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,. . U <br /> I <br /> INTRINSIC BIOREMEDIATION OF FUEL <br /> CONTAMINATION IN GROUND WATER <br /> AT A FIELD SITE <br /> D.H. Kampbell', T.H. Wiedemeier2, and J.E. Hansen 3; 'R.$. Kerr Environmental Research <br /> Laboratory, Ada, OK 74820; ZParsons Engineering Science, Inc., Denver, CO 80290; and <br /> 3U S. Air Force Center for Environmental Excellence, Brooks Air Force Base, TX 78235 <br /> I <br /> j <br /> ABSTRACT <br /> A spill of gasoline occurred at an automobile service station in 1986. Oily phase residue <br /> in the subsurface has, for the r na t eight years, continued to release water soluble fuel <br /> hydrocarbons into the aquifer. The site was characterized for implementation of intrinsic <br /> remediation. The subsurface was a beach sand with sea shell fragments. The water table <br /> was near 1.3 meters below ground surface. Surface dimensions over the plume were <br /> about 200 meters downgradient and 60 meters in width. Three points to coincide with <br /> direction of ground water flow were selected in the plume for water quality assessments. <br /> Both methane and trimethylbenzene were used as surrogate tracers to normalize loss of <br /> contaminants. Aerobic respiration and methanogenesis accounted for most <br /> biodegradation obtained. Assimilation capacities of dissolved oxygen, ferrous iron, and <br /> methane distributions when compared to BTEX concentrations showed that the ground <br /> water has sufficient capacity to degrade all dissolved BTEX before the plume moves ; <br /> beyond 250 meters downgradient. Evidence obtained from loss of contaminants, <br /> geochemistry and microbial breakdown chemicals showed that intrinsic bioremediation <br /> technology would be a viable option to restore the site. <br /> KEY WORDS <br /> intrinsic remediation, BTEX plume, aerobic respiration, methanogenesis <br /> INTRODUCTION lowed was reported by Wiedemeier et al. <br /> [1]. Intrinsic remediation of contaminants in <br /> A detailed characterization study was con- ground water incorporates mechanisms of <br /> ducted during March 1994 at a fuel spill lo- biodegradation, sorption, dilution, volatiliza- <br /> cation on Patrick Air Force Base in Cocoa tion, dispersion and advection. All of these <br /> Beach, Florida. Core material and ground processes can operate concurrently during <br /> water samples were collected and analyzed field scale implementation of bioremedia- <br /> to predict the influence of natural attenua- tion technology. The respiration processes <br /> tion on dissolved contaminant migration microorganisms used to bring about a re- <br /> and attenuation. Technical protocol fol- <br /> I <br /> :ai <br /> iration 7.502+C6H6=6CO2+3H2O z <br /> 6N0-3+6H++C6H6=6CO2+6H2O+3N2 <br /> n 60H'+30Fe(OH)3+C6H6=6CO2+30Fe2{+76H2O <br /> tion 7.5H++3.75SO4'+C6H6=6CO2+3.75H2S+3H2O <br /> sis 4.5H2O+C6H6=2.25CO2+3.75CHa <br /> Table 1 ,Benzene biode radation reactions. <br /> 9 <br /> 2 Proceedings of the 10th Annual Conference on Hazardous Waste Research <br />