Acidogenic sequencing batch reactor start-up procedures for induction of 2,4,6-trichlorophenol dechlorination

Dechlorination of 2,4,6-trichlorophenol to 4-chlorophenol under acidogenic conditions (pH 5.6–6.5) was successfully induced by manipulating the start-up procedure of an acidogenic sequencing batch reactor (SBR). A stepwise pH reduction from neutral to acidic level during start-up was crucial for inducing dechlorination. Once induced, dechlorination can proceed at pH as low as 5.6 before inhibition occurrs. Optimum pH for maximum dechlorination rate ranged from 6.0 to 6.3. High primary (sucrose) to secondary (2,4,6-trichlorophenol) substrate ratio failed to induce dechlorination. Instead, dechlorination occurred at primary to secondary substrate ratios of less than 103 M/M. A specific maximum trichlorophenol loading rate of 60 μmol/g MLVSS d was achieved before inhibition appeared with onset of acidogenic reactor failure. T-RFLP profile analysis gave evidence that the start-up procedure resulted in the selection of an appropriate microbial community, which resulted in the successful development of an acidogenic consortium capable of degrading 2,4,6-trichlorophenol.