This paper presents the pilot plant studies on the biologically treated effluents from the pulp and paper and fermentation industry effluents by using two stage membrane treatment (Ultrafiltration(UF) and reverse osmosis(RO), (brackish water(BW) and seawater(:SW)) membranes). In the first part of the study, the combination of UF and RO treatment resulted in very high removals of COD, color and conductivity for the pulp and paper industry effluents. At the end of one single pass with SW membrane, the initial GOD, colour and conductivity values were reduced to 10-20 mg/l, 0-100 Pt-Co units and 200-300 mu s/cm, respectively. The influent, UF permeate, BW permeate and SW permeate conductivities were 6000-6700 mu s/cm, 5500-5900 mu s/cm, 1000-1500 mu s/cm and 200-300 mu s/cm, respectively. Almost complete colour removals were achieved in the RO experiments with SW membranes. RO studies with BW membranes were also performed to the same permeate from the first stage UF study. In the second part of the study, ultrafiltration and reverse osmosis membranes were evaluated for their suitability in separating color and COD from the different wastewater streams generated by the fermentation industry. Three different wastewater stream, including the anaerobic treatment plant effluents of plant A and B, the aerobic treatment plant effluent of plant B have been tested during the runs. The overall removal efficiencies of GOD, Color, Conductivity, NH3-N were found as 90-95%, 95-97%, 85-90% and 80-90% respectively with 85-90% recovery after UF and RO membranes for all these wastewater streams. Applying membrane technology to these complex industrial wastewaters, color problems of treatment plant effluents can be solved effectively. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.