ENHANCED ANAEROBIC BIOREMEDIATION OF CHLOROETHENES IN GROUNDWATER UNDER A BUILDING

Groundwater beneath the basement floor of an actively used building contained chlorinated ethenes at concentrations ranging from 11 to 42 ug/L. A system of extraction/injection wells was installed across the contaminated area in a square grid pattern. Groundwater was extracted, mixed with sodium lactate and yeast extract as an organic carbon and electron source, and re-injected to stimulate anaerobic bioremediation of the chloroethenes. The organic carbon was rapidly metabolized by the indigenous bacteria, and was consumed with a half-life of approximately 23 days. High concentrations of organic carbon, greater than ten times the groundwater electron donor demand, were necessary to sustain sulfate-reducing conditions for an extended period of time and to fuel complete reductive dechlorination to ethene and ethane end products. Within six months of active remediation, the chloroethene concentrations were reduced to the range of less than 0.2 to 4.2 ug/L. It was also necessary to add phosphate buffer to counter the acidity introduced by the lactate and its breakdown products.