DICHLOROETHANE REMOVAL FROM GAS STREAMS BY AN EXTRACTIVE MEMBRANE BIOREACTOR

A novel extractive membrane bioreactor (EMB) system, in which a silicone rubber membrane separates a contaminated gas stream from an aerated biomedium, extracted and biodegraded 1,2-dichloroethane (DCE) from a gaseous waste stream. Selective transfer of the organic compound takes place through the silicone membrane to the biomedium, where biodegradation occurs. At a gas flow rate of 770 mL min(-1) and an average DCE concentration of 0.65 mg L(-1), the EMB, with 2.5 m(2) of membrane surface contained in a spirally wound module, degraded 91% of the DCE. A biofilm grew on the membrane surface and caused a 600 mbar pressure drop at steady state conditions. The chloride ions released by DCE mineralization were 99% of the stoichiometric amount, while 60% of the total amount of carbon crossing the membrane as DCE was bioconverted to CO2. The overall mass transfer coefficient across the membrane in the absence of microbial activity was (0.8-1.3) x 10(-6) m s(-1) and was controlled by the liquid film resistance. Extensive biofilm growth significantly lowered the DCE flux. Comparison of the EMB to a direct bioscrubbing process showed that the EMB system has superior volumetric efficiency.