Reverse osmosis is the most sophisticated membrane liquid separation technology, in the feed water (concentrated solution) side of the operating pressure to overcome the natural osmotic pressure, when higher than the natural osmotic pressure of the operating pressure added to the concentrated solution side of the natural osmosis of water molecules in the direction of the flow will be reversed, the water molecules in the feed water (concentrated solution) part of the water molecules through the reverse osmosis membrane to become a dilute solution side of the purified water production; reverse osmosis equipment can block all soluble Reverse osmosis equipment can block all dissolved salts and molecular weight greater than 100 organic matter, but allows water molecules to pass through, reverse osmosis composite membrane desalination rate is generally greater than 98%, they are widely used in industrial pure water and electronic ultrapure water preparation, drinking water production, boiler feed water and other processes, the use of reverse osmosis equipment before the exchange of ions can be greatly reduced to the bottom of the operation of the water and wastewater discharges.