The evaporative recovery is a very energy intensive process. Approximately 970 BTU's are required to evaporate one pound of water at standard atmospheric pressure. Additional energy may also be required to raise the temperature of the solution to its boiling point. The membrane allows water molecules to pass through, but blocks metallic salts and additives. Like evaporators, RO works on most plating baths and rinse tanks.
Most RO systems consist of a housing that contains a membrane and feed pump.
Diluted or concentrated rinse waters are circulated through the membrane at pressures greater than aqueous osmotic pressure. This action results in the separation of water from the plating chemicals. The recovered chemicals can be returned to the plating bath for reuse and the permeate, which is similar to the condensate from an evaporator, can be used as make-up water. RO units work best on dilute solutions. The design and capacity of an RO unit is dependent upon the type of chemicals in the plating solution and the dragout solution rate.