Desalination is a process that takes away mineral components from saline water. More generally, desalination refers to the removal of salts and minerals from a target substance, as in soil desalination, which is an issue for agriculture.
Saltwater is desalinated to produce water suitable for human consumption or irrigation. One 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 cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few rainfall-independent water sources.
Due to its energy consumption, desalinating sea water is generally more costly than fresh water from rivers or groundwater, water recycling and water conservation. However, these alternatives are not always available and depletion of reserves is a critical problem worldwide. Desalination processes are usually driven by either thermal (e.g. distillation) or electrical (e.g., photovoltaic or wind power) as the primary energy types.
Currently, approximately 1% of the world's population is dependent on desalinated water to meet daily needs, but the UN expects that 14% of the world's population will encounter water scarcity by 2025. Desalination is particularly relevant in dry countries such as Australia, which traditionally have relied on collecting rainfall behind dams for water.
According to the International Desalination Association, in June 2015, 18,426 desalination plants operated worldwide, producing 86.8 million cubic meters per day, providing water for 300 million people. This number increased from 78.4 million cubic meters in 2013, a 10.71% increase in 2 years. The single largest desalination project is Ras Al-Khair in Saudi Arabia, which produced 1,025,000 cubic meters per day in 2014. Kuwait produces a higher proportion of its water than any other country, totaling 100% of its water use.
There are several methods. Each has advantages and disadvantages but all are useful.
Solar distillation mimics the natural water cycle, in which the sun heats the sea water enough for evaporation to occur. After evaporation, the water vapor is condensed onto a cool surface. There are two types of solar desalination. The former one is using photo voltaic cells which converts solar energy to electrical energy to power the desalination process. The later one utilises the solar energy in the heat form itself and is known as solar thermal powered desalination.
In vacuum distillation atmospheric pressure is reduced, thus lowering the temperature required to evaporate the water. Liquids boil when the vapor pressure equals the ambient pressure and vapor pressure increases with temperature. Effectively, liquids boil at a lower temperature, when the ambient atmospheric pressure is less than usual atmospheric pressure. Thus, because of the reduced pressure, low-temperature "waste" heat from electrical power generation or industrial processes can be employed.
Water is evaporated and separated from sea water through multi-stage flash distillation, which is a series of flash evaporations. Each subsequent flash process utilizes energy released from the condensation of the water vapor from the previous step.
Multiple-effect distillation (MED) works through a series of steps called "effects". Incoming water is sprayed onto pipes which are then heated to generate steam. The steam is then used to heat the next batch of incoming sea water. To increase efficiency, the steam used to heat the sea water can be taken from nearby power plants. Although this method is the most thermodynamically efficient among methods powered by heat, a few limitations exist such as a max temperature and max number of effects.
Vapor-compression evaporation involves using either a mechanical compressor or a jet stream to compress the vapor present above the liquid. The compressed vapor is then used to provide the heat needed for the evaporation of the rest of the sea water. Since this system only requires power, it is more cost effective if kept at a small scale.
The leading process for desalination in terms of installed capacity and yearly growth is reverse osmosis (RO). The RO membrane processes use semipermeable membranes and applied pressure (on the membrane feed side) to preferentially induce water permeation through the membrane while rejecting salts. Reverse osmosis plant membrane systems typically use less energy than thermal desalination processes. Energy cost in desalination processes varies considerably depending on water salinity, plant size and process type. At present the cost of seawater desalination, for example, is higher than traditional water sources, but it is expected that costs will continue to decrease with technology improvements that include, but are not limited to, improved efficiency, reduction in plants footprint, improvements to plant operation and optimization, more effective feed pretreatment, and lower cost energy sources.
Reverse osmosis uses a thin-film composite membrane, which comprises an ultra-thin, aromatic polyamide thin-film. This polyamide film gives the membrane its transport properties, whereas the remainder of the thin-film composite membrane provides mechanical support. The polyamide film is a dense, void-free polymer with a high surface area, allowing for its high water permeability.
The reverse osmosis process is not maintenance free. Various factors interfere with efficiency: ionic contamination (calcium, magnesium etc.); DOC; bacteria; viruses; colloids and insoluble particulates; biofouling and scaling. In extreme cases, the RO membranes are destroyed. To mitigate damage, various pretreatment stages are introduced. Anti-scaling inhibitors include acids and other agents such as the organic polymers polyacrylamide and polymaleic acid, phosphonates and polyphosphates. Inhibitors for fouling are biocides (as oxidants against bacteria and viruses), such as chlorine, ozone, sodium or calcium hypochlorite. At regular intervals, depending on the membrane contamination; fluctuating seawater conditions; or when prompted by monitoring processes, the membranes need to be cleaned, known as emergency or shock-flushing. Flushing is done with inhibitors in a fresh water solution and the system must go offline. This procedure is environmentally risky, since contaminated water is diverted into the ocean without treatment. Sensitive marine habitats can be irreversibly damaged.
Off-grid solar-powered desalination units use solar energy to fill a buffer tank on a hill with seawater. The reverse osmosis process receives its pressurized seawater feed in non-sunlight hours by gravity, resulting in sustainable drinking water production without the need for fossil fuels, an electricity grid or batteries.Nano-tubes are also used for the same function (i.e, Reverse Osmosis).
Freeze-thaw desalination uses freezing to remove fresh water from salt water. Salt water is sprayed during freezing conditions into a pad where an ice-pile builds up. When seasonal conditions warm, naturally desalinated melt water is recovered. This technique relies on extended periods of natural sub-freezing conditions.
A different freeze-thaw method, not weather dependent and invented by Alexander Zarchin, freezes seawater in a vacuum. Under vacuum conditions the ice, desalinated, is melted and diverted for collection and the salt is collected.
CETO is a wave power technology that desalinates seawater using submerged buoys. Wave-powered desalination plants began operating on Garden Island in Western Australia in 2013 and in Perth in 2015.
Energy consumption of seawater desalination has reached as low as 3 kWh/m3, including pre-filtering and ancillaries, similar to the energy consumption of other fresh water supplies transported over large distances, but much higher than local fresh water supplies that use 0.2 kWh/m3 or less.
A minimum energy consumption for seawater desalination of around 1 kWh/m3 has been determined, excluding prefiltering and intake/outfall pumping. Under 2 kWh/m3 has been achieved with reverse osmosis membrane technology, leaving limited scope for further energy reductions.
Supplying all US domestic water by desalination would increase domestic energy consumption by around 10%, about the amount of energy used by domestic refrigerators. Domestic consumption is a relatively small fraction of the total water usage.
|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 that could be generated using a given quantity of thermal energy and appropriate turbine generator. These calculations do not include the energy required to construct or refurbish items consumed in the process.
Cogeneration is generating excess heat and electricity generation from a single process. Cogeneration can provide usable heat for desalination 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. 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 more viable.
The current trend in dual-purpose facilities is hybrid configurations, in which the permeate from reverse osmosis desalination is mixed with distillate from thermal desalination. Basically, two or more desalination processes are combined along with power production. Such facilities have been implemented in Saudi Arabia at Jeddah and Yanbu.
Costs of desalinating sea water (infrastructure, energy, and maintenance) are generally higher than fresh water from rivers or groundwater, water recycling, and water conservation, but alternatives are not always available. Desalination costs in 2013 ranged from US$0.45 to $1.00/cubic metre. More than half of the cost comes directly from energy cost, and since energy prices are very volatile, actual costs can vary substantially.
The cost of untreated fresh water in the developing world can reach US$5/cubic metre.
|Area||Consumption Litre/person/day||Desalinated Water Cost US$/person/day|
|UN recommended minimum||49||0.05|
Factors that determine the costs for desalination include capacity and type of facility, location, feed water, labor, energy, financing and concentrate disposal. Desalination stills 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 2000 m, or transport it over more than 1600 km 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, transport costs could match 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. By contrast in other locations transport costs are much less, such as Beijing, Bangkok, Zaragoza, Phoenix, and, of course, coastal cities like Tripoli." After desalination at Jubail, Saudi Arabia, water is pumped 320 km inland to Riyadh. For coastal cities, desalination is increasingly viewed as a competitive choice.
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. Perth began operating a reverse osmosis seawater desalination plant in 2006. A desalination plant now operates in 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.
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.
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 190,000 cubic metres of drinking water per day, enough to supply about 100,000 homes. As of June 2012, 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.
Poseidon Resources made an unsuccessful attempt to construct a desalination plant in Tampa Bay, FL, in 2001. The board of directors of Tampa Bay Water was forced to buy the plant from Poseidon 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. The facility reached capacity only in 2007.
Factors that determine the costs for desalination include capacity and type of facility, location, feed water, labor, energy, financing and concentrate disposal.
In the United States, cooling water intake structures are regulated by the Environmental Protection Agency (EPA). These structures can have the same impacts to the environment as desalination facility intakes. According to EPA, water intake structures cause adverse environmental impact by sucking 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 become trapped against screens at the front of an intake structure. Alternative intake types that mitigate these impacts include beach wells, but they require more energy and higher costs.
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 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.
Desalination processes produce large quantities of brine, possibly at above ambient 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 prevention of biofouling, scaling, foaming and corrosion in thermal plants, and of 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. With medium to large power plant and desalination plants, the power plant's cooling water flow is likely to be several times larger than that of the desalination plant, reducing the salinity of the combination. Another method to dilute the brine is to mix it via a diffuser in a mixing zone. For example, once a 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 and therefore sinks to the ocean bottom and can damage the ecosystem. Careful reintroduction can minimize this problem.
Increased water conservation and efficiency remain the most cost-effective approaches in areas with a large potential to improve the efficiency of water use practices. Wastewater reclamation 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 oil tankers converted to water carriers, or pipelines. The idea is politically unpopular in Canada, where governments imposed trade barriers to bulk water exports as a result of a North American Free Trade Agreement (NAFTA) claim.
Desalination removes iodine from water and could increase the risk of iodine deficiency disorders. Israeli researchers claimed a possible link between seawater desalination and iodine deficiency, finding deficits among euthyroid adults exposed to iodine-poor water concurrently with an increasing proportion of their area's drinking water from seawater reverse osmosis (SWRO). They later found probable iodine deficiency disorders in a population reliant on desalinated seawater. A possible link of heavy desalinated water use and national iodine deficiency was suggested by Israeli researchers. They found a high burden of iodine deficiency in the general population of Israel: 62% of school-age children and 85% of pregnant women fall below the WHO’s adequacy range. They also pointed out the national reliance on iodine-depleted desalinated water, the absence of a universal salt iodization program and reports of increased use of thyroid medication in Israel as a possible reasons that the population’s iodine intake is low. In the year that the survey was conducted, the amount of water produced from the desalination plants constitutes about 50% of the quantity of fresh water supplied for all needs and about 80% of the water supplied for domestic and industrial needs in Israel.
Due to the nature of the process, there is a need to place the plants on approximately 25 acres of land on or near the shoreline. In the case a plant is built inland, pipes have to be laid into the ground to allow for easy intake and outtake. However, once the pipes are laid into the ground, they have a possibility of leaking into and contaminating nearby aquifers. Aside from environmental risks, the noise generated by certain types of desalination plants can be loud.
Despite the issues associated with desalination processes, public support for its development can be very high. One survey of a Southern California community saw 71.9% of all respondents being in support of desalination plant development in their community. In many cases, high freshwater scarcity corresponds to higher public support for desalination development whereas areas with low water scarcity tend to have less public support for its development.
Other desalination techniques include:
Thermally-driven desalination technologies are frequently suggested for use with low-temperature waste heat sources, as the low temperatures are not useful for many industrial processes, but ideal for the lower temperatures found in desalination. In fact, such pairing with waste heat can even improve electrical process: Diesel generators commonly provide electricity in remote areas. About 40%–50% of the energy output is low-grade heat that leaves the engine via the exhaust. Connecting a thermal desalination technology such as membrane distillation system to the diesel engine exhaust repurposes this low-grade heat for desalination. The system actively cools the diesel generator, improving its efficiency and increasing its electricity output. This results in an energy-neutral desalination solution. An example plant was commissioned by Dutch company Aquaver in March 2014 for Gulhi, Maldives.
Originally stemming from ocean thermal energy conversion research, low-temperature thermal desalination (LTTD) takes advantage of water boiling at low pressure, even at ambient temperature. The system uses 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. Cool ocean water is supplied from depths of up to 600 m (2,000 ft). This water is pumped through coils to condense the water vapor. The resulting condensate is purified water. LTTD may 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) in 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.
In October 2009, Saltworks Technologies 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.
Adsorption-based desalination (AD) relies on the moisture absorption properties of certain materials such as Silica Gel.
The idea of the method is in the fact that when the hydrogel is put into contact with aqueous salt solution, it swells absorbing a solution with the ion composition different from the original one. This solution can be easily squeezed out from the gel by means of sieve or microfiltration membrane. The compression of the gel in closed system lead to change in salt concentration, whereas the compression in open system, while the gel is exchanging ions with bulk, lead to the change in the number of ions. The consequence of the compression and swelling in open and closed system conditions mimics the reverse Carnot Cycle of refrigerator machine. The only difference is that instead of heat this cycle transfers salt ions from the bulk of low salinity to a bulk of high salinity. Similarly to the Carnot cycle this cycle is fully reversible, so can in principle work with an ideal thermodynamic efficiency. Because the method is free from the use of osmotic membranes it can compete with reverse osmosis method. In addition, unlike the reverse osmosis, the approach is not sensitive to the quality of feed water and its seasonal changes, and allows the production of water of any desired concentration.
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. It eliminates the need for plastic PET bottles or energy-consuming water transport. 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 increases its temperature. The heat is transferred to the input water falling in the tubes, vaporizing the water in the tubes. 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 evaporation, demisting, vapor compression, condensation, and water movement processes.
Geothermal energy can drive desalination. In most locations, geothermal desalination beats using scarce groundwater or surface water, environmentally and economically.
Nanotube membranes of higher permeability than current generation of membranes may lead to eventual reduction in the footprint of RO desalination plants. It has also been suggested that the use of such membranes will lead to reduction in the energy needed for desalination.
Hermetic, sulphonated nano-composite membranes have shown to be capable of removing a various contaminants to the parts per billion level. s, have little or no susceptibility to high salt concentration levels.
In 2008, Siemens Water Technologies announced technology that applied electric fields to desalinate one cubic meter of water while using only a purported 1.5 kWh of energy. If accurate, this process would consume one-half the energy of other processes. As of 2012 a demonstration plant was operating in Singapore. Researchers at the University of Texas at Austin and the University of Marburg are developing more efficient methods of electrochemically mediated seawater desalination.
A process employing electrokinetic shocks waves can be used to accomplish membraneless desalination at ambient temperature and pressure. In this process, anions and cations in salt water are exchanged for carbonate anions and calcium cations, respectively using electrokinetic shockwaves. Calcium and carbonate ions react to form calcium carbonate, which precipitates, leaving fresh water. The theoretical energy efficiency of this method is on par with electrodialysis and reverse osmosis.
A group of researchers from Columbia University have developed a process designed to purify industrial hypersaline brines. They call it Temperature Swing Solvent Extraction (TSSE). TSSE can desalinate extremely salty brine up to seven times as salty as the ocean. For comparison, the current methods can only handle brine twice as salty. Unlike other approaches that use reverse osmosis or distillation, TSSE has found success with using a solvent. Solvent extraction is commonly used during chemical engineering. The TSSE solvent isn't dependent on the evaporation of water, meaning it doesn't need high temperatures to work. It can be activated by low-grade heat (less than 70 degrees celsius) that is easy to attain, sometimes to the point of it being natural. In a study, TSSE removed up to 98.4 percent of the salt in brine.
Estimates vary widely between 15,000–20,000 desalination plants producing more than 20,000 m3/day. Micro desalination plants operate near almost every natural gas or fracking facility found in the United States.
Evaporation of water over the oceans in the water cycle is a natural desalination process.
The formation of sea ice produces ice with little salt, much lower than in 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 far from land.
Mangrove trees grow in seawater; they secrete salt by trapping it in parts of the root, which are then eaten by animals (usually crabs). Additional salt is removed by storing it in leaves that 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.
Desalination has been known to history for millennia as both a concept, and later practice, though in a limited form. The ancient Greek philosopher Aristotle observed in his work Meteorology that “salt water, when it turns into vapour, becomes sweet and the vapour does not form salt water again when it condenses,” and also noticed that a fine wax vessel would hold potable water after being submerged long enough in seawater, having acted as a membrane to filter the salt. There are numerous other examples of experimentation in desalination throughout Antiquity and the Middle Ages, but desalination was never feasible on a large scale until the modern era.
Before the Industrial Revolution, desalination was primarily of concern to oceangoing ships, which otherwise needed to keep on board supplies of fresh water. When Protector (1779 frigate) was sold to Denmark in the 1780s (as the ship Hussaren) the desalination plant was studied and recorded in great detail.
In the newly formed United States, Thomas Jefferson catalogued heat-based methods going back to the 1500s, and formulated practical advice that was publicized to all U.S. ships on the backs of sailing clearance permits.
Significant research into improved desalination methods occurred in the United States after World War II. The Office of Saline Water was created in the United States Department of the Interior by the Saline Water Conversion Act of 1952. It was merged into the Office of Water Resources Research in 1974.
Research also took place at state universities in California, followed by development at the Dow Chemical Company and DuPont. Many studies focus on ways to optimize desalination systems.
This project is the world’s first commercial-scale wave energy array that is connected to the grid and has the ability to produce desalinated water.
The Adelaide Desalination plant (ADP), formerly known as the Port Stanvac Desalination Plant, is a sea water reverse osmosis desalination plant located in Lonsdale, South Australia which has the capacity to provide the city of Adelaide with up to 50% of its drinking water needs.
In September 2007, South Australian Premier Mike Rann announced that the State Government would fund and build a desalination plant to insure Adelaide's water supply against drought. The plant was financed and built by SA Water, a state-owned corporation.
The plant was initially planned to have a capacity of 50 gigalitres (GL) of water per year, but was later doubled in capacity to 100 GL/year with the assistance of funding from the Australian Government. The expanded capacity represents around 50% of Adelaide's domestic water supply.
The plant was completed on time and within the original budget ($1.83 billion).
Stage one of the plant commenced operations in October 2011, and stage two commenced in July 2012. The plant was officially opened on 26 March 2013.The Adelaide Desalination Project is the largest infrastructure project that the State of South Australia has funded, owns, and has completed successfully.Since 2012, the plant has been operating at 10% of its capacity to keep it functioning. In 2017, it produced 2% of the state's water supply.Brine
Brine is a high-concentration solution of salt in water. In different contexts, brine may refer to salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of solutions used for brining foods) up to about 26% (a typical saturated solution, depending on temperature). Lower levels of concentration are called by different names: fresh water, brackish water, and saline water.
Brine naturally occurs on the Earth's surface (salt lakes), crust, and within brine pools on ocean bottom. High-concentration brine lakes typically emerge due to evaporation of ground saline water on high ambient temperatures. Brine is used for food processing and cooking (pickling and brining), for de-icing of roads and other structures, and in a number of technological processes. It is also a by-product of many industrial processes, such as desalination, and may pose an environmental risk due to its corrosive and toxic effects, so it requires wastewater treatment for proper disposal.Chennai MetroWater Supply and Sewage Board
Chennai Metropolitan Water Supply and Sewerage Board known as CMWSSB provides Water supply and sewage treatment to the city of Chennai and areas around it.
Chennai is one of the metros in India which is dependent mostly on ground water supply. Ground water in Chennai is replenished by rain water and average rainfall in Chennai is 1276 mm. Chennai receives about 985 million liters per day (mld) from various sources against the required amount of 1200 mld and the demand is expected to rise to 2100 mld by 2031. The newly constructed Minjur desalination plant adds another 100 mlds to the city's growing demand.
As of 2012, Chennai Metrowater supplies about 830 million litres of water every day to residents and commercial establishments.Geothermal desalination
Geothermal desalination is a process under development for the production of fresh water using heat energy. Claimed benefits of this method of desalination are that it requires less maintenance than reverse osmosis membranes and that the primary energy input is from geothermal heat, which is a low-environmental-impact source of energy.
Circa 1995, Douglas Firestone from Nevada devised the use of geothermal water directly as a source for desalination. In 1998, several individuals began working with evaporation/condensation air loop water desalination. The experiment was successful and a proof of concept, proving that geothermal waters could be used as process water to produce potable water in 2001.
In 2005 to 2009 testing was done in a sixth prototype of a device referred to as a delta t device, a closed air loop, atmospheric pressure, evaporation condensation loop geothermally powered desalination device. The device used filtered sea water from Scripps Institution of Oceanography and reduced the salt concentration from 35,000 ppm to 51 ppm.
A total of six prototypes and six modifications demonstrated that, with process water approaching 100 °C (212 °F) and a chill source about 2 °C (36 °F), a full-size device would produce about 600 m³ of water per day. Salt concentration in the wastewater would only be about 10% above the level of the original water, thus, from, say, 35,000 to about 38,000 parts per million, well within the ability of osmoregulators to adjust.Gold Coast Desalination Plant
The Gold Coast desalination plant is a 125 ML/d (46 gigalitres per year) reverse osmosis, water desalination plant located in Tugun, a seaside suburb of the Gold Coast. It supplies water to the South East Queensland region via the South East Queensland Water Grid.
The plant first supplied water to the grid in February 2009. It is owned by Seqwater and operated by Veolia. The plant is currently in 'hot standby' mode, which means it is not in permanent use but is capable of being brought back on line when needed.Multi-stage flash distillation
Multi-stage flash distillation (MSF) is a water desalination process that distills sea water by flashing a portion of the water into steam in multiple stages of what are essentially countercurrent heat exchangers. Multi-stage flash distillation plants produce about 26% of all desalinated water in the world, but today virtually all new desalination plants use reverse osmosis due to much lower energy consumption.Nahal Sorek
Nahal Sorek (Hebrew: נחל שורק, lit. Brook of Sorek), also Soreq, is one of the largest, most important drainage basins in the Judean Hills. It is mentioned in the Book of Judges 16:4 of the Bible as the border between the ancient Philistines and the Tribe of Dan of the ancient Israelites. It is known in Arabic as Wadi es-Sarār, sometimes spelled Surar, and by various names along different segments, such as Wadi Qalunya near Motza, Wadi al-Tahuna, and Nahr Rubin further downstream.Queensland Water Commission
The Queensland Water Commission (QWC) is a defunct Queensland Government agency established to develop long term water supply strategies. The Commission was chaired by Mary Boydell and the chief executive officer was John Bradley.
The agency was responsible for setting water restriction policy and coordinating water infrastructure projects in the state. In South East Queensland, the Commission established a regional water grid known as the SEQ Water Grid and the Western Corridor Recycled Water Project. Together with new dams and desalination plants the Commission aimed to counter the worst effects of drought in Australia.
As part of 50-year South East Queensland water strategy the QWC recommended that the Government of Queensland focus on recycled water projects, rather than desalination plants, because desalination plants are too energy intensive and recycled water provides supply regardless of changes in climate.On 1 January 2013, the Queensland Water Commission ceased operations. Policy-making functions of the Commission were assumed by the Queensland Department of Energy and Water Supply and its planning and regulatory functions became the responsibility of Seqwater.Reverse osmosis
Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to remove ions, unwanted molecules and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential differences of the solvent, a thermodynamic parameter. Reverse osmosis can remove many types of dissolved and suspended chemical species as well as biological ones (principally bacteria) from water, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as solvent molecules, i.e., water, H2O) to pass freely.In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (high water potential), through a membrane, to an area of high solute concentration (low water potential). The driving force for the movement of the solvent is the reduction in the free energy of the system when the difference in solvent concentration on either side of a membrane is reduced, generating osmotic pressure due to the solvent moving into the more concentrated solution. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications.
Reverse osmosis differs from filtration in that the mechanism of fluid flow is by osmosis across a membrane. The predominant removal mechanism in membrane filtration is straining, or size exclusion, where the pores are 0.01 micrometers or larger, so the process can theoretically achieve perfect efficiency regardless of parameters such as the solution's pressure and concentration. Reverse osmosis instead involves solvent diffusion across a membrane that is either nonporous or uses nanofiltration with pores 0.001 micrometers in size. The predominant removal mechanism is from differences in solubility or diffusivity, and the process is dependent on pressure, solute concentration, and other conditions. Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules.Sydney Desalination Plant
The Sydney Desalination Plant is a potable drinking water desalination plant that forms part of the water supply system of Greater Metropolitan Sydney. The plant is located in the Kurnell industrial estate, in Southern Sydney in the Australian state of New South Wales. The plant uses reverse osmosis filtration membranes to remove salt from seawater and is powered using renewable energy, supplied to the national power grid from the Infigen Energy–owned Capital Wind Farm located at Bungendore.
The Sydney Desalination Plant is owned by the Government of New South Wales. In 2012, the NSW Government entered into a 50–year lease with Sydney Desalination Plant Pty Ltd (SDP), a company jointly owned by the Ontario Teachers' Pension Plan Board (50%) and two funds managed by Hastings Funds Management Limited: Utilities Trust of Australia and The Infrastructure Fund (together 50%). The terms of the A$2.3 billion lease lock Sydney Water into a 50–year water supply agreement with SDP. The operator of the plant is Veolia Water Australia Pty Ltd.
The Sydney Desalination Plant is the third major desalination plant built in Australia, after Kwinana in Perth which was completed in 2006 and Tugun on the Gold Coast which was completed in 2009.Sydney Water
Sydney Water or formally, Sydney Water Corporation, is a New South Wales Government–owned statutory corporation that provides potable drinking water, wastewater and some stormwater services to Greater Metropolitan Sydney, the Illawarra and the Blue Mountains regions, in the Australian state of New South Wales.Thames Water Desalination Plant
The Thames Water Desalination Plant or Beckton Desalination Plant is a water desalination plant in Beckton, London, United Kingdom. The first of its kind in the UK, it was constructed for Thames Water by a consortium of Interserve, Atkins Water and Acciona Agua. The plant was officially opened by Prince Philip, Duke of Edinburgh on 2 June 2010. The plant can provide up to 150 million litres of drinking water each day – enough for nearly one million people.Victorian Desalination Plant
The Victorian Desalination Plant (also referred to as the Victorian Desalination Project or Wonthaggi desalination plant) is a water desalination plant in Dalyston, on the Bass Coast in southern Victoria, Australia. The project was announced by Premier Steve Bracks in June 2007, at the height of the crippling millennium drought when Melbourne's water storage levels dropped to 28.4%, a drop of more than 20% from the previous year. Increased winter-spring rains after mid-2007 took water storage levels above 40%, but it was not until 2011 that storages returned to pre-2006 levels.
The plant was completed in December 2012, and was the largest addition to Melbourne's water system since the Thomson River Dam was completed in 1983. However, at the time, Melbourne's reservoirs were at 81% capacity, and the plant was immediately put into standby mode. The first water released for public use was in March 2017 via Cardinia Reservoir.
As a rainfall-independent source of water the desalination plant complements Victoria's existing drainage basins, being a useful resource in times of drought. It is a controversial part of Victoria's water system, with ongoing costs of $608 million a year. Construction commenced in mid-2009. While the project will supply water for Melbourne, it is being managed by the Department of Sustainability & Environment (DSE) as a public-private partnership (PPP). DSE awarded the tender for design, build and operation to another company that will in turn supply the water to Melbourne Water, that makes payments to the plant owners and operators, Aquasure (Thiess/Suez). Melbourne Water pays the owner of the plant, even if no water is ordered, $608 million a year, or $1.8 million per day, for 27 years. The total payment is between $18 and $19 billion. On 1 April each year, the Minister for Water places an order for the following financial year, up to 150 gigalitres a year, at an additional cost to Melbourne Water and consumers.Water security
Water security has been defined as "the reliable availability of an acceptable quantity and quality of water for health, livelihoods and production, coupled with an acceptable level of water-related risks". It is realised to the degree that water scarcity is non-existent, or has been decreased or eliminated, and to the degree that floods and contamination of freshwater supplies are non-threatening.
"Sustainable development will not be achieved without a water secure world. A water secure world integrates a concern for the intrinsic value of water with a concern for its use for human survival and well-being. A water secure world harnesses water's productive power and minimises its destructive force. Water security also means addressing environmental protection and the negative effects of poor management. It is also concerned with ending fragmented responsibility for water and integrating water resources management across all sectors—finance, planning, agriculture, energy, tourism, industry, education and health. A water secure world reduces poverty, advances education, and increases living standards. It is a world where there is an improved quality of life for all, especially for the most vulnerable—usually women and children—who benefit most from good water governance."The areas of the world that are most likely to have water insecurity are places with low rainfall, places with rapid population growth in a freshwater scarce area, and areas with international competition over a water source.Water supply and sanitation in Algeria
Drinking water supply and sanitation in Algeria is characterized by achievements and challenges. Among the achievements is a substantial increase in the amount of drinking water supplied from reservoirs, long-distance water transfers and desalination at a low price to consumers, thanks to the country's substantial oil and gas revenues. These measures increased per capita water supply despite a rapidly increasing population. Another achievement is the transition from intermittent to continuous water supply in the capital Algiers in 2011, along with considerable improvements in wastewater treatment resulting in better water quality at beaches. These achievements were made possible through a public-private partnership with a private French water company. The number of wastewater treatment plants throughout the country increased rapidly from only 18 in 2000 to 113 in 2011, with 96 more under construction. However, there are also many challenges. One of them is poor service quality in many cities outside Algiers with 78% of urban residents suffering from intermittent water supply. Another challenge is the pollution of water resources. There has also been insufficient progress concerning reuse of treated water, a government priority in this dry country.Water supply and sanitation in Australia
As the country's supply of freshwater is increasingly vulnerable to droughts, possibly as a result of climate change, there is an emphasis on water conservation and various regions have imposed restrictions on the use of water.
In 2006, Perth became the first Australian city to operate a seawater desalination plant, the Kwinana Desalination Plant, to reduce the city's vulnerability to droughts. A plant at Kurnell has also been built and supplies Sydney metropolitan area with water during droughts and low dam levels. More plants are planned or are under construction in Gold Coast, Melbourne, and Adelaide. The use of reclaimed water is also increasingly common.
However, some desalination plants were put in stand-by modes in 2010 following above average rainfall levels and floods in 2010.
Governments of Australian states and territories, through state-owned companies, are in charge of service provision in Western Australia, South Australia and the Northern Territory, while utilities owned by local governments provide services in parts of Queensland and Tasmania. In Victoria, New South Wales and Southeast Queensland, state-owned utilities provide bulk water which is then distributed by utilities owned by either local or state governments. The Minister for Sustainability, Environment, Water, Population and Communities is responsible for water policies at the federal level.Water supply and sanitation in Israel
Water supply and sanitation in Israel are intricately linked to the historical development of Israel. Because rain falls only in the winter, and largely in the northern part of the country, irrigation and water engineering are considered vital to the country's economic survival and growth. Large scale projects to desalinate seawater, direct water from rivers and reservoirs in the north, make optimal use of groundwater, and reclaim flood overflow and sewage have been undertaken. Among them is the National Water Carrier, carrying water from the country's biggest freshwater lake, the Sea of Galilee, to the northern Negev desert through channels, pipes and tunnels. Israel's water demand today outstrips available conventional water resources. Thus, in an average year, Israel relies for about half of its water supply on unconventional water resources, including reclaimed water and desalination. A particularly long drought in 1998–2002 had prompted the government to promote large-scale seawater desalination.Water supply and sanitation in Saudi Arabia
Water supply and sanitation in Saudi Arabia is characterized by challenges and achievements. One of the main challenges is water scarcity. In order to overcome water scarcity, substantial investments have been undertaken in seawater desalination, water distribution, sewerage and wastewater treatment. Today about 50% of drinking water comes from desalination, 40% from the mining of non-renewable groundwater and only 10% from surface water in the mountainous southwest of the country. The capital Riyadh, located in the heart of the country, is supplied with desalinated water pumped from the Persian Gulf over a distance of 467 km. Water is provided almost for free to residential users. Despite improvements, service quality remains poor, for example in terms of continuity of supply. Another challenge is weak institutional capacity and governance, reflecting general characteristics of the public sector in Saudi Arabia. Among the achievements is a significant increase in desalination, and in access to water, the expansion of wastewater treatment, as well as the use of treated effluent for the irrigation of urban green spaces, and for agriculture.
Since 2000, the government has increasingly relied on the private sector to operate water and sanitation infrastructure, beginning with desalination and wastewater treatment plants. Since the creation of the National Water Company (NWC) in 2008, the operation of urban water distribution systems in the four largest cities has gradually been delegated to private companies as well. The apparent paradox of very low water tariffs and water privatization is explained by government subsidies. The government buys desalinated water from private operators at high prices and resells the bulk water for free. Likewise, the government directly pays private operators that run the water distribution and sewer systems of large cities under management contracts. Furthermore, it fully subsidizes investments in water distribution and sewers. Water utilities are expected to recover an increasing share of their costs from the sale of treated effluent to industries. In January 2016 water and sewer tariffs were increased for the first time in more than a decade, which resulted in discontent and in the sacking of the Minister of Water and Energy Abdullah Al-Hussayen in April 2016.Water supply and sanitation in Singapore
Water supply and sanitation in Singapore is characterised by a number of achievements in the challenging environment of a densely populated island. Access to water is universal, affordable, efficient and of high quality. Innovative integrated water management approaches such as the reuse of reclaimed water, the establishment of protected areas in urban rainwater catchments and the use of estuaries as freshwater reservoirs have been introduced along with seawater desalination in order to reduce the country's dependence on water imported from neighbouring country, Malaysia.
Singapore's approach does not rely only on physical infrastructure, but it also emphasizes proper legislation and enforcement, water pricing, public education as well as research and development. In 2007 Singapore's water and sanitation utility, the Public Utilities Board, received the Stockholm Industry Water Award for its holistic approach to water resources management.