Long-term impacts of triclocarban on nitrogen removal via the anammox process: Focusing on triclocarban fate and microbial community shift

The presence of triclocarban (TCC) in municipal wastewater has potentially inhibitive effect on anammox process. In the present study, the long-term impact of TCC on the anammox process was investigated via determining nitrogen removal efficiency, TCC fate and microbial community. Results showed that TCC exerted an inhibitory effect on nitrogen removal performance with a 22.9% decrease in ammonium removal efficiency (ARE) at the first 15 day, but it gradually recovered after 45 days TCC exposure. The secretion of extracellular polymeric substances (EPS) was increased to resist the TCC, and the long-term operation enhanced the activity of enzymes associated with anammox process due to the Hormesis effect exerted by microorganisms, indicating the adaption of anammox bacteria. The TCC degradation could reach 73.4% and reduce the stress to anammox bacteria, leading to the recovery of nitrogen removal. The microbiological analysis revealed that after 45 days of exposure to TCC, there was a gradual shift in the dominant bacterial group from Candidatus_Jettenia to Candidatus_Brocadia due to its higher semi-saturation constant (Ks) to NH4+-N. Moreover, the denitrifying bacteria (i.e., Thauera) was detected and the TCC degraded product (e.g., β-ketoadipic acid) could be as its carbon source. The Pseudomonas capable of degrading TCC was accumulated, consistent with TCC degradation. Overall, the findings in present study provided the insight mechanism of TCC on annamox process.