Possible factors controlling the effectiveness of bioenhanced dissolution of non-aqueous phase tetrachloroethene

Tetrachloroethene (PCE) is a widespread subsurface contaminant. When PCE exists in the form of non-aqueous phase liquid (NAPL), it becomes a long term threat to groundwater quality. It has been recognized that treating the resulting plumes from PCE source zones alone is not effective because the long life of NAPL source zones may dictate the overall remediation time. Recent studies have shown the possibility of using microbial reductive dehalogenation to shorten the life of NAPL source zones by accelerating the dissolution process. To better understand the underlying mechanisms and the possible controlling factors of this technology, we used a novel two-dimensional numerical model to fully resolve the evolution of biomass profiles and the distributions of compounds within source zones. It was found that dehalogenation kinetics, electron donor (ED) levels, NAPL configurations, and ED competition among microorganisms all affect the extent of bio-enhanced dissolution. The simulation results point out the need to better characterize dehalogenation kinetics at high concentrations of PCE and its metabolic products.