Reverse osmosis (RO) is a point-of-use treatment system. The simplest reverse osmosis (RO) system consists of a housing for a semi-permeable membrane, a storage tank, and a separate faucet. The membrane allows water to pass through and collect in the storage tank.
Untreated water is forced through the membrane. The contaminants being treated by the unit do not pass through the membrane and are removed as waste.
It is not practical to treat all water entering a home with an RO system because four gallons of raw water into the RO treatment system produce about one gallon of treated water. Therefore, the treated water is often used only for drinking and cooking.
Adapted from: Wagenet,L., K. Mancl, and M. Sailus. (1995). Home Water Treatment. Northeast Regional Agricultural Engineering Service, Cooperative Extension. NRAES-48. Ithaca, NY.