Effects of dissolved oxygen on the anaerobic/oxic/anoxic simultaneous nitrification, denitrification and phosphorus removal (AOA-SNDPR) process for advanced wastewater treatment and in situ sludge reduction

The anaerobic/oxic/anoxic performing simultaneous nitrification, denitrification and phosphorus removal (AOA-SNDPR) is an emerging approach for advanced wastewater treatment and sludge reduction, while the responses and mechanism to dissolved oxygen (DO) remain much unknown. Herein, the effects of DO (5.88, 3.02, and 0.88 mg/L, respectively) on the AOA-SNDPR were investigated in terms of performance of nutrients removal and in situ sludge yield, as well as the mechanisms. Results showed that excellent removal of carbon, nitrogen, and phosphorus was kept regardless of decreasing DO, while decreased DO significantly strengthened denitrification (residual nitrate of 8.8, 5.2 and 2.2 mg /L, respectively) via stimulating oxic simultaneous nitrification and denitrification (SND) and anoxic post denitrification. A low sludge yield (Yobs) of 0.12 g MLSS/g COD was observed with different DO levels. Besides, physiochemical characteristics of sludge kept robust towards DO, which helped maintain stable reactor performances and spontaneous sludge aggregation. Overall, the AOA-SNDPR process under varying DO levels kept well stability with advanced nutrients removal and in situ sludge yield minimization, which provided new insights into the operational strategies for development of low-carbon and energy-efficient wastewater management. © 2024 Elsevier Ltd