High levels of the chlorinated solvents tetrachloroethene (PCE) and trichloroethene (TCE) occur in groundwater beneath a manufacturing facility in southern Sweden. Regulatory authorities have required groundwater remediation, but Swedish environmental consultants have little direct experience with certain in situ remediation technologies.
The team of SWECO VIAK, COWI A/S, and Geosyntec combined forces to evaluate the feasibility of in situ chemical oxidation (ISCO) with permanganate and biological in situ enhanced reductive dechlorination (ERD) using bioaugmentation for treatment of site groundwater. Given that ERD and ISCO are commonly employed for groundwater remediation in neighboring Denmark, these two technologies were chosen for pilot testing at the Sweden site. The objective of the testing was to identify the more cost-effective technology and to develop a remedial strategy for full-scale groundwater remediation at the site.
Geosyntec Scope of Services
Geosyntec provided technical expertise for a KB-1® bioaugmentation design for the ERD pilot test and supported evaluation of both the ISCO and ERD pilot tests. KB-1® is a microbial culture containing naturally-occurring strains of Dehalococcoides organisms used to degrade chlorinated solvents to non-toxic ethene. Although both ISCO and ERD performed well in the pilot tests, it was concluded that more cost-effective treatment was achieved with ERD.
Geosyntec then developed a remedial strategy for design and implementation of a full-scale ERD system that was subsequently approved by the Swedish EPA. Our strategy included a pre-design investigation for mapping the source area using a membrane interface probe along with groundwater modeling to evaluate flow-field impacts of a neighboring municipal extraction well, with an option for incorporating the extraction well as a component in the ERD design.
Geosyntec's involvement in this project led to the first use of bioaugmentation in Sweden for in situ treatment of chlorinated solvents in groundwater. Based on the success of the bioaugmentation pilot test, and with Geosyntec’s support, the Swedish EPA approved ERD as the final remedy for the site.