Trichloroethylene degradation study

Biotransformation was also strongly indicated as a factor in the degradation of trichloroethylene in a case of soil and groundwater pollution (Milde et al. 1988). The only ethylenes at the point source of pollution were tetrachloroethylene and trichloroethylene however, substantial amounts of known metabolites of these two compounds (dichloroethylene, vinyl chloride, and ethylene) were found at points far from the source. Data from laboratory studies by the same group supported the study authors contention that degradation was due... 

Wackett LP, DT Gibson (1988) Degradation of trichloroethylene by tolnene dioxygenase in whole-cell studies with Pseudomonas putida FI. Appl Environ Microbiol 54 1703-1708. 

In a model aquatic ecosystem, methoxychlor degraded to ethanol, dihydroxy ethane, dihy-droxyethylene, and unidentified polar metabolites (Metcalf et al, 1971). Kapoor et al. (1970) also studied the biodegradation of methoxychlor in a model ecosystem containing snails, plankton, mosquito larvae, Daphnia magna, and mosquito fish Gambusia affinis). The following metabolites were identified 2-(/5-methoxyphenyl)-2-(p-hydroxyphenyl)-l,l,l-trichloroethane, 2,2-bis (p-hydroxyphenyl) -1,1,1 -trichloroethane, 2,2-bis (p-hydroxyphenyl) -1,1,1 -trichloroethylene,... 

In a continuous-flow mixed-film methanogenic column study, tetrachloroethylene degraded to trichloroethylene with traces of vinyl chloride, dichloroethylene isomers, and carbon dioxide (Vogel and McCarty, 1985). In a static-culture-flask screening test, tetrachloroethylene (5 and 10 mg/L) was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum. Significant degradation with gradual adaptation was observed after 28 d of incubation. The amount lost due to volatilization after 10 d was 16 to 23% (Tabak et al., 1981). 

Biological. Microbial degradation of trichloroethylene via sequential dehalogenation produced cis- and /ra/3s-l,2-dichloroethylene and vinyl chloride (Smith and Dragun, 1984). Anoxic microcosms in sediment and water degraded trichloroethylene to 1,2-dichloroethylene and then to vinyl chloride (Barrio-Lage et al., 1986). Trichloroethylene in soil samples collected from Des Moines, lA anaerobically degraded to 1,2-dichloroethylene. The production of 1,1-dichloroethylene was not observed in this study (Kleopfer et al., 1985). 

In a similar study, Zhang and Wang (1997) studied the reaction of zero-valent iron powder and palladium-coated iron particles with trichloroethylene and PCBs. In the batch scale experiments, 50 mL of 20 mg/L trichloroethylene solution and 1.0 g of iron or palladium-coated iron were placed into a 50 mL vial. The vial was placed on a rotary shaker (30 rpm) at room temperature. Trichloroethylene was completely degraded by palladium/commercial iron powders (<2 h), by nanoscale iron powder (<1.7 h), and nanoscale palladium/iron bimetallic powders (<30 min). Degradation products included ethane, ethylene, propane, propene, butane, butene, and pentane. The investigators concluded that nanoscale iron powder was more reactive than commercial iron powders due to the high specific surface area and less surface area of the iron oxide layer. In addition, air-dried nanoscale iron powder was not effective in the dechlorination process because of the formation of iron oxide. 

Titanium dioxide photodegradation rates can be significantly enhanced with H202. With the addition of H202, degradation times of trichloroethylene (TCE) dropped from 75 to 20 min in a study by Tanaka et al. (1989). This enhancement was most likely due to an increase of hydroxyl radicals. The half-lives of pesticides DDVP and DEP were demonstrated to be shortened with the addition of H2Oz (Harada et al., 1990). Similar enhancements were shown for the photodegradation of chloral hydrate, phenol, and chlorophe-nols (Venkatadri and Peters, 1993). 

In laboratory studies, Ravikumar and Gurol [46] monitored the Fenton degradation of pentachlorophenol (PCP) and trichloroethylene (TCE) from sand. In both column and batch studies, they observed the degradation of PCP and TCE with the addition of hydrogen peroxide only. They concluded that iron naturally present in the sand was an effective catalyst for the formation of hydroxyl radical from the added peroxide. However, addition of soluble ferrous salts caused a more rapid degradation of the pollutants, indicating that either insufficient iron was present in the sand or the nature of the iron in the sand made it a poor catalyst. 

Bioremediation has been successfully demonstrated for a variety of contaminant classifications. The majority of the studies have focused on petroleum compounds (BTEX, gasoline, diesel, jet fuel, etc.) because of their widespread occurrence as a contaminant. The other major waste classifications where bioremediation has been successful are solvents (toluene, trichloroethylene, etc.), creosote, pulp and paper, pesticides, textiles, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Table 1 contains a partial list of the microbial genus successfully implemented for these contaminants. For aqueous petroleum contaminants, bacteria and yeasts are the most prevalent degraders. In contaminated soil systems, bacteria and fungi are the microorganisms responsible for degradation. ... 

The removal of perchloroethylene solvents such as the very toxic trichloroethylene (TCE) from soil and water is a rather difficult problem [331]. A bench-scale study was conducted in TCE-contaminated sand columns. The following operation was tested. Foam obtained using the anionic surfactant Steol CS-330 was injected in a pulsed operation, after which artificial groundwater followed, and then foam again. The result was 75% of the initial TCE content. After the TCE-degrading bacterial strain ENV 435 had been added with the second pulse of foam, the result of the treatment was 95-99%. 

Hsu et al. [55] studied a core-shell Ti02/Fe304 C catalyst during gas-phase photocatalytic degradation of trichloroethylene (TCE) by in situ X-ray absorption near-edge structural (XANES) analysis with a home-made photoreaction cell using a 300 W xenon lamp. 

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