Aluminum dioxide (Al2O3) flat-tubular ceramic membrane was applied in a novel staged anaerobic fluidized bed ceramic membrane bioreactor (SAF-CMBR) for low-strength wastewater treatment. Granular activated carbon (GAC) particles were fluidized by bulk recirculation through the membrane reactor to control membrane fouling without any biogas sparging. The SAF-CMBR was operated for 350 days at 25 degrees C with total hydraulic retention time (HRT) between 1.3 and 2.1 h. A net permeate flux of 22 L/m(2) h was achieved during the reactor operation combined with periodic maintenance cleaning using 25 mg/L of sodium hypochlorite solution under GAC fluidization. The overall chemical oxygen demand (COD) removal efficiency was 93%; with average SCOD was less than 30 mg/L in membrane permeate. Energy requirement to operate the SAF-CMBR was 0.024 kWh/m(3) and it was only 10% of the electrical energy converted from methane produced by the reactor. Biosolids production averaged 0.01 g volatile suspended solids per g COD removed. With SAF-CMBR, microbial classification revealed that anaerobic treatment was achieved mainly by microbial communities grown on the GAC particles fluidized in which propionate-degrading syntrophs, aceticlastic/DIET-dependent CO2 reduction methanogens Methanothrix and exoelectrogenic Geobacter were dominated.