Nitrogen removal, nitrous oxide emission and microbial community in sequencing batch and continuous-flow intermittent aeration processes

Abstract

Nitrogen removal, nitrous oxide (N2O) emission and microbial community in sequencing batch and continuous-flow intermittent aeration processes were investigated. Two sequencing batch reactors (SBRs) and two continuous-flow multiple anoxic and aerobic reactors (CMRs) were operated under high dissolved oxygen (DO) (SBR-H and CMR-H) and low DO (SBR-L and CMR-L) concentrations, respectively. Nitrogen removal was enhanced under CMR and low DO conditions (CMR-L). The highest total inorganic nitrogen removal efficiency of 91.5% was achieved. Higher nitrifying and denitrifying activities in SBRs were observed. CMRs possessed higher N2O emission factors during nitrification in the presence of organics, with the highest N2O emission factor of 60.7% in CMR-L. SBR and low DO conditions promoted N2O emission during denitrification. CMR systems had higher microbial diversity. Candidatus Accumulibacter, Nitrosomonadaceae and putative denitrifiers (N2O reducers and producers) were responsible for N2O emission.