Desalination

Desalination is the artificial process of turning salt water, most often seawater, into fresh water by removing its dissolved salts and minerals, and it now supplies roughly 95 million cubic meters of fresh water a day worldwide, especially in arid regions short of natural fresh water. Two main methods dominate: thermal processes such as multi-stage flash distillation boil and then condense seawater to leave the salt behind, while membrane processes, chiefly reverse osmosis, force water through a semipermeable membrane under pressure that lets water through but blocks dissolved salts; reverse osmosis has become the leading method because it scales and uses energy more efficiently than thermal distillation. Ancient writers such as Aristotle already noted that seawater left fresh condensate when evaporated, and sailors used shipboard distillation for centuries afterward, but industrial-scale desalination began with steam-powered multiple-effect evaporators in the 19th century, followed by the United States government's 1955 Office of Saline Water and the emergence of reverse osmosis as a practical technology in the late 1960s and 1970s. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/