Book Description

Enhanced biological reductive dechlorination (EBRD) shows a great deal of promise for efficiently treating groundwater contaminated with chlorinated solvents, but demonstration sites around the country were reporting mixed results. Because individual demonstrations commonly used dissimilar methods, the limitations of the technology were not clear and its applicability at any given site was unknown. As a result, the Environmental Security Technology Certification Program (ESTOP) invested in the development of a standardized protocol to test the technology's effectiveness at any site. A draft protocol was developed that included microcosm and field-testing and an extensive array of sampling and monitoring. Once developed, the draft protocol was applied at four sites to evaluate its overall effectiveness. Data generated at the four sites was used to refine the protocol by eliminating less valuable components while maintaining a testing methodology that provides scientifically defensible data that would satisfy the regulatory community at a reasonable cost. Microcosm testing was used to evaluate the performance of a suite of electron donors, which included yeast extract, lactate, butyrate, benzoic add, propionic add, and acetic add. The testing examined the rate, onset, and extent of dechlorination as well as donor fermentation pathways. Microcosm testing data revealed an apparently heterogeneous distribution of dechlorinating organisms within Individual sites, and that most electron donors will eventually yield the same dechlorination endpoint, though the onset and rate of dechlorination may differ significantly. The electron donor showing the most rapid and complete dechlorination in microcosm studies (usually butyrate) was used in the four 6-month field demonstrations.