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EFFECT OF ETHANOL ON NATURAL ATTENUATION OF BENZENE AT UST SITES
Citation:
ADAIR, C. J., J. T. WILSON, D. MACKAY, AND M. EINARSON. EFFECT OF ETHANOL ON NATURAL ATTENUATION OF BENZENE AT UST SITES. Presented at First National Tanks Conference , Memphis, TN, March 20 - 22, 2006.
Impact/Purpose:
To inform the public.
Description:
The use of ethanol as a fuel oxygenate has caused concern regarding the risk it poses as a groundwater contaminant. The natural bioattenuation of automobile fuels, including benzene, may be inhibited by the presence of ethanol as a result of a spill. Ethanol, in the presence of other fuel components, would be expected to influence the subsurface microbial community by consuming electron acceptors and slowing or stopping BTEX biodegradation. The presence of ethanol may also reduce the number of microorganisms available to biodegrade the fuel components. Field and laboratory experiments were conducted to evaluate the effect of ethanol on the natural attenuation of benzene in ground water. A full-scale field study was conducted at a site on Vandenberg AFB in California where groundwater was impacted by a spill of motor gasoline. The University of California at Davis supplemented two flow paths in the aquifer with benzene and benzene plus ethanol. The progression of each plume was recorded. Laboratory experiments were conducted using soil collected from the site before the ethanol release. Microcosms were constructed and dosed with know concentrations of BTEX and ethanol. Autoclaved control microcosms were also prepared. Microcosms were sampled quarterly and removal rates were compared over time. The metabolism of ethanol by microorganisms uses a variety of electron acceptors. In the field experiment at Vandenberg AFB, the presence of ethanol depleted sulfate due to demand for electron acceptors. At bench scale, the addition of ethanol stopped the natural methanogenic biodegradation of benzene. The effect persisted long after the ethanol was gone. In the field, this could cause the benzene plume to expand.