Reverse osmosis (RO) is a process whereby water is passed through a membrane under pressure in cross-flow fashion. With its exceptional purifying efficiency, reverse osmosis is one of the most economical methods for the removal of up to 99% of impurities.
How does it work?
During reverse osmosis, feedwater is pumped past the input side of an RO membrane under pressure (typically 4-15 bar, 60-220 psi) in cross-flow fashion. Typically 15-30% of feedwater passes through the membrane as permeate and the exits the membrane as the concentrate that contains most of the salts, organics and essentially all particulates.
RO membranes are typically thin film polyamide and are stable over a wide pH range, however, they can be damaged by oxidizing agents such as chlorine, so pretreatment is usually required to protect the membrane. RO membranes are used to remove water contaminants and reject water contaminants that are less than 1 nm in diameter. Typically over 90% of ionic impurity, most organic impurity, and nearly all particulates, bacteria and bio-molecules are removed from the filtrate or permeate water; these are carried out of the RO module in a waste or concentrate water stream.