Editing Desalination (section)

==Applications==

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| audio1 = [https://www.sciencehistory.org/distillations/podcast/making-the-deserts-bloom "Making the Deserts Bloom: Harnessing nature to deliver us from drought"], Distillations Podcast and transcript, Episode 239, March 19, 2019, [[Science History Institute]] }}
[[File:Multiflash.svg|thumb|right|upright=1.5|Schematic of a [[multistage flash distillation|multistage flash desalinator]]<br>A – steam in&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;B – seawater in&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;C – potable water out<br>D – brine out (waste)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;E – [[condensation|condensate]] out&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F – heat exchange&nbsp;&nbsp;&nbsp;&nbsp;G – condensation collection (desalinated water)<br>H – brine heater<br>
The [[pressure vessel]] acts as a [[countercurrent exchange|countercurrent heat exchanger]]. A [[vacuum pump]] lowers the pressure in the vessel to facilitate the evaporation of the heated seawater ([[brine]]) which enters the vessel from the right side (darker shades indicate lower temperature). The steam condenses on the pipes on top of the vessel in which the fresh sea water moves from the left to the right.]]

There are now about 21,000 desalination plants in operation around the globe. The biggest ones are in the [[United Arab Emirates]], [[Saudi Arabia]], and [[Israel]]. The world's largest desalination plant is located in [[Saudi Arabia]] ([[Ras Al-Khair Power and Desalination Plant]]) with a capacity of 1,401,000 cubic meters per day.<ref>{{Cite web|title=Largest water desalination plant|url=https://www.guinnessworldrecords.com/world-records/425709-largest-water-desalination-plant|access-date=2020-08-21|website=Guinness World Records|language=en-GB}}</ref>

Desalination is currently expensive compared to most alternative sources of water, and only a very small fraction of total human use is satisfied by desalination.<ref>{{Cite journal |last1=Do Thi |first1=Huyen Trang |last2=Pasztor |first2=Tibor |last3=Fozer |first3=Daniel |last4=Manenti |first4=Flavio |last5=Toth |first5=Andras Jozsef |date=January 2021 |title=Comparison of Desalination Technologies Using Renewable Energy Sources with Life Cycle, PESTLE, and Multi-Criteria Decision Analyses |journal=Water |language=en |volume=13 |issue=21 |pages=3023 |doi=10.3390/w13213023 |issn=2073-4441|doi-access=free |hdl=11311/1197124 |hdl-access=free }}</ref> It is usually only economically practical for high-valued uses (such as household and industrial uses) in [[arid]] areas. However, there is growth in desalination for agricultural use and highly populated areas such as Singapore<ref>{{Cite web |last=Theng |first=Charlotte Kng Yoong |date=2022-09-16 |title=From NEWater to vertical farming: Key milestones in Singapore's 50-year journey towards sustainability {{!}} The Straits Times |url=https://www.straitstimes.com/singapore/environment/mse-from-newater-to-vertical-farming-key-milestones-singapore-50-year-journey-towards-sustainability |access-date=2023-04-21 |website=www.straitstimes.com |language=en}}</ref> or California.<ref>{{Cite news |last=Canon |first=Gabrielle |date=2022-05-11 |title=California to decide fate of controversial desalination plant amid brutal drought |language=en-GB |work=The Guardian |url=https://www.theguardian.com/environment/2022/may/11/california-desalination-plant-water-drought |access-date=2023-04-21 |issn=0261-3077}}</ref><ref>{{Cite web |date=2022-04-03 |title=Mini desalination plants could refresh the parched West |url=https://www.popsci.com/environment/desalination-drought-california/ |access-date=2023-04-21 |website=Popular Science |language=en-US}}</ref> The most extensive use is in the [[Persian Gulf]].<ref>{{Cite journal |last1=Le Quesne |first1=W. J. F. |last2=Fernand |first2=L. |last3=Ali |first3=T. S. |last4=Andres |first4=O. |last5=Antonpoulou |first5=M. |last6=Burt |first6=J. A. |last7=Dougherty |first7=W. W. |last8=Edson |first8=P. J. |last9=El Kharraz |first9=J. |last10=Glavan |first10=J. |last11=Mamiit |first11=R. J. |date=2021-12-01 |title=Is the development of desalination compatible with sustainable development of the Arabian Gulf? |journal=Marine Pollution Bulletin |language=en |volume=173 |issue=Pt A |pages=112940 |doi=10.1016/j.marpolbul.2021.112940 |pmid=34537571 |bibcode=2021MarPB.17312940L |s2cid=237574682 |issn=0025-326X|doi-access=free }}</ref>

While noting costs are falling, and generally positive about the technology for affluent areas in proximity to oceans, a 2005 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 the 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."<ref>{{cite journal |last1=Zhou |first1=Yuan |title=Evaluating the costs of desalination and water transport |journal=Water Resources Research |date=2 March 2005 |volume=41 |issue=3 |page=03003 |doi=10.1029/2004WR003749|bibcode=2005WRR....41.3003Z |hdl=11858/00-001M-0000-0011-FF1E-C |s2cid=16289710 |hdl-access=free }}</ref>

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, Arizona|Phoenix]], and, of course, coastal cities like [[Tripoli, Libya|Tripoli]].<ref>Yuan Zhou and Richard S.J. Tol. {{cite web|date=December 9, 2004|title=Evaluating the costs of desalination and water transport|url=http://www.uni-hamburg.de/Wiss/FB/15/Sustainability/DesalinationFNU41_revised.pdf|url-status=dead|archive-url=https://web.archive.org/web/20090325031333/http://www.uni-hamburg.de/Wiss/FB/15/Sustainability/DesalinationFNU41_revised.pdf|archive-date=March 25, 2009|access-date=August 20, 2007|publisher=Hamburg University|type=Working paper}}</ref> After desalination at [[Jubail]], Saudi Arabia, water is pumped 320&nbsp;km inland to [[Riyadh]].<ref>[http://www.redorbit.com/news/science/1367352/desalination_is_the_solution_to_water_shortages/ Desalination is the Solution to Water Shortages], redOrbit, May 2, 2008,</ref> For coastal cities, desalination is increasingly viewed as a competitive choice.

In 2023, Israel was using desalination to replenish the [[Sea of Galilee]]'s water supply.<ref>[https://www.yahoo.com/news/israel-refills-sea-galilee-supplying-215147564.html Israel refills the Sea of Galilee, supplying Jordan on the way], Reuters, January 30, 2023, [https://web.archive.org/web/20230131022001/https://www.yahoo.com/news/israel-refills-sea-galilee-supplying-215147564.html Archive], [https://www.youtube.com/watch?v=F1pogU_5TYY, Video at Reuters YouTube channel]</ref>

Not everyone is convinced that desalination is or will be economically viable or environmentally sustainable for the foreseeable future. [[Debbie Cook]] wrote in 2011 that desalination plants can be energy intensive and costly. Therefore, water-stressed regions might do better to focus on conservation or other water supply solutions than invest in desalination plants.<ref>[http://blogs.ei.columbia.edu/2011/01/17/desalination-unlocking-lessons-from-yesterdays-solution-part-1/ Desalination: Unlocking Lessons from Yesterday's Solution (part 1)], Water Matters, January 17, 2009.</ref>