EVALUATION OF BIOREMEDIATION SUITABILITY AT A TCE-CONTAMINATED SITE BASED ON MODELING OF LARGE-SCALE COLUMN TRACER AND MICROCOSM EXPERIMENTS

Enhanced biodegradation using carbon donor and microbial amendment addition is being considered as a possible remediation technique for trichloroethylene (TCE) contaminated groundwater in Sunset, Utah, west of the source area on Hill Air Force Base. As a precursor to any in situ remediation attempts, several laboratory treatability experiments are being conducted at both a microcosm scale and at a larger flow-through column scale. Nine large-scale (6-ft (183-cm) long, 6-in (15-cm) diameter) columns were built using site soil and groundwater. Bromide tracer tests were conducted to determine the hydraulic conditions within the columns. Microcosms were used to study the effectiveness of various carbon donors and microbial populations in stimulating TCE dechlorination under simulated site aquifer conditions. Using the data obtained from several selected treatments of these microcosm experiments, first-order degradation rates were estimated. Finally, predictive models were created, and used to show potential degradation scenarios in the columns and in the field for the selected treatments. Of the various carbon donors used in the microcosm experiments, an emulsified oil showed the most promise for enhancing TCE degradation, and was selected for this predictive modeling. Treatments selected for modeling indicated that carbon addition alone is insufficient for stimulating dechlorination of TCE, and that microbial amendments will be necessary.