Hybrid reverse osmosis — ultrafiltration membranes

Abstract A new group of asymmetric non-cellulosic membranes having a performance intermediate between that of a conventional RO membrane and an ultrafilter has been developed. Its main characteristics are high fluxes (4–10 m 3 /m 2 day) at low pressures (6–10 at) and moderate rejections for various salts. From 200 mg/l solutions of NaNO 3 , Na 2 SO 4 and KH 2 PO 4 rejections up to 40%, 70% and 90%, respectively, were obtained. The new membranes can withstand large variations in pH (1 to 13) and have excellent chemical and biological stability. The membranes have been tested in a mobile SUF pilot plant operating on oxidation pond effluent. High rejections for BOD, COD, bacteria and suspended solids as well as a 20% reduction in salinity have been obtained.