How Does a Reverse Osmosis System Desalinate Water?

In normal osmosis, water moves from a dilute solution to a concentrated one through a membrane. Reverse osmosis (RO) reverses this by applying pressure (typically 55–80 bar for seawater) to the salty side, forcing water molecules through the membrane while rejecting up to 99.5% of dissolved salts. The membranes are usually thin-film composite polyamide, wound in spiral modules. Pre-treatment (sediment filtration, chemical dosing) protects the membranes from fouling. A large desalination plant, such as the Sorek B facility in Israel, can produce over 500,000 m³ of fresh water per day. Energy recovery devices capture the pressure from the brine stream, reducing energy use to as low as 3 kWh per cubic metre.