Improving simultaneous N, P, and C removal and microbial population dynamics in an anaerobic–aerobic–anoxic SBR (A-O-A-SBR) treating municipal wastewater by altering organic loading rate (OLR)

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To assess the impacts of the influent organic loading rate (OLR) on the performance of an improved sequencing batch reactor (A-O-A-SBR system), four OLRs (1.35, 2.03, 2.70, and 3.38 g-COD/L/d) were used for enhancing simultaneous N, P, and C removals in the system. Results showed that high simultaneous N, P, and C removal efficiencies of the A-O-A-SBR were achieved with an OLR of 2.03 g-COD/L/d. The corresponding TN, TP, and COD removal efficiencies were 98.10%, 87.01%, and 93.43%, respectively. Dominant phyla, including Proteobacteria, Planctomycetes, Candidatus Saccharibacteria, Bacteroidetes, and critical genus Thiothrix, and essential classes such as Gammaproteobacteria, Betaproteobacteria, Sphingobacteriia, contributed to the excellent A-O-A-SBR performance. Functional genes forecasts demonstrated that the metabolic potential on pollutants degradation metabolism improved with the proper OLR condition.