A review of oily wastewater treatment using ultrafiltration membrane: A parametric study to enhance the membrane performance

The industries like petroleum refining, petrochemicals, metallurgical, oil & gas, etc., generate a substantial volume of oily wastewater, and it is recognized as a potential threat to the environment. The topic of oily wastewater treatment is very topical and important to major industry developments such as shale oil and gas. Among the techniques employed, the treatment of oily wastewater using polymeric ultrafiltration membrane (UFM) has emerged as a cost-effective technique with ease of operation as well as high separation efficiency over the conventional oily wastewater treatment methods. The major limitation of the UFM technique is mainly due to the fouling of membranes because of the accumulation of tiny oil droplets on the surface and blockage of membrane pores. Therefore, the enhanced wettability (i.e., hydrophilicity) and the antifouling behavior of membranes are the key parameters to improve the performance of UFMs. In this review, we briefly highlight the parametric effects on the performance of UFM performance, which includes the (i) composition of the membrane related to the blend-ratio of several additives (namely, polymeric, inorganic, grafted polymers, etc.) (ii) operating conditions (pH, temperature, salinity, oil concentration, and cross-flow velocity of feed, the viscosity of casting solution and salinity of the coagulation bath, etc.) and (iii) process optimization. The review further provides an insight into the fouling of membranes using oily wastewater. Finally, the present review emphasizes the challenges faced for commercial applications of UFM, economic aspects as well as the range of strategies for the researchers to follow.