Demethanization of aqueous anaerobic effluents using a polydimethylsiloxane membrane module: Mass transfer, fouling and energy analysis

The performance, fouling and feasibility of a polydimethylsiloxane hollow fibre membrane module for in situ methane degasification from the effluent of an Expanded Granular Sludge Bed anaerobic reactor has been investigated. Experiments at different operational conditions were carried out (liquid flow, sweep gas flow and vacuum pressure) with maximum removal efficiency (77%) at lowest flow-rate (0.4 L h−1), highest vacuum gauge pressure (−800 mbar) and liquid flowing in lumen side. Mass transport analysis denoted a considerably higher methane transfer than that predicted (attributed to liquid oversaturation). An enhancement factor for liquid phase has been proposed to correlate the experimental results. Long-term experiments were also performed in order to determine the possible influence of fouling on the module performance, and it showed that relatively frequent cleaning with water might be carried out to ensure preservation of the membrane efficiency. Characterization of water quality before and after membrane module was carried out to elucidate fouling causes. Energy balance analysis evidenced that energy production exceeded the system energy requirements. A substantial reduction of CO2 equivalent emissions showed the positive environmental impact of this technology.