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' ENVIROLOG14 • TECHNOLOGIES, INC. ISNI IA-NL CED NATURAL BIOREMEDIATION USING A TIME RVLI:ASE ' OXYGEN COMPOUND ' David G. Bohan and Wendy S Schlert (Envirologic Technologies, Inc , Kalamazoo, Michigan) ' ABSTRACT: A time release oxygen compound was placed into an aquifer to facilitate bioremediation of a BTEX plume at a leaking underground storage tank ' site The objective was to accelerate naturally occurring biodegradation by rising an oxygen release compound (ORC), which slowly delivers oxygen over an extended period of time The treatment area was estimated to be approximately ' 36 m by 21 m, with a 3 m thick contaminated saturated zone containing approximately 13 4 kg of BTEX (benzene, toluene, ethylbenzene, and xylenes) ORC was applied by drilling 50 borings with 10 8 em inner diameter (ID) hollow ' stem augers and installing a precast 10 2 cm diameter cylinder of the compound into the upper three meters of the aquifer BTEX concentrations and microbial ' populations were measured from a series of five monitoring wells in the impacted arca The mass of the BTEX compounds totaled approximately 13 4 kg before ORC installation In the 316 days following the installation of ORC, the contaminant mass has been reduced to 6 2 leg 1 his decrease in contaminant mass is faster than would be expected by natural attenuation Analytical results indicate that there has been a four to 170 fold increase in microbial populations in the ' monitoring wells INTRODUCTION In today's environmental market, major remediation projects for the removal of groundwater contaminants, particularly petroleum hydrocarbons, are being replaced with new concepts which enhance the natural attenuation process ' In general, the most important process in remediation by natural attenuation is degradation of contaminants by naturally occurring bacteria (Wiedemicier, et al , ' 1994) I he bacteria present in the aquifer need a significant quantity of oxygen to degrade petroleum hydrocarbons. With this thought in mind, Envtroingic Technologies, Inc (L-nvirologic) ' implemented the first application of ORC as a source area treatment to augment natural attenuation of petroleum hydrocarbons While ORC barriers had previously been demonstrated to effectively reduce benzene and toluene ' concentrations in field scale pilot testing (Biancht-Mosquera, 1994) a source treatment application had not been attempted ' Background. The aquifer at this site is composed of a complex series of glacial outwash and ice contact deposits Saturation is encountered at a depth of 6 7 ' meters The groundwater flow direction is highly variable within clic aquifer and � � ' d dTE : 90 66--b1 -m50