Influence of nitrate supply on performance and stability of a two-stage partial denitrification-anammox system

Résumé fourni par la source

Achieving stable partial denitrification-anammox (PDA) performance remains a major challenge for energy-efficient nitrogen removal because efficient nitrite production and effective carbon removal in the partial denitrification (PD) stage are essential for sustaining subsequent anammox activity. This study investigated the influence of nitrate (NO 3 − -N) supply on the performance, stability, nitrogen transformation, and microbial succession of a two-stage sequencing batch reactor (SBR) comprising a PD reactor followed by an anammox-enriched SBR (A-SBR). Synthetic municipal wastewater containing 120 mg/L COD, 45 mg/L NH 4 + -N, and 40–60 mg/L NO 3 − -N was used to evaluate the effect of NO 3 − -N supply on process performance. Regulating NO 3 − -N supply to the PD reactor optimized the influent NO 3 − -N/NH 4 + -N ratio, thereby establishing a favorable NO 2 − -N/NH 4 + -N ratio entering the A-SBR while enhancing carbon removal in the PD stage, minimizing residual COD transfer, and protecting the subsequent anammox process from COD shock. At an influent NO 3 − -N concentration of 60 mg/L, the integrated system achieved removal efficiencies of 84.63% for total inorganic nitrogen (TIN), 81.49% for NH 4 + -N, and 81.27% for COD. Nitrogen mass balance showed that PD and anammox contributed 66.01% and 33.99% of TIN removal, respectively. Microbial analysis revealed enrichment of functional microorganisms, with Thauera increasing from 0.15% to 8.45% in the PD reactor following NH 4 + -N addition, while Candidatus Brocadia remained the dominant anammox bacterium (0.28–2.45%). These results demonstrate that NO 3 − -N supply is an important operational parameter for maintaining stable two-stage PDA performance and provide mechanistic insights for future evaluation under real municipal wastewater conditions.

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