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Water desalination
Methods

Desalination, desalinization, or desalinisation refers to any of several processes that remove excess salt and other minerals from water. More generally, desalination may also refer to the removal of salts and minerals,[1] as in soil desalination.[2][3]

Water is desalinated in order to convert salt water to fresh water so it is suitable for human consumption or irrigation. Sometimes the process produces table salt as a by-product. It 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 in regions where the availability of fresh water is limited.

Large-scale desalination typically uses extremely large amounts of energy as well as specialized, expensive infrastructure, making it very costly compared to the use of fresh water from rivers or groundwater. The large energy reserves of many Middle Eastern countries, along with their relative water scarcity, have led to extensive construction of desalination in this region. By mid-2007, Middle Eastern desalination accounted for close to 75% of total world capacity.[4]

The world's largest desalination plant is the Jebel Ali Desalination Plant (Phase 2) in the United Arab Emirates. It is a dual-purpose facility that uses multi-stage flash distillation and is capable of producing 300 million cubic meters of water per year. By comparison the largest desalination plant in the United States is located in Tampa Bay, Florida, which began desalinating 25 million gallons (US Gal.) (95000 m³) of water per day in December 2007.[5] The Tampa Bay plant runs at around 12% the output of the Jebel Ali Desalination Plants. A January 17, 2008, article in the Wall Street Journal states, "World-wide, 13,080 desalination plants produce more than 12 billion gallons of water a day, according to the International Desalination Association."[6]

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

Contents

Methods

As of July 2004, the leading method is multi-stage flash distillation (85% of production worldwide).[7] The traditional process used in these operations is vacuum distillation—essentially the boiling of water at less than atmospheric pressure and thus a much lower temperature than normal. This is because the boiling of a liquid occurs when the vapor pressure equals the ambient pressure and vapor pressure increases with temperature. Thus, because of the reduced temperature, energy is saved.

In the last decade, membrane processes have developed very quickly, and most new facilities use reverse osmosis technology.[citation needed] Membrane processes use semi-permeable membranes and pressure to separate salts from water.[citation needed] 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.[citation needed]

Considerations and criticism

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Cogeneration

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

Shevchenko BN350, a nuclear-heated desalination unit

In a December 26, 2007, opinion column in the The Atlanta Journal-Constitution, Nolan Hertel, a professor of nuclear and radiological engineering at Georgia Tech, wrote, "... nuclear reactors can be used ... to produce large amounts of potable water. The process is already in use in a number of places around the world, from India to Japan and Russia. Eight nuclear reactors coupled to desalination plants are operating in Japan alone ... nuclear desalination plants could be a source of large amounts of potable water transported by pipelines hundreds of miles inland..."[10][11]

Additionally, the current trend in dual-purpose facilities is hybrid configurations, in which the permeate from an RO 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 Yambu-Medina.[12]

A typical aircraft carrier in the U.S. military uses nuclear power to desalinate 400,000 gallons (US Gal.) or 1514 m³ of water per day.[13]

Economics

A number of factors determine the capital and operating costs for desalination: 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 the water extraction efficiency. Nuclear-powered desalination might be economical on a large scale.[14]

But, critics will point to the high costs of desalination technologies, especially for developing countries, the impracticability and cost of transporting or piping massive amounts of desalinated seawater throughout the interiors of large countries, and the byproduct of concentrated seawater, which some environmentalists have claimed "is a major cause of marine pollution when dumped back into the oceans at high temperatures"[15]

While noting that costs are falling, and generally positive about the technology for affluent areas that are proximate to oceans, one study argues that "Desalinated water may be a solution for some water-stress regions, but not for places that are poor, deep in the interior of a continent, or at high elevation. Unfortunately, that includes some of the places with biggest water problems." and "Indeed, one needs to lift the water by 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, 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."[16] After being desalinized at Jubail, Saudi Arabia, water is pumped 200 miles (320 km) inland through a pipeline to the capital city of Riyadh.[17] For cities on the coast, desalination is being increasingly viewed as an untapped and unlimited water source.

Nevertheless, desalination does not take into account recycling water and broken infrastructure.[citation needed] Water is reused in Fountain Valley, CA, Fairfax, VA, El Paso, TX and Scottsdale, AZ. This process is an alternative to desalination that requires 50% less energy due to the significantly lower salt content and produces new water at 30% less cost to the consumer than desalinated sea water without the damage to marine life and ecosystems common to desalination plants.[citation needed]

Israel is now desalinating water at a cost of US$0.53 per cubic meter.[18] Singapore is desalinating water for US$0.49 per cubic meter.[19] Many large coastal cities in developed countries are considering the feasibility of seawater desalination, due to its cost effectiveness compared with other water supply options, which can include mandatory installation of rainwater tanks or stormwater harvesting infrastructure. Studies[citation needed] have shown that the desalination option is more cost-effective than large-scale recycled water for drinking, and more cost-effective in Sydney than the vastly expensive option of mandatory installation of rainwater tanks or stormwater harvesting infrastructure. The city of Perth has been successfully [20] operating a reverse osmosis seawater desalination plant since 2006, and the Western Australian government have announced that a second plant will be built to serve the city's needs. A desalination plant is being built in Australia's largest city, Sydney, and at Wonthaggi, Victoria, in the near future.[21]

The Perth desalination plant is powered partially by renewable energy from the Emu Downs Wind Farm[22]. The Sydney plant will be powered entirely from renewable sources[23], thereby eliminating harmful greenhouse gas emissions to the environment, a common argument used against seawater desalination due to the energy requirements of the technology. The purchase or production of renewable energy to power desalination plants naturally adds to the capital and/or operating costs of desalination. However, recent experience in Perth and Sydney indicates that the additional cost is acceptable to communities, as a city may then augment its water supply without doing environmental harm to the atmosphere. The Queensland state government recently announced that the Gold Coast desalination plant will be powered entirely from renewable sources, bringing its environmental footprint down, in line with the other major plants that will be operating around the same time, in Perth and Sydney.

In December 2007, the South Australian government announced that it would build a seawater desalination plant for the city of Adelaide, Australia, located at Port Stanvac. The desalination plant is to be funded by raising water rates to achieve full cost recovery. [2] [3] An online, unscientific poll showed that nearly 60% of votes cast were in favor of raising water rates to pay for desalination. [4]

A January 17, 2008, article in the Wall Street Journal states, "In November, Connecticut-based Poseidon Resources Corp. won a key regulatory approval to build the US$300 million water-desalination plant in Carlsbad, north of San Diego. The facility would be the largest in the Western Hemisphere, producing 50 million [U.S.] gallons [190,000 m³] of drinking water a day, enough to supply about 100,000 homes ... Improved technology has cut the cost of desalination in half in the past decade, making it more competitive ... Poseidon plans to sell the water for about US$950 per acre-foot [1200 m³]. That compares with an average US$700 an acre-foot [1200 m³] that local agencies now pay for water." [5] $1,000 per acre-foot works out to $3.06 for 1,000 gallons, which is the unit of water measurement that residential water users are accustomed to being billed in. [6].

While this regulatory hurdle was met, Poseidon Resources is not able to break ground until the final approval of a mitigation project for the damage done to marine life through the intake pipe, as is required by California law. Poseidon Resources has made progress in Carlsbad, CA, despite its 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 were 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 due to marine life and growth captured and stuck to reverse osmosis filters prior to fully utilizing this facility in 2007.[24]

According to a May 9, 2008, article in Forbes, a San Leandro, California, company called Energy Recovery Inc. has been desalinating water for US$0.46 per cubic meter.[25]

According to a June 5, 2008, article in the Globe and Mail, a Jordanian-born chemical engineering doctoral student at the University of Ottawa, named Mohammed Rasool Qtaisha, has invented a new desalination technology that is alleged to be between 600% and 700% more efficient than current technology. According to the article, General Electric is looking into similar technology, and the U.S. National Science Foundation announced a grant to the University of Michigan to study it as well. Because the patents were still being worked out, the article was very vague about the details of this alleged technology.[26]

Environmental

One of the main environmental considerations of ocean water desalination plants is the impact of the open ocean water intakes[citation needed], especially when co-located with power plants. Many proposed ocean desalination plants' initial plans relied on these intakes despite perpetuating ongoing impacts on marine life[citation needed]. In the United States, due to a recent court ruling under the Clean Water Act, these intakes are no longer viable without reducing mortality, by ninety percent, of the life in the ocean; the plankton, fish eggs and fish larvae.[27] There are alternatives, including beach wells that eliminate this concern, but require more energy and higher costs while limiting output.[28] Other environmental concerns include air pollution and greenhouse gas emissions from the power plants that provide electricity and/or thermal energy to the desalination plants.

Regardless of the method used, there is always a highly concentrated waste product consisting of everything that was removed from the created fresh water. This is sometimes referred to as brine, which is also a common term for the byproduct of recycled water schemes that is often disposed of in the ocean. These concentrates are classified by the United States Environmental Protection Agency as industrial wastes. With coastal facilities, it may be possible to return it to the sea without harm if this concentrate does not exceed the normal ocean salinity gradients to which osmoregulators are accustomed. Reverse osmosis, for instance, may require the disposal of waste water with salinity twice that of normal seawater. The benthic community cannot accommodate such an extreme change in salinity and many filter-feeding animals are destroyed by osmotic pressure when such water is returned to the ocean. This presents an increasing problem further inland where one needs to avoid ruining existing fresh water supplies such as ponds, rivers and aquifers. As such, proper disposal of concentrate needs to be investigated during the design phases.

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 waste water treatment plant or power plant. While seawater power plant cooling water outfalls are not freshwater like waste water treatment plant outfalls, the salinity of the brine will still be reduced. If the power plant is medium- to large-sized and the desalination plant is not enormous, the flow of the power plant's cooling water 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 spread the brine over a very large area so that there is only a slight increase in salinity. For example, once the pipeline containing the brine reaches the sea floor, it can split off into many branches, each one releasing the brine gradually along its length through small holes. This method can be used in combination with the joining of the brine with power plant or waste water plant outfalls.

The concentrated seawater has the potential to harm ecosystems, especially marine environments in regions with low turbidity and high evaporation that already have elevated salinity. Examples of such locations are the Persian Gulf, the Red Sea and, in particular, coral lagoons of atolls and other tropical islands around the world[citation needed]. Because the brine is denser than the surrounding sea water due to the higher solute concentration, discharge into water bodies means that the ecosystems on the bed of the water body are most at risk because the brine sinks and remains there long enough to damage the ecosystems. Careful re-introduction can minimize this problem[citation needed]. For example, for the desalination plant and ocean outlet structures to be built in Sydney from late 2007, the water authority states that the ocean outlets will be placed in locations at the seabed that will maximize the dispersal of the concentrated seawater, such that it will be indistinguishable from normal seawater between 50 meters and 75 meters from the outlet points. Sydney is fortunate to have typical oceanographic conditions off the coast that allow for such rapid dilution of the concentrated byproduct, thereby minimizing harm to the environment.

In Perth, Australia, in 2007, the Kwinana Desalination Plant was opened. The water is sucked in from the ocean at only 0.1 meter per second, which is slow enough to let fish escape. The plant provides nearly 140,000 m³ of clean water per day. [7]

Desalination compared to other waters supply options

Increased water conservation and water use efficiency remain the most cost-effective priority for supplying water for certain areas of the world where there is a large potential to improve the efficiency of water use practices.[29] While comparing ocean water desalination to waste water reclamation for drinking water shows desalination as the first option, using reclamation for irrigation and industrial use provides multiple benefits.[30] Urban runoff and storm water capture also provide multiple benefits in treating, restoring and recharging groundwater.[31] An emerging alternative to desalinization in the state of California and other areas in the American Southwest is the commercial importation of bulk water either by very large crude carriers converted to water carriers or pipelines. The idea is presently politically unpopular in Canada, where governments have been scrambling to impose 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. Sun Belt maintains a web site where documents relating to their dispute are posted online here.

Experimental techniques and other developments

In the past, many novel desalination techniques have been researched with varying degrees of success. Some, such as forward osmosis, are still on the drawing board now while others have attracted research funding. For example, to offset the energy requirements of desalination, the U.S. government is working to develop practical solar desalination.

As an example of newer theoretical approaches for desalination, focusing specifically on maximizing energy efficiency and cost effectiveness, the Passarell Processmay be considered[citation needed].

Other approaches involve the use of geothermal energy. From an environmental and economic point of view, in most locations geothermal desalination can be preferable to using fossil groundwater or surface water for human needs, as in many regions the available surface and groundwater resources already have long been under severe stress.

Recent research in the U.S. indicates that nanotube membranes may prove to be extremely effective for water filtration and may produce a viable water desalination process that would require substantially less energy than reverse osmosis.[32]

On June 23, 2008, it was reported that Siemens Water Technologies had developed a new technology, based on applying electric field on seawater, that desalinates one cubic meter of water while using only 1.5 kWh of energy, which, according to the report, is one half the energy that other processes use.[33]

Fresh water can also be produced by freezing seawater, as happens naturally in the polar regions, and is known as freeze-thaw desalination.

According to MSNBC, a report by Lux Research estimated that the worldwide desalinated water supply will triple between 2008 and 2020.[34]

Low Temperature Thermal Desalination

Low Temperature Thermal Desalination (LTTD) uses low pressures inside chambers created by vacuum pumps and the principle that water boils at low pressures, even at ambient temperature. To cool the water vapors, cold sea water located 600 metres below the sea level is pumped through coils to condense the water vapors and then collect the pure water into storage tanks. The temperature of ocean water declines with an increase in depth, the water on the surface of sea water is hot and water below 600 metres is much cooler. It is also possible to use the LTTD process for power plants where huge amounts of warm water are discharged continuously from the plant.

The technology was developed by India's National Institute of Ocean Technology (NIOT) and the world's first LTTD plant was opened in the Lakshadweep islands in 2005. The plant has a 100,000 liters/day capacity.[35] In 2007, NIOT successfully opened a floating LTTD plant off the coast of Chennai with a capacity of 1 million liters/day and is currently constructing a similar plant with a capacity of 10 million liters/day.[36][37]

Thermo-ionic 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 empties all the sodium and chlorine ions from the water.[38][39]

Existing facilities and facilities under construction

Aruba

The island of Aruba has a large (world second largest at the time of its inauguration) desalination plant with the total installed capacity of 42000 metric tons (11.1 million gallons) per day[40].

Australia

A combination of increased water usage and lower rainfall in Australia has caused State governments to build a number of desalination plants, including the recently commissioned Kurnell Desalination Plant serving the Sydney area.

El Paso (Texas) Desalination Plant

Brackish groundwater has been treated at the El Paso plant since around 2004. Producing 27.5 million gallons (104,000 m³) of fresh water daily (about 25% of total freshwater deliveries) by reverse osmosis, it is a crucial contribution to water supplies in this water-stressed city.[41]

Israel

The Hadera seawater reverse osmosis (SWRO) desalination plant in Israel is the largest in the world.[42][43] The project was developed as a BOT (Build-Operate-Transfer) by a consortium of three international companies: Veolia water, IDE Technologies and Elran.[44]

Existing Israeli water desalination facilities[45]
Location Opening Capacity
(mln m3/year)
Capacity
(mln gallons/day)
Capacity
(megaliters)
Cost of water (per m3) Notes
Ashkelon August 2005 111 (as of 2008) 83.2 315 NIS 2.60 [43]
Palmachim May 2007 30 (expansion to 45 planned [46]) 32.6 123.4 NIS 2.90 [47]
Hadera December 2009 127 91.9 349 NIS 2.60 [48]
Israeli water desalination facilities under construction
Location Opening Capacity
(mln m3/year)
Cost of water (per m3) Notes
Ashdod 2012 100 (expansion to up to 150 possible) NIS 2.70 [49]
Soreq 2012 150 NIS 2.01 - 2.19 [50]

Tampa Bay Water Desalination Project

The Tampa Bay Water Desalination project was originally a private venture led by Poseidon Resources. This project was delayed by the bankruptcy of Poseidon Resources' successive partners in the venture, Stone & Webster, then Covanta (formerly Ogden) and its principal subcontractor Hydranautics. Poseidon's relationship with Stone & Webster through S & W Water LLC ended in June 2000 when Stone & Webster declared bankruptcy and Poseidon Resources purchased Stone & Webster's stake in S & W Water LLC. Poseidon Resources partnered with Covanta and Hydranautics in 2001, changing the consortium name to Tampa Bay Desal. Through the inability of Covanta to complete construction bonding of the project, the Tampa Bay Water agency was forced to purchase the project from Poseidon on May 15, 2002, and underwrite the project financing under its own credit rating. Tampa Bay Water then contracted with Covanta Tampa Construction, which produced a project that did not meet required performance tests, and Covanta Tampa Construction filed bankruptcy in October 2003 to prevent losing the contract with Tampa Bay Water, which resulted in nearly six months of litigation between Covanta Tampa Construction and Tampa Bay Water. The plant was not fully operational until 2007[24]. The plant currently runs at the capacity of 25 million gallons per day[51].

Trinidad and Tobago

The Republic of Trinidad and Tobago is using desalination to free up more of the island's water supply for drinking purposes. The desalination facility, opened in March 2003, is considered to be the first of its kind. It is the largest desalination facility in the Americas and will process 28.8 million gallons of water a day and sell water at the price of $2.67 per 1,000 gallons[52]. This facility will be located at Trinidad's Point Lisas Industrial Estate, a park of more than 12 companies in various manufacturing and processing functions and will allow for easy access to water for both factories and residents in the country[53].

See also

References

Notes

  1. ^ "Desalination" (definition), The American Heritage Science Dictionary, Houghton Mifflin Company, via dictionary.com. Retrieved on 2007-08-19.
  2. ^ "Australia Aids China In Water Management Project." People's Daily Online, 2001-08-03, via english.people.com.cn. Retrieved on 2007-08-19.
  3. ^ There exist a new solution with the HelioTech products. HelioTech company ltd. Takashi, Kume, Amaya Takao, and Mitsuno Tooru. "The Effect of Soil Desalinization in the Hetao Irrigation District, Inner Mongolia, China." Transactions of the Japanese Society of Irrigation, Drainage and Reclamation Engineering, No. 223, pp. 133-139, 2003, abstract via sciencelinks.jp. Retrieved on 2007-08-19.
  4. ^ Fischetti, Mark (September 2007), "Fresh from the Sea", Scientific American (Scientific American, Inc.) 297 (3): 118–119, http://www.sciam.com/article.cfm?id=fresh-from-the-sea, retrieved 2008-08-03  Note: only the first two paragraphs are available on-line for no charge.
  5. ^ Applause, At Last, For Desalination Plant, The Tampa Tribune, December 22, 2007
  6. ^ Kathryn Kranhold, Water, Water, Everywhere..., The Wall Street Journal, January 17, 2008
  7. ^ Source: water-technology.net
  8. ^ Hamed, Osman A. (2005). “Overview of hybrid desalination systems – current status and future prospects.” Desalination, 186, 207-214.
  9. ^ Misra, B.M., J. Kupitz. (2004). “The role of nuclear desalination in meeting potable water needs in water scarce areas in the next decades.” Desalination, 166, 1-9.
  10. ^ http://gift.kisti.re.kr/GTB/infoboard/download.jsp?down_url=data/file/GTB/shleegift/shleegift_1198793876096.doc&cn=GTB2007120672
  11. ^ Nuclear Desalination. Retrieved on 2010-01-07
  12. ^ Ludwig, Heinz. (2004). “Hybrid systems in seawater desalination – practical design aspects, present status and development perspectives.” Desalination, 164, 1-18.
  13. ^ How Aircraft Carriers Work
  14. ^ "Nuclear Desalination". World Nuclear Association. January 2010. http://www.world-nuclear.org/info/inf71.html. Retrieved 2010-02-01. 
  15. ^ Barlow, Maude, and Tony Clarke, "Who Owns Water?" The Nation, 2002-09-02, via thenation.com. Retrieved on 2007-08-20.
  16. ^ Zhoua, Yuan, and Richard S.J. Tolb. "Evaluating the costs of desalination and water transport." (Working paper). Via a Hamburg University website. 2004-12-09. Retrieved on 2007-08-20.
  17. ^ Desalination is the Solution to Water Shortages, redOrbit, May 2, 2008
  18. ^ Sitbon, Shirli. "French-run water plant launched in Israel," European Jewish Press, via ejpress.org, 2005-12-28. Retrieved on 2007-08-20.
  19. ^ "Black & Veatch-Designed Desalination Plant Wins Global Water Distinction," (Press release). Black & Veatch Ltd., via edie.net, 2006-05-04. Retrieved on 2007-08-20.
  20. ^ http://www.water-technology.net/projects/perth/
  21. ^ "Sydney desalination plant to double in size," ABC News (Australian Broadcasting Corporation), via abc.net.au, 2007-06-25. Retrieved on 2007-08-20.
  22. ^ Australia Turns to Desalination by Michael Sullivan and PX Pressure Exchanger energy recovery devices from Energy Recovery Inc. An Environmentally Green Plant Design. Morning Edition, National Public Radio, June 18, 2007
  23. ^ Fact sheets
  24. ^ a b http://www.tampabaywater.org/watersupply/tbdesalhistory.aspx
  25. ^ Hydro-Alchemy, Forbes, May 9, 2008
  26. ^ Ottawa student may hold secret to Water For All, Globe and Mail, June 5, 2008
  27. ^ http://www.desalresponsegroup.org/files/RiverkeepervEPA1-25-07_decision.pdf
  28. ^ untitled
  29. ^ Gleick, Peter H., Dana Haasz, Christine Henges-Jeck, Veena Srinivasan, Gary Wolff, Katherine Kao Cushing, and Amardip Mann. (November 2003.) "Waste not, want not: The potential for urban water conservation in California." (Website). Pacific Institute. Retrieved on 2007-09-20.
  30. ^ Cooley, Heather, Peter H. Gleick, and Gary Wolff. (June 2006.) "Desalination, With a Grain of Salt – A California Perspective." (Website). Pacific Institute. Retrieved on 2007-09-20.
  31. ^ Gleick, Peter H., Heather Cooley, David Groves. (September 2005.) "California water 2030: An efficient future." (Website). Pacific Institute. Retrieved on 2007-09-20.
  32. ^ Lawrence Livermore National Laboratory Public Affairs (2006-05-18). "Nanotube membranes offer possibility of cheaper desalination". Press release. http://www.llnl.gov/pao/news/news_releases/2006/NR-06-05-06.html. Retrieved 2007-09-07. 
  33. ^ Team wins $4m grant for breakthrough technology in seawater desalination, The Straits Times, June 23, 2008
  34. ^ A Rising Tide for New Desalinated Water Technologies, MSNBC, March. 17, 2009
  35. ^ Desalination: India opens world’s first low temperature thermal desalination plant
  36. ^ Floating plant, India
  37. ^ Mobile Desalination plant, India
  38. ^ Current thinking, Oct 29th 2009, The Economist
  39. ^ Saltworks Technologies
  40. ^ W.E.B. Aruba N.V. - Water Plant
  41. ^ http://www.epwu.org/water/desal_info.html
  42. ^ Israel is No. 5 on Top 10 Cleantech List in Israel 21c A Focus Beyond Retrieved 2009-12-21
  43. ^ a b Ashkelon Desalination Plant Seawater Reverse Osmosis (SWRO) Plant
  44. ^ Ashkelon desalination plant — A successful challenge
  45. ^ Public-Private Partnership Projects, Accountant General, Ministry of Finance
  46. ^ "Israel: Finance secured for Palmachim desalination expansion"
  47. ^ [1] "Israel's Desalination Industry"
  48. ^ "Funding agreed for expanding Hadera desalination plant"
  49. ^ "Spanish/Israeli JV awarded Ashdod desalination contract"
  50. ^ "IDE reported winner of Soreq desalination contract"
  51. ^ http://www.tampabaywater.org/facilities/desalination_plant/index.aspx
  52. ^ Cite error: Invalid <ref> tag; no text was provided for refs named http:.2F.2Fwww.bizjournals.com.2Fboston.2Fstories.2F1999.2F10.2F04.2Fstory7.html; see Help:Cite error.
  53. ^ Cite error: Invalid <ref> tag; no text was provided for refs named http:.2F.2Fwww.waterindustry.org.2FNew.2520Projects.2Fionics-2.htm; see Help:Cite error.

Further reading

Ariticles

External links


Water desalination
Methods

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

Water is desalinated in order to convert salt water to fresh water so it is suitable for human consumption or irrigation. Sometimes the process produces table salt as a by-product. It 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 in regions where the availability of fresh water is, or is becoming, limited.

Large-scale desalination typically uses extremely large amounts of energy as well as specialized, expensive infrastructure, making it very costly compared to the use of fresh water from rivers or groundwater.[3]

The world's largest desalination plant is the Jebel Ali Desalination Plant (Phase 2) in the United Arab Emirates. It is a dual-purpose facility that uses multi-stage flash distillation and is capable of producing 300 million cubic metres of water per year. By comparison the largest desalination plant in the United States is located in Tampa Bay, Florida and operated by Tampa Bay Water, which began desalinating 34.7 million cubic meters of water per year in December 2007.[4] The Tampa Bay plant runs at around 12% the output of the Jebel Ali Desalination Plants. A January 17, 2008, article in the Wall Street Journal states, "World-wide, 13,080 desalination plants produce more than 12 billion gallons of water a day, according to the International Desalination Association."[5]

[[File:|thumb|right|350px|Schematic of a multi-stage flash desalinator
A - Steam in
B - Seawater in
C - Potable water out
D - Waste out
E - Steam out
F - Heat exchange
G - Condensation collection
H - Brine heater]] [[File:|thumb|right|350px|Plan of a typical reverse osmosis desalination plant]]

Contents

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, energy is saved. A leading distillation method is multi-stage flash distillation accounting for 85% of production worldwide in 2004.[6] [[File:|thumb|Reverse osmosis desalination plant in Barcelona, Spain]] The principal competing processes use membranes to desalinate, principally applying reverse osmosis technology.[citation needed] Membrane processes use semi-permeable membranes and pressure to separate salts from water.[citation needed] 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.[citation needed]

Considerations and criticism

Cogeneration

Cogeneration is the process of using excess heat from power production to accomplish another task. In the sense of desalination, cogeneration is the production of potable water from seawater or brackish groundwater in an integrated, or "dual-purpose", facility in which a power plant is used as the source of energy for the desalination process. The facility’s energy production may be dedicated entirely to the production of potable water (a stand-alone facility), or excess energy may be produced and incorporated into the energy grid (a true cogeneration facility). There are various forms of cogeneration, and theoretically any form of energy production could be used. However, the majority of current and planned cogeneration desalination plants use either fossil fuels or nuclear power as their source of energy. Most plants are located in the Middle East or North Africa, due to their petroleum resources and subsidies. The advantage of dual-purpose facilities is that they can be more efficient in energy consumption, thus making desalination a more viable option for drinking water in areas of scarce water resources.[7][8]

File:Shevchenko BN350
Shevchenko BN350, a nuclear-heated desalination unit

In a December 26, 2007, opinion column in the The Atlanta Journal-Constitution, Nolan Hertel, a professor of nuclear and radiological engineering at Georgia Tech, wrote, "... nuclear reactors can be used ... to produce large amounts of potable water. The process is already in use in a number of places around the world, from India to Japan and Russia. Eight nuclear reactors coupled to desalination plants are operating in Japan alone ... nuclear desalination plants could be a source of large amounts of potable water transported by pipelines hundreds of miles inland..."[9][10]

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

A typical aircraft carrier in the U.S. military uses nuclear power to desalinate 400,000 gallons (US Gal.) or 1514 m³ of water per day.[12]

Economics

A number of factors determine the capital and operating costs for desalination: 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 the water extraction efficiency. Nuclear-powered desalination might be economical on a large scale.[13][14]

While noting that costs are falling, and generally positive about the technology for affluent areas that are proximate to oceans, one study argues that "Desalinated water may be a solution for some water-stress regions, but not for places that are poor, deep in the interior of a continent, or at high elevation. Unfortunately, that includes some of the places with biggest water problems." and "Indeed, one needs to lift the water by 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, high transport costs would add to the high desalination costs. Desalinated water is also expensive in places that are both somewhat far from the sea and somewhat high, such as Riyadh and Harare. In many places, the dominant cost is desalination, not transport; the process would therefore be relatively less expensive in places like Beijing, Bangkok, Zaragoza, Phoenix, and, of course, coastal cities like Tripoli."[15] After being desalinated at Jubail, Saudi Arabia, water is pumped 200 miles (320 km) inland through a pipeline to the capital city of Riyadh.[16] For cities on the coast, desalination is being increasingly viewed as an untapped and unlimited water source.

Nevertheless, desalination does not take into account recycling water and broken infrastructure.[citation needed] Water is reused in Fountain Valley, CA, Fairfax, VA, El Paso, TX and Scottsdale, AZ. This process is an alternative to desalination that requires 50% less energy due to the significantly lower salt content and produces new water at 30% less cost to the consumer than desalinated sea water without the damage to marine life and ecosystems common to desalination plants.[citation needed]

Israel is now desalinating water at a cost of US$0.53 per cubic meter.[17] Singapore is desalinating water for US$0.49 per cubic meter.[18] Many large coastal cities in developed countries are considering the feasibility of seawater desalination, due to its cost effectiveness compared with other water supply options, which can include mandatory installation of rainwater tanks or stormwater harvesting infrastructure. Studies[citation needed] have shown that the desalination option is more cost-effective than large-scale recycled water for drinking, and more cost-effective in Sydney than the vastly expensive option of mandatory installation of rainwater tanks or stormwater harvesting infrastructure. The city of Perth has been successfully [19] operating a reverse osmosis seawater desalination plant since 2006, and the Western Australian government have announced that a second plant will be built to serve the city's needs. A desalination plant is being built in Australia's largest city of Sydney,[20] and the Wonthaggi desalination plant is a proposed facility in Wonthaggi, Victoria.

The Perth desalination plant is powered partially by renewable energy from the Emu Downs Wind Farm.[21] The Sydney plant will be powered entirely from renewable sources,[22] thereby eliminating harmful greenhouse gas emissions to the environment, a common argument used against seawater desalination due to the energy requirements of the technology. The purchase or production of renewable energy to power desalination plants naturally adds to the capital and/or operating costs of desalination. However, recent experience in Perth and Sydney indicates that the additional cost is acceptable to communities, as a city may then augment its water supply without doing environmental harm to the atmosphere. The Queensland state government recently announced that the Gold Coast desalination plant will be powered entirely from renewable sources, bringing its environmental footprint down, in line with the other major plants that will be operating around the same time, in Perth and Sydney.

In December 2007, the South Australian government announced that it would build a seawater desalination plant for the city of Adelaide, Australia, located at Port Stanvac. The desalination plant is to be funded by raising water rates to achieve full cost recovery. [3] [4] An online, unscientific poll showed that nearly 60% of votes cast were in favor of raising water rates to pay for desalination. [5]

A January 17, 2008, article in the Wall Street Journal states, "In November, Connecticut-based Poseidon Resources Corp. won a key regulatory approval to build the US$300 million water-desalination plant in Carlsbad, north of San Diego. The facility would be the largest in the Western Hemisphere, producing 50 million [U.S.] gallons [190,000 m³] of drinking water a day, enough to supply about 100,000 homes ... Improved technology has cut the cost of desalination in half in the past decade, making it more competitive ... Poseidon plans to sell the water for about US$950 per acre-foot [1200 m³]. That compares with an average US$700 an acre-foot [1200 m³] that local agencies now pay for water." [6] $1,000 per acre-foot works out to $3.06 for 1,000 gallons, which is the unit of water measurement that residential water users are accustomed to being billed in. [7].

While this regulatory hurdle was met, Poseidon Resources is not able to break ground until the final approval of a mitigation project for the damage done to marine life through the intake pipe, as is required by California law. Poseidon Resources has made progress in Carlsbad, CA, despite its 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 were 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 due to marine life and growth captured and stuck to reverse osmosis filters prior to fully utilizing this facility in 2007.[23]

According to a May 9, 2008, article in Forbes, a San Leandro, California, company called Energy Recovery Inc. has been desalinating water for US$0.46 per cubic meter.[24]

According to a June 5, 2008, article in the Globe and Mail, a Jordanian-born chemical engineering doctoral student at the University of Ottawa, named Mohammed Rasool Qtaisha, has invented a new desalination technology that is alleged to be between 600% and 700% more water output per square meter of membrane than current technology. According to the article, General Electric is looking into similar technology, and the U.S. National Science Foundation announced a grant to the University of Michigan to study it as well. Because the patents were still being worked out, the article was very vague about the details of this alleged technology.[25]

While desalinating 1,000 gallons of water can cost as much as $3, the same amount of bottled water costs $7,945.[26]

Environmental

One of the main environmental considerations of ocean water desalination plants is the impact of the open ocean water intakes[citation needed], especially when co-located with power plants. Many proposed ocean desalination plants' initial plans relied on these intakes despite perpetuating ongoing impacts on marine life[citation needed]. In the United States, due to a recent court ruling under the Clean Water Act, these intakes are no longer viable without reducing mortality, by ninety percent, of the life in the ocean; the plankton, fish eggs and fish larvae.[27] There are alternatives, including beach wells that eliminate this concern, but require more energy and higher costs while limiting output.[28] Other environmental concerns include air pollution and greenhouse gas emissions from the power 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 waste water treatment plant or power plant. While seawater power plant cooling water outfalls are not freshwater like waste water treatment plant outfalls, the salinity of the brine will still be reduced. If the power plant is medium- to large-sized and the desalination plant is not enormous, the flow of the power plant's cooling water 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 spread the brine over a very large area so that there is only a slight increase in salinity. For example, once the pipeline containing the brine reaches the sea floor, it can split off into many branches, each one releasing the brine gradually along its length through small holes. This method can be used in combination with the joining of the brine with power plant or waste water plant outfalls.

The concentrated seawater has the potential to harm ecosystems, especially marine environments in regions with low turbidity and high evaporation that already have elevated salinity. Examples of such locations are the Persian Gulf, the Red Sea and, in particular, coral lagoons of atolls and other tropical islands around the world[citation needed]. Because the brine is denser than the surrounding sea water due to the higher solute concentration, discharge into water bodies means that the ecosystems on the bed of the water body are most at risk because the brine sinks and remains there long enough to damage the ecosystems. Careful re-introduction can minimize this problem[citation needed]. For example, for the desalination plant and ocean outlet structures to be built in Sydney from late 2007, the water authority states that the ocean outlets will be placed in locations at the seabed that will maximize the dispersal of the concentrated seawater, such that it will be indistinguishable from normal seawater between 50 meters and 75 meters from the outlet points. Sydney is fortunate to have typical oceanographic conditions off the coast that allow for such rapid dilution of the concentrated byproduct, thereby minimizing harm to the environment.

In Perth, Australia, in 2007, the Kwinana Desalination Plant was opened. The water is sucked in from the ocean at only 0.1 meter per second, which is slow enough to let fish escape. The plant provides nearly 140,000 m³ of clean water per day. [8]

Desalination compared to other water supply options

Increased water conservation and water use 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.[29] While comparing ocean water desalination to waste water reclamation for drinking water shows desalination as the first option, using reclamation for irrigation and industrial use provides multiple benefits.[30] Urban runoff and storm water capture also provide benefits in treating, restoring and recharging groundwater.[31] A proposed alternative to desalinization in the state of California and other areas in the American Southwest is the commercial importation of bulk water either by very large crude carriers converted to water carriers, or via pipelines. The idea is politically unpopular in Canada, where governments have been scrambling to impose 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. Sun Belt maintains a web site where documents relating to their dispute are posted online.[32]

Experimental techniques and other developments

In the past, many novel desalination techniques have been researched with varying degrees of success. Some, such as forward osmosis, are still on the drawing board now while others have attracted research funding. For example, to offset the energy requirements of desalination, the U.S. government is working to develop practical solar desalination.

As an example of newer theoretical approaches for desalination, focusing specifically on maximizing energy efficiency and cost effectiveness, the Passarell Process may be considered[citation needed].

Other approaches involve the use of geothermal energy. From an environmental and economic point of view, in most locations geothermal desalination can be preferable to using fossil groundwater or surface water for human needs, as in many regions the available surface and groundwater resources already have long been under severe stress.

Recent research in the U.S. indicates that nanotube membranes may prove to be extremely effective for water filtration and may produce a viable water desalination process that would require substantially less energy than reverse osmosis.[33]

Another method being looked into for water desalination is the use of biomimetic membranes [34]

On June 23, 2008, it was reported that Siemens Water Technologies had developed a new technology, based on applying electric field on seawater, that desalinates one cubic meter of water while using only 1.5 kWh of energy, which, according to the report, is one half the energy that other processes use.[35]

Fresh water can also be produced by freezing seawater, as happens naturally in the polar regions, and is known as freeze-thaw desalination.

According to MSNBC, a report by Lux Research estimated that the worldwide desalinated water supply will triple between 2008 and 2020.[36]

Low Temperature Thermal Desalination

Low Temperature Thermal Desalination (LTTD) takes advantage of the fact that water boils at low pressures, even as low as 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 to 10 degrees C between two volumes of water. Cooling water is supplied from sea depths of as much as 600 metres (2,000 ft). This cold water is pumped through coils to condense the evaporated water vapor. The resulting condensate is purified water. The LTTD process may also take advantage of the temperature gradient available at power plants, where large quantities of warm waste water are discharged from the plant, reducing the energy input needed to create a temperature gradient.[37]

LTTD was developed by India's National Institute of Ocean Technology (NIOT) from 2004. The world's first LTTD plant was opened in 2005 at Kavaratti in the Lakshadweep islands. The plant's capacity is 100,000 liters/day, at a capital cost of INR 50 million (€922,000). The plant uses deep water at a temperature of 7 to 15 degrees C.[38] In 2007, NIOT opened an experimental floating LTTD plant off the coast of Chennai with a capacity of 1 million liters/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..[39][40][37]

Thermo-ionic 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 empties all the sodium and chlorine ions from the water.[41]

Existing facilities and facilities under construction

Abu Dhabi, United Arab Emirates

  • Taweelah A1 Power and Desalination Plant has an output 385 million liters per day of clean water
  • Umm Al Nar Desalination Plant has an output of 394 million liters a day of clean water
  • Fujairah F2 is to be completed by July 2010 will have a water production capacity of 492 million liters (130 million gallons) per day.[42]

Aruba

The island of Aruba has a large (world’s largest at the time of its inauguration) desalination plant with the total installed capacity of 42000 metric tons (11.1 million gallons or 42 × 103 m3) per day.[43]

Australia

A combination of increased water usage and lower rainfall in Australia has caused State governments to build a number of desalination plants, including the recently commissioned Kurnell Desalination Plant serving the Sydney area. While desalination has been adopted by state governments to secure water supply, it is highly energy intensive (~$140 energy demand/ML) and has a high carbon footprint due to continued reliance on Australia's coal-based energy generation.

Cyprus

There are also desalination plants in Cyprus, like the one near the town of Larnaca.[44] This is called the Dhekelia Desalination Plant, which utilises the reverse osmosis system.[45]

Israel

The Hadera seawater reverse osmosis (SWRO) desalination plant in Israel is the largest of its kind in the world.[46][47] The project was developed as a BOT (Build-Operate-Transfer) by a consortium of three international companies: Veolia water, IDE Technologies and Elran.[48]

Existing Israeli water desalination facilities[49]
Location Opening Capacity
(mln m3/year)
Capacity
(mln gallons/day)
Capacity
(megaliters)
Cost of water (per m3) Notes
Ashkelon August 2005 111 (as of 2008) 83.2 315 NIS 2.60 [50]
Palmachim May 2007 30 (expansion up to 45 planned [51]) 32.6 123.4 NIS 2.90 [52]
Hadera December 2009 127 91.9 349 NIS 2.60 [53]
Israeli water desalination facilities under construction
Location Opening Capacity
(mln m3/year)
Cost of water (per m3) Notes
Ashdod 2012 100 (expansion up to 150 possible) NIS 2.55 [54] [55]
Soreq 2013 150 (expansion up to 300 approved) NIS 2.01 - 2.19 [56]

United Kingdom

Beckton Desalination Plant

The first water desalination plant in the United Kingdom, the Thames Water Desalination Plant,[57] has been built in Beckton, east London for Thames Water by Acciona Agua

United States

El Paso (Texas) Desalination Plant

Brackish groundwater has been treated at the El Paso plant since around 2004. Producing 27.5 million gallons (104,000 m³) of fresh water daily (about 25% of total freshwater deliveries) by reverse osmosis, it is a crucial contribution to water supplies in this water-stressed city.[58]

Tampa Bay Water Desalination Project

The Tampa Bay Water Desalination project was originally a private venture led by Poseidon Resources. This project was delayed by the bankruptcy of Poseidon Resources' successive partners in the venture, Stone & Webster, then Covanta (formerly Ogden) and its principal subcontractor Hydranautics. Poseidon's relationship with Stone & Webster through S & W Water LLC ended in June 2000 when Stone & Webster declared bankruptcy and Poseidon Resources purchased Stone & Webster's stake in S & W Water LLC. Poseidon Resources partnered with Covanta and Hydranautics in 2001, changing the consortium name to Tampa Bay Desal. Through the inability of Covanta to complete construction bonding of the project, the Tampa Bay Water agency was forced to purchase the project from Poseidon on May 15, 2002, and underwrite the project financing under its own credit rating. Tampa Bay Water then contracted with Covanta Tampa Construction, which produced a project that did not meet required performance tests. Covanta Tampa Construction's parent company filed bankruptcy in October 2003 to prevent losing the contract with Tampa Bay Water. Then, Covanta Tampa Construction filed bankruptcy prior to performing renovations that would have satisfied contractual agreements. This resulted in nearly six months of litigation between Covanta Tampa Construction and Tampa Bay Water. 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[23] and is designed to run at a maximum capacity of 25 million gallons per day.[59] Nevertheless, the plant continues to be set with problems limiting it to producing only about half that amount (14 million gallons per day or 42 af / day in 2009.[60]

Yuma Desalting Plant (Arizona)

The Yuma Desalting Plant was constructed under authority of the Colorado River Basin Salinity Control Act of 1974 to treat saline agricultural return flows from the Wellton-Mohawk Irrigation and Drainage District. The treated water is intended for inclusion in water deliveries to Mexico thereby preserving the like amount of water in Lake Mead. Construction of the plant was completed in 1992 and it has operated on two occasions since then. The plant has been maintained, but largely not operated due to surplus and then normal water supply conditions on the Colorado River.[61] 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.[62]

Trinidad and Tobago

The Republic of Trinidad and Tobago is using desalination to free up more of the island's water supply for drinking purposes. The desalination facility, opened in March 2003, is considered to be the first of its kind. It is the largest desalination facility in the Americas and will process 28.8 million gallons of water a day and sell water at the price of $2.67 per 1,000 gallons.[63] This facility will be located at Trinidad's Point Lisas Industrial Estate, a park of more than 12 companies in various manufacturing and processing functions and will allow for easy access to water for both factories and residents in the country.[64]

See also

References

Notes

  1. ^ "Desalination" (definition), The American Heritage Science Dictionary, Houghton Mifflin Company, via dictionary.com. Retrieved on 2007-08-19.
  2. ^ "Australia Aids China In Water Management Project." People's Daily Online, 2001-08-03, via english.people.com.cn. Retrieved on 2007-08-19.
  3. ^ Fischetti, Mark (September 2007). "Fresh from the Sea". Scientific American (Scientific American, Inc.) 297 (3): pp. 118–119. doi:10.1038/scientificamerican0907-118. http://www.sciam.com/article.cfm?id=fresh-from-the-sea. Retrieved 2008-08-03  Note: only the first two paragraphs are available on-line for no charge.
  4. ^ Applause, At Last, For Desalination Plant, The Tampa Tribune, December 22, 2007
  5. ^ Kathryn Kranhold, Water, Water, Everywhere..., The Wall Street Journal, January 17, 2008
  6. ^ Source: water-technology.net
  7. ^ Hamed, Osman A. (2005). “Overview of hybrid desalination systems – current status and future prospects.” Desalination, 186, 207-214.
  8. ^ Misra, B.M., J. Kupitz. (2004). “The role of nuclear desalination in meeting potable water needs in water scarce areas in the next decades.” Desalination, 166, 1-9.
  9. ^ http://gift.kisti.re.kr/GTB/infoboard/download.jsp?down_url=data/file/GTB/shleegift/shleegift_1198793876096.doc&cn=GTB2007120672
  10. ^ Nuclear Desalination. Retrieved on 2010-01-07
  11. ^ Ludwig, Heinz. (2004). “Hybrid systems in seawater desalination – practical design aspects, present status and development perspectives.” Desalination, 164, 1-18.
  12. ^ How Aircraft Carriers Work
  13. ^ "Nuclear Desalination". World Nuclear Association. January 2010. http://www.world-nuclear.org/info/inf71.html. Retrieved 2010-02-01. 
  14. ^ Barlow, Maude, and Tony Clarke, "Who Owns Water?" The Nation, 2002-09-02, via thenation.com. Retrieved on 2007-08-20.
  15. ^ Zhoua, Yuan, and Richard S.J. Tolb. "Evaluating the costs of desalination and water transport." (Working paper). Via a Hamburg University website. 2004-12-09. Retrieved on 2007-08-20.
  16. ^ Desalination is the Solution to Water Shortages, redOrbit, May 2, 2008
  17. ^ Sitbon, Shirli. "French-run water plant launched in Israel," European Jewish Press, via ejpress.org, 2005-12-28. Retrieved on 2007-08-20.
  18. ^ "Black & Veatch-Designed Desalination Plant Wins Global Water Distinction," (Press release). Black & Veatch Ltd., via edie.net, 2006-05-04. Retrieved on 2007-08-20.
  19. ^ http://www.water-technology.net/projects/perth/
  20. ^ "Sydney desalination plant to double in size," ABC News (Australian Broadcasting Corporation), via abc.net.au, 2007-06-25. Retrieved on 2007-08-20.
  21. ^ Australia Turns to Desalination by Michael Sullivan and PX Pressure Exchanger energy recovery devices from Energy Recovery Inc. An Environmentally Green Plant Design. Morning Edition, National Public Radio, June 18, 2007
  22. ^ Fact sheets
  23. ^ a b http://www.tampabaywater.org/watersupply/tbdesalhistory.aspx
  24. ^ Hydro-Alchemy, Forbes, May 9, 2008
  25. ^ Ottawa student may hold secret to Water For All, Globe and Mail, June 5, 2008
  26. ^ The Arid West—Where Water Is Scarce - Desalination—a Growing Watersupply Source, Library Index
  27. ^ http://www.desalresponsegroup.org/files/RiverkeepervEPA1-25-07_decision.pdf
  28. ^ untitled
  29. ^ Gleick, Peter H., Dana Haasz, Christine Henges-Jeck, Veena Srinivasan, Gary Wolff, Katherine Kao Cushing, and Amardip Mann. (November 2003.) "Waste not, want not: The potential for urban water conservation in California." (Website). Pacific Institute. Retrieved on 2007-09-20.
  30. ^ Cooley, Heather, Peter H. Gleick, and Gary Wolff. (June 2006.) "Desalination, With a Grain of Salt – A California Perspective." (Website). Pacific Institute. Retrieved on 2007-09-20.
  31. ^ Gleick, Peter H., Heather Cooley, David Groves. (September 2005.) "California water 2030: An efficient future." (Website). Pacific Institute. Retrieved on 2007-09-20.
  32. ^ http://www.sunbeltwater.com/docs.shtml Sun Belt Inc. Legal Documents
  33. ^ Lawrence Livermore National Laboratory Public Affairs (2006-05-18). "Nanotube membranes offer possibility of cheaper desalination". Press release. http://www.llnl.gov/pao/news/news_releases/2006/NR-06-05-06.html. Retrieved 2007-09-07. 
  34. ^ Biomimetic membrane for water desalination
  35. ^ Team wins $4m grant for breakthrough technology in seawater desalination, The Straits Times, June 23, 2008
  36. ^ A Rising Tide for New Desalinated Water Technologies, MSNBC, March. 17, 2009
  37. ^ a b Sistla, Phanikumar V.S.; et al. "Low Temperature Thermal DesalinbationPLants". International Society of Offshore and Polar Engineers. http://www.isope.org/publications/proceedings/ISOPE_OMS/OMS%202009/papers/M09-83Sistla.pdf. Retrieved 22 June 2010. 
  38. ^ Desalination: India opens world’s first low temperature thermal desalination plant
  39. ^ Floating plant, India
  40. ^ Mobile Desalination plant, India
  41. ^ Current thinking, Oct 29th 2009, The Economist
  42. ^ http://www.pump-zone.com/global-news/global-news/abu-dhabi-to-build-three-power-and-water-desalination-plants-by-2016-to-meet-demand.html
  43. ^ W.E.B. Aruba N.V. - Water Plant
  44. ^ [1]
  45. ^ [2]
  46. ^ Israel is No. 5 on Top 10 Cleantech List in Israel 21c A Focus Beyond Retrieved 2009-12-21
  47. ^ Ashkelon Desalination Plant Seawater Reverse Osmosis (SWRO) Plant
  48. ^ Ashkelon desalination plant — A successful challenge
  49. ^ Public-Private Partnership Projects, Accountant General, Ministry of Finance
  50. ^ water-technology.net:[http://www.water-technology.net/projects/israel/ "Ashkelon Desalination Plant Seawater Reverse Osmosis (SWRO) Plant, Israel"
  51. ^ Euro-Mediterranean Water Information System (EMWIS):"Israel: Finance secured for Palmachim desalination expansion", August 19, 2009
  52. ^ Anonymous Blogger "Israeli Water Engineer":"Israel's Desalination Industry", September 6, 2007
  53. ^ Globes Business and Technology News:"Funding agreed for expanding Hadera desalination plant", November 6, 2009
  54. ^ Desalination & Water Reuse:"Spanish/Israeli JV awarded Ashdod desalination contract", 24 November 2009
  55. ^ Globes Business and Technology News:"Mekorot, gov't near desalination water price compromise", June 20, 2010
  56. ^ Desalination & Water Reuse:"IDE reported winner of Soreq desalination contract", 15 December 2009
  57. ^ Thames Water Desalination Plant: water-technology.net
  58. ^ http://www.epwu.org/water/desal_info.html
  59. ^ http://www.tampabaywater.org/facilities/desalination_plant/index.aspx
  60. ^ http://www.tampabay.com/news/environment/water/article984409.ece
  61. ^ "Yuma Desalting Plant" U.S. Bureau of Reclamation, retrieved May 1, 2010
  62. ^ "A fresh start for Yuma desalting plant" Los Angeles Times, May 1, 2010
  63. ^ http://www.bizjournals.com/boston/stories/1999/10/04/story7.html"
  64. ^ http://www.waterindustry.org/New%20Projects/ionics-2.htm"

Further reading

Articles

External links


Study guide

Up to date as of January 14, 2010

From Wikiversity

Learn about desalination...

Reverse osmosis One of the most common forms of Desalination is Reverse osmosis (RO). This technology comprises imposing pressure on a high turbidity/salinity fluid in contact with a membrane. The membrane acts as a solvent to the fluid, i.e. the fluid is soluble in the membrane. After the membrane becomes saturated with fluid, the fluid then diffuses into the space on the non-saline side of the membrane. The membrane is also considered semi-permeable to hydroxide (OH-) and hydronium (H+) ions, which are water's natural state, and pass through the membrane as they would through any particle exclusion barrier. In these ways, salinity and turbidity may be filtered out of the fluid sourcewater.

Learning questions

Would utilizing desalination on a mass scale have undesirable environmental outcomes?

I think the primary impact would be in energy consumption but if the scale were massive enough then there could be impacts on deserts or other terrain as human activities; such as farms, cities and homes; previously water limited expand. Mirwin 13:16, 25 September 2007 (UTC)

The recently developed desalination plants and/or systems are equipped with Energy Recovery device which considerably reduce energy consumption up to 40 percent,In fact the required energy to desalinate 1 cubic meter of seawater is about 3 KW. However the impact of Reverse Osmosis brine discharge to marine environment is still irrevocable.The high saline brine water outfall, which typically discharges in the ocean have enormus undesireable negative impacts in nature and marine life that could be stopped by few simple works such as discharging in deep beach wells and/or discharging through different tiny branches instead of one big diameter pipe and etc.

See also

External links


Simple English

Desalination means any process that removes the excess salt and other minerals from water in order to obtain fresh water suitable for animal consumption or irrigation.

If almost all of the salt is removed for human consumption, sometimes the process produces table salt as a by-product.

Desalination of brackish water is done in the United States in order to meet treaty obligations for river water entering Mexico. Several Middle Eastern countries have energy reserves so great that they use desalinated water for agriculture. Saudi Arabia's desalination plants account for about 24% of total world capacity. The world's largest desalination plant is the Jebel Ali Desalination Plant (Phase 2) in UAE. It uses multi-stage flash distillation, dual-purpose and it is capable of producing 300 million cubic meters of water per year.[1]

Methods

  1. Distillation
    1. Multi-stage flash (MSF)
    2. Multiple-effect (MED|ME)
    3. Vapor compression (VC)
    4. Evaporation/condensation
  2. Membrane processes
    1. Electrodialysis reversal (EDR)
    2. Reverse osmosis (RO)
    3. Nanofiltration (NF)
    4. Forward osmosis (FO)
    5. Membrane distillation (MD)
  3. Freezing
  4. Geothermal
  5. Solar humidification (HDH, MEH)
  6. Methane hydrate crystallisation
  7. High grade water recycling

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. Due to the reduced temperature, energy is saved.

References

  1. Saline Water Conversion Corporation

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