Recovery of wastewater from the pulp and paper industry by cellulose acetate reverse osmosis membrane.

The high salt content and color are regarded as a major challenge to the reuse of industrial wastewater. In the present study, the application of cellulose acetate reverse osmosis (RO) membrane in combination with microfiltration (MF), ultrafiltration (UF), or nanofiltration (NF) process was investigated in the purification of biological and Fenton treated pulp and paper wastewater. In the first step, the effect of pH and inlet pressures on the membrane fouling was investigated. The minimum flux decline caused by fouling were obtained at pH of 10 and inlet pressure of 40 bar. Under the optimized conditions, 82 % chemical oxygen demand (COD) and 96 % color removal were achieved. However, total hardness and conductivity were still high. In the second step, NF-RO system was used to provide better permeate quality. Negligible concentrations of conductivity and hardness were obtained, and iron, calcium, magnesium, potassium and sodium ions with the removal efficiencies of 99.93 %, 99.97 %, 99.96 %, 99.93 % and 99.70 % were achieved, respectively. Moreover, the adsorption of pollutants on the membrane surface and the blockage of the membrane hole were reduced effectively, thus extending the service life of the membrane. Zero discharge of wastewater can be achieved by reuse of wastewater.