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FIELD SCALE EVALUATION OF TREATMENT OF TCE IN A BIOWALL AT THE OU-1 SITE
Citation:
WILSON, J. T., X. LU, AND H. SHEN. FIELD SCALE EVALUATION OF TREATMENT OF TCE IN A BIOWALL AT THE OU-1 SITE. Presented at The Enhanced In Situ Bioremediation Workshop, San Antonio, TX, April 24 - 25, 2007.
Impact/Purpose:
To inform the public.
Description:
A passive reactive barrier (Biowall) was installed at the OU-1 site at Altus Air Force Base, Oklahoma to treat TCE contamination in ground water from a landfill. Depth to ground water varies from 1.8 to 2.4 meters below land surface. To intercept and treat the plume of contaminated ground water, a trench 140 meters long, 7.6 meters deep, and 0.46 meters wide was filled with a mixture of shredded tree mulch, composted cotton gin trash, and sand. The Biowall was installed in June 2002. When monitored in 2005, it was still consistently reducing the concentrations of TCE in ground water leaving the Biowall by 90% or more. Presumably, the extent of treatment of TCE by the plant mulch in the Biowall will be a function of the residence time of contaminated ground water in the Biowall. To determine the rate of treatment, it is necessary to know the residence time water in the Biowall. In 2005 a bromide tracer test was conducted to determine the seepage velocity of ground water and the residence time of ground water in the Biowall. The concentrations of TCE and bromide were monitored in the wells in Biowall and down gradient of the Biowall. The average seepage velocity of ground water was 0.07 meters per day. Based on the seepage velocity, the geometry of the Biowall, and the measured porosity of the sediment in the aquifer and the matrix of the biowall, the residence time of ground water in the Biowall would be 10 days. If all the TCE removal occurred in the Biowall, this corresponds to a pseudo-first order rate constant of 0.2 per day.