ORIN successfully implemented a pilot study utilizing in-situ anaerobic bioremediation to treat contaminated groundwater at a National Priorities List Superfund Site. Chlorinated hydrocarbons were the remedial drivers. Due to the low cost of EOS®, ORIN saved the client over $25,000 during the pilot test when compared to similar products.

Site Characteristics

  • Site: Residential plume in Long Prairie, MN.
  • Geology: Silty sand to course sand.
  • Groundwater velocity: average 2×10-3 cm/sec
  • Contaminants: Tetrachloroethene – 90 micrograms per liter
  • (ug/L)

Remediation Approach

  • Treatment chemistry: EOS®
  • Treatment application: Chemical injections utilizing direct push
  • technology (DPT).

Chemistry Used During Injection

The EOS® process provides an innovative, low-cost approach for distributing and immobilizing biodegradable organic substrates in contaminated aquifers to promote in-situ anaerobic biodegradation of chlorinated solvents. EOS® consists of food grade soybean oil, surfactants, macro and micronutrients, and vitamins blended to form a stable micro-emulsion with small, uniformly sized droplets. Once injected, the oil droplets stick to the sediment surfaces providing a residual oil phase. The EOS® then serves as a carbon source for cell growth and an electron donor for energy generation, supporting long-term anaerobic biodegradation of the target contaminants.

This approach provides good contact between the slowly biodegradable organic substrate (oil) and the contaminants and substantially reduces initial capital and long-term operation and maintenance costs. For example, common organic solvents utilizing EOS® is completely reduced to ethene according to the following equations:

  • PCE: C2Cl4 + 4H2 → C2H4 + 4H+ + 4Cl-
  • TCE: C2HCl3 + 3H2 → C2H4 + 3H+ + 3Cl-
  • DCE: C2H2Cl2 + 2H2 → C2H4 + 2H+ + 2Cl-
  • VC: C2H3Cl + H2 → C2H4 + H+ + Cl-

Summary of Implementation

The purpose of the pilot study was to provide information on the feasibility and logistics of full-scale treatment. Six injection points (IP-1 through IP-6) were advanced using DPT throughout the treatment area. Each point was located approximately 16.5 feet apart to ensure complete coverage of the targeted treatment area. The vertical treatment zone extended from 50 feet below ground surface (ft. bgs) to 25 ft. bgs. ORIN injected a 5% concentration of EOS treatment chemistry into the injection points to enhance the naturally occurring reductive dechlorination of chlorinated solvents. Each injection point received approximately 1,325 gallons of treatment chemistry. A total of 7,950 gallons of 5% EOS treatment chemistry was injected into the six injection locations over an eleven-hour day.

Effectiveness

Four months following the pilot test, PCE concentrations in the source area decreased from 90 ug/L to less than 5 ug/L. The client and state regulators are planning to implement ORIN’s full-scale design in fall of 2007.

The Bottom Line

The pilot study demonstrated the effectiveness and feasibility for utilizing EOS® to treat a National Priorities List Superfund Site, saving the client $1,000,000 in full-scale costs.