Effects of aluminum ions on anaerobic ammonium oxidation granular sludge systems: Performance, microbial characteristics and mechanisms

Abstract

Anammox has a very broad application for the treatment of low carbon/nitrogen and high ammonia nitrogen wastewater. In sewage treatment, the anammox granular sludge systems would be affected due to a large number of aluminum salt coagulant or phosphorus removal agent. Therefore, this paper investigated the effect of aluminum ions on the nitrogen removal performance and sludge characteristics of anammox granular sludge. Under low-concentration conditions of aluminum ions (5–20 mg·L⁻¹), nitrogen removal performance was significantly enhanced, particularly at 20 mg·L⁻¹. However, above 30 mg·L⁻¹ concentration, the anammox system gradually collapsed. In the range of 30–100 mg·L⁻¹, the abundance of anammox bacteria did not change considerably, but the nitrogen removal performance was significantly decreased due to the colloidal layer formed by the hydrolysis of aluminum ions. When aluminum ion concentration was 200 mg·L⁻¹, both the genus Candidatus_Brocadia and hzsB gene copy number were notably reduced, anammox bacteria were significantly inhibited by aluminum ion toxicity. These results indicate that the effects of aluminum ion coagulants on anammox granular sludge system include toxicity inhibition and mass transfer.