Reverse osmosis (RO) is a water treatment technology that uses a semipermeable membrane to separate dissolved salts and other impurities from water. It works by applying high pressure to the water to overcome osmotic pressure, which is the natural tendency of water to move through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration. The high pressure pushes the water molecules through the membrane, leaving behind the dissolved salts and other impurities, which are then flushed out as waste. Reverse osmosis is commonly used in the semiconductor industry for the production of ultra-pure water, which is used in various processes such as cleaning, rinsing, and chemical dilution.