The oily wastewaters from oil refineries and oil distribution centers are one of the most important environmental pollutants in recent decades. In this research, the performance of different membranes in oily water treatment has been reviewed and furthermore, the performance of nanostructured polyethersulfone (PES) hollow fiber membranes in oil/water separation process has been investigated and the effect of operating parameters such as pressure, oil concentration and cross flow velocity of feed on the membrane performance is studied. Increasing the pressure makes more membrane compactness, therefore the optimum operating conditions for oil separation are P = 1, low feed concentration and high cross flow velocity. All the fabricated membranes showed complete separation of oil from water. Therefore, they can effectively be used in oily water treatment. Membrane #M1 with the pore size of 15.6 nm showed the best permeation flux of 12.4 (L/m2/hr) with 100% oil rejection.
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