Technology:
In Situ Bioremediation
- In situ bioremediation using the Enzyme-Catalyzed In Situ Dissolved Oxygen Treatment (DO-IT) process; patented process uses a combination of proprietary multi-enzyme complexes (proteins that are extracted from living TPH-degrading bacterial cultures), and a consortium of total petroleum hydrocarbon (TPH) degrading bacteria, with supplemental oxygen; generates a concentration of dissolved oxygen in water of approximately 40 mg/L
- Three horizontal injection wells, two vertical injection wells, and three extraction/recovery wells were installed within the plume
- Groundwater was extracted from down-gradient locations, amended by adding oxygenated water, nutrients, and the enzyme/bacterial consortium mixture, and then re-injected using the horizontal and vertical injection wells; layout provided for both treatment and hydraulic control
- Initial inoculation in January 1999 consisted of approximately 75 gallons of enzymes and 150 gallons of bacteria; each month, 5 gallons of enzymes and 10 gallons of bacteria have been added to the oxygenated water to maintain the microbial population
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Cleanup Authority:
Project Contact:
Mark B. Miller, P.G.
Remedial Solutions, Inc.
2733 Kanasita Drive, Suite A
Hixson, TN 37343
Telephone: (423) 870-8888
E-mail: remsol@cdc.net |
Contaminants:
MTBE, BTEX, TPH
- MTBE concentrations as high as 5,000 ug/L
- BTEX concentrations as high as 8,000 ug/L
- TPH concentrations as high as 300,000 ug/L
- Plume containing MTBE and benzene covers approximately 16,000 square feet; TPH plume covers approximately 66,000 square feet (1.5 acres) |
Waste Source:
Leaks from an underground gasoline storage tank |
Type/Quantity of Media Treated:
Groundwater
- On-site groundwater is located within a tight clay soil horizon at 5-7 feet below ground surface (bgs)
- Off-site groundwater is located in bedrock consisting of limestone and shale beds at depths of greater than 10 feet bgs |
Purpose/Significance of Application:
Use of in situ bioremediation to treat MTBE in groundwater |
Regulatory Requirements/Cleanup Goals:
The cleanup criteria specified for this site were benzene - 100 mg/kg in soil and 70 ug/L in groundwater, and TPH - 1,000 mg/kg in soil and 1,000 ug/L in groundwater
- No cleanup levels were specified for MTBE, however MTBE was identified as a contaminant of concern for the site |
Results:
Results were available for the first 360 days of operation (January to December 1999) from well MW-2 (the well with the highest concentrations of contaminants)
- MTBE concentrations were reduced from approximately 5,000 ug/L to approximately 200 ug/L
- Benzene concentrations were reduced from as high as 8,000 ug/L to less than approximately 1,000 ug/L
- TPH concentrations were reduced from as high as 300,000 ug/L to less than approximately 50,000 ug/L
- Benzene and TPH concentrations remain above cleanup goals; treatment system operation is ongoing |
Cost Factors:
Start-up costs for this site, including the initial inoculation, were approximately $30,000
- Monthly maintenance costs have been approximately $4,000, through December 1999 |
Description:
As a result of leaking underground storage tanks (USTs), gasoline, diesel fuel, and waste oil releases occurred at an abandoned gasoline service station located in a mixed-use area in Chattanooga Tennessee. The service station has no remaining on-site structures or facilities. The releases resulted in contamination of soil and groundwater at the site with MTBE, BTEX, and petroleum constituents. Concentrations of contaminants measured in groundwater at the site were as high as MTBE at 5,000 ug/L, benzene at 8,000 ug/L, and total petroleum hydrocarbons at 300,000 ug/L. The vendor estimated that 1,500 cubic yards of soil at the site were impacted by the contamination. In the mid-1990s, the USTs were removed and decommissioned.
Beginning in January 1999, in situ bioremediation using the Enzyme-Catalyzed In Situ Dissolved Oxygen Treatment (DO-IT) process was used to treat groundwater at the site. This process uses a combination of proprietary multi-enzyme complexes and a consortium of total petroleum hydrocarbon (TPH) degrading bacteria, with supplemental oxygen, to biodegrade MTBE, BTEX, and TPH contaminants. At this site, three horizontal injection wells, two vertical injection wells, and three extraction/recovery wells were installed within the plume. In January 1999, the initial inoculation of approximately 75 gallons of enzymes and 150 gallons of bacteria was performed. Subsequently, 5 gallons of enzymes and 10 gallons of bacteria have been added to the oxygenated water each month to maintain the microbial population. As of December 1999, after 360 days of operation, the concentrations of MTBE, BTEX, and TPH have been reduced by more than 70%. However, cleanup goals were not reached for benzene or TPH in the groundwater during this time, and treatment is ongoing. The technology vendor reported that this application was aided by the design of injection galleries that were specific to the low permeability of the soil formation and the intended injection approach. |
