Reverse osmosis is the most precise membrane-based liquid separation technology. An operating pressure is applied to the feed water (concentrated solution) side to overcome the natural osmotic pressure. When an operating pressure higher than the natural osmotic pressure is applied to the concentrated solution side, the natural osmotic flow direction of water molecules is reversed. Part of the water molecules in the feed water (concentrated solution) pass through the reverse osmosis membrane to become purified product water on the dilute solution side; reverse osmosis equipment can block all dissolved salts and organic substances with a molecular weight greater than 100, while allowing water molecules to pass through. The desalination rate of reverse osmosis composite membranes is generally more than 98%. They are widely used in processes such as industrial pure water and electronic ultrapure water preparation, drinking pure water production, and boiler feed water preparation. Using reverse osmosis equipment before ion exchange can significantly reduce the discharge of operating water and wastewater.