Theme: 11. Advanced Diagnostic Tools

Topic Area: 11c. Using Omic Approaches and Advanced Molecular Tools to Optimize Site Remediation

Formatted Title:

Sorption-Supported Biological Dechlorination: Laboratory and Field Lines of Evidence

Background/Objectives:

Background/Objectives. Over the past two decades, in situ methods for restoring soil and groundwater have increased in both sophistication and effectiveness. Chlorinated solvent plumes may be bioremediated within targeted areas via various chemical and biological approaches. One relatively new treatment approach is the construction of permeable barriers combining injectable sorbents and electron donors. By combining sorption with enhanced reductive dechlorination, degradation helps maintain active sorption sites and prevents saturation. Thus, the residence time of contaminants fluxing into the treatment zone is increased. This extended retardation within the treatment area is critical to improving treatment effectiveness. Even when dechlorination rates are not optimized, complete contaminant transformation can be achieved within the small footprint of a treatment zone.

Contaminants are frequently not detectible in the aqueous phase within sorbent-amended treatment zones, therefore alternative methods are needed to access treatment system health. Advanced molecular biological approaches such as qPCR and metabolomics can help shed light on the activity of these treatment approaches in the absence of traditional chemical data.

Approach/Activities:

Approach/Activities. As a part of the development of a new solid electron donor, a pilot treatment was performed within a portion of a large chlorinated solvent plume in Michigan. Two treatment areas were selected and treated by applying injectable amendments using a low pressure, direct push approach. In both areas, a solid electron donor and a bioaugmentation culture were applied, and in one area a colloidal activated carbon amendment was co-applied. The sampling schedule for the project included baseline and quarterly qPCR, chemical/dissolved gas, and geochemical analysis.

Results/Lessons Learned:

Results/Lessons Learned. After three years of post-application monitoring, the pilot study has demonstrated successful contaminant reductions, and through the combination of qPCR, ethene, and additional datasets, a convincing case can be made for complete dechlorination of the incoming contaminant mass that continues to flux into the emplaced permeable reactive zone. In addition to the field study, insights into the rates of contaminant degradation within this treated zone from laboratory column studies will also be discussed.

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Sophia Nguyen