Reductive Dechlorination of Chlorophenols in Methanogenic Cultures

Abstract
Anaerobic biodegradation of a group of 12 chlorophenols (2-CP; 3-CP; 4-CP; 2,3-DCP; 2,6-DCP; 3,4-DCP; 3,5-DCP; 2,3,6-TCP; 2,4,5-DCP; 2,3,4,6-TeCP; 2,3,5,6-TeCP; and PCP) was examined in an unacclimated digester sludge culture and in a phenol-enriched, 2-CP and 3-CP acclimated methanogenic culture. The phenol-enriched culture degraded all chlorophenols except 4-CP, whereas the digester sludge culture did not degrade PCP or 2,3,4,6-TeCP. Dechlorination products were observed in the phenol-enriched culture but not in the fresh sludge. Based on the observed dechlorination products, degradation pathways for chlorophenols in the phenol-enriched culture were proposed. The phenol-enriched culture degraded chlorophenols at much higher rates than the digester sludge by dechlorinating at the ortho and meta positions. In both cultures, the rate of degradation depended on the number as well as the ring position of chlorine substituents. Higher rates were generally observed with ortho dechlorination and for compounds w...

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