Development of Design Factors for Reverse Osmosis Concentration of Pulping Process Effluents

Abstract

Laboratory, pilot and large field demonstration units were used concurrently to develop engineering design factors for concentration treatment of four different pulp and paper industry waste streams by reverse osmosis. Eleven, half-inch diameter tubular modules with cellulose acetate membranes were operated in parallel under closely controlled conditions of flow rate (to 5 1/2 gallons/minute per module); velocity (to 9 feet/second); concentration (tap water controls to 10% waste liquor solids); pH (2.5–7.5); temperature (20°C to 40°C); viscosity (0.8–2.0 cp); and time of continuous operation (to ten days/run). Detailed data obtained include turbulence (N _Re ); viscosity; osmotic pressure; pressure drop; permeation resistance; and effect of reverse osmosis in terms of rejections of dissolved solids, BOD, COD, and Color (OD) for the individual wastes processed. Design factors developed from these data include pumping energy per unit volume; hydrolysis rates on cellulose acetate; concentration polarization; fouling rates by microbiological growth and other surface accumulations; and membrane compaction rates. Auxiliary information is being developed from these studies to provide a firm base upon which methods of pretreatment and of operation can be developed to maintain sustained operation with minimum membrane fouling and also methods and routines for systematic cleanups where required.