Current reverse osmosis technology was applied to the treatment and demineralization of secondary effluents to determine what operational problems may occur, and develop methods of alleviating them. Two parallel reverse osmosis systems, with 50 sq ft. spiral-wound reverse osmosis modules, were operated and results for activated sludge effluent versus activated carbon treated activated sludge effluent were compared. Fouling problems were encountered for which previously developed cleaning techniques were ineffective. An enxyme-based detergent technique was developed which alleviated the problem and restored performance. The size of the brine spacers affected only the pressure drop across the modules, and not the overall performance. Also the quantity of water handled would, over a 3 year period, be substantially more than could be handled by standard flux-high selectivity membranes. (WRSIC abstract)