Treatment of the wastewater from a petrochemical industry has been investigated using a submerged membrane bioreactor (MBR). A bench scale MBR system with an anoxic/aerobic concept and flat sheet MF membranes were used in the study. The testing system ran continuously (24-h) over 2 months. Trial, on different membrane fluxes and hydraulic retention time (HRT) were conducted and the effect of aeration on nitrification was investigated. The results showed that the product quality consistently met the requirement for discharge while segregation of the streams with high TDS was required to reclaim the water for reuse. A flux of 12.5 L m(-2) h(-1) (LMH) was sustainable and HRT of 13 h was applicable. The current anoxic volume ratio of 40% in this system might be further increased to reduce the energy consumption in the aeration tank. Membrane permeability could be, fully recovered after cleaning. In addition, there was no foaming issue in the process. It was concluded that it was feasible to treat the wastewater using Submersed MBR technology. (c) 2007 Elsevier B.V. All rights reserved.