Membrane filtration of chlorination and extraction stage bleach plant effluent in Indian paper Industry

The present study was carried out for the treatment of effluent from the chlorination and extraction stages of a bleach plant at an Indian pulp and paper mill. The effluents were taken from an integrated paper mill employing OCEOPHH sequence for the bleaching of hardwood pulp. Effluent was treated via ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Thin film composite spiral-wound modules, having cross flow membranes composed of polysulfone and polyamide, were used in the study. Three initial inlet pressures were used for the UF and NF; 6.8, 10.3, and 13.7 bar. For RO initial inlet pressures of 10.3 bar, 13.7 bar and 17.2 bar, were taken in different trials. The retentate from each experiment was recycled back to the feed and retreated until the inlet pressure increased to the maximum cut-of pressure for each membrane. The UF permeate was fed to the NF, which was subsequently fed to the RO. Variations in the trans-membrane pressure and permeate flux were assessed. The removal of pollutants and fouling indices were obtained for each membrane at each initial inlet pressure.