Treatment of petroleum refinery wastewater using crossflow and immersed membrane processes

Due to the dwindling water resources in the Kingdom of Saudi Arabia and increasing stringencies on the discharge of effluents, two pilot-scale membrane processes were installed in Riyadh petroleum refinery in order to treat wastewater discharged by the selected refinery after an API separator. One of the membrane processes was performed in a crossflow mode, while the other process was performed in an immersed mode. Results on permeate flux of both processes showed that the immersed membrane process was producing a stable flux value (more than 50 l/m² h) throughout the investigation period (more than 800 h). On the other hand, permeate flux of the crossflow membrane process was noticed to steadily decline after 600 h of running period. In terms of oil and grease contents, both membrane processes produced permeates that contained less than 1.4 mg/l. The immersed membrane process was found to be a potential process for treating oily wastewater, where the permeate flux was found to be almost stable at its initial value throughout the investigation. Moreover, the immersed membrane was effectively cleaned using a commercial detergent.