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[[Image:evap desal icon.png|right|80px]][[Image:SolarDistiller.jpg|thumb|right|350px200px|Gabriele Diamanti's "Eliodomestico" solar-powered eco-distiller. The small, vat-like still is made entirely from terracotta and zinc-plated metal sheets. It is designed to be produced (and eventually repaired) by local craftsmen.]][[Image:water pyramid.jpg|thumb|right|200px|The [https://changemakers.org/sites/default/files/waterpyramid%20brochure%20mrt%2008.pdf WaterPyramid] is used in tropical remote regions to desalinate saline water and to harvest rainwater. The technology is best used were abundant radiation of the sun and free ground space is available. Photo: Aqua-Aero WaterSystems.]]__NOTOC__ <small-title />Desalination is used to remove salts from brackish or saline surface water and groundwater in order to render it acceptable for human consumption or other uses. Brackish water is defined as having a Total Dissolved Solids content of 1,000 mg/l, and saline water as having 10,000 mg/l. It is increasingly employed to provide drinking-water because of a growing scarcity of fresh water driven by population growth, overexploitation of water resources and climate change. Desalination facilities exist all over the world, particularly in the eastern Mediterranean region, with use increasing on all continents. Small-scale desalination is used to supply fresh water on ships and to provide additional fresh water in some hot and arid regions.
Desalination is used to remove by distillation produces water without chemical salts from brackish or saline surface water and groundwater in order to render it acceptable for human consumption or other uses. Brackish water is defined as starting at having a Total Dissolved Solids content The method can be expensive because of 1,000 mg/l, the capital investment needed and saline water as having 10,000 mgbecause fuel/l. It charcoal is increasingly employed used to provide drinking-heat the water because of a growing scarcity of fresh water driven by population growth. However, overexploitation solar distillation is inexpensive. The volume of water resources and climate change. Desalination facilities exist all over the world, particularly in the eastern Mediterranean region, with use increasing on all continents. Small-scale desalination produced is used to supply fresh water on ships and to provide additional fresh water in some hot and arid regionsgenerally low.
* Natural waters may be classified approximately according to their Total Dissolved Solids (TDS) values:
[[File:TDS chart.jpg]]
===Resilience to changes in the environment=======Drought===='''Effects of drought''': Salinity increases; Corrosion of equipment/pipes.<br>'''Underlying causes of effects''':Less recharge leads to less dilution of naturally-occurring minerals; More demand creates more extraction; Saline intrusion; Higher population means more pollution from anthropogenic sources<br>'''To increase resiliency of WASH system''': Diversify water sources; Household & communal level solar distillation; Managed Aquifer Recharge (MAR); Reduce water-logging in irrigated areas. ===Construction, operations and maintenance===[[Image:DistillationSetup.jpg|thumb|right|350px200px|Click drawing to zoom in.]][[Image:Distillation.jpg|thumb|right|350px200px|Simple distillation and condensation.]]
Of the desalination methods available, the two main ones are: '''distillation''' followed by condensation and '''reverse osmosis'''.
'''Household solar stills''' <br>
Household solar stills have not been widely promoted, yet can provide 2.5 – 3 litres per m2 surface area per day. However there is
scope to increase yields – more efficient and expensive stills (Aqua Solaris) have been tried that can increase volume to 40 litres per m2 per day. Water temperatures must be high, while the condensing surface should be as cool as possible – for this reason stills are most efficient in the early evening when water is still warm but temperature of the glass is a lot lower, and stills continue to produce water during the night. Water extraction for solar stills takes place by gravity of condensate to a gutter which leads to a container or tank.
The Watercone is a massproduced innovation that can produce 1.5 litres maximum per cone per day, but tends to be expensive. Solar stills can be constructed using local materials which are cheaper. There are key points to get right:
Salinization of shallow groundwater can occur due to water-logging (e.g. where irrigation is practiced) – this is because of a shallow water table and high evaporation rates. Techniques to reduce salinity include:
Legislation can impact increasing levels of groundwater salinity – in Mozambique, the government prohibited the drilling of new boreholes in rural areas where salinity was an issue. This combined with rainwater MAR techniques proved to be a good combination at addressing the saline issue.
Water produced by desalination is low in minerals and usually aggressive towards materials with which it comes into contact, such as materials used for distribution pipes, storage and plumbing. During post-treatment, the water must be stabilized or re-mineralized prior to distribution to reduce its corrosive nature. Stabilization is commonly achieved by adding chemical constituents such as calcium and magnesium carbonate along with pH adjustment or through blending with small volumes of mineral-rich waters.
===Costs==='''Solar still costs'''
* Cost can be reasonably high – between £50-£70 (US$70 - US$100) per m2.<br>
* In Afghanistan, a locally-produced still was priced up at US$65.
* Cost is proportional to output, so there are no economies of scale when scaling up as there are with other treatment methods.
===Field experiences==={|style="border: 2px solid #e0e0e0; width: 40%; text-align: justify; background-color: #e9f5fd;" cellpadding="2"<!--rsr logo here-->|- style="vertical-align: top"|[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]]||[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]]<!--project blocks here-->|- style="vertical-align: bottom"|[[Image: rsr 476.jpg|thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/project/476/ RSR Project 476]<br>Ensure access to safe water and sanitation</center></font>|link=http://rsr.akvo.org/project/476/]] |[[Image: rsr 769.jpg|thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/project/769/ RSR Project 769]<br>Life-WASH</center></font>|link=http://rsr.akvo.org/project/769/]] |[[Image: rsr 770.jpg|thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/project/770/ RSR Project 770]<br>title</center></font>|link=http://rsr.akvo.org/project/770/]] |} ===Manuals, videos and links==={|align="none"|{{#ev:youtube|c9fepEyGRx8|200|auto|<font size="2"><center>Watercone solar distiller</center></font>}}|[[Image:solar cucumber.jpg|thumb|right|200px|The [http://www.philpauley.com/cucumber.php Solar Cucumber] desalinates sea water and produces drinkable freshwater. As of 2012, the Solar Cucumber is still in the concept phase. Photo: Phil Pauley.]]|}* [http://www.cawst.org/en/resources/pubs/education-materials/category/25-fact-sheets-academic HWTS Factsheet - Solar Distillation]. * [http://docs.watsan.net/Downloaded_Files/PDF/WHO-2011-Safe.pdf Safe Drinking-water from Desalination] or ([http://apps.who.int/iris/bitstream/10665/70621/1/WHO_HSE_WSH_11.03_eng.pdf alternative link]). World Health Organization, 2011. * [http://www.lboro.ac.uk/well/resources/technical-briefs/40-desalination.pdf Desalination] or ([http://www.washdoc.info/docsearch/title/116234 alternative link]). WEDC Loughborough University. * BLOG: [http://www.core77.com/blog/sustainable_design/eliodomestico_solar_household_still_by_gabriele_diamanti_20893.asp Gabriele Diamanti's "Eliodomestico" solar-powered eco-distiller]. * ARTICLE: [http://www.nytimes.com/2011/03/22/business/energy-environment/22iht-rbog-technology-22.html?scp=1&sq=New+Technology+Could+Make+Desalination+More+Accessible&st=nyt# New Technology Could Make Desalination More Accessible]. New York Times. * The [https://changemakers.org/sites/default/files/waterpyramid%20brochure%20mrt%2008.pdf Water Pyramid] by Aqua-Aero WaterSystems. ===Acknowledgements===* CARE Nederland, Desk Study: [[Resilient WASH systems in drought-prone areas]]. October 2010.