The evolution of Anammox performance and granular sludge characteristics under the stress of phenol

•The IC50 of phenol on Anammox was 678.2 mg L−1 in short-term test.•The modified non-competitive inhibition model fit the test data well.•The evolution of Anammox performance under phenol inhibition was presented.•Phenol changed stoichiometric ratios and granule properties.•Measures for recovery of Anammox performance are provided.

The short- and long-term effects of phenol on anaerobic ammonium oxidation (Anammox) were evaluated. The short-term impact of phenol on Anammox activity was determined by a batch test, and an IC50 value of 678.2 mg L−1 was calculated. Anammox granular sludge was equally seeded into two identical upflow anaerobic sludge blanket reactors (R0 and R1); synthetic wastewater without phenol was fed to R0 while with varied phenol was fed to R1 to study the long-term effects. The performance of R0 was stable, with a steadily rising nitrogen removal rate of 10.5–21.3 kg N m−3 day−1. However, the performance of R1 was significantly suppressed by an influent phenol concentration of 50 mg L−1, and was recovered and stabilized by applying one or more control strategies. The phenol-mediated inhibition depressed the Anammox activity and biomass, and caused a change of stoichiometric ratios and granule characteristics.