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ANN l r�It A d .915 x !71: /) Fundamentals of Bioventing Applied to Fuel Contaminated Sites Dr. R. Ryan Dupont . UWRL, UMC-8200, Utah State University, Logan, UT 84322-8200 Bioventing entails the use of soil vapor extraction (SVE) systems for the transport of oxygen to-the subsurface, where indigenous organisms are stimulated to aerobically metabolize fuel components. Bioventing systems are designed and { er and oxygen utilization efficiency, and are configured to optimize oxygen transf operated at much lower flow rates and with configurations much different than those of conventional SVE systems. Bioventing system applications and design are contrasted to those of conventional SVE systems, and the two key elements of bioventing system design evaluation, i.e., in situ microbial activity and air permeability determinations, are highlighted in this paper. The application of 4. bioventing to vadose zone bioremediation was reviewed with particular emphasis on its advantages over aqueous based bioremediation systems in terms of its superior oxygen transfer efficiency. Finally; the application of bioventing and biover;'ting design concepts are illustrated through a case study of JP-4 jet fuel contaminated soil remediation at Mill AFB, Utah. INTRODUCTION BIOLOGICAL REMEDIATION Off' CONTAMI- t t< NATED SOILS Conventional soil vacuum extraction (SVE) systems are de- signed to optimize'system performance to yield a maximum The biodegradation of organic compounds in soil environ- recovery rate of volaciles from contaminated soil.Performance ments has been extensively described in the technical literature, may deteriorate over time, however, due to occluded residual and details of metabolic pathways and microbial populations saturation and enrichment of residual contamination in the responsible for compound biotransformation have been sum- less volatile waste components. marized in a large number of textbooks and reviews on soil F Bioventing has been successfully applied and documented microbial ecology [I,2,3]. For direct biodegradation of haz- for the remediationof residual hydrocarbons remaining in soil ardous organics to be successful, four conditions must be sat- following high rale SVE. Bioventing entails the use of SVE isfied.First,the contaminants of interest must be able to serve systems for the transport of oxygen to the subsurface, where as a carbon and energy source for the indigenous microbial indigenous organisms are stimulated to aerobically metabolize population,i.e.,it must be able to serve as an electron donor. fuel components.'ISioventing systems are designed and con- Secondly, an;appropriate electron acceptor must be available figured to optimize oxygen transfer and oxygen utilization so that energy can be extracted from these electron donors at f efficiency,and are operaced at much lower flow rates and with environmentally significant rates. Thirdly, macro- and mi- cronutrients essential for the production of cellular configurations much different than those of conventional SVE material must be available in the appropriate ratio for microbial growth systems. The bioventingEprocesses is described in this paper, along to proceed unhindered. (A C:N:P mass ratio typical recom- ,' with details of a recommended design approach for full-scale mended for soil bioremediation applications is 100:10:1). Fi- i systems using field in situ respiration and airpermeability wPY Pnv;c�nmentalcnoatdnotobewithin initibitory �ott ,lndigettou