TCE Ground-Water Plume Remediation: Fletcher, North Carolina
In January 2006, Leggette, Brashears & Graham, Inc. (LBG), submitted an injection well permit application to the North Carolina Department of Environment and Natural Resources (approved March 2006) for the injection of emulsified vegetable oil into a chlorinated solvent plume at an industrial facility. Data previously collected from the facility had indicated that there was virtually no naturally occurring breakdown of the TCE.
Because the responsible party did not own the facility property, they wanted to avoid the continuing cost, operation and maintenance of a more traditional remediation system (i.e. pump and treat). A pilot test subsequently demonstrated the viability of injecting an electron donor, the emulsified vegetable oil, to create reducing conditions and stimulate the growth of indigenous, dehalogenating microbes.
The emulsified oil was injected into the two shallow groundwater plumes (Areas 1 and 2) through 77 temporary, 1-inch PVC injection points. A total of 115,000 gallons of diluted emulsified oil was injected over a 12-day period, to promote the reductive dechlorination of the TCE. Conversely, ethene concentrations have increased from 2.1 ug/L to 110 ug/L, thus demonstrating the complete dehalogenation cycle from TCE to ethene.
The addition of emulsified vegetable oil, which increases the magnitude of attenuation by natural processes, is a specific type of active treatment strategy based significantly on the idea of sustainability. For a typical site, the remedial plan is to start with source treatment and active plume treatment to rapidly remove significant contaminant mass. These methods become less efficient over time, eventually using relatively large amounts of energy/power to remove small amounts of the contaminant.
The injection of the emulsified vegetable oil, which works to stimulate the activity of natural microorganisms and has longer term “staying power”, will result in a naturally sustainable treatment that consumes minimal power while meeting environmental cleanup goals. This naturally sustainable treatment can be deployed to treat source areas as well as contaminants in the resulting subsurface plumes.