The geology of the site is approximately 10 ft of glacial till over granite. The bedrock is competent at ~40 ft. The ground-water elevation is 8 to 10 ft below ground surface. The aerial extent of the site is approximately 1 acre.
Targeted Environmental Media:
 Fractured Bedrock - Light Non-aqueous Phase Liquids (LNAPLs)
Numerous releases occured from leaking underground piping, tank overfills and leaking drums.
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (68,000 µg/L)
- Tetrachloroethene (68,000 µg/L)
- Toluene (1,400 µg/L)
- Hexane (LNAPL)
No technologies selected.
- Bioremediation (In Situ)
Comments:
In June 2001, a pump and treat bioreactor system was installed. The system consists of pumping from two perimeter down gradient recovery wells into a 500 gallon plastic tank aerated by a small compressor followed by another 500 gallon plastic settling tank, two parallel bag filters and a 1,000 lb. carbon canister. The effluent flows by gravity into an upgradient leaching field.
The average dailyflow rate treated is 5,700 gallons. Since startup, 4.85 millon gallons of ground water have been treated. The capacity of the leaching field limits the system's flow rate. In the summer, with the water temperatures approaching 68 degrees, the bioreactor system removed more than 95% of the contaminants. In the winter, with water temperature at 43 degrees the system efficiency declined to ~50%. The average daily influent of contaminants is 559 mg and effluent is 118 mg.
The system did not work until microbes and nutrients were added to the first bioreactor. The microbes added to the first bioreactor are a consortium of aerobic hydrocarbon degraders and aerobic chlorinated compound degraders.
None provided
The capitol cost of the system is less than $5,000. Utility costs are approximately 160 kwmonth. The monthly cost of microbes is $1,300.
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