PNNL

Abstract

The incorporation of microbial processes into reactive transport models has generally proceeded along two separate lines of investigation; transport of bacteria as inert colloids in porous media, and the biodegradation of dissolved contaminants by a stationary phase of bacteria. Research over the last decade has indicated that these processes, contaminant biodegradation and bacterial transport, are closely linked. This linkage may occur when a change in metabolic activity alters the attachment/detachment rates of bacteria to surfaces, either promoting or retarding bacterial transport in a groundwater contaminant plume. Changes in metabolic activity, in turn, are controlled by the time of exposure of the microbes to electron acceptors/donor and other components affecting activity. Similarly, metabolic activity can affect the reversibility of attachment, depending on the residence time of active microbes. Thus, improvements in quantitative analysis of active subsurface biota necessitate direct linkages between substrate both a detailed understanding of the biologic processes and robust quantitative representations of these processes that can be tested experimentally. Int his paper we present an overview of current approaches used to represent physiochemical and biological processes in porous media, along with new conceptual approaches that link metabolic activity with partitioning of the microorganism between the aqueous and solid phases.