Desalination, desalinization, or desalinisation refers to any of several processes that remove some amount of salt and other minerals from saline water. More generally, desalination may also refer to the removal of salts and minerals,^[1] as in soil desalination.^[2]

Salt water is desalinated in order to produce fresh water that is suitable for human consumption or irrigation. One potential by-product of desalination is table salt. Desalination is used on many seagoing ships and submarines. Most of the modern interest in desalination is focused on developing cost-effective ways of providing fresh water for human use. Along with recycled wastewater, this is one of the few non-rainfall-dependent water sources.

Large-scale desalination typically uses large amounts of energy and specialized, expensive infrastructure, making it more expensive than fresh water from conventional sources such as rivers or groundwater.^[3]

Desalination is particularly relevant to countries like Australia which traditionally have relied on collecting rainfall behind dams to provide their drinking water supplies.

According to the International Desalination Association, in 2009 14,451 desalination plants operated worldwide, producing 59.9e6 cubic metres (2.12×10⁹ cu ft) per day, a year on year increase of 12.3%.^[4] It was 68 million in 2010, and expected to hit 120 million by 2020, some 40 million is planned for the Middle East.^[5] The world's largest desalination plant is the Jebel Ali Desalination Plant (Phase 2) in the United Arab Emirates.

Schematic of a multi-stage flash desalinator
A – Steam in
B – Seawater in
C – Potable water out
D – Waste out
E – Steam out
F – Heat exchange
G – Condensation collection
H – Brine heater

Plan of a typical reverse osmosis desalination plant

Methods[link]

The traditional process used in these operations is vacuum distillation—essentially the boiling of water at less than atmospheric pressure and thus a much lower temperature than normal. This is because the boiling of a liquid occurs when the vapor pressure equals the ambient pressure and vapor pressure increases with temperature. Thus, because of the reduced temperature, energy is saved. A leading distillation method is multi-stage flash distillation accounting for 85% of production worldwide in 2004.^[6]

Reverse osmosis desalination plant in Barcelona, Spain

The principal competing processes use membranes to desalinate, principally applying reverse osmosis technology.^[7] Membrane processes use semi-permeable membranes and pressure to separate salts from water. Reverse osmosis plant membrane systems typically use less energy than thermal distillation, which has led to a reduction in overall desalination costs over the past decade. Desalination remains energy intensive, however, and future costs will continue to depend on the price of both energy and desalination technology.

Considerations and criticism[link]

Cogeneration[link]

Cogeneration is the process of using excess heat from power production to accomplish another task. For desalination, cogeneration is the production of potable water from seawater or brackish groundwater in an integrated, or "dual-purpose", facility in which a power plant becomes the source of energy for desalination. Alternatively, the facility’s energy production may be dedicated to the production of potable water (a stand-alone facility), or excess energy may be produced and incorporated into the energy grid (a true cogeneration facility). There are various forms of cogeneration, and theoretically any form of energy production could be used. However, the majority of current and planned cogeneration desalination plants use either fossil fuels or nuclear power as their source of energy. Most plants are located in the Middle East or North Africa, which use their petroleum resources to offset limited water resources. The advantage of dual-purpose facilities is that they can be more efficient in energy consumption, thus making desalination a more viable option for drinking water.^[8][9]

Shevchenko BN350, a nuclear-heated desalination unit

In a December 26, 2007, opinion column in the The Atlanta Journal-Constitution, Nolan Hertel, a professor of nuclear and radiological engineering at Georgia Tech, wrote, "... nuclear reactors can be used ... to produce large amounts of potable water. The process is already in use in a number of places around the world, from India to Japan and Russia. Eight nuclear reactors coupled to desalination plants are operating in Japan alone ... nuclear desalination plants could be a source of large amounts of potable water transported by pipelines hundreds of miles inland..."^[10]

Additionally, the current trend in dual-purpose facilities is hybrid configurations, in which the permeate from a reverse osmosis desalination component is mixed with distillate from thermal desalination. Basically, two or more desalination processes are combined along with power production. Such facilities have already been implemented in Saudi Arabia at Jeddah and Yanbu.^[11]

A typical aircraft carrier in the U.S. military uses nuclear power to desalinate 400,000 US gallons (1,500,000 l; 330,000 imp gal) of water per day.^[12]

Economics[link]

Factors that determine the costs for desalination include: capacity and type of facility, location, feed water, labor, energy, financing, and concentrate disposal. Desalination stills now control pressure, temperature and brine concentrations to optimize efficiency. Nuclear-powered desalination might be economical on a large scale.^[13][14]

While noting that costs are falling, and generally positive about the technology for affluent areas that are proximate to oceans, a 2004 study argued that "Desalinated water may be a solution for some water-stress regions, but not for places that are poor, deep in the interior of a continent, or at high elevation. Unfortunately, that includes some of the places with biggest water problems." and "Indeed, one needs to lift the water by 2,000 metres (6,600 ft), or transport it over more than 1,600 kilometres (990 mi) to get transport costs equal to the desalination costs. Thus, it may be more economical to transport fresh water from somewhere else than to desalinate it. In places far from the sea, like New Delhi, or in high places, like Mexico City, high transport costs would add to the high desalination costs. Desalinated water is also expensive in places that are both somewhat far from the sea and somewhat high, such as Riyadh and Harare. In many places, the dominant cost is desalination, not transport; the process would therefore be relatively less expensive in places like Beijing, Bangkok, Zaragoza, Phoenix, and, of course, coastal cities like Tripoli."^[15] After being desalinated at Jubail, Saudi Arabia, water is pumped 200 miles (320 km) inland through a pipeline to the capital city of Riyadh.^[16] For coastal cities, desalination is increasingly viewed as an untapped and unlimited water source.

In Israel as of 2005 desalinating water cost US$0.53 per cubic meter.^[17] As of 2006 Singapore was desalinating water for US$0.49 per cubic meter.^[18] The city of Perth began operating a reverse osmosis seawater desalination plant in 2006, and the Western Australian government have announced that a second plant will be built to serve the city's needs.^[19] A desalination plant is now operating in Australia's largest city of Sydney,^[20] and the Wonthaggi desalination plant was under construction in Wonthaggi, Victoria.

The Perth desalination plant is powered partially by renewable energy from the Emu Downs Wind Farm.^[21] A wind farm at Bungendore in New South Wales was purpose-built to generate enough renewable energy to offset the Sydney plant's energy use,^[22] mitigating concerns about harmful greenhouse gas emissions, a common argument used against seawater desalination.

In December 2007, the South Australian government announced that it would build a seawater desalination plant for the city of Adelaide, Australia, located at Port Stanvac. The desalination plant was to be funded by raising water rates to achieve full cost recovery.^[23][24] An online, unscientific poll showed that nearly 60% of votes cast were in favor of raising water rates to pay for desalination.^[25]

A January 17, 2008, article in the Wall Street Journal stated, "In November, Connecticut-based Poseidon Resources Corp. won a key regulatory approval to build the US$300 million water-desalination plant in Carlsbad, north of San Diego. The facility would produce 50,000,000 US gallons (190,000,000 l; 42,000,000 imp gal) of drinking water per day, enough to supply about 100,000 homes ... Improved technology has cut the cost of desalination in half in the past decade, making it more competitive ... Poseidon plans to sell the water for about US $950 per acre-foot [1,200 cubic metres (42,000 cu ft)]. That compares with an average US$700 an acre-foot [1200 m³] that local agencies now pay for water." ^[26] $1,000 per acre-foot works out to $3.06 for 1,000 gallons, or $.81 for 1 cubic meter.^[27]

While this regulatory hurdle was met, Poseidon Resources is not able to break ground until the final approval of a mitigation project for the damage done to marine life through the intake pipe, as required by California law. Poseidon Resources has made progress in Carlsbad, CA, despite an unsuccessful attempt to complete construction of Tampa Bay Desal, a desalination plant in Tampa Bay, FL, in 2001. The Board of Directors of Tampa Bay Water was forced to buy Tampa Bay Desal from Poseidon Resources in 2001 to prevent a third failure of the project. Tampa Bay Water faced five years of engineering problems and operation at 20% capacity to protect marine life and stuck to reverse osmosis filters prior to fully utilizing this facility in 2007.^[28]

In 2008 San Leandro, California company (Energy Recovery Inc.) was desalinating water for US $0.46 per cubic meter.^[29]

A Jordanian-born chemical engineering doctoral student at University of Ottawa, named Mohammed Rasool Qtaisha, invented a new desalination technology that is alleged to produce between 600% and 700% more water output per square meter of membrane than current technology. General Electric is looking into similar technology, and the U.S. National Science Foundation funded University of Michigan to study it as well. Patent issues and details of the technology were unresolved as of 2008.^[30]

While desalinating 1,000 US gallons (3,800 l; 830 imp gal) of water can cost as much as $3, the same amount of bottled water costs $7,945.^[31]

Environmental[link]

Intake[link]

In the United States, due to a recent court ruling under the Clean Water Act, ocean water intakes are no longer viable without reducing mortality, by 90%, of the life in the ocean; the plankton, fish eggs and fish larvae.^[32] There are alternatives, including beach wells that eliminate this concern, but require more energy and higher costs while limiting output.^[33]

Outflow[link]

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2012)

All desalination processes produce large quantities of a concentrate, which may be increased in temperature, contain residues of pretreatment and cleaning chemicals, their reaction (by-)products, and heavy metals due to corrosion. Chemical pretreatment and cleaning is a necessity in most desalination plants, which typically includes the treatment against biofouling, scaling, foaming and corrosion in thermal plants, and against biofouling, suspended solids and scale deposits in membrane plants.^[34]

To limit the environmental impact of returning the brine to the ocean, it can be diluted with another stream of water entering the ocean, such as the outfall of a wastewater treatment plant or power plant. While seawater power plant cooling water outfalls are not as fresh as wastewater treatment plant outfalls, salinity is reduced. If the power plant is medium- to large-sized and the desalination plant is not enormous, the power plant's cooling water flow is likely to be at least several times larger than that of the desalination plant. Another method to reduce the increase in salinity is to mix the brine via a diffuser in a mixing zone. For example, once the pipeline containing the brine reaches the sea floor, it can split into many branches, each releasing brine gradually through small holes along its length. Mixing can be combined with power plant or waste water plant dilution.

Brine is denser than seawater due to higher solute concentration. The ocean bottom is most at risk because the brine sinks and remains there long enough to damage the ecosystem. Careful re-introduction can minimize this problem. For example, for the desalination plant and ocean outlet structures to be built in Sydney from late 2007, the water authority stated that the ocean outlets would be placed in locations at the seabed that will maximize the dispersal of the concentrated seawater, such that it will be indistinguishable beyond between 50–75 metres (160–246 ft) from the outlets. Typical oceanographic conditions off the coast allow for rapid dilution of the concentrated byproduct, thereby minimizing harm to the environment.

The Kwinana Desalination Plant opened In Perth, in 2007. Water there and at Queensland's Gold Coast Desalination Plant and Sydney's Desalination Plant is withdrawn at only 0.1 metres per second (0.33 ft/s), which is slow enough to let fish escape. The plant provides nearly 140,000 cubic metres (4,900,000 cu ft) of clean water per day.^[35]

Alternatives without pollution[link]

Some methods of desalination, particularly in combination with evaporation ponds and solar stills (solar desalination), do not discharge brine. They do not use chemicals in their process nor the burning of fossil fuels. They do not work with membranes or other critical parts, like components that include heavy metals, thus not causing toxic waste (and high maintenance). A new approach that works like a solar still, but on the scale of industrial evaporation ponds is the Integrated Biotectural System. ^[36] It can be considered "full desalination" because it converts the entire amount of salt-water intake into distilled water. One of the most unique advantages of this type of solar-powered desalination is the feasibility for inland operation. Standard advantages also include no air-pollution from desalination-power-plants and no temperature increase of endangered natural water bodies from power-plant cooling-water discharge. Another important advantage is the production of seasalt for industrial and other uses. Currently 50% of world-salt production still relies on fossil energy sources.

Alternatives to desalination[link]

Increased water conservation and efficiency remain the most cost-effective priorities in areas of the world where there is a large potential to improve the efficiency of water use practices.^[37] Wastewater reclamation for irrigation and industrial use provides multiple benefits over desalination.^[38] Urban runoff and storm water capture also provide benefits in treating, restoring and recharging groundwater.^[39]

A proposed alternative to desalinization in the American Southwest is the commercial importation of bulk water from water-rich areas either by very large crude carriers converted to water carriers, or via pipelines. The idea is politically unpopular in Canada, where governments imposed trade barriers to bulk water exports as a result of a claim filed in 1999 under Chapter 11 of the North American Free Trade Agreement (NAFTA) by Sun Belt Water Inc., a company established in 1990 in Santa Barbara, California, to address pressing local needs due to a severe drought in that area.^[40]

Experimental techniques and other developments[link]

Many desalination techniques have been researched, with varying degrees of success.

One such process was commercialised by Modern Water PLC using forward osmosis, with a number of plants reported in operation.^[41][42][43]

The U.S. government is working to develop practical solar desalination.^{[citation needed]}

The Passarell Process uses reduced atmospheric pressure rather than heat to drive evaporative desalination. The pure water vapor generated by distillation is then compressed and condensed using an advanced compressor. The compression process improves distillation efficiency by creating the reduced pressure in the evaporation chamber. The compressor centrifuges the pure water vapor after it is drawn through a demister (removing residual impurities) causing it to compress against tubes in the collection chamber. The compression of the vapor causes its temperature to increase. The heat generated is transferred to the input water falling in the tubes causing the water in the tubes to vaporize. Water vapor condenses on the outside of the tubes as product water. By combining several physical processes, Passarell enables most of the system's energy to be recycled through its subprocesses, namely evaporation, demisting, vapor compression, condensation, and water movement within the system.^[44]

Geothermal energy can drive desalination. In most locations geothermal desalination beats using scarce groundwater or surface water environmentally and economically.^{[citation needed]}

Nanotube membranes may prove to be effective for water filtration and desalination process that would require substantially less energy than reverse osmosis.^[45]

Biomimetic membranes are another approach.^[46]

On June 23, 2008, Siemens Water Technologies announced technology based on applying electric fields that desalinate one cubic meter of water while using only 1.5 kWh of energy, claimedly one half the energy of other processes.^[47] Currently Oasis Water who develops the technology still uses 3 times that much energy.

Fresh water can be produced by freezing seawater and is known as freeze-thaw desalination.

In 2009 Lux Research estimated that the worldwide desalinated water supply will triple between 2008 and 2020.^[48]

Desalination through evaporation and condensation for crops growth[link]

The Seawater Greenhouse uses natural evaporation and condensation processes inside a greenhouse powered by solar energy to grow crops in arid coastal land.

Low-temperature thermal desalination[link]

Originally stemming from ocean thermal energy conversion research, Low-temperature thermal desalination (LTTD) takes advantage of the fact that water boils at low pressures, potentially even at ambient temperature. The system uses vacuum pumps to create a low pressure, low-temperature environment in which water boils at a temperature gradient of 8–10 °C (46–50 °F) between two volumes of water. Cooling ocean water is supplied from depths of up to 600 metres (2,000 ft). This cold water is pumped through coils to condense the water vapor. The resulting condensate is purified water. LTTD may also take advantage of the temperature gradient available at power plants, where large quantities of warm waste water are discharged from the plant, reducing the energy input needed to create a temperature gradient.^[49]

Experiments were conducted in U.S. and Japan to test the approach. In Japan, a spray flash evaporation system was tested by Saga University.^[50] In Hawaii the National Energy Laboratory tested an open-cycle OTEC plant with fresh water and power production using a temperature of 20 °C (68 °F) between surface water and water at a depth of around 500 metres (1,600 ft). LTTD was studied by India's National Institute of Ocean Technology (NIOT) from 2004. Their first LTTD plant opened in 2005 at Kavaratti in the Lakshadweep islands. The plant's capacity is 100,000 litres (22,000 imp gal; 26,000 US gal)/day, at a capital cost of INR 50 million (€922,000). The plant uses deep water at a temperature of 7 to 15 °C (45 to 59 °F).^[51] In 2007, NIOT opened an experimental floating LTTD plant off the coast of Chennai with a capacity of 1,000,000 litres (220,000 imp gal; 260,000 US gal)/day. A smaller plant was established in 2009 at the North Chennai Thermal Power Station to prove the LTTD application where power plant cooling water is available.^[49][52][53]

Thermo-ionic process[link]

In October 2009, Saltworks Technologies, a Canadian firm, announced a process that uses solar or other thermal heat to drive an ionic current that removes all sodium and chlorine ions from the water usin ion-exchange membranes.^[54]

Existing facilities and facilities under construction[link]

Aruba[link]

The island of Aruba has a large (world’s largest at the time of its inauguration) desalination plant with the total installed capacity of 11.1e6 US gallons (42,000 m³) per day.^{[55][dead link]}

Australia[link]

A combination of increased water usage and lower rainfall/drought in Australia caused State governments to turn to desalination, including the recently commissioned Kurnell Desalination Plant serving the Sydney area. While desalination helped secure water supplies, it is energy intensive (~$140/ML) and has a high carbon footprint due to Australia's coal-based energy supply.^{[citation needed]} In 2010, a Seawater Greenhouse went into operation in Port Augusta.^[56][57][58]

Bahrain[link]

Completed in 2000, the Al Hidd Desalination Plant on Muharraq island employed a multistage flash process, and produces 272,760 cubic metres (9,632,000 cu ft) per day.^[59] The Al Hidd distillate forwarding station provides 410 million litres of distillate water storage in a series of 45 million litre steel tanks. A 135 million litres/day forwarding pumping station sends flows to the Hidd blending station, Muharraq blending station, Hoora blending station, Sanabis blending station and Seef blending station and which has an option for gravity supply for low flows to blending pumps and pumps which forward to Janusan, Budiya and Saar.^[60]

Upon completion of the third construction phase, the Durrat Al Bahrain sea water reverse osmosis (SWRO) desalination plant was planned to have a capacity of 36,000 cubic meters of potable water per day to serve the irrigation needs of the Durrat Al Bahrain development.^[61] The Bahrain-based utility company, Energy Central Co (ECC) contracted to design, build and operate the plant.^[62]

China[link]

China operates the Beijiang Desalination Plant in Tianjin, a combination desalination and coal-fired power plant designed to alleviate Tianjin's critical water shortage. Though the facility has the capacity to produce 200,000 cubic meters of potable water per day, it has never operated at more than one quarter capacity due to difficulties with local utility companies and an inadequate local infrastructure.^[63]

Cyprus[link]

A plan operates in Cyprus near the town of Larnaca.^[64] The Dhekelia Desalination Plant utilises the reverse osmosis system.^[65]

Gibraltar[link]

Fresh water in Gibraltar is supplied by a number of reverse osmosis and multi-stage flash desalination plants.^[66] A demonstration forward osmosis desalination plant also operates there.^[67]

Hong Kong[link]

The Water Supplies Department had a pilot desalination plant in Tuen Mun and Ap Lei Chau using reverse osmosis technology. The production cost was at HK$7.8 to HK$8.4 per cubic metre.^[68][69] In 2011 the government announced a feasibility study to build a desalination plant in Tseung Kwan O.^[70] Hong Kong used to have a desalination plant in Lok On Pai.^[71]

Israel[link]

The Hadera seawater reverse osmosis (SWRO) desalination plant in Israel is the largest of its kind in the world.^[72][73] The project was developed as a Build-Operate-Transfer (BOT) by a consortium of two Israeli companies: Shikun and Binui and IDE Technologies.^[74]

Jersey[link]

The desalination plant located near La Rosière, Corbiere, Jersey is operated by Jersey Water. Built in 1970 in an abandoned quarry, it was the first in the British Isles.

The original plant used a multi-stage flash (MSF) distillation process, whereby seawater was boiled under vacuum, evaporated and condensed into a fresh water distillate. In 1997 the MSF plant reached the end of its operational life and was replaced with a modern reverse osmosis plant.

Its maximum power demand is 1,750kW, and the output capacity is 6,000 cubic metres per day. Specific energy consumption is 6.8kWh per cubic metre.<produced.^[81]

Maldives[link]

Maldives is a nation of small islands. Some depend on desalination as a source of water.^{[citation needed]}

Oman[link]

A pilot Seawater Greenhouse was built in 2004 near Muscat, in collaboration with Sultan Qaboos University, providing a sustainable horticultural sector on the Batinah coast.^[82]

Saudi Arabia[link]

The Saline Water Conversion Corporation of Saudi Arabia provides 50% of the municipal water in the Kingdom, operates a number of desalination plants, and has contracted $1892 million ^[83] to a Japanese-South Korean consortium to build a new facility capable of producing a billion litres a day, opening at the end of 2013. They currently operate approximately 14 plants in the Kingdom; one example at Shoaiba cost $1060 million and produces 450 million litres a day.^[84]

Spain[link]

Lanzarote is the easternmost of the autonomous Canary Islands. It is of volcanic origin and has limited water supplies. A private, commercial desalination plant was installed in 1964. This served the whole island and enabled the tourism industry. In 1974 the venture was injected with investments from local and municipal governments and a larger infrastructure was put in place. In 1989 INALSA^[85] was formed as the Lanzarote Island Waters Consortium.

A prototype Seawater Greenhouse was constructed in Tenerife in 1992.^[86]

El Prat, near Barcelona, has a desalination plant completed in 2009 and meant to provide water to the Barcelona metropolitan area, specially during the periodic severe droughts that put the drinking water provision under serious stress.

United Arab Emirates (Abu Dhabi)[link]

The Jebel Ali desalination plant in Dubai is a dual-purpose facility that uses multi-stage flash distillation and is capable of producing 300e6 cubic metres (1.1×10¹⁰ cu ft) of water per year. By comparison the largest desalination plant in the United States is located in Tampa Bay, Florida, and operated by Tampa Bay Water, which began desalinating 34.7 million cubic meters of water per year in December 2007.^[87] The Tampa Bay plant runs at around 12% the output of the Jebel Ali Desalination Plants. The largest desalination plant in South Asia is the Minjur Desalination Plant near Chennai in India which produces 36.5 million cubic meters of water per year.^[88][89]

• Taweelah A1 Power and Desalination Plant has an output 385,000,000 litres (85,000,000 imp gal; 102,000,000 US gal) per day of clean water.
• Umm Al Nar Desalination Plant has an output of 394,000,000 litres (87,000,000 imp gal; 104,000,000 US gal) per day of clean water.
• Fujairah F2 is to be completed by July 2010 will have a water production capacity of 492,000,000 litres (108,000,000 imp gal; 130,000,000 US gal) per day.^[90]
• A Seawater Greenhouse was constructed on Al-Aryam Island, Abu Dhabi, United Arab Emirates in 2000.

United Kingdom[link]

The first large scale water desalination plant in the United Kingdom, the Thames Water Desalination Plant, was built in Beckton, east London for Thames Water by Acciona Agua.^[91]

United States[link]

El Paso (Texas) Desalination Plant[link]

Brackish groundwater has been treated at the El Paso plant since around 2004. It produces 27,500,000 US gallons (104,000,000 l; 22,900,000 imp gal) of fresh water daily (about 25% of total freshwater deliveries) by reverse osmosis.^[92]

Tampa Bay Water Desalination Project[link]

The Tampa Bay Water Desalination project was originally a private venture led by Poseidon Resources. This project was delayed by the bankruptcy of Poseidon Resources' successive partners in the venture, Stone & Webster, then Covanta (formerly Ogden) and its principal subcontractor Hydranautics. Stone & Webster crashed in June 2000 declaring bankruptcy. Covanta and Hydranautics joined in 2001, but Covanta failed to complete construction bonding and the Tampa Bay Water agency purchased the project on May 15, 2002, underwriting project financing. Tampa Bay Water then contracted with Covanta Tampa Construction, which produced a project that failed performance tests. After its parent went bankrupt, Covanta also filed for bankruptcy prior to performing renovations that would have satisfied contractual agreements. This resulted in nearly six months of litigation. In 2004, Tampa Bay Water hired a renovation team, American Water/Acciona Aqua, to bring the plant to its original, anticipated design. The plant was deemed fully operational in 2007^[28] and is designed to run at a maximum capacity of 25 million US gallons (95,000 m³) per day.^[93] Nevertheless, as of 2009 problems limited it to producing only about half that amount (14 million US gallons (53,000 m³).^[94]

Yuma Desalting Plant (Arizona)[link]

The Yuma Desalting Plant was constructed under authority of the Colorado River Basin Salinity Control Act of 1974 to treat saline agricultural return flows from the Wellton-Mohawk Irrigation and Drainage District. The treated water is intended for inclusion in water deliveries to Mexico thereby preserving a like amount of water in Lake Mead. Construction of the plant was completed in 1992 and it has operated on two occasions since then. The plant has been maintained, but largely not operated due to sufficient water supply conditions on the Colorado River.^[95] An agreement was reached in April 2010 between the Southern Nevada Water Authority, the Metropolitan Water District of Southern California, the Central Arizona Project and the U.S. Bureau of Reclamation to underwrite the cost of running the plant in a year long pilot project.^[96]

Trinidad and Tobago[link]

The Republic of Trinidad and Tobago uses desalination to free up more of the island's water supply for drinking purposes. The desalination facility, opened in March 2003, is considered to be the first of its kind. It was the largest desalination facility in the Americas and processes 28,800,000 US gallons (109,000,000 l; 24,000,000 imp gal) of water a day at the price of $2.67 per 1,000 US gallons (3,800 l; 830 imp gal).^[97] This facility will be located at Trinidad's Point Lisas Industrial Estate, a park of more than 12 companies in various manufacturing and processing functions and will allow for easy access to water for both factories and residents in the country.^[98]

In nature[link]

Mangrove leaf with salt crystals

Evaporation of water over the oceans in the water cycle is a natural desalination process.

The formation of sea ice is also a process of desalination. Salt is expelled from seawater when it freezes. Although some brine is trapped, the overall salinity of sea ice is much lower than seawater.

Giant Petrel with brine emitting tube nostril

Seabirds distill sea water, by using countercurrent exchange in a gland with a Rete mirabile. The gland secretes highly concentrated brine stored near the nostrils above the beak. The bird then "sneezes" the brine out to the sea. As freshwater is not available in their environment, seabirds like pelicans, petrels, albatrosses, gulls and terns possess this gland which allows the birds to drink the salty water from their environment while they are hundreds miles away from land.^[99][100]

Mangroves are trees which grow in seawater. Mangroves secrete salt by trapping it into parts of the root, which are then eaten by animals (usually crabs). Additional salt removal is done by storing it in leaves which then fall off. Some types of mangrove have glands on the leaf, which work in a similar way to the seabird desalination gland. Salt is extracted to the leaf exterior as small crystals, which then fall off the leaf.

Willow trees and reeds are known to absorb salt and other contaminants, effectively desalinating the water. This is used in artificial constructed wetlands, for treating sewage.^{[citation needed]}

See also[link]

References[link]

Further reading[link]

• Committee on Advancing Desalination Technology, National Research Council. (2008). Desalination: A National Perspective. National Academies Press.

Articles[link]

• Desalination: The next wave in global water consumption from TLVInsider
• Elimelech, M.; Phillip, W. A. (2011). "The Future of Seawater Desalination: Energy, Technology, and the Environment". Science 333 (6043): 712–717. DOI:10.1126/science.1200488. PMID 21817042. http://physics.indiana.edu/~brabson/p310/WaterDesalEgy.pdf.  Significant review article.

External links[link]

• International Desalination Association
• Examples of sea water desalination plants by the WWWS AG
• GeoNoria Solar Desalination Process
• National Academies Press|Desalination: A National Perspective
• World Wildlife Fund|Desalination: option or distraction?
• European Desalination Society
• IAEA – Nuclear Desalination
• DME – German Desalination Society
• Large scale desalination of sea water using solar energy
• Desalination by humidification and dehumidification of air: state of the art
• Zonnewater – optimized solar thermal desalination (distillation)
• SOLAR TOWER Project – Clean Electricity Generation for Desalination.
• Desalination bibliography Library of Congress
• Water-Technology
• Cheap Drinking Water from the Ocean – Carbon nanotube-based membranes will dramatically cut the cost of desalination
• Solar thermal-driven desalination plants based on membrane distillation
• Encyclopedia of Water Sciences, Engineering and Technology Resources
• wind-powered desalinization plant in Perth, Australia, is an example of how technology is insulating rich countries from impacts of climate change, while poor countries remain particularly vulnerable.
• The Desal Response Group
• Encyclopedia of Desalination and water and Water Resources
• Desalination & Water Reuse – Desalination news
• Desalination: The Cyprus Experience
• Desalination: The Jersey Water plant at La Rosière, Corbiere