Domestic wastewater treatment using an anaerobic bioreactor coupled with membrane filtration

A laboratory scale anaerobic bioreactor coupled with a membrane filtration device was investigated for treating domestic wastewater at ambient temperature. The system was capable of achieving over 97% chemical oxygen demand (COD) removal with effluent of COD less than 20 mg l−1 on the average at volumetric organic loadings ranging from 0.5 to 12.5 kg m−3 d−1, and had a strong tolerance to wastewater temperature variation. Due to the effective retention of biomass within the bioreactor with a membrane, the sludge concentration in the anaerobic bioreactor could be kept at a high level between 16 and 22.5 g l−1. Membrane permeability was largely affected by intermittent suction mode and membrane flux. A stable operation could be maintained continuously over 2 weeks without any cleaning at a operational mode of 4 min pumping and 1 min non-pumping, and a membrane flux of 5 l m−2 h−1. COD mass balance analysis showed that about half of the influent COD was converted to methane gas.