Concept The in situ microbial filter concept is to inject TCE-degrading microbes into the subsurface without nutrients. Naturally occurring microbes are grown in surface bioreactors, separated from their growth medium, resuspended in groundwater from the site, and then injected into the subsurface. Methylosinus trichosporium OB3b, a methanotroph, is currently employed. Schematic of one of several possible implementations of the biofilter concept. Contaminated groundwater, shown in increasing concentrations from yellow to dark orange, flows through an engineered biofilter where it is bioremediated to acceptable contaminant limits.
Monitoring wells provide performance measurement.
A key element of the concept is the subsurface filter implementation. A portion of the injected microbes attaches to the soil and forms a fixed-bed biofilter. The attached microbes oxidatively degrade TCE to harmless compounds as it is transported through the biofilter region by the flowing groundwater. An advantage of the restin g-state biofilter approach is that it can be engineered so that contaminated groundwater will enter the biofilter but exit clean. The microbial filter concept can be generalized, even though the current focus is on intercepting chlorinated ethene plumes.