Modeling of Biological Processes in the Subsurface

Biofilm processes are potentially important for transformations of organic micropollutants in groundwater. The type of electron acceptor used by the microorganisms is an important environmental factor affecting biotransformation. A fundamental model of biofilm kinetics is shown to be capable of simulating microbially-mediated changes in a subsurface system of primary substrates and mixed electron acceptors. The model incorporates external mass transport effects, Monod kinetics with determination of limiting electron donor or acceptor, and competitive and sequential microbial reactions. The system to which the model is applied includes aerobic carbonaceous oxidation, nitrification, denitrification, sulfate respiration, and methanogenesis. The model establishes the dominant electron acceptor condition in a given region so that favorable environments for organic contaminant biotransformation can be determined. Model simulations could suggest useful strategies to achieve aquifer clean-up with biological processes.