Evaluation of various carbon sources on ammonium assimilation and denitrifying phosphorus removal in a modified anaerobic-anoxic-oxic process from low-strength wastewater.

A pilot-scale continuous-flow modified anaerobic-anoxic-oxic (MAAO) process examined the impact of external carbon sources (acetate, glucose, acetate/propionate) on ammonium assimilation, denitrifying phosphorus removal (DPR), and microbial community. Acetate exhibited superior efficacy in promoting the combined process of ammonia assimilation and DPR, enhancing both to 50.0 % and 60.0 %, respectively. Proteobacteria and Bacteroidota facilitated ammonium assimilation, while denitrifying phosphorus-accumulating organisms (DPAOs) played a key role in nitrogen (N) and phosphorus (P) removal. Denitrifying glycogen-accumulating organisms (DGAOs) aided N removal in the anoxic zone, ensuring stable N and P removal and recovery. Acetate/propionate significantly enhanced DPR (77.7 %) and endogenous denitrification (37.9 %). Glucose favored heterotrophic denitrification (29.6 %) but had minimal impact on ammonium assimilation. These findings provide valuable insights for wastewater treatment plants (WWTPs) seeking efficient N and P removal and recovery from low-strength wastewater.