Secondary Impacts of In Situ Remediation on Groundwater Quality and Post-Treatment Management Strategies
ER-2129
Objective
Although substantial progress has been achieved in the remediation and management of hazardous waste sites at Department of Defense (DoD) installations, many sites contain recalcitrant contaminants, such as chlorinated solvents, often in complex hydrogeologic settings. For these problematic sites, significant amounts of the contaminant mass (>10%) are likely to remain even after aggressive source zone treatment. As a result, the subsurface remediation paradigm has shifted from the development of stand-alone technologies toward the integration of complementary remediation technologies that can be deployed in parallel (simultaneously) or in series (sequentially) to more efficiently address difficult remediation scenarios and meet cleanup goals. However, the potential impacts of in situ remediation technologies on long-term groundwater quality and the impacts of an aggressive primary treatment on microbial reductive dechlorination processes are not well understood.
The objective of this project is to develop a fundamental understanding of the impacts of in situ remediation technologies on groundwater quality and relevant subsurface processes. This information is needed to realize the full potential of combined remedies, more effectively treat difficult hazardous waste sites, and develop ecologically sound long-term site management strategies.
Technical Approach
The research is structured around three tasks. In Task 1, researchers will determine the effects of thermal remediation on groundwater quality and subsequent microbiological treatment. The generation of organic acids, hydrogen, and other byproducts in sealed batch reactors will be identified, the magnitude and rate of byproduct release under dynamic heating conditions in the absence of microbial activity will be determined, and changes in the abundance and activity of relevant microbial populations in response to byproduct formation during thermal treatment will be measured. In Task 2, researchers will elucidate the impacts of electron donor delivery on metal sulfide formation and associated reductions in aquifer permeability. The impacts of iron sulfide (FeS) formation will be determined and quantified, oxygenated groundwater will be infused to determine the biogeochemical changes caused by FeS oxidation, and additional column experiments will evaluate the contributions of microbial growth to FeS clogging following biostimulation and bioaugmentation. In Task 3, researchers will evaluate the consequences of pH reductions on reductive dechlorination activity and microbial community structure, and batch culture experiments will determine the pH boundary conditions for reductive dechlorination activity. The effects of fluctuating pH on dechlorination rates and microbial community structure will be monitored in continuous flow reactor vessels, and 1-D column studies will be established to monitor pH effects on dechlorination activity and microbial community composition under continuous flow conditions.
Benefits
This research will provide remediation project managers (RPMs), regulatory officials, and the scientific community with relevant new information about the impacts of thermal treatment and biostimulation on groundwater biogeochemistry and quality and demonstrate the benefits of combined remedies. Key secondary impacts of thermal treatment and biostimulation on long-term groundwater quality will be identified, and strategies will be developed to overcome negative impacts (e.g., pH reduction) and to take advantage of positive impacts (e.g., electron donor release). Guidelines will be provided for RPMs to effectively implement remedies to achieve ecologically sound and lasting solutions. (Anticipated Project Completion - 2014)
Points of Contact
Principal Investigator
Dr. Kurt Pennell
Tufts University
Phone: 617-627-3099
Fax: 617-627-3994
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
- Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
- Model/Software - Computer programs and applications available for download.
- Database - Digitally organized collection of data available to search and access.