ANAEROBIC DECHLORINATION OF CHLORINATED PYRIDINES IN ANOXIC FRESH-WATER SEDIMENT SLURRIES

Transformation of several isomers of dichloropyridine (DCPR) under methanogenic conditions was studied in freshwater sediment slurries. 2,3- and 3,5-DCPR (10 mg/l) were completely removed by day 50 while 2,5- and 2,6-DCPR were not metabolized in the sediment slurries during 6 months incubation. 3-Chloropyridine (3-CPR) was detected as the intermediate product of 3,5-DCPR amended sediment slurries while 2-and 3-CPR were detected in 2,3-DCPR amended sediment slurries. However, 2- and 3-CPR were persistent in the sediment slurries and were not further metabolized. 2-and 3-CPR were also persistent in the sediment slurries amended with these compounds. 2,3- and 3,5-DCPR were transformed at similar rates when both compounds were added simultaneously to the 2,3-DCPR adapted sediment slurries. However, 3,5-DCPR was transformed faster than 2,3-DCPR when both compounds were added simultaneously into the 3,5-DCPR adapted sediment slurries. 2,5- and 2,6-DCPR were not transformed in the 2,3- or 3,5-DCPR adapted sediment slurries. These results indicate that chlorinated heterocyclic compounds were biotransformed by reductive dechlorination as observed for homocyclic compounds under anaerobic condition.