In this paper, results of an experimental study on separation of oil from actual and synthetic oily wastewaters with mullite and mullite-alumina tubular ceramic membranes are presented. Mullite and mullite-alumina microfiltration (MF) symmetric membranes were synthesized from kaolin clay and alpha-alumina powder. The effects of different operating parameters such as pressure (0.5-4 bar), cross flow velocity (0-2 m/s), temperature (15-55 degrees C), oil concentration (250-3000 ppm) and salt concentration (0-200 g/L) on permeation flux (PF), fouling resistance (FR), fouling and rejection (R) of mullite and mullite-alumina membranes for treatment of synthetic wastewaters were investigated. In order to determine the best operating conditions, 250-3000 ppm condensate gas in water emulsions was employed as synthetic oily wastewaters using mullite membrane. At the best operating conditions (3 bar pressure, 1.5 m/s cross flow velocity and 35 degrees C temperature), performance of mullite and mullite-alumina membranes for treatment of real and synthetic wastewaters were also compared. The results for treatment of emulsions showed that the mullite ceramic membrane has the highest R (93.8%) and the lowest FR (28.97%). Also, the mullite-alumina ceramic membrane with 75% alumina performs high PF (244 L/m(2) h) and low R (81.3%). Also for all the membranes, R for the real wastewater is lower than that for the synthetic wastewaters. (C) 2010 Elsevier B.V. All rights reserved.