Membrane processes gain favor for water reuse

The author describes tertiary treatment research and demonstration projects in U. S. A. and gives tabulated preliminary cost estimates for sewage and industrial waste waters. The cost of removing organic and inorganic nutrients by tertiary treatment compares favourably with the cost of secondary treatment processes. Reverse osmosis used to treat paper mill effluents has reduced total dissolved solids, COD and colour by 95 per cent. Further studies using reverse osmosis have been made on sewage and hospital, industrial and radioactive wastes. The author suggests that special membranes are required for the retention or passage of specific materials. Membranes are susceptible to fouling by trace contaminants which reduce flow., md the anthor describes how membrane modules have been cleaned successfully with chemical solutions.