Effect of sulfamethoxazole on biological phosphorus removal and its mechanism

As a typical representative of sulfonamides，sulfamethoxazole （SMZ） has a potential threat to biological phosphorus removal process. In order to explore its impact on biological phosphorus removal performance and its mechanism，a sequencing batch reactor was constructed to determine the impact of sulfamethoxazole on reactor performance，explore the impact of sulfamethoxazole on the content of microbial metabolic intermediates（poly-P，PHB and glycogen） and the activity of key enzymes（PPX，PPK）. Moreover， the micro mechanism of sulfamethoxazole on key enzymes were analyzed with molecular docking technology. The results showed that low concentrations of sulfamethoxazole（0.05 mg/L and 0.1 mg/L） had no significant effect on biological phosphorus removal performance，the content of metabolic intermediates and the activity of key enzymes. When the concentration of sulfamethoxazole increased to 1 mg/L，it began to inhibit biological phosphorus removal performance. With the increase of its concentration，the inhibition increased. Furthermore， the synthesis and degradation of poly-P and PHB in microbial cells decreased with the increase of the concentration of sulfamethoxazole， while the synthesis and degradation of glycogen will increase significantly. The inhibition rate of sulfamethoxazole on key enzyme activities increased with the rise of concentration. The molecular docking results showed that sulfamethoxazole combined with the amino acid residues in the enzyme activity center to form a complex，thus changing the structure of the enzyme.