Nutrient removal and microbial community in a two-stage process: Simultaneous enhanced biological phosphorus removal and semi-nitritation (EBPR-SN) followed by anammox

Abstract

This study developed a two-stage process, including simultaneous enhanced biological phosphorus-removal and semi-nitritation (EBPR-SN) sequencing batch reactor (SBR), followed by Anammox SBR, to achieve advanced nitrogen (N) and phosphorus (P) removal from real sewage with low carbon/nitrogen (2.82). The long-term operation suggested that removal efficiencies for TIN (86.2 ± 3.5%) and P (95.0 ± 5.5%) were stably obtained, with nitrite accumulation ratio of 98.7% in EBPR-SN SBR. Mechanism analysis indicated contribution of anammox to N-removal being 57.3%–73.7% and superior P-removal due to the majority of removed organics (~74.5%) being stored by polyphosphate-accumulating organisms (PAOs). In EBPR-SN SBR, high-throughput sequencing showed ammonium-oxidizing bacteria was 0.03% while nitrite-oxidizing bacteria was not detected, and PAOs accounted for 30.07%. In Anammox SBR, Candidatus Brocadia (9.75%) was the only anammox bacteria. Remarkably, short aerobic hydraulic retention time (4.29 h) with low DO (0.3–1.2 mg/L) during the whole process provided desirable energy-saving.