems come from contamination of human faecal pathogens and parasites which enter the systems through cross-connections , breaks, water main works, and open storage tanks. [ 6 ]
Chemical hazards are those of disinfection by-products , leaching of piping materials and fittings, and water treatment chemicals. [ 6 ]
Physical hazards include turbidity of water, odors, colors, scales which are buildups of materials inside the pipes from corrosions, and sediment resuspension. [ 6 ]
There are several bodies around the world that create standards to limit hazards in the distribution systems: NSF International in North America; European Committee for Standardization , British Standards Institution and Umweltbundesamt in Europe; Japanese Standards Association in Asia; Standards Australia in Australia; and Brazilian National Standards Organization in Brazil. [ 6 ]
Lead contamination in drinking water can be from leaching of lead that was used in old water mains, service lines, pipe joints, plumbing fittings and fixtures. According to WHO, the most significant contributor of lead in water in many countries is the lead service line. [ 6 ]
Water quality deteriorate due to corrosion of metal pipe surfaces and connections in distribution systems. Pipe corrosion shows in water as color, taste and odor, any of which may cause health concerns. [ 17 ]
Health issues relate to releases of trace metals such as lead, copper or cadmium into the water. Lead exposure can cause delays in physical and mental development in children. Long term exposure to copper may cause liver and kidney damage. High or long term exposure of cadmium may cause damage to various organs. Corrosion of iron pipes causes rusty or red water. Corrosion of zinc and iron pipes can cause metallic taste. [ 17 ]
Various techniques can be used to control internal corrosion, for example, pH level adjustment, adjustment of carbonate and calcium to create calcium carbonate as pipe surface coating, and applying a corrosion inhibitor . For example, phosphate products that form films over pipe surfaces is a type of corrosion inhibitor. This reduces the chance of leaching of trace metals from the pipe materials into the water. [ 18 ]
Hydrant flushing is the scheduled release of water from fire hydrants or special flushing hydrants to purge iron and other mineral deposits from a water main. Another benefit of using fire hydrants for water main flushing is to test whether water is supplied to fire hydrants at adequate pressure for fire fighting. During hydrant flushing, consumers may notice rust color in their water as iron and mineral deposits are stirred up in the process. [ 19 ]
After water mains are in service for a long time, there will be deterioration in structural, water quality, and hydraulic performance. Structural deterioration may be caused by many factors. Metal-based pipes develop internal and external corrosion, causing the pipe walls to thin or degrade. They can eventually leak or burst. Cement-based pipes are subject to cement matrix and reinforced steel deterioration. All pipes are subject to joint failures. Water quality deterioration includes scaling, sedimentation, and biofilm formation. Scaling is the formation of hard deposits on the interior wall of pipes. This can be a by-product of pipe corrosion combined with calcium in the water, which is called tuberculation. Sedimentation is when solids settle within the pipes, usually at recesses between scaling build-ups. When there is a change in the velocity of water flow (such as sudden use of a fire hydrant), the settled solids will be stirred up, causing water to be discolored. Biofilms can develop in highly scaled and thus rough-surfaced pipes where bacteria are allowed to grow, as the higher the roughness of the interior wall, the harder it is for disinfectant to kill the bacteria on the surface of the pipe wall. Hydraulic deterioration that affects pressures and flows can be a result of other deterioration that obstructs the water flow. [ 20 ]
When it is time for water main renewal, there are many considerations in choosing the method of renewal. This can be open-trench replacement or one of the pipeline rehabilitation methods. A few pipeline rehabilitation methods are pipe bursting , sliplining , and pipe lining . [ 20 ]
When an in-situ rehabilitation method is used, one benefit is the lower cost, as there is no need to excavate along the entire water main pipeline. Only small pits are excavated to access the existing water main. The unavailability of the water main during the rehabilitation, however, requires building a temporary water bypass system to serve as the water main in the affected area. [ 21 ] A temporary water bypass system (known as temporary bypass piping [ 22 ] ) should be carefully designed to ensure an adequate water supply to the customers in the project area. Water is taken from a feed hydrant into a temporary pipe. When the pipe crosses a driveway or a road, a cover or a cold patch should be put in place to allow cars to cross the temporary pipe. Temporary service connections to homes can be made to the temporary pipe. Among many ways to make a temporary connection, a common one is to connect the temporary service connection to a garden hose. The temporary pipe should also add temporary fire hydrants for fire protection. [ 23 ]
As water main work can disturb lead service lines , which can result in elevated lead levels in drinking water, it is recommended that when a water utility plans a water main renewal project, it should work with property owners to replace lead service lines as part of the project. [ 24 ]
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Water droplet erosion (WDE) is "a form of materials wear that is caused by the impact of liquid droplets with sufficiently high speed." [ 1 ] The phenomenon was furthermore previously known as liquid impingement erosion (LIE) .
The emphasis of discrete water droplets serves to distinguish the WDE problem from liquid jet erosion and cavitation. The impact pressures invoked by discrete water droplet impact have a range considerably higher than the stagnation pressure created by liquid jet.
The difference between WDE and cavitation erosion is the fact that WDE usually comprises a gaseous or vaporous phase containing discrete liquid droplets; while cavitation erosion is observed when a continual liquid phase carries separate gaseous bubbles or cavities inside it. [ 2 ]
Recently, Ibrahim & Medraj developed an analytical model to predict the threshold speed of water droplet erosion and verified it experimentally, a challenge having been attempted hitherto without success since the 1950s. [ 3 ]
For an extended period of time, many industries have encountered the problem of erosion due to water droplet impact, and it continues to reappear wherever rotation or movement of a component at high speed in a hydrometer environment is employed. Recently, with the use of larger wind turbine blades, the issue of erosion of the leading edge due to rain droplets has grown more grave. Aerodynamics efficiency of turbine blades is severely diminished due to leading-edge erosion, resulting in a considerable decrease in annual energy production. [ 4 ]
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Water extraction (also known as water withdrawal , water abstraction , and water intake ) is the process of taking water from any source, either temporarily or permanently, for flood control or to obtain water for, for example, irrigation . [ 1 ] [ 2 ] The extracted water could also be used as drinking water after suitable treatment.
Depending on the environmental legislation in the country, controls may be placed on extraction to limit the amount of water that can be removed. The over-extraction of water can lead to dry rivers or declining groundwater levels. [ 3 ]
The science of hydrogeology is used to determine safe water extraction levels. Water can go through dams that are used to regulate or stop water from coming though, creating hydroelectricity.
Saltwater intrusion is the movement of saline water into freshwater aquifers , which can lead to groundwater quality degradation, including drinking water sources, and other consequences. Saltwater intrusion can naturally occur in coastal aquifers, owing to the hydraulic connection between groundwater and seawater . Because saline water has a higher mineral content than freshwater, it is denser and has a higher water pressure. As a result, saltwater can push inland beneath the freshwater. [ 4 ] In other topologies, submarine groundwater discharge can push fresh water into saltwater.
Groundwater contamination of water is seen vastly through the high needs of irrigation, drinking, and to support organic life. Keeping contaminants at a minimum is at a high demand and treated using arsenic, chloride and other chemicals to extract the pollutants. Humans can be a direct cause of these pollutants through over extraction.
Certain leading causes for groundwater contamination comes from lowering water tables due to the over extraction of water and the water table not being able to recharge as quickly as needed. With this being said, polluted water from the surface (rivers and streams), makes its way into the groundwater more quickly and easily and results in a water quality problem due to the surface water pollution.
Land Subsidence
Land Subsidence is another effect linked to the over extraction of groundwater. When large amounts of groundwater is extracted from aquifers beneath, surrounding areas above. When water from the aquifer is extracted at a large amount, the sediment, certain rock types, is separated due to the lack of water being used to make sure the sediment stays tightly together. The over extraction of groundwater is a human caused activity that causes these ground failures that create pore spaces where water once was occupying. The sudden sinking of the soils surface causes infrastructure damage and a higher risk of flood damage due to the displacement of the Earth's surface.
Groundwater laws contain the information revolving around the rights of water extraction and the withdrawals from aquifers in the United States that is measured. Most of the groundwater that is mainly withdrawn or extracted from aquifers consist of primarily irrigation towards the Southwest and the West with close to 85 to 90 withdrawn.
With an expected increase of the demand of water for domestic usage in the future, systems are to be regulated and land rights vary on the consumption of groundwater rights. When requirements haven't been met through the water extraction, States water resources control and take steps on authorization of the requirements for groups of individuals or corporations.
6. Bagley, E. S. (1961). Water rights law and public policies relating to ground water “mining” in the Southwestern States. The Journal of Law and Economics , 4 , 144–174. https://doi.org/10.1086/466576
7. Infinite Water Holdings Limited. (n.d.). Groundwater Contamination & Treatment Solutions . Infinite Water. https://www.infinitewater.com/articles/groundwater-contamination-treatment-solutions
8. Water School Science. (n.d.). Land subsidence completed . Land Subsidence | U.S. Geological Survey. https://www.usgs.gov/special-topics/water-science-school/science/land-subsidence
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Water filling algorithm is a general name given to the ideas in communication systems design and practice for equalization strategies on communications channels . As the name suggests, just as water finds its level even when filled in one part of a vessel with multiple openings, as a consequence of Pascal's law , the amplifier systems in communications network repeaters, or receivers amplify each channel up to the required power level compensating for the channel impairments. See, for example, channel power allocation in MIMO systems.
In a single channel communication system the deamplification and loss present on them can be simplistically taken as attenuation by a percentage g , then amplifiers restore the signal power level to the same value at transmission setup by operating at a gain of 1/ (1 − g ). E.g. if we experience 6 dB attenuation in transmission, i.e. 75% loss, then we have to amplify the signal by a factor of 4 x to restore the signal to the transmitter levels.
Same ideas can be carried out in presence impairments and a multiple channel system. Amplifier nonlinearity, crosstalk and power budgets prevent the use of these waterfilling algorithms to restore all channels, and only a subset can benefit from them.
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Water gas is a kind of fuel gas , a mixture of carbon monoxide and hydrogen . It is produced by "alternately hot blowing a fuel layer [coke] with air and gasifying it with steam". [ 1 ] [ 2 ] The caloric yield of the fuel produced by this method is about 10% of the yield from a modern syngas plant. The coke needed to produce water gas also costs significantly more than the precursors for syngas (mainly methane from natural gas), making water gas technology an even less attractive business proposition.
Synthesis gas is made by passing steam over a red-hot carbon fuel such as coke : [ 3 ]
The reaction is endothermic , so the fuel must be continually re-heated to maintain the reaction. To do this, an air stream, which alternates with the vapor stream, is introduced to combust some of the carbon:
Theoretically, to make 6 L of water gas, 5 L of air is required. Alternatively, to prevent contamination with nitrogen, energy can be provided by using pure oxygen to burn carbon into carbon monoxide.
In this case, 1 L of oxygen will create 5.3 L of pure water gas.
The water-gas shift reaction was discovered by Italian physicist Felice Fontana in 1780. [ 4 ] [ 5 ] Water gas was made in England from 1828 by blowing steam through white-hot coke. [ 6 ]
Hydrocarbonate is an archaic term for water gas composed of carbon monoxide and hydrogen generated by passing steam through glowing coke . Hydrocarbonate was classified as a factitious air and explored for therapeutic properties by some eighteenth-century physicians, including Thomas Beddoes and James Watt . [ 7 ] The term hydrocarbonate, coined by Beddoes in 1794, should not be confused with the modern name "hydrogen carbonate" for bicarbonate ion.
Between 1794 and 1802, physicians such as Tiberius Cavallo and Davies Gilbert experimented with hydrocarbonate as an analgesic and anesthetic. [ 8 ] Humphry Davy infamously inhaled three quarts of hydrocarbonate at the Pneumatic Institution and nearly died upon "sinking into annihilation"; Davy recovered two days later and concluded inhalation of more hydrocarbonate could have "destroyed life immediately without producing any painful sensations". [ 9 ] He was right: carbon monoxide poisoning can be fatal.
Diseases treated by hydrocarbonate included: tuberculosis , inflammation , asthma , expectoration , hemoptysis , pneumonia , hydrothorax , spasm and other indications. [ 7 ] [ 8 ] Many of the diseases treated with hydrocarbonate, whose active ingredient was carbon monoxide, are now being investigated using modern biomedical research methods to determine the therapeutic potential of carbon monoxide. For example, James Lind recognized hydrocarbonate to effectively treat lung inflammation; [ 7 ] delivery of carbon monoxide via inhalation protocol or carbon monoxide-releasing molecules has significant preclinical data indicating an effective treatment for inflammation. [ 10 ] The pioneering work of exploratory medicinal application of hydrocarbonate is an important origin for modern drug development.
James Watt suggested hydrocarbonate could act as "an antidote to the oxygen in blood" in 1794 and cautioned about the toxicity of an overdose prior to the discoveries of carbon monoxide (1800) and hemoglobin (1840). [ 7 ] Despite Watt's observation, it is widely accepted that Claude Bernard had first described the mechanism for carbon monoxide poisoning by describing carbon monoxide's affinity for hemoglobin displacing oxygen to induce asphyxia circa 1857. [ 11 ]
In 1873, Thaddeus S. C. Lowe developed and patented the water gas process by which large amounts of hydrogen gas could be generated for residential and commercial use in heating and lighting. This gas provided a more efficient heating fuel than the common coal gas , or coke gas, which was used in municipal service. The process used the water-gas shift reaction:
The process was discovered by passing high-pressure steam over hot coal , the major source of coke gas. Lowe's process improved upon the chimney systems by which the coal could remain superheated, thereby maintaining a consistently high supply of the gas. The reaction produced carbon dioxide and hydrogen, which, after a process of cooling and " scrubbing ", produced hydrogen gas.
The process spurred on the industry of gas manufacturing, and gasification plants were established quickly along the eastern seaboard of the United States. Similar processes, like the Haber–Bosch process , led to the manufacture of ammonia (NH 3 ) by the combining of nitrogen , found in air , with hydrogen. This spurred on the refrigeration industry, which long used ammonia as its refrigerant . Lowe also held several patents on artificial ice making machines and was able to run successful businesses in cold storage, as well as products which operated on hydrogen gas.
Water gas has a lower heat of combustion than coal gas , so the calorific value was often boosted by passing the gas through a heated retort , into which oil was sprayed. The resulting mixed gas was called carburetted water gas . The average composition of carburetted water gas is as follows: 34–38% H 2 ; 23–28% CO; 17–21% saturated hydrocarbons; 13–16% unsaturated hydrocarbons; 0.2–2.2% CO 2 ; 2.5–5.0% N 2 . It is used as a source of heat, since it has a high calorific value.
Semi-water gas is a mixture of water gas and producer gas made by passing a mixture of air and steam through heated coke. The heat generated when producer gas is formed keeps the temperature of the coke high enough to allow water gas to be formed.
Pure hydrogen can be obtained from water gas by using the Water–gas shift reaction , after subsequent removal of the carbon dioxide formed when carbon monoxide reacts with water.
Completely displaced by syngas, water gas could be applied to certain fuel cells. Used in Fischer–Tropsch process . It reacts with producer gas to produce fuel gas . It could also be used to gain pure hydrogen for synthesis of ammonia.
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In light microscopy , a water immersion objective is a specially designed objective lens used to increase the resolution of the microscope. This is achieved by immersing both the lens and the specimen in water which has a higher refractive index than air, thereby increasing the numerical aperture of the objective lens.
Water immersion objectives are used not only at very large magnifications that require high resolving power, but also of moderate power as there are water immersion objectives as low as 4X. Objectives with high power magnification have short focal lengths , facilitating the use of water. The water is applied to the specimen (conventional microscope), and the stage is raised, immersing the objective in water. Sometimes with water dipping objectives, the objective is directly immersed in the solution of water which contains the specimens to look at. Electrophoretic preparations used in the case of comet assay can benefit from the use of water objectives.
The refractive index of the water (1.33) is closer to those of imaged materials or to the glass of the cover-slip, so more light will be collected/focused by this type of objective comparing to air-immersion ones, leading to a range of higher numerical apertures (NA). [ 1 ]
Unlike oil, water does not have the same or near identical refractive value as the cover slip glass, so a correction collar is needed to be able to variate for its thickness. Lenses without a correction collar generally are made for the use of a 0.17 mm cover slip or for use without a coverslip (dipping lens). [ 1 ]
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The water industry provides drinking water [ 1 ] and wastewater services (including sewage treatment ) to residential, commercial, and industrial sectors of the economy . Typically public utilities operate water supply networks . The water industry does not include manufacturers and suppliers of bottled water , which is part of the beverage production and belongs to the food sector .
The water industry includes water engineering , operations, water and wastewater plant construction, equipment supply and specialist water treatment chemicals, among others.
The water industry is at the service of other industries, e.g. of the food sector which produces beverages such as bottled water. [ 2 ]
There are a variety of organizational structures for the water industry, with countries usually having one dominant traditional structure, which usually changes only gradually over time. [ 3 ]
Water quality standards and environmental standards relating to wastewater are usually set by national bodies.
Using available data only, and during 2009 - 2010, the ten largest water companies active globally were (largest first) : [ 7 ] Veolia Environnement (France), Suez Environnement (France), ITT Corporation (US), United Utilities (UK), Severn Trent (UK), Thames Water (UK), American Water Works Company (US), GE Water (US), Kurita Water Industries (Japan), Nalco Water (US).
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A water jacket furnace is a type of blast furnace used to smelt non-ferrous metallic ores, most typically ores of copper, lead, or silver-lead. It takes its name from the water jacket arrangement used to cool the lower furnace casing and prolong the life of the furnace hearth. It is sometimes referred to as a water-jacketed blast furnace , copper blast furnace , or lead blast furnace . The water jacket furnace is now virtually an obsolete technology for copper smelting , being nearly entirely replaced, by flash smelting of copper ore concentrates . It remains in use, in a modified form, for lead smelting .
The terminology is also used for an indirect heating device used in the petroleum oil and gas industry, generally known as a water jacket heater [ 1 ] or water bath heater, which should not be confused with the metallurgical water jacket furnace.
In the mid 19th Century, most non-ferrous smelting was done using reverberatory furnaces . Blast furnaces were used to smelt sulphide copper ore in the Harz Mountains of Germany. The mines at Burra in South Australia tried to adopt the technology, in 1847, but without success because the German furnace design, using horse-powered bellows to provide the air blast, was not well suited to their carbonate copper ore. [ 2 ]
The 'water jacket' blast furnace design for non-ferrous smelting arose in North America, during the 1870s, [ 3 ] and an alternative name for it, in Australia, was 'American water jacket furnace'. [ 4 ] The design evolved from earlier German cupola furnace designs, with the distinguishing innovation being a well-controlled cooling of the furnace shell. [ 3 ]
Water jacket furnaces began to be common in the later part of the century, from the 1880s, particularly for smelting sulphide ores. Unlike reverberatory furnaces, water jacket furnaces could be made in a factory and then assembled at site. [ 3 ]
Not all situations and ores were well-suited to water jacket furnace operation. Some attempts to apply them were costly failures, such as at the North Lyell mine, at Crotty, Tasmania , [ 5 ] and Lloyd's Mine at Burraga [ 6 ] and the Overflow Mine at Bobadah , both in New South Wales . [ 7 ] However, the furnaces were hugely successful, when well applied, such as at the vast Anaconda Copper Mine , in Butte, Montana , the Mt Lyell Mine in Tasmania , [ 5 ] and at many other mines.
Water jacket furnaces only ever partially displaced reverberatory furnaces in the copper industry, until both furnace types were displaced, almost entirely, by flash smelting , between around 1949 and 1980. [ 8 ]
A water jacket furnace can be used to reduce non-ferrous oxide ores mixed with coke, to produce metal and slag. When smelting lead, the feedstock is lead oxide, coke and fluxes. When smelting lead sulphide ores, the ore is first sintered to form a lead oxide sinter. Lead and silver ores often occur in the same ore body. Separating silver metal from the crude lead produced by a furnace requires a second process of refining, such as the Parkes process . When smelting lead, there was the added complication that measures were necessary to protect workers from harmful lead vapours.
The pyrometallurgical process of a water jacket furnace, when smelting copper sulphide ores, was fundamentally different to a conventional blast furnace used to make iron, or a water jacket furnace used to make lead. The conventional blast furnace process produces molten metal by reducing the ore, and separating out the silica as slag. Water jacket furnaces, when smelting sulphide copper ores, used an oxidation reaction that produces molten copper matte , which must be further treated in a convertor (similar in concept to a Bessemer convertor ) or reverberatory furnace to produce copper metal. The product of that conversion process is known as blister copper. [ 3 ] If a smelter did not have a convertor, the matte was poured into moulds and allowed to solidify.
The smelting of sulphide copper ores in a water jacket furnace can be viewed as concentrating the non-ferrous metallic portion of the ore, as matte, and separating out some impurities, such as silica and iron, in the mainly iron silicate slag, and much of the sulphur, as sulphur dioxide in the off-gas. The molten slag and matte separate, with the denser molten matte accumulating at the bottom of the furnace, with a layer of molten slag immediately above it. [ 3 ]
Depending upon the composition of the ore being smelted, the choice of a suitable flux was particularly important. [ 9 ] Fluxes used could be limestone , iron oxide , or silica ( quartz ), depending upon what was needed to create slag and to minimise the loss of copper with that slag. When both 'basic' (oxide or carbonate) ores and 'siliceous' sulphide ores were available, feeding the furnaces with a mixture of the two copper ore types reduced the amount of other fluxes needing to be added. [ 10 ] [ 11 ]
Water jacket furnaces had some advantages over reverberatory furnaces . Fuel consumption was lower. Sulphide copper ores could be smelted without first roasting the ore. Production per furnace was generally higher. Low grade ore could be smelted, because the water jacket furnace could more readily discharge large amounts of molten slag . Because solidified slag is unsuitable to backfill the voids ( stopes ) created by underground mining, disposal of large volumes of slag, from smelting of low grade ores, was a significant problem. Some mines treated molten slag with water to create granulated slag, which could be used to backfill stopes. [ 12 ] Otherwise, the molten slag was dumped and large slag dumps accumulated near the smelter, becoming a lasting legacy of smelting operations. [ 13 ]
Another advantage of the water jacket furnace was that, while out of service, the bottom of the furnace, if so designed, could be 'dropped' for cleaning it up or for repair. Over time, a significant amount of copper material would accumulate in the bottom of a reverberatory furnace which could not be accessed without effectively demolishing the furnace. [ 14 ]
A disadvantage of the water jacket furnace was that it could not handle fine ore well and was so was better suited to lump ore. Fines tended to either choke the furnace or were blown into the flue by the air blast. Eventually, the second problem, only, would be solved by capturing the flue dust and recycling it. [ 3 ]
An initial disadvantage of the water jacket furnace was its use of coke as fuel. It could not use the cheaper fuels such as firewood or fine raw coal that could be used to fire a reverberatory furnace. That disadvantage was offset by lower overall fuel consumption. In the first years of the 20th Century, the perfection of a technique known as pyritic smelting greatly reduced coke consumption, when smelting suitable ores such as chalcopyrite , by optimizing the use of the sulphur and iron in the ore itself, as a fuel generating heat. [ 15 ] [ 16 ] The iron oxide so produced combined with molten silica to form an iron silicate slag. [ 16 ]
Water jacket furnaces needed blowers and a cooling water supply, and were more complex to build and operate than the reverberatory furnaces. However, they were also more versatile, being a readily scalable technology; large or small furnaces could be made, and would operate effectively. [ 3 ]
Water jacket furnaces, like other blast furnaces, are best operated continuously, and smelters that used them had to work continuously too. However, this was in one way an advantage over reverberatory furnaces that operated as a batch process with around 24 hours typical duration. The associated cycles of heating and cooling of a reverberatory furnace led, over time, to damage of its masonry and higher maintenance and downtime as a result. [ 17 ] In contrast, a well-operated water jacket furnace might achieve years of operation before needing new fire bricks . [ 3 ]
The internal operating temperature of the water jacket furnace is lower than that of a blast furnace used to make iron, and the process does not depend upon the formation of a bosh shell, as is critical in the operation of a blast furnace making iron.
Conventional blast furnaces used for smelting iron ore use a hot blast . Water jacket furnaces most commonly used a cold air blast , typically provided by a positive-displacement blower, such as a Roots blower . Preheating of the air blast was used on some water jacket furnaces, but preheating of the blast had no advantage when the furnace was being used for pyritic smelting of copper ore. [ 18 ] [ 19 ]
The horizontal cross-section of water jacket furnaces was usually rectangular—although circular and oval cross-section ones did exist [ 4 ] —whereas conventional blast furnaces making iron always have a circular horizontal cross-section. In some larger furnace designs, molten metal / matte and molten slag were tapped at the opposite narrow ends of the rectangular base. Water jacket furnaces typically have a higher number of smaller tuyeres than a conventional iron-making blast furnace.
Typically, feedstock was fed into a water jacket furnace through a sliding door arrangement in the side of the upper furnace structure, [ 18 ] [ 4 ] but not via the top itself as in a blast furnace for iron. At the top of a water jacket furnace was a fixed flue. The off-gas from copper smelting was not suitable to be recycled as a fuel, as is done in a blast furnace making iron ( blast furnace gas ). However, the sulphur dioxide in the flue gases, from those furnaces using the pyritic smelting process, was concentrated enough that it could be used to make sulphuric acid , which reduced the level of air pollution created by the smelter. [ 20 ] If the flue gas needed to be dispersed to the atmosphere, a tall chimney was necessary. [ 21 ] to ensure that the noxious gases from smelting, largely sulphur dioxide , were carried far from the smelter and any nearby settlement. Dust carried in the flue gas was often collected, as it had a significant metallic content. [ 22 ] A furnace smelting lead uses a reduction reaction; it generates an off-gas containing carbon monoxide, similar to blast furnace gas, which needs to be disposed of, usually by flaring .
In contrast to a conventional blast furnace used to make iron, lead metal or copper matte and slag were run off more or less continuously. There was a separate slag spout to run off slag. The molten copper matte run from such a furnace, under this arrangement, still contained a proportion of slag. The copper matte was run first into a vessel known as a 'settler' to allow any slag to accumulate on the surface, from where it could overflow from the settler. From tap holes at the bottom of the settler, the molten matte was run into ladles, which were used to transport the matte to a convertor, where it was processed to make blister copper. [ 22 ] The 'settler' presented a hazard to furnace operators. [ 23 ]
A variant of the water jacket furnace was used to smelt lead-zinc ores using the Imperial Smelting Process . In that case, the furnace was completely sealed, to allow the zinc to be recovered, from flue gases, in its vapour phase . [ 24 ]
Water jacket furnaces were used to reprocess copper smelter slag that still contained a significant amount of copper, especially slag from smelting high-grade copper ore in reverberatory furnaces.
Although rarely done, small water jacket furnaces have been used to recover gold from quartz rock—particularly if the ore was very rich in gold or sulphide ores of other metals were also present—as an alternative to crushing the rock and extracting the gold using other methods. [ 25 ] [ 26 ] However, it was a very inefficient method of extracting gold. [ 27 ]
Where gold and silver were present in copper ores, the precious metals were present in the copper matte produced by a water jacket furnace. The precious metals could later be separated from blister copper, using electrolytic copper refining, and delivered in the form of dore bullion .
As the average ore grades of copper mines declined, ore smelting became uneconomic. Smelters such as the Great Cobar mine were struggling to achieve economic operation, as early as 1912, despite buoyant copper prices. [ 28 ]
Smelting of low-grade copper ore at the mine site was largely superseded by a process consisting of copper ore concentration, especially using froth flotation , and smelting of ore concentrates . The water jacket furnace was less well suited to that new regime—especially large ones that had been used to smelt low grade copper ores—and, after the introduction of flash smelting , from around 1949, had fallen out of favour by 1980. [ 8 ]
Water jacket furnaces are now a largely forgotten technology for copper smelting, [ 8 ] but remain in use, in a modified form, for lead smelting. [ 29 ] Modern lead furnaces are more commonly referred to as lead blast furnaces, but retain most features of water jacket furnaces.
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Water level , also known as gauge height or stage , is the elevation of the free surface of a sea , stream , lake or reservoir relative to a specified vertical datum . [ 1 ] Over long distances, neglecting external forcings (such as wind), water level tends to conform to an equigeopotential surface. [ 2 ]
This hydrology article is a stub . You can help Wikipedia by expanding it .
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An oceanographic water mass is an identifiable body of water with a common formation history which has physical properties distinct from surrounding water. Properties include temperature , salinity , chemical - isotopic ratios, and other physical quantities which are conservative flow tracers . Water mass is also identified by its non-conservative flow tracers such as silicate, nitrate, oxygen, and phosphate.
Water masses are generally distinguished not only by their respective tracers but also by their location in the Worlds' oceans. Water masses are also distinguished by their vertical position so that there are surface water masses, intermediate water masses and deep water masses.
Common water masses in the world ocean are:
Although there are many types of water masses, they all share characteristics. Water Masses are formed from regions of water having different temperatures. When ice is being formed in a cold climate like Antarctica, the cold temperatures separate the molecular bonds of the water causing it to become less dense. However, because water increases its volume by about 9% when frozen, this makes the ice less dense than the water which is why glaciers float. This also in turn causes the salinity of the water to decrease. The salinity of the water makes water freeze at lower temperatures than freshwater. Freshwater freezes at the standard 0 °C (32 °F), while saltwater freezes at an average of -2 °C (28.4 °F).
The best method of classifying a water mass is through using a T-S diagram. In the diagram pictured at the top, it categorises a water mass by the temperature and salinity of the water and is represented by a single point. However, water masses are not constant. Throughout time climates can change, seasons can drag out, or there could be less rainfall meaning that the water masses might change in temperature or salinity. To have a complete water mass classification, it requires the water type of the source and the standard deviations of the temperature and salinity. It can take many years to establish the standard deviations of the water mass and requires constant surveillance. Once all of the necessary measures are completed, the data will now determine what the current density of the water is and help further classify the water mass.
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Water memory is the purported ability of water to retain a memory of substances previously dissolved in it even after an arbitrary number of serial dilutions . It has been claimed to be a mechanism by which homeopathic remedies work, even when they are diluted to the point that no molecule of the original substance remains, but there is no theory for it.
Water memory is pseudoscientific in nature; it contradicts the scientific understanding of physical chemistry and is generally not accepted by the scientific community . In 1988, Jacques Benveniste and colleagues published a study supporting a water memory effect amid controversy in Nature , [ 1 ] accompanied by an editorial by Nature ' s editor John Maddox [ 2 ] urging readers to "suspend judgement" until the results could be replicated. In the years after publication, multiple supervised experiments were made by Benveniste's team, the United States Department of Defense , [ 3 ] BBC's Horizon programme, [ 4 ] and other researchers, but no one has ever reproduced Benveniste's results under controlled conditions.
Jacques Benveniste was a French immunologist who sought to demonstrate the plausibility of homeopathic remedies "independently of homeopathic interests" in a major scientific journal. [ 5 ] To that end, Benveniste and his team at Institut National de la Santé et de la Recherche Médicale (INSERM, French for National Institute of Health and Medical Research) diluted a solution of human antibodies in water to such a degree that there was virtually no possibility that a single molecule of the antibody remained in the water solution.
Nonetheless, they reported, human basophils responded to the solutions just as though they had encountered the original antibody (part of the allergic reaction ). The effect was reported only when the solution was shaken violently during dilution. [ 1 ] Benveniste stated: "It's like agitating a car key in the river, going miles downstream, extracting a few drops of water, and then starting one's car with the water." [ 6 ] At the time, Benveniste offered no theoretical explanation for the effect, which was later coined as "water memory" by a journalist reporting on the study. [ 7 ] [ self-published source? ]
While Benveniste's study demonstrated a mechanism by which homeopathic remedies could operate, the mechanism defied scientific understanding [ clarification needed ] of physical chemistry . [ 6 ] [ 8 ] [ 9 ] A paper about hydrogen bond dynamics [ 10 ] is mentioned by some secondary sources [ 11 ] [ 12 ] in connection to the implausibility of water memory.
Benveniste submitted his research to the prominent science journal Nature for publication. There was concern on the part of Nature's editorial oversight board that the material, if published, would lend credibility to homeopathic practitioners even if the effects were not replicable. [ 6 ] There was equal concern that the research was simply wrong, given the changes that it would demand of the known laws of physics and chemistry. The editor of Nature , John Maddox , stated that, "Our minds were not so much closed as unready to change our whole view of how science is constructed." [ 6 ] Rejecting the paper on any objective grounds was deemed unsupportable, as there were no methodological flaws apparent at the time.
In the end, a compromise was reached. The paper was published in Nature Vol. 333 on 30 June 1988, [ 1 ] but it was accompanied with an editorial by Maddox that noted "There are good and particular reasons why prudent people should, for the time being, suspend judgement" and described some of the fundamental laws of chemistry and physics which it would violate, if shown to be true. [ 8 ] Additionally, Maddox demanded that the experiments be re-run under the supervision of a hand-picked group of what became known as "ghostbusters", including Maddox, famed magician and paranormal researcher James Randi , and Walter W. Stewart , a chemist and freelance debunker at the U.S. National Institutes of Health . [ 13 ]
Under supervision of Maddox and his team, Benveniste and his team of researchers followed the original study's procedure and produced results similar to those of the first published data. Maddox, however, noted that during the procedure, the experimenters were aware of which test tubes originally contained the antibodies and which did not. Benveniste's team then started a second, blinded experimental series with Maddox and his team in charge of the double-blinding : notebooks were photographed, the lab videotaped, and vials juggled and secretly coded. Randi even went so far as to wrap the labels in newspaper, seal them in an envelope, and then stick them on the ceiling. This was done so that Benveniste and his team could not read them. [ 14 ] The blinded experimental series showed no water memory effect.
Maddox's team published a report on the supervised experiments in the next issue (July 1988) of Nature . [ 15 ] Maddox's team concluded "that there is no substantial basis for the claim that anti-IgE at high dilution (by factors as great as 10 120 ) retains its biological effectiveness, and that the hypothesis that water can be imprinted with the memory of past solutes is as unnecessary as it is fanciful." Maddox's team initially speculated that someone in the lab "was playing a trick on Benveniste", [ 6 ] but later concluded that, "We believe the laboratory has fostered and then cherished a delusion about the interpretation of its data." Maddox also pointed out that two of Benveniste's researchers were being paid by the French homeopathic company Boiron . [ 15 ]
In a response letter published in the same July issue of Nature , Benveniste lashed out at Maddox and complained about the "ordeal" that he had endured at the hands of the Nature team, comparing it to " Salem witchhunts or McCarthy -like prosecutions". [ 16 ] Both in the Nature response and during a later episode of Quirks and Quarks , Benveniste especially complained about Stewart, who he claimed acted as if they were all frauds and treated them with disdain, complaining about his "typical know-it-all attitude". In his Nature letter, Benveniste also implied that Randi was attempting to hoodwink the experimental run by doing magic tricks, "distracting the technician in charge of its supervision!" He was more apologetic on Quirks and Quarks , re-phrasing his mention of Randi to imply that he had kept the team amused with his tricks and that his presence was generally welcomed. He also pointed out that although it was true two of his team members were being paid by a homeopathic company, the same company had paid Maddox's team's hotel bill.
Maddox was unapologetic, stating "I'm sorry we didn't find something more interesting." On the same Quirks and Quarks show, he dismissed Benveniste's complaints, stating that, because of the possibility that the results would be unduly promoted by the homeopathy community, an immediate re-test was necessary. The failure of the tests demonstrated that the initial results were likely due to the experimenter effect . He also pointed out that the entire test procedure, that Benveniste later complained about, was one that had been agreed upon in advance by all parties. It was only after the test had failed that Benveniste disputed its appropriateness.
The debate continued in the letters section of Nature for several issues before being ended by the editorial board. It continued in the French press for some time, [ 17 ] and in September Benveniste appeared on the British television discussion programme After Dark to debate the events live with Randi and others. In spite of all the arguing over the retests, it had done nothing to stop what Maddox worried about: even in light of the tests' failure, they were still being used to claim that the experiments "prove" that homeopathy works. One of Benveniste's co-authors on the Nature paper, Francis Beauvais, later stated that while unblinded experimental trials usually yielded "correct" results ( i.e. ultradiluted samples were biologically active, controls were not), "the results of blinded samples were almost always at random and did not fit the expected results: some 'controls' were active and some 'active' samples were without effect on the biological system." [ 18 ]
In the cold fusion or polywater controversies, many scientists started replications immediately, because the underlying theories did not go directly against scientific fundamental principles and could be accommodated with a few tweaks to those principles. [ 19 ] But Benveniste's experiment went directly against several principles, causing most researchers to outright reject the results as errors or fabrication, with only a few researchers willing to perform replications or experiments that could validate or reject his hypotheses. [ 19 ]
After the Nature controversy, Benveniste gained the public support of Brian Josephson , [ 20 ] a Nobel laureate physicist with a reputation for openness to paranormal claims. Experiments continued along the same basic lines, culminating with a 1997 paper claiming the effect could be transmitted over phone lines. [ 21 ] This was followed by two additional papers in 1999 [ 22 ] and another from 2000, in the controversial non- peer reviewed Medical Hypotheses , on remote-transmission, by which time it was claimed that it could also be sent over the Internet . [ 23 ]
Time magazine reported in 1999 that, in response to skepticism from physicist Robert Park , Josephson had challenged the American Physical Society (APS) to oversee a replication by Benveniste. This challenge was to be "a randomized double-blind test", of his claimed ability to transfer the characteristics of homeopathically altered solutions over the Internet: [ 24 ]
[Benveniste's] latest theory, and the cause of the current flap, is that the "memory" of water in a homeopathic solution has an electromagnetic "signature." This signature, he says, can be captured by a copper coil, digitized and transmitted by wire—or, for extra flourish, over the Internet—to a container of ordinary water, converting it to a homeopathic solution.
The APS accepted the challenge and offered to cover the costs of the test. When he heard of this, Randi offered to throw in the long-standing $1 million prize for any positive demonstration of the paranormal, to which Benveniste replied: "Fine to us." [ 25 ] In his DigiBio NewsLetter . Randi later noted that Benveniste and Josephson did not follow up on their challenge, mocking their silence on the topic as if they were missing persons. [ 26 ]
An independent test of the 2000 remote-transmission experiment was carried out in the US by a team funded by the United States Department of Defense . Using the same experimental devices and setup as the Benveniste team, they failed to find any effect when running the experiment. Several "positive" results were noted, but only when a particular one of Benveniste's researchers was running the equipment. "We did not observe systematic influences such as pipetting differences, contamination, or violations in blinding or randomization that would explain these effects from the Benveniste investigator. However, our observations do not exclude these possibilities."
Benveniste admitted to having noticed this himself. "He stated that certain individuals consistently get digital effects and other individuals get no effects or block those effects." [ 27 ]
Third-party attempts at replication of the Benveniste experiment to date have failed to produce positive results that could be independently replicated. In 1993, Nature published a paper describing a number of follow-up experiments that failed to find a similar effect, [ 28 ] and an independent study published in Experientia in 1992 showed no effect. [ 29 ] An international team led by Madeleine Ennis of Queen's University of Belfast claimed in 1999 to have replicated the Benveniste results. [ 30 ] [ 31 ] Randi then forwarded the $1 million challenge to the BBC Horizon program to prove the "water memory" theory following Ennis's experimental procedure. In response, experiments were conducted with the vice-president of the Royal Society , John Enderby, overseeing the proceedings. The challenge ended with no memory effect observed by the Horizon team. [ 4 ] For a piece on homeopathy, the ABC program 20/20 also attempted, unsuccessfully, to reproduce Ennis's results. [ 32 ] Ennis has claimed that these tests did not follow her own experiment protocols. [ 33 ]
In 2003, Louis Rey, a chemist from Lausanne , reported that frozen samples of lithium and sodium chloride solutions prepared according to homeopathic prescriptions showed – after being exposed to radiation – different thermoluminescence peaks compared with pure water. Rey claimed that this suggested that the networks of hydrogen bonds in homeopathic dilutions were different. [ 34 ] These results have never been replicated and are not generally accepted - even Benveniste criticised them, pointing out that they were not blinded. [ 35 ]
In January 2009, Luc Montagnier , the Nobel Laureate virologist who led the team that discovered the human immunodeficiency virus (HIV), claimed (in a paper published in a journal that he set up, which seems to have avoided conventional peer review as it was accepted three days after submission) that the DNA of pathogenic bacteria and viruses massively diluted in water emit radio waves that he can detect. [ 36 ] The device used to detect these signals was developed by Jacques Benveniste, and was independently tested, with the co-operation of the Benveniste team, at the request of the United States Defense Advanced Research Projects Agency . That investigation was unable to replicate any effects of digital signals using the device. [ 37 ]
In 2010, at the age of 78, Montagnier announced that he would take on the leadership of a new research institute at Jiaotong University in Shanghai, where he plans to continue this work. He claims that the findings "are very reproducible and we are waiting for confirmation by other labs", but said, in an interview with Science , "There is a kind of fear around this topic in Europe. I am told that some people have reproduced Benveniste's results, but they are afraid to publish it because of the intellectual terror from people who don't understand it." Montagnier had called Benveniste "a modern Galileo ", but the problem was that "his results weren't 100% reproducible". [ 38 ]
To most scientists, the "memory of water" is not something that deserves serious consideration; the only evidence is the flawed Benveniste work. By contrast, the notion of "memory of water" has been taken seriously among homeopaths . For them, it seemed to explain how some of their remedies might work.
An overview of the issues surrounding the memory of water was the subject of a special issue of Homeopathy. In an editorial, the editor of Homeopathy , Peter Fisher , acknowledged that Benveniste's original method does not yield reproducible results and declared "...the memory of water is a bad memory: it casts a long shadow over homeopathy and is just about all that many scientists recall about the scientific investigation of homeopathy, equating it with poor or even fraudulent science." The issue was an attempt to restore some credibility to the notion with articles proposing various, very different theories of water memory, such as electromagnetic exchange of information between molecules, breaking of temporal symmetry , thermoluminescence , entanglement described by a new quantum theory, formation of hydrogen peroxide , clathrate formation, etc. Some of the proposed mechanisms would require overthrowing much of 20th-century physics. [ 39 ]
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Water metering is the practice of measuring water use . Water meters measure the volume of water used by residential and commercial building units that are supplied with water by a public water supply system. They are also used to determine flow through a particular portion of the system.
In most of the world water meters are calibrated in cubic metres (m 3 ) or litres, [ 1 ] but in the United States and some other countries water meters are calibrated in cubic feet (ft 3 ) or US gallons on a mechanical or electronic register. Modern meters typically can display rate-of-flow in addition to total volume.
Several types of water meters are in common use, and may be characterized by the flow measurement method, the type of end-user, the required flow rates, and accuracy requirements.
Water metering is changing rapidly with the advent of smart metering technology and various innovations.
In North America, standards for manufacturing water meters are set by the American Water Works Association . Outside of North America, most countries use ISO standards .
There are two common approaches to flow measurement : displacement and velocity , each making use of a variety of technologies. Common displacement designs include oscillating piston and nutating disc meters. Velocity-based designs include single- and multi-jet meters and turbine meters.
There are also non-mechanical designs, for example, electromagnetic and ultrasonic meters, and meters designed for special uses. Most meters in a typical water distribution system are designed to measure cold potable water only. Specialty hot water meters are designed with materials that can withstand higher temperatures. Meters for reclaimed water have special lavender register covers to signify that the water should not be used for drinking.
Additionally, there are electromechanical meters, like prepaid water meters and automatic meter reading meters. The latter integrates an electronic measurement component and a LCD with a mechanical water meter. Mechanical water meters normally use a reed switch, hall or photoelectric coding register as the signal output. After processing by the microcontroller unit (MCU) in the electronic module, the data are transmitted to the LCD or output to an information management system.
Water meters are generally owned, read and maintained by a public water provider such as a city, rural water association or private water company . In some cases an owner of a mobile home park, apartment complex or commercial building may be billed by a utility based on the reading of one meter, with the costs shared among the tenants based on some sort of key (size of flat, number of inhabitants or by separately tracking the water consumption of each unit in what is called submetering ).
Displacement meters are commonly referred to as Positive Displacement , or "PD" meters. Two common types are oscillating piston meters and nutating disk meters. Either method relies on the water to physically displace the moving measuring element in direct proportion to the amount of water that passes through the meter. The piston or disk moves a magnet that drives the register.
PD meters are generally very accurate at the low-to-moderate flow rates typical of residential and small commercial users and commonly range in size from 5/8" to 2". Because displacement meters require that all water flows through the meter to "push" the measuring element, they generally are not practical in large commercial applications requiring high flow rates or low-pressure loss. PD meters normally have a built-in strainer to protect the measuring element from rocks or other debris that could stop or break the measuring element. PD meters normally have bronze, brass or plastic bodies with internal measuring chambers made of moulded plastics and stainless steel.
A velocity-type meter measures the velocity of flow through a meter of known internal capacity. The speed of the flow can then be converted into a volume of flow to determine the usage. There are several types of meters that measure water flow velocity, including jet meters (single-jet and multi-jet), turbine meters, propeller meters and mag meters. Most velocity-based meters have an adjustment vane for calibrating the meter to the required accuracy.
Multi-jet meters are very accurate in small sizes and are commonly used in 5 ⁄ 8 in (16 mm) to 2 in (51 mm) sizes for residential and small commercial users. Multi-jet meters use multiple ports surrounding an internal chamber to create multiple jets of water against a turbine , whose rotation speed depends on the velocity of water flow. Multi-jets are very accurate at low flow rates, but there are no large size meters since they do not have the straight-through flow path needed for the high flow rates used in large pipe diameters. Multi-jet meters generally have an internal strainer element that can protect the jet ports from getting clogged. Multi-jet meters normally have bronze alloy bodies or outer casings, with internal measuring parts made from modern thermoplastics and stainless steel.
Turbine meters are less accurate than displacement and jet meters at low flow rates, but the measuring element does not occupy or severely restrict the entire path of flow. The flow direction is generally straight through the meter, allowing for higher flow rates and less pressure loss than displacement-type meters. They are the meter of choice for large commercial users, fire protection and as master meters for the water distribution system. Strainers are generally required to be installed in front of the meter to protect the measuring element from gravel or other debris that could enter the water distribution system. Turbine meters are generally available for 1 + 1 ⁄ 2 in (38 mm) to 12 in (300 mm) or higher pipe sizes. Turbine meter bodies are commonly made of bronze, cast iron or ductile iron . Internal turbine elements can be plastic or non-corrosive metal alloys. They are accurate in normal working conditions but are greatly affected by the flow profile and fluid conditions.
A compound meter is used where high flow rates are necessary, but where at times there are also smaller rates of flow that need to be accurately measured. Compound meters have two measuring elements and a check valve to regulate flow between them. At high flow rates, water is normally diverted primarily or completely to the high flow element. The high flow element is typically a turbine meter. When flow rates drop to where the high flow element cannot measure accurately, a check valve closes to divert water to a smaller element that can measure the lower flow rates accurately. The low flow element is typically a multi-jet or PD meter. By adding the values registered by the high and low elements, the utility has a record of the total consumption of water flowing through the meter.
Magnetic flow meters , commonly referred to as "mag meters", are technically a velocity-type water meter, except that they use electromagnetic properties to determine the water flow velocity, rather than the mechanical means used by jet and turbine meters. Mag meters use the physics principle of Faraday's law of induction for measurement and require AC or DC electricity from a power line or battery to operate the electromagnets . Since mag meters have no mechanical measuring element, they normally have the advantage of being able to measure flow in either direction, and use electronics for measuring and totalizing the flow. Mag meters can also be useful for measuring raw (untreated/unfiltered) water and waste-water since there is no mechanical measuring element to get clogged or damaged by debris flowing through the meter. Strainers are not required with mag meters since there is no measuring element in the stream of flow that could be damaged. Since stray electrical energy flowing through the flow tube can cause inaccurate readings, most mag meters are installed with either grounding rings or grounding electrodes to divert stray electricity away from the electrodes used to measure the flow inside the flow tube.
Ultrasonic water meters use one or more ultrasonic transducer to send ultrasonic sound waves through the fluid to determine the velocity of the water. Since the cross-sectional area of the meter body is a fixed and known value, when the velocity of water is detected, the volume of water passing through the meter can be calculated with very high accuracy. Because of water density changes with temperature, most ultrasonic water meters also measure the water temperature as a component of the volume calculation.
There are 2 primary ultrasonic measurement technologies used in water metering:
Ultrasonic meters may either be of flow-through or "clamp-on" design. Flow-through designs are those where the water passes directly through the meter, and are typically found in residential or commercial applications. Clamp-on designs are generally used for larger diameters where the sensors are mounted to the exterior of pipes, etc.
Ultrasonic water meters are highly accurate devices, with residential models capable of measuring flow rates as low as 1 liter per hour (L/h). [ 2 ] They feature wide flow measurement ranges, require minimal maintenance, and have long lifespans due to the absence of internal mechanical components that could wear out over time. [ 3 ] This design ensures stable long-term operation and reduces the need for maintenance.
Although relatively new to some markets, including the American water utility sector, ultrasonic water meters have been well-established in Europe, Asia, and other regions. Their growing popularity is driven by the increasing demand for reliable, low-maintenance, and durable metering solutions suitable for diverse climates and water supply conditions. [ 3 ]
Furthermore, the integration of smart meter technology with ultrasonic systems is accelerating their adoption worldwide, as utility providers seek more efficient and accurate data collection methods.
A Coriolis water meter is a precision instrument used to measure the mass flow rate and density of fluids, including water, by utilizing the Coriolis effect. Unlike traditional mechanical meters with moving parts, Coriolis meters use oscillating tubes through which the fluid flows. As the fluid passes through the tubes, it induces a phase shift in the oscillation, which is detected by sensors and is directly proportional to the mass flow rate. [ 4 ]
Additionally, the meter can determine the fluid's density by analyzing the natural frequency of the oscillating tubes. [ 4 ] This dual measurement capability provides high accuracy and reliability, making Coriolis meters particularly suitable for industrial applications requiring precise flow measurements. In addition, "Coriolis meters have a wide, dynamic range due to the linear nature of the signal created while measuring flow." [ 5 ] However, their high cost often limits their use in residential or municipal water metering. [ 6 ]
The dimensions of water meters, including tube length and diameter, are standardized to ensure compatibility with plumbing systems and compliance with regulatory frameworks. These dimensions are typically defined in terms of nominal pipe size (NPS) in the United States [ 7 ] and nominal diameter (DN) in Europe, with corresponding measurements in inches and millimeters, respectively. Installation lengths are also standardized, differing between the United States and Europe to ensure interchangeability within regional plumbing systems.
The installation length (distance between the connection points) of a water meter varies between regions:
There are several types of registers on water meters. A standard register normally has a dial similar to a clock, with gradations around the perimeter to indicate the measuring unit and the amount of water used, if less than the lowest digit in a display similar to the odometer wheels in a car, their sum is the total volume used. Modern registers are normally driven by a magnetic coupling between a magnet in the measuring chamber attached to the measuring element and another attached to the bottom of the register. Gears in the register convert the motion of the measuring element to the proper usage increment for display on the sweep hand and the odometer-style wheels. Many registers also have a leak detector. This is a small visible disk or hand that is geared closer to the rotation speed of the drive magnet, so that very small flows that would be visually undetectable on the regular sweep hand can be seen.
With Automatic Meter Reading , manufacturers have developed pulse or encoder registers to produce electronic output for radio transmitters, reading storage devices, and data logging devices. Pulse meters send a digital or analog electronic pulse to a recording device. Encoder registers have an electronic means permitting an external device to interrogate the register to obtain either the position of the wheels or a stored electronic reading. Frequent transmissions of consumption data can be used to give smart meter functionality.
There are also some specialized types of registers such as meters with an LCD instead of mechanical wheels, and registers to output data or pulses to a variety of recording and controller devices. For industrial applications, the output is often 4-20 mA analog for recording or controlling different flow rates in addition to totalization.
Different size meters indicate different resolutions of the reading. One rotation of the sweep hand may be equivalent to 10 gallons or to 1,000 gallons (1 to 100 ft 3 , 0.1 to 10 m 3 ). If one rotation of the hand represents 10 gallons, the meter has a 10-gallon sweep. Sometimes the last number(s) of the wheel display are non-rotating or printed on the dial face. The fixed zero number(s) are represented by the position of the rotating sweep hand. For example, if one rotation of the hand is 10 gallons, the sweep hand is on 7, and the wheel display shows 123456 plus a fixed zero, the actual total usage would be 1,234,567 gallons.
In the United States most utilities bill only to the nearest 100 or 1,000 gallons (10 to 100 ft 3 , 1 to 10 m 3 ), and often only read the leftmost 4 or 5 numbers on the display wheels. Using the above example, they would read and bill 1,234, rounding to 1,234,000 gallons based on a 1,000-gallon billing resolution. The most common rounding for a particular size meter is often indicated by differently coloured number wheels, the ones ignored being black, and the ones used for billing being white.
Smart metering technologies for water meters refer to advanced systems that enable real-time monitoring, data collection, and analysis of water usage through digital and connected devices. Unlike traditional mechanical water meters, smart meters are equipped with electronic components that measure water flow and transmit the data wirelessly to utilities and consumers. Key technologies include Automated Meter Reading (AMR), which provides one-way communication to collect usage data, and Advanced Metering Infrastructure (AMI), which supports two-way communication for enhanced features such as remote monitoring, leak detection, and dynamic billing. Smart water meters are integrated with Internet of Things (IoT) platforms, allowing for more efficient water management, reduced waste, and improved customer engagement.
Radio Frequency (RF) technologies form the backbone of smart metering systems by enabling wireless communication between meters and utility networks. Several RF technologies and protocols are widely used in smart water metering:
Application-layer protocols operating above RF communication technologies to standardize data exchange, ensure interoperability, and enhance device functionality. These protocols enable seamless integration of meters into broader utility and Internet of Things (IoT) ecosystems.
DLMS/COSEM (Device Language Message Specification/Companion Specification for Energy Metering) is one of the most widely adopted protocols in smart metering. It provides a flexible and standardized framework for data exchange between metering devices and utility systems. The protocol supports various communication technologies, including RF, wired, and cellular networks, and facilitates secure data transfer, structured data management, and remote monitoring. [ 16 ]
LwM2M (Lightweight Machine to Machine) is a protocol specifically designed for IoT devices, offering efficient resource management and secure communication over constrained networks. Its lightweight design makes it ideal for smart water meters and other low-power devices. LwM2M supports remote configuration, firmware updates, and real-time monitoring, enabling enhanced functionality and scalability in metering systems. [ 17 ]
Other application-layer protocols, such as MQTT (Message Queuing Telemetry Transport) and CoAP (Constrained Application Protocol), are also utilized in smart metering systems, particularly in IoT-centric deployments. These protocols focus on low-bandwidth, high-efficiency communication, ensuring reliable data exchange in diverse environments. [ 18 ] [ 19 ]
A smart water metering system integrates advanced water meters, communication networks, and centralized platforms like the Head-End System (HES) and Meter Data Management System ( MDMS ). Smart meters collect data on water usage, pressure, and anomalies, transmitting it through wireless networks. The HES aggregates and validates this data, forwarding it to the MDMS, which performs advanced analytics, trend reporting, and billing integration.
A WMBUS Gateway (Wireless M-Bus Gateway) is a communication device that enables remote reading of water meters by bridging the gap between the water meters equipped with Wireless M-Bus communication modules and centralized data collection systems. The gateway typically operates on standard frequencies such as 868 MHz (Europe) or other ISM bands. [ 20 ]
WMBUS gateways can be deployed as fixed gateways, installed at permanent locations to continuously collect data from meters within range, or as part of mobile solutions, such as drive-by or walk-by systems, where data is collected via handheld devices or vehicles equipped with receivers as they pass by the meters.
In some cases, electricity meters with integrated communication modules are also utilized as fixed gateways to collect data from nearby water and gas meters, leveraging their existing infrastructure to minimize deployment costs. [ 21 ]
The collected data is then transmitted to a central server via technologies like GSM, GPRS, LTE, or Ethernet for analysis and management.
The adoption of these RF technologies and protocols enables seamless integration of smart water meters into utility systems, offering several advantages:
Water metering is common for residential and commercial drinking water supply in many countries, as well as for industrial self-supply with water. However, it is less common in irrigated agriculture , which is the major water user worldwide. Water metering is also uncommon for piped drinking water supply in rural areas and small towns, although there are examples of successful metering in rural areas in developing countries, such as in El Salvador. [ 22 ]
Metering of water supplied by utilities to residential, commercial and industrial users is common in most developed countries, except for the United Kingdom where only about 52% of users are metered. [ 23 ] In some developing countries metering is very common, such as in Chile where it stands at 96%, while in others it still remains low, such as in Argentina .
The percentage of residential water metering in selected cities in developing countries is as follows: [ 24 ]
Nearly two-thirds of OECD countries meter more than 90% of single-family houses. A few are also expanding their metering of apartments (e.g., France and Germany). [ 25 ]
The benefits of metering are that:
The costs of metering include:
While the cost of purchasing residential meters is low, the total life cycle costs of metering are high. For example, retrofitting flats in large buildings with meters for every flat can involve major and thus costly plumbing work. [ 26 ]
Problems associated with metering arise particularly in the case of intermittent supply , which is common in many developing countries. Sudden changes in pressure can damage meters to the extent that many meters in cities in developing countries are not functional. Also, some types of meters become less accurate as they age, and under-registering consumption leads to lower revenues if defective meters are not regularly replaced. Many types of meters also register air flows, which can lead to over-registration of consumption, [ 27 ] especially in systems with intermittent supply, when water supply is re-established and the incoming water pushes air through the meters.
Displacement Water meters do not distinguish between air and water, both are counted as fluid. There are two regulations where water companies and meter manufacturers do not comply and charge air for water. A measuring system shall be equipped with an effective air/vapor eliminator or other automatic means to prevent the passage of air/vapor through the meter. ref.[Handbook 44 – 2019 3.30. S.2.1.] [ specify ] Measuring systems shall incorporate a gas elimination device for the proper elimination of any air or undissolved gases which may be contained in the liquid before it enters the meter. [ 28 ] [ 29 ] [ failed verification ]
Water meters are subject to measurement standards and certifications to ensure their accuracy, reliability, and compliance with regulatory requirements. The most widely recognized standards include the ISO 4064 [ 30 ] series and the OIML R49 [ 31 ] standards, which define the performance, accuracy classes, and testing procedures for water meters.
In the European Union, compliance with the Measuring Instruments Directive (MID) is mandatory for water meters sold within member states, ensuring conformity with harmonized European standards.
In the United States, water meters typically adhere to the AWWA (American Water Works Association) C700 series standards, which specify design, materials, and performance criteria.
In Australia and New Zealand, water meters must comply with the AS 3565 standard.
Certification processes for water meters often include testing for
Water meters used in potable water systems are required to meet stringent standards to ensure they do not contaminate the water supply or alter its quality. These standards address materials, coatings, and designs that come into contact with drinking water.
In the United States, compliance with NSF/ANSI 61 is mandatory, setting limits on leachable contaminants from water system components.
The European Union mandates conformity with the Regulation (EU) 305/2011 (Construction Products Regulation), alongside national certifications like
In Australia and New Zealand, [ 33 ] the AS/NZS 4020 standard governs the suitability of products for use with potable water, focusing on factors such as taste, color, and toxicity.
In Latin America, countries like Brazil and Mexico often reference international standards such as those from NSF International.
Water meters are frequently installed in environments where they are exposed to rain, flooding, and dust, necessitating robust protection to maintain accurate and reliable operation. An IP68 rating indicates that a device is completely dust-tight and can withstand continuous immersion in water beyond 1 meter depth, as specified by the manufacturer. [ 34 ]
To achieve such protection, manufacturers employ various ingress protection mechanisms:
Additional sensors integrated into water meters are being explored as part of proof-of-concept (PoC) projects to enhance functionality and provide more detailed insights into water usage and system performance.
These innovations aim to address challenges such as leak detection, water quality monitoring, and reverse flow detection.
For instance,
The data collected by the smart meters is analyzed to provide insights into water usage patterns, peak consumption times, and potential issues like leaks or inefficiencies in the system. Utilities can use this data to optimize water distribution and address problems proactively. [ 40 ] [ 41 ]
There is disagreement as to the effect of metering and water pricing on water consumption. The price elasticity of metered water demand varies greatly depending on local conditions. The effect of volumetric water pricing on consumption tends to be higher if the water bill represents a significant portion of household expenditures.
There is evidence from the UK that there is an instant drop in consumption of some 10% when meters are installed, although in most instances consumption is not directly measured prior to meter installation, so the benefits are uncertain. [ 26 ] Whilst metered water users in the UK do use less than unmetered users, in most areas metering is not compulsory for homes built before 1990, [ 42 ] so the metered customers are to some extent a self-selecting group. There is also concern that water metering could be socially regressive, as householders on low incomes are less able to invest in water efficiency measures and may experience water poverty (defined as when a household spends more than 3% of net income on water and sewage services). [ 43 ]
In Hamburg , Germany , domestic water consumption for metered flats (112 liter/capita/day) was 18% lower than for unmetered flats (137 liter/capita/day) in 1992.
Water meter calibration and testing benches employ various methods to evaluate the accuracy and performance of water meters. Each method caters to specific testing requirements, such as flow range, precision, or scalability.
Once the water flow is controlled, various measurement methods are employed to assess the performance and accuracy of water meters. These methods focus on comparing the meter's readings to a reference standard [ 44 ]
A basic and widely used approach where the flow is initiated and stopped over a fixed period or volume. The meter's reading is compared against a precisely measured reference volume, offering reliable results for low to medium flow rates. [ 45 ]
This method involves collecting the fluid over a known period, typically 60s and measuring its mass using high precision weighing scales. [ 45 ]
This method uses a calibrated reference device, such as a piston prover or master meter, to compare the water volume measured by the test meter. It is highly precise and suitable for meters requiring strict compliance with standards.
Continuous flow systems use real-time data acquisition to monitor and compare the meter's readings with those from a calibrated sensor. This modern method enables fast and efficient testing, especially for high-volume operations. [ 46 ]
Meters can be prepaid or postpaid, depending on the payment method. Most mechanical type water meters are of the postpaid type, as are electromagnetic and ultrasonic meters. With prepaid water meters, the user purchases and prepays for a given amount of water from a vending station. The amount of water credited is entered on media such as an IC or RF type card. The main difference is whether the card needs contact with the processing part of the prepaid water meter. In some areas, a prepaid water meter uses a keypad as the interface for inputting the water credit.
Manual Water Meters http://watflux.in/manual-water-meters/
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In computational chemistry , a water model is used to simulate and thermodynamically calculate water clusters , liquid water , and aqueous solutions with explicit solvent, often using molecular dynamics or Monte Carlo methods . The models describe intermolecular forces between water molecules and are determined from quantum mechanics , molecular mechanics , experimental results, and these combinations. To imitate the specific nature of the intermolecular forces, many types of models have been developed. In general, these can be classified by the following three characteristics; (i) the number of interaction points or sites , (ii) whether the model is rigid or flexible, and (iii) whether the model includes polarization effects.
An alternative to the explicit water models is to use an implicit solvation model, also termed a continuum model. Examples of this type of model include the COSMO solvation model , the polarizable continuum model (PCM) and hybrid solvation models. [ 1 ]
The rigid models are considered the simplest water models and rely on non-bonded interactions . In these models, bonding interactions are implicitly treated by holonomic constraints . The electrostatic interaction is modeled using Coulomb's law , and the dispersion and repulsion forces using the Lennard-Jones potential . [ 2 ] [ 3 ] The potential for models such as TIP3P (transferable intermolecular potential with 3 points) and TIP4P is represented by
where k C , the electrostatic constant , has a value of 332.1 Å·kcal/(mol· e ²) in the units commonly used in molecular modeling [ citation needed ] ; [ 4 ] [ 5 ] [ 6 ] q i and q j are the partial charges relative to the charge of the electron; r ij is the distance between two atoms or charged sites; and A and B are the Lennard-Jones parameters . The charged sites may be on the atoms or on dummy sites (such as lone pairs). In most water models, the Lennard-Jones term applies only to the interaction between the oxygen atoms.
The figure below shows the general shape of the 3- to 6-site water models. The exact geometric parameters (the OH distance and the HOH angle) vary depending on the model.
A 2-site model of water based on the familiar three-site SPC model (see below) has been shown to predict the dielectric properties of water using site-renormalized molecular fluid theory. [ 7 ]
Three-site models have three interaction points corresponding to the three atoms of the water molecule. Each site has a point charge, and the site corresponding to the oxygen atom also has the Lennard-Jones parameters. Since 3-site models achieve a high computational efficiency, these are widely used for many applications of molecular dynamics simulations. Most of the models use a rigid geometry matching that of actual water molecules. An exception is the SPC model, which assumes an ideal tetrahedral shape (HOH angle of 109.47°) instead of the observed angle of 104.5°.
The table below lists the parameters for some 3-site models.
The SPC/E model adds an average polarization correction to the potential energy function:
where μ is the electric dipole moment of the effectively polarized water molecule (2.35 D for the SPC/E model), μ 0 is the dipole moment of an isolated water molecule (1.85 D from experiment), and α i is an isotropic polarizability constant, with a value of 1.608 × 10 −40 F ·m 2 . Since the charges in the model are constant, this correction just results in adding 1.25 kcal/mol (5.22 kJ/mol) to the total energy. The SPC/E model results in a better density and diffusion constant than the SPC model.
The TIP3P model implemented in the CHARMM force field is a slightly modified version of the original. The difference lies in the Lennard-Jones parameters: unlike TIP3P, the CHARMM version of the model places Lennard-Jones parameters on the hydrogen atoms too, in addition to the one on oxygen. The charges are not modified. [ 12 ] Three-site model (TIP3P) has better performance in calculating specific heats. [ 13 ]
The flexible simple point-charge water model (or flexible SPC water model) is a re-parametrization of the three-site SPC water model. [ 14 ] [ 15 ] The SPC model is rigid, whilst the flexible SPC model is flexible. In the model of Toukan and Rahman, the O–H stretching is made anharmonic, and thus the dynamical behavior is well described. This is one of the most accurate three-center water models without taking into account the polarization . In molecular dynamics simulations it gives the correct density and dielectric permittivity of water. [ 16 ]
Flexible SPC is implemented in the programs MDynaMix and Abalone .
The four-site models have four interaction points by adding one dummy atom near of the oxygen along the bisector of the HOH angle of the three-site models (labeled M in the figure). The dummy atom only has a negative charge. This model improves the electrostatic distribution around the water molecule. The first model to use this approach was the Bernal–Fowler model published in 1933, [ 21 ] which may also be the earliest water model. However, the BF model doesn't reproduce well the bulk properties of water, such as density and heat of vaporization , and is thus of historical interest only. This is a consequence of the parameterization method; newer models, developed after modern computers became available, were parameterized by running Metropolis Monte Carlo or molecular dynamics simulations and adjusting the parameters until the bulk properties are reproduced well enough.
The TIP4P model, first published in 1983, is widely implemented in computational chemistry software packages and often used for the simulation of biomolecular systems. There have been subsequent reparameterizations of the TIP4P model for specific uses: the TIP4P-Ew model, for use with Ewald summation methods; the TIP4P/Ice, for simulation of solid water ice; TIP4P/2005, a general parameterization for simulating the entire phase diagram of condensed water; and TIP4PQ/2005, a similar model but designed to accurately describe the properties of solid and liquid water when quantum effects are included in the simulation. [ 22 ]
Most of the four-site water models use an OH distance and HOH angle which match those of the free water molecule. One exception is the OPC model, in which no geometry constraints are imposed other than the fundamental C 2v molecular symmetry of the water molecule. Instead, the point charges and their positions are optimized to best describe the electrostatics of the water molecule. OPC reproduces a comprehensive set of bulk properties more accurately than several of the commonly used rigid n -site water models. The OPC model is implemented within the AMBER force field.
Others:
The 5-site models place the negative charge on dummy atoms (labelled L ) representing the lone pairs of the oxygen atom, with a tetrahedral-like geometry. An early model of these types was the BNS model of Ben-Naim and Stillinger, proposed in 1971, [ citation needed ] soon succeeded by the ST2 model of Stillinger and Rahman in 1974. [ 31 ] Mainly due to their higher computational cost, five-site models were not developed much until 2000, when the TIP5P model of Mahoney and Jorgensen was published. [ 32 ] When compared with earlier models, the TIP5P model results in improvements in the geometry for the water dimer , a more "tetrahedral" water structure that better reproduces the experimental radial distribution functions from neutron diffraction , and the temperature of maximal density of water. The TIP5P-E model is a reparameterization of TIP5P for use with Ewald sums .
Note, however, that the BNS and ST2 models do not use Coulomb's law directly for the electrostatic terms, but a modified version that is scaled down at short distances by multiplying it by the switching function S ( r ):
Thus, the R L and R U parameters only apply to BNS and ST2.
Originally designed to study water/ice systems, a 6-site model that combines all the sites of the 4- and 5-site models was developed by Nada and van der Eerden. [ 34 ] Since it had a very high melting temperature [ 35 ] when employed under periodic electrostatic conditions (Ewald summation), a modified version was published later [ 36 ] optimized by using the Ewald method for estimating the Coulomb interaction.
The computational cost of a water simulation increases with the number of interaction sites in the water model. The CPU time is approximately proportional to the number of interatomic distances that need to be computed. For the 3-site model, 9 distances are required for each pair of water molecules (every atom of one molecule against every atom of the other molecule, or 3 × 3). For the 4-site model, 10 distances are required (every charged site with every charged site, plus the O–O interaction, or 3 × 3 + 1). For the 5-site model, 17 distances are required (4 × 4 + 1). Finally, for the 6-site model, 26 distances are required (5 × 5 + 1).
When using rigid water models in molecular dynamics, there is an additional cost associated with keeping the structure constrained, using constraint algorithms (although with bond lengths constrained it is often possible to increase the time step).
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In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals . Water is often incorporated in the formation of crystals from aqueous solutions . [ 1 ] In some contexts, water of crystallization is the total mass of water in a substance at a given temperature and is mostly present in a definite ( stoichiometric ) ratio. Classically, "water of crystallization" refers to water that is found in the crystalline framework of a metal complex or a salt , which is not directly bonded to the metal cation .
Upon crystallization from water, or water-containing solvents , many compounds incorporate water molecules in their crystalline frameworks. Water of crystallization can generally be removed by heating a sample but the crystalline properties are often lost.
Compared to inorganic salts , proteins crystallize with large amounts of water in the crystal lattice. A water content of 50% is not uncommon for proteins.
Knowledge of hydration is essential for calculating the masses for many compounds. The reactivity of many salt-like solids is sensitive to the presence of water.
The hydration and dehydration of salts is central to the use of phase-change materials for energy storage. [ 2 ]
A salt with associated water of crystallization is known as a hydrate . The structure of hydrates can be quite elaborate, because of the existence of hydrogen bonds that define polymeric structures. [ 3 ] [ 4 ] Historically, the structures of many hydrates were unknown, and the dot in the formula of a hydrate was employed to specify the composition without indicating how the water is bound. Per IUPAC's recommendations, the middle dot is not surrounded by spaces when indicating a chemical adduct . [ 5 ] Examples:
For many salts, the exact bonding of the water is unimportant because the water molecules are made labile upon dissolution. For example, an aqueous solution prepared from CuSO 4 ·5H 2 O and anhydrous CuSO 4 behave identically. Therefore, knowledge of the degree of hydration is important only for determining the equivalent weight : one mole of CuSO 4 ·5H 2 O weighs more than one mole of CuSO 4 . In some cases, the degree of hydration can be critical to the resulting chemical properties. For example, anhydrous RhCl 3 is not soluble in water and is relatively useless in organometallic chemistry whereas RhCl 3 ·3H 2 O is versatile. Similarly, hydrated AlCl 3 is a poor Lewis acid and thus inactive as a catalyst for Friedel-Crafts reactions . Samples of AlCl 3 must therefore be protected from atmospheric moisture to preclude the formation of hydrates.
Crystals of hydrated copper(II) sulfate consist of [Cu(H 2 O) 4 ] 2+ centers linked to SO 2− 4 ions. Copper is surrounded by six oxygen atoms, provided by two different sulfate groups and four molecules of water. A fifth water resides elsewhere in the framework but does not bind directly to copper. [ 6 ] The cobalt chloride mentioned above occurs as [Co(H 2 O) 6 ] 2+ and Cl − . In tin chloride, each Sn(II) center is pyramidal (mean O/Cl−Sn−O/Cl angle is 83°) being bound to two chloride ions and one water. The second water in the formula unit is hydrogen-bonded to the chloride and to the coordinated water molecule. Water of crystallization is stabilized by electrostatic attractions, consequently hydrates are common for salts that contain +2 and +3 cations as well as −2 anions. In some cases, the majority of the weight of a compound arises from water. Glauber's salt , Na 2 SO 4 (H 2 O) 10 , is a white crystalline solid with greater than 50% water by weight.
Consider the case of nickel(II) chloride hexahydrate. This species has the formula NiCl 2 (H 2 O) 6 . Crystallographic analysis reveals that the solid consists of [ trans - NiCl 2 (H 2 O) 4 ] subunits that are hydrogen bonded to each other as well as two additional molecules of H 2 O . Thus one third of the water molecules in the crystal are not directly bonded to Ni 2+ , and these might be termed "water of crystallization".
The water content of most compounds can be determined with a knowledge of its formula. An unknown sample can be determined through thermogravimetric analysis (TGA) where the sample is heated strongly, and the accurate weight of a sample is plotted against the temperature. The amount of water driven off is then divided by the molar mass of water to obtain the number of molecules of water bound to the salt.
Water is particularly common solvent to be found in crystals because it is small and polar. But all solvents can be found in some host crystals. Water is noteworthy because it is reactive, whereas other solvents such as benzene are considered to be chemically innocuous. Occasionally more than one solvent is found in a crystal, and often the stoichiometry is variable, reflected in the crystallographic concept of "partial occupancy". It is common and conventional for a chemist to "dry" a sample with a combination of vacuum and heat "to constant weight".
For other solvents of crystallization, analysis is conveniently accomplished by dissolving the sample in a deuterated solvent and analyzing the sample for solvent signals by NMR spectroscopy . Single crystal X-ray crystallography is often able to detect the presence of these solvents of crystallization as well. Other methods may be currently available.
In the table below are indicated the number of molecules of water per metal in various salts. [ 7 ] [ 8 ]
Examples are rare for second and third row metals. No entries exist for Mo, W, Tc, Ru, Os, Rh, Ir, Pd, Hg, Au. AuCl 3 (H 2 O) has been invoked but its crystal structure has not been reported.
Transition metal sulfates form a variety of hydrates, each of which crystallizes in only one form. The sulfate group often binds to the metal, especially for those salts with fewer than six aquo ligands . The heptahydrates, which are often the most common salts, crystallize as monoclinic and the less common orthorhombic forms. In the heptahydrates, one water is in the lattice and the other six are coordinated to the ferrous center. [ 28 ] Many of the metal sulfates occur in nature, being the result of weathering of mineral sulfides. [ 29 ] [ 30 ] Many monohydrates are known. [ 31 ]
Transition metal nitrates form a variety of hydrates. The nitrate anion often binds to the metal, especially for those salts with fewer than six aquo ligands . Nitrates are uncommon in nature, so few minerals are represented here. Hydrated ferrous nitrate has not been characterized crystallographically.
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The presence of water on the terrestrial planets of the Solar System ( Mercury , Venus , Earth , Mars , and the closely related Earth's Moon ) varies with each planetary body, with the exact origins remaining unclear. Additionally, the terrestrial dwarf planet Ceres is known to have water ice on its surface.
Due to its proximity to the Sun and lack of visible water on its surface, the planet Mercury had been thought of as a non- volatile planet. Data retrieved from the Mariner 10 mission found evidence of hydrogen (H), helium (He), and oxygen (O) in Mercury's exosphere. [ 1 ] Volatiles have also been found near the polar regions. [ 2 ] MESSENGER , however, sent back data from multiple on-board instruments that led scientists to the conclusion that Mercury was volatile rich. [ 3 ] [ 4 ] [ 5 ] Mercury is rich in potassium (K) which has been suggested as a proxy for volatile depletion on the planetary body. This leads to assumption that Mercury could have accreted water on its surface, relative to that of Earth if its proximity had not been so near that of the Sun. [ 6 ]
The current Venusian atmosphere has only ~200 mg/kg H 2 O(g) in its atmosphere and the pressure and temperature regime makes water unstable on its surface. Nevertheless, assuming that early Venus's H 2 O had a ratio between deuterium (heavy hydrogen, 2H) and hydrogen (1H) similar to Earth's Vienna Standard Mean Ocean Water ( VSMOW ) of 1.6×10 −4 , [ 7 ] the current D/H ratio in the Venusian atmosphere of 1.9×10 −2 , at nearly ×120 of Earth's, may indicate that Venus had a much larger H 2 O inventory. [ 8 ] While the large disparity between terrestrial and Venusian D/H ratios makes any estimation of Venus's geologically ancient water budget difficult, [ 9 ] its mass may have been at least 0.3% of Earth's hydrosphere. [ 8 ] Estimates based on Venus's levels of deuterium suggest that the planet has lost anywhere from 4 metres (13 ft) of surface water up to "an Earth's ocean's worth". [ 10 ]
Earth's hydrosphere contains ~1.46×10 21 kg (3.22×10 21 lb) of H 2 O and sedimentary rocks contain ~0.21×10 21 kg (4.6×10 20 lb), for a total crustal inventory of ~1.67×10 21 kg (3.68×10 21 lb) of H 2 O. The mantle inventory is poorly constrained in the range of 0.5×10 21 –4×10 21 kg (1.1×10 21 –8.8×10 21 lb). Therefore, the bulk inventory of H 2 O on Earth can be conservatively estimated as 0.04% of Earth's mass (~2.3×10 21 kg (5.1×10 21 lb)).
Recent observation made by a number of spacecraft confirmed significant amounts of lunar water . The secondary ion mass spectrometer (SIMS) measured H 2 O as well as other possible volatiles in lunar volcanic glass bubbles. In these volcanic glasses, 4-46 ppm by weight (wt) of H 2 O was found and then modeled to have been 260-745 ppm wt prior to the lunar volcanic eruptions. [ 11 ] SIMS also found lunar water in the rock samples the Apollo astronauts returned to Earth. These rock samples were tested in three different ways and all came to the same conclusion that the Moon contains water. [ 12 ] [ 13 ] [ 14 ] [ 15 ]
There are three main data sets for water abundance on the lunar surface: highland samples, KREEP samples, and pyroclastic glass samples. Highlands samples were estimated for the lunar magma ocean at 1320-5000 ppm wt of H 2 O in the beginning. [ 16 ] The urKREEP sample estimates a 130-240 ppm wt of H 2 O, which is similar to the findings in the current Highland samples (before modeling). [ 17 ] Pyroclastic glass sample beads were used to estimate the water content in the mantle source and the bulk silicate Moon. The mantle source was estimated at 110 ppm wt of H 2 O and the bulk silicate Moon contained 100-300 ppm wt of H 2 O. [ 18 ] [ 17 ]
A significant amount of surface hydrogen has been observed globally by the Mars Odyssey GRS. [ 19 ] Stoichiometrically estimated water mass fractions indicate that—when free of carbon dioxide —the near surface at the poles consists almost entirely of water covered by a thin veneer of fine material. [ 19 ] This is reinforced by MARSIS observations, with an estimated 1.6 × 10 6 km 3 (3.8 × 10 5 cu mi) of water at the southern polar region with Water Equivalent to a Global layer (WEG) 11 metres (36 ft) deep. [ 20 ] Additional observations at both poles suggest the total WEG to be 30 m (98 ft), while the Mars Odyssey NS observations places the lower bound at ~14 cm (5.5 in) depth. [ 21 ] Geomorphic evidence favors significantly larger quantities of surface water over geologic history, with WEG as deep as 500 m (1,600 ft). [ 21 ] The current atmospheric reservoir of water, though important as a conduit, is insignificant in volume with the WEG no more than 10 μm (0.00039 in). [ 21 ] Since the typical surface pressure of the current atmosphere (~6 hPa (0.087 psi) [ 22 ] ) is less than the triple point of H 2 O, liquid water is unstable on the surface unless present in sufficiently large volumes. Furthermore, the average global temperature is ~220 K (−53 °C; −64 °F), even below the eutectic freezing point of most brines. [ 22 ] For comparison, the highest diurnal surface temperatures at the two MER sites have been ~290 K (17 °C; 62 °F). [ 23 ]
The D/H isotopic ratio is a primary constraint on the source of H 2 O of terrestrial planets. Comparison of the planetary D/H ratios with those of carbonaceous chondrites and comets enables a tentative determination of the source of H 2 O. The best constraints for accreted H 2 O are determined from non-atmospheric H 2 O, as the D/H ratio of the atmospheric component may be subject to rapid alteration by the preferential loss of H [ 22 ] unless it is in isotopic equilibrium with surface H 2 O. Earth's VSMOW D/H ratio of 1.6×10 −4 [ 7 ] and modeling of impacts suggest that the cometary contribution to crustal water was less than 10%. However, much of the water could be derived from Mercury-sized planetary embryos that formed in the asteroid belt beyond 2.5 AU. [ 24 ] Mars's original D/H ratio as estimated by deconvolving the atmospheric and magmatic D/H components in Martian meteorites (e.g., QUE 94201), is ×(1.9+/-0.25) the VSMOW value. [ 24 ] The higher D/H and impact modeling (significantly different from Earth due to Mars's smaller mass) favor a model where Mars accreted a total of 6% to 27% the mass of the current Earth hydrosphere, corresponding respectively to an original D/H between ×1.6 and ×1.2 the SMOW value. [ 24 ] The former enhancement is consistent with roughly equal asteroidal and cometary contributions, while the latter would indicate mostly asteroidal contributions. [ 24 ] The corresponding WEG would be 0.6–2.7 km (0.37–1.68 mi), consistent with a 50% outgassing efficiency to yield ~500 m (1,600 ft) WEG of surface water. [ 24 ] Comparing the current atmospheric D/H ratio of ×5.5 SMOW ratio with the primordial ×1.6 SMOW ratio suggests that ~50 m (160 ft) of has been lost to space via solar wind stripping. [ 24 ]
The cometary and asteroidal delivery of water to accreting Earth and Mars has significant caveats, even though it is favored by D/H isotopic ratios. [ 9 ] Key issues include: [ 9 ]
An alternative to the cometary and asteroidal delivery of H 2 O would be the accretion via physisorption during the formation of the terrestrial planets in the solar nebula . This would be consistent with the thermodynamic estimate of around two Earth masses of water vapor within 3AU of the solar accretionary disk, which would exceed by a factor of 40 the mass of water needed to accrete the equivalent of 50 Earth hydrospheres (the most extreme estimate of Earth's bulk H 2 O content) per terrestrial planet. [ 9 ] Even though much of the nebular H 2 O(g) may be lost due to the high temperature environment of the accretionary disk, it is possible for physisorption of H 2 O on accreting grains to retain nearly three Earth hydrospheres of H 2 O at 500 K (227 °C; 440 °F) temperatures. [ 9 ] This adsorption model would effectively avoid the 187 Os/ 188 Os isotopic ratio disparity issue of distally-sourced H 2 O. However, the current best estimate of the nebular D/H ratio spectroscopically estimated with Jovian and Saturnian atmospheric CH 4 is only 2.1×10 −5 , a factor of 8 lower than Earth's VSMOW ratio. [ 9 ] It is unclear how such a difference could exist, if physisorption were indeed the dominant form of H 2 O accretion for Earth in particular and the terrestrial planets in general.
Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow ( → ) may be read as "within" or "part of".
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https://en.wikipedia.org/wiki/Water_on_terrestrial_planets_of_the_Solar_System
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Water oxidation catalysis (WOC) is the acceleration (catalysis) of the conversion of water into oxygen and protons:
Many catalysts are effective, both homogeneous catalysts and heterogeneous catalysts . The oxygen evolving complex in photosynthesis is the premier example. There is no interest in generating oxygen by water oxidation since oxygen is readily obtained from air. Instead, interest in water oxidation is motivated by its relevance to water splitting , which would provide "solar hydrogen ," i.e. water oxidation would generate the electrons and protons for the production of hydrogen. [ 2 ] An ideal WOC would operate rapidly at low overpotential, exhibit high stability and be of low cost, derived from nontoxic components.
Water is more difficult to oxidize than its conjugate base hydroxide . Hydroxide is stabilized by coordination to metal cations. Some metal hydroxides, those featuring redox-active metal centers, can be oxidized to give metal oxo complexes . Attack of water on metal oxo centers represents one pathway for the formation of the O-O bond, leading to dioxygen. Alternatively, the crucial O-O bond forming step can arise by coupling suitably positioned pairs of metal hydroxo centers. The molecular mechanism of the OEC has not been elucidated.
The conversion of even metal hydroxo complexes to O 2 requires very strong oxidants. In photosynthesis, such oxidants are provided by electron holes on porphyrin radical cations. For device applications, the aspirational oxidant is a photovoltaic material. For screening WOCs, ceric ammonium nitrate is a typical electron acceptor.
A number of ruthenium- aqua complexes catalyze the oxidation of water. Most catalysts feature bipyridine and terpyridine ligands. [ 3 ] [ 4 ] [ 2 ] Catalysts containing pyridine-2-carboxylate exhibit rates (300 s −1 ) comparable to that of photosystem II . [ 5 ] [ 6 ] Work in this area has ushered in many new polypyridyl ligands. [ 7 ] [ 8 ]
Early examples of cobalt-based WOCs suffered from instability. [ 9 ] A homogeneous WOC [Co(py) 5 (H 2 O)](ClO 4 ) 2 [ 10 ] operates by a proton-coupled electron transfer to form a [Co III --OH] 2+ species, which on further oxidation forms a Co IV intermediate. The intermediate formed reacts with water to liberate O 2 . The cobalt- polyoxometalate complex [Co 4 (H 2 O) 2 (α-PW 9 O 34 ) 2 ] 10− is highly efficient WOC. [ 11 ]
Some iron complexes catalyze water oxidation. A water-soluble complex [Fe(OTf) 2 (Me 2 Pytacn)] (Pytacn=pyridine-substituted trimethyltriazacyclononane ; OTf= triflate ) is an efficient WOC. The concentration of the catalyst and the oxidant were found to be strongly affecting the oxidation process. Many related complexes with cis labile sites are active catalysts. Most complexes were found to undergo degradation in a few hours. Higher stability of the molecular catalyst may be achieved using robust clathrochelate ligands that stabilize high oxidation states of iron and prevent rapid degradation of the catalyst. [ 12 ] The number and stereochemistry of reactive coordination sites on Fe have been evaluated but few guidelines have emerged. [ 13 ]
The complexes [Ir(ppy) 2 (OH 2 ) 2 ] + (ppy = 2-phenylpyridine) exhibit high turnover numbers, but low catalytic rates. Replacing ppy with Cp* (C 5 Me 5 ) results in increased catalytic activity but decreased the turnover number. [ 14 ] Water nucleophilic attack on Ir=O species was found to be responsible for the O 2 formation. [ 15 ]
Iridium oxide is a stable bulk WOC catalyst with low overpotential. [ 16 ]
Ni-based oxide film liberates oxygen in quasi-neutral conditions at an overpotential of ~425 mV and shows long lasting stability. [ 17 ] X-ray spectroscopy revealed the presence of di-μ-oxide bridging between Ni III /Ni IV ions but no evidence of mono-μ-oxide bridging was found between the ions. [ 18 ] Similar structures can be found in Co-WOC films and Mn-WOC catalysts. [ 19 ] [ 20 ]
Cobalt oxides (Co 3 O 4 ) have been investigated to work on the same pattern as other cobalt salts. [ 21 ] Cobalt phosphates are also active WOCs at neutral pH. [ 22 ] Stable and highly active WOCs can be prepared by adsorbing Co II on silica nanoparticles. [ 23 ]
The spinel compounds are also very efficient in oxidizing water. When nanodimensional spinels are coated over the carbon materials hydrothermally, followed by a further reduction, can exhibit high efficiency in splitting the water electrochemically. [ 24 ] [ 25 ]
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https://en.wikipedia.org/wiki/Water_oxidation_catalysis
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Water positive is the concept of water conservation by a company, community or individual that actively contributes to the sustainable management and restoration of water resources . This involves implementing practices and technologies that reduce water consumption , improve water quality and enhance water availability . The goal of being water positive is to leave a positive impact on water ecosystems and ensure that more water is conserved and restored than is used or depleted. [ 1 ] [ 2 ] [ 3 ]
Although many corporations have focused on this issue primarily within their own operations, especially in regions with low water thresholds, organizations like the Water Resilience Coalition are committed to achieving a net positive water impact by the year 2050, encompassing their entire value chain . This commitment entails optimizing not only their direct operations but also considering and improving the impact throughout their supply chain. [ 4 ]
The idea of water positivity began in the construction industry in the early 2000s in India . [ 5 ] This was in response to an agenda for optimizing construction practices by reducing their environmental impact through land and material reductions , as well as energy and water conservation, to produce "zero impact buildings." [ 6 ] To conserve water, rain harvesting was considered to minimize dependence on freshwater consumption.
Interest in water positivity expanded to other domains and industries as concerns began to rise over the challenges of global freshwater scarcity. It can be coupled with the previous agenda of net zero emissions , sharing a common goal of restoring the environment through sustainable management of vital resources. Civil and corporate responsibilities aim to control resource consumption and manage waste to achieve a net positive impact. To achieve these goals, compensation incentives are introduced as credits (such as carbon credits or water-positive credits) that can be commercially exchanged between the seller (authorized carbon credit or water-positive holders) and buyers, promoting positive environmental impacts.
Like the compensation of greenhouse gases (GHG), the idea behind water positivity is to balance the water footprint by implementing measures for process efficiency, water purification , aquifer recharge , ecosystem conservation, and other water compensation projects. It focuses on managing this critical resource so that organizations contribute more to global water sustainability.
In 2023, the concept of Water Positive gained greater significance with the creation of the Water Positive Think Tank (WPTT) , [ 7 ] an initiative that brings together experts from various disciplines and regions around the world, committed to sustainable and regenerative water management. This group was formed in response to the growing urgency to implement measures that ensure the availability and quality of water resources in the near future. During the United Nations Water Conference in New York in March 2023 , [ 8 ] the founders of the WPTT recognized the call to action and the shared responsibility to drive effective solutions. In 2024, Daniele Strongone [ 9 ] was appointed as its first president, with Esmeralda Leyva named as vice president.
Water positivity expanded globally in the 2000s, driven partly by the United Nations Millennium Development Goals relating to access to drinking water and the need for manufacturing industries to participate in water sustainability in their production .
Beverage companies like The Coca-Cola Company and PepsiCo established water positivity commitments for water-stressed regions by investing in water efficiency and community projects. They set goals to reduce the use of potable water per liter of product production, becoming models for other industries. In June 2007, Coca-Cola announced a multi-year partnership with World Wildlife Fund (WWF) on water conservation . E. Neville Isdell , Coca-Cola's chairman and CEO, said: "Our goal is to replace every drop of water we use in our beverages and their production. For us, that means reducing the amount of water used...recycling water used for manufacturing processes so it can be safely returned to the environment, and replenishing water in communities and nature through locally relevant projects." [ 10 ]
With the UN Sustainable Development Goals established in 2015 and growing social pressure for companies to adopt environmentally sustainable practices, more companies across various industries publicly committed to the goal of being water positive by 2030 to 2050.
The surge in commitment to this initiative occurred after 2015, when Microsoft , Google , Ecolab , Unilever , Nestlé , AB InBev , Levi's , IKEA , Cargill , BP , Gap Inc. , Colgate-Palmolive , Meta , Diageo , Starbucks , Danone , IBM , Procter & Gamble , Intel and Mars proposed drastic reductions in their operational water consumption, offsetting consumption by implementing strategies such as rainwater harvesting systems, water purification , reforestation projects, and aquifer recharge , among other initiatives, focusing on improving water-stressed basins . [ 11 ]
On August 7, 2023, Canada Ocean Racing, an offshore sailing team competing in the IMOCA Globe Series ), named its new team "Be Water Positive". [ 12 ] The team partnered with Alex Thomson Racing, which managed British solo sailor Alex Thomson’s five Vendée Globe campaigns over the past [ when? ] 20 years. Canada Ocean Racing's goal was to be the first Canadian team to complete the Vendée Globe and build awareness of water positivity. [ 13 ]
The main strategies applied by companies and entities were presented at the United Nations Conference on Water held in New York City in 2023. [ 14 ] It is assumed that by systematically following these guidelines and with long-term commitments, various companies have set goals to be water positive within 10 to 15 years. The strategies are:
The water positive concept, through water purification using unconventional resources, was presented for the first time during the opening ceremony at the IDA 2022 World Congress during the “Charting Resilient Water Solutions” opening ceremony. [ 15 ] The initiative was presented by IDA Vice President at that time, Alejandro Sturniolo.
The objective of water footprint compensation is to achieve a positive impact on global water resources. This is done by collaborating with various stakeholders to implement water purification systems in areas of scarcity, thus increasing the local supply. A more balanced trade in virtual water footprint, which is the water used to produce traded goods and services between regions, is also promoted.
Regulating this virtual water trade can improve the global efficiency of water use. Regions with abundant water resources could compensate part of the water footprint from regions with high water stress, thus helping to alleviate their dependence on virtual water imports. This two-pronged approach of increasing local supply and balancing trade between regions represents a comprehensive management of global water resources that only these decentralized treatments allow in a way similar to the carbon offset market .
The Water Benefit Standard launched in 2014, was the first globally consistent standard that certified the positive socio-economic impacts of water projects. The principles and safeguards from this standard have been embedded into the broader framework of the Gold Standard registry for Water Benefit Certificates. This ensures that any project that may have implications on water quality or access, actively manages any risks. [ 16 ]
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https://en.wikipedia.org/wiki/Water_positive
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Water pouring puzzles (also called water jug problems , decanting problems , [ 1 ] [ 2 ] measuring puzzles , or Die Hard with a Vengeance puzzles ) are a class of puzzle involving a finite collection of water jugs of known integer capacities (in terms of a liquid measure such as liters or gallons ).
Initially each jug contains a known integer volume of liquid, not necessarily equal to its capacity.
Puzzles of this type ask how many steps of pouring water from one jug to another (until either one jug becomes empty or the other becomes full) are needed to reach a goal state, specified in terms of the volume of liquid that must be present in some jug or jugs. [ 3 ]
By Bézout's identity , such puzzles have solution if and only if the desired volume is a multiple of the greatest common divisor of all the integer volume capacities of jugs.
It is a common assumption, stated as part of these puzzles, that the jugs in the puzzle are irregularly shaped and unmarked, so that it is impossible to accurately measure any quantity of water that does not completely fill a jug. Other assumptions of these problems may include that no water can be spilled, and that each step pouring water from a source
jug to a destination jug stops when either the source jug is empty or the destination jug is full, whichever happens first.
The standard puzzle of this kind works with three jugs of capacity 8, 5 and 3 liters. These are initially filled with 8, 0 and 0 liters. In the goal state they should be filled with 4, 4 and 0 liters. The puzzle may be solved in seven steps, passing through the following sequence of states (denoted as a bracketed triple of the three volumes of water in the three jugs):
Cowley (1926) writes that this particular puzzle "dates back to mediaeval times" and notes its occurrence in Bachet 's 17th-century mathematics textbook.
Since the rules only allows stopping/turning on the boundaries of the Cartesian grid (i.e. at the full capacities of each jug), the only reversible actions (reversible in one step) are:
The only irreversible actions that can't be reversed in one step are:
By restricting ourselves to reversible actions only, we can construct the solution to the problem from the desired result. From the point [4,4,0], there are only two reversible actions: transferring 3 liters from the 8 liter jug to the empty 3 liter jug [1,4,3], and transferring 3 liters from the 5 liter jug to the empty 3 liter jug [4,1,3]. Therefore, there are only two solutions to this problem:
The rules are sometimes formulated by adding a tap (a source "jug" with infinite water) and a sink (a drain "jug" that accepts any amount of water without limit). Filling a jug to the rim from the tap or pouring the entire contents of jug into the drain each count as one step while solving the problem. This version of the puzzle was featured in a scene of the 1995 movie Die Hard with a Vengeance . [ 4 ] This variant has an optimal solution that can be obtained using a billiard-shape barycentric plot (or a mathematical billiard). [ 5 ]
The graph shows two ways to obtain 4 liters using 3-liter and 5-liter jugs, and a water source and sink on a Cartesian grid with diagonal lines of slope −1 (such that x + y = c o n s t . {\displaystyle x+y=const.} on these diagonal lines, which represent pouring water from one jug to the other jug). The x and y axes represent the amounts in the 5 and 3 L jugs, respectively. Starting from (0, 0), we traverse the grid along the line segments, turning only on its boundaries, until we reach the black line denoting 4 L in the 5 L jug. Solid lines denote pouring between jugs, dashed lines denote filling a jug and dotted lines denote emptying a jug.
Concatenating either solution, traversal of the 4 L line and the reverse of the other solution returns to (0, 0), yielding a cycle graph . If and only if the jugs' volumes are co-prime , every boundary point is visited, giving an algorithm to measure any integer amount up to the sum of the volumes.
As shown in the previous section, we can construct the solution to the problem from the desired result by using reversible actions only (emptying a full jug into the sink and filling an empty jug from the tap are both reversible). To obtain 4 liters using 3-liter and 5-liter jugs, we want to reach the point (4, 0). From the point (4, 0), there are only two reversible actions: filling the empty 3-liter jug to full from the tap (4,3), or transferring 1 liter of water from the 5-liter jug to the 3-liter jug (1,3). Therefore, there are only two solutions to the problem:
The cycle graph can be represented by the ordered pairs connected by reversible actions:
which contains all the possible states reachable with a 3-liter jug and a 5-liter jug. The state (1, 2), for example, is impossible to reach from an initial state of (0, 0), since (1, 2) has both jugs partially full, and no reversible action is possible from this state.
Another variant [ 6 ] is when one of the jugs has a known volume of water to begin with; In that case, the achievable volumes are either a multiple of the greatest common divisor between the two containers away from the existing known volume, or from zero. For example, if one jug that holds 8 liters is empty and the other jug that hold 12 liters has 9 liters of water in it to begin with, then with a source (tap) and a drain (sink), these two jugs can measure volumes of 9 liters, 5 liters, 1 liter, as well as 12 liters, 8 liters, 4 liters and 0 liters. The simplest solution for 5 liters is (9,0) → (9,8) → (12,5); The simplest solution for 4 liters is (9,0) → (12,0) → (4,8). These solutions can be visualized by red and blue arrows in a Cartesian grid with diagonal lines (of slope -1 such that x + y = c o n s t . {\displaystyle x+y=const.} on these diagonal lines) spaced 4 liters apart, both horizontally and vertically.
Again, if we restrict ourselves to reversible actions only, from the desired point (5,0), there are only two reversible actions: transferring 5 liter of water from the 12-liter jug to the 8-liter jug (0,5), or filling the empty 8 liter jug to full from the tap (5,8). Therefore, there are only two solutions to the problem:
For the 4 liter question, since 4 ≡ 0 mod 4 {\displaystyle 4\equiv 0\!\mod \!4} , one irreversible action is necessary at the start of the solution; It could be simply pouring the whole 9 liters of water from the 12-liter jug to the sink (0,0), or fully fill it to 12 liters from the tap (12,0). Then, we can construct our solutions backwards as before:
If the number of jugs is three, the filling status after each step can be described in a diagram of barycentric coordinates , because the sum of all three integers stays the same throughout all steps. [ 7 ] In consequence the steps can be visualized as billiard moves in the (clipped) coordinate system on a triangular lattice.
The barycentric plot on the right gives two solutions to the 8, 5 and 3 L puzzle. The yellow area denotes combinations achievable with the jugs. Starting at the square, solid red and dashed blue paths show pourable transitions. When a vertex lands on the dotted black triangle, 4 L has been measured. Another pour to the diamond yields 4 L in each 8 and 5 L jugs.
The blue path is one step shorter than the path for the two-jug puzzle with tap and drain, as we can accumulate 4 L in the 8 L jug, absent in the two-jug variant.
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https://en.wikipedia.org/wiki/Water_pouring_puzzle
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A water power engine includes prime movers driven by water and which may be classified under three categories: [ 1 ]
Hydro power is generated when the natural force from the water's current moves a device (fan, propeller, wheel) that is pushed by the force of the water. Ordinary water weighs 8.36 lbs per gallon (1 kg per liter). [ citation needed ] The force makes the turbine mechanism spin, creating electricity. As long as there is flow, it is possible to produce electricity. The advantage of electricity generated in this way is that it is a renewable resource. [ 3 ] A small-scale Micro Hydro Power can be a reliable and long lasting piece of technology. The disadvantage of the system is that technology has yet to be developed more than what it is today. [ citation needed ]
As the prices for gasoline continued to soar a man of many inventions named Stanley Myer worked on a solution that would cut the cost of fueling our cars as well as help the planet. The war on the supply and demand of a necessity for vehicles would become a distant memory if Myer could make his invention work for all vehicles. Myer transformed a dune buggy's fuel system into a system that used water to fuel its engine, which replaced gasoline. The idea was to have cars altered to accommodate the water powered engines. On June 24, 1992 Myer applied to have his work patented. He was a man of many inventions and patents such as his work on Process and apparatus for the production of fuel gas and the enhanced release of thermal energy from such gas, Method for the production of a fuel gas, Controlled process for the production of thermal energy from gases and apparatus useful therefore, Electrical pulse generator, Gas electrical hydrogen generator, Start-up/shut-down for a hydrogen gas burner, Light-guide lens, Solar heating system Multi-stage solar storage system. After a long two years later on March 15, 1994, Myer patented his work. Hydrogen gas fuel and management system for an internal combustion engine using hydrogen gas fuel, patent number 5293857. This invention would use a 2:1 portion of hydrogen to oxygen and a regulated density of the hydrogen component of the mixture such that the burn rate of the mixture approximates that of a fossil fuel and a system for maintaining the foregoing gas fuel mixture and characteristics in an internal combustion engine. [ 4 ] According to Myer, this transformed dune buggy could run a whopping 100 miles per gallon. The dune buggy was able to go so far on water due to a process called electrolysis. The investors and courts felt Myer and his inventions were fraudulent.
Two years later Myer was accused of fraud and had to pay back his investors. The idea was that he had not invented anything new or useful it was a simple use of electrolysis. The investors and courts felt Myer and his inventions were fraudulent. There was another idea that it is impossible to use water in cars due to heat the tolerability of it.
Normal water electrolysis requires the passage of current measured in amps, Meyer's cell achieves the same effect in milliamps. Furthermore ordinary tap water requires the addition of an electrolyte such as sulphuric acid to aid current conduction; Meyer's cell functions at greatest efficiency with pure water. [ 5 ]
Water-powered engines and hydro power can have many advantages in a society that relies mostly on non-renewable resources such as oil and coal. Water covers an estimated 71 percent of the Earth's surface. In conjunction with normal weather patterns such as evaporation and precipitation , water is a natural renewable resource that is in abundance on Earth.
Hydroelectric power has been a popular method of energy dating back to the late 19th century. The main advantage of using hydropower is that it is a clean form of energy, otherwise known as "green" energy. Since the process of using waterpower does not require burning fossil fuels , it is more environmentally friendly. Fewer Greenhouse gasses are emitted into the atmosphere contributing to climate change , lower levels of smog in large cities, and a lesser chance of acid rain taking place.
In the current economy, fossil fuels account for most competitive markets between big businesses. This leads to a constant fluctuation in economic prices being considerably high or low depending on supply and demand. Unlike fossil fuels which are non-renewable, rivers, lakes, and ocean water are an infinite resource. Dams are a product of the water-power engine and provide consistent energy to nearby populated areas. Murray 1 and 2 Hydro Electric Power Stations and the Tumut 3 Hydroelectric Power Station in Australia is responsible for generating between 550 megawatts and 1,800 megawatts of electricity. The water powered turbines used in these dams need little maintenance, are easily upgradable with modern technology, and have a lifespan of 50–100 years.
Clean energy created by hydro power plants attracts positive results in otherwise remote areas. It enhances commerce and gives rise to more industry. The overall education improves in these areas as well as healthcare. Dams that run on hydro powered engines create lakes that attract tourists and boosts the economy in those areas. Such as the Hoover Dam which attracts 7 million tourists every year. The advantages of using hydro power and controlling water flow also has irrigation benefits. In areas that have less rainfall, such as Arizona and Nevada, the ability to control the waterpower engine's water consumption saves water during dry seasons making the region less reliant on natural rainfall.
Although beneficial in the long run, water powered engines require materials that require a high financial price. Hydro powered dams require less maintenance once fully constructed, however the time it takes to earn its revenue back may take almost its whole lifespan.
Some water powered engines and the plants associated with them can emit large amounts of methane and carbon dioxide into the atmosphere. This is mainly due to the surrounding reservoirs that have stagnant water where over long periods of time plants and other biological material decomposes and produces environmentally harmful pollutants into the air.
Currently in Israel, MayMaan Research, LLC, has developed a powerful piston engine that runs on a combination of water and ethanol (or another alcohol) and does not require the use of diesel or regular gasoline. The water powered piston engine eliminates both nitrogen and sulfur oxides that create harmful air quality. They estimate that it is 60 percent more efficient than gasoline and can save on 50 percent of fuel costs. They plan to not only focus on automobiles but overall transportation such as ships, trains, and large trucks. The mission that MayMaan Research and its founders are trying to accomplish is to eliminate the dependency on fossil fuels worldwide and to create a greener environment for all.
Ten examples of relevant inventions:
Many inventions involve water. The problem is finding inventions that can be useful to all people and help curve poverty as well as curve the negative impacts inventions have on our natural world and wild life. [ 6 ]
There have been a number of hoaxes, claiming the invention of water-powered engines. No water powered engine has successfully been invented to the point of getting a patent.
Conspiracy theorists believe that there is a global suppression surrounding the idea of creating a successful water fuel cell or fully water powered engine. This stems from the idea that large oil companies that control most of the revenue related to gas and fossil fuels do not want water fueled technology to overpower current gas and electric reliant vehicles. This would not only create a cheaper, cleaner, and more efficient engine but also would eventually make oil companies obsolete.
The uncertainty behind events such as these are what fuels conspiracy theorists to continue to support the claim of suppression of clean energy technology by unknown entities.
The idea of a water powered car has been around since Stanley Meyer's "water fuel cell" made it popular in the late 20th century. However, he was met with pushback from an Ohio court claiming that such an automobile could not possibly work. Meyer abruptly died in 1998 while eating at a restaurant. According to his brother, Meyer ran out of the restaurant screaming "They’ve poisoned me" before succumbing to his death. Due to this account, some believe that Meyer was poisoned by those trying to dismantle the idea of clean energy, especially in a time of a booming crude oil industry. This was never proven to be true as an autopsy revealed that Meyer died from a cerebral aneurysm and not poison.
One such event that raised eyebrows was the company Genepax and their "water powered car". Primarily based in Japan, it was unveiled in 2008 that Genepax had a working concept car that apparently ran solely on air and water. It did this by using a special water energy system and a membrane electrode assembly (MES). These two technologies combined was able to break down hydrogen and oxygen through the processes of a chemical reaction. It was a design that made the future of water powered technology attainable and not too far off from becoming the future of clean energy.
That is until the mid 2000s that Genepax suddenly shut its doors for good without notice. For a company that made many appearances to the public showcasing the future of automobiles, many find it strange that it ended so suddenly, which correlates with the sudden death of the inventor himself Stanley Meyer.
[ 1 ]
[ 2 ] [ 3 ]
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https://en.wikipedia.org/wiki/Water_power_engine
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A Water pyramid or WaterPyramid is a village-scale solar still , designed to distill water using solar energy for remote communities without easy access to clean, fresh water. It provides a means whereby communities can produce potable drinking water from saline , brackish or polluted water sources.
Martijn Nitzsche, an engineer from the Netherlands , founded Aqua-Aero Water Systems to develop water treatment and purification systems. In the early 2000s, the company invented the WaterPyramid technology. [ 1 ] The first WaterPyramid was engineered and installed in collaboration with MWH Global , an international environmental engineering firm, in the country of Gambia in 2005. The WaterPyramid desalination systems were awarded the World Bank Development Marketplace award in 2006. [ 2 ]
The pyramid stands about 26 feet (7.9 meters) tall, 100 feet (30 meters) in diameter, and has a conical shape. It is constructed of plastic sheeting, which is inflated using a fan powered by solar energy generated by the pyramid. Within the pyramid, temperatures reach up to 167 °F (75 °C), which evaporates water pumped into thin layer of water inside the cone. Distilled water runs down the sides of the pyramid wall and is collected by gutters that feed into a collection tank. When sunshine is replaced by rain, the falling water is also collected around the edge of the base of the cone and stored for use in dry weather. Each pyramid can desalinate approximately 265 U.S. gallons (1,000 liters) of water each day. [ 3 ] To increase water production, a village simply adds additional pyramids. [ citation needed ]
Operation of each pyramid is the responsibility of the local community, generating employment opportunities for the village. Since the water produced by the Pyramid is distilled water , there are also business uses for excess water production, such as the filling of batteries, which provide additional income to the village. [ 4 ]
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https://en.wikipedia.org/wiki/Water_pyramid
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Water quality refers to the chemical , physical , and biological characteristics of water based on the standards of its usage. [ 1 ] [ 2 ] It is most frequently used by reference to a set of standards against which compliance, generally achieved through treatment of the water, can be assessed. The most common standards used to monitor and assess water quality convey the health of ecosystems , safety of human contact, extent of water pollution and condition of drinking water . Water quality has a significant impact on water supply and often determines supply options. [ 3 ]
Over time, there has been increasing recognition of the importance of drinking water quality and its impact on public health . This has led to increasing protection and management of water quality. [ 4 ]
The understanding of the links between water quality and health continues to grow and highlight new potential health crises: from the chronic impacts of infectious diseases on child development through stunting to new evidence on the harms from known contaminants, such as manganese with growing evidence of neurotoxicity in children. [ 4 ] In addition, there are many emerging water quality issues—such as microplastics , perfluorinated compounds , and antimicrobial resistance . [ 4 ]
The parameters for water quality are determined by the intended use. Work in the area of water quality tends to be focused on water that is treated for potability, industrial/domestic use, or restoration (of an environment/ecosystem, generally for health of human/aquatic life). [ 5 ]
Contaminants that may be in untreated water include microorganisms such as viruses , protozoa and bacteria ; inorganic contaminants such as salts and metals ; organic chemical contaminants from industrial processes and petroleum use; pesticides and herbicides ; and radioactive contaminants. Water quality depends on the local geology and ecosystem , as well as human uses such as sewage dispersion, industrial pollution, use of water bodies as a heat sink , and overuse (which may lower the level of the water). [ citation needed ]
The United States Environmental Protection Agency [ 6 ] (EPA) limits the amounts of certain contaminants in tap water provided by US public water systems . The Safe Drinking Water Act authorizes EPA to issue two types of standards:
The U.S. Food and Drug Administration (FDA) regulations establish limits for contaminants in bottled water . [ 10 ] Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of these contaminants does not necessarily indicate that the water poses a health risk.
In urbanized areas around the world, water purification technology is used in municipal water systems to remove contaminants from the source water (surface water or groundwater ) before it is distributed to homes, businesses, schools and other recipients. Water drawn directly from a stream, lake, or aquifer and that has no treatment will be of uncertain quality in terms of potability. [ 3 ]
The burden of polluted drinking water disproportionally effects under-represented and vulnerable populations. [ 11 ] Communities that lack these clean drinking-water services are at risk of contracting water-borne and pollution-related illnesses like Cholera, diarrhea , dysentery, hepatitis A, typhoid, and polio. [ 12 ] These communities are often in low-income areas, where human wastewater is discharged into a nearby drainage channel or surface water drain without sufficient treatment, or is used in agricultural irrigation.
Dissolved ions may affect the suitability of water for a range of industrial and domestic purposes. The most familiar of these is probably the presence of calcium (Ca 2+ ) and magnesium (Mg 2+ ) that interfere with the cleaning action of soap , and can form hard sulfate and soft carbonate deposits in water heaters or boilers . [ 13 ] Hard water may be softened to remove these ions. The softening process often substitutes sodium cations. [ 14 ] For certain populations, hard water may be preferable to soft water because health problems have been associated with calcium deficiencies and with excess sodium. [ 15 ] The necessity for additional calcium and magnesium in water depends on the population in question because people generally satisfy their recommended amounts through food. [ 3 ] : 99, 115, 377
Environmental water quality , also called ambient water quality, relates to water bodies such as lakes , rivers , and oceans . [ 16 ] Water quality standards for surface waters vary significantly due to different environmental conditions, ecosystems, and intended human uses. Toxic substances and high populations of certain microorganisms can present a health hazard [ 17 ] for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses. These conditions may also affect wildlife, which use the water for drinking or as a habitat. According to the EPA, water quality laws generally specify protection of fisheries and recreational use and require, as a minimum, retention of current quality standards. [ 18 ] In some locations, desired water quality conditions include high dissolved oxygen concentrations, low chlorophyll-a concentrations, and high water clarity . [ 19 ]
There is some desire among the public to return water bodies to pristine, or pre-industrial conditions. [ 20 ] Most current environmental laws focus on the designation of particular uses of a water body. In some countries these designations allow for some water contamination as long as the particular type of contamination is not harmful to the designated uses. Given the landscape changes (e.g., land development , urbanization , clearcutting in forested areas) in the watersheds of many freshwater bodies, returning to pristine conditions would be a significant challenge. In these cases, environmental scientists focus on achieving goals for maintaining healthy ecosystems and may concentrate on the protection of populations of endangered species and protecting human health.
The complexity of water quality as a subject is reflected in the many types of measurements of water quality indicators. Some measurements of water quality are most accurately made on-site, because water exists in equilibrium with its surroundings . Measurements commonly made on-site and in direct contact with the water source in question include temperature , pH , dissolved oxygen , conductivity , oxygen reduction potential (ORP) , turbidity , and Secchi disk depth.
Sampling of water for physical or chemical testing can be done by several methods, depending on the accuracy needed and the characteristics of the contaminant. Sampling methods include for example simple random sampling, stratified sampling , systematic and grid sampling, adaptive cluster sampling , grab samples, semi-continuous monitoring and continuous, passive sampling , remote surveillance, remote sensing , and biomonitoring . The use of passive samplers greatly reduces the cost and the need of infrastructure on the sampling location.
Many contamination events are sharply restricted in time, most commonly in association with rain events. For this reason "grab" samples are often inadequate for fully quantifying contaminant levels. [ 21 ] Scientists gathering this type of data often employ auto-sampler devices that pump increments of water at either time or discharge intervals.
More complex measurements are often made in a laboratory requiring a water sample to be collected, preserved, transported, and analyzed at another location.
The process of water sampling introduces two significant problems:
Sample preservation may partially resolve the second problem. A common procedure is keeping samples cold to slow the rate of chemical reactions and phase change, and analyzing the sample as soon as possible; but this merely minimizes the changes rather than preventing them. [ 23 ] : 43–45 A useful procedure for determining influence of sample containers during delay between sample collection and analysis involves preparation for two artificial samples in advance of the sampling event. One sample container is filled with water known from previous analysis to contain no detectable amount of the chemical of interest. This sample, called a "blank", is opened for exposure to the atmosphere when the sample of interest is collected, then resealed and transported to the laboratory with the sample for analysis to determine if sample collection or holding procedures introduced any measurable amount of the chemical of interest. The second artificial sample is collected with the sample of interest, but then "spiked" with a measured additional amount of the chemical of interest at the time of collection. The blank ( negative control ) and spiked sample ( positive control ) are carried with the sample of interest and analyzed by the same methods at the same times to determine any changes indicating gains or losses during the elapsed time between collection and analysis. [ 25 ]
After events such as earthquakes and tsunamis , there is an immediate response by the aid agencies as relief operations get underway to try and restore basic infrastructure and provide the basic fundamental items that are necessary for survival and subsequent recovery. [ 26 ] The threat of disease increases hugely due to the large numbers of people living close together, often in squalid conditions, and without proper sanitation. [ 27 ]
After a natural disaster , as far as water quality testing is concerned, there are widespread views on the best course of action to take and a variety of methods can be employed. The key basic water quality parameters that need to be addressed in an emergency are bacteriological indicators of fecal contamination, free chlorine residual, pH , turbidity and possibly conductivity / total dissolved solids . There are many decontamination methods. [ 28 ] [ 29 ]
After major natural disasters, a considerable length of time might pass before water quality returns to pre-disaster levels. For example, following the 2004 Indian Ocean tsunami the Colombo-based International Water Management Institute (IWMI) monitored the effects of saltwater and concluded that the wells recovered to pre-tsunami drinking water quality one and a half years after the event. [ 30 ] IWMI developed protocols for cleaning wells contaminated by saltwater; these were subsequently officially endorsed by the World Health Organization as part of its series of Emergency Guidelines. [ 31 ]
The simplest methods of chemical analysis are those measuring chemical elements without respect to their form. Elemental analysis for oxygen , as an example, would indicate a concentration of 890 g/L ( grams per litre ) of water sample because oxygen (O) has 89% mass of the water molecule (H 2 O). The method selected to measure dissolved oxygen should differentiate between diatomic oxygen and oxygen combined with other elements. The comparative simplicity of elemental analysis has produced a large amount of sample data and water quality criteria for elements sometimes identified as heavy metals . Water analysis for heavy metals must consider soil particles suspended in the water sample. These suspended soil particles may contain measurable amounts of metal. Although the particles are not dissolved in the water, they may be consumed by people drinking the water. Adding acid to a water sample to prevent loss of dissolved metals onto the sample container may dissolve more metals from suspended soil particles. Filtration of soil particles from the water sample before acid addition, however, may cause loss of dissolved metals onto the filter. [ 32 ] The complexities of differentiating similar organic molecules are even more challenging.
Making these complex measurements can be expensive. Because direct measurements of water quality can be expensive, ongoing monitoring programs are typically conducted and results released by government agencies . However, there are local volunteer programs and resources available for some general assessment. [ 33 ] Tools available to the general public include on-site test kits, commonly used for home fish tanks , and biological assessment procedures.
Biosensors have the potential for "high sensitivity, selectivity, reliability, simplicity, low-cost and real-time response". [ 34 ] For instance, bionanotechnologists reported the development of ROSALIND 2.0 , that can detect levels of diverse water pollutants. [ 35 ] [ 36 ]
Although water quality is usually sampled and analyzed at laboratories, since the late 20th century there has been increasing public interest in the quality of drinking water provided by municipal systems. Many water utilities have developed systems to collect real-time data about source water quality. In the early 21st century, a variety of sensors and remote monitoring systems have been deployed for measuring water pH, turbidity, dissolved oxygen and other parameters. [ 37 ] Some remote sensing systems have also been developed for monitoring ambient water quality in riverine, estuarine and coastal water bodies. [ 38 ] [ 39 ]
The following is a list of indicators often measured by situational category:
Biological monitoring metrics have been developed in many places, and one widely used family of measurements for freshwater is the presence and abundance of members of the insect orders Ephemeroptera , Plecoptera and Trichoptera (EPT) (of benthic macroinvertebrates whose common names are, respectively, mayfly, stonefly and caddisfly). EPT indexes will naturally vary from region to region, but generally, within a region, the greater the number of taxa from these orders, the better the water quality. Organisations in the United States, such as EPA. offer guidance on developing a monitoring program and identifying members of these and other aquatic insect orders. Many US wastewater dischargers (e.g., factories, power plants, refineries , mines, municipal sewage treatment plants) are required to conduct periodic whole effluent toxicity (WET) tests. [ 40 ] [ 41 ]
Individuals interested in monitoring water quality who cannot afford or manage lab scale analysis can also use biological indicators to get a general reading of water quality. One example is the IOWATER volunteer water monitoring program of Iowa , which includes an EPT indicator key. [ 42 ]
Bivalve molluscs are largely used as bioindicators to monitor the health of aquatic environments in both fresh water and the marine environments. Their population status or structure, physiology, behaviour or the level of contamination with elements or compounds can indicate the state of contamination status of the ecosystem. They are particularly useful since they are sessile so that they are representative of the environment where they are sampled or placed. A typical project is the U.S. Mussel Watch Programme , [ 43 ] but today they are used worldwide.
The Southern African Scoring System (SASS) method is a biological water quality monitoring system based on the presence of benthic macroinvertebrates (EPT). The SASS aquatic biomonitoring tool has been refined over the past 30 years and is now on the fifth version (SASS5) which has been specifically modified in accordance with international standards, namely the ISO/IEC 17025 protocol. [ 44 ] The SASS5 method is used by the South African Department of Water Affairs as a standard method for River Health Assessment, which feeds the national River Health Programme and the national Rivers Database.
Weather and its related shocks can affect water quality in several ways. These depend on the local climate and context. [ 45 ] Shocks that are linked to weather include water shortages, heavy rain and temperature extremes. They can damage water infrastructure through erosion under heavy rainfall and floods, cause loss of water sources in droughts, and make water quality deteriorate. [ 45 ]
Climate change can reduce lower water quality in several ways: [ 46 ] : 582
In the setting of standards, agencies make political and technical/scientific decisions based on how the water will be used. [ 55 ] In the case of natural water bodies , agencies also make some reasonable estimate of pristine conditions. Natural water bodies will vary in response to a region's environmental conditions, whereby water composition is influenced by the surrounding geological features, sediments, and rock types, topography , hydrology , and climate. [ 56 ] Environmental scientists and aqueous geochemists work to interpret the parameters and environmental conditions that impact the water quality of a region, which in turn helps to identify the sources and fates of contaminants . Environmental lawyers and policymakers work to define legislation with the intention that water is maintained at an appropriate quality for its identified use.
Another general perception of water quality is that of a simple property that tells whether water is polluted or not. In fact, water quality is a complex subject, in part because water is a complex medium intrinsically tied to the ecology , geology , and anthropogenic activities of a region. Industrial and commercial activities (e.g. manufacturing , mining , construction , transport ) are a major cause of water pollution as are runoff from agricultural areas, urban runoff and discharge of treated and untreated sewage . [ citation needed ]
The water policy of the European Union is primarily codified in three directives :
Water quality guidelines for South Africa are grouped according to potential user types (e.g. domestic, industrial) in the 1996 Water Quality Guidelines. [ 59 ] Drinking water quality is subject to the South African National Standard (SANS) 241 Drinking Water Specification. [ 60 ]
In England and Wales acceptable levels for drinking water supply are listed in the "Water Supply (Water Quality) Regulations 2000." [ 61 ]
In the United States, Water Quality Standards are defined by state agencies for various water bodies, guided by the desired uses for the water body (e.g., fish habitat, drinking water supply, recreational use). [ 62 ] The Clean Water Act (CWA) requires each governing jurisdiction (states, territories, and covered tribal entities) to submit a set of biennial reports on the quality of water in their area. These reports are known as the 303(d) and 305(b) reports, named for their respective CWA provisions, and are submitted to, and approved by, EPA. [ 63 ] These reports are completed by the governing jurisdiction, typically a state environmental agency . EPA recommends that each state submit a single "Integrated Report" comprising its list of impaired waters and the status of all water bodies in the state. [ 64 ] The National Water Quality Inventory Report to Congress is a general report on water quality, providing overall information about the number of miles of streams and rivers and their aggregate condition. [ 65 ] The CWA requires states to adopt standards for each of the possible designated uses that they assign to their waters. Should evidence suggest or document that a stream, river or lake has failed to meet the water quality criteria for one or more of its designated uses, it is placed on a list of impaired waters. Once a state has placed a water body on this list, it must develop a management plan establishing Total Maximum Daily Loads (TMDLs) for the pollutant(s) impairing the use of the water. These TMDLs establish the reductions needed to fully support the designated uses. [ 66 ]
Drinking water standards, which are applicable to public water systems , are issued by EPA under the Safe Drinking Water Act . [ 8 ]
Archived 24 March 2018 at the Wayback Machine – Professional association
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https://en.wikipedia.org/wiki/Water_quality
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Water quality modeling involves water quality based data using mathematical simulation techniques. Water quality modeling helps people understand the eminence of water quality issues and models provide evidence for policy makers to make decisions in order to properly mitigate water. [ 1 ] Water quality modeling also helps determine correlations to constituent sources and water quality along with identifying information gaps. [ 2 ] Due to the increase in freshwater usage among people, water quality modeling is especially relevant [ 3 ] both in a local level and global level. In order to understand and predict the changes over time in water scarcity , climate change, and the economic factor of water resources, [ 1 ] water quality models would need sufficient data by including water bodies from both local and global levels.
A typical water quality model consists of a collection of formulations representing physical mechanisms that determine position and momentum of pollutants in a water body. [ 4 ] Models are available for individual components of the hydrological system such as surface runoff ; [ 5 ] there also exist basin wide models addressing hydrologic transport and for ocean and estuarine applications. Often finite difference methods are used to analyze these phenomena, and, almost always, large complex computer models are required. [ 6 ]
Water quality models have different information, but generally have the same purpose, which is to provide evidentiary support of water issues. Models can be either deterministic or statistical depending on the scale with the base model, [ 2 ] which is dependent on if the area is on a local, regional, or a global scale. Another aspect to consider for a model is what needs to be understood or predicted about that research area along with setting up any parameters to define the research. Another aspect of building a water quality model is knowing the audience and the exact purpose for presenting data like to enhance water quality management [ 7 ] for water quality law makers for the best possible outcomes.
A SPARROW model is a SPAtially-Referenced Regression on Watershed attributes, which helps integrate water quality data with landscape information. [ 2 ] More specifically the USGS used this model to display long-term changes within watersheds to further explain in-stream water measurement in relation to upstream sources, water quality, and watershed properties. These models predict data for various spatial scales and integrate streamflow data with water quality at numerous locations across the US. [ 2 ] A SPARROW model used by the USGS focused on the nutrients in the Nation's major rivers and estuaries; this model helped create a better understanding of where nutrients come from, where they are transported to while in the water bodies, and where they end up (reservoirs, other estuaries, etc.). [ 2 ]
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https://en.wikipedia.org/wiki/Water_quality_modelling
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Water Remote Sensing is the observation of water bodies such as lakes , oceans , and rivers from a distance in order to describe their color, state of ecosystem health, and productivity. Water remote sensing studies the color of water through the observation of the spectrum of water leaving radiance. From the spectrum of color coming from the water, the concentration of optically active components of the upper layer of the water body can be estimated via specific algorithms . [ 1 ] Water quality monitoring by remote sensing and close-range instruments has obtained considerable attention since the founding of EU Water Framework Directive. [ 1 ]
Water remote sensing instruments (sensors) allow scientists to record the color of a water body, which provides information on the presence and abundance of optically active natural water components (plankton, sediments, detritus, or dissolved substances). The water color spectrum as seen by a satellite sensor is defined as an apparent optical property (AOP) of the water. This means that the color of the water is influenced by the angular distribution of the light field and by the nature and quantity of the substances in the medium, in this case, water. [ 2 ] Thus, the values of remote sensing reflectance, an AOP, will change with changes in the optical properties and concentrations of the optically active substances in the water. Properties and concentrations of substances in the water are known as the inherent optical properties or IOPs. [ 1 ] IOPs are independent from the angular distribution of light (the "light field") but they are dependent on the type and amount of substances that are present in the water. [ 2 ] For instance, the diffuse attenuation coefficient of downwelling irradiance , K d (often used as an index of water clarity or ocean turbidity ) is defined as an AOP (or quasi-AOP), while the absorption coefficient and the scattering coefficient of the water are defined as IOPs. [ 2 ] There are two different approaches to determine the concentration of optically active water components by the study of spectra, distributions of light energy over a range of wavelengths or colors. The first approach consist of empirical algorithms based on statistical relationships. The second approach consists of analytical algorithms based on the inversion of calibrated bio-optical models. [ 1 ] [ 2 ] Accurate calibration of the relationships and/or models used is an important condition for successful inversion on water remote sensing techniques and the determination of concentration of water quality parameters from observed spectral remote sensing data. [ 1 ] Thus, these techniques depend on their ability to record these changes in the spectral signature of light backscattered from water surface and relate these recorded changes to water quality parameters via empirical or analytical approaches. Depending on the water constituents of interest and the sensor used, different parts of the spectrum will be analyzed. [ 3 ]
The gradual development of understanding of the transparency of natural waters and of the reason of their clarity variability and coloration has been sketched from the times of Henry Hudson (1600) to those of Chandrasekhara Raman (1930). [ 4 ] However, the development of water remote sensing techniques (by the use of satellite imaging, aircraft or close range optical devices) didn't start until the early 1970s. These first techniques measured the spectral and thermal differences in the emitted energy from water surfaces. In general, empirical relationships were settled between the spectral properties and the water quality parameters of the water body. [ 3 ] In 1974, Ritchie et al. (1974) [ 5 ] developed an empirical approach to determine suspended sediments. This kind of empirical models are only able to use to determine water quality parameters of water bodies with similar conditions. In 1992 an analytical approach was used by Schiebe et al. (1992). [ 6 ] This approach was based on the optical characteristics of water and water quality parameters to elaborate a physically based model of the relationship between the spectral and physical properties of the surface water studied. This physically based model was successfully applied in order to estimate suspended sediment concentrations. [ 3 ] [ 6 ] [ 7 ] [ 8 ]
By the use of optical close range devices (e.g. spectrometers , radiometers ), airplanes or helicopters (airborne remote sensing) and satellites (space-borne remote sensing), the light energy radiating from water bodies is measured. For instance, algorithms are used to retrieve parameters such as chlorophyll-a (Chl-a) and Suspended Particulate Matter (SPM) concentration, the absorption by colored dissolved organic matter at 440 nm (aCDOM) and secchi depth . [ 1 ] The measurement of these values will give an idea about the water quality of the water body being studied. A very high concentration of green pigments like chlorophyll might indicate the presence of an algal bloom, for example, due to eutrophication processes. Thus, the chlorophyll concentration could be used as a proxy or indicator for the trophic condition of a water body. In the same manner, other optical quality parameters such as suspended particles or Suspended Particulate matter (SPM), Colored Dissolved Organic Matter (CDOM), Transparency (Kd), and chlorophyll-a (Chl-a) can be used to monitor water quality. [ 1 ]
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https://en.wikipedia.org/wiki/Water_remote_sensing
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Water resource policy, sometimes called water resource management or water management , encompasses the policy-making processes and legislation that affect the collection, preparation, use, disposal, and protection of water resources. [ 1 ] The long-term viability of water supply systems poses a significant challenge as a result of water resource depletion, climate change, and population expansion. [ 2 ]
Water is a necessity for all forms of life as well as industries on which humans are reliant, like technology development and agriculture . [ 3 ] [ 4 ] This global need for clean water access necessitates water resource policy to determine the means of supplying and protecting water resources. Water resource policy varies by region and is dependent on water availability or scarcity , the condition of aquatic systems, and regional needs for water. [ 5 ] Since water basins do not align with national borders, water resource policy is also determined by international agreements, also known as hydropolitics . [ 6 ] Water quality protection also falls under the umbrella of water resource policy; laws protecting the chemistry, biology, and ecology of aquatic systems by reducing and eliminating pollution , regulating its usage, and improving the quality are considered water resource policy. [ 1 ] When developing water resource policies, many different stakeholders, environmental variables, and considerations have to be taken to ensure the health of people and ecosystems are maintained or improved. Finally, ocean zoning , coastal , and environmental resource management are also encompassed by water resource management, like in the instance of offshore wind land leasing. [ 7 ]
As water scarcity increases with climate change, the need for robust water resource policies will become more prevalent. An estimated 57% of the world's population will experience water scarcity at least one month out of the year by 2050. [ 8 ] Mitigation and updated water resource policies will require interdisciplinary and international collaboration, including government officials, environmental scientists, sociologists, economists, climate modelers, and activists. [ 9 ] [ 10 ]
When considering its utility as a resource and developing water resource policy, water can be classified into 4 different categories: green, blue, gray, and virtual water. Blue water is surface and groundwater, like water in rivers, lakes, and aquifers. [ 11 ] Green water is rainwater that was precipitated on soil that can be used naturally for plants and agriculture. [ 12 ] [ 11 ] Gray water is water that has been contaminated by human use or proximity. The gray water classification can range from freshwater fertilizer runoff pollution [ 13 ] to water contaminated from dishwashers and showers. [ 14 ] Virtual water is the water consumed to make an agricultural or industrial product. [ 11 ] Calculating virtual water of a commodity is used to determine the water footprint of a country and see how much water they are importing and exporting through their goods. [ 15 ] [ 12 ]
Water basins do not align with national borders and an estimated 60% of worldwide freshwater flows across political boundaries. [ 16 ] Countries navigate managing shared water resources by making agreements in the form of treaties . Treaties between nations may enumerate policies, rights and responsibilities. The Permanent Court of International Justice adjudicates disputes between nations, including water rights litigation. [ 17 ] An estimated 3600 water treaties have existed, including the introduction of more than 150 new ones since 1950. [ 16 ] Transboundary water agreements, like treaties, are oftentimes focused on water infrastructure and quality. [ 18 ] Water resource treaties encompass many types of water like surface water, groundwater, watercourses, and dams. [ 19 ] [ 20 ] When a water resource can be shared equally, like a river acting as a border between nations, there tends to be less conflict than upstream/downstream water resource sharing agreements. [ 21 ] Sometimes treaties establish joint committees between the two or more nations to oversee all water sharing and to ensure that treaty agreements are being met. Two examples of this are the 1996 Ganges Treaty between India and Bangladesh and the 1955 Great Lakes Basin Compact between the United States and Canada. [ 22 ] [ 23 ] With increasing water scarcity and competition for water resources due to climate change and diminished water quality, there has been an increase in international water-based conflict. [ 18 ]
Another example of a water resource interstate agreement is through multi-country agreements to get funding for water resource projects such as building hydropower dams. In Sub-Saharan African countries, China has financed many hydropower projects. [ 24 ]
In Water Resource Policy, covenants and declarations are nonbinding goals for reaching universal human access to water for drinking and sanitation purposes. The United Nations has adopted three covenants and declarations: the 1948 Declaration of Human Rights , the 1966 International Covenant on Civil and Political Rights , and the 1966 International Covenant on Economic, Social, and Cultural Rights . [ 25 ] Since the 1996 International Covenant on Economic, Social, and Cultural Rights declaration, all 191 UN member states have also signed the Millennium Development Goals , which is a further commitment to combat health inequalities. [ 26 ] Access to safe and clean water for drinking and sanitation were fully declared human rights on July 28, 2010 through the UN General Assembly resolution A/RES/64/292. [ 27 ]
Water management rules and regulations dictate different national standards for water quality, like drinking water and environmental water quality standards. For example, in the United States, the Safe Drinking Water Act authorizes the Environmental Protection Agency to set the national standards for safe drinking water and set regulations for contaminants. [ 28 ] Within the European Union , the European Environment Agency enacted the Water Framework Directive in 2000 to regulate water resource planning, management, and protection. [ 29 ] In India, the Ministry of Environment and Forests sets the water management policies that the Central Pollution Control Board and the State Pollution Control Boards then enforce. [ 30 ] The Ministry for Environmental Protection directions national efforts for water management and regulation in China , like the Law on Prevention and Control of Water Pollution. [ 31 ]
Several global organizations have created aid programs and diplomatic efforts to see that progress is being made towards achieving global covenants and declarations regarding water resource access. Because health is closely tied to drinking water and sanitation access, UNICEF and the World Health Organization formed the Joint Monitoring Programme for Water Supply and Sanitation focused exclusively on monitoring and reporting progress on water, sanitation and hygiene goals as dictated by the UN. [ 32 ] In 1977, the United Nations convened for a Conference on Water in Mar del Plata to develop recommendations for national water policy. [ 33 ] Subsequently, the United Nations declared the 1980s as the International Drinking-water Supply and Sanitation Decade. [ 34 ] In 2000, the UN sanctioned a task force led by UNESCO , World Water Assessment Programme, to report on worldwide freshwater use and sustainability in the World Water Development Report. [ 35 ] In 2003, UN-Water was formed as an interagency coordination tool to help countries achieve their water resource goals as set by the Millennium Development Goals and make global water governance frameworks. [ 36 ] Additionally, the United Nations declared 2013 as the International Year of Water Cooperation. [ 37 ] As well as the United Nations' interest in water resource policy for the benefit of human health, the United Nations Environmental Programme has also done work to improve international water quality. [ 38 ]
Non-profits and non-governmental organizations also play a role in water resource policy. For example, the World Water Council is an international think tank established in 1996 to help countries and stakeholders with water resource management strategies. [ 39 ] Additionally, the US Agency for International Development ( USAID ) developed a Water and Development Strategy in 2013 to help people improve water supply, sanitation, and hygiene ( WASH ) programs and help with water resource management. [ 40 ]
Water Resource Policy also encompasses the economic exchange of water, known as virtual water . The term virtual water is used to understand and quantify the volume of water required for a product or service. [ 41 ] For example, when determining the virtual water trade for agricultural goods, the trade flow rate (ton/yr) would be multiplied by the virtual water content (m 3 /ton) of each type of produce or livestock to determine how much water was exchanged in addition to the good. [ 42 ] According to these calculations for virtual water, India, the United States, and China are the top national consumers for virtual water. [ 43 ] Critiques for this method have questioned virtual water's relevance in creating water resource policy, but understanding the trade of water may be useful for countries facing water scarcity to prioritize importation of virtual water instead of exportation of water-intensive goods and services. [ 43 ]
The World Business Council for Sustainable Development engages stakeholders in H2OScenarios [ 44 ] that consider various alternative policies and their effects.
In June 2011 in Geneva, the Future of Water Virtual Conference addressed water resource sustainability. Issues raised included: water infrastructure monitoring, [ 45 ] global water security , potential resource wars, interaction between water, energy, food and economic activity, the "true value" of "distribution portions of available water" and a putative "investment gap" in water infrastructure. [ 46 ] [ 47 ] It was asserted that climate change will affect scarcity of water but the water security presentation emphasized that a combined effect with population growth "could be devastating". [ 46 ] Identified corporate water related risks include physical supply, regulatory and product reputation. [ 46 ] : 23
This forum indicated policy concerns with: trade barriers, price supports, treatment of water as a free good creates underpricing of 98% of water, [ 46 ] : 2 need to intensify debate, and need to harmonize public/private sectors [ 46 ] : 28
Freshwater resources on earth are under increasing stress and depletion because of pollution, climate change, and consumptive use. [ 12 ]
Water can produce a natural disaster in the form of tsunamis , hurricanes , rogue waves and storm surge . Land-based floods can originate from infrastructural issues like bursting dams or levee failure during surges, as well as environmental phenomena like rivers overflowing their banks during increased rainfall events, urban stormwater flooding, or snowmelt. [ 48 ] [ 49 ] [ 50 ] The increased magnitude and frequency of floods are a result of urbanization and climate change. [ 50 ] [ 49 ] Urbanization increases stormwater runoff during large rain events. Surface runoff is water that flows when heavy rains do not infiltrate soil; excess water from rain, meltwater, or other sources flowing over the land. This is a major component of the water cycle. [ 51 ] Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source . When runoff flows along the ground, it can pick up soil contaminants including, but not limited to petroleum, pesticides, or fertilizers that become discharge or nonpoint source pollution. [ 52 ] [ 13 ] [ 53 ]
Water resource policy encompasses flood risk management and development of infrastructure to mitigate damages from floods. [ 48 ] Water resource policy solutions to flooding include land drainage for agriculture, urban planning focused on flood prevention, rainwater harvesting, and permeable surfacing of developed areas. [ 49 ]
A drought is defined as a period of dry conditions with either less precipitation or more depleted water reserves than normal. [ 54 ] Because droughts are defined relative to the area's normal weather patterns and water availability, the definition varies from place to place. Overall, defining a drought takes into consideration 1.) the duration, intensity, and area of lessened precipitation or water availability and 2.) the estimated environmental, social and economic impact of the limited water. [ 54 ] For example, in Colorado, paleohydrologic data, or tree rings from areas affected by drought, have been used to define drought extent and understand the impact of past droughts to improve future water resource planning and decision making. [ 55 ]
With climate change, the frequency and intensity of droughts have been increasing but water resource policy is typically reactive instead of proactive. [ 56 ] Droughts have negative economic impacts on many sectors including agriculture, environment, energy production and transportation. [ 56 ] Local and national governments normally respond to droughts once they happen and are in crisis mode, whereas a robust policy would include early drought monitoring systems, preparedness plans, energy response programs, and impact assessment and management procedures to help mitigate the effects of drought on the economy and the environment. [ 56 ] Different nations have different policies regarding national droughts. [ 57 ] [ 58 ] [ 59 ] In 2013, the High-level Meeting on National Drought Policy (HMNDP) was organized by the World Meteorological Organization , the Secretariat of the United Nations Convention to Combat Desertification (UNCCD) and the Food and Agriculture Organization of the United Nations (FAO) to help nations develop drought preparedness policies and plans for international emergency relief efforts in the event of droughts. [ 56 ] There were 414 participants from 87 countries that unanimously adopted the HMNDP declaration at the end of the meeting rallying national governments to implement drought management policies. [ 60 ]
The oceans provide many important resources for the planet and humans including: transportation, marine life, food, minerals, oil, natural gas, and recreation. [ 61 ] Water resource policy involving the ocean includes jurisdiction and regulation issues, pollution regulation and reduction, over exploitation prevention, and desalination to make drinking water. [ 61 ] [ 62 ]
National jurisdictions of the oceans are dictated by coastal proximity. Oceans along coastlines of nations are considered territories of that nation. For the first 12 nautical miles away from the nation's coastal border, the country has rights to the ocean for its resources, including fish and minerals, and it considered a continuation of that nation's territory. [ 63 ] The countries' economic zone , consisting of both the water column and the seafloor, continues out for 200 nautical miles where they are still entitled to the areas' resources. [ 63 ] On the other hand, the Antarctic and Southern Oceans are shared by 45 state parties under the Antarctic Treaty , so the status and ownership of Antarctic and Southern Ocean resources is unclear legally. [ 64 ] Additionally, some areas are conserved as Marine Protected Areas (MPAs) and resource exploitation is prohibited. For example, by 1997 off the coast of California, there were 103 MPAs. [ 65 ]
The oceans are becoming polluted and exploited for resources. [ 61 ] With increasing carbon dioxide concentrations in the atmosphere from burning fossil fuels, the oceans are experiencing acidification . [ 66 ] Decreasing the pH of the ocean makes it more difficult for marine organisms, like coral reefs , to make their calcium carbonate shells. [ 66 ] Additionally, pollution is threatening oceanic resources, especially near coasts. [ 61 ] Oil rigs and undersea mineral extraction can create problems that affect shorelines, marine life, fisheries and human safety. Decommissioning of such operations has another set of issues. Rigs-to-reefs is a proposal for using obsolete oil rigs as substrate for coral reefs that has failed to reach consensus. There have been oil tanker accidents and oil pipeline spills like the Exxon Valdez oil spill and the Deepwater Horizon oil spill . [ 61 ] Ballast water , fuel/oil leaks and trash originating from ships foul harbors, reefs and estuaries pollute the oceans. Ballast water may contain toxins, invasive plants, animals, viruses, and bacteria. Additionally, marine debris , or industrially processed materials that have been dumped in the oceans, threatens the wellbeing and biodiversity of marine organisms. [ 67 ] Along coasts, oceans are threatened by land runoff that includes fertilizers, insecticides, chemicals, and organic pollutants that can cause algal blooms and dead zones . [ 61 ]
Fisheries also have an effect on oceans and can fall under water resource policy rules. According to the UN Food and Agriculture Organization (FAO), 87% of the fisheries worldwide are either fully exploited or overexploited. [ 68 ] Regional fisheries management organizations (RFMOs) control and oversee high sea fisheries under the UN Convention of the Law of the Sea (UNCLOS) and the UN FishStocks Agreement. [ 68 ] Poor management by RFMOs, government subsidies for fish, and illegal fish catches have contributed to overfishing and over exploitation of ocean resources. [ 68 ] Ecosystem-based fishery management (EBFM) is an attempt to correct some RFMO mismanagement by limiting biomass that is allowed to be removed by fisheries, and by making sure fishing is more targeted for the desired species. [ 69 ] One problem EBFM tries to eliminate is bycatch , or unintentional catching of the wrong fish species. [ 69 ] For example, white marlin , an endangered billfish, is mostly accidentally caught and killed by swordfish and tuna longline fisheries. [ 69 ]
Desalination of seawater is becoming a resource for coastal nations needing freshwater for industry and drinking, particularly areas with over exploited groundwater aquifers and surface water, pollution of freshwater, or unreliable water supply due to climate change. [ 62 ] Desalination is particularly popular in arid, water-stressed regions like Egypt, Jordan, Kuwait, Cyprus, Israel, Saudi Arabia, United Arab Emirates, Australia, and California, US. [ 70 ] [ 71 ] [ 72 ] [ 62 ]
Surface water and groundwater can be studied and managed as separate resources as a single resource in multiple forms. [ 73 ] Jurisdictions typically distinguish three recognized groundwater classifications: subterranean streams, underflow of surface waters, and percolating groundwater. [ 74 ]
Drinking water and water for utilitarian uses such as washing, crop cultivation and manufacture is competed for by various constituencies:
Regulatory bodies address piped waste water discharges to surface water that include riparian and ocean ecosystems. [ 76 ] These review bodies are charged with protecting wilderness ecology, wildlife habitat, drinking water, agricultural irrigation and fisheries. Stormwater discharge can carry fertilizer residue and bacterial contamination from domestic and wild animals. [ 77 ] They have the authority to make orders which are binding upon private actors such as international corporations [ 78 ] and do not hesitate to exercise the police powers of the state. Water agencies have statutory mandate which in many jurisdictions is resilient to pressure from constituents and lawmakers in which they on occasion stand their ground despite heated opposition from agricultural interests [ 79 ] On the other hand, the Boards [ who? ] enjoy strong support from environmental concerns such as Greenpeace,Heal the Ocean and Channelkeepers. [ citation needed ]
Water quality issues or sanitation concerns reuse or water recycling and pollution control which in turn breaks out into stormwater and wastewater.
Wastewater is water that has been discharged from human use. The primary discharges flow from the following sources: residences, commercial properties, industry, and agriculture.
Sewage is technically wastewater contaminated with fecal and similar animal waste byproducts, but is frequently used as a synonym for wastewater. Origination includes cesspool and sewage outfall pipes.
Water treatment is subject to the same overlapping jurisdictional constraints which affect other aspects of water policy. [ 80 ] For instance, levels of chloramines with their resulting toxic trihalomethane by-product are subject to Federal guidelines even though water management implementing those policy constraints are carried out by local water boards. [ 81 ]
The human right to water and sanitation (HRWS) is a principle stating that clean drinking water and sanitation are a universal human right because of their high importance in sustaining every person's life. [ 82 ] It was recognized as a human right by the United Nations General Assembly on 28 July 2010. [ 83 ] The HRWS has been recognized in international law through human rights treaties , declarations and other standards. Some commentators have based an argument for the existence of a universal human right to water on grounds independent of the 2010 General Assembly resolution, such as Article 11.1 of the International Covenant on Economic, Social and Cultural Rights (ICESCR); among those commentators, those who accept the existence of international ius cogens and consider it to include the Covenant's provisions hold that such a right is a universally binding principle of international law. Other treaties that explicitly recognize the HRWS include the 1979 Convention on the Elimination of All Forms of Discrimination Against Women (CEDAW) and the 1989 Convention on the Rights of the Child (CRC).
The clearest definition of the human right to water was issued by the United Nations Committee on Economic, Social and Cultural Rights in General Comment 15 drafted in 2002. [ 84 ] It was a non-binding interpretation that access to water was a condition for the enjoyment of the right to an adequate standard of living , inextricably related to the right to the highest attainable standard of health, and therefore a human right. It stated: "The human right to water entitles everyone to sufficient, safe, acceptable, physically accessible and affordable water for personal and domestic uses." [ 85 ]
The first resolutions about the HRWS were passed by the UN General Assembly and the UN Human Rights Council in 2010. [ 86 ] They stated that there was aman right to sanitation connected to the human right to water, since the lack of sanitation reduces the quality of water downstream, so subsequent discussions have continued emphasizing both rights together. In July 2010, United Nations (UN) General Assembly Resolution 64/292 reasserted the human right to receive safe, affordable, and clean accessible water and sanitation services. [ 87 ] During that General Assembly, it stated that for the comprehension of enjoyment in life and all human rights, safe and clean drinking water as well as sanitation is acknowledged as a human right. [ 88 ] General Assembly Resolution 64/292's assertion of a free human right of access to safe and clean drinking water and sanitation raises issues regarding governmental rights to control and responsibilities for securing that water and sanitation. The United Nations Development Programme has stated that broad recognition of the significance of accessing dependable and clean water and sanitation services will promote wide expansion of the achievement of a healthy and fulfilling life. [ 89 ] [ 90 ] [ 91 ] A revised UN resolution in 2015 highlighted that the two rights were separate but equal. [ 85 ]
The HRWS obliges governments to ensure that people can enjoy quality, available, acceptable, accessible, and affordable water and sanitation. [ 92 ] Affordability of water considers the extent to which the cost of water becomes inhibitive such that it requires one to sacrifice access to other essential goods and services. [ 93 ] Generally, a rule of thumb for the affordability of water is that it should not surpass 3–5% of households' income. [ 94 ] Accessibility of water considers the time taken, convenience in reaching the source and risks involved while getting to the source of water. [ 93 ] Water must be accessible to every citizen, meaning that water should not be further than 1,000 meters or 3,280 feet and must be within 30 minutes. [ 95 ] Availability of water considers whether the supply of water is available in adequate amounts, reliable and sustainable. [ 93 ] Quality of water considers whether water is safe for consumption, including for drinking or other activities. [ 93 ] For acceptability of water, it must not have any odor and should not consist of any color. [ 82 ]
Policies are implemented by organizational entities created by government exercise of state power. However, all such entities are subject to constraints upon their autonomy. [ 80 ]
Subject matter and geographic jurisdiction are distinguishable. [ 96 ] The jurisdiction of any water agency is limited by political boundaries and by enabling legislation. In some cases, limits target specific types of uses (wilderness, agricultural, urban-residential, urban-commercial, etc.) A second part of jurisdictional limitation governs the subject matter that the agency controls, such as flood control, water supply and sanitation, etc. In many locations, agencies may face unclear or overlapping authority, increasing conflicts and delaying conflict resolution.
As reported by the non-partisan Civil Society Institute , a 2005 US Congressional study on water supply was suppressed and became the target of a Freedom of Information Act (FOIA) litigation. [ 97 ]
One jurisdiction's projects may cause problems in other jurisdictions. For instance, Monterey County, California controls a body of water that acts as a reservoir for San Luis Obispo County . The specific responsibilities for managing the resource must therefore be negotiated
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Water retention curve is the relationship between the water content , θ , and the soil water potential , ψ. The soil moisture curve is characteristic for different soil types, and is also called the soil moisture characteristic .
It is used to predict soil water storage, plant water supply ( field capacity ) and soil aggregate stability . Due to the hysteretic effect of water filling and draining the pores, different wetting and drying curves may be distinguished.
The general features of a water retention curve can be seen in the figure, in which the volume water content, θ , is plotted against the matric potential, Ψ m {\displaystyle \Psi _{m}} . At potentials close to zero, the soil is close to saturation, and water is held in the soil primarily by capillary forces. As θ decreases, binding of the water becomes stronger, and at small potentials (more negative, approaching wilting point ) water is strongly bound in the smallest of pores, at contact points between grains and as films bound by adsorptive forces around particles.
Sandy soils will involve mainly capillary binding, and will therefore release most of the water at higher potentials, while clayey soils, with adhesive and osmotic binding, will release water at lower (more negative) potentials. At any given potential, peaty soils will usually display much higher moisture contents than clayey soils, which would be expected to hold more water than sandy soils. The water holding capacity of any soil is due to the porosity and the nature of the bonding in the soil.
The shape of water retention curves can be characterized by several models, one of them known as the van Genuchten model: [ 1 ]
where
Based on this parametrization a prediction model for the shape of the unsaturated hydraulic conductivity - saturation - pressure relationship was developed. [ 2 ]
In 1907, Edgar Buckingham created the first water retention curve. [ 2 ] It was measured and made for six soils varying in texture from sand to clay. The data came from experiments made on soil columns 48 inch tall, where a constant water level maintained about 2 inches above the bottom through periodic addition of water from a side tube. The upper ends were closed to prevent evaporation.
The Van Genuchten parameters ( α {\displaystyle \alpha } and n {\displaystyle n} ) can be determined through field or laboratory testing. One of the methods is the instantaneous profile method, [ 3 ] where water content θ {\displaystyle \theta } (or effective saturation S e {\displaystyle Se} ) are determined for a series of suction pressure measurements ψ {\displaystyle \psi } . Due to the non-linearity of the equation, numerical techniques such as the non-linear least-squares method can be used to solve the van Genuchten parameters. [ 4 ] [ 5 ] The accuracy of the estimated parameters will depend on the quality of the acquired dataset ( θ {\displaystyle \theta } and ψ {\displaystyle \psi } ). Structural overestimation or underestimation can occur when water retention curves are fitted with non-linear least squares. In these cases, the representation of water retention curves can be improved in terms of accuracy and uncertainty by applying Gaussian Process regression to the residuals obtained after non-linear least-squares. This is mostly due to the correlation between the data points, which is accounted for with Gaussian Process regression through the kernel function. [ 6 ]
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A water sampler is a device for field collection of one or more samples of water for testing. There are many different designs of water samplers. Selection or a particular sampler type depends on the type of analysis to be performed (e.g. ambient water quality or wastewater ), the type of water source (e.g. a lake or pond, small stream or large river, coastal waters or deep ocean) and other factors such as ambient environmental conditions (e.g. collection of stormwater during a rain event vs. ambient water sampling during dry weather). Some sampler devices are designed for manual collection (a grab sample ). Composite samplers can be configured to collect multiple samples over a specified time period or flow regime. [ 1 ] [ 2 ]
This environment -related article is a stub . You can help Wikipedia by expanding it .
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Water scarcity (closely related to water stress or water crisis ) is the lack of fresh water resources to meet the standard water demand. There are two types of water scarcity. One is physical. The other is economic water scarcity . [ 2 ] : 560 Physical water scarcity is where there is not enough water to meet all demands. This includes water needed for ecosystems to function. Regions with a desert climate often face physical water scarcity. [ 3 ] Central Asia , West Asia , and North Africa are examples of arid areas. Economic water scarcity results from a lack of investment in infrastructure or technology to draw water from rivers, aquifers , or other water sources. It also results from weak human capacity to meet water demand. [ 2 ] : 560 Many people in Sub-Saharan Africa are living with economic water scarcity. [ 4 ] : 11
There is enough freshwater available globally and averaged over the year to meet demand. As such, water scarcity is caused by a mismatch between when and where people need water, and when and where it is available. [ 5 ] This can happen due to an increase in the number of people in a region, changing living conditions and diets, and expansion of irrigated agriculture . [ 6 ] [ 7 ] [ 8 ] Climate change (including droughts or floods ), deforestation , water pollution and wasteful use of water can also mean there is not enough water. [ 9 ] These variations in scarcity may also be a function of prevailing economic policy and planning approaches.
Water scarcity assessments look at many types of information. They include green water ( soil moisture ), water quality , environmental flow requirements, and virtual water trade . [ 8 ] Water stress is one parameter to measure water scarcity. It is useful in the context of Sustainable Development Goal 6 . [ 10 ] Half a billion people live in areas with severe water scarcity throughout the year, [ 5 ] [ 8 ] and around four billion people face severe water scarcity at least one month per year. [ 5 ] [ 11 ] Half of the world's largest cities experience water scarcity. [ 11 ] There are 2.3 billion people who reside in nations with water scarcities (meaning less than 1700 m 3 of water per person per year). [ 12 ] [ 13 ] [ 14 ]
There are different ways to reduce water scarcity. It can be done through supply and demand side management, cooperation between countries and water conservation . Expanding sources of usable water can help. Reusing wastewater and desalination are ways to do this. Others are reducing water pollution and changes to the virtual water trade.
Water scarcity has been defined as the " volumetric abundance, or lack thereof, of freshwater resources " and it is thought to be "human-driven". [ 15 ] : 4 This can also be called "physical water scarcity". [ 4 ] There are two types of water scarcity. One is physical water scarcity and the other is economic water scarcity . [ 2 ] : 560 Some definitions of water scarcity look at environmental water requirements. This approach varies from one organization to another. [ 15 ] : 4
Related concepts are water stress and water risk . The CEO Water Mandate, an initiative of the UN Global Compact , proposed to harmonize these in 2014. [ 15 ] : 2 In their discussion paper they state that these three terms should not be used interchangeably. [ 15 ] : 3
Some organizations define water stress as a broader concept. It would include aspects of water availability, water quality and accessibility. Accessibility depends on existing infrastructure. It also depends on whether customers can afford to pay for the water. [ 15 ] : 4 Some experts call this economic water scarcity . [ 4 ]
The FAO defines water stress as the "symptoms of water scarcity or shortage". Such symptoms could be "growing conflict between users, and competition for water, declining standards of reliability and service, harvest failures and food insecurity". [ 17 ] : 6 This is measured with a range of Water Stress Indices.
A group of scientists provided another definition for water stress in 2016: "Water stress refers to the impact of high water use (either withdrawals or consumption) relative to water availability." [ 1 ] This means water stress would be a demand-driven scarcity .
Experts have defined two types of water scarcity. One is physical water scarcity. The other is economic water scarcity. These terms were first defined in a 2007 study led by the International Water Management Institute . This examined the use of water in agriculture over the previous 50 years. It aimed to find out if the world had sufficient water resources to produce food for the growing population in the future. [ 4 ] [ 17 ] : 1
Physical water scarcity occurs when natural water resources are not enough to meet all demands. This includes water needed for ecosystems to function well. Dry regions often suffer from physical water scarcity. Human influence on climate has intensified water scarcity in areas where it was already a problem. [ 18 ] It also occurs where water seems abundant but where resources are over-committed. One example is overdevelopment of hydraulic infrastructure . This can be for irrigation or energy generation . There are several symptoms of physical water scarcity. They include severe environmental degradation , declining groundwater and water allocations favouring some groups over others. [ 17 ] : 6
Water is scarce in densely populated arid areas . These are projected to have less than 1000 cubic meters available per capita per year. Examples are Central and West Asia, and North Africa). [ 3 ] A study in 2007 found that more than 1.2 billion people live in areas of physical water scarcity. [ 19 ] This water scarcity relates to water available for food production, rather than for drinking water which is a much smaller amount. [ 3 ] [ 20 ]
Some academics propose a separate type of water scarcity termed ecological water scarcity [ 21 ] though some publications argue that this falls within the definition of physical water scarcity. [ 17 ] [ 4 ] It would focus on the water demand of ecosystems, referring to the minimum quantity and quality of water discharge needed to maintain sustainable and functional ecosystems. Results from a modelling study in 2022 show that northern China suffered more severe ecological water scarcity than southern China. The driving factor of ecological water scarcity in most provinces was water pollution rather than human water use. [ 21 ]
Economic water scarcity is due to a lack of investment in infrastructure or technology to draw water from rivers, aquifers, or other water sources. It also reflects insufficient human capacity to meet the demand for water. [ 22 ] : 560 It causes people without reliable water access to travel long distances to fetch water for household and agricultural uses. Such water is often unclean.
The United Nations Development Programme says economic water scarcity is the most common cause of water scarcity. This is because most countries or regions have enough water to meet household, industrial, agricultural, and environmental needs. But they lack the means to provide it in an accessible manner. [ 23 ] Around a fifth of the world's population currently live in regions affected by physical water scarcity. [ 23 ]
A quarter of the world's population is affected by economic water scarcity. It is a feature of much of Sub-Saharan Africa. [ 4 ] : 11 So better water infrastructure there could help to reduce poverty . Investing in water retention and irrigation infrastructure would help increase food production. This is especially the case for developing countries that rely on low-yield agriculture. [ 24 ] Providing water that is adequate for consumption would also benefit public health. [ 25 ] This is not only a question of new infrastructure. Economic and political intervention are necessary to tackle poverty and social inequality. The lack of funding means there is a need for planning. [ 26 ]
The emphasis is usually on improving water sources for drinking and domestic purposes. But more water is used for purposes such as bathing, laundry, livestock and cleaning than drinking and cooking. [ 25 ] This suggests that too much emphasis on drinking water addresses only part of the problem. So it can limit the range of solutions available. [ 25 ]
There are several indicators for measuring water scarcity. One is the water use to availability ratio. This is also known as the criticality ratio. Another is the IWMI Indicator. This measures physical and economic water scarcity. Another is the water poverty index. [ 8 ]
"Water stress" is a criterion to measure water scarcity. Experts use it in the context of Sustainable Development Goal 6 . [ 10 ] A report by the FAO in 2018 provided a definition of water stress. It described it as "the ratio between total freshwater withdrawn (TFWW) by all major sectors and total renewable freshwater resources (TRWR), after taking into account environmental flow requirements (EFR)". This means that the value for TFWW is divided by the difference between TRWR minus EFR. [ 28 ] : xii Environmental flows are water flows required to sustain freshwater and estuarine ecosystems . A previous definition in Millennium Development Goal 7, target 7.A, was simply the proportion of total water resources used, without taking EFR into consideration. [ 28 ] : 28 This definition sets out several categories for water stress. Below 10% is low stress; 10-20% is low-to-medium; 20-40% medium-to-high; 40-80% high; above 80% very high. [ 29 ]
Indicators are used to measure the extent of water scarcity. [ 30 ] One way to measure water scarcity is to calculate the amount of water resources available per person each year. One example is the "Falkenmark Water Stress Indicator". This was developed by Malin Falkenmark . This indicator says a country or region experiences "water stress" when annual water supplies drop below 1,700 cubic meters per person per year. [ 31 ] Levels between 1,700 and 1,000 cubic meters will lead to periodic or limited water shortages. When water supplies drop below 1,000 cubic meters per person per year the country faces "water scarcity". However, the Falkenmark Water Stress Indicator does not help to explain the true nature of water scarcity. [ 3 ]
It is also possible to measure water scarcity by looking at renewable freshwater . Experts use it when evaluating water scarcity. This metric can describe the total available water resources each country contains. This total available water resource gives an idea of whether a country tend to experience physical water scarcity. [ 32 ] This metric has a drawback because it is an average. Precipitation delivers water unevenly across the planet each year. So annual renewable water resources vary from year to year. This metric does not describe how easy it is for individuals, households, industries or government to access water. Lastly this metric gives a description of a whole country. So it does not accurately portray whether a country is experiencing water scarcity. For example, Canada and Brazil both have very high levels of available water supply. But they still face various water-related problems. [ 32 ] Some tropical countries in Asia and Africa have low levels of freshwater resources.
Water scarcity assessments must include several types of information. They include data on green water ( soil moisture ), water quality , environmental flow requirements, globalisation, and virtual water trade . [ 8 ] Since the early 2000s, water scarcity assessments have used more complex models. These benefit from spatial analysis tools. Green-blue water scarcity is one of these. Footprint-based water scarcity assessment is another. Another is cumulative abstraction to demand ratio, which considers temporal variations. Further examples are LCA -based water stress indicators and integrated water quantity–quality environment flow. [ 8 ] Since the early 2010s assessments have looked at water scarcity from both quantity and quality perspectives. [ 33 ]
A successful assessment will bring together experts from several scientific discipline. These include the hydrological, water quality, aquatic ecosystem science, and social science communities. [ 8 ]
The United Nations estimates that only 200,000 cubic kilometers of the total 1.4 billion cubic kilometers of water on Earth is freshwater available for human consumption. A mere 0.014% of all water on Earth is both fresh and easily accessible . [ 34 ] Of the remaining water, 97% is saline, and a little less than 3% is difficult to access. The fresh water available to us on the planet is around 1% of the total water on earth. [ 35 ] The total amount of easily accessible freshwater on Earth is 14,000 cubic kilometers. This takes the form of surface water such as rivers and lakes or groundwater , for example in aquifers . Of this total amount, humanity uses and resuses just 5,000 cubic kilometers. Technically, there is a sufficient amount of freshwater on a global scale. So in theory there is more than enough freshwater available to meet the demands of the current world population of 8 billion people. There is even enough to support population growth to 9 billion or more. But unequal geographical distribution and unequal consumption of water makes it a scarce resource in some regions and groups of people.
Rivers and lakes provide common surface sources of freshwater. But other water resources such as groundwater and glaciers have become more developed sources of freshwater. They have become the main source of clean water. Groundwater is water that has pooled below the surface of the Earth. It can provide a usable quantity of water through springs or wells. These areas of groundwater are also known as aquifers. It is becoming harder to use conventional sources because of pollution and climate change. So people are drawing more and more on these other sources. Population growth is encouraging greater use of these types of water resources. [ 32 ]
In 2019 the World Economic Forum listed water scarcity as one of the largest global risks in terms of potential impact over the next decade. [ 36 ] Water scarcity can take several forms. One is a failure to meet demand for water, partially or totally. Other examples are economic competition for water quantity or quality, disputes between users, irreversible depletion of groundwater , and negative impacts on the environment .
About half of the world's population currently experience severe water scarcity for at least some part of the year. [ 37 ] Half a billion people in the world face severe water scarcity all year round. [ 5 ] Half of the world's largest cities experience water scarcity. [ 11 ] Almost two billion people do not currently have access to clean drinking water.
[ 38 ] [ 39 ] A study in 2016 calculated that the number of people suffering from water scarcity increased from 0.24 billion or 14% of global population in the 1900s to 3.8 billion (58%) in the 2000s. [ 1 ] This study used two concepts to analyse water scarcity. One is shortage, or impacts due to low availability per capita. The other is stress, or impacts due to high consumption relative to availability.
In the 20th century, water use has been growing at more than twice the rate of the population increase. Specifically, water withdrawals are likely to rise by 50 percent by 2025 in developing countries, and 18 per cent in developed countries. [ 40 ] One continent, for example, Africa , has been predicted to have 75 to 250 million inhabitants lacking access to fresh water. [ 41 ] By 2025, 1.8 billion people will be living in countries or regions with absolute water scarcity, and two-thirds of the world population could be under stress conditions. [ 42 ] By 2050, more than half of the world's population will live in water-stressed areas, and another billion may lack sufficient water, MIT researchers find. [ 43 ]
With the increase in global temperatures and an increase in water demand, six out of ten people are at risk of being water-stressed. The drying out of wetlands globally, at around 67%, was a direct cause of a large number of people at risk of water stress. As global demand for water increases and temperatures rise, it is likely that two thirds of the population will live under water stress in 2025. [ 44 ] [ 35 ] : 191
According to a projection by the United Nations, by 2040, there can be about 4.5 billion people affected by a water crisis (or water scarcity). Additionally, with the increase in population, there will be a demand for food, and for the food output to match the population growth, there would be an increased demand for water to irrigate crops. [ 45 ] The World Economic Forum estimates that global water demand will surpass global supply by 40% by 2030. [ 46 ] [ 47 ] Increasing the water demand as well as increasing the population results in a water crisis where there is not enough water to share in healthy levels. The crises are not only due to quantity but quality also matters.
A study found that 6-20% of about 39 million groundwater wells are at high risk of running dry if local groundwater levels decline by a few meters. In many areas and with possibly more than half of major aquifers [ 48 ] this would apply if they simply continue to decline. [ 49 ] [ 50 ]
Controllable factors such as the management and distribution of the water supply can contribute to scarcity. A 2006 United Nations report focuses on issues of governance as the core of the water crisis. The report noted that: "There is enough water for everyone". It also said: "Water insufficiency is often due to mismanagement, corruption, lack of appropriate institutions, bureaucratic inertia and a shortage of investment in both human capacity and physical infrastructure". [ 52 ]
Economists and others have argued that a lack of property rights , government regulations and water subsidies have given rise to the situation with water. These factors cause prices to be too low and consumption too high, making a point for water privatization . [ 53 ] [ 54 ] [ 55 ]
The clean water crisis is an emerging global crisis affecting approximately 785 million people around the world. [ 56 ] 1.1 billion people lack access to water and 2.7 billion experience water scarcity at least one month in a year. 2.4 billion people suffer from contaminated water and poor sanitation. Contamination of water can lead to deadly diarrheal diseases such as cholera and typhoid fever and other waterborne diseases . These account for 80% of illnesses around the world. [ 57 ]
Using water for domestic, food and industrial uses has major impacts on ecosystems in many parts of the world. This can apply even to regions not considered "water scarce". [ 3 ] Water scarcity damages the environment in many ways. These include adverse effects on lakes, rivers, ponds, wetlands and other fresh water resources. Thus results in water overuse because water is scarce. This often occurs in areas of irrigation agriculture. It can harm the environment in several ways. This includes increased salinity , nutrient pollution , and the loss of floodplains and wetlands . [ 23 ] [ 58 ] Water scarcity also makes it harder to use flow to rehabilitate urban streams. [ 59 ]
Through the last hundred years, more than half of the Earth's wetlands have been destroyed and have disappeared. [ 9 ] These wetlands are important as the habitats of numerous creatures such as mammals, birds, fish, amphibians, and invertebrates . They also support the growing of rice and other food crops. And they provide water filtration and protection from storms and flooding. Freshwater lakes such as the Aral Sea in central Asia have also suffered. It was once the fourth largest freshwater lake in the world. But it has lost more than 58,000 square km of area and vastly increased in salt concentration over the span of three decades. [ 9 ]
Subsidence is another result of water scarcity. The U.S. Geological Survey estimates that subsidence has affected more than 17,000 square miles in 45 U.S. states, 80 percent of it due to groundwater usage. [ 60 ]
Vegetation and wildlife need sufficient freshwater. Marshes , bogs and riparian zones are more clearly dependent upon sustainable water supply. Forests and other upland ecosystems are equally at risk as water becomes less available. In the case of wetlands, a lot of ground has been simply taken from wildlife use to feed and house the expanding human population. Other areas have also suffered from a gradual fall in freshwater inflow as upstream water is diverted for human use.
Other impacts include growing conflict between users and growing competition for water. [ 17 ] : 6 Examples for the potential for conflict from water scarcity include: Food insecurity in the Middle East and North Africa Region [ 61 ] and regional conflicts over scarce water resources. [ 62 ]
Around fifty years ago, the common view was that water was an infinite resource. At that time, there were fewer than half the current number of people on the planet. People were not as wealthy as today, consumed fewer calories and ate less meat, so less water was needed to produce their food. They required a third of the volume of water we presently take from rivers. Today, the competition for water resources is much more intense. This is because there are now seven billion people on the planet and their consumption of water-thirsty meat is rising. And industry , urbanization , biofuel crops, and water reliant food items are competing more and more for water. In the future, even more water will be needed to produce food because the Earth's population is forecast to rise to 9 billion by 2050. [ 63 ]
In 2000, the world population was 6.2 billion. The UN estimates that by 2050 there will be an additional 3.5 billion people, with most of the growth in developing countries that already suffer water stress. [ 64 ] This will increase demand for water unless there are corresponding increases in water conservation and recycling . [ 65 ] In building on the data presented here by the UN, the World Bank [ 66 ] goes on to explain that access to water for producing food will be one of the main challenges in the decades to come. It will be necessary to balance access to water with managing water in a sustainable way. At the same time it will be necessary to take the impact of climate change and other environmental and social variables into account. [ 67 ]
In 60% of European cities with more than 100,000 people, groundwater is being used at a faster rate than it can be replenished. [ 68 ]
The increase in the number of people is increasing competition for water. This is depleting many of the world's major aquifers. It has two causes. One is direct human consumption. The other is agricultural irrigation. Millions of pumps of all sizes are currently extracting groundwater throughout the world. Irrigation in dry areas such as northern China , Nepal and India draws on groundwater. And it is extracting groundwater at an unsustainable rate. Many cities have experienced aquifer drops of between 10 and 50 meters. They include Mexico City , Bangkok , Beijing , Chennai and Shanghai . [ 70 ]
Until recently, groundwater was not a highly used resource. In the 1960s, more and more groundwater aquifers developed. [ 71 ] Improved knowledge, technology and funding have made it possible to focus more on drawing water from groundwater resources instead of surface water. These made the agricultural groundwater revolution possible. They expanded the irrigation sector which made it possible to increase food production and development in rural areas. [ 72 ] Groundwater supplies nearly half of all drinking water in the world. [ 73 ] The large volumes of water stored underground in most aquifers have a considerable buffer capacity. This makes it possible to withdraw water during periods of drought or little rainfall. [ 32 ] This is crucial for people that live in regions that cannot depend on precipitation or surface water for their only supplies. It provides reliable access to water all year round. As of 2010, the world's aggregated groundwater abstraction is estimated at 1,000 km 3 per year. Of this 67% goes on irrigation, 22% on domestic purposes and 11% on industrial purposes. [ 32 ] The top ten major consumers of abstracted water make up 72% of all abstracted water use worldwide. They are India, China, United States of America, Pakistan, Iran, Bangladesh, Mexico, Saudi Arabia, Indonesia, and Italy. [ 32 ]
Goundwater sources are quite plentiful. But one major area of concern is the renewal or recharge rate of some groundwater sources. Extracting from non-rewable groundwater sources could exhaust them if they are not properly monitored and managed. [ 74 ] Increasing use of groundwater can also reduce water quality over time. Groundwater systems often show falls in natural outflows, stored volumes, and water levels as well as water degradation. [ 32 ] Groundwater depletion can cause harm in many ways. These include more costly groundwater pumping and changes in salinity and other types of water quality. They can also lead to land subsidence, degraded springs and reduced baseflows.
The main cause of water scarcity as a result of consumption is the extensive use of water in agriculture / livestock breeding and industry . People in developed countries generally use about 10 times more water a day than people in developing countries . [ 77 ] A large part of this is indirect use in water-intensive agricultural and industrial production of consumer goods . Examples are fruit, oilseed crops and cotton. Many of these production chains are globalized, So a lot of water consumption and pollution in developing countries occurs to produce goods for consumption in developed countries. [ 78 ]
Many aquifers have been over-pumped and are not recharging quickly. This does not use up the total fresh water supply. But it means that much has become polluted, salted, unsuitable or otherwise unavailable for drinking, industry and agriculture. To avoid a global water crisis, farmers will have to increase productivity to meet growing demands for food. At the same time industry and cities find will have to find ways to use water more efficiently. [ 79 ]
Business activities such as tourism are continuing to expand. They create a need for increases in water supply and sanitation . This in turn can lead to more pressure on water resources and natural ecosystems . The approximate 50% growth in world energy use by 2040 will also increase the need for efficient water use. [ 79 ] It may means some water use shifts from irrigation to industry. This is because thermal power generation uses water for steam generation and cooling. [ 80 ]
Water pollution (or aquatic pollution) is the contamination of water bodies , with a negative impact on their uses. [ 81 ] : 6 It is usually a result of human activities. Water bodies include lakes , rivers , oceans , aquifers , reservoirs and groundwater . Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources. These are sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater . [ 82 ] Water pollution may affect either surface water or groundwater . This form of pollution can lead to many problems. One is the degradation of aquatic ecosystems . Another is spreading water-borne diseases when people use polluted water for drinking or irrigation . [ 83 ] Water pollution also reduces the ecosystem services such as drinking water provided by the water resource .
Climate change could have a big impact on water resources around the world because of the close connections between the climate and hydrological cycle . Rising temperatures will increase evaporation and lead to increases in precipitation. However there will be regional variations in rainfall . Both droughts and floods may become more frequent and more severe in different regions at different times. There will be generally less snowfall and more rainfall in a warmer climate. [ 86 ] Changes in snowfall and snow melt in mountainous areas will also take place. Higher temperatures will also affect water quality in ways that scientists do not fully understand. Possible impacts include increased eutrophication . Climate change could also boost demand for irrigation systems in agriculture. There is now ample evidence that greater hydrologic variability and climate change have had a profound impact on the water sector, and will continue to do so. This will show up in the hydrologic cycle, water availability, water demand, and water allocation at the global, regional, basin, and local levels. [ 87 ]
The United Nations' FAO states that by 2025 1.9 billion people will live in countries or regions with absolute water scarcity. It says two thirds of the world's population could be under stress conditions. [ 88 ] The World Bank says that climate change could profoundly alter future patterns of water availability and use. This will make water stress and insecurity worse, at the global level and in sectors that depend on water. [ 89 ]
Scientists have found that population change is four times more important than long-term climate change in its effects on water scarcity. [ 44 ]
The continued retreat of glaciers will have a number of different quantitative effects. In areas that are heavily dependent on water runoff from glaciers that melt during the warmer summer months, a continuation of the current retreat will eventually deplete the glacial ice and substantially reduce or eliminate runoff. A reduction in runoff will affect the ability to irrigate crops and will reduce summer stream flows necessary to keep dams and reservoirs replenished. This situation is particularly acute for irrigation in South America, where numerous artificial lakes are filled almost exclusively by glacial melt. [ 90 ] Central Asian countries have also been historically dependent on the seasonal glacier melt water for irrigation and drinking supplies. In Norway, the Alps, and the Pacific Northwest of North America, glacier runoff is important for hydropower .
A review in 2006 stated that "It is surprisingly difficult to determine whether water is truly scarce in the physical sense at a global scale (a supply problem) or whether it is available but should be used better (a demand problem)". [ 95 ]
The International Resource Panel of the UN states that governments have invested heavily in inefficient solutions. These are mega-projects like dams , canals, aqueducts , pipelines and water reservoirs. They are generally neither environmentally sustainable nor economically viable. [ 96 ] According to the panel, the most cost-effective way of decoupling water use from economic growth is for governments to create holistic water management plans . These would take into account the entire water cycle: from source to distribution, economic use, treatment , recycling , reuse and return to the environment.
In general, there is enough water on an annual and global scale. The issue is more of variation of supply by time and by region. Reservoirs and pipelines would deal with this variable water supply. Well-planned infrastructure with demand side management is necessary. Both supply-side and demand-side management have advantages and disadvantages. [ citation needed ]
Lack of cooperation may give rise to regional water conflicts . This is especially the case in developing countries . The main reason is disputes regarding the availability, use and management of water. [ 62 ] One example is the dispute between Egypt and Ethiopia over the Grand Ethiopian Renaissance Dam which escalated in 2020. [ 97 ] [ 98 ] Egypt sees the dam as an existential threat, fearing that the dam will reduce the amount of water it receives from the Nile . [ 99 ]
Water conservation aims to sustainably manage the natural resource of fresh water , protect the hydrosphere , and meet current and future human demand . Water conservation makes it possible to avoid water scarcity. It covers all the policies, strategies and activities to reach these aims. Population, household size and growth and affluence all affect how much water is used.
Wastewater treatment is a process which removes and eliminates contaminants from wastewater . It thus converts it into an effluent that can be returned to the water cycle . Once back in the water cycle, the effluent creates an acceptable impact on the environment. It is also possible to reuse it. This process is called water reclamation . [ 107 ] The treatment process takes place in a wastewater treatment plant. There are several kinds of wastewater which are treated at the appropriate type of wastewater treatment plant. For domestic wastewater the treatment plant is called a Sewage Treatment . Municipal wastewater or sewage are other names for domestic wastewater . For industrial wastewater, treatment takes place in a separate Industrial wastewater treatment , or in a sewage treatment plant. In the latter case it usually follows pre-treatment. Further types of wastewater treatment plants include Agricultural wastewater treatment and leachate treatment plants.
The virtual water trade is the hidden flow of water in food or other commodities that are traded from one place to another. [ 113 ] Other terms for it are embedded or embodied water. The virtual water trade is the idea that virtual water is exchanged along with goods and services. This idea provides a new, amplified perspective on water problems. It balances different perspectives, basic conditions, and interests. This concept makes it possible to distinguish between global, regional, and local levels and their linkages. However, the use of virtual water estimates may offer no guidance for policymakers seeking to ensure they are meeting environmental objectives.
The Consultative Group on International Agricultural Research (CGIAR) published a map showing the countries and regions suffering most water stress. [ 116 ] They are North Africa , the Middle East , [ 117 ] India , Central Asia , China , Chile , Colombia , South Africa , Canada and Australia . Water scarcity is also increasing in South Asia . [ 118 ] As of 2016, about four billion people, or two thirds of the world's population, were facing severe water scarcity. [ 119 ]
The more developed countries of North America , Europe and Russia will not see a serious threat to water supply by 2025 in general. This is not only because of their relative wealth. Their populations will also be more in line with available water resources. [ citation needed ] North Africa, the Middle East, South Africa and northern China will face very severe water shortages. This is due to physical scarcity and too many people for the water that is available. [ citation needed ] Most of South America , Sub-Saharan Africa, southern China and India will face water supply shortages by 2025. For these regions, water scarcity will be due to economic constraints on developing safe drinking water, and excessive population growth . [ citation needed ]
The main causes of water scarcity in Africa are physical and economic water scarcity, rapid population growth, and the effects of climate change on the water cycle . Water scarcity is the lack of fresh water resources to meet the standard water demand . [ 121 ] The rainfall in sub-Saharan Africa is highly seasonal and unevenly distributed, leading to frequent floods and droughts . [ 122 ]
Water scarcity in Yemen (see: Water supply and sanitation in Yemen ) is a growing problem. Population growth and climate change are among the causes. Others are poor water management, shifts in rainfall, water infrastructure deterioration, poor governance, and other anthropogenic effects. As of 2011, water scarcity is having political, economic and social impacts in Yemen. As of 2015, [ 124 ] Yemen is one of the countries suffering most from water scarcity. Most people in Yemen experience water scarcity for at least one month a year.
In Nigeria, some reports have suggested that increase in extreme heat, drought and the shrinking of Lake Chad is causing water shortage and environmental migration. This is forcing thousands to migrate to neighboring Chad and towns. [ 125 ]
A major report in 2019 by more than 200 researchers, found that the Himalayan glaciers could lose 66 percent of their ice by 2100. [ 126 ] These glaciers are the sources of Asia 's biggest rivers – Ganges , Indus , Brahmaputra , Yangtze , Mekong , Salween and Yellow . Approximately 2.4 billion people live in the drainage basin of the Himalayan rivers. [ 127 ] India, China, Pakistan, Bangladesh , Nepal and Myanmar could experience floods followed by droughts in coming decades. In India alone, the Ganges provides water for drinking and farming for more than 500 million people. [ 128 ] [ 129 ] [ 130 ]
Even with the overpumping of its aquifers , China is developing a grain deficit. When this happens, it will almost certainly drive grain prices upward. Most of the 3 billion people projected to be added worldwide by mid-century will be born in countries already experiencing water shortages. Unless population growth can be slowed quickly, it is feared that there may not be a practical non-violent or humane solution to the emerging world water shortage. [ 131 ] [ 132 ]
It is highly likely that climate change in Turkey will cause its southern river basins to be water scarce before 2070, and increasing drought in Turkey . [ 133 ]
In the Rio Grande Valley , intensive agribusiness has made water scarcity worse. It has sparked jurisdictional disputes regarding water rights on both sides of the U.S.-Mexico border . Scholars such as Mexico's Armand Peschard-Sverdrup have argued that this tension has created the need for new strategic transnational water management . [ 135 ] Some have likened the disputes to a war over diminishing natural resources . [ 136 ] [ 137 ]
The west coast of North America , which gets much of its water from glaciers in mountain ranges such as the Rocky Mountains and Sierra Nevada , is also vulnerable. [ 138 ] [ 139 ]
By far the largest part of Australia is desert or semi-arid lands commonly known as the outback . [ 140 ] Water restrictions are in place in many regions and cities of Australia in response to chronic shortages resulting from drought . Environmentalist Tim Flannery predicted that Perth in Western Australia could become the world's first ghost metropolis . This would mean it was an abandoned city with no more water to sustain its population, said Flannery, who was Australian of the year 2007. [ 141 ] In 2010, Perth suffered its second-driest winter on record [ 142 ] and the water corporation tightened water restrictions for spring. [ 143 ]
Some countries have already proven that decoupling water use from economic growth is possible. For example, in Australia, water consumption declined by 40% between 2001 and 2009 while the economy grew by more than 30%. [ 96 ]
Water scarcity or water crisis in particular countries:
Sustainable Development Goal 6 aims for clean water and sanitation for all. [ 144 ] It is one of 17 Sustainable Development Goals established by the United Nations General Assembly in 2015. The fourth target of SDG 6 refers to water scarcity. It states: "By 2030, substantially increase water-use efficiency across all sectors and ensure sustainable withdrawals and supply of freshwater to address water scarcity and substantially reduce the number of people suffering from water scarcity". [ 10 ]
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Water slide decals (or water transfer decals ) are decals which rely on dextrose residue from the decal paper to bond the decal to a surface. A water-based adhesive layer can be added to the decal to create a stronger bond or may be placed between layers of lacquer to create a durable decal transfer. The paper also has a layer of glucose film added prior to the dextrose layer which gives it adhesive properties; the dextrose layer gives the decal the ability to slide off the paper and onto the substrate ( lubricity ).
Water slide decals are thinner than many other decorative techniques (such as vinyl stickers) and as they are printed, they can be produced to a very high level of detail . As such, they are popular in craft areas such as scale modeling , [ 1 ] as well as for labeling DIY electronics devices, such as guitar pedals .
Previously, water slide decals were professionally printed and only available in supplied designs, but with the advent of printable decal paper for colour inkjet and laser printers , custom decals can now be produced by the hobbyist or small business.
This material -related article is a stub . You can help Wikipedia by expanding it .
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Water softening is the removal of calcium , magnesium , and certain other metal cations in hard water . The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions. Soft water also extends the lifetime of plumbing by reducing or eliminating scale build-up in pipes and fittings. Water softening is usually achieved using lime softening or ion-exchange resins , but is increasingly being accomplished using nanofiltration or reverse osmosis membranes.
The presence of certain metal ions like calcium and magnesium , principally as bicarbonates , chlorides , and sulfates , in water causes a variety of problems. [ 1 ]
Hard water leads to the buildup of limescale , which can foul plumbing , and promote galvanic corrosion . [ 2 ] In industrial scale water softening plants, the effluent flow from the re-generation process can precipitate scale that can interfere with sewage systems. [ 3 ]
The slippery feeling associated with washing in soft water is caused by the weaker attraction of the soap to the water ions when the water has been stripped of its mineral content. The surface of human skin has a light charge that the soap tends to bind with, requiring more effort and a greater volume of water to remove. [ 4 ] Hard water contains calcium or magnesium ions that form insoluble salts upon reacting with soap, leaving a coating of insoluble stearates on tub and shower surfaces, commonly called soap scum . [ 4 ] [ 5 ]
The most common means for removing water hardness rely on ion-exchange resin or reverse osmosis . Other approaches include precipitation methods, such as fluidized bed pellet softening, [ 6 ] and sequestration by the addition of chelating agents. Distillation and reverse osmosis are the most widely used two non-chemical methods of water softening.
Conventional water-softening appliances intended for household use depend on an ion-exchange resin in which "hardness ions"—mainly Ca 2+ and Mg 2+ —are exchanged for sodium ions. [ 7 ] As described by NSF/ANSI Standard 44 , [ 8 ] ion-exchange devices reduce the hardness by replacing magnesium and calcium (Mg 2+ and Ca 2+ ) with sodium or potassium ions (Na + and K + )."
Ion-exchange resins are organic polymers containing anionic functional groups to which the divalent cations (Ca 2+ ) bind more strongly than monovalent cations (Na + ). Inorganic materials called zeolites also exhibit ion-exchange properties. These minerals are widely used in laundry detergents . Resins are also available to remove the carbonate, bicarbonate, and sulfate ions that are absorbed and hydroxide ions that are released from the resin. [ 9 ]
When all the available Na + ions have been replaced with calcium or magnesium ions, the resin must be recharged by eluting the Ca 2+ and Mg 2+ ions using a solution of sodium chloride or sodium hydroxide , depending on the type of resin used. [ 10 ] For anionic resins, regeneration typically uses a solution of sodium hydroxide ( lye ) or potassium hydroxide. The waste waters eluted from the ion-exchange column containing the unwanted calcium and magnesium salts are typically discharged to the sewage system. [ 3 ]
Recharge typically takes the following steps: [ 11 ]
Lime softening is the process in which lime is added to hard water to make it softer. It has several advantages [ further explanation needed ] over the ion-exchange method but is mainly suited to commercial treatment applications. [ 13 ]
Chelators are used in chemical analysis , as water softeners, and are ingredients in many commercial products such as shampoos and food preservatives . Citric acid is used to soften water in soaps, personal care products and laundry detergents . A commonly used synthetic chelator is ethylenediaminetetraacetic acid (EDTA), which may exist as a tetrasodium or disodium salt. Due to environmental and aquatic toxicity concerns regarding widespread use of EDTA in household and personal care products, alternatives such as sodium phytate/ phytic acid , tetrasodium glutamate diacetate and trisodium ethylenediamine disuccinate are finding more prevalent usage.
In this method, water is treated with a calculated amount of washing soda (Na 2 CO 3 ), which converts the chlorides and sulphates of calcium and magnesium into their respective carbonates, which get precipitated.
CaCl 2 + Na 2 CO 3 → CaCO 3 + 2NaCl
MgSO 4 + Na 2 CO 3 → MgCO 3 + Na 2 SO 4
Since Ca 2+ and Mg 2+ exist as nonvolatile salts, they can be removed by distilling the water. Distillation is expensive and energy-inefficient compared to other methods of water softening. Rainwater is soft because it is naturally distilled during the water cycle of evaporation, condensation and precipitation. [ 14 ]
Reverse osmosis uses an applied pressure gradient across a semipermeable membrane to overcome osmotic pressure and remove water molecules from the solution with hardness ions. The membrane has pores large enough to admit water molecules for passage; hardness ions such as Ca 2+ and Mg 2+ will not fit through the pores. The resulting soft water supply is free of hardness ions without any other ions being added. Membranes are a type of water filter requiring regular cleaning or replacement maintenance.
Nanofiltration is a process similar to reverse osmosis in that it involves the use of a semipermeable membrane, though the filter membrane is distinct in that its pores are ≤ 10 nanometers in diameter. The process is often used in conjunction with reverse osmosis filtration, as nanofiltration on its own is not as effective and more expensive than chemical water treatment methods. [ 15 ]
Removing or replacing minerals in hard water is called water softening. An alternative water treatment is called water conditioning, in which minerals remain in the water, but are altered so they do not form scale. Although the United States has standards for measuring the minerals in water, it does not have standards for measuring scale forming ability of water. Instead, US researchers use the German DVGW-W512 protocol. [ 16 ]
Rain water contains dissolved carbon dioxide taken from the atmosphere. Some of the dissolved carbon dioxide reacts with the water to form carbonic acid , which remains in solution. Minerals containing calcium and magnesium form soluble bicarbonates when exposed to carbonic acid. Water containing these minerals is known as "hard water". [ citation needed ]
When hard water is heated in a plumbing system, carbon dioxide goes out of solution, and bicarbonates become carbonates, which are much less soluble. The carbonates bind to plumbing surfaces providing seed crystals for further crystal growth, which build up as hard scale. [ citation needed ]
Some manufacturers claim that the electrical devices they produce can affect the interaction of minerals with water so that the minerals do not bind to surfaces. Since these systems do not work by exchanging ions, like traditional water softeners do, one benefit claimed for the user is the elimination of the need to add salt to the system. Such systems do not remove minerals from the water itself. Rather, they can only alter the downstream effects that the mineral-bearing water would otherwise have. These systems do not fall within the term "water softening" but rather "water conditioning". [ citation needed ]
Electrical precipitation devices cause microscopic mineral crystals to form and remain suspended as they flow with the water, while also acting as seeds for further crystal growth. As water is heated, minerals will crystallize on these seeds, instead of the plumbing system. The dissolved minerals become insoluble solid particles in suspension, passing through the system without binding to plumbing surfaces. [ 19 ]
Claims for magnetic water treatment are not considered to be valid. For instance, no reduction of scale formation was found when such a magnet device was scientifically tested. [ 20 ]
Cold hard water passes through a tank containing tiny polymeric beads with surfaces that allow nucleation of tiny bubbles of carbon dioxide gas. The initial nucleation of the gas bubbles can occur due to depressurization of the hard water as it flows up a water well just like when the top comes off of a beer bottle. Once carbon dioxide leaves the liquid a chemical reaction immediately drives formation of calcium carbonate crystals on the surface of the bubbles. As crystals grow on these seeds they break off in the flow while still of microscopic size. If these tiny particles travel through a water heater, further exsolution of carbon dioxide occurs due to increased temperature and new crystal growth occurs on the particles, rather than on the water heater. Once calcite occurs in the water, new calcite will prefer to form on the old calcite due to the available bonds on the crystals and the proximity and number of calcite surfaces in the water. [ citation needed ]
This process is either called template assisted crystallization (TAC) or nucleation assisted crystallization (NAC). The polymeric beads are polyphosphates ranging in size from 0.5 to 2.0 μm. [ citation needed ] and some have a ceramic coating. Testing at the University of Arizona found TAC to be the most effective at reducing scale formation, followed closely by ion exchange (see chart above). They are more effective than approaches that attempt to sequester ions through application of magnetic or electric fields. The advantages of TAC tanks include simplicity, low maintenance, lack of toxic effluent (like chlorine), and the availability of calcium as a nutrient in drinking water. The disadvantages include that the calcite crystals are not avoided or removed from the water such that areas where water evaporates will still show deposits. It is claimed by manufacturers that these deposits are easier to clean since the calcite forms on seed crystals instead of on the surfaces. [ citation needed ]
The UK's National Health Service recommends a maximum salt intake of 6g, against an actual current intake of 8.1g. The US CDC recommends limiting daily total sodium intake to 2,300 mg per day, [ 21 ] though the average US American consumes 3,500 mg per day. [ 22 ] Because the amount of sodium present in drinking water—even after softening—does not represent a significant percentage of a person's daily sodium intake, the US EPA considers sodium in drinking water to be unlikely to cause adverse health effects. [ 23 ]
A study found the mean concentration of sodium in softened water to be 278 mg/L. [ 24 ] In 2 liters of water—the amount of drinking water typically suggested for an average adult, this constitutes about 22% of the recommended sodium intake by the US CDC and may make a difference to those who need to significantly limit their sodium consumption. [ citation needed ] For those who are on sodium-restricted diets, the use of a reverse osmosis system for drinking water and cooking water will remove sodium along with any other impurities that may be present. [ citation needed ] Potassium chloride can also be used as a regenerant instead of sodium chloride, although it is more costly. For people with impaired kidney function , however, elevated potassium levels, or hyperkalemia , can lead to complications such as cardiac arrhythmia . [ citation needed ]
High levels of water hardness in the home may also be linked to the development of atopic dermatitis (eczema) early in life, [ 25 ] although the actual relationship is correlational at the present and further research is indicated to establish a causal one. However, using water softeners when atopic dermatitis is already established does not reduce the severity of the symptoms. [ 26 ] [ 27 ]
Softened water (measured as residual sodium carbonate index ) in which calcium and magnesium have been partly replaced by sodium is not suitable for irrigation use, as it tends to cause the development of alkali soils . [ 28 ] Non-chemical devices are often used in place of traditional water softening for this application.
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Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen : [ 1 ]
Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy . A version of water splitting occurs in photosynthesis , but hydrogen is not produced. The reverse of water splitting is the basis of the hydrogen fuel cell . Water splitting using solar radiation has not been commercialized.
Electrolysis of water is the decomposition of water (H 2 O) into oxygen (O 2 ) and hydrogen (H 2 ): [ 2 ]
Production of hydrogen from water is energy intensive. Usually, the electricity consumed is more valuable than the hydrogen produced, so this method has not been widely used. In contrast with low-temperature electrolysis, high-temperature electrolysis (HTE) of water converts more of the initial heat energy into chemical energy (hydrogen), potentially doubling efficiency to about 50%. [ citation needed ] Because some of the energy in HTE is supplied in the form of heat, less of the energy must be converted twice (from heat to electricity, and then to chemical form), and so the process is more efficient. [ citation needed ]
High-temperature electrolysis (also HTE or steam electrolysis ) is a method for the production of hydrogen from water with oxygen as a by-product.
A version of water splitting occurs in photosynthesis but the electrons are shunted, not to protons, but to the electron transport chain in photosystem II . The electrons are used to reduce carbon dioxide, which eventually becomes incorporated into sugars.
Photo-excitation of photosystem I initiates electron transfer to a series of electron acceptors, eventually reducing NADP + to NADPH. The oxidized photosystem I captures electrons from photosystem II through a series of steps involving plastoquinone , cytochromes , and plastocyanin . Oxidized photosystem II oxidizes the oxygen-evolving complex (OEC), which converts water into O 2 and protons. [ 3 ] [ 4 ] Since the active site of the OEC contains manganese , much research has aimed at synthetic Mn compounds as catalysts for water oxidation. [ 5 ]
In biological hydrogen production , the electrons produced by the photosystem are shunted not to a chemical synthesis apparatus but to hydrogenases , resulting in formation of H 2 . This biohydrogen is produced in a bioreactor . [ 6 ]
Using electricity produced by photovoltaic systems potentially offers the cleanest way to produce hydrogen, other than nuclear, wind, geothermal, and hydroelectric. Again, water is broken down into hydrogen and oxygen by electrolysis, but the electrical energy is obtained by a photoelectrochemical cell (PEC) process. The system is also named artificial photosynthesis . [ 7 ] [ 8 ] [ 9 ]
Catalysis and proton-relay membranes are often the focus on development. [ 10 ]
The conversion of solar energy into hydrogen by means of water splitting process might be more efficient if it is assisted by photocatalysts suspended in water rather than a photovoltaic or an electrolytic system, so that the reaction takes place in one step. [ 11 ] [ 12 ]
Energetic nuclear radiation can break the chemical bonds of a water molecule. In the Mponeng gold mine , South Africa , researchers found in a naturally high radiation zone a community dominated by Desulforudis audaxviator , a new phylotype of Desulfotomaculum , feeding on primarily radiolytically produced H 2 . [ 13 ]
In thermolysis , water molecules split into hydrogen and oxygen . For example, at 2,200 °C (2,470 K; 3,990 °F) about three percent of all H 2 O are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H 2 , O, O 2 , and OH. Other reaction products like H 2 O 2 or HO 2 remain minor. At the very high temperature of 3,000 °C (3,270 K; 5,430 °F) more than half of the water molecules are decomposed. At ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat. [ 14 ] The high temperature requirements and material constraints have limited the applications of the thermal decomposition approach.
Other research includes thermolysis on defective carbon substrates, thus making hydrogen production possible at temperatures just under 1,000 °C (1,270 K; 1,830 °F). [ 15 ]
One side benefit of a nuclear reactor that produces both electricity and hydrogen is that it can shift production between the two. For instance, a nuclear plant might produce electricity during the day and hydrogen at night, matching its electrical generation profile to the daily variation in demand. If the hydrogen can be produced economically, this scheme would compete favorably with existing grid energy storage schemes. As of 2005, there was sufficient hydrogen demand in the United States that all daily peak generation could be handled by such plants. [ 16 ]
The hybrid thermoelectric copper–chlorine cycle is a cogeneration system using the waste heat from nuclear reactors, specifically the CANDU supercritical water reactor . [ 17 ]
Concentrated solar power can achieve the high temperatures necessary to split water. Hydrosol-2 is a 100-kilowatt pilot plant at the Plataforma Solar de Almería in Spain which uses sunlight to obtain the required 800 to 1,200 °C (1,070 to 1,470 K; 1,470 to 2,190 °F) to split water. Hydrosol II has been in operation since 2008. The design of this 100-kilowatt pilot plant is based on a modular concept. As a result, it may be possible that this technology could be readily scaled up to megawatt range by multiplying the available reactor units and by connecting the plant to heliostat fields (fields of sun-tracking mirrors) of a suitable size. [ 18 ]
Material constraints due to the required high temperatures are reduced by the design of a membrane reactor with simultaneous extraction of hydrogen and oxygen that exploits a defined thermal gradient and the fast diffusion of hydrogen. With concentrated sunlight as heat source and only water in the reaction chamber, the produced gases are very clean with the only possible contaminant being water. A "Solar Water Cracker" with a concentrator of about 100 m 2 can produce almost one kilogram of hydrogen per sunshine hour. [ 19 ]
The sulfur–iodine cycle (S–I cycle) is a series of thermochemical processes used to produce hydrogen . The S–I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen . All other chemicals are recycled. The S–I process requires an efficient source of heat.
More than 352 thermochemical cycles have been described for water splitting by thermolysis . [ 20 ] These cycles promise to produce hydrogen and oxygen from water and heat without using electricity. [ 21 ] Since all the input energy for such processes is heat, they can be more efficient than high-temperature electrolysis. This is because the efficiency of electricity production is inherently limited. Thermochemical production of hydrogen using chemical energy from coal or natural gas is generally not considered, because the direct chemical path is more efficient.
For all the thermochemical processes, the summary reaction is that of the decomposition of water: [ 21 ] 2 H 2 O ⇌ Heat 2 H 2 + O 2 {\displaystyle {\ce {2H2O <=>[{\ce {Heat}}] 2H2{}+ O2}}}
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Water stagnation occurs when water stops flowing for a long period of time. Stagnant water can be a significant environmental hazard . [ 1 ]
Malaria and dengue are among the main dangers of still water, which can become a breeding ground for the mosquitoes that transmit these diseases. [ 2 ]
Stagnant water can be dangerous because it provides a better incubator than running water for many kinds of infectious pathogens . Stagnant water can be contaminated with human and animal feces , particularly in deserts or other areas of low rainfall. [ 2 ] Water stagnation for as little as six days can completely change bacterial community composition and increase cell count. [ 3 ]
Stagnant water may be classified into the following basic, although overlapping, types:
To avoid ground and surface water stagnation, the drainage of surface and subsoil is advised. Areas with a shallow water table are more susceptible to ground water stagnation due to the lower availability of natural soil drainage.
Some plants prefer flowing water, while others, such as lotuses , prefer stagnant water.
Various anaerobic bacteria are commonly found in stagnant water. [ 4 ] For this reason, pools of stagnant water have historically been used in processing hemp and some other fiber crops , as well as linden bark used for making bast shoes . Several weeks of soaking makes bast fibers easily separable due to bacterial and fermentative processes known as retting .
Stagnant water is the favorite breeding ground for a number of insects .
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A water supply network or water supply system is a system of engineered hydrologic and hydraulic components that provide water supply . A water supply system typically includes the following:
Water supply networks are often run by public utilities of the water industry .
Raw water (untreated) is from a surface water source (such as an intake on a lake or a river ) or from a groundwater source (such as a water well drawing from an underground aquifer ) within the watershed that provides the water resource .
The raw water is transferred to the water purification facilities using uncovered aqueducts, covered tunnels or underground water pipes .
Virtually all large systems must treat the water; a fact that is tightly regulated by global, state and federal agencies, such as the World Health Organization (WHO) or the United States Environmental Protection Agency (EPA). Water treatment must occur before the product reaches the consumer and afterwards (when it is discharged again). Water purification usually occurs close to the final delivery points to reduce pumping costs and the chances of the water becoming contaminated after treatment.
Traditional surface water treatment plants generally consists of three steps: clarification, filtration and disinfection. Clarification refers to the separation of particles (dirt, organic matter, etc.) from the water stream. Chemical addition (i.e. alum, ferric chloride) destabilizes the particle charges and prepares them for clarification either by settling or floating out of the water stream. Sand, anthracite or activated carbon filters refine the water stream, removing smaller particulate matter. While other methods of disinfection exist, the preferred method is via chlorine addition. Chlorine effectively kills bacteria and most viruses and maintains a residual to protect the water supply through the supply network.
The product, delivered to the point of consumption, is called potable water if it meets the water quality standards required for human consumption.
The water in the supply network is maintained at positive pressure to ensure that water reaches all parts of the network, that a sufficient flow is available at every take-off point and to ensure that untreated water in the ground cannot enter the network. The water is typically pressurised by pumping the water into storage tanks constructed at the highest local point in the network. One network may have several such service reservoirs .
In small domestic systems, the water may be pressurised by a pressure vessel or even by an underground cistern (the latter however does need additional pressurizing). This eliminates the need of a water tower or any other heightened water reserve to supply the water pressure.
These systems are usually owned and maintained by local governments such as cities or other public entities, but are occasionally operated by a commercial enterprise (see water privatization ). Water supply networks are part of the master planning of communities, counties, and municipalities. Their planning and design requires the expertise of city planners and civil engineers , who must consider many factors, such as location, current demand, future growth, leakage, pressure, pipe size, pressure loss, fire fighting flows, etc.—using pipe network analysis and other tools.
As water passes through the distribution system, the water quality can degrade by chemical reactions and biological processes. Corrosion of metal pipe materials in the distribution system can cause the release of metals into the water with undesirable aesthetic and health effects. Release of iron from unlined iron pipes can result in customer reports of "red water" at the tap. Release of copper from copper pipes can result in customer reports of "blue water" and/or a metallic taste. Release of lead can occur from the solder used to join copper pipe together or from brass fixtures . Copper and lead levels at the consumer's tap are regulated to protect consumer health.
Utilities will often adjust the chemistry of the water before distribution to minimize its corrosiveness. The simplest adjustment involves control of pH and alkalinity to produce a water that tends to passivate corrosion by depositing a layer of calcium carbonate . Corrosion inhibitors are often added to reduce release of metals into the water. Common corrosion inhibitors added to the water are phosphates and silicates .
Maintenance of a biologically safe drinking water is another goal in water distribution. Typically, a chlorine based disinfectant , such as sodium hypochlorite or monochloramine is added to the water as it leaves the treatment plant. Booster stations can be placed within the distribution system to ensure that all areas of the distribution system have adequate sustained levels of disinfection .
Like electric power lines, roads, and microwave radio networks, water systems may have a loop or branch network topology, or a combination of both. The piping networks are circular or rectangular. If any one section of water distribution main fails or needs repair, that section can be isolated without disrupting all users on the network.
Most systems are divided into zones. [ 1 ] Factors determining the extent or size of a zone can include hydraulics, telemetry systems, history, and population density. Sometimes systems are designed for a specific area then are modified to accommodate development. Terrain affects hydraulics and some forms of telemetry. While each zone may operate as a stand-alone system, there is usually some arrangement to interconnect zones in order to manage equipment failures or system failures.
Water supply networks usually represent the majority of assets of a water utility. Systematic documentation of maintenance works using a computerized maintenance management system (CMMS) is a key to a successful operation of a water utility. [ why? ]
A sustainable urban water supply network covers all the activities related to provision of potable water. Sustainable development is of increasing importance for the water supply to urban areas. Incorporating innovative water technologies into water supply systems improves water supply from sustainable perspectives. The development of innovative water technologies provides flexibility to the water supply system, generating a fundamental and effective means of sustainability based on an integrated real options approach. [ 2 ]
Water is an essential natural resource for human existence. It is needed in every industrial and natural process, for example, it is used for oil refining , for liquid-liquid extraction in hydro-metallurgical processes, for cooling, for scrubbing in the iron and the steel industry, and for several operations in food processing facilities.
It is necessary to adopt a new approach to design urban water supply networks; water shortages are expected in the forthcoming decades and environmental regulations for water utilization and waste-water disposal are increasingly stringent.
To achieve a sustainable water supply network, new sources of water are needed to be developed, and to reduce environmental pollution.
The price of water is increasing, so less water must be wasted and actions must be taken to prevent pipeline leakage. Shutting down the supply service to fix leaks is less and less tolerated by consumers. A sustainable water supply network must monitor the freshwater consumption rate and the waste-water generation rate.
Many of the urban water supply networks in developing countries face problems related to population increase , water scarcity , and environmental pollution .
In 1900 just 13% of the global population lived in cities. By 2005, 49% of the global population lived in urban areas. In 2030 it is predicted that this statistic will rise to 60%. [ 3 ] Attempts to expand water supply by governments are costly and often not sufficient. The building of new illegal settlements makes it hard to map, and make connections to, the water supply, and leads to inadequate water management. [ 4 ] In 2002, there were 158 million people with inadequate water supply . [ 5 ] An increasing number of people live in slums , in inadequate sanitary conditions, and are therefore at risk of disease .
Potable water is not well distributed in the world. 1.8 million deaths are attributed to unsafe water supplies every year, according to the WHO . [ 6 ] Many people do not have any access, or do not have access to quality and quantity of potable water, though water itself is abundant. Poor people in developing countries can be close to major rivers, or be in high rainfall areas, yet not have access to potable water at all. There are also people living where lack of water creates millions of deaths every year.
Where the water supply system cannot reach the slums, people manage to use hand pumps , to reach the pit wells, rivers , canals , swamps and any other source of water. In most cases the water quality is unfit for human consumption. The principal cause of water scarcity is the growth in demand. Water is taken from remote areas to satisfy the needs of urban areas. Another reason for water scarcity is climate change : precipitation patterns have changed; rivers have decreased their flow; lakes are drying up; and aquifers are being emptied.
In developing countries many governments are corrupt and poor and they respond to these problems with frequently changing policies and non clear agreements. [ 7 ] Water demand exceeds supply, and household and industrial water supplies are prioritised over other uses, which leads to water stress . [ 8 ] Potable water has a price in the market; water often becomes a business for private companies, which earn a profit by putting a higher price on water, which imposes a barrier for lower-income people. The Millennium Development Goals propose the changes required.
Goal 6 of the United Nations' Sustainable Development Goals is to "Ensure availability and sustainable management of water and sanitation for all". [ 9 ] This is in recognition of the human right to water and sanitation, which was formally acknowledged at the United Nations General Assembly in 2010, that "clean drinking water and sanitation are essential to the recognition of all human rights". [ 10 ] Sustainable water supply includes ensuring availability, accessibility, affordability and quality of water for all individuals.
In advanced economies, the problems are about optimising existing supply networks. These economies have usually had continuing evolution, which allowed them to construct infrastructure to supply water to people. The European Union has developed a set of rules and policies to overcome expected future problems.
There are many international documents with interesting, but not very specific, ideas and therefore they are not put into practice. [ 11 ] Recommendations have been made by the United Nations , such as the Dublin Statement on Water and Sustainable Development .
The yield of a system can be measured by either its value or its net benefit. For a water supply system, the true value or the net benefit is a reliable water supply service having adequate quantity and good quality of the product. For example, if the existing water supply of a city needs to be extended to supply a new municipality , the impact of the new branch of the system must be designed to supply the new needs, while maintaining supply to the old system.
The design of a system is governed by multiple criteria, one being cost. If the benefit is fixed , the least cost design results in maximum benefit. However, the least cost approach normally results in a minimum capacity for a water supply network. A minimum cost model usually searches for the least cost solution (in pipe sizes), while satisfying the hydraulic constraints such as: required output pressures, maximum pipe flow rate and pipe flow velocities. The cost is a function of pipe diameters; therefore the optimization problem consists of finding a minimum cost solution by optimising pipe sizes to provide the minimum acceptable capacity.
However, according to the authors of the paper entitled, “Method for optimizing design and rehabilitation of water distribution systems”, “the least capacity is not a desirable solution to a sustainable water supply network in a long term, due to the uncertainty of the future demand”. [ 12 ] It is preferable to provide extra pipe capacity to cope with unexpected demand growth and with water outages. The problem changes from a single objective optimization problem (minimizing cost), to a multi-objective optimization problem (minimizing cost and maximizing flow capacity).
To solve a multi-objective optimization problem, it is necessary to convert the problem into a single objective optimization problem, by using adjustments, such as a weighted sum of objectives , or an ε-constraint method. The weighted sum approach gives a certain weight to the different objectives, and then factors in all these weights to form a single objective function that can be solved by single factor optimization. This method is not entirely satisfactory, because the weights cannot be correctly chosen, so this approach cannot find the optimal solution for all the original objectives.
The second approach (the constraint method), chooses one of the objective functions as the single objective, and the other objective functions are treated as constraints with a limited value. However, the optimal solution depends on the pre-defined constraint limits.
The multiple objective optimization problems involve computing the tradeoff between the costs and benefits resulting in a set of solutions that can be used for sensitivity analysis and tested in different scenarios. But there is no single optimal solution that will satisfy the global optimality of both objectives. As both objectives are to some extent contradictory, it is not possible to improve one objective without sacrificing the other. It is necessary in some cases use a different approach. (e.g. Pareto Analysis ), and choose the best combination.
Returning to the cost objective function, it cannot violate any of the operational constraints. Generally this cost is dominated by the energy cost for pumping. “The operational constraints include the standards of customer service , such as: the minimum delivered pressure, in addition to the physical constraints such as the maximum and the minimum water levels in storage tanks to prevent overtopping and emptying respectively.” [ 13 ]
In order to optimize the operational performance of the water supply network, at the same time as minimizing the energy costs, it is necessary to predict the consequences of different pump and valve settings on the behavior of the network.
Apart from Linear and Non-linear Programming, there are other methods and approaches to design, to manage and operate a water supply network to achieve sustainability—for instance, the adoption of appropriate technology coupled with effective strategies for operation and maintenance. These strategies must include effective management models, technical support to the householders and industries, sustainable financing mechanisms, and development of reliable supply chains . All these measures must ensure the following: system working lifespan; maintenance cycle; continuity of functioning; down time for repairs; water yield and water quality.
In an unsustainable system there is insufficient maintenance of the water networks, especially in the major pipe lines in urban areas. The system deteriorates and then needs rehabilitation or renewal.
Householders and sewage treatment plants can both make the water supply networks more efficient and sustainable. Major improvements in eco-efficiency are gained through systematic separation of rainfall and wastewater. Membrane technology can be used for recycling wastewater.
The municipal government can develop a “Municipal Water Reuse System” which is a current approach to manage the rainwater. It applies a water reuse scheme for treated wastewater, on a municipal scale, to provide non-potable water for industry, household and municipal uses. This technology consists in separating the urine fraction of sanitary wastewater, and collecting it for recycling its nutrients . [ 14 ] The feces and graywater fraction is collected, together with organic wastes from the households, using a gravity sewer system , continuously flushed with non-potable water. The water is treated anaerobically and the biogas is used for energy production .
One effective way to achieve sustainable water management is to shift emphasis towards decentralized water projects, such as drip irrigation diffusion in India. [ 15 ] This project covers large spatial areas while relying on individual technological adoption decisions, offering scalable solutions that can mitigate water scarcity and enhance agricultural productivity.
Another method that can be utilized is through the promoting of community engagement and resistance against unsustainable water infrastructure projects. Grassroots movements, as observed in anti-dam protests in various countries, play a crucial role in challenging dominant development narratives and advocating for more socially and ecologically just water management practices. [ 15 ]
Municipalities and other forms of local governments should also invest in innovative technologies, such as membrane technology for wastewater recycling, and develop policy frameworks that incentivize eco-efficient practices. Municipal water reuse systems, as demonstrated in implementation, offer promising avenues for integrating wastewater treatment and resource recovery into urban water networks. [ 15 ]
The sustainable water supply system is an integrated system including water intake, water utilization, wastewater discharge and treatment and water environmental protection . It requires reducing freshwater and groundwater usage in all sectors of consumption. Developing sustainable water supply systems is a growing trend, because it serves people's long-term interests. [ 16 ] There are several ways to reuse and recycle the water, in order to achieve long-term sustainability, such as:
Other possible approaches to scoping models for water supply, applicable to any urban area, include the following:
The Dublin Statement on Water and Sustainable Development is a good example of the new trend to overcome water supply problems. This statement, suggested by advanced economies, has come up with some principles that are of great significance to urban water supply. These are:
From these statements, developed in 1992, several policies have been created to give importance to water and to move urban water system management towards sustainable development. The Water Framework Directive by the European Commission is a good example of what has been created there out of former policies.
There is great need for a more sustainable water supply systems. To achieve sustainability several factors must be tackled at the same time: climate change, rising energy cost, and rising populations. All of these factors provoke change and put pressure on management of available water resources. [ 18 ]
An obstacle to transforming conventional water supply systems is the amount of time needed to achieve the transformation. More specifically, transformation must be implemented by municipal legislation bodies, which always need short-term solutions too. [ citation needed ] Another obstacle to achieving sustainability in water supply systems is the insufficient practical experience with the technologies required, and the missing know-how about the organization and the transition process.
Urban water infrastructure faces several challenges that undermine its sustainability and resilience. One critical issue highlighted in recent research is the vulnerability of water networks to climate variability and extreme weather events. Poor seasonal rains, as observed in the case of the Panama Canal's lock and dam infrastructure, exemplify how inadequate water supply can strain water-intensive infrastructure, raising questions about engineering legitimacy and the reliability of water systems. [ 19 ]
Another key challenge is the unequal development associated with large-scale water infrastructure projects such as dams and canals. Such projects, while aimed at promoting economic growth, often actually reproduce social and economic inequalities by displacing rural communities and marginalizing indigenous populations. [ 19 ] This phenomenon of "accumulation by dispossession" further emphasizes the need for more equitable and inclusive approaches to water infrastructure development. [ 19 ]
Possible ways to improve this situation is simulating of the network, implementing pilot projects , learning from the costs involved and the benefits achieved.
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The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater , [ 1 ] which may be fresh, saline, or brackish, depending on the locality. It can also be simply explained as the depth below which the ground is saturated. The portion above the water table is the vadose zone . It may be visualized as the "surface" of the subsurface materials that are saturated with groundwater in a given vicinity. [ 2 ]
In coarse soils, the water table settles at the surface where the water pressure head is equal to the atmospheric pressure (where gauge pressure = 0). In soils where capillary action is strong, the water table is pulled upward, forming a capillary fringe .
The groundwater may be from precipitation or from more distant groundwater flowing into the aquifer. In areas with sufficient precipitation, water infiltrates through pore spaces in the soil, passing through the unsaturated zone. At increasing depths, water fills in more of the pore spaces in the soils, until a zone of saturation is reached. Below the water table, in the zone of saturation, layers of permeable rock that yield groundwater are called aquifers . In less permeable soils, such as tight bedrock formations and historic lakebed deposits, the water table may be more difficult to define.
“Water table” and “ water level ” are not synonymous. If a deeper aquifer has a lower permeable unit that confines the upward flow, then the water level in this aquifer may rise to a level that is greater or less than the elevation of the actual water table. The elevation of the water in this deeper well is dependent upon the pressure in the deeper aquifer and is referred to as the potentiometric surface , not the water table. [ 2 ]
The water table may vary due to seasonal changes such as precipitation and evapotranspiration . In undeveloped regions with permeable soils that receive sufficient amounts of precipitation, the water table typically slopes toward rivers that act to drain the groundwater away and release the pressure in the aquifer. Springs , rivers , lakes and oases occur when the water table reaches the surface. Groundwater entering rivers and lakes accounts for the base-flow water levels in water bodies. [ 3 ]
Within an aquifer, the water table is rarely horizontal, but reflects the surface relief due to the capillary effect ( capillary fringe ) in soils , sediments and other porous media . In the aquifer, groundwater flows from points of higher pressure to points of lower pressure, and the direction of groundwater flow typically has both a horizontal and a vertical component. The slope of the water table is known as the “hydraulic gradient”, which depends on the rate at which water is added to and removed from the aquifer and the permeability of the material. The water table does not always mimic the topography due to variations in the underlying geological structure (e.g., folded, faulted, fractured bedrock).
A perched water table (or perched aquifer) is an aquifer that occurs above the regional water table. This occurs when there is an impermeable layer of rock or sediment ( aquiclude ) or relatively impermeable layer ( aquitard ) above the main water table/aquifer but below the land surface. If a perched aquifer's flow intersects the surface, at a valley wall, for example, the water is discharged as a spring .
On low-lying oceanic islands with porous soil, freshwater tends to collect in lenticular pools on top of the denser seawater intruding from the sides of the islands. Such an island's freshwater lens, and thus the water table, rises and falls with the tides.
In some regions, for example, Great Britain or California , winter precipitation is often higher than summer precipitation and so the groundwater storage is not fully recharged in summer. Consequently, the water table is lower during the summer. This disparity between the level of the winter and summer water table is known as the "zone of intermittent saturation", wherein the water table will fluctuate in response to climatic conditions.
Fossil water is groundwater that has remained in an aquifer for several millennia and occurs mainly in deserts . It is non-renewable by present-day rainfall due to its depth below the surface, and any extraction causes a permanent change in the water table in such regions.
Most crops need a water table at a minimum depth. [ 6 ] For some important food and fiber crops a classification was made [ 7 ] because at shallower depths the crop suffers a yield decline. [ 8 ]
A water table close to the surface affects excavation, drainage, foundations, wells and leach fields (in areas without municipal water and sanitation), and more.
When excavation occurs near enough to the water table to reach its capillary action, groundwater must be removed during construction. This is conspicuous in Berlin , which is built on sandy, marshy ground, and the water table is generally 2 meters below the surface. Pink and blue pipes can often be seen carrying groundwater from construction sites into the Spree river (or canals). [ citation needed ]
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Water testing is a broad description for various procedures used to analyze water quality . Millions of water quality tests are carried out daily to fulfill regulatory requirements and to maintain safety. [ 1 ]
Testing may be performed to evaluate:
Government regulations related to water testing and water quality for some major countries is given below.
The Ministry of Environmental Protection of the People's Republic of China is the nation's environmental protection department charged with the task of protecting China's air, water, and land from pollution and contamination. Directly under the State Council, it is empowered and required by law to implement environmental policies and enforce environmental laws and regulations. Complementing its regulatory role, it funds and organizes research and development. [ 2 ] See Ministry of Environmental Protection of the People's Republic of China .
In late 2009, a survey was carried out by China Ministry of Housing and Urban-Rural Development to assess the water quality of urban supplies in China's cities, which revealed that "at least 1,000" water treatment plants out of more than 4,000 plants surveyed at the county level and above failed to comply with government requirements. The survey results were never formally released to the public, but in 2012, China's Century Weekly published the leaked survey data. In response, Wang Xuening, a health ministry official, released figures derived from a pilot monitoring scheme in 2011 and suggested that 80% of China's urban tap water was up to standard. [ citation needed ]
China's new drinking water standards involve 106 indicators. Of China's 35 major cities, only 40% of cities have the capacity to test for all 106 indicators. The department in charge of local water and the health administration department will enter into a discussion to determine results for more than 60 of the new measures; hence it is not required to test the water using every indicator. The grading of water quality is based on an overall average of 95% to fulfill government requirements. The frequency of water quality inspections at water treatment plants is twice yearly. [ 3 ]
Established in 1964, the Pakistan Council of Research in Water Resources aims to conduct, organize, coordinate and promote research in all aspects of water resources. As a national research organization, it undertakes and promotes applied and basic research in different disciplines of water sector. [ 4 ]
In March 2013, Minister for Science and Technology Mir Changez Khan Jamali notified the National Assembly that groundwater samples collected revealed that only 15-18% samples were deemed safe for drinking both in urban and rural areas in Pakistan. The Ministry has created 24 Water Quality Testing Laboratories across Pakistan, developed and commercialized water quality test kits, water filters, water disinfection tablets and drinking water treatment sachets, conducted training for 2,660 professionals of water supply agencies and surveyed 10,000 water supply schemes out of a grand total of 12,000 schemes. [ 5 ]
The Drinking Water Inspectorate is a section of Department for Environment, Food and Rural Affairs set up to regulate the public water supply companies in England and Wales. [ 6 ] Water testing in England and Wales can be conducted at the environmental health office at the local authority. [ 7 ] See Drinking Water Inspectorate .
The U.S. Department of Homeland Security is a cabinet department of the United States federal government, created in response to the September 11 attacks, and with the primary responsibilities of protecting the United States of America and U.S. territories (including protectorates) from and responding to terrorist attacks, man-made accidents, and natural disasters. See United States Department of Homeland Security . [ citation needed ]
The Homeland Security Presidential Directive 7 designates the Environmental Protection Agency as the sector-specific agency for the water sector's critical infrastructure protection activities. All Environmental Protection Agency activities related to water security are carried out in consultation with the Department of Homeland Security. Possible threats to water quality include contamination with deadly agents, such as cyanide, [ 8 ] and physical attacks like the release of toxic gaseous chemicals. [ 9 ]
The principal U.S. federal laws governing water testing are the Safe Drinking Water Act (SDWA) and the Clean Water Act . The U.S. Environmental Protection Agency (EPA) issues regulations under each law specifying analytical test methods. EPA's annual Regulatory Agenda sets a schedule for specific objectives on improving its oversight of water testing. [ 10 ]
Under the Safe Drinking Water Act, public water systems are required to regularly monitor their treated water for contaminants. Water samples must be analyzed using EPA-approved testing methods, by laboratories that are certified by EPA or a state agency. [ 11 ] [ 12 ]
The 2013 revised total coliform rule and the 1989 total coliform rule are the only microbial drinking water regulations that apply to all public water systems. The revised rule highlights the frequency and timing of microbial testing by water systems based on population served, system type, and source water type. It also places a legal limit on the level for Escherichia coli . Potential health threats must be disclosed to EPA or the appropriate state agency, and public notification is required in some circumstances. [ 13 ]
Methods for measuring acute toxicity usually take between 24 and 96 hours to identify contaminants in water supplies. [ 14 ]
All facilities in the United States that discharge wastewater to surface waters (e.g. rivers, lakes or coastal waters) must obtain a permit under the National Pollutant Discharge Elimination System , a Clean Water Act program administered by EPA and state agencies. The facilities covered include sewage treatment plants, industrial and commercial plants, military bases and other facilities. Most permittees are required to regularly collect wastewater samples and analyze them for compliance with permit requirements, and report the results either to EPA or the state agency. [ 15 ]
Private wells are not regulated by the federal government. [ 16 ] In general, private well owners are responsible for testing their wells. [ 17 ] Some state or local governments regulate well construction and may require well testing. [ 18 ] Generally well testing required by local governments is limited to a handful of contaminants including coliform and E. Coli bacteria and perhaps a few predominant local contaminants such as nitrates or arsenic. EPA publishes test methods for contaminants that it regulates under the SDWA. [ 11 ]
Peer-reviewed test methods have been published by government agencies, [ 19 ] private research organizations [ 20 ] and international standards organizations [ 21 ] for ambient water, wastewater and drinking water. Approved published methods must be used when testing to demonstrate compliance with regulatory requirements. [ 22 ] [ 23 ]
The Energy Policy Act of 2005 created a loophole that exempts companies drilling for natural gas from disclosing the chemicals involved in fracturing operations that would normally be required under federal clean water laws. [ 24 ] The loophole is commonly known as the " Halliburton loophole" because Dick Cheney, the former chief executive officer of Halliburton, was reportedly instrumental in its passage. [ 25 ] Although the Safe Drinking Water Act excludes hydraulic fracturing from the Underground Injection Control regulations, the use of diesel fuel during hydraulic fracturing is still regulated. State oil and gas agencies may issue additional regulations for hydraulic fracturing. States or EPA have the authority under the Clean Water Act to regulate discharge of produced waters from hydraulic fracturing operations. [ 26 ]
In December 2011, federal environment officials scientifically linked underground water pollution with hydraulic fracturing for the first time in central Wyoming. EPA stated that the water supply contained at least 10 compounds known to be used in fracking fluids. The findings in the report contradicted arguments by the drilling industry on the safety of the fracturing process, such as the hydrologic pressure that naturally forces fluids downwards instead of upwards. EPA also commented that the pollution from 33 abandoned oil and gas waste pits were responsible for some degree of minor groundwater pollution in the vicinity. [ 27 ]
In January 2013, the Alaska Oil and Gas Conservation Commission, which is responsible for overseeing oil and gas production in Alaska, proposed new rules for regulating hydraulic fracturing in the state, which contains over two billion barrels of shale oil (second only to the Bakkan) and over 80 trillion cubic feet of natural gas. Companies will be required to conduct water testing at least 90 days prior to and up to 120 days after hydraulically fracturing a well, which includes analysis of pH, alkalinity, total dissolved solids, and total petroleum hydrocarbons. The proposed rules necessitate disclosure of the identity and volume of chemicals used in fracturing fluid. [ 28 ] See Alaska Oil and Gas Conservation Commission .
In February 2013, the state of Illinois introduced the Illinois Hydraulic Fracturing Regulatory Act, H.B. 2615, which imposes strict controls on fracturing companies, such as chemical disclosure requirements and water testing requirements. The bill includes baseline and periodic post-frack testing of potentially affected waters, such as surface water and groundwater sources near fracturing wells, to identify contamination associated with hydraulic fracturing. Fracturing wells will be closed if fracturing fluid is released outside of the shale rock formation being fractured. [ 29 ]
Detectable levels of pharmaceuticals and personal care products, in the parts per trillion, are found in many public drinking water systems in the US as many water testing plants lack the technological know-how to remove these chemical compounds from raw water. There are now increasing worries about how these compounds degrade and react in the environment, during the treatment process, inside our bodies, and the long-term exposure to multiple contaminants at low levels. Out of over 80,000 chemicals registered with the EPA, the US federal drinking water rules mandate testing for only 83 chemicals, which calls for increased monitoring of pharmaceuticals on the presence and concentrations of chemical compounds in rivers, streams, and treated tap water. As traditional waste water regulations and treatment systems target microorganisms and nutrients, there are no federal standards for pharmaceuticals in drinking water or waste water. [ 30 ]
In May 2012, the Environmental Protection Agency released a new list of contaminants, known as the unregulated contaminant monitoring regulation 3 (UCMR3), that will be part of municipal water systems testing starting this year and continuing through 2015. The UCMR3 testing will help municipal water system operators measure the occurrence and exposure of contamination levels that may endanger human health. The State Hygienic Laboratory at the University of Iowa is the only state environmental public health laboratory that has been certified and approved to test for all 28 chemical contaminants on the new list. [ 31 ]
In March 2013, the Environmental Protection Agency developed a new rapid water quality test that provides accurate same day results of contamination levels, which marks a significant improvement from current tests that require at least 24 hours to obtain results. The new test will help authorities determine whether beaches are safe for swimming to keep the public from falling sick and could help prevent beaches from being closed. [ 32 ]
The International Maritime Organization, known as the Inter-Governmental Maritime Consultative Organization until 1982, [ 33 ] was established in Geneva in 1948, [ 34 ] and came into force ten years later, meeting for the first time in 1959. [ citation needed ] See International Maritime Organization .
The International Maritime Organization has been at the forefront of the international community by taking the lead in addressing the transfer of aquatic invasive species through shipping. On 13 February 2004, the International Convention for the Control and Management of Ships' Ballast Water and Sediments was adopted by consensus at a diplomatic conference held at the International Maritime Organization headquarters in London. According to the convention, all ships are required to implement a ballast water and sediments management plan. All ships will have to carry a Ballast Water Record Book and will be required to carry out ballast water management procedures to a given standard. Parties to the convention are given the option to take additional measures which are subject to criteria set out in the Convention and to International Maritime Organization guidelines. Ballast water management is subjected to the ballast water exchange standard and the ballast water performance standard. Ships performing ballast water exchange shall do so with an efficiency of 95 per cent volumetric exchange of ballast water and ships using a ballast water management system (BWMS) shall meet a performance standard based on agreed numbers of organisms per unit of volume. The convention will enter into force 12 months after ratification by 30 States, representing 35 per cent of world merchant shipping tonnage. [ 35 ] See Ballast water discharge and the environment .
The [[World Water Monitoring [ 36 ] Day|EarthEcho Water Challenge]] is an international education and outreach program that generates public awareness and involvement in safeguarding water resources globally by engaging citizens to conduct water testing of local water bodies. Participants learn how to conduct simple water quality tests, analyze common indicators of water health, specifically dissolved oxygen, pH, temperature, and turbidity. The program was originally called "World Water Monitoring Day" and later "World Water Monitoring Challenge", and was established in 2003. EarthEcho International encourages participants to conduct their monitoring activities as part of the "EarthEcho Water Challenge" during any period between March 22 ( World Water Day ) and December of each year. [ 37 ]
As of 2009, the global water test market, which includes in-house, small commercial and large laboratory groups, is approximately US$3.6 billion. The global market for low-end test equipment is roughly $300–400 million. The global market for in-line monitors is approximately $100–130 million. [ 38 ]
Key products include analytical systems, instrumentation, and reagents for water quality and safety analysis. [ 39 ] Reagents are chemical testing compounds that identify presence of chlorine, pH, alkalinity, turbidity and other metrics.
The equipment market comprises low-end, onsite field testing equipment, in-line monitors, and high-end testing laboratory instruments. [ 38 ] High-end lab equipment are Mass Spectrometry devices that conduct organic analysis, using Gas Chromatography and Liquid Chromatography , or metals analysis, using Inductively Coupled Plasma. [ 1 ]
Several trends to monitor include digital sensor plug-and-play techniques and luminescent dissolved oxygen meters replacing sensors. [ 40 ]
The water test market is approximately two-thirds equipment and one-third consumables. Reagents are used with each test and generate recurring revenue for companies. Aftermarket maintenance agreements, operator training and parts replacement help to ensure resources are maximized. [ 40 ] The market leader with an estimated 21% market share, Danaher, is able to reap EBIT [ clarification needed ] margins in the high-teens-to-low-20% on test equipment, but can command 40%+ margins on the water test reagents. [ 41 ] See Freebie marketing .
Companies tend to employ the "direct-to-end-user" model for most products, but may also try to sell low-end equipment via the Internet to reduce distribution costs. [ 40 ]
Pricing depends on application and type of product. Instruments range from as low as $10 to thousands of dollars. [ 40 ]
The low-end test equipment is dominated by few large suppliers, notably Germany's Loviband and Merck, DelAgua & ITS Europe Water Testing of the UK who work globally, and US-based LaMotte. Major manufacturers of in-line equipment include Siemens and Danaher's Hach. Thermo Scientific and Waters are key producers of high-end test equipment. [ 38 ]
The end markets include municipal water plants, industrial users, such as beverage and electronics, and environmental agencies, such as the United States Geological Survey. [ 40 ]
There are two main types of laboratories: commercial and in-house.
In-house laboratories are usually present in municipal water and waste water facilities, breweries and pharmaceutical manufacturing plants. They account for roughly half of all tests run annually. [ 1 ]
Most of the commercial laboratories are single-site firms that only service institutions in the geographical region. The employee head count for each laboratory is usually fewer than five people, and revenues are under $1 million. These laboratories account for one quarter of all tests. There are several major laboratory groups, such as UK-based Inspicio and Australia-based ALS, which account for another quarter of all tests. [ 1 ]
The conventional impression is that private water systems, which sources groundwater from rural areas, produce higher water quality compared to public water systems. Studies have demonstrated that groundwater is vulnerable to antibiotic-resistant bacteria, which necessitates frequent water testing. However, critics like Charrois argue that inconvenience and time constraint impede regular testing in private wells and water systems, which poses risk of poor water quality to consumers. [ 42 ]
In 1998, Sydney, Australia's water supply, 85% controlled by Suez Lyonnaise des Eaux until 2021, [ 43 ] contained high concentrations of parasites Giardia and Cryptosporidium . However, the public was not immediately informed of the water contamination when it had first occurred. [ 44 ]
In Ontario, Canada, the Harris government introduced the "Common Sense Revolution" to cut the large provincial deficit accumulated under the previous Rae government, implementing major cuts to the environment budget, privatizing water testing labs, deregulating water protection infrastructure, and firing trained water testing experts. See Mike Harris .
In 1999, in spite of a Canadian federal government study that found a third of Ontario's rural wells were contaminated with E. coli, the Ontario government dropped testing for E.coli from its Drinking Water Surveillance Program and subsequently closed the program in 2000. In June 2000, there was a wave of E. coli outbreaks in several communities in rural Ontario, where at least seven people died from consuming the water in Walkerton. The private testing company, A&L Laboratories, detected E. coli in the water but failed to disclose the contamination to provincial authorities due to a loophole in the "common sense" regulation. A&L Laboratories claimed that the test results were "confidential intellectual property" and therefore belonged only to the "client", who was the authorities of Walkerton who lacked the training for proper assessment. [ 44 ] See Escherichia coli .
In 2011, Hong Kong Education Secretary Michael Suen was diagnosed with Legionnaires' disease. The bacteria contamination stemmed from Hong Kong's HK$5.5 billion government headquarters site, where traces of the bacteria were found to be up to 14 times above acceptable levels. [ 45 ]
In March 2013, French consumer magazine 60 Millions de Consommateurs and non-governmental organization Fondation France Libertés conducted an investigation that found traces of pesticides and prescription drugs, including a medicine for breast cancer treatment, in almost one in five French brands of bottled water, which are commonly touted as cleaner, healthier and purer alternatives to French tap water. Out of 47 brands of bottled water commonly available in French supermarkets, 10 brands contained "residues from drugs or pesticides". [ 46 ]
In March 2013, almost 200 water fountains in Jersey City public schools were found to contain lead above regulatory standards, where one of the water fountains had lead contamination at levels more than 800 times the EPA's standard. The situation warrants concern because exposure to lead in water could lead to mental retardation for children. [ 47 ]
In March 2013, a defense lawyer asked a federal judge to dismiss charges against the owner of Mississippi Environmental Analytical Laboratories Inc. accused of falsifying records on industrial waste water samples. According to the indictment, Borg Warner Emissions Systems Inc. hired Tennie White, the owner of the laboratory, to test waste water discharge at its car parts plant in Water Valley. White is accused of creating three reports in 2009 that indicated tests were completed when they were not. The motion to dismiss was based on the lawyer's argument that the documents referred to in the indictment were not signed and were not submitted to a government agency. [ 48 ]
Water quality testing for private wells in Chemung County is affected by budget cuts. [ 49 ]
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Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking , industrial water supply, irrigation , river flow maintenance, water recreation or many other uses, including being safely returned to the environment. Water treatment removes contaminants and undesirable components, or reduces their concentration so that the water becomes fit for its desired end-use. This treatment is crucial to human health and allows humans to benefit from both drinking and irrigation use.
Water contamination is primarily caused by the discharge of untreated wastewater from enterprises. The effluent from various enterprises, which contains varying levels of contaminants, is dumped into rivers or other water resources. The wastewater may have a high proportion of organic and inorganic contaminants at the initial discharge. Industries generate wastewater as a result of fabrication processes, processes dealing with paper and pulp , textiles , chemicals , and from various streams such as cooling towers , boilers , and production lines. [ 1 ]
Treatment for drinking water production involves the removal of contaminants and/or inactivation of any potentially harmful microbes from raw water to produce water that is pure enough for human consumption without any short term or long term risk of any adverse health effect. In general terms, the greatest microbial risks are associated with ingestion of water that is contaminated with human or animal (including bird) feces. Feces can be a source of pathogenic bacteria, viruses, protozoa and helminths. The removal or destruction of microbial pathogens is essential, and commonly involves the use of reactive chemical agents such as suspended solids , to remove bacteria , algae , viruses , fungi , and minerals including iron and manganese . Research including Professor Linda Lawton 's group at Robert Gordon University , Aberdeen is working to improve detection of cyanobacteria . [ 2 ] These substances continue to cause great harm to several less developed countries who do not have access to effective water purification systems. [ original research? ]
Measures taken to ensure water quality not only relate to the treatment of the water, but to its conveyance and distribution after treatment. It is therefore common practice to keep residual disinfectants in the treated water to kill bacteriological contamination during distribution and to keep the pipes clean. [ 3 ]
Water supplied to domestic properties such as for tap water or other uses, may be further treated before use, often using an in-line treatment process. Such treatments can include water softening or ion exchange. [ citation needed ]
Wastewater treatment is a process which removes and eliminates contaminants from wastewater . It thus converts it into an effluent that can be returned to the water cycle . Once back in the water cycle, the effluent creates an acceptable impact on the environment. It is also possible to reuse it. This process is called water reclamation . [ 4 ] The treatment process takes place in a wastewater treatment plant. There are several kinds of wastewater which are treated at the appropriate type of wastewater treatment plant. For domestic wastewater the treatment plant is called a Sewage Treatment . Municipal wastewater or sewage are other names for domestic wastewater . For industrial wastewater, treatment takes place in a separate Industrial wastewater treatment , or in a sewage treatment plant. In the latter case it usually follows pre-treatment. Further types of wastewater treatment plants include Agricultural wastewater treatment and leachate treatment plants.
One common process in wastewater treatment is phase separation , such as sedimentation. Biological and chemical processes such as oxidation are another example. Polishing is also an example. The main by-product from wastewater treatment plants is a type of sludge that is usually treated in the same or another wastewater treatment plant. [ 5 ] : Ch.14 Biogas can be another by-product if the process uses anaerobic treatment. Treated wastewater can be reused as reclaimed water . [ 6 ] The main purpose of wastewater treatment is for the treated wastewater to be able to be disposed or reused safely. However, before it is treated, the options for disposal or reuse must be considered so the correct treatment process is used on the wastewater.
Water treatment is used to reduce inpact on equipment used in industrial processes, such as heating, cooling, processing, cleaning, and rinsing so that operating costs and risks are reduced. Poor water treatment lets water interact with the surfaces of pipes and vessels which contain it. Steam boilers can scale up or corrode, and these deposits will mean more fuel is needed to heat the same amount of water. Cooling towers can also scale up and corrode, but left untreated, the warm, dirty water they can contain will encourage bacteria to grow, and Legionnaires' disease can be the fatal consequence. Water treatment is also used to improve the quality of water contacting the manufactured product (e.g., semiconductors) and/or can be part of the product (e.g., beverages, pharmaceuticals). In these instances, poor water treatment can cause defective products. [ citation needed ]
For the elimination of hazardous chemicals from the water, many treatment procedures have been applied. [ 8 ]
The processes involved in removing the contaminants include physical processes such as settling and filtration , chemical processes such as disinfection and coagulation , and biological processes such as slow sand filtration .
A combination selected from the following processes (depending on the season and contaminants and chemicals present in the raw water) is used for municipal drinking water treatment worldwide.
Different chemical procedures for the conversion into final products or the removal of pollutants are used for the safe disposal of contaminants. [ 9 ]
Physical techniques of water/waste water treatment rely on physical phenomena to complete the removal process, rather than biological or chemical changes. [ 9 ]
Most common physical techniques are:
Also referred to as "Conventional" Treatment
Chemical precipitation is a common process used to reduce heavy metals concentrations in wastewater. The dissolved metal ions are transformed to an insoluble phase by a chemical interaction with a precipitant agent such as lime. In industrial applications stronger alkalis may be used to effect complete precipitation. In drinking water treatment, the common-ion effect is often used to help reduce water hardness. [ 14 ]
Flotation uses bubble attachment to separate solids or dispersed liquids from a liquid phase. [ 15 ]
Membrane filtration can remove suspended solids and organic components, and inorganic pollutants such heavy metals. For heavy metal removal, several forms of membrane filtration , such as ultrafiltration , nanofiltration , and reverse osmosis , can be used depending on the particle size that can be maintained. [ 16 ] [ 17 ] Aminophosphonates can be added for antiscalant properties to maintain filtration. [ 18 ]
Ion exchange is a reversible ion exchange process in which an insoluble substance ( resin ) takes ions from an electrolytic solution and releases additional ions of the same charge in a chemically comparable amount without changing the resin's structure. [ 19 ] [ 20 ]
Adsorption is a mass transfer process in which a substance is transported from the liquid phase to the surface of a solid/liquid (adsorbent) and becomes physically and chemically bonded (adsorbate). Adsorption can be classified into two forms based on the type of attraction between the adsorbate and the adsorbent: physical and chemical adsorption, commonly known as physisorption and chemisorptions. [ 21 ] [ 22 ]
Activated carbons (ACs) or biological-activated carbon (BAC) [ 23 ] are effective adsorbents for a wide variety of contaminants. The adsorptive removal of color, aroma, taste, and other harmful organics and inorganics from drinking water and wastewater is one of their industrial applications. [ 24 ]
Both a high surface area and a large pore size can improve the efficiency of activated carbon. Activated carbon was utilized by a number of studies to remove heavy metals and other types of contaminants from wastewater. The cost of activated carbon is rising due to a shortage of commercial activated carbon (AC). Because of its high surface area, porosity, and flexibility, activated carbon has a lot of potential in wastewater treatment. [ 24 ]
This is the method by which dissolved and suspended organic chemical components are eliminated through biodegradation , in which an optimal amount of microorganism is given to re-enact the same natural self-purification process. [ 25 ] Through two distinct biological process , such as biological oxidation and biosynthesis , microorganisms can degrade organic materials in wastewater. Microorganisms involved in wastewater treatment produce end products such as minerals , carbon dioxide , and ammonia during the biological oxidation process. The minerals (products) remained in the wastewater and were discharged with the effluent . Microorganisms use organic materials in wastewater to generate new microbial cells with dense biomass that is eliminated by sedimentation throughout the biosynthesis process. [ 26 ]
Many developed countries specify standards to be applied in their own country. In Europe, this includes the European Drinking Water Directive [ 27 ] and in the United States the United States Environmental Protection Agency (EPA) establishes standards as required by the Safe Drinking Water Act . For countries without a legislative or administrative framework for such standards, the World Health Organization publishes guidelines on the standards that should be achieved. [ 28 ] China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002. [ 29 ]
Where drinking water quality standards do exist, most are expressed as guidelines or targets rather than requirements, and very few water standards have any legal basis or, are subject to enforcement. [ 30 ] Two exceptions are the European Drinking Water Directive and the Safe Drinking Water Act in the United States, which require legal compliance with specific standards.
Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) or self-supply designs. [ 31 ] Such designs may employ solar water disinfection methods, using solar irradiation to inactivate harmful waterborne microorganisms directly, mainly by the UV-A component of the solar spectrum, or indirectly through the presence of an oxide photocatalyst , typically supported TiO 2 in its anatase or rutile phases. [ 32 ] Despite progress in SODIS technology, military surplus water treatment units like the ERDLator are still frequently used in developing countries. Newer military style Reverse Osmosis Water Purification Units (ROWPU) are portable, self-contained water treatment plants are becoming more available for public use. [ 33 ]
For waterborne disease reduction to last, water treatment programs that research and development groups start in developing countries must be sustainable by the citizens of those countries. This can ensure the efficiency of such programs after the departure of the research team, as monitoring is difficult because of the remoteness of many locations.
Energy Consumption: Water treatment plants can be significant consumers of energy. In California, more than 4% of the state's electricity consumption goes towards transporting moderate quality water over long distances, treating that water to a high standard. [ 34 ] In areas with high quality water sources which flow by gravity to the point of consumption, costs will be much lower.
Much of the energy requirements are in pumping. Processes that avoid the need for pumping tend to have overall low energy demands. Those water treatment technologies that have very low energy requirements including trickling filters , slow sand filters , gravity aqueducts .
A 2021 study found that a large-scale water chlorination program in urban areas of Mexico massively reduced childhood diarrheal disease mortality rates. [ 35 ]
Stainless steels, such as Type 304L and 316L, are used extensively in the fabrication of water treatment plants due to their corrosion resistance to water and to the corrosivity of chlorination used for disinfection. [ 36 ] [ 37 ]
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A water tunnel is an experimental facility used for testing the hydrodynamic behavior of submerged bodies in flowing water. It functions similar to a recirculating wind tunnel , but uses water as the working fluid, and related phenomena are investigated, such as measuring the forces on scale models of submarines or lift and drag on hydrofoils . Water tunnels are sometimes used in place of wind tunnels to perform measurements because techniques like particle image velocimetry (PIV) are easier to implement in water. For many cases as long as the Reynolds number is equivalent, the results are valid, whether a submerged water vehicle model is tested in air or an aerial vehicle is tested in water. For low Reynolds number flows, tunnels can use oil instead of water. The advantage is that the increased viscosity will allow the flow to be a higher speed (and thus easier to maintain in a stable manner) for a lower Reynolds number.
Often, a tunnel will be co-located with other experimental facilities such as a wave flume at a Ship model basin .
Because it is a high-speed phenomenon, a special procedure is needed to visualize cavitation. The propeller, attached to a dynamometer , is placed in the inflow, and its thrust and torque is measured at different ratios of propeller speed (number of revolutions) to inflow velocity. A stroboscope synchronized with the propeller speed "freezes" the cavitation bubble. By this means, it is possible to determine if the propeller would be damaged by cavitation. To ensure similarity to the full-scale propeller, the pressure is lowered, and the gas content of the water is controlled.
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Water use in alluvial fans refers to irrigation systems using the water resources in alluvial fans , mainly river floods and groundwater recharged by infiltration of rain or river water, to enhance the production of agricultural crops.
Alluvial fans , also called inland deltas, occur at the foot of mountain ranges and mark the presence of river floods. They contain considerable groundwater reservoirs that are replenished each year by infiltration of the water from the river branches into the usually permeable underground, thus creating rich aquifers .
The mountainous areas usually receive more rainfall than the plains: they form a watershed and provide a source of water. In (semi)arid regions, therefore, alluvial fans are often used for irrigation of agricultural crops. The fans reveal much greenery in the harsh desert -like environment. Irrigation methods in alluvial fans differ according to the hydrological regime of the river, the shape of the fan, and the natural resources available to maintain human life.
The alluvial fans along the river plains near Khuzdar , Baluchistan , are fed by small water catchments in areas of relatively low mountains. The fans are relatively small, steep, and subject to flash floods [ 1 ]
Average annual rainfall in Baluchistan varies between 200 and 400 mm, depending on altitude, and the main part occurs in winter (November to March). Of old, in sloping lands, farmers constructed bunds along the contour lines to capture the surface runoff (Fig. K1). This method of water harvesting (locally called khuskaba ) provided extra water for agricultural crops planted just up-slope of the bund, where the captured water would infiltrate into the soil and provide extra soil moisture to supplement the scarce rainfall.
In alluvial fans, the spate floods provided and additional source of water. The floods, diverted from the watercourses, were retained behind similar bunds employed in the khuskaba system (Fig. K2). The method of flood interception is locally called sailaba ( Rod Kohi elsewhere in Pakistan, generally: spate irrigation ). The system is combined with the tapping of groundwater from the aquifer by means of dug underground galleries, called karez or qanat (Fig. K3). The karezes make permanent agriculture possible (Fig. K3). Although the sailaba -and- qanat systems cover about 20% of the agricultural land, their production is more than 40% of the total.
It is a modern development to sink deep wells in the aquifer of the alluvial fan to exploit the groundwater more effectively than do the traditional karezes . The owners of the wells may be entrepreneurs from elsewhere and the original population runs the risk of losing the karez water when the wells draw the water table down to a deeper depth than that of the karezes so that these fall dry (Fig K4).
The fairly large alluvial fan of Garmsar , east of Tehran , is fed by the Hableh Rud river with an important catchment area in the high Alburz mountain range. The river carries a large amount of water during the rainy season, otherwise the discharge is low. [ 2 ]
The irrigation system for the Garmsar alluvial fan is quite well developed (Fig. G1, below), to the extent that lined canals have been made and a large belt-canal crosses the fan through its middle.
Roughly, the cropped area occupies 30% of the land each season, while 70% is left fallow. The winter crops are mainly wheat and barley, while the summer crops are cotton and melons. However, the planting of the new crops is done before harvesting the previous crops. Thus, there is a period of overlap during which 60% of the land is under crops. The fallow land is continuously rotated throughout the years, so that there exists no permanent fallow land, except along the fringes at the base of the fan where soil salinization occurs.
An estimated average annual water balance is shown in Fig. G2 (below). It is seen that the storage of irrigation losses in the aquifer plays an important role. In the dry season the groundwater is used for irrigation by pumping from deep wells. A cross-section of the groundwater situation is shown in Fig. G3 (below).
The water rights are expressed in sang , a measure of continuous flow of about 10 L/s, but in practice it varies from 10 to more than 15 L/s. The water is delivered to about 100 tertiary units (often a village), within which the water is distributed by 12-day rotations amongst the farmers who each are entitled to receive the authorized sangs for a fixed number of hours during each rotation period. The village communities are, at the same time, water-user associations who take care of the water-distribution within the tertiary unit and they maintain the tertiary canals.
At present, the distribution of surface irrigation water to the villages is determined by the Garmsar Water Authority on the basis of the water rights and verbal agreements and communications with the water users in the absence of a written manual. The authority also maintains the irrigation canals and structures. The structures are sometimes re-designed to adjust them to verbally communicated needs. The fair distribution of the irrigation water is not an easy job as the average annual river discharge is quite variable in the range of 5 to 20 m3/s (see graph at the right).
The deep tube-wells are privately owned. The drilling of wells is subject to license . Recently, the licensing has stopped for fear of over-exploitation of the aquifer. It appears that no operational rules are applied to the wells.
In the fringe lands, the water table is shallow because the discharge capacity of the aquifer diminishes here for two reasons: (1) the hydraulic gradient reduces where the sloping alluvial fan reaches the flat desert area, and (2) the thickness and hydraulic conductivity of the aquifer diminishes. The necessary drainage canals for watertable control at the fringes of the irrigation perimeter are not maintained by the water authority, but by the respective farmers groups. For the irrigation water, these groups depend (1) on occasional river floods too large to be handled by the irrigation system and that flow down to the fringe lands through the natural watercourses, (2) on spillage from the irrigation system, and (3) on deep wells.
To stabilize the agriculture in the fringe lands, which are threatened by soil salinization , a method of strip-cropping (Fig. G4) can be recommended for soil salinity control . This method uses irrigated strips next to permanently un-irrigated strips, whereby the salinization is directed to the un-irrigated strips. This concept is sometimes called sacrificial drainage .
The alluvial fan of Punata in the Valle Alto , east of Cochabamba , is fed by the Rio Paracaya river with a higher average discharge than the Hableh Rud, and consequently is fairly flat. [ 3 ]
The alluvial fan of Punata is found in the district of Cochabamba , Bolivia .
The region of Punata, at the upper end of the Valle (valley) Alto, at about 2800 m altitude, has a summer rainfall of 400 to 450 mm starting in the second half of November end ending in March. Maize is here the most important food crop, followed by potatoes . Alfalfa is the dominant fodder crop, followed by maize straw. (Fig. P1). These crops could, of old, only be planted successfully because of the existence of additional water resources like runoff , floods, river base-flow and groundwater . In the winter months, crop growth is restricted due to the occurrence of night frosts, especially in June and July, and absence of rains.
The total rural population in Punata is estimated at 25 000. There are about 4000 families of which an estimated 3680 are farmer families. The farms are small. The average size is 1.3 ha of which 1 ha is cropped. The modal size of farm is smaller, about 0.7 ha.
The rainfall distribution in Punata is characterized by a wet season from December to March, a dry season from May to October, and transition months in April and November. The average yearly total is 428 mm (1966 to 1983, San Benito). The rainfall with a probability of exceedance of 75% (R75) on a year basis is 360 mm. Rainfall is not reliable: in the period from 1966 to 1983, the yearly total varied between 246 mm (1982/83) to 591 mm (1968/69).
The river floods during the rainy summer period can be used for irrigation by anyone who wants to. When the river flow recedes, the stream can only be used for rotational irrigation by those who are entitled to take part in it (this is locally called the mita system). By the month of May the river base-flow becomes strongly reduced, and a drought period sets in, lasting into November.
Irrigation is considered desirable to start the cropping season in August/September, so that an early harvest can be obtained. The early harvest has a high market value and reduces peak labor requirements. Further, the irrigation reduces the risk of crop failure and it permits diversification of agricultural produce. Nevertheless, there are some farming communities that have refrained in the past from the extra effort to obtain additional irrigation water and who seemed to be content with purely rain-fed cropping.
At a modest scale, irrigation from deep-wells is also practiced.
In order to satisfy the needs of the majority of the farmers who strongly wish to have additional irrigation water, the irrigation project Punata-Tiraque began to be developed from 1970 onwards. The project entailed the construction of a complicated system of dams and reservoirs up in the Andean mountains (Fig. P2).
The gross area of the Punata projects is estimated at 4600 ha, 90% of which can be used for agriculture or animal husbandry. About 1150 ha of this presently receive irrigation water, either surface water derived from the Laguna Robada or Lluska Kocha dam, or water pumped from the 16 deep wells in the project area (estimated at 350 ha). In addition there are a few hundred hectares that receive occasional water from mita irrigation (wild flooding).
The traditional irrigation method is based on handling large irrigation flows ( golpes ) per farm at large intervals. The intake structures in the Pucara Mayu river, at the place where it enters the alluvial fan of Punata, would alternately pass water from each of the reservoir systems ( Laguna Robada and Lluska Kocha / Muyu Loma ) and the natural mita water. The new system has been designed for smaller flows with shorter rotation intervals, but it works continuously for the whole area, so that there is no need anymore to separate the various sources of water. It covers a much larger area than the traditional system and it incorporates the associations of the mita systems (which may have partly the same members), the associations of tube-well systems (which may also have partly the same members) as well as the persons who had no previous water rights.
Hence, the new irrigation system makes it necessary to replace the traditional water rights by a totally new set of rights (and duties). In addition, the farmers will have to get used to new water distribution methods and new field irrigation techniques. Because the new irrigation zones do not correspond to the boundaries of the existing, scattered, Comité’s de Riego (Fig. P3), not only the water management but also the organizational structure will have to be adjusted to the new situation.
The Okavango inland delta, near Maun , receives an enormous amount of river inflow from Angola . Hence, the fan is so large and flat that it is rather called a delta. It takes six months for the peak inflow at the apex to reach the base of the delta. [ 4 ]
The inland Okavango Delta in northwest Botswana is hand-shaped, with the fingers spread (see map). The Okavango River, which originates in Angola, enters the delta at its apex. On the average, the river carries about 10 000 million m 3 of water a year into the delta. The flow rate is high in the months of March and April (about 1000 m 3 /s on the average), but varying from year to year between 500 and 1500 m 3 /s and low in November (100 to 200 m 3 /s).
The large volume of water spreading over the delta is almost fully absorbed in permanent and seasonal swamps (the latter are called molapo’s ) before is slowly infiltrates or evaporates. There is rich swamp vegetation, which creates an ideal environment for numerous kinds of animals. The rich fauna finds its habitat on and between the thousands of islands between the swamps.
The little water that exceeds the retention capacity of the marshy wilderness drains from July to November through the fingers of the giant hand. Hence, it takes almost six months before the peak discharge of the Okavango River manifests itself at the base of the delta. Here, the water meets a barrier: the Thamalakane Fault Line (see map), beyond which the Kalahari sands rise up 10 m. At the foot of the fault, the Thamalakane River collects the water (which is not more than 5% of the total inflow) and carries it almost without gradient to the Boteti River, which flows through a breach in the fault line. Eventually, the remaining waters evaporate in the Makgadikgadi Pans , more than 200 km to the east.
Although the annual rainfall is relatively low (an average of 500 mm, the greater part of which falls from December to March), it contributes a volume of water to the Delta equaling half of the Okavango inflow. The annual rainfall and its yearly distribution are equally erratic as the regime of the river.
The Okavango River transports a large amount of sands and other sediments into the delta. Their mass is about 2 million tons a year. Salts also enter the Delta, but they do so in a dissolved form. The salt concentration of the water is some 200 mg/L, which is very low. The total weight of incoming salts is thus about 2 million tons per year.
The sediments and the salts imported by the Okavango River settle in the delta. Together with the vegetation the sediments build up resistances to surface-water flow. As a result, the main watercourses have in the past swayed from thumb to little finger to and fro, as is common in alluvial fans. Tectonic movements have also contributed to this phenomenon. At present the middle finger, from which the Boro River stems, provides the major thoroughfare.
Many of the islands in the delta have a garland of riparian trees along their borders, but in the middle they are bare: symptoms of salt accumulation (see photo of the delta).
The Kalahari Desert cooperates with the Okavango River to form the predominantly sandy soils of the delta. The desert uses the vector wind to deposit its share of fine sand.
The geophysical characteristics of the Okavango Delta have led to a low population density, so that the natural situation has scarcely been disrupted by mankind. Also, the population was more interested in hunting and cattle breeding than in food crop production, so that agricultural developments were limited.
The arable lands in the south-eastern fringes of the delta, that become dry after the floods recede (these are locally known as molapo's ), often have a sandy topsoil. In depressions, the topsoil may be thin or missing altogether, exposing a heavy clay soil.
In 1978/79, after four years of high and prolonged floods had made molapo farming impossible, a severe drought coincided with an outbreak of foot and mouth disease , leaving the local population in a state of emergency. This resulted in two important undertakings:
The Molapo Development Projects (MDP) became operational in December 1983. The project aimed at increasing crop production in pilot areas by protecting those areas against prolonged high floods by flood-control bunds with entrance gates that could be closed (see photo). When enough floodwater has entered the molapo, the gate can be closed and the water recedes under influence of evaporation and infiltration into the soil and cropping may start when the outside water level is still high. This was a response to the high and prolonged flooding in the years 1974–1978, when molapo cropping was largely impossible. In more recent years, however, inadequate floods appeared to present an equally severe constraint to satisfactory crop production. It was therefore decided to focus also on improved, more stable crop production under fully rain-dependent conditions.
The hydrograph figure shows that crop production has not been possible in 60% of the hitherto recorded years because of the prolonged high floods. The figure also shows how flood-control measures can bring about a timely recession of the water level in the molapo. After the flood has been permitted to enter the bunded molapo, the sluice gates are closed. Recession of the water in the bunded molapo then begins under the influence of evaporation and infiltration, and allows a timely planting of the crop (in October or November). The crops use the residual soil moisture (about 100 mm) till the onset of the rainy season at the end of November or the beginning of December. Thus the growing season is prolonged, the moisture availability is increased, and crop production is enhanced. However, the success of the flood-control measures on the crop performance still depends to a great extent on the amount and distribution of the rainfall.
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https://en.wikipedia.org/wiki/Water_use_in_alluvial_fans
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Water vapor , water vapour or aqueous vapor is the gaseous phase of water . It is one state of water within the hydrosphere . Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice . Water vapor is transparent, like most constituents of the atmosphere. [ 1 ] Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation . It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds and fog.
Being a component of Earth's hydrosphere and hydrologic cycle, it is particularly abundant in Earth's atmosphere , where it acts as a greenhouse gas and warming feedback, contributing more to total greenhouse effect than non-condensable gases such as carbon dioxide and methane . Use of water vapor, as steam , has been important for cooking, and as a major component in energy production and transport systems since the industrial revolution .
Water vapor is a relatively common atmospheric constituent, present even in the solar atmosphere as well as every planet in the Solar System and many astronomical objects including natural satellites , comets and even large asteroids . Likewise the detection of extrasolar water vapor would indicate a similar distribution in other planetary systems. Water vapor can also be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects.
Water vapor, which reacts to temperature changes, is referred to as a 'feedback', because it amplifies the effect of forces that initially cause the warming. Therefore, it is a greenhouse gas. [ 2 ]
Whenever a water molecule leaves a surface and diffuses into a surrounding gas, it is said to have evaporated . Each individual water molecule which transitions between a more associated (liquid) and a less associated (vapor/gas) state does so through the absorption or release of kinetic energy . The aggregate measurement of this kinetic energy transfer is defined as thermal energy and occurs only when there is differential in the temperature of the water molecules. Liquid water that becomes water vapor takes a parcel of heat with it, in a process called evaporative cooling . [ 3 ] The amount of water vapor in the air determines how frequently molecules will return to the surface. When a net evaporation occurs, the body of water will undergo a net cooling directly related to the loss of water.
In the US, the National Weather Service measures the actual rate of evaporation from a standardized "pan" open water surface outdoors, at various locations nationwide. Others do likewise around the world. The US data is collected and compiled into an annual evaporation map. [ 4 ] The measurements range from under 30 to over 120 inches per year. Formulas can be used for calculating the rate of evaporation from a water surface such as a swimming pool. [ 5 ] [ 6 ] In some countries, the evaporation rate far exceeds the precipitation rate.
Evaporative cooling is restricted by atmospheric conditions . Humidity is the amount of water vapor in the air. The vapor content of air is measured with devices known as hygrometers . The measurements are usually expressed as specific humidity or percent relative humidity . The temperatures of the atmosphere and the water surface determine the equilibrium vapor pressure; 100% relative humidity occurs when the partial pressure of water vapor is equal to the equilibrium vapor pressure. This condition is often referred to as complete saturation. Humidity ranges from 0 grams per cubic metre in dry air to 30 grams per cubic metre (0.03 ounce per cubic foot) when the vapor is saturated at 30 °C. [ 7 ]
Sublimation is the process by which water molecules directly leave the surface of ice without first becoming liquid water. Sublimation accounts for the slow mid-winter disappearance of ice and snow at temperatures too low to cause melting. Antarctica shows this effect to a unique degree because it is by far the continent with the lowest rate of precipitation on Earth. [ 8 ] As a result, there are large areas where millennial layers of snow have sublimed, leaving behind whatever non-volatile materials they had contained. This is extremely valuable to certain scientific disciplines, a dramatic example being the collection of meteorites that are left exposed in unparalleled numbers and excellent states of preservation.
Sublimation is important in the preparation of certain classes of biological specimens for scanning electron microscopy . Typically the specimens are prepared by cryofixation and freeze-fracture , after which the broken surface is freeze-etched, being eroded by exposure to vacuum until it shows the required level of detail. This technique can display protein molecules, organelle structures and lipid bilayers with very low degrees of distortion.
Water vapor will only condense onto another surface when that surface is cooler than the dew point temperature, or when the water vapor equilibrium in air has been exceeded. When water vapor condenses onto a surface, a net warming occurs on that surface. [ 9 ] The water molecule brings heat energy with it. In turn, the temperature of the atmosphere drops slightly. [ 10 ] In the atmosphere, condensation produces clouds, fog and precipitation (usually only when facilitated by cloud condensation nuclei ). The dew point of an air parcel is the temperature to which it must cool before water vapor in the air begins to condense. Condensation in the atmosphere forms cloud droplets.
Also, a net condensation of water vapor occurs on surfaces when the temperature of the surface is at or below the dew point temperature of the atmosphere. Deposition is a phase transition separate from condensation which leads to the direct formation of ice from water vapor. Frost and snow are examples of deposition.
There are several mechanisms of cooling by which condensation occurs:
1) Direct loss of heat by conduction or radiation.
2) Cooling from the drop in air pressure which occurs with uplift of air, also known as adiabatic cooling .
Air can be lifted by mountains, which deflect the air upward, by convection, and by cold and warm fronts.
3) Advective cooling - cooling due to horizontal movement of air.
A number of chemical reactions have water as a product. If the reactions take place at temperatures higher than the dew point of the surrounding air the water will be formed as vapor and increase the local humidity, if below the dew point local condensation will occur. Typical reactions that result in water formation are the burning of hydrogen or hydrocarbons in air or other oxygen containing gas mixtures, or as a result of reactions with oxidizers.
In a similar fashion other chemical or physical reactions can take place in the presence of water vapor resulting in new chemicals forming such as rust on iron or steel, polymerization occurring (certain polyurethane foams and cyanoacrylate glues cure with exposure to atmospheric humidity) or forms changing such as where anhydrous chemicals may absorb enough vapor to form a crystalline structure or alter an existing one, sometimes resulting in characteristic color changes that can be used for measurement .
Measuring the quantity of water vapor in a medium can be done directly or remotely with varying degrees of accuracy. Remote methods such electromagnetic absorption are possible from satellites above planetary atmospheres. Direct methods may use electronic transducers, moistened thermometers or hygroscopic materials measuring changes in physical properties or dimensions.
Water vapor is lighter or less dense than dry air . [ 11 ] [ 12 ] At equivalent temperatures it is buoyant with respect to dry air, whereby the density of dry air at standard temperature and pressure (273.15 K, 101.325 kPa) is 1.27 g/L and water vapor at standard temperature has a vapor pressure of 0.6 kPa and the much lower density of 0.0048 g/L.
Water vapor and dry air density calculations at 0 °C:
At the same temperature, a column of dry air will be denser or heavier than a column of air containing any water vapor, the molar mass of diatomic nitrogen and diatomic oxygen both being greater than the molar mass of water. Thus, any volume of dry air will sink if placed in a larger volume of moist air. Also, a volume of moist air will rise or be buoyant if placed in a larger region of dry air. As the temperature rises the proportion of water vapor in the air increases, and its buoyancy will increase. The increase in buoyancy can have a significant atmospheric impact, giving rise to powerful, moisture rich, upward air currents when the air temperature and sea temperature reaches 25 °C or above. This phenomenon provides a significant driving force for cyclonic and anticyclonic weather systems (typhoons and hurricanes).
Water vapor is a by-product of respiration in plants and animals. Its contribution to the pressure, increases as its concentration increases. Its partial pressure contribution to air pressure increases, lowering the partial pressure contribution of the other atmospheric gases (Dalton's Law) . The total air pressure must remain constant. The presence of water vapor in the air naturally dilutes or displaces the other air components as its concentration increases.
This can have an effect on respiration. In very warm air (35 °C) the proportion of water vapor is large enough to give rise to the stuffiness that can be experienced in humid jungle conditions or in poorly ventilated buildings.
Water vapor has lower density than that of air and is therefore buoyant in air but has lower vapor pressure than that of air. When water vapor is used as a lifting gas by a thermal airship the water vapor is heated to form steam so that its vapor pressure is greater than the surrounding air pressure in order to maintain the shape of a theoretical "steam balloon", which yields approximately 60% the lift of helium and twice that of hot air. [ 13 ]
The amount of water vapor in an atmosphere is constrained by the restrictions of partial pressures and temperature. Dew point temperature and relative humidity act as guidelines for the process of water vapor in the water cycle . Energy input, such as sunlight, can trigger more evaporation on an ocean surface or more sublimation on a chunk of ice on top of a mountain. The balance between condensation and evaporation gives the quantity called vapor partial pressure .
The maximum partial pressure ( saturation pressure ) of water vapor in air varies with temperature of the air and water vapor mixture. A variety of empirical formulas exist for this quantity; the most used reference formula is the Goff-Gratch equation for the SVP over liquid water below zero degrees Celsius:
where T , temperature of the moist air, is given in units of kelvin , and p is given in units of millibars ( hectopascals ).
The formula is valid from about −50 to 102 °C; however there are a very limited number of measurements of the vapor pressure of water over supercooled liquid water. There are a number of other formulae which can be used. [ 14 ]
Under certain conditions, such as when the boiling temperature of water is reached, a net evaporation will always occur during standard atmospheric conditions regardless of the percent of relative humidity. This immediate process will dispel massive amounts of water vapor into a cooler atmosphere.
Exhaled air is almost fully at equilibrium with water vapor at the body temperature. In the cold air the exhaled vapor quickly condenses, thus showing up as a fog or mist of water droplets and as condensation or frost on surfaces. Forcibly condensing these water droplets from exhaled breath is the basis of exhaled breath condensate , an evolving medical diagnostic test.
Controlling water vapor in air is a key concern in the heating, ventilating, and air-conditioning (HVAC) industry. Thermal comfort depends on the moist air conditions. Non-human comfort situations are called refrigeration , and also are affected by water vapor. For example, many food stores, like supermarkets, utilize open chiller cabinets, or food cases , which can significantly lower the water vapor pressure (lowering humidity). This practice delivers several benefits as well as problems.
Gaseous water represents a small but environmentally significant constituent of the atmosphere . The percentage of water vapor in surface air varies from 0.01% at -42 °C (-44 °F) [ 15 ] to 4.24% when the dew point is 30 °C (86 °F). [ 16 ] Over 99% of atmospheric water is in the form of vapour, rather than liquid water or ice, [ 17 ] and approximately 99.13% of the water vapour is contained in the troposphere . The condensation of water vapor to the liquid or ice phase is responsible for clouds , rain, snow, and other precipitation , all of which count among the most significant elements of what we experience as weather. Less obviously, the latent heat of vaporization , which is released to the atmosphere whenever condensation occurs, is one of the most important terms in the atmospheric energy budget on both local and global scales. For example, latent heat release in atmospheric convection is directly responsible for powering destructive storms such as tropical cyclones and severe thunderstorms . Water vapor is an important greenhouse gas [ 18 ] [ 19 ] owing to the presence of the hydroxyl bond which strongly absorbs in the infra-red .
Water vapor is the "working medium" of the atmospheric thermodynamic engine which transforms heat energy from sun irradiation into mechanical energy in the form of winds. Transforming thermal energy into mechanical energy requires an upper and a lower temperature level, as well as a working medium which shuttles forth and back between both. The upper temperature level is given by the soil or water surface of the Earth, which absorbs the incoming sun radiation and warms up, evaporating water. The moist and warm air at the ground is lighter than its surroundings and rises up to the upper limit of the troposphere. There the water molecules radiate their thermal energy into outer space, cooling down the surrounding air. The upper atmosphere constitutes the lower temperature level of the atmospheric thermodynamic engine. The water vapor in the now cold air condenses out and falls down to the ground in the form of rain or snow. The now heavier cold and dry air sinks down to ground as well; the atmospheric thermodynamic engine thus establishes a vertical convection, which transports heat from the ground into the upper atmosphere, where the water molecules can radiate it to outer space. Due to the Earth's rotation and the resulting Coriolis forces, this vertical atmospheric convection is also converted into a horizontal convection, in the form of cyclones and anticyclones, which transport the water evaporated over the oceans into the interior of the continents, enabling vegetation to grow. [ 20 ]
Water in Earth's atmosphere is not merely below its boiling point (100 °C), but at altitude it goes below its freezing point (0 °C), due to water's highly polar attraction . When combined with its quantity, water vapor then has a relevant dew point and frost point , unlike e. g., carbon dioxide and methane. Water vapor thus has a scale height a fraction of that of the bulk atmosphere, [ 21 ] [ 22 ] [ 23 ] as the water condenses and exits , primarily in the troposphere , the lowest layer of the atmosphere. [ 24 ] Carbon dioxide ( CO 2 ) and methane , being well-mixed in the atmosphere, tend to rise above water vapour. The absorption and emission of both compounds contribute to Earth's emission to space, and thus the planetary greenhouse effect . [ 22 ] [ 25 ] [ 26 ] This greenhouse forcing is directly observable, via distinct spectral features versus water vapor, and observed to be rising with rising CO 2 levels. [ 27 ] Conversely, adding water vapor at high altitudes has a disproportionate impact, which is why jet traffic [ 28 ] [ 29 ] [ 30 ] has a disproportionately high warming effect. Oxidation of methane is also a major source of water vapour in the stratosphere, [ 31 ] and adds about 15% to methane's global warming effect. [ 32 ]
In the absence of other greenhouse gases, Earth's water vapor would condense to the surface; [ 33 ] [ 34 ] [ 35 ] this has likely happened , possibly more than once. Scientists thus distinguish between non-condensable (driving) and condensable (driven) greenhouse gases, i.e., the above water vapor feedback. [ 36 ] [ 19 ] [ 18 ]
Fog and clouds form through condensation around cloud condensation nuclei . In the absence of nuclei, condensation will only occur at much lower temperatures. Under persistent condensation or deposition, cloud droplets or snowflakes form, which precipitate when they reach a critical mass.
Atmospheric concentration of water vapour is highly variable between locations and times, from 10 ppmv in the coldest air to 5% (50 000 ppmv) in humid tropical air, [ 37 ] and can be measured with a combination of land observations, weather balloons and satellites. [ 38 ] The water content of the atmosphere as a whole is constantly depleted by precipitation. At the same time it is constantly replenished by evaporation, most prominently from oceans, lakes, rivers, and moist earth. Other sources of atmospheric water include combustion, respiration, volcanic eruptions, the transpiration of plants, and various other biological and geological processes. At any given time there is about 1.29 x 10 16 litres (3.4 x 10 15 gal.) of water in the atmosphere. The atmosphere holds 1 part in 2500 of the fresh water, and 1 part in 100,000 of the total water on Earth. [ 39 ] The mean global content of water vapor in the atmosphere is roughly sufficient to cover the surface of the planet with a layer of liquid water about 25 mm deep. [ 40 ] [ 41 ] [ 42 ] The mean annual precipitation for the planet is about 1 metre, a comparison which implies a rapid turnover of water in the air – on average, the residence time of a water molecule in the troposphere is about 9 to 10 days. [ 42 ]
Global mean water vapour is about 0.25% of the atmosphere by mass and also varies seasonally, in terms of contribution to atmospheric pressure between 2.62 hPa in July and 2.33 hPa in December. [ 45 ] IPCC AR6 expresses medium confidence in increase of total water vapour at about 1-2% per decade; [ 46 ] it is expected to increase by around 7% per °C of warming. [ 40 ]
Episodes of surface geothermal activity, such as volcanic eruptions and geysers, release variable amounts of water vapor into the atmosphere. Such eruptions may be large in human terms, and major explosive eruptions may inject exceptionally large masses of water exceptionally high into the atmosphere, but as a percentage of total atmospheric water, the role of such processes is trivial. The relative concentrations of the various gases emitted by volcanoes varies considerably according to the site and according to the particular event at any one site. However, water vapor is consistently the commonest volcanic gas ; as a rule, it comprises more than 60% of total emissions during a subaerial eruption . [ 47 ]
Atmospheric water vapor content is expressed using various measures. These include vapor pressure, specific humidity , mixing ratio, dew point temperature, and relative humidity .
Because water molecules absorb microwaves and other radio wave frequencies, water in the atmosphere attenuates radar signals. [ 48 ] In addition, atmospheric water will reflect and refract signals to an extent that depends on whether it is vapor, liquid or solid.
Generally, radar signals lose strength progressively the farther they travel through the troposphere. Different frequencies attenuate at different rates, such that some components of air are opaque to some frequencies and transparent to others. Radio waves used for broadcasting and other communication experience the same effect.
Water vapor reflects radar to a lesser extent than do water's other two phases. In the form of drops and ice crystals, water acts as a prism, which it does not do as an individual molecule ; however, the existence of water vapor in the atmosphere causes the atmosphere to act as a giant prism. [ 49 ]
A comparison of GOES-12 satellite images shows the distribution of atmospheric water vapor relative to the oceans, clouds and continents of the Earth. Vapor surrounds the planet but is unevenly distributed. The image loop on the right shows monthly average of water vapor content with the units are given in centimeters, which is the precipitable water or equivalent amount of water that could be produced if all the water vapor in the column were to condense. The lowest amounts of water vapor (0 centimeters) appear in yellow, and the highest amounts (6 centimeters) appear in dark blue. Areas of missing data appear in shades of gray. The maps are based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's Aqua satellite. The most noticeable pattern in the time series is the influence of seasonal temperature changes and incoming sunlight on water vapor. In the tropics, a band of extremely humid air wobbles north and south of the equator as the seasons change. This band of humidity is part of the Intertropical Convergence Zone , where the easterly trade winds from each hemisphere converge and produce near-daily thunderstorms and clouds. Farther from the equator, water vapor concentrations are high in the hemisphere experiencing summer and low in the one experiencing winter. Another pattern that shows up in the time series is that water vapor amounts over land areas decrease more in winter months than adjacent ocean areas do. This is largely because air temperatures over land drop more in the winter than temperatures over the ocean. Water vapor condenses more rapidly in colder air. [ 50 ]
As water vapor absorbs light in the visible spectral range, its absorption can be used in spectroscopic applications (such as DOAS ) to determine the amount of water vapor in the atmosphere. This is done operationally, e.g. from the Global Ozone Monitoring Experiment (GOME) spectrometers on ERS (GOME) and MetOp (GOME-2). [ 51 ] The weaker water vapor absorption lines in the blue spectral range and further into the UV up to its dissociation limit around 243 nm are mostly based on quantum mechanical calculations [ 52 ] and are only partly confirmed by experiments. [ 53 ]
Water vapor plays a key role in lightning production in the atmosphere. From cloud physics , usually clouds are the real generators of static charge as found in Earth's atmosphere. The ability of clouds to hold massive amounts of electrical energy is directly related to the amount of water vapor present in the local system.
The amount of water vapor directly controls the permittivity of the air. During times of low humidity, static discharge is quick and easy. During times of higher humidity, fewer static discharges occur. Permittivity and capacitance work hand in hand to produce the megawatt outputs of lightning. [ 54 ]
After a cloud, for instance, has started its way to becoming a lightning generator, atmospheric water vapor acts as a substance (or insulator ) that decreases the ability of the cloud to discharge its electrical energy. Over a certain amount of time, if the cloud continues to generate and store more static electricity , the barrier that was created by the atmospheric water vapor will ultimately break down from the stored electrical potential energy. [ 55 ] This energy will be released to a local oppositely charged region, in the form of lightning. The strength of each discharge is directly related to the atmospheric permittivity, capacitance, and the source's charge generating ability. [ 56 ]
Water vapor is common in the Solar System and by extension, other planetary systems . Its signature has been detected in the atmospheres of the Sun, occurring in sunspots . The presence of water vapor has been detected in the atmospheres of all seven extraterrestrial planets in the Solar System, the Earth's Moon, [ 57 ] and the moons of other planets, [ which? ] although typically in only trace amounts.
Geological formations such as cryogeysers are thought to exist on the surface of several icy moons ejecting water vapor due to tidal heating and may indicate the presence of substantial quantities of subsurface water. Plumes of water vapor have been detected on Jupiter's moon Europa and are similar to plumes of water vapor detected on Saturn's moon Enceladus . [ 58 ] Traces of water vapor have also been detected in the stratosphere of Titan . [ 60 ] Water vapor has been found to be a major constituent of the atmosphere of dwarf planet , Ceres , largest object in the asteroid belt [ 61 ] The detection was made by using the far-infrared abilities of the Herschel Space Observatory . [ 62 ] The finding is unexpected because comets , not asteroids , are typically considered to "sprout jets and plumes." According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids." [ 62 ] Scientists studying Mars hypothesize that if water moves about the planet, it does so as vapor. [ 63 ]
The brilliance of comet tails comes largely from water vapor. On approach to the Sun , the ice many comets carry sublimes to vapor. Knowing a comet's distance from the sun, astronomers may deduce the comet's water content from its brilliance. [ 64 ]
Water vapor has also been confirmed outside the Solar System. Spectroscopic analysis of HD 209458 b , an extrasolar planet in the constellation Pegasus, provides the first evidence of atmospheric water vapor beyond the Solar System. A star called CW Leonis was found to have a ring of vast quantities of water vapor circling the aging, massive star . A NASA satellite designed to study chemicals in interstellar gas clouds, made the discovery with an onboard spectrometer. Most likely, "the water vapor was vaporized from the surfaces of orbiting comets." [ 65 ] Other exoplanets with evidence of water vapor include HAT-P-11b and K2-18b . [ 66 ] [ 67 ]
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https://en.wikipedia.org/wiki/Water_vapor
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A water year (also called hydrological year , discharge year or flow year ) is a term commonly used in hydrology to describe a time period of 12 months for which precipitation totals are measured. Its beginning differs from the calendar year because part of the precipitation that falls in late autumn and winter accumulates as snow and does not drain until the following spring or summer's snowmelt . The goal is to ensure that as much as possible of the surface runoff during the water year is attributable to the precipitation during the same water year. [ 1 ]
Due to meteorological and geographical factors, the definition of the water years varies. The United States Geological Survey (USGS) defines it as the period between October 1 of one year and September 30th of the next, [ 2 ] [ 3 ] as late September to early October is the time for many drainage areas in the US to have the lowest stream flow and consistent ground water levels.
The water year is designated by the calendar year in which it ends, so the 2025 water year started on October 1, 2024, and will end on September 30, 2025. [ 1 ]
One way to identify a water-year is to find the successive 12-month period that most consistently, year after year, gives the highest correlation between precipitation and streamflow and negligible changes in storage (i.e., soil water and snow). [ 4 ] Usually, the time when the variation of storage from year to year is the smallest is the time with the minimum storage level and minimum flow. However, the practical considerations also affect the water year definitions. For example, in Canada the water year starts in October, apparently to coincide with the US one, although better measurement conditions exist in winter. [ 5 ]
To accommodate the regional and climatic variations, some researchers use a per- gauge local water year that starts in the month with the lowest average streamflow . [ 6 ]
Water year types (or indices [ 7 ] ) are used to present the historical hydrological data in a simplified form. [ 8 ] These indices help to categorize similar water years for the planning of the rule-based [ 7 ] water operations. A typical set includes: very dry year , dry year , normal year, wet year , very wet year . [ 8 ] The years are characterized through setting numerical thresholds for the water runoff in the water year. The methods of calculation (and the set of types) naturally vary by the region, therefore many indices exists, for example: [ 7 ]
Many practically used indices were created ad-hoc . For example, California River Indices [ 12 ] are weighted averages of the estimates of spring melt , runoff for the rest of the year, and the result for the previous year, calculated for few river basins separately to classify the water year as a wet , above normal , below normal , dry , and critical ("normal" years in California are extremely rare [ 13 ] ). These California indices were not created "through a systematic statistical analysis of
historic basin conditions and river flows". [ 14 ]
All indices by nature reflect the historic values and therefore cannot capture the variations in climate that are known to cause the distribution of water year types to be non-stationary in time. [ 15 ]
Examples of how water year is used:
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https://en.wikipedia.org/wiki/Water_year
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