Editing Desalination (section)

===Outflow===
{{More citations needed section|date=January 2012}}
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 (especially in thermal-based plants).<ref name="PanagopoulosHaralambous2020">{{Cite journal|last1=Panagopoulos|first1=Argyris|last2=Haralambous|first2=Katherine-Joanne|date=2020-10-01|title=Minimal Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) strategies for wastewater management and resource recovery – Analysis, challenges and prospects|url=http://www.sciencedirect.com/science/article/pii/S2213343720307673|journal=Journal of Environmental Chemical Engineering|language=en|volume=8|issue=5|pages=104418|doi=10.1016/j.jece.2020.104418|s2cid=225309628|issn=2213-3437}}</ref><ref>Greenberg, Joel (March 20, 2014) [http://www.mcclatchydc.com/2014/03/20/221880/israel-no-longer-worried-about.html "Israel no longer worried about its water supply, thanks to desalination plants"] {{Webarchive|url=https://web.archive.org/web/20140324202006/http://www.mcclatchydc.com/2014/03/20/221880/israel-no-longer-worried-about.html |date=March 24, 2014 }}, ''[[The McClatchy Company|McClatchy DC]]''</ref> 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.<ref>{{cite journal|doi=10.1016/j.desal.2007.03.009 |title=Environmental impact and impact assessment of seawater desalination|year=2008|last1=Lattemann|first1=Sabine|last2=Höpner|first2=Thomas|journal=Desalination|volume=220|issue=1–3|page=1|bibcode=2008Desal.220....1L }}</ref>

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 [[Sewage treatment|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. Furthermore, zero liquid discharge systems can be adopted to treat brine before disposal.<ref name="PanagopoulosHaralambous2020" /><ref>Szeptycki, L., E. Hartge, N. Ajami, A. Erickson, W. N. Heady, L. LaFeir, B. Meister, L. Verdone, and J.R. Koseff (2016). Marine and Coastal Impacts on Ocean Desalination in California. Dialogue report compiled by Water in the West, Center for Ocean Solutions, Monterey Bay Aquarium and The Nature Conservancy, Monterey, CA. https://www.scienceforconservation.org/assets/downloads/Desal_Whitepaper_2016.pdf</ref>

Another possibility is making the desalination plant movable, thus avoiding that the brine builds up into a single location (as it keeps being produced by the desalination plant). Some such movable (ship-connected) desalination plants have been constructed.<ref>{{Cite web|url=https://www.theexplorer.no/solutions/waterfountain-innovative-floating-desalination-system/|title=Innovative floating desalination system|website=www.theexplorer.no}}</ref><ref>{{Cite web|url=https://waterfountain.no/|title=Oisann Engineering|website=Oisann Engineering}}</ref>

Brine is denser than seawater and therefore sinks to the ocean bottom and can damage the ecosystem. Brine plumes have been seen to diminish over time to a diluted concentration, to where there was little to no effect on the surrounding environment. However studies have shown the dilution can be misleading due to the depth at which it occurred. If the dilution was observed during the summer season, there is possibility that there could have been a seasonal thermocline event that could have prevented the concentrated brine to sink to sea floor. This has the potential to not disrupt the sea floor ecosystem and instead the waters above it. Brine dispersal from the desalination plants has been seen to travel several kilometers away, meaning that it has the potential to cause harm to ecosystems far away from the plants. Careful reintroduction with appropriate measures and environmental studies can minimize this problem.<ref>{{cite journal |last1=Yolanda Fernández-Torquemada |title=Dispersion of brine discharge from seawater reverse osmosis desalination plants |journal=Desalination and Water Treatment |date=March 16, 2009 |volume=5 |issue=1–3 |pages=137–145 |doi=10.5004/dwt.2009.576 |bibcode=2009DWatT...5..137F |hdl=10045/11309 |hdl-access=free }}</ref><ref>{{Cite journal|last1=Panagopoulos|first1=Argyris|last2=Haralambous|first2=Katherine-Joanne|date=2020-12-01|title=Environmental impacts of desalination and brine treatment – Challenges and mitigation measures|url=http://www.sciencedirect.com/science/article/pii/S0025326X20308912|journal=Marine Pollution Bulletin|language=en|volume=161|issue=Pt B|pages=111773|doi=10.1016/j.marpolbul.2020.111773|pmid=33128985|bibcode=2020MarPB.16111773P |s2cid=226224643|issn=0025-326X}}</ref>