The demonstration of transformation of chlorinated aliphatic compounds (CAHs) in porous media can be challenging, especially when the products are carbon dioxide (CO2) and chloride ion (Cl-). In a continuous flow column study 13C labeled carbon tetrachloride (CT) was used to demonstrate its anaerobic transformation to 13CO2. A column packed with quartz sand and bioaugmented with Evanite Culture (EV) that is capable of transforming tetrachloroethene (PCE) to ethene and fermenting lactate to H2 and acetate. The column was fed a synthetic groundwater that contained 0.1 mM PCE, unlabeled and later 13C labeled CT (up to 0.1 mM), lactate (1.1 mM) as hydrogen (H2) producing electron donor and sulfate (1 mM) as electron acceptor. After bioaugmentation, effective sulfate reduction and PCE transformation to ethene was achieved with lactate fermenting to acetate and H2. When unlabeled CT (0.015 mM) was added it was completely transformed with a transient build-up of CF and chloromethane, which were subsequently removed below their detection limits. When the CT concentration was increased to 0.03 mM, it was completely transformed with no detectable transformation products. The unlabeled CT was then switched to labeled 13CT at the same concentration (0.03 mM). GC-MS analysis showed that about 85% of 13CT was transformed to 13CO2.  The concentration of 13CO2 was double that present as a natural background due to the bicarbonate buffer in the media plus the CO2 produced from lactate fermentation. When 13CT concentration was increased in steps to 0.1 mM, 85% of the transformed CT continued to be observed as 13CO2. COD digestion of the column effluent showed, the remaining 10 � 15% of the transformed CT (not observed as 13CO2) was present as non-volatile organics, likely acetate. The results clearly demonstrate that high concentrations of CT can be transformed to CO2, while maintaining effective PCE dehalogenation to ethene.

Use of <sup>13</sup>C labeled carbon tetrachloride to demonstrate its transformation to Carbon dioxide in a continuous flow column

248th National Meeting (2014)

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Use of 13C labeled carbon tetrachloride to demonstrate its transformation to Carbon dioxide in a continuous flow column

Use of ¹³C labeled carbon tetrachloride to demonstrate its transformation to Carbon dioxide in a continuous flow column