Rapid recovery of bisphenol A-inhibited anammox biofilm systems by exogenous AHLs addition

This study investigated the feasibility and underlying mechanisms of rapidly recovering anaerobic ammonium oxidation (anammox) biofilm systems subjected to bisphenol A (BPA) stress through the addition of exogenous signal molecule. Two anammox biofilm reactors were employed, named R1 (control) and R2 (exogenous C6-HSL), respectively. After the long-term shock of BPA, R2 could achieve a total inorganic nitrogen removal efficiency more than 80 % within 6 days and maintained stable performance, whereas R1 required 12 days to reach a similar efficiency and exhibited operational instability. The specific anammox activity in R2 increased by 368.84 %, significantly outperforming the 118.95 % increase observed in R1. Furthermore, key enzyme activities in R2 exceeded their initial levels, with NIR, HZS, and HZO reaching 0.96, 1.79, and 3.19 U/g VSS, respectively. Metagenomic analysis revealed that exogenous C6-HSL would not influence the relative abundance of anammox bacteria, i.e., Candidatus Brocadia, while the relative abundance of functional genes, i.e., nirS and nirK, were enhanced. The underlying mechanism was associated with the accelerated conversion of NO_2^--N to NO, thereby effectively strengthening the anammox metabolic pathway. These findings provided insights into the role of quorum sensing in mediating anammox biofilm system performance in treating BPA-containing wastewater.