Correlation between microbial diversity and toxicity of sludge treating synthetic wastewater containing 4-chlorophenol in sequencing batch reactors

Effects of hydraulic retention time and proteins on sludge toxicity for 4‐chlorophenol wastewater treatment in sequencing batch reactors

“…The mixed liquor suspended (MLSS) and sludge volume index (SVI) of both SBRs were about 2500 mg/L and 80 mL/g, respectively. Subsequently, the activated sludge was cultivated with synthetic wastewater as described in Zhao et al (). Influent chemical oxygen demand (COD) was controlled at 300 ± 20 mg/L via methanol; N and P were supplied using urea and K 2 HPO 4 to satisfy the requirements of microbes.…”

“…At present, it has confirmed that the ecotoxicity of 4‐chlorocatechol, which is the main metabolite of 4‐CP, is substantially lower than that of 4‐CP, while the ecotoxicity of another metabolite of 5‐chloro‐2‐hydroxymuconic semialdehyde is reported even higher than that of 4‐CP (Admassu and Korus, ; Monsalvo et al, ). In addition, the identified secondary metabolites, which are secreted by microbes under chlorophenols stress, may inhibit the sludge performance and induce sludge toxicity (Zhao et al, ). Therefore, the comprehensive analysis of sludge toxicity caused by chlorophenols’ biodegradation process is essential, while similar studies are seldom reported.…”

“…Previous studies focus on indirectly evaluating the influence of chlorophenols’ biodegradation on activated sludge via chemical analysis, while sludge toxicity is not reflected in this process. However, a luminescent bacterium acute toxicity bioassay can be utilized to determine sludge toxicity for its sensitivity and accessibility (Zhao et al, ), and some other treatment processes can be used to reduce sludge toxicity, just as digestion, photocatalysis and ultrasonic (Anjum et al, ). Besides, in the process of wastewater treatment, the reactor performance is often significantly influenced by the changes of operation parameters as with dissolved oxygen (DO), hydraulic retention time (HRT), temperature and pH (Chen et al, ; Jiang et al, ; Xu et al, ).…”

“…In the process of 4‐CP wastewater treatment, our previous studies have explored the correlation between different molecular‐weight organics in sludge and sludge toxicity in single SBR cycle, the contribution of secretions from microbes on sludge toxicity, the influence of elevated influent 4‐CP loads on main components of polysaccharides and proteins and sludge toxicity, the correlation between the components of polysaccharides and proteins and sludge toxicity and the proteins’ expression in sludge with or without 4‐CP using two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE) technology (Zhao et al, ; Zhao et al, ; Zhao et al, ). And in this study, on the basis of previous studies, 4‐CP wastewater was sequentially treated using activated sludge process in a SBR with HRT of 8 hours.…”

“…And in this study, on the basis of previous studies, 4‐CP wastewater was sequentially treated using activated sludge process in a SBR with HRT of 8 hours. The dynamic change of sludge toxicity was evaluated, and contrasted to a previous study of HRT 12 hours (Zhao et al, ; Zhao et al, ). After the activated sludge was effectively acclimated with 4‐CP, the main proteins in the sludge were analysed and identified via SDS‐PAGE plus MS, and their influence on 4‐CP biodegradation and sludge toxicity was analysed, thus providing more information on the stable operation strategy of industrial wastewater treatment process.…”