Toxicity and biodegradation of chlorophenols in anaerobic propionate enrichment culture

The fate of four trichlorophenols (TCP), six dichlorophenols (DCP), and three monochlorophenols (CP), were studied in anaerobic propionate enrichment systems. TCPs were more toxic than DCPs and CPs; 2,4,5-TCP was most toxic to the propionate users among the 13 chlorophenols studied in this research. Most chlorophenols were dechlorinated reductively to less chlorinated compounds and/or phenol. Dechlorination at the ortho position was observed most frequently. The overall removal of the selected chlorophenols by anaerobic propionate enrichment systems were in the following order: 2,3,5-TCP > 2,3,6-TCP > 3,5-DCP > 2,4-DCP > 2-CP > 3,4-DCP; 2,3-DCP; 2,5-DCP > 3-CP, 2,4,5-TCP > 2,6-DCP > 2,4,6-TCP > 4-CP.