YUNYupan,DINGJindie,XUEShiyu,et al.Effect of Volume Ratio and HRT on Nitrogen and Phosphorus Removal in Low-oxygen A2/O Process[J].China Water & Wastewater,2026,42(7):58-64.
Effect of Volume Ratio and HRT on Nitrogen and Phosphorus Removal in Low-oxygen A2/O Process
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第42卷
Number:
第7期
Page:
58-64
Column:
Date of publication:
2026-04-01
- Keywords:
- A2/O process; low dissolved oxygen; nitrogen and phosphorus removal; volume ratio; hydraulic retention time (HRT)
- Abstract:
- This study investigated the effect of the volume ratio of anaerobic, anoxic，and aerobic zones and hydraulic retention time (HRT) on the removal of nitrogen and phosphorus from low C/N wastewater when the A2/O process was operated under low dissolved oxygen conditions (DO: 0.5-1.0 mg/L). The results showed that, without the addition of external carbon sources, COD, NH4+-N, TN and PO43--P in the wastewater could be efficiently removed by reasonably controlling the volume ratio of the anaerobic, anoxic, and aerobic zones and the HRT. When the HRT was 12 h and Vanaerobic ∶ Vanoxic ∶ Vaerobic was 3∶4∶7, COD was effectively removed, with the removal rate reaching as high as 91.2%, and the effluent COD concentration was below 20 mg/L. The influent COD was mainly removed in the anaerobic zone, where it was utilized by phosphorus-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs) to synthesize the intracellular carbon source PHA. When the HRT was 9 h and Vanaerobic ∶ Vanoxic ∶ Vaerobic was 4∶4∶6, the system achieved stable nitrogen and phosphorus removal. The effluent TN and PO43--P concentrations were below 11 mg/L and 0.5 mg/L, with removal rates of 81% and 89.2%, respectively. Phosphorus removal in the system was mainly achieved through anoxic denitrifying phosphorus removal and aerobic phosphorus uptake, with denitrifying phosphorus removal being the primary pathway. Nitrogen removal was primarily accomplished through anoxic endogenous denitrification and denitrifying phosphorus removal, accompanied by aerobic partial nitrification and simultaneous nitrification and denitrification. An analysis of the microbial abundance and diversity of the system revealed that the main microorganisms responsible for nitrogen and phosphorus removal were glycogen-accumulating organisms (Candidatus_Competibacter), denitrifying bacteria (Azospira, Terrimonas and Dechloromonas), nitrifying bacteria (Nitrospira and Nitrosomonas), and denitrifying phosphorus?accumulating organisms (Hyphomicrobium).
Last Update:
2026-04-01