Trichloroethene (TCE) contamination in groundwater was discovered at a confidential site in Florida in 1995. Remedial actions have been performed at the site since that time, including: excavation of contaminated soil, zero valent iron (ZVI) treatment in the source area and more recently, enhanced in situ bioremediation (EISB) using biostimulation with vegetable oil and bioaugmentation with KB-1?.
The source area was also injected with emulsified zero-valent iron (EZVI). In 2011, Dehalococcoides (Dhc) and vinyl chloride reductase (vcrA) were detected at some areas of the site, however geographical distribution was limited. Ethene was also detected at certain areas indicating that the complete reductive dechlorination of TCE was occurring at the Site. The site conditions were ideal for EISB, with reducing conditions in the sulfate reducing and methanogenic range already present. However, the distribution of vcrA and ethene production across the site was limited. This lead to the full scale implementation of EISB including the use of KB-1? to increase the distribution of vcrA, as well asto promote complete dechlorination across the site. In the fall of 2012 approximately 40,000 gallons of vegetable oil, 20,000 gallons of EZVI, and 472 liters of KB-1? culture were injected at the Site. Six months after amendment injection and bioaugmentation with KB-1?, greater than 50% reduction in TCE has been observed with corresponding increases in ethene. Bioaugmentation led to at least a 60% geographical proliferation of vcrA across the site from baseline. vcrA has reached levels as high as 7x107 gene copies per liter, which is above the level required for high rates of in situ reductive dechlorination and ethene production. Results are very promising in other locations and further proliferation of vcrA and complete reductive dechlorination to ethene is expected.
- Geosyntec Authors: Jeff Roberts, Phil Dennis, Sandra Dworatzek
- Title: Proliferation of vcrA following Biostimulation and Bioaugmentation
- Event or Publication: Florida Remediation Conference
- Practice Areas: Groundwater Assessment and Remediation
- Date: 2013
- Location: Orlando, Florida