Enhanced In-Situ Anaerobic Bioremediation using Vegetable Oil Substrate
-- A vegetable oil, lecithin, and native groundwater emulsion was injected into three shallow and three deep injection wells (230 gallons per shallow well and 600 gallons per deep well). Following the emulsion, a water push of additional groundwater was pumped through the injection wells (50 gallons per shallow well and 150 gallons per deep well).
-- Approximately 25 percent of the emulsion was composed of vegetable oil and lecithin. The remaining 75 percent consisted of native groundwater.
-- Emulsification of the vegetable oil, lecithin, and water took place using ½ inch diameter Koflow™ static in-line mixers.
-- The emulsion was injected using Ingersol-Rand ARO air-operated diaphragm pumps. The flow rates, volume, and pressure were controlled using flow meters, pressure gauges, and valves allowing multiple injection points with different volumes and pressures.
-- The maximum injection rate into the shallow wells was 10 gallons per minute at a maximum injection pressure of 10 pounds per inch. The maximum injection rate in the deep wells was 6.4 gallons per minute at a maximum injection pressure of 18 pounds per inch.
-- Over 600 gallons of the emulsion was injected into four additional wells in order to treat an area that did not achieve cleanup goals after Phase I injection. An additional 100 gallons of groundwater was injected following the injection of emulsion in order to improve emulsion distribution.
AFCEE Project Manager:
Erica S.K. Becvar, M.S.
3300 Sidney Brooks
Brooks City-Base, TX 78235
Bruce M. Henry, P.G.
1700 Broadway, Suite 900
Denver, CO 80290
Tetrachloroethene (PCE); trichloroethene (TCE); cis-1,2-dichloroethene (cis-1,2-DCE); 1,1,1-trichloroethane (1,1,1-TCA); 1,1-dichloroethane (1,1-DCA).
Spills from 55-gallon drums containing spent chlorinated solvents.
Type/Quantity of Media Treated:
Groundwater (quantity not documented)
Purpose/Significance of Application:
Remediation of chlorinated ethenes and ethanes in soil and groundwater.
Regulatory Requirements/Cleanup Goals:
Ground Water Protection Standards established by the Ohio Environmental Protection Agency: PCE = 5.0 microgram per liter (ug/L); TCE = 5.0 ug/L; cis-1,2-DCE = 20.0 ug/L; 1,1,1-TCA = 68.0 ug/L; 1,1-DCA = 43.0 ug/L.
Enhanced in situ anaerobic bioremediation using vegetable oil substrate provided an environment required for the dechlorination of ethenes. After injection of the substrate during Phase I, all monitoring locations except one had achieved the cleanup goals. A Phase II injection was performed in the area where the cleanup goals were not achieved. Data obtained after the Phase II injection indicated that the anaerobic conditions were achieved at all locations. Concentrations of PCE and TCE decreased significantly while dechlorination products increased initially and then decreased subsequently.
Capital cost for both phases of the in-situ anaerobic bioremediation totaled $131,900 with Phase I accounting for 60 percent of the costs. The higher costs of Phase I were largely associated with the installation of nine monitoring and six injection wells, while Phase II installation costs accounted for four direct injection locations. Operating costs totaled $228,000 which accounted for eleven sampling events over 49 months.
FF-87 is located on the Former Newark Air Force Base in Ohio. The Former Newark Air Force Base is currently being leased to Boeing Aircraft Corporation who uses the location to produce and calibrate instruments. Surrounding the base are areas used for industry, farming, and housing. FF-87 consisted of a semi-enclosed structure that housed 55-gallon drums filled with solvents and spent Freon 113. The chemicals were believed to have entered the subsurface through spills that migrated beneath the asphalt flooring. Contaminants at the site included tetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (cis-1,2-DCE), 1,1,1-thichloroethane (1,1,1-TCA), and 1,1-dichloroethane (1,1-DCA). The largest concentration of contaminant was 1,300 micrograms per liter (ug/L) of PCE; other contaminants had a concentration of 150 ug/L or less.
Enhanced in situ anaerobic bioremediation using vegetable oil substrate was selected to remediate the site. The vegetable oil emulsion provided an anaerobic environment in which the chlorinated ethenes could be chemically reduced. The initial application of the substrate resulted in the achievement of contaminant concentrations below the Ground Water Protection Standards established by the Ohio Environmental Protection Agency for all monitoring locations except one. The second application of the substrate was targeted for the area surrounding one monitoring location and showed a substantial decrease in the parent compound followed by a peak and then a decrease of the dechlorination compounds.