Remediation of Chlorinated Hydrocarbon Solvents

摘要

A series of laboratory scale "microcosm" studies were undertaken to study the rates of biological (biotic) and non-biological (abiotic) dechlorination of chlorinated hydrocarbon solvents such as trichloroethylene (TCE). Microcosms were seeded with subsurface sediment samples drawn from a contaminated paint manufacturing facility in continental Europe, and incubated under a variety of ( anaerobic conditions to determine TCE removal rates by cometabolic oxidation, biological reductive dechlorination, and non-biological reductive dechlorination catalysed by supplementary additions of zero-valent Iron. Control microcosms conducted in parallel included incubations in the absence of sediments, and in the presence of sediments previously sterilised by autoclaving. TCE was added at an initial concentration of 6 mg/1 in all microcosms, together with methanol as a supplementary carbon source. The naturally-occurring abiotic dechlorination rate for TCE was determined to be 0.2μmole TCE degraded daily per litre of microcosm (0.2μmole/1/d). The biological reductive dechlorination rate was also 0.2 /μmole/l/d. The addition of zero-valent Iron (as coarse Iron filings) to a level of 12.5 g/1 increased the abiotic dechlorination rate to 0.6 /μmole/l/d in sterile microcosms. The dechlorination rate increased to 1.0μmole/1/d with the addition of 37.5 g/1 coarse Iron filings. Individual bacterial strains isolated from the sediments used in the microcosm studies have been found to have a high naturally-occurring resistance to heavy metals including copper, chromium, cobalt and lead. A number of experimental tools including biosensors, ion-specific electrodes, and growth response curves have been employed in an attempt to estimate the bioavailability of added metals to bacteria in both solid and liquid media.