In Situ Measurement and Numerical Simulation of Oxygen Limited Biotransformation |
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| Authors: | Robert C Borden Michael D Lee J Michele Thomas Philip B Bedient C Herbert Ward |
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| Institution: | Dr. Robert C. Borden is an assistant professor of civil engineering at North Carolina State University (Raleigh, NC 27604). His primary research interest is in the development of field methods and numerical models for the prediction of adsorption and biotransformation of hazardous organic compounds in the subsurface.;Dr. Michael D. Lee is a senior environmental scientist with Biosystems Inc. (2100 Concord Rd., Chester Township, PA 19013). His primary emphasis is on the development of efficient technologies for the bioremediation of contaminated soil and ground water.;Dr. J. Michele Thomas is a research associate with the National Center for Ground Water Research at Rice University (Houston, TX 77251). Her research interests are in the ecology and transport of microorganism in the subsurface at hazardous waste sites. Thomas'interests also include improving current methods of enhanced subsurface biorestoration.;Dr. Philip B. Bedient is a professor of environmental science and engineering and member of the National Center for Ground Water Research at Rice University (Houston, TX 77251). His research interests are in the development and application of ground water quality models.;Dr. C.H. Ward is a professor and chairman of the Department of Environmental Science and Engineering and a director of the National Center for Ground Water Research at Rice University (Houston, TX 77251). Dr. Ward's research interests are in the general field of environmental microbiology, specifically in the area of microbial degradation and transformation of synthetic and petroleum derived hydrocarbons in the subsurface. |
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| Abstract: | Enhanced subsurface biorestoration is rapidly becoming recognized as a valuable tool for the restoration of hydrocarbon-contaminated aquifers and sediments. Previous field and laboratory studies at a former wood creosoting facility near Conroe, Texas, have indicated that insufficient oxygen is the primary factor limiting the biotransformation of polynuclear aromatics (PNAs) in sediments and ground water at this site. A series of laboratory experiments and field push-pull injection tests were performed as part of this project to: (1) study the effect of low oxygen concentrations on the biotransformation of PNAs; (2) identify the minimum concentration of PNAs that could be achieved through the addition of oxygen alone; (3) confirm that enhanced subsurface biorestoration is feasible at this site; and (4) test an existing numerical model of the biotransformation process (BIOPLUME). The laboratory studies demonstrated that biotransformation of the PNAs was not inhibited at dissolved oxygen concentrations as low as 0.7 mg/L although this work did suggest that there may be a minimum PNA concentration of 30 to 70 μg/L total PNAs below which biotransformation was inhibited. The field push-pull tests confirmed that addition of oxygen was effective in enhancing the subsurface biodegradation of the PNAs. The minimum concentration achieved using oxygen alone was approximately 60 μg/L total PNAs. Minimal biotransformation of these compounds was observed without oxygen addition. The numerical model BIOPLUME was tested against monitoring data from the field experiments and appears to provide a good approximation of the biodegradation process. |
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