Abstract
| - Aerobic trichloroethylene (TCE) biodegradation wasinvestigated in small-column aquifer microcosms repeatedlyfed solutions containing 6.5 mg/L phenol or 15 mg/Llactateand 250 μg/L TCE every two to three days. Theeffectiveness of TCE cometabolism by an indigenous phenol-fed microbial population declined significantly during a280-day experiment. This behavior, possibly due to thenegative selective pressure of TCE cometabolism, whichleads to the formation of toxic products, has not beenobservedpreviously in shorter term TCE transformation experiments.The addition of microorganisms Burkholderia cepaciaG4or PR1301 to microcosms along with phenol orlactateinitially allowed for substantial TCE degradation but ledtothe eventual depletion of dissolved oxygen and a declinein TCE transformation. After termination ofbioaugmentation,dissolved oxygen levels recovered in all microcosms andthose microcosms that continued to receive phenolreturned to or surpassed previous TCE transformationlevels,while unfed and lactate-fed microcosms lost degradativeactivity. The introduced organisms, however, did notappear to be responsible for the recovered TCE degradationin the phenol-fed, formerly bioaugmented microcosms.The source of activity in these microcosms was notidentifiedbut is likely to have been efficient TCE-transformingindigenous organisms selected by the operating conditionswithin the microcosms.
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