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 toxicity effects. A hollow fiber membrane bioreactor was investigated that involves a bundle of polypropylene fibers through which volatile organic compound contaminated air passes. The fibers are immersed in a recirculating nutrient/cosubstrate solution. Batch culture experiments were performed with a mixed culture that could cometabolize TCE with toluene as a primary substrate. 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 inoculated into the hollow-fiber membrane bioreactor. Initially toluene was supplied to the reactor to build a sufficient biomass density on the fibers. After steady-state toluene removal was achieved, TCE was added to the gas phase of the reactor. Toluene was added in three different configurations: (1) As a mixture with TCE in the gas phase; (2) by pulsing into the gas phase; or (3) to the liquid phase. This paper investigates which reactor configuration is most favorable for cometabolism of toluene and TCE.