INVESTIGATION OF BIOLOGICALLY ENHANCED DNAPL DISSOLUTION IN A BENCH-SCALE THREE-DIMENSIONAL FRACTURE NETWORK

Remediation of dense non-aqueous phase liquid (DNAPL) introduces unique challenges within fractured bedrock, especially in terms of microbe transport and activity during bioremediation. Little research exists that characterizes the fate of microbes within fractured settings, which makes implementing efficient bioremediation of DNAPL source zones in fractured media difficult. This research evaluates the dissolution behavior of tetrachloroethylene (PCE) DNAPL in a bench-scale three-dimensional (3-D) sandstone fracture network in the presence of microbial degradation activity, using Dehalococcoides sp. (DHC). Microbial kinetics, transport, and DNAPL dissolution will be considered as a function of (DHC) inoculation dosage. Reaction kinetics, as well as transport and delivery of microbes, are hypothesized to be affected by the complex flow patterns within a fracture network. Microbial reaction kinetics inferred from effluent breakthrough curves, when compared to those of static batch studies and discrete fracture experiments, provide a guide for understanding and improving field-scale bioremediation efforts. Results from discrete fracture experiments have shown up to a five-fold increase in DNAPL dissolution in the presence of microbial degradation.