Transformations of 1,1,2,2-Tetrachloroethane under Methanogenic Conditions

Abiotic and biotic transformations of 1,1,2,2-tetrachloroethane (TeCA) under methanogenic conditions were studied. TeCA degradation started without lag with municipal digester sludge. 1,1,2-Trichloroethane (1,1,2-TCA), trans-1,2-dichloroethene (tDCE), and cis-1,2-dichloroethene (cDCE) were products of biotic transformation, while trichloroethene (TCE) resulted from abiotic degradation. TCE was further transformed to cDCE, vinyl chloride (VC), and ethene. Ethene, VC, and tDCE were the persistent products of TeCA transformations. With the same municipal digester sludge culture, 1,1,2-TCA was removed and converted to 1,2-dichloroethane (1,2-DCA) and VC. 1,2-DCA partially degraded, resulting in chloroethane and ethene formation. Reductive dechlorination, dichloroelimination, and dehydrochlorination simultaneously took place during the degradation of TeCA. Dichloroelimination and dehydrochlorination played important roles in the removal of TeCA and 1,1,2-TCA under methanogenic conditions.