Microbial degradation of volatile anthropogenic organic chemicals. Final report

Experiments were conducted to study the degradation of trichloroethylene (TCE) by bacteria able to grow on methane (methanotrophs) and to consider specific aspects relative to the ultimate design of a bioreactor to purify air streams contaminated with TCE that could originate from air stripping of contaminated aquifers. A procedure was investigated that consisted of initially sorbing TCE from the gas phase to granular activated carbon (GAC). The GAC then was treated by first extracting TCE from the GAC by using methanol and then providing the methanol containing TCE to methanotrophs. The experiments indicated that neither TCE nor methane could be significantly degraded by methanotrophs in the presence of a high but nontoxic concentration of methanol in water. A study was conducted to determine whether there is a concentration of TCE (a threshold) below which methanotrophs growing on methane would not be able to degrade TCE. TCE was degraded below a concentration of about 2 parts per trillion, and thus no threshold was found. The degradation of TCE by methanotrophs in the presence of different packing materials was assessed. The results showed that some packing materials inhibited TCE degradation unless they were first washed with an aqueous solution of ethylenediaminetetraacetic acidmore » (EDTA).« less