Abstract: Organic pollutant 2,4,6-trichlorophenol (2,4,6-TCP) is commonly found in anaerobic environments such as sediments and groundwater aquifers. To investigate the ability of the anaerobic consortium XH-1 to degrade 2,4,6-TCP, we established anaerobic incubations using 2,4,6-TCP as the substrate and inoculated the incubations with XH-1. Additional subcultures were established by amending with intermediate product 4-chlorophenol (4-CP) or phenol as the substrate. The transformation products of 2,4,6-TCP were analyzed and determined using high-performance liquid chromatography (HPLC). Microbial community structure and key microbial groups involved in the degradation of 2,4,6-TCP were analyzed based on 16S rRNA gene high-throughput sequencing. The results showed that the initial 122 μmol·L^-1 2,4,6-TCP was completely transformed after a 80-day incubation at a rate of 0.15 μmol·d^-1. 2,4-dichlorophenol (2,4-DCP), 4-CP and phenol were identified as the intermediate products. All intermediate products generated from 2,4,6-TCP transformation were completely degraded after being incubated for 325 days. The main microbial groups responsible for the reductive dechlorination of 2,4,6-TCP might be the organohalide respiring Dehalobacter and Dehalococcoides. The subsequent reductive dechlorination of 4-CP to phenol was likely driven by Dehalococcoides. The cooperation between the organohalide respiring bacteria, Syntrophorhabdus and methanogens (e.g. Methanosaeta and Methanofolis) was responsible for the complete degradation of 2,4,6-TCP.

Key words: chlorophenol, anaerobic biodegradation, enrichment cultivation, reductive dechlorination