MEMBRANE SEPARATION ACTIVATED-SLUDGE FOR RESIDUAL ORGANIC REMOVAL IN OIL WASTE-WATER

A hybrid membrane separation activated sludge process was investigated for treatment of residual organic matter in oily wastewater from an a utomobile engine manufacturing plant. A bench scale experiment was con ducted to identify the biodegradability of the residual organic matter in activated sludge reactors at various HRT (equal to SRT), such as 5 , 10, 20, 30 days. Removal efficiency of higher than 90% was obtained in terms of SCOD at more than 10 day HRT showing the possibility of bi ological treatment. Ultrafiltration test was also carried out for the residual organics using cross-flow membrane filtration system at trans membrane pressure (TMP) of 2.0 kg/cm(2). The membrane used for this ex periment was polysulfone hollow fiber membrane with 30,000 molecular w eight cut off. The rejection rate was around 10% in terms of TCOD. Thi s low rejection rate explains that the residual organics in the oil wa stewater are soluble and their MWCO size distribution might be less th an 30,000. However the combined membrane activated sludge process coul d maintain significantly high removal efficiency more than 95% for the residual organics in the oily wastewater. The enhancement in organic removal was estimated to be contributed to the increased biomass in th e system resulting in the reduction of the organic loading. (C) 1997 I AWQ.