INFLUENCE OF FILTRATION CONDITIONS ON THE PERFORMANCE OF NF MEMBRANESIN THE FILTRATION OF PAPER-MILL TOTAL EFFLUENT

Nanofiltration membranes were studied and their suitability for treatm ent of paper mill total effluent was evaluated. The membrane flux, its decline and retentions of various components were studied on a labora tory scale using a flat sheet module under different operation conditi ons. The results showed that during short filtrations temperature, pre ssure and how velocity had minor effects on the retention of the measu red components. Only the retention of monovalent ions (chloride) was s ignificantly dependent on the flow velocity and the ionic concentratio n on the surface of the membrane. With the Desal-5 membrane, however, temperature, pressure and how velocity were found to have a considerab le effect on the permeate flux. The critical flux of the membranes was dependent on the flow velocity. The higher the flow velocity, the hig her the pressure that could be used without a decrease in permeate flu x. pH had a considerable effect on the ability of the membranes to ret ain various species. Increasing the pH of the solutions improved reten tion ability of the membranes. An increase in salt concentration (Na2S O4 and NaCl) decreased the flux and led to a decrease in the retention s of COD and chloride. With the RO membrane (TFC ULP) changes in salt concentration did not significantly alter the retentions. Adjustment o f the filtration conditions is one way to improve the efficiency of NF membranes. Appropriate pretreatment of the waste water can also impro ve the flux and filtering efficiency. The permeates from the NF membra nes were adequately clean to be reused, for example, as shower waters. (C) 1997 Elsevier Science B.V.