Reverse Osmosis

Reverse osmosis is a water purification process that forces water through a semi-permeable membrane by applying pressure to overcome natural osmotic pressure, leaving dissolved and suspended chemical and biological substances behind while purified water passes through, most familiar in desalinating seawater into drinking water. The French physicist Jean-Antoine Nollet first observed the underlying phenomenon of osmosis through a semi-permeable membrane in 1748, but investigation into reversing that pressure to desalinate water did not begin until 1950 at the University of California, Los Angeles, and mid-1950s experiments there and at the University of Florida produced desalinated water whose flow rate was too low to be commercially useful. Sidney Loeb and Srinivasa Sourirajan later developed an asymmetric membrane that made the process practical, and John Cadotte's interfacial-polymerization technique produced high-flux membranes; Cape Coral, Florida became the first United States municipality to use reverse osmosis at scale in 1977, treating 11.35 million liters of water a day, and by 2019 roughly 16,000 desalination plants were operating worldwide, together producing about 95 million cubic meters of water daily.