Purpose:

The Department of Defense (DoD) has used chlorinated aliphatic hydrocarbons (CAH) since the late 1940's, and accidental spills, improper storage, and historical disposal practices have resulted in widespread occurrence of CAHs in the environment. Co-disposal of CAHs with petroleum products was a common practice at many fire-training areas, chemical disposal pits, and unsecured landfills throughout the DoD. It has been estimated that there are as many as 1,000 sites containing free-phase light non-aqueous phase liquid (LNAPL), and a strong potential exists that a significant number of these sites contain co-solvated mixtures of hydrocarbons and CAHs. These mixtures are often LNAPLs that tend to smear in the capillary fringe as the water table fluctuates.

The DoD has been developing innovative remediation technologies to treat CAHs in groundwater. Enhanced anaerobic dechlorination (EAD) through the delivery of electron donor compounds is one of the more promising technologies that have been demonstrated successfully at numerous DoD sites. Anaerobic bioventing is an innovative approach for treating CAHs in the vadose zone where injected anaerobic gas containing hydrogen serves as the electron donor, and it has been demonstrated on a pilot scale. The purpose of this project is to demonstrate the effectiveness of a combination of these two approaches to remove CAHs from the capillary fringe at co-solvated sites.

Description:

The technology being demonstrated is an innovative application of EAD that combines two mature technologies, air sparging and bioventing, to address chlorinated solvent contamination smeared in the capillary fringe. The technology establishes anaerobic conditions and stimulates the reductive pathway by sparging anaerobic gas containing hydrogen just below the water table. Some of the hydrogen dissolves into the groundwater to support biodegradation and the sparging action carries contaminant and residual hydrogen to the soils above the water table to stimulate biodegradation similar to anaerobic bioventing.

Benefits:

The primary benefit of in-situ bioremediation is the destruction of contaminants without the need to bring them above ground. This eliminates mass transfer constraints as well as the need for above ground treatment and monitoring and results in significant cost savings over current extract-and-treat technologies. A successful demonstration of enhanced dechlorination in the capillary fringe will result in a technology that can be applied alone or in conjunction with other remedial technologies to reduce cleanup times.

Contacts:

Technical Contact:
Dr. Bruce Alleman
Battelle Memorial Institute
Columbus, OH 43201-2693
Telephone: (614) 424-5715
Fax: (614) 424-3667
E-mail: allemanb@battelle.org

DoD Liaison Officer:
Dr. Jon Ginn
OO-ALC/EMR
Hill AFB, UT 84056-5137
Telephone: (801) 775-6894
Fax: (801) 777-4306
E-mail: jon.ginn@hill.af.mil