Objective:

Previous studies have demonstrated that naturally-occurring bacteria can be added to aquifers to promote anaerobic biodegradation of chlorinated solvents to environmentally-acceptable end products such as ethene and chloride. To date, the impacts of permanganate and reduced manganese-oxides on the activity of these dehalorespiring microorganisms have not been assessed. This project will demonstrate the application of a sequential treatment approach for sites with chlorinated solvent dense non-aqueous phase liquids (DNAPL) that uses in-situ chemical oxidation with permanganate coupled with enhanced bioremediation. Coupling these technologies provides a cost-effective remedial approach that can 1) substantially increase the dissolution rate of DNAPL and accelerate DNAPL removal and/or 2) contain plume migration by rapidly degrading the high concentrations of dissolved phase contaminants that emanate from the DNAPL source.

Technology Description:

The initial phase of this project will include a treatability assessment using uncontaminated soil spiked with perchloroethylene (PCE) DNAPL. The laboratory study will evaluate the impacts of chemical oxidation on the inorganic geochemistry and microbiology of the aquifer materials and the need for aquifer pre-conditioning prior to bioremediation, determine whether dechlorination of PCE to ethene may be accomplished through either biostimulation of the surviving indigenous microorganisms or bioaugmentation with a dehalorespiring bacteria consortium, and identify optimal conditions (electron donor and concentration) for biostimulation and/or bioaugmentation using an accepted dehalorespiring microbial culture. In the second phase, a Department of Defense (DoD) site will be selected for a field demonstration. Site-specific data will be used to design a closed-loop groundwater recirculation system in a DNAPL source area. Groundwater will be circulated through the treatment zone under a variety of test conditions including 1) baseline (non-biologically enhanced using unamended groundwater), 2) oxidant addition using concentrated permanganate solution, 3) electron donor addition (biostimulation), and 4) electron donor addition plus bioaugmentation of dehalorespiring microorganisms.

Expected Benefits:

This technology demonstration will result in the development of an innovative in-situ remediation approach that will allow cost-effective and expedited cleanup of DNAPL source sites at DoD and related facilities. As a stand-alone technology, chemical oxidation provides significantly enhanced dissolution and destruction of the target contaminants within a relatively short period; however, the rate of mass removal by this technology diminishes over time. At many sites, the most appropriate use of this technology may be rapid removal of accessible target DNAPL mass within the source area followed by the implementation of a less active in-situ remediation approach (enhanced bioremediation) to contain migration of the remaining dissolved phase contaminants. (Anticipated Project Completion - 2007)

Principal Investigator:

Dr. David Major
GeoSyntec Consultants
130 Research Lane, Suite 2
Guelph, Ontario N1G 5B2
Telephone: (519) 822-2230
Fax: (519) 822-3151
E-mail: dmajor@geosyntec.com

DoD Liaison:

Dr. Jeffrey Davis
U.S. Army Corps of Engineers

Engineer Research and Development Center
3909 Halls Ferry Road
Vicksburg, MS 39180
Telephone: (601) 634-4846
Fax: (601) 634-4844
E-mail: jeffrey.l.davis@erdc.usace.army.mil