Reverse osmosis, also known as ultrafiltration, is a membrane separation desalination method that uses a semipermeable membrane to separate seawater from freshwater. Under the action of external pressure applied by a high-pressure pump, water reversely permeates from the high-concentration side to the low-concentration side, intercepting solutes such as salt and organic matter to achieve separation, purification and concentration of freshwater and seawater. The energy consumption of reverse osmosis is only 1/2 of that of electrodialysis and 1/40 of that of distillation. Its main development trends are to reduce the operating pressure of reverse osmosis membranes, improve the recovery rate of reverse osmosis systems, cheap and efficient pretreatment technology, and enhance the system's anti-pollution ability.
