Treatment of oil sands process-affected water with ceramic ultrafiltration membrane: Effects of operating conditions on membrane performance

Abstract

This study investigated the performance of 1kDa ceramic ultrafiltration membrane for the removal of inorganic and organic compounds from oil sands process-affected water (OSPW) generated after thermal operations of heavy oil recovery in Alberta, Canada. The OSPW was pretreated with alum coagulant, and the effect of operating conditions on subsequent membrane filtration was studied. While permeate flux increased with increasing trans-membrane pressure (TMP) from 1.4bar to 3.5bar, greater permeate flux decline was observed at TMP of 3.5bar due to increased accumulation of foulants at the membrane surface. The membrane filtration performed at cross-flow velocity (CFV) of 0.2L/min was characterized by the lowest initial and steady-state permeate fluxes and by the highest normalized flux decline compared to higher CFVs. This effect was attributed to lower turbulence at the membrane surface which might have promoted the buildup of contaminants. According to the resistance-in-series model, no irreversible membrane fouling was observed when OSPW was pretreated with coagulation–flocculation–sedimentation. The pore blocking and cake layer formation dominated at the beginning of filtration, whereas cake layer formation was the primary fouling mechanism at later stages. The final membrane permeates met the requirements for the high pressure-driven membrane processes (i.e., nanofiltration and reverse osmosis) with respect to turbidity and silt density index (SDI15) values. Up to 38.6±2.7% (depending on TMP and CFV values) of chemical oxygen demand (COD) was removed, and the removal percentages of the acid extractable fraction (AEF) and naphthenic acids (NAs) were less because of the small sizes of NAs and other organic compounds contributing to the AEF as compared to the membrane pore sizes.