Reversing Full-Scale ISCO

摘要

A TCE plume had been well-defined at a site located in southern Delaware. A set of full-scale permanganate injections to treat TCE in groundwater proved to be unsuccessful. In addition, hexavalent chromium formation and low pH were observed after the injections. To reverse these conditions, and address the TCE, an alternate remedial approach was taken-injecting a mixture of lactate and dissolved vegetable oil. Within 6 months, the indigenous microbial population responded dramatically, resulting in widespread reductive dechlorination of the TCE. This example of enhanced bioremediation is useful from several respects. Despite injection of a strong oxidant, it is evident that indigenous microbes remain and can rebound in a short time to adequate levels for reductive dechlorination to be effective. No microbes were added to this system. Also, the presence of hexavalent chromium was short-lived and was reversed by the injection of hydrogen donor to create a reducing environment. To suppress potential rebound from subsequent desorption of TCE in the saturated soil, a second injection was performed 6 months after the first.