Experimental investigation of oily wastewater treatment using combined membrane systems

摘要

Investigations were carried out for purification of oily wastewater by a combined ofnultrafiltration/reverse osmosis (UF/RO) processes. Laboratory-scale UF using polysulfone (PS) andnpolyacrylonitrile (PAN) membranes were employed with typical oily wastewater collected fromnAPI unit of Tehran refinery. The PAN membrane showed higher rejection, more permeation fluxnand less fouling resistance than the PS membrane. Both membranes produced permeate with oilnand grease contents generally less than 5 ppm. Rejection of chemical oxygen demand (COD) andnbiological oxygen demand (BOD5) were found to be 65% for UF treatment. In this work, Hermia’snmodels were used to investigate the fouling mechanism involved in UF of the oily wastewater.nThe results showed that the best fit to experimental data corresponds to the cake layernformation model followed by the intermediate blocking model for both the UF membranes.nFor further treatment of the UF permeates, RO was applied using a thin film composite polyamidenmembrane. The rejection of COD, BOD5 and total dissolved solid (TDS) after UF/RO treatmentnincreased up to 98%, 98% and 95%, respectively. The results showed that the final permeatenhas very high quality and even better than that is currently introduced to the cooling towersnin Tehran refinery.