A novel two-stage partial-nitritation/anammox (PN/A) process based on zeolite biological fixed bed reactor for low-strength ammonium wastewater treatment

Abstract

A novel two-stage partial nitritation/anammox (PN/A) process coupled by a zeolite biological fixed bed reactor (ZBFB) and an anammox reactor were proposed for wastewater containing 30 mg/L NH4+-N by long-term operation. The cycle operational results by adsorption and biological desorption in ZBFB showed adsorption effluent NH4+-N maintained at 3.0-4.0 mg/L and the average biological desorption effluent NO2--N was 42.2 mg/L. In ZBFB, free ammonia inhibition on nitrite oxidizing bacteria was the main reason for stable nitrite accumulation performance with nitrite accumulation ratio as 88.70% during biological desorption step. Total nitrogen in the mixture of influent and biological desorption effluent of ZBFB could be removed to less than 15 mg/L by the subsequent anammox reactor. High-throughput sequencing analysis results presented the enrichment of Nitrosomonas and inhibition of Nitrobactor and Nitrospira in ZBFB, and dominance of Candidatua Kuenenia in anammox reactor. All results revealed desirable feasibility for nitrogen removal from low-strength ammonium wastewater by ZBFB combined with anammox reactor.