This remedial technology, developed by the University of Waterloo and EnviroMetal Technologies Inc., degrades dissolved halogenated organic compounds in groundwater with an in situ permeable wall containing reactive metal (usually iron) (see photograph below). The technology may also be used in an aboveground reactor for ex situ treatment.
Installation of Pilot-Scale In Situ Treatment System at an Industrial Facility in Northeast United States
The technology employs an electrochemical process. Contaminated groundwater passes through the specially prepared granular reactive iron, which oxidizes, inducing reductive dehalogenation of contaminants. Halogenated organics are degraded to nonhazardous substances, preventing contaminants from migrating further downstream. Observed degradation rates are several times higher than those reported for natural abiotic degradation processes.
In most in situ applications of this technology, groundwater moves naturally through the permeable subsurface wall or is directed by flanking impermeable sections such as sheet piles or slurry walls. This passive remediation method is a cost-effective alternative to conventional pump-and-treat methods. Aboveground reactor vessels employing this technology may replace or add to treatment units in conventional pump-and-treat systems.
Process residuals may include dissolved ethane, ethene, methane, hydrogen gas, chloride, and ferrous iron. Because contaminants are degraded to nonhazardous substances and not transferred to another medium, this process eliminates the need for waste treatment or disposal.
The process was developed to treat dissolved halogenated organic compounds in groundwater. The technology has degraded a wide variety of chlorinated alkanes and alkenes, including trichloroethene (TCE), tetrachloroethene (PCE), vinyl chloride, 1,1,1-trichloroethane, and 1,2-dichloroethene (DCE). The technology also degrades other organic contaminants, including Freon-113, ethylene dibromide, certain nitroaromatics, and N-nitrosodimethylamine.
This technology was accepted into the SITE Demonstration Program in spring 1993. A pilot-scale demonstration of the aboveground reactor (ex situ) technology took place from November 1994 to February 1995 at an industrial facility in New Jersey. Groundwater at the facility contained dissolved TCE and PCE.
A second SITE demonstration was performed in New York from May through December 1995. A pilot-scale in situ permeable wall was installed in a shallow sand and gravel aquifer containing TCE, DCE, vinyl chloride, and 1,1,1-trichloroethane. This project may eventually be expanded to full-scale.
A successful permeable in situ wall was installed at the Canadian Forces Base Borden test site in June 1991. The technology removed about 90 percent of the TCE and PCE from groundwater passing through the reactive iron wall. The wall has performed consistently for 5 years. More than 250 sites have been identified where the technology could be applied. Over 50 successful bench-scale feasibility tests have been completed using groundwater from industrial and government facilities in the United States and Canada.
The first full-scale, in situ installation of this technology was completed at an industrial facility in California in December 1994. Since that time, five additional full-scale in situ systems and three pilot-scale systems have been installed in locations including Colorado, Kansas, North Carolina and Belfast, Northern Ireland. Several more are planned for 1997. Aboveground treatment systems have been proposed at sites in Maryland and Germany.
During the New Jersey (ex situ) demonstration, about 60,833 gallons of groundwater was treated during 13 weeks of sampling. Conversion efficiency of PCE during the demonstration period exceeded 99.9 percent. Vinyl chloride and cis-1,2-dichloroethene occasionally exceeded the New Jersey Department of Environmental Protection limits. This exceedance may have been caused by a reduction in the iron's reactive capacity due to precipitate formation. Complete demonstration results will be published in the Technology Capsule and Innovative Technology Evaluation Report (ITER), which will be available in 1997.
For the New York (in situ) demonstration, preliminary data indicate a significant reduction in all critical contaminants present, and no apparent decrease in removal efficiency over the seven month demonstration period. Results of the in situ demonstration of the process will be published in an ITER that will be available in 1997.
EPA PROJECT MANAGER:
Chien Chen
U.S. EPA
National Risk Management Research Laboratory
2890 Woodbridge Avenue, MS-104
Edison, NJ 08837-3679
908-906-6985
Fax: 908-321-6640
TECHNOLOGY DEVELOPER CONTACT:
Larry Kwicinski
EnviroMetal Technologies Inc.
42 Arrow Road
Guelph, Ontario, Canada N1K 1S6
519-824-0432
Fax: 519-763-2378