A fractured bedrock aquifer underlies the site.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
Major Contaminants and Maximum Concentrations:
- 1,1,1-Trichloroethane (50,000 µg/L)
No technologies selected.
- Bioremediation (In Situ)
- Reductive Dechlorination (In Situ Bioremediation)
Comments:
Plumes of chlorinated ethenes and ethanes were treated at four industrial sites in the northeastern United States. Anaerobic dechlorination was stimulated at each site by injecting lactate in one or both of the following two forms: (1) sodium lactate, or (2) glycerol polylactate polymer (slow-release formulation). The performance of the same carbon source was compared under four scenarios.
Of the four sites, only one (Site #3) was shown to have a contaminated fractured bedrock aquifer. A pilot application of glycerol polylactate polymer was injected into a single row of five bedrock wells at this site to stimulate anaerobic dechlorination of trichloroethane (TCA).
Not provided in information reviewed.
Over a 1.5-year period, the groundwater chemistry changed from anoxic to methanogenic, and dechlorination reduced TCA concentrations in groundwater by approximately 90 percent=. Full-scale treatment is currently in the design phase.
The two most critical factors for successful anaerobic dechlorination at the four industrial sites studied were (1) efficient, thorough lactate delivery, and (2) sustaining dissolved organic carbon (DOC) concentrations above 500 mgL for an extended period. The slow-release lactate formulations could not sustain sufficiently high DOC within the treatment zones. The readily bioavailable sodium lactate created high DOC concentrations but was metabolized rapidly, with an approximate 1-month half life. This short half life necessitated high-concentration applications to maintain the required DOC levels.
Reference:
Miller, Michael E. 2005. Biostimulation of anaerobic dechlorination: Strategy and results at four sites. The Eighth International In Situ and On-Site Bioremediation Symposium, Baltimore, Maryland. June 6-9.
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