Biofilm Reactors for Treatment of Gas Streams Containing Chlorinated Solvents

Abstract

Air streams contaminated with chlorinated solvents are increasingly common as by‐products of air‐stripping and soil‐vapor‐extraction operations. This research investigated treatment of such gas streams with a bioreactor that supported the growth of methanotrophic bacteria. These bacteria cometabolize many chlorinated solvents. Trichloroethylene (TCE) and 1,2‐dichloroethane (DCA) were selected as model contaminants. Removals ranged from 20% to 80% at influent concentrations of 300–1,000 μg/L of air and packed‐bed gas‐resident times of 5–12 min. Biofilm models were able to describe bioreactor performance well. Pseudo‐first‐order rate constants from reactor modeling were considerably smaller than those measured in batch systems, suggesting that much of the biofilm was inactive, which also was supported by methane‐removal data. Enzyme competition between methane and chlorinated solvents and toxicity from chlorinated solvent metabolites both appeared significant.