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.