Editing Desalination (section)

===Energy consumption===
The desalination process's energy consumption depends on the water's salinity. [[Brackish water]] desalination requires less energy than [[seawater]] desalination.<ref name="Panagopoulos2020">{{Cite journal|last=Panagopoulos|first=Argyris|date=2020-12-01|title=A comparative study on minimum and actual energy consumption for the treatment of desalination brine|url=http://www.sciencedirect.com/science/article/pii/S0360544220318405|journal=Energy|language=en|volume=212|pages=118733|doi=10.1016/j.energy.2020.118733|bibcode=2020Ene...21218733P |s2cid=224872161|issn=0360-5442}}</ref>

The energy intensity of seawater desalination has improved: It is now about 3 kWh/m<sup>3</sup> (in 2018), down by a factor of 10 from 20-30 kWh/m<sup>3</sup> in 1970.<ref name="IWA2022" />{{rp|24}} This is similar to the energy consumption of other freshwater supplies transported over large distances,<ref>Wilkinson, Robert C. (March 2007) [http://www.westbasin.org/files/general-pdfs/Energy--UCSB-energy-study.pdf "Analysis of the Energy Intensity of Water Supplies for West Basin Municipal Water District"] {{webarchive|url=https://web.archive.org/web/20121220210850/http://www.westbasin.org/files/general-pdfs/Energy--UCSB-energy-study.pdf |date=December 20, 2012 }}, Table on p. 4</ref> but much higher than local fresh [[water supply|water supplies]] that use 0.2 kWh/m<sup>3</sup> or less.<ref>[http://www.circleofblue.org/waternews/wp-content/uploads/2010/08/EPRI-Volume-4.pdf "U.S. Electricity Consumption for Water Supply & Treatment"] {{webarchive|url=https://web.archive.org/web/20130617040130/http://www.circleofblue.org/waternews/wp-content/uploads/2010/08/EPRI-Volume-4.pdf |date=June 17, 2013 }}, pp. 1–4 Table 1-1, Electric Power Research Institute (EPRI) Water & Sustainability (Volume 4), 2000</ref>

A minimum energy consumption for seawater desalination of around 1 kWh/m<sup>3</sup> has been determined,<ref name="Panagopoulos2020" /><ref>Elimelech, Menachem (2012) [http://www.nwri-usa.org/documents/Elimelech_000.pdf "Seawater Desalination"] {{Webarchive|url=https://web.archive.org/web/20140223110451/http://www.nwri-usa.org/documents/Elimelech_000.pdf |date=February 23, 2014 }}, p. 12 ff</ref><ref>{{Cite journal | doi = 10.1021/es801330u| pmid = 19068794| title = Energy Issues in Desalination Processes| journal = Environmental Science & Technology| volume = 42| issue = 22| pages = 8193–201| year = 2008| last1 = Semiat | first1 = R. |bibcode = 2008EnST...42.8193S }}</ref> excluding prefiltering and intake/outfall pumping. Under 2 kWh/m<sup>3</sup><ref>[http://www.usbr.gov/research/AWT/reportpdfs/ADC_SWRO_DA.pdf "Optimizing Lower Energy Seawater Desalination"] {{Webarchive|url=https://web.archive.org/web/20150618132743/http://www.usbr.gov/research/AWT/reportpdfs/ADC_SWRO_DA.pdf |date=2015-06-18 }}, p. 6 figure 1.2, Stephen Dundorf at the IDA World Congress November 2009</ref> has been achieved with [[reverse osmosis]] membrane technology, leaving limited scope for further energy reductions as the [[reverse osmosis]] energy consumption in the [[1970s]] was 16 kWh/m<sup>3</sup>.<ref name="Panagopoulos2020" />

Supplying all US domestic water by desalination would increase domestic [[Energy in the United States|energy consumption]] by around 10%, about the amount of energy used by domestic refrigerators.<ref>[http://www.amtaorg.com/wp-content/uploads/7_MembraneDesalinationPowerUsagePutInPerspective.pdf "Membrane Desalination Power Usage Put In Perspective" ] {{Webarchive|url=https://web.archive.org/web/20140424044855/http://www.amtaorg.com/wp-content/uploads/7_MembraneDesalinationPowerUsagePutInPerspective.pdf |date=April 24, 2014 }}, American Membrane Technology Association (AMTA) April 2009</ref> Domestic consumption is a relatively small fraction of the total water usage.<ref>[http://water.usgs.gov/edu/wateruse-total.html] Total Water Use in the United States</ref>

{| class="wikitable sortable wiki table"
|+ Energy consumption of seawater desalination methods (kWh/m<sup>3</sup>)<ref>[http://www.desware.net/Energy-Requirements-Desalination-Processes.aspx "Energy Requirements of Desalination Processes"], ''Encyclopedia of Desalination and Water Resources'' (DESWARE). Retrieved June 24, 2013</ref>
|- style="line-height:120%;"
! Desalination Method   ⇨
! rowspan="2" | [[Multi-stage flash distillation|Multi-stage<br>Flash<br>"MSF"]]
! rowspan="2" | [[Multiple-effect distillation|Multi-Effect<br>Distillation<br>"MED"]]
! rowspan="2" | [[Vapor-compression desalination|Mechanical Vapor<br>Compression<br>"MVC"]]
! rowspan="2" | [[Reverse osmosis|Reverse<br>Osmosis<br>"RO"]]
|- style="line-height:120%;"
! Energy ⇩
|-
| Electrical energy || 4–6 || 1.5–2.5 || 7–12 || 3–5.5
|-
| Thermal energy || 50–110 || 60–110 || ''none'' || ''none''
|-
| Electrical equivalent of thermal energy || 9.5–19.5 || 5–8.5 || ''none'' || ''none''
|-
| Total equivalent electrical energy || 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 an appropriate turbine generator. These calculations do not include the energy required to construct or refurbish items consumed.

Given the energy-intensive nature of desalination and the associated economic and environmental costs, desalination is generally considered a last resort after [[water conservation]]. But this is changing as prices continue to fall.