[Effects of operating parameters on organic toxicity of sludge treating synthetic bisphenol A wastewater]

In order to investigate the influence of hydraulic retention time (HRT) and sludge retention time (SRT) on sludge organic toxicity in sequencing batch reactors (SBR(S)), the sludge toxicity was compared when HRT and SRT were controlled at various levels. The influents COD were controlled at around 300 mg x L(-1), HRT and SRT were changed from 12 h to 8 h and from 20 d to 10 d, respectively. The effluents COD, BPA contents both in liquid and sludge were measured, and sludge toxicity was also analyzed and compared between the blank group (no BPA content) and BPA control groups (40 mg x L(-1)). The results showed that the effluents COD of two SBRs were both below 50 mg x L(-1), and there were no BPA content in liquid and sludge. Furthermore, decrease HRT and SRT is helpful to remove BPA and reduce sludge toxicity. Additional investigation revealed a correlation between the properties of bacterial community and total sludge toxicity by the PCR-DGGE analysis, and different influent compositions and operation parameters were the main reasons for leading the difference of sludge toxicity.