Desalination

This article is about removing salt from water. For soil desalination, see Soil salinity control.

Desalination or desalinization is a process that removes minerals from saline water. More generally, desalination may also refer to the removal of salts and minerals, as in soil desalination, which also happens to be a major issue for agricultural production.

Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. One potential by-product of desalination is 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 rainfall-independent water sources.

Due to relatively high energy consumption, the costs of desalinating sea water are generally higher than the alternatives (fresh water from rivers or groundwater, water recycling and water conservation), but alternatives are not always available and rapid overdraw and depletion of reserves is a critical problem worldwide. Quoting Christopher Gasson of Global Water Intelligence, "At the moment, around 1% of the world's population are dependent on desalinated water to meet their daily needs, but by 2025, the UN expects 14% of the world's population to be encountering water scarcity. Unless people get radically better at water conservation, the desalination industry has a very strong future indeed."

Desalination is particularly relevant in dry countries such as Australia, which traditionally have relied on collecting rainfall behind dams to provide their drinking water supplies. According to the International Desalination Association, in June 2011, 15,988 desalination plants operated worldwide, producing 66.5 million cubic meters per day, providing water for 300 million people. This number has been updated to 78.4 million cubic meters by 2013, or 57% greater than just 5 years prior. The single largest desalination project is Ras Al-Khair in Saudi Arabia, which produced 1,025,000 cubic meters per day in 2014, although this plant in Saudi Arabia is expected to be surpassed by a desal plant in California. The largest percent of desalinated water used in any country is in Israel, which produces 40% of its domestic water use from seawater desalination.

Schematic of a multistage 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

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, low-temperature "waste" heat from electrical power generation or industrial processes can be used.

Reverse osmosis desalination plant in Barcelona, Spain

The principal competing processes use membranes to desalinate, principally applying reverse osmosis technology. Membrane processes use semipermeable 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

Energy consumption

Energy consumption of sea water desalination can be as low as 3 kWh/m³, including pre-filtering and ancillaries, similar to the energy consumption of existing fresh water supplies transported over large distances, but much higher than local fresh water supplies which use 0.2 kWh/m³ or less.

A minimum energy consumption for sea water desalination of around 1 kWh/m³ has been determined, excluding prefiltering and intake/outfall pumping. Under 2 kWh/m³ has been achieved with existing reverse osmosis membrane technology, leaving limited scope for further energy reductions.

Supplying all domestic water by sea water desalination would increase the United States' energy consumption by around 10%, about the amount of energy used by domestic refrigerators.

However, domestic consumption is a relatively small fraction of the total water usage in the United States.

The table below shows the energy consumption of sea water desalination methods.

Desalination Method >>	Multi-stage Flash MSF	Multi-Effect Distillation MED	Mechanical Vapor Compression MVC	Reverse Osmosis RO
Electrical energy (kWh/m3)	4–6	1.5–2.5	7–12	3–5.5
Thermal energy (kWh/m3)	50–110	60–110	None	None
Electrical equivalent of thermal energy (kWh/m3)	9.5–19.5	5–8.5	None	None
Total equivalent electrical energy (kWh/m3)	13.5–25.5	6.5–11	7–12	3–5.5

Note: "Electrical equivalent" refers to the amount of electrical energy which could be generated using a given quantity of thermal energy and appropriate turbine generator. In addition, these calculations do not include the energy required to construct or refurbish consumable items used up in the processes.

Cogeneration

Cogeneration is the process of using excess heat from electricity generation for another task: in this case the production of potable water from seawater or brackish groundwater in an integrated, or "dual-purpose", facility where a power plant provides the 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). Cogeneration takes various forms, 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 they can be more efficient in energy consumption, thus making desalination a more viable option for drinking water.

The Shevchenko BN350, a nuclear-heated desalination unit

In a December 26, 2007, opinion column in 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..."

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.

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

Economics

Costs of desalinating sea water (infrastructure, energy, and maintenance) are generally higher than the alternatives (fresh water from rivers or groundwater, water recycling, and water conservation), but alternatives are not always available. Achievable costs in 2013 range from US$0.45 to $1.00/cubic metre ($US2 to 4/kgal). (1 cubic meter is about 264 gallons.) However, more than half of the total cost of desalination comes directly from energy cost, and since energy price is very volatile, any calculated cost of desalination is only good based on the energy price at the time of calculation.

The cost of untreated fresh water in the developing world can reach US$5/cubic metre.

Average water consumption and cost of supply by sea water desalination (±50%)

Area	Consumption USgal/person/day	Consumption litre/person/day	Desalinated Water Cost US$/person/day
USA	100	378	0.29
Europe	50	189	0.14
Africa	15	57	0.05
UN recommended minimum	13	49	0.04

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.

While noting costs are falling, and generally positive about the technology for affluent areas in proximity to oceans, a 2004 study argued, "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 m (6,600 ft), or transport it over more than 1,600 km (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." After being desalinated at Jubail, Saudi Arabia, water is pumped 200 mi (320 km) inland through a pipeline to the capital city of Riyadh. For coastal cities, desalination is increasingly viewed as an untapped and unlimited water source.

In 2014, the Israeli facilities of Hadera, Palmahim, Ashkelon, and Sorek were desalinizing water for less than US$0.40 per cubic meter. As of 2006, Singapore was desalinating water for US$0.49 per cubic meter. The city of Perth began operating a reverse osmosis seawater desalination plant in 2006, and the Western Australian government announced a second plant will be built to serve the city's needs. A desalination plant is now operating in Australia's largest city, Sydney, 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. 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, mitigating concerns about harmful greenhouse gas emissions, a common argument used against seawater desalination.

In December 2007, the South Australian government announced 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. An online, unscientific poll showed nearly 60% of votes cast were in favor of raising water rates to pay for desalination.

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 $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 $950 per acre-foot [1,200 cubic meters (42,000 cu ft)]. That compares with an average [of] $700 an acre-foot [1200 m³] that local agencies now pay for water." In June 2012, new estimates were released that showed the cost for the desalinated water had risen to $2,329 per acre-foot. Each $1,000 per acre-foot works out to $3.06 for 1,000 gallons, or $.81 per cubic meter.

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 is received, as required by California law. Poseidon Resources has made progress in Carlsbad, 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, so stuck to reverse osmosis filters prior to fully using this facility in 2007.

In 2008, a San Leandro, California company (Energy Recovery Inc.) was desalinating water for $0.46 per cubic meter.

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 (purchased individually in half-liter bottles).

Lastly, desalination may provide flexibility or real options to the overall water supply system, a point that is highly valuable and critical in motivating the decision of desalination in Singapore and other cities.

Environmental

Intake

In the United States, cooling water intake structures are regulated by the Environmental Protection Agency under Section 316(b) of the Clean Water Act. These intake structures can have the same impacts to the environment as desalination facility intakes. According to the EPA, water intake structures cause adverse environmental impact by pulling large numbers of fish and shellfish or their eggs into an industrial system. There, the organisms may be killed or injured by heat, physical stress, or chemicals. Larger organisms may be killed or injured when they are trapped against screens at the front of an intake structure. Alternative intake types which avoid this environmental impact include beach wells, but these require more energy and higher costs, while limiting output.

The Kwinana Desalination Plant opened in Perth in 2007. Water there and at Queensland's Gold Coast Desalination Plant and Sydney's Kurnell Desalination Plant is withdrawn at only 0.1 m/s (0.33 ft/s), which is slow enough to let fish escape. The plant provides nearly 140,000 m³ (4,900,000 cu ft) of clean water per day.

Outflow

All desalination processes produce large quantities of a concentrate, which may be increased in temperature, and contain residues of pretreatment and cleaning chemicals, their reaction byproducts, and heavy metals due to corrosion. Chemical pretreatment and cleaning are 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.

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 or power plant. While seawater power plant cooling water outfalls are not as fresh as wastewater treatment plant outfalls, salinity is reduced. With medium to large power plant and desalination plant, 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 wastewater 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 reintroduction 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 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 and 75 meters (164 and 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.

Alternatives without pollution

Some methods of desalination, particularly in combination with evaporation ponds, solar stills, and condensation trap (solar desalination), do not discharge brine. They do not use chemicals in their processes nor the burning of fossil fuels. They do not work with membranes or other critical parts, such as components that include heavy metals, thus do not cause 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. It can be considered "full desalination" because it converts the entire amount of saltwater intake into distilled water. One of the 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 sea salt for industrial and other uses. Currently, 50% of the world's sea salt production still relies on fossil energy sources.

Alternatives to desalination

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. Wastewater reclamation for irrigation and industrial use provides multiple benefits over desalination. Urban runoff and storm water capture also provide benefits in treating, restoring and recharging groundwater.

A proposed alternative to desalination 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.

Public Health concerns

Israeli researchers have found possible link between seawater desalination and iodine deficiency. Their study, conducted by Yaniv Ovadia, registered dietitian, by the supervision of Dr Dov Gefel and Dr Aron M Troen from the Barzilai Medical center Ashkelon and the Hebrew University Jerusalem, revealed prevalent, apparent iodine deficiency among euthyroid adults exposed to iodine-poor water simultaneously with supply of an ever-increasing seawater reverse osmosis (SWRO) proportion of their area's drinking water. These researchers underscored the need for reliable data on iodine intake and status to illuminate the implications of SWRO desalination on health for populations in regions that are increasingly dependent on desalinated-water.

Experimental techniques and other developments

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

Desalination powered by waste heat

Diesel generators are commonly used to provide electricity in remote areas. They typically produce about 40%–50% of the energy as low-grade heat which leaves the engine via the exhaust. By connecting a membrane distillation system to the diesel engine exhaust it is possible to use this low-grade heat which is currently wasted. Furthermore, the membrane distillation system actively cools the diesel generator, improving its efficiency and hence increasing its electricity output. This results in an energy-neutral desalination solution. An example of such a desalination plant was commissioned by Dutch company Aquaver in March 2014 in the island of Gulhi, Maldives.

Low-temperature thermal desalination

Originally stemming from ocean thermal energy conversion research, low-temperature thermal desalination (LTTD) takes advantage of water boiling 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 m (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 wastewater are discharged from the plant, reducing the energy input needed to create a temperature gradient.

Experiments were conducted in the US and Japan to test the approach. In Japan, a spray-flash evaporation system was tested by Saga University. In Hawaii, the National Energy Laboratory tested an open-cycle OTEC plant with fresh water and power production using a temperature difference of 20 C° between surface water and water at a depth of around 500 m (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 L (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 10 to 12 °C (50 to 54 °F). In 2007, NIOT opened an experimental, floating LTTD plant off the coast of Chennai, with a capacity of 1,000,000 L (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.

Thermoionic process

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 using ion-exchange membranes.

Desalination through evaporation and condensation for crops

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

Other approaches

One such process was commercialized by Modern Water PLC using forward osmosis, with a number of plants reported to be in operation.

The United States, France and the United Arab Emirates are working to develop practical solar desalination. AquaDania's WaterStillar has been installed at Dahab, Egypt, and in Playa del Carmen, Mexico. In this approach, a solar thermal collector measuring two square metres can distill from 40 to 60 litres per day from any local water source – five times more than conventional stills and eliminating the need for polluting plastic PET bottles or tranportation of water supply. In Central California, a startup company WaterFX is developing a solar-powered method of desalination that can enable the use of local water, including runoff water that can be treated and used again. Salty groundwater in the region would be treated to become freshwater, and in areas near the ocean, seawater could be treated.

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.

Geothermal energy can drive desalination. In most locations, geothermal desalination beats using scarce groundwater or surface water, environmentally and economically.

Nanotube membranes may prove to be effective for water filtration and desalination processes that would require substantially less energy than reverse osmosis.

Hermetic, sulphonated nano-composite membranes have shown to be capable of cleaning most all forms of contaminated water to the 'parts per billion' level. These nano-materials, using a non-reverse osmosis process, have little or no susceptibility to high salt concentration levels.

Abstracted animation of the nanoscale graphene membrane desalination process.

Biomimetic membranes are another approach.

On June 23, 2008, Siemens Water Technologies announced technology based on applying electric fields that purports to desalinate one cubic meter of water while using only 1.5 kWh of energy. If accurate, this process would consume only one-half the energy of other processes. Currently, Oasis Water, which developed the technology, still uses three times that much energy. Researchers at the University of Texas at Austin and the University of Marburg are developing more efficient methods of electrochemically mediated seawater desalination.

Freeze-thaw desalination uses freezing to remove fresh water from frozen seawater.

Membraneless desalination at ambient temperature and pressure using electrokinetic shocks waves has been demonstrated. In this technique anions and cations in salt water are exchanged for carbonate anions and calcium cations respectively using electrokinetic shockwaves. Calcium and carbonate ions then react to form calcium carbonate, which then precipitates leaving behind fresh water. Theoretical energy efficiency of this method is on par with electrodialysis and reverse osmosis.

In 2009, Lux Research estimated the worldwide desalinated water supply will triple between 2008 and 2020.

Existing facilities and facilities under construction

Estimates vary widely between 15,000–20,000 desalination plants producing more than 20,000 m³/day. Micro desalination plants are in operation nearly every where there is a natural gas or fracking facility in the United States.

Algeria

Believed to have at least 15 desalination plants in operation

• Arzew IWPP Power & Desalination Plant, Arzew
• Cap Djinet Seawater Reverse Osmosis(SWRO) 100,000 m³/d
• Tlemcen Souk Tleta 200,000 m³/day
• Tlemcen Hounaine 200,000 m³/day
• Beni Saf 200,000 m³/day
• Tenes 200,000 m³/day
• Fouka 120,000 m³/day
• Skikda 100,000 m³/day
• Hamma Seawater Desalination Plant 200,000 m³/day built by GE
• Mostaganem, (Sonaghter) 200,000m3/day
• Magtaa Reverse Osmosis (RO) Desalination Plant 500 000m3/day, Oran, Algeria

Aruba

The island of Aruba has a large (world's largest at the time of its inauguration) desalination plant, with a total installed capacity of 11.1 million US gallons (42,000 m³) per day.

Australia

Main article: Seawater desalination in Australia

The Millenium Drought (1997–2009) led to a water supply crisis across much of the country. A combination of increased water usage and lower rainfall/drought in Australia caused state governments to turn to desalination. As a result, several large-scale desalination plants were constructed (see list).

Large-scale seawater reverse osmosis plants (SWRO) now contribute to the domestic water supplies of several major Australian cities including Adelaide, Melbourne, Sydney, Perth and the Gold Coast. 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. In 2010, a Seawater Greenhouse went into operation in Port Augusta.

A growing number of smaller scale SWRO plants are used by the oil and gas industry (both on and offshore), by mining companies to supply slurry pipelines for the transport of ore and on offshore islands to supply tourists and residents.

Bahrain

Completed in 2000, the Al Hidd Desalination Plant on Muharraq island employed a multistage flash process, and produces 272,760 m³ (9,632,000 cu ft) per day. The Al Hidd distillate forwarding station provides 410 million liters of distillate water storage in a series of 45-million-liter steel tanks. A 135-million-liters/day forwarding pumping station sends flows to the Hidd, Muharraq, Hoora, Sanabis, and Seef blending stations, and which has an option for gravity supply for low flows to blending pumps and pumps which forward to Janusan, Budiya and Saar.

Upon completion of the third construction phase, the Durrat Al Bahrain seawater 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. The Bahrain-based utility company, Energy Central Co contracted to design, build and operate the plant.

Chile

• Copiapó Desalination Plant
• Thorium Power Canada, with its affiliate, DBI Chile, have proposed plans to build a 10 MW demonstration thorium reactor in Chile to power the 2000 litre/day desalination plant. All land and regulatory approvals are currently in process.

China

China operates the Beijing 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.

Cyprus

A plant operates in Cyprus near the town of Larnaca. The Dhekelia Desalination Plant uses the reverse osmosis system.

Egypt

• Dahab RO Desalination Plants Dahab 3,600 m³/day completed 1999
• Hurgada and Sharm El-Sheikh Power and Desalination Plants
• Oyoun Moussa Power and Desalination
• Zaafarana Power and Desalination

Germany

Fresh water on the island of Helgoland is supplied by two reverse osmosis desalination plants.

Gibraltar

Fresh water in Gibraltar is supplied by a number of reverse osmosis and multistage flash desalination plants. A demonstration forward osmosis desalination plant also operates there.

Grand Cayman

• West Bay, West Bay, Grand Cayman
• Abel Castillo Water Works, Governor's Harbour, Grand Cayman
• Britannia, Seven Mile Beach, Grand Cayman

Hong Kong

The Hong Kong Water Supplies Department had pilot desalination plants in Tuen Mun and Ap Lei Chau using reverse-osmosis technology. The production cost was put at HK$7.8 to HK$8.4 /m³. Hong Kong used to have a desalination plant in Lok On Pai.

In 2014, the government confirmed the reservation of a 10-hectare site at Tseung Kwan O for the construction of a reverse-osmosis desalination plant with an initial output capacity of 50 million cubic metres per annum. Plans include provisions for future expansion to an ultimate capacity of 90 million cubic metres per annum, which will meet about 10 per cent of Hong Kong's fresh water demand. Detailed feasibility studies, preliminary design and a cost-effectiveness analysis are planned to be completed by 2014. A commissioning date of 2020 is envisaged.

India

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.

A second plant at Nemmeli, Chennai is expected to reach full capacity of 100 million litres of sea-water per day in March 2013.

Iran

An assumption is that around 400,000 m³/d of historic and newly installed capacity is operational in Iran. In terms of technology, Iran's existing desalination plants use a mix of thermal processes and RO. MSF is the most widely used thermal technology although MED and vapour compression (VC) also feature.

Israel

Israel Desalination Enterprises' Sorek Desalination Plant in Palmachim provides up to 26,000 m³ of potable water per hour (2.300 m³ p.a.). At full capacity, it is the largest desalination plant of its kind in the world. Once unthinkable, given Israel's history of drought and lack of available fresh water resource, with desalination, Israel can now actually produce a surplus of fresh water.

The Hadera seawater reverse osmosis (SWRO) desalination plant in Israel is the largest of its kind in the world. The project was developed as a build–operate–transfer by a consortium of two Israeli companies: Shikun and Binui, and IDE Technologies.

By 2014, Israel's desalination programs provided roughly 35% of Israel's drinking water and it is expected to supply 40% by 2015 and 70% by 2050. As of May 29, 2015 more than 50 percent of the water for Israeli households, agriculture and industry is artificially produced.

Existing Israeli water desalination facilities

Location	Opened	Capacity (million m3/year)	Cost of water (per m3)	Notes
Ashkelon	August 2005	120 (as of 2010)	NIS 2.60
Palmachim	May 2007	45	NIS 2.90
Hadera	December 2009	127	NIS 2.60
Sorek	2013	228	NIS 2.01 – 2.19

Israeli water desalination facilities under construction

Location	Opening	Capacity (million m3/year)	Cost of water (per m3)	Notes
Ashdod	September 2014	100 (expansion up to 150 possible)	NIS 2.40

Malta

Ghar Lapsi II 50,000 m³/day

Maldives

Maldives is a nation of small islands. Some depend on desalination as a source of water.

Oman

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.

• Ghubrah Power & Desalination Plant, Muscat
• Sohar Power & Desalination Plant, Sohar
• Sur R.O. Desalination Plant 80,000 m³/day 2009
• Qarn Alam 1,000 m³/day
• Wilayat Diba 2,000 m³/day

There are at least two forward osmosis plants operating in Oman

• Al Najdah 200 m³/day (built by Modern Water)
• Al Khaluf

Qatar

• Ras Abu fontas (RAF) A2 - 160,000  m³/day. The country has plans for two plants with an additional 194 million gallons / day

Saudi Arabia

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 $1.892 billion to a Japanese-South Korean consortium to build a new facility capable of producing a billion liters per day, opening at the end of 2013. They currently operate 32 plants in the Kingdom; one example at Shoaiba cost $1.06 billion and produces 450 million liters per day.

• Corniche RO Plant (Crop) (operated by SAWACO)
• Jubail 800,000 m³/day
• North Obhor Plant (operated by SAWACO)
• Rabigh 7,000 m³/day (operated by wetico)
• planned for completion 2018 Rabigh II 600,000 m³/day (under construction Saline Water Conversion Corporation)
• Shuaibah III 150,000 m³/day (operated by Doosan)
• South Jeddah Corniche Plant (SOJECO) (operated by SAWACO)
• Yanbu Multi Effect Distillation (MED), Saudi Arabia 68,190 m³/day

Spain

Lanzarote is the easternmost of the autonomous Canary Islands, which are of volcanic origin. It is the closest of the islands to the Sahara desert and therefore the driest, and it has limited water supplies. A private, commercial desalination plant was installed in 1964 to serve the whole island and enable 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, the Lanzarote Island Waters Consortium (INALSA) was formed.

A prototype seawater greenhouse was constructed in Tenerife in 1992.

• Alicante II 65,000 m³/day (operator Inima)
• Tordera 60,000 m³/day
• Barcelona 200,000 m³/day (operator Degremont) El Prat, near Barcelona, a desalination plant completed in 2009 was meant to provide water to the Barcelona metropolitan area, especially during the periodic severe droughts that put the available amounts of drinking water under serious stress.
• Oropesa 50,000 m³/day (operator TECNICAS REUNIDAS)
• Moncofa 60,000 m³/day (operator Inima)
• Marina Baja – Mutxamel 50,000 m³/day (operator Degremont)
• Torrevieja 240,000 m³/day (operator ACCIONA)
• Cartagena Escombreras 63,000 m³/day (operator COBRA | TEDAGUA)
• Edam Ibiza + Edam San Antonio 25,000 m³/day (operator Ibiza – Portmany)
• Mazarron 36,000 m³/day (operator TEDAGUA)
• Bajo Almanzora 65,000 m³/day

South Africa

• Mossel Bay 15,000 m³/day

Transnet Saldanha 2,400 m³/day

• Knysna 2,000 m³/day
• Plettenberg Bay 2,000 m³/day
• Bushman's River Mouth 1,800 m³/day
• Lambert's Bay 1,700 m³/day
• Cannon Rocks 750 m³/day

United Arab Emirates

The Jebel Ali desalination plant in Dubai, a dual-purpose facility, uses multistage flash distillation and is capable of producing 300 million cubic meters of water per year.

• Kalba 15,000 m³/day built for Sharjah Electricity and Water Authority completed 2010 (operator CH2MHill)
• Khor Fakkan 22,500 m³/day (operator CH2MHill)
• Ghalilah RAK 68,000 m³/day (operator AQUATECH)
• Hamriyah 90,000 m³/day (operator AQUA Engineering)
• Taweelah A1 Power and Desalination Plant has an output 385,000,000 L (85,000,000 imp gal; 102,000,000 US gal) per day of clean water.
• Al Zawrah 27,000 m³/day (operator Aqua Engineering)
• Layyah I 22,500 m³/day (operator CH2MHill)
• Emayil & Saydiat Island ≈20,000 m³/day (operator Aqua EPC)
• Umm Al Nar Desalination Plant has an output of 394,000,000 L (87,000,000 imp gal; 104,000,000 US gal)/day.
• Al Yasat Al Soghrih Island 2M gallons per day (GPD) or 9,000 m³/day
• Fujairah F2 is to be completed by July 2010 will have a water production capacity of 492,000,000 L (108,000,000 imp gal; 130,000,000 US gal) per day.
• A seawater greenhouse was constructed on Al-Aryam Island, Abu Dhabi, United Arab Emirates in 2000.

United Kingdom

The first large-scale plant in the United Kingdom, the Thames Water Desalination Plant, was built in Beckton, east London for Thames Water by Acciona Agua.

Jersey

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 multistage flash (MSF) distillation process, whereby seawater was boiled under vacuum, evaporated and condensed into a freshwater 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 1,750 kW, and the output capacity is 6,000 cubic meters per day. Specific energy consumption is 6.8 kWh/m³.

United States

Texas

There are a dozen different desalination projects in the state of Texas, both for desalinating groundwater and desalinating seawater from the Gulf of Mexico.

• El Paso: Brackish groundwater has been treated at the El Paso, Texas, 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. The plant's water cost—largely representing the cost of energy—is about 2.1 times higher than ordinary groundwater production. On average, the plant produces 3.5 million gallons per day (about 11 acre-feet) at an average production cost of $489 per acre-foot.

California

California has 17 desalination plants in the works, either partially constructed or through exploration and planning phases. The list of locations includes Bay Point, in the Delta, Redwood City, seven in the Santa Cruz / Monterey Bay, Cambria, Oceaneo, Redondo Beach, Huntington Beach, Dana Point, Camp Pendleton, Oceanside and Carlsbad.

• Carlsbad: The Carlsbad desalination plant being constructed by Poseidon Resources will be the largest desalination plant in the United States when it goes online in 2016. It is expected to produce 50 million gallons a day to 110,000 customers in San Diego County at an estimated cost of $1b.
• Concord: Planned to open in 2020, producing 20 million gallons a day.
• Monterey County: Sand City, two miles north of Monterey, with a population of 334, is the only city in California completely supplied with water from a desalination plant.
• Santa Barbara: The Charles Meyer Desalination Facility was constructed in Santa Barbara, California, in 1991–92 as a temporary emergency water supply in response to severe drought. While it has a high operating cost, the facility only needs to operate infrequently, allowing Santa Barbara to use its other supplies more extensively. The plant is expected to be re-activated in the summer of 2016.

Florida

RO production train, North Cape Coral RO Plant

In 1977 Cape Coral, Florida became the first municipality in the United States to use the RO process on a large scale with an initial operating capacity of 3 million gallons per day. By 1985, due to the rapid growth in population of Cape Coral, the city had the largest low pressure reverse osmosis plant in the world, capable of producing 15 MGD.

As of 2012, South Florida has 33 brackish and two seawater desalination plants operating with seven brackish water plants under construction. The brackish and seawater desalination plants have the capacity to produce 245 million gallons of potable water per day.

• Tampa Bay: The Tampa Bay Water desalination project near Tampa, Florida, was originally a private venture led by Poseidon Resources, but it 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 declared bankruptcy June 2000. Covanta and Hydranautics joined in 2001, but Covanta failed to complete the construction bonding, and then the Tampa Bay Water agency purchased the project on May 15, 2002, underwriting the project. 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, and is designed to run at a maximum capacity of 25 million US gallons (95,000 m³) per day. The plant can now produce up to 25 million US gallons (95,000 m³) per day when needed.

Arizona

• Yuma: The desalination plant in Yuma, Arizona, was constructed under authority of the Federal Colorado River Basin Salinity Control Act of 1974 to treat saline agricultural return flows from the Wellton-Mohawk Irrigation and Drainage District into the Colorado River. The treated water is intended for inclusion in water deliveries to Mexico, thereby keeping a like amount of freshwater in Lake Mead, Arizona and Nevada. 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 freshwater supplies from the upper Colorado River. 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.

Trinidad and Tobago

The Republic of Trinidad and Tobago uses desalination to open up more of the island's water supply for drinking purposes. The country's desalination plant, opened in March 2003, is considered to be the first of its kind. It was the largest desalination facility in the Americas, and it processes 28,800,000 US gallons (109,000 m³) of water a day at the price of $2.67 per 1,000 US gallons (3.8 m³).

This plant will be located at Trinidad's Point Lisas Industrial Estate, a park of more than 12 companies in various manufacturing and processing functions, and it will allow for easy access to water for both factories and residents in the country.

In nature

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.

Seabirds distill seawater 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. As freshwater is not usually available in their environments, some seabirds, such as pelicans, petrels, albatrosses, gulls and terns, possess this gland, which allows them to drink the salty water from their environments while they are hundreds of miles away from land.

Mangrove trees grow in seawater; they 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 mangroves have glands on their leaves, 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.

See also

• Adelaide Desalination Plant
• Brine
• Dewvaporation
• Peak water
• Salinity control
• Soil desalination model
• Seawater
• Soil salinity
• Soil salinity and groundwater model
• Spragg Bags
• Pumpable ice technology
• Water supply
• Atmospheric water generator

References

Further reading

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

Articles

• 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" (PDF). Science 333 (6043): 712–717. Bibcode:2011Sci...333..712E. doi:10.1126/science.1200488. PMID 21817042.  Significant review article.

External links

• International Desalination Association
• Desalination timeline
• 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
• Desalination and Membrane Technologies: Federal Research and Adoption Issues Congressional Research Service
• Desalination Articles, Commentary and Archive - The New York Times Newspaper