The Effect of Oxygen Transport on Biotransformation of Trichloroethylene in the Subsurface

Trichloroethylene (TCE) is one of the most-frequently-detected chemicals in the contaminated groundwater. In the subsurface, TCE can be biodegraded by indigenous microorganisms through coexisting aerobic and anaerobic bioprocesses, which are determined mostly by oxygen, energy sources, and electron acceptors. The bio-processes generate different benign or toxic byproducts. We investigate oxygen transport, induced by the density-driven gas flow and groundwater flow, and the effect of oxygen presence on the fate of TCE and its associated byproducts via the variation of aerobic and anaerobic bioprocesses in the unsaturated and saturated zones. In this study, the types and rates of the bioprocesses depend only on the oxygen-concentration level. Fully coupled nonlinear multiphase flow and multi-species transport equations are formulated and solved using the Galerkin finite element technique. Both sequential dehalogenation and aerobic cometabolic biodegradation of the contaminants are considered. The aerobic bioreaction under oxic conditions had significant impacts on the fate of TCE's byproducts in the subsurface.