EOS Remediation product and design engineers worked with the consulting firm GeoTrans, Inc., a Tetra Tech Company, and Visteon Corporation to pilot test enhanced reductive dechlorination (ERD) as a remedy for a massive TCE groundwater plume emanating from a former manufacturing facility in Indiana (more than a 1,000 feet wide, 8,000 long and up to 75 feet deep).
For the bench test, GeoTrans and Visteon collected and tested soil samples from the targeted circulation cell area for genetic and microcosm analysis. The genetic tests and microcosm studies demonstrated that dechlorinating bacteria were present in site soil at very low concentrations but were not detected in site groundwater. Biostimulation of site soils in microcosms with lactate yielded dechlorination of TCE to cis-1,2-dichloroethene (cis- DCE); however, dechlorination beyond cis-DCE was not observed. Bioaugmentation of the microcosms with halorespiring bacteria innoculum resulted in complete dechlorination of TCE to ethene. Based on these results, the design and engineering team set up a pilot test to determine whether a series of biobarriers could treat the plume and restore the water quality of the regional significant aquifer.
The pilot test consisted of direct push injection of EOS® emulsified vegetable oil with 5 percent lactate at 14 locations in the upgradient portion of a circulation cell. According to Mike Kovacich of GeoTrans, “We observed very positive results within weeks of injection and increasing populations of halorespiring bacteria were observed in the circulation area in subsequent months. VOC, geochemical, and microbial data indicate that complete dechlorination of TCE to ethene was achieved and favorable conditions for reductive dechlorination persisted in the circulation zone more than six months after system shut-down. This pilot test demonstrated that the bench test results could be replicated at the site and the combination of direct injection and circulation accelerated the establishment of the biobarrier. Based on these results, IDEM approved the work plan for full-scale implementation of ERD in the form of biobarriers at the site.” Currently, two biobarriers and a source zone treatment biozone have been implemented at the site.
“The size of the plume required a creative solution, such as the biobarrier approach,” says Mike Zack. “It would have been cost-prohibitive to inject the remediation agent across the entire area of the plume – we would have needed thousands of borings. Essentially, we created a series of biobarrier at key locations within the plume. Contaminants are degraded as impacted groundwater flows through each biobarrier; and now significantly reduced concentrations of contaminants are present as groundwater exits the biobarrier. Our full-scale implementation of this technology has exceeded IDEM’s expectations.”
“We’re thrilled with the results of our design to date and the performance of the EOS® products,” says Mike Zack of Visteon. “Our entire team has been focused on delivering rapid and sustainable results for the people of Indiana who rely on the IDEM to safeguard their water supply.”