Model simulations for in situ aerobic cometabolism of trichloroethylene

BACKGROUND: While overall removal of trichloroethylene (TCE) can be estimated from in situ pilot studies of aerobic cometabolism, no quantitative information on the relative importance of the biodegradation and sorption processes is currently available. This paper presents a quantitative method to evaluate the dynamics and the individual removal efficiencies of cometabolic biodegradation and sorption processes using model simulations for in situ aerobic cometabolism. RESULTS: The first-order rate constant of TCE cometabolism by aerobic toluene-utilizing bacteria was around 0.2 to 0.3 L mg^-1 day^-1. The TCE partition coefficient of sorption was determined at 16.4 L kg^-1. The sorption process diminished as the sorption capacity of the aquifer solids became saturated. The sustainable TCE removal efficiency due to cometabolic biodegradation for the in situ pilot was determined at 25.8%, 51.8%, and 75.2% for residence times of 0.14 day, 0.57 day, and 1.16 day, respectively, after establishing an indigenous toluene-degrading consortium. CONCLUSION: The agreement between model simulations and pilot results demonstrates the validity of a model that incorporates fundamental microbial and transport processes of advection, dispersion, and sorption onto the aquifer solids. The mathematical model aids the understanding of both the dynamics and the individual removal efficiencies of sorption and biodegradation processes of in situ bioremediation.