Purpose:

Groundwater contamination by chlorinated solvents and perchlorate has become a major environmental issue for the Department of Defense (DoD). Numerous laboratory and field studies have shown that chlorinated solvents can be biodegraded by naturally occurring microorganisms under anaerobic conditions. The process can be enhanced by the addition of biodegradable organic substrates resulting in the production of less-chlorinated intermediate products. A limited number of studies have also shown that microorganisms from a variety of aquifers can anaerobically biodegrade perchlorate when supplied with appropriate organic substrates and related amendments. This project will investigate an innovative, low-cost approach for distributing and immobilizing a water miscible emulsion with a controlled droplet size as the biodegradable organic substrate in chlorinated solvent- and perchlorate-contaminated aquifers. The emulsion is prepared using food-grade edible oils and surfactants and then distributed throughout the treatment zone using conventional wells or temporary direct-push points. A portion of the oil becomes trapped within the soil pores leaving a residual oil phase to support long-term anaerobic biodegradation of the target contaminants.

Description:

A pilot-scale edible oil permeable reactive barrier will be installed at two different DoD locations to control the migration of a dissolved chlorinated solvent plume and a perchlorate plume respectively. As dissolved groundwater contaminants migrate through the barrier, the contaminants are removed or degraded, leaving uncontaminated water to emerge from the downstream side. The edible oil emulsion will be injected into a line of wells oriented perpendicular to groundwater flow. Biodegradation of contaminants entering the barrier will be enhanced by the slow dissolution of the trapped residual oil phase. The spatial distribution of the oil emulsion in each aquifer and the impact of emulsion injection on the aquifer permeability and groundwater flow paths will be monitored. The barrier performance will be tracked and field and laboratory data will be collected to evaluate the barrier's ability to stimulate biodegradation of the contaminants.

Benefits:

The design, permitting, and installation of an edible oil barrier are estimated to be lower in cost than competing technologies. Many pump-and-treat systems have been in operation for over 10 years with no end in sight for high operations and maintenance (O&M) costs. Iron barriers are believed to have lower O&M costs; however, initial construction costs vary from $30 to $500 per square foot with an average cost of $200. By contrast, design, permitting, and installation of an edible oil barrier are estimated to cost on the order of $15 to $25 per square foot. Implementation of the edible oil barrier technology has the potential to improve the effectiveness of aquifer remediation at many chlorinated solvent- and perchlorate-contaminated sites, while reducing costs. (Project Completed - 2006)

Contacts:

Technical Contact:
Dr. Robert Borden
Solutions Industrial & Environmental Services, Inc.
3722 Benson Drive
Raleigh, NC 27609
Telephone: (919) 873-1060
Fax: (919) 873-1074
E-mail: rborden@solutions-ies.com

DoD Liaison Officer:
Mr. Bryan Harre
Naval Facilities Engineering Service Center
1100 23rd Avenue
Port Hueneme, CA 93043
Telephone: (805) 982-1795
Fax: (805) 982-4304
E-mail: harrebl@nfesc.navy.mil