COUPLING TRANSPORT AND BIODEGRADATION OF TOLUENE AND TRICHLOROETHYLENE IN UNSATURATED SOILS

Trichloroethylene (TCE), a commori groundwater pollutant generally res istant to aerobic biodegradation, can be cometabolized in the presence of another compound such as toluene. The coupled transport and biodeg radation of TCE and toluene was investigated and modeled in laboratory soil columns. Toluene biodegradation was linked to microbial growth u sing Monod kinetics, while TCE degradation was described using Michael is-Menten kinetics modified to account for changing enzyme levels. Bio degradation of TCE was modeled as a mass fraction of the toluene degra dation rate. Both growth and decay were incorporated into the equation s to model microbial population dynamics. With the exception of the in itial biomass, a single set of parameters to describe both degradation functions was obtained from independent soil batch experiments. Physi cal parameters were obtained from sterile soil columns. The initial bi omass declined from the inlet to the outlet side of the chamber. Tolue ne was fully degraded in the soil column with the majority occurring c losest to the inlet chamber. A substantial amount of TCE was not degra ded because it diffused faster and was transformed at a lower rate tha n toluene.