A Numerical Model (SEAM3D) to Assess the Biotransformation of Chlorinated Ethenes at a TCE/BTEX Contaminated Site

Abstract

Numerical models (GMS MODFLOW, SEAM3D, and SEAM3D Interface) were applied to simulate groundwater flow, petroleum hydrocarbon compound (PHC) transport and biodegradation, and the transport and biotransformation of chlorinated ethenes at Site FT-002 Plattsburgh Air Force Base (PAFB), NY. Site FT-002 was contaminated with waste jet fuel and chlorinated ethenes used as a fire source during fire fighting training. The results of groundwater analysis indicated that the aquifer exhibited aerobic, nitrate reducing, ferrogenic, sulfate reducing and methanogenic conditions due to the biodegradation of the PHCs. Additional groundwater analysis showed the biotransformation of TCE to DCE, VC, and ethene. A numerical model was developed to simulate and assess the extent to which reductive dechlorination and direct anaerobic oxidation were responsible for the biotransformation of the chlorinated ethenes. Reductive dechlorination accounted for the 100%, 98.3%, and 97.5% of the biotransformation of TCE, DCE, and VC respectively. Direct anaerobic oxidation accounted for 1.7% and 2.5% of the biotransformation of DCE and VC respectively. Though direct anaerobic oxidation only accounted for a small percentage of total biotransformation it was necessary to fully develop the biotransformation of the DCE and VC in the ferrogenic zone. This study focused on the mechanisms responsible for the biotransformation of chlorinated ethenes, specifically reductive dechlorination and direct anaerobic oxidation. By further defining the NAPL source and initial conditions it could be used as a tool to accurately predict the monitored natural attenuation (MNA) of the FT-002 contaminant plume.