High levels of the chlorinated solvents tetrachloroethene (PCE) and trichloroethene (TCE) occur in groundwater beneath a manufacturing facility in southern Sweden. Regulatory authorities require groundwater remediation, but Swedish environmental consultants had 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 which was the most cost effective and to develop a remedial strategy for full-scale groundwater remediation at the site.

Geosyntec provided technical expertise for a KB-1® bioaugmentation design at the ERD pilot test site and supported evaluation of both the ISCO and ERD pilot tests. KB-1 is a microbial culture containing naturally occurring strains of Dehalococcoides organisms that are used to degrade chlorinated solvents to non-toxic ethene. Although both ISCO and ERD performed well in the pilot tests, it was concluded that ERD is the most cost-effective treatment.

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.