Reductive dechlorination
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Reductive dechlorination is a biological process that is used to describe certain types of biodegradation of chlorinated solvents in groundwater.
[edit] Biological
Tetrachloroethylene (PCE) and trichloroethylene (TCE) contaminants in ground water can be biodegraded by naturally occurring anaerobic bacteria, most commonly dehalococcoides species. This occurs when other anaerobic bacteria present in the contaminated site take electrons from small organic compounds (the "electron donors") and produce H2. The dechlorinating bacteria use the electrons in the H2 to replace a chlorine atom in TCE/PCE.
If the site soil and ground water contain organic electron donors, this process can proceed until all of the chlorine atoms are removed, and TCE is dechlorinated completely via dichloroethene (DCE) and vinyl chloride (VC) to ethylene gas, a harmless end-product. Other solvents, such as 1,1,1-TCA and carbon tetrachloride, can also be degraded by reductive dechlorination.
[edit] Radiation
It is known that by gamma irradiation of PCBs that they can be converted into biphenyl and inorganic chloride, this is formally a reduction of the organic compound as hydrogen is added. See the Polychlorinated biphenyl page for more details of this destruction method. This reductive destruction method works for many organochlorine compounds, for instance carbon tetrachloride when irradated tends to form chloroform and chloride anions.
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