Evaluating alkaline microcapsules for pH control and reductive dechlorination of trichloroethylene in sediment

Near neutral pH has been reported in the literature to optimise trichloroethylene (TCE) reductive dehalogenase activity in purified enzyme solutions, cell extracts and cell suspensions. In this study, microencapsulated alkaline buffers were used to evaluate potential use in controlling pH in soil microcosms and columns containing sediment obtained from a TCE-contaminated acidic aquifer at the Department of Energy's Savannah River Site (SRS). Batch microcosm tests were performed to determine the effect of pH on TCE degradation at different set points (4.0, 5.5, 7.0, 8.5, 10.0). Maximum vinyl chloride (VC) production occurred at a pH of 4 (p < 0.001), which is approximately the groundwater pH at the site. Although more nutrient uptake occurred at all other pH levels, indicating that general microbial activity was greater under less acidic conditions, TCE metabolite production was not maximised at neutral pH. Other factors, such as a small population of active dechlorinators, may have limited reductive dechlorination in the SRS sediment.