Analysis of aeration patterns on carbon source utilization characteristics in anaerobic/aerobic/anoxic process for...

The anaerobic/aerobic/anoxic (AOA) process involves the inevitable consumption of intracellular carbon sources during the aerobic phase, which limits the nitrogen removal efficiency of subsequent endogenous denitrification. Therefore, elucidating the effects of different aeration patterns on endogenous metabolic mechanisms and microbial interactions is crucial. In this study, the characteristics of intracellular carbon source utilization under continuous and intermittent aeration patterns were comparatively analyzed in continuous-flow suspended sludge reactors treating low C/N municipal wastewater. During 210 days of operation, both the continuous aeration system (AOA_C) and intermittent aeration system (AOA_I) achieved a total inorganic nitrogen (TIN) removal efficiency of approximately 90%. The results demonstrated that the AOA_I system effectively reduced the oxidation of intracellular carbon sources within the aerobic zone. However, intermittent aeration was prone to introducing inter-zonal dissolved oxygen (DO) interference, which caused a metabolic lag in the anoxic phase and consequently constrained the rapid utilization of electron donors. Conversely, the prolonged continuous anoxic conditions in the AOA_C system enriched the hydrolytic-fermentative bacterium Caldithrix. This enrichment of Caldithrix enhanced the utilization of extracellular polymers and cellular decay products, providing additional electron donors for endogenous denitrification. Furthermore, glycogen was identified as the core carbon source driving endogenous denitrification in both systems, with the dominant genus Rubrivivax playing a pivotal role. In conclusion, this study elucidated the impact of aeration patterns on the endogenous metabolic networks of the AOA process from the perspective of carbon utilization mechanisms, providing valuable insights for advancing low-energy, high-efficiency nitrogen removal.