Simultaneous anammox and denitrification (SAD) process in sequencing batch reactors

Abstract

This study investigated nitrogen removal by the simultaneous anaerobic ammonium oxidation (anammox) and heterotrophic denitrification (SAD) process in a sequencing batch reactor (SBR) inoculated with suspended activated sludge and immobilized anammox sludge at various total organic carbon/nitrate (C/N) ratios. Synthetic wastewater containing nitrate 100mg-NL−1, ammonium 70mg-NL−1, and acetate 50–250mg-CL−1 was fed to the SBR. Nitrite reduced from nitrate by heterotrophic denitrification was accumulated and removed with ammonium in each cycle operation of the SBR. The SAD process removed nitrate and ammonium effectively (T-N removal, 58–94%) by the high anammox contribution (ca. 80–100%) under low C/N ratios (0.5–1.0). At high C/N ratios of 1.2–2.5, the SAD process maintained T-N removal 67–79% with predominance of heterotrophic denitrification instead of anammox reaction. Results demonstrated that the SAD process performs high nitrogen removal effectively from wastewater with widely different C/N ratios.