Effects of different carbon sources on 2,4,6-trichlorophenol degradation in the activated sludge process

The effects of different carbon sources on the enrichment of 2,4,6TCP-degrading microbes and on reactor stability were was investigated using a lab-scale sequencing batch reactor (SBR). Glucose, sucrose, and starch were selected as different carbon sources because of the different molecular weights. The sucrose-fed activated sludge (AS) exhibited faster adaption and higher degradation rates for 2,4,6-TCP in long-term operation and typical cycles compared to that fed with glucose and starch. Large amounts of extracellular polymeric substance (EPS; 117.54 mg/gVSS) were induced from AS after adding starch, leading to a high SVI (191 mL/g) and poor sludge settling. This suggests that macromolecular carbon sources might have a detrimental effect on the reactor operation. Moreover, the high removal efficiency for TOC and chloride ions was achieved in a typical cycle of all SBRs, indicating that AS could completely mineralize 2,4,6-TCP. On average, more than 90% of the COD could be removed in all SBRs during long-term operation. Glucose, sucrose, and starch facilitated the development of a different microbial community compared to the seeding sludge, making Chloroflexi, Actinobacteria, and Proteobacteria the dominant phylum in the corresponding SBR. The microbial abundance associated with the metabolism of 2,4,6-TCP reached 81.02% due to the addition of sucrose. The results of this study could provide a potential guide for the effective selection of carbon sources in the treatment of chlorophenol wastewater.