Regulation of nitrogen removal pathways in sulfuric autotrophic denitrification combined with ANAMMOX

Abstract

The process of sulfuric autotrophic denitrification combined with anaerobic ammonia oxidation (ANAMMOX) has attracted attention because of its efficient N removal capacity, low sludge yield and low operating cost. However, the NO2−-N generated by the sulfuric autotrophic partial denitrification (SAPDN) easily continues conversion to N2 in the coupled process. Thus, ANAMMOX cannot occur in the absence of NO2−-N. In this study, the regulation of N removal pathways was studied in the combined system. The N removal performance was evaluated for treating the industrial wastewater in NO3−-N and NH4+-N with the sulfuric autotrophic denitrification combined with the ANAMMOX process. The effects of influent nitrogen load, concentration ratio of NO3−-N/NH4+-N as well as S/N mass ratio on the transformation of nitrogen removal pathway were studied. SAPDN combined with ANAMMOX became the primary nitrogen removal pathway due to regulating the high nitrogen load of 0.83–0.96 kg/(m3·d), average ratio of NO3−-N/NH4+-N ranging from 1.38 to 1.70 in the influent and a low S/N ratio of 1.5. Moreover, the microbial analysis results indicated that Thiobacillus and Candidatus Brocadia became the main functional microbes when the primary nitrogen removal pathway was SAPDN combined with ANAMMOX.