Transformation of clofibric acid in sequencing batch reactor and microbial characteristics

The removal and transformation of clofibric acid (CA), which is a metabolite of clofibrate drugs, in aerobic sequencing batch reactor (SBR) was studied in this paper. By the analysis of CA concentration in the sewage and sludge phase, the biological removal mechanism was shown to be important, achieving 10%–12% of removal efficiency. However, the adsorption effect was relatively weak. High performance liquid chromatography (HPLC) analysis showed that CA mainly produced three biodegradation metabolites: α-hydroxyisobutyric acid, lactic acid and 4-chlorophenol. The α-hydroxyisobutyric acid was the major metabolite, and the second most important was lactic acid. The two substances accumulated for a period, and were then gradually utilised by microorganisms. These results indicated that CA can be transformed into other products during biological treatment although it is refractory. Moreover, the concentration of 4-chlorophenol was very low. Microbial community distribution was analysed by high-throughput sequencing. The dominant phyla were Proteobacteria, Actinobacteria and Bacteroidetes. After addition of CA, the component of both Actinobacteria and Bacteroidetes dropped. For genus level analysis, a new Porphyromonadaceae emerged in the SBR with CA.