Evaluation of Biodegradation Potential of Carbon Tetrachloride and Chlorophenols under Acidogenic Condition

Biodegradability of chlorinated aliphatic (carbon tetrachloride) and aromatic (chlorophenol) compounds under acidogenic condition was investigated at pH of 5.0 to 5.5. Batch tests were used to evaluate biodegradability, adsorption capacity, and inhibitory effects of the chlorinated compounds on the fermentative microbial consortium. The biodegradability of carbon tetrachloride differed from that of the chlorophenols tested. Carbon tetrachloride was degraded to dichloromethane, and its adsorption onto the biomass was minimal. Inhibition of the acidogenic process was not observed for carbon tetrachloride at 10 mg/L. Chlorophenols (penta, tri, di, and mono) were not degraded at all, even after addition of vitamin supplements, increased incubation time, and increased primary to secondary substrate ratio. Chlorophenol removed from the aqueous phase by adsorption can be recovered from the acidogenic sludge. Pentachlorophenol was inhibitory to the acidogenic culture, whereas 2-chlorophenol was not. Microbial community analysis revealed the bacteria therein were primarily rumen and enteric bacteria. The results showed that it is possible to dechlorinate at least an aliphatic chlorinated compound under acidogenic conditions.