Recent developments in thin-film composite reverse osmosis membrane systems

Desalination of seawater by reverse osmosis requires a membrane which approaches theoretical semipermeability and is sufficiently thin to provide transport of water at practical operating pressures and recovery rates. This objective has been achieved by the development of a family of thin-film composite membranes based on nitrogen-containing polymers supported on a fabric-reinforced porous supporting membrane. The membranes, packaged in the spiral-wound configuration, exhibit high water permeability, low salt permeability, thermal stability, resistance to micro-organisms, wet-dry, and chemical stability. Membranes of this type are currently employed for the conversion of seawater to potable water in the world's first large reverse osmosis plant in Jeddah, Saudi Arabia, trailer-mounted U.S. Army military units, off-shore drilling platforms, marine applications, and hand-powered emergency units. Reverse osmosis systems, employing thin-film composite membrane elements, are also in operation for the conversion of brackish to potable water and a variety of water-reuse applications for textile finishing, boiler water for electrical utilities, soft drink manufacturing, agricultural water, and reclamation of municipal waste water.