Transport issues and bioremediation modeling for the in situ aerobic co-metabolism of chlorinated solvents

For aerobic co-metabolism of chlorinated solvents to occur, it is necessary that oxygen, a primary substrate, and the chlorinated compound all be available to an appropriate microorganism--that is, a microorganism capable of producing the nonspecific enzyme that will promote degradation of the contaminant while the primary substrate is aerobically metabolized. Thus, the transport processes that serve to mix the reactants are crucial in determining the rate and extent of biodegradation, particularly when considering in situ biodegradation. These transport processes intersect, at a range of scales, with the biochemical reactions. This paper reviews how the important processes contributing to aerobic co-metabolism of chlorinated solvents at different scales can be integrated into mathematical models. The application of these models to field-scale bioremediation is critically examined. It is demonstrated that modeling can be a useful tool in gaining insight into the physical, chemical, and biological processes relevant to aerobic co-metabolism, designing aerobic co-metabolic bioremediation systems, and predicting system performance. Research needs are identified that primarily relate to gaps in our current knowledge of inter-scale interactions.