Modeling the elongation of commingled BTEX and chlorinated ethene plumes undergoing biodegradation with a multi-level substrate interaction module.

Multi-solvent co-contamination is a common phenomenon found in organically contaminated groundwater. A mathematical approach based on multi-level substrate interactions was developed to describe the microbial growth and the corresponding biodegradation of highly chlorinated ethenes (CEs) in the presence of the co-contaminant BTEX. The Reactive Transport in 3 Dimensions (RT3D) model was applied to integrate proposed mathematical model into reactive transport framework. With benzene and PCE as target contaminants, the most influential interaction mechanisms on microbial growth, the corresponding substrate depletion, and the contaminant plume elongation were evaluated. The results revealed that the calculations based on the parameter values identified by the Markov chain Monte Carlo (MCMC) procedure exhibited strong agreement with the microcosm observations (R > 85 %). The simulations accurately reproduced the trends observed in the microcosm studies of the accelerated PCE consumption with low concentrations of benzene and the inhibited PCE utilization with high concentrations of benzene. Fortuitous catalytic degradation based on enzymatic reactions was derived to be the main mechanism affecting the extension of the PCE plume. The proposed approach offers valuable insights into microbial population dynamics and associated substrate depletion in commingled plumes and is expected to serve as a useful tool for studying the bioremediation of commonly occurring co-contaminated groundwater.