The site hydrology includes shallow alluvial gravels, with overlying fractured mudstone bedrock. The contamination includes a dissolved phase contaminant plume.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
The extent of contamination is not identified; a dense non-aqueous phase liquid (DNAPL) source zone has been identified, with an associated extensive dissolved phase plume.
Major Contaminants and Maximum Concentrations:
- Trichloroethene (var)
- Vertical Chemical Profiling
Comments:
Measuring the performance of in situ remedies demands a combination of complementary performance metrics and interpretative methods. A key objective of the study was to quantify the performance of the enhanced in situ bioremediation remedy using multiple lines of evidence, including hydrogeological, geochemical and microbiological data. This four-year research program used a highly instrumented pilot-scale experiment and research cell to provide spatial and temporal data which can inform the design, operation, and performance assessment of future sites applying similar in situ bioremediation techniques.
- Bioremediation (In Situ)
Comments:
In this pilot study, the source zone and plume were amended with a partitioning electron donor (SRS TM) and bioaugmented with a dechlorinating culture (KB-1TM). The pilot-scale study included a rectangular cell measuring 30 by 4 meters. Multilevel samplers and fully screened monitoring wells were installed to support the study. Performance data were collected from over 500 monitoring locations over a 2-year period. The pilot-scale study included the following assessment activities: tracking the distribution of the electron donor and microbial culture; monitoring and buffering pH changes resulting from rapid dechlorination in the cell; evaluating the decline of the parent compound and evolution of degradation products; and developing a chloride mass balance to evaluate the extent and rate of trichloroethene (TCE) dechlorination. Performance monitoring data included data on volatile organic compounds (VOC), total organic carbon (TOC), pH, chloride and dechlorinating bacteria. Data were synthesized through time-series correlation plots, statistical analysis and 3-D visualization of the changes in the population of the dechlorinator over the course of the pilot-scale study.
Not documented.
The pilot-scale study has been completed. The study demonstrated DNAPL mass removal using enhanced in-situ bioremediation (EISB), with high rates of dechlorination and biotransformation. Complete dechlorination to ethene was observed; the chloride mass balance model documented a flux enhancement factor of 2. Performance data also indicated that dechlorinator population dynamics are sensitive to changes in pH and electron donor supply and may provide a more sensitive performance indicator than VOC data alone.
The study concluded that cell count data for both the source and plume zones can serve as a primary performance metric to monitor in situ bioremediation of DNAPL source areas. The cell count data provide decision-level information to inform operational decisions that optimize treatment rates and efficiency.
Reference:
Wealthhall, G., et. al. 2012. ýEvaluation of Multiple Performance Metrics for Enhanced In Situ Bioremediation of a DNAPL Source Zone". 8th International Conference Remediation of Chlorinated and Recalcitrant Compounds. Page A3. May 21-24.
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