One of the major difficulties in anaerobic wastewater treatment processes is the need to retain a sufficient quantity of active biomass in the anaerobic reactor. The use of membranes to achieve external solid/liquid phase separation will result in the retention of the biomass at the surface of the membranes. In this study, the Membrane Anaerobic System (MAS) was used to treat industrial wastewater from a palm oil mill. The MAS was subjected to increasing organic loading rates (OLR) and a total of six steady states were attained. The first steady state influent COD concentration was 39,910 mg/l increasing to the final or sixth steady state COD concentration of 68,310 mg/l. The efficiency of COD removal was between 91.7 to 94.2 percent with an average HRT of 3.03 days. The maximum OLR applied during the sixth steady state was 21.7 kgCOD/m3/d. The reactor mixed liquor suspended solids (MLSS) was between 50,000 to 57,000 mg/l while the percentage of the mixed liquor volatile suspended solids (MLVSS) was between 74 to 82 percent. A crossflow ultraftration (UF) module was used to filter the final effluent and simultaneously retain biomass in the anaerobic reactor. A clear final effluent was produced but membrane flux rate deterioration was observed due to membrane fouling. Membrane fouling could be minimised with faster crossflow feed velocities and regular membrane flushing.