The impact of microbial population dynamics on the transport and biodegradation of organic compounds

The impact of microbial population dynamics on the biodegradation and transport of organic compounds was evaluated in this study. At the laboratory-scale, results from miscible-displacement studies demonstrated that transport and biodegradation behavior in systems with increasing biologic diversity and population density variation was considerably more variable. Biokinetic parameters associated with biodegradation of the target compound were found to be considerably different in batch versus flow-through systems. While growth rates were always higher in the flow-through systems, the impacts on microbial lag and cell yield were opposite in different soils. In homogeneous sand, microbial lag was longer and column cell yields were larger than values reported under batch conditions. However, in more heterogeneous soils, microbial lag was shorter and column yields were smaller in the flow-through systems. This was determined in part using a one-dimensional contaminant transport and biodegradation model that incorporates the effects of microbial lag, inhibition, bacterial transport and nonuniform distribution of microbes, which was developed as a part of this study. In the second part of this study, a contaminant transport and biodegradation model incorporating linear biodegradation was applied to recovery data from small input pulses of biotracers at the field scale. One field site was low in oxygen and fairly homogeneous. The other had been subjected to a surfactant flush that enhanced oxygen concentrations, and thus microbial population densities, near the injection wells. Application of this model allowed for quantitative determination of the spatial distribution of microbial activity at the field sites