Effects of triclosan on microalgal-bacterial symbiosis system operating in stable phase: Performances and mechanisms

Triclosan (TCS) is widely distributed in aquatic environments, and its toxicity poses a significant threat to both ecology and environment health. Previous studies have shown the effects of TCS on microalgae-bacterial symbiosis (MABS) system operating in the logarithmic phase, however, their effects on MABS system operating in the stable phase remain unknown, which is closer to the real aquatic system. This study was conducted to explore the roles of TCS on regulating performance and microbial community structure and activity in MABS system operating in stable phase. The findings showed that a high TCS loading (500 mu g/L) not only impaired pollutants removal performance but also led to cell lysis, resulting in elevating total nitrogen and phosphorus concentrations, which respectively increased by 16.8 % and 633.3 %. And this situation was worsened with the loading increase of TCS. TCS inhibited biomass accumulation in MABS system through reducing microbial activity and accelerating microalgae death. In addition, TCS altered the composition of extracellular polymeric substances, facilitated the aggregation of MABS flocs, and induced the changes of cell membrane properties and cellular oxidative stress. Notably, the inhibited phenomenon caused by TCS accumulated in MABS system operating in stable phase was more serious than that operating in logarithmic phase. This case led to nutrients outflow and then the deterioration of water quality. The findings of this study provided valuable references for understanding the influence of TCS on MABS system treating water/wastewater.