Membrane bioreactor for cometabolism of trichloroethene air emissions

Biofilters have been of limited use for cometabolism of chlorinated organic compounds, such as trichloroethene (TCE), due to enzyme inhibition or toxi city effects. A hollow fiber membrane bioreactor was investigated that invo lves a bundle of polypropylene fibers through which volatile organic compou nd contaminated air passes. The fibers are immersed in a recirculating nutr ient/cosubstrate solution. Batch culture experiments were performed with a mixed culture that could cometabolize TCE with toluene as a primary substra te. No inhibition or inquiry to the toluene degrading ability was observed at up to 15 mg L-1 toluene or up to 1.5 mg L-1 TCE. The culture was inocula ted into the hollow-fiber membrane bioreactor. Initially toluene was suppli ed to the reactor to build a sufficient biomass density on the fibers. Afte r steady-state toluene removal was achieved, TCE was added to the gas phase of the reactor. Toluene was added in three different configurations: (Ij A s a mixture with TCE in the gas phase; (2) by pulsing into the gas phase; o r (3) to the liquid phase. This paper investigates which reactor configurat ion is most favorable for cometabolism of toluene and TCE.