Alternative designs of an aerated moving-bed biofilm reactor and a flat-sheet membrane module for a biofilm membrane bioreactor process have been investigated to overcome a membrane clogging problem and to determine the performance of a new membrane module. Double-deck aerated biofilm reactor with integrated designs of sludge hopper, thickener, and velocity-zone concept for particle settlement was evaluated for the suspended solid control and removal. Hydrodynamics of bubbling, liquid, and solid particles were arranged in the bioreactor to obtain a particle settlement. New membrane modules used under low suspended solid environment having smaller membrane gaps were evaluated for filtration performance and clogging problems for long-term operation. The average suspended solids concentration in the bioreactor effluent was 44.6 mg/L Relaxation applied with the membrane module provided the most optimum result for fouling control, and no clogging problems in the modules were observed in the system after continuous operation of 3 weeks. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 1291-1297, 2009