Reverse osmosis

== History ==
A process of osmosis through semi-permeable membranes was first observed in 1748 by [[Jean-Antoine Nollet]]. For the following 200 years, osmosis was only a laboratory phenomenon. In 1950, the [[University of California at Los Angeles]] (UCLA) first investigated osmotic [[desalination]]. Researchers at both UCLA and [[University of Florida]] desalinated seawater in the mid-1950s, but the [[flux]] was too low to be commercially viable.<ref>{{cite journal |title=The early history of reverse osmosis membrane development|doi=10.1016/S0011-9164(98)00122-2 |author=Glater, J. |year=1998 |journal=Desalination |volume=117 |issue=1–3 |pages=297–309 }}</ref> [[Sidney Loeb]] at UCLA and Srinivasa Sourirajan<ref>{{cite journal|author=Weintraub, Bob|url=https://drive.google.com/file/d/1hpgY6dd0Qtb4M6xnNXhutP4pMxidq_jqG962VzWt_W7-hssGnSxSzjTY8RvW/edit?usp=sharing |title=Sidney Loeb, Co-Inventor of Practical Reverse Osmosis|journal=Bulletin of the Israel Chemical Society|date=December 2001| issue =8|pages= 8–9}}</ref> at the [[National Research Council of Canada]], Ottawa, found techniques for making asymmetric membranes characterized by an effectively thin "skin" layer supported atop a highly porous and much thicker substrate region. John Cadotte, of [[Filmtec corporation]], discovered that membranes with particularly high flux and low salt passage could be made by [[interfacial polymerization]] of [[M-Phenylenediamine|''m''-phenylene diamine]] and trimesoyl chloride. Cadotte's patent on this process<ref>Cadotte, John E. (1981) "Interfacially synthesized reverse osmosis membrane" {{US Patent|4277344}}</ref> was the subject of litigation and expired. Almost all commercial RO membrane is now made by this method. By 2019, approximately 16,000 [[desalination]] plants operated around the world, producing around {{convert|95|e6m3/day|e9usgal/day|abbr=off}}. Around half of this capacity was in the Middle East and North Africa region.<ref>{{cite journal |last1=Jones |display-authors=etal |first1=Edward |title=The state of desalination and brine production: A global outlook |journal=Science of the Total Environment |date=20 March 2019 |volume=657 |pages=1343–1356 |doi=10.1016/j.scitotenv.2018.12.076|pmid=30677901 |bibcode=2019ScTEn.657.1343J |s2cid=59250859 }}</ref>

[[File:Northcapecoral-RO.jpg|thumb|RO production train, North Cape Coral Reverse Osmosis Plant]]In 1977 [[Cape Coral]], Florida became the first US municipality to use RO at scale, with an initial operating capacity of 11.35&nbsp;million liters (3&nbsp;million US gal) per day. By 1985, rapid growth led the city to operate the world's largest low-pressure RO plant, producing 56.8&nbsp;million liters (15&nbsp;million US gal) per day (MGD).<ref>[http://www.capecoral.net/department/utilities_department/docs/2012_Citywide_CCR.pdf 2012 Annual Consumer Report on the Quality of Tap Water] {{Webarchive|url=https://web.archive.org/web/20160304001506/http://www.capecoral.net/department/utilities_department/docs/2012_Citywide_CCR.pdf |date=4 March 2016 }}. City of Cape Coral</ref>