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Development of the Push-Pull Test to Monitor Bioaugmentation with Dehalogenating CulturesPrincipal InvestigatorsJennifer A. Field and Jonathan D. Istok, Oregon State University Objectives: Promising technologies for enhancing in-situ remediation of groundwater aquifers contaminated with chlorinated aliphatic hydrocarbons include the addition of substrates, nutrients, and/or the addition of cultures possessing dehalogenating capabilities. With the recent identification of cultures that survive in the presence of high concentrations of trichloroethene (TCE), bioaugmentation has become a viable alternative for remediating TCE source zones. While this approach may hold promise for field-scale remediation, it is currently difficult to evaluate the degree to which microorganism additions are effective in stimulating contaminant-degrading activity at the field scale. The single-well, "push-pull" test method is a potentially powerful method for obtaining quantitative information about microbial metabolic activities in groundwater aquifers. A push-pull test consists of the controlled injection of a prepared test solution into an aquifer followed by the recovery of the test solution/groundwater mixture from the same location. The overall goal of this project is to further develop the capabilities of the single-well, push-pull test method for quantifying changes in biomass and TCE-transformation potential in the subsurface due to bioaugmentation. The specific objectives are to: 1) develop methods for monitoring changes in biomass upon the addition of dehalogenating cultures and 2) evaluate the ability of the push-pull tests to monitor changes in sediment biomass and TCE-transformation potential resulting from the injection of dehalogenating cultures. Approach: To address the objectives, physical aquifer models will be constructed and packed with aquifer sediment and maintained under fermentative, anaerobic conditions. Laboratory push-pull tests will be conducted in the sediment packs using substrates that can be used to quantify changes in the transport properties and the spatial distribution of biomass before and after the injection of dehalogenating cultures as well as the resulting changes in TCE-transformation potential. Expected Benefits: The benefit of the proposed project is the establishment of the single-well push-pull test as a rapid, low-cost field method for monitoring bioaugmentation. Ultimately, the methods developed for this project can be applied in the field as a means for obtaining quantitative information on dehalogenating activity before and after bioaugmentation. The application of these methods will result in improved field site characterization, assessments of bioaugmentation success at the field scale, and risk assessment at contaminated field sites undergoing bioaugmentation. Project Status (end of 2002): Currently the background activity of sediment collected from a site with known indigenous reductive dechlorination activity is being characterized with respect to the kinetics of TCFE, fumarate, and succinate utilization and product formation. These three substrates are proposed for this project as substrates that can be used to assay for reductive dechlorination potential in situ. These microcosm studies are being used to determine the relationship between TCFE, fumarate, and succinate prior to initiating these assays in PAMs. The PAMs that are in place and under saturated conditions will be driven anaerobic with the introduction of oxygen free water. Dissolved oxygen concentrations will be measured and compared to in situ redox measurements made in collaboration with Dr. Ingle's project. Once anaerobic conditions are established in the PAMs and verified using these two techniques, the background reductive dechlorination activity will be determined by modifying the TCFE and succinate as necessary for use as assays in the PAMs. Progress Reports: 2003
Copyright © Georgia Tech Research Corporation, 2007.
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