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 design a bioremediation system for treating carbon tetrachloride (CT) in groundwater at the U.S. Department of Energy's Hanford site.  This case study was an Accelerated In Situ Bioremediation Design, in which the bioremediation team determined the approach and design of a pilot-scale bioremediation system.  Battelle provides accelerated in situ bioremediation designs and other bioremediation services to clients around the country.

The U.S. Department of Energy's Hanford Site, located in southeastern Washington State, was the site for a technology demonstration to remediate CT in groundwater.  An estimated 20,000 to 70,000 kg of carbon tetrachloride is present in a 10-km² plume at the site.  The highest groundwater concentra-tion of CT is approximately 7 mg/L.  Nitrate is a co-contaminant throughout most of the plume.  The aquifer is a heterogeneous mixture of sand, gravel, and silt with layered variations in permeability created by calcium carbonate cementation and differences in silt content.  The field demonstration site is in a portion of the plume that contains approximately 2 mg/L CT and 250 mg/L nitrate.  Contaminant concentrations are relatively constant over a large area of the plume surrounding the test site.  The unsaturated zone over the test site is 75-m thick and is uncontaminated.

Design, operate, and evaluate a field application of accelerated in situ bioremediation for CT and nitrate destruction.  Data collected during the field test must demonstrate that contaminants were destroyed to nonhazardous end products and must provide the required information to accurately scale the process to treat a several hundred acre region near the original source of the contamination.

Accelerated in situ bioremediation of CT was successfully implemented with simultaneous denitrification.  Highlights of the test included:

• Dechlorination byproducts were controlled (avoiding production of chloroform).
• Measured CT destruction rates in the field were comparable to those based on laboratory data.
• Biofouling in injection and extraction wells was avoided even though an estimated 20 kg (dry weight) of bacteria was grown in the subsurface.

 

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