Adaption and restoration of anammox biomass to Cd(II) stress: Performance, extracellular polymeric substance and microbial community

[Display omitted] •Cd(II) at 2 mg L−1 enhanced anammox performance.•Cd(II) at 5 mg L−1 inhibited anammox performance.•The relative abundance of Candidatus kuenenia increased at ≤2 mg L−1 Cd(II).•The SAA, EPS and microbial community could be recovered after withdrawing Cd(II).•Anammox biomass displayed a certain adaption to Cd(II) suppression. Cadmium (Cd) can cause the deterioration of biological systems through inhibiting the enzymes activity and disturbing the microbial metabolism. Although the influence of Cd on conventional wastewater treatment process has been studied, the response of anammox to Cd exposure still remains unclear. This study firstly investigated the adaption and restoration of anammox biomass to Cd(II) stress. Results showed that long-term exposure of anammox bacteria to 2 mg L−1 Cd(II) was beneficial for the reactor performance, while 5 mg L−1 Cd(II) would cause the decline of SAA, extracellular polymeric substance content and relative abundance of Candidatus kuenenia by 40%, 25% and 31%, respectively. Furthermore, these indexes could approximately recover to the initial status after withdrawing Cd(II) from the influent. Overall, the anammox biomass exhibited a certain adaption and restoration ability to the suppression of Cd(II). This study may provide key valuable information for the biological treatment of wastewater containing Cd(II).