Microbial removal of halogenated methanes, ethanes, and ethylenes in an aerobic soil exposed to methane

Contamination of ground water with halogenated aliphatic hydrocarbons threatens this source of drinking water. In order to study microbial processes that may enhance the removal of these compounds, Lincoln fine sand was exposed to an atmosphere containing methane (4%) to enrich microorganisms capable of growth on this gaseous hydrocarbon. The methane-enriched soil was then tested to determine whether the enriched microbes could remove seven halocarbons from aqueous solution. Removal of dichloromethane. trans-1,2-dichloroethylene, chloroform, 1,2-dichloroethane, trichloroethylene, and 1,1,1-trichloroethane was significantly different in methane-enriched soil compared to non-enriched soil (ANOVA, 95% significance level). Tetrachloroethylene was not removed. Autoclaving the methane-enriched soil inhibited completely the removal of all the compounds. Once the soil was enriched with methane, its presence in the headspace was not required for removal of several of the compounds but methane was required for their complete removal. These results suggest that methane stimulation of microbial communities may be an alternative treatment technology for bioremediation of contaminated subsurface soils and ground water.