The RT3D software, one of the computer codes used in the Battelle Chlorinated Solvent Design Service, was used in the case study described here to evaluate bioremediation options for a contaminated plume located at the U.S. Department of Energy's Idaho National Engineering and Environmental Laboratory (INEEL).  This case study was a Remediation Alternatives Evaluation, in which the bioremediation team determined if natural attenuation, accelerated in situ bioremediation, or a combination of the two is needed to remediate the contamination in the plume.  Battelle provides remediation alternatives evaluations and other bioremediation services to clients around the country.

The Snake River Plain Aquifer at INEEL in Idaho Falls, Idaho is contaminated by an almost 2-mile long trichloroethene (TCE) plume resulting from historical deep injection of liquid waste.  Based on groundwater concentrations, free phase TCE is suspected to still exist near the injection well.  The water table is located approximately 200 to 300 ft below ground surface.  Contamination extends to a depth of up to 100 feet below the water table.  The aquifer is comprised of a complex layering of fractured basalt flows intercalated with sedimentary interbeds.  Regional-scale modeling of the plume indicates that remediation of the contamination within the 1.0-mg/L contour will be sufficient to ensure contamination does not migrate to downstream receptors.

Use the RT3D computer code to evaluate the technical feasibility and clean-up time for remediating the contamination within the 1.0-mg/L contour.  Four remedial options were evaluated:

• Groundwater extraction and aboveground treatment (air stripping and granular activated carbon adsorption)
• Natural attenuation of the plume
• Accelerated aerobic in situ bioremediation ^[1] of the high concentration region around the deep injection well, combined with natural attenuation of dispersed plume.
• Accelerated anaerobic in situ bioremediation ^[2] of the high concentration region around the deep injection well, combined with Natural Attenuation of dispersed plume.

Reactive-flow-and-transport analysis streamlined the technology selection process by quickly revealing the most reasonable technologies.  The table below summarizes the results of the technology screening.  Based on these results, a pilot-scale test of accelerated anaerobic in situ bioremediation coupled to natural attenuation is now being implemented.

 

For more information, contact:
Michael Truex Program Manager Field Hydrology and Chemistry Group	Battelle 902 Battelle Blvd., K6-96 Richland, WA 99352 USA	509-376-5461 509-372-1704 FAX mj.truex@pnl.gov