To ensure effluent quality in the treatment of high-strength organic waste and enhance CH(4) production, this study investigates the applicability of process optimization and a Submerged anaerobic membrane bioreactor (SAMBR) for a two-phase anaerobic digestion (TPAD) system. The use of response surface methodology (RSM) suggests that the optimum conditions for maximum volatile fatty acids (VFA) production were a hydraulic retention time (HRT) of 2.01 days and a substrate concentration of 29.30 g/L based on chemical oxygen demands (COD). A confirmation experiment showed that an empirical model could predict a VFA increase of 76% under the proposed conditions with a relative error of 4%. SAMBRs could convert the VFA in acidogenic effluent to CH(4) with an average production rate of 0.28 m(3)/m(3)/d in an HRT of 14 days. All of the SAMBRs could achieve COD removal rates of over 99% by the increased solid retention time and secondary membrane formation. (C) 2009 Elsevier Ltd. All rights reserved.