Balancing denitrifying phosphorus-accumulating organisms and denitrifying glycogen-accumulating organisms for advanced nitrogen and phosphorus removal from municipal wastewater

Abstract

Given the carbon limitation of municipal wastewater, the balance of biological nitrogen and phosphorus removal remains a challenging task. In this study, an anaerobic-anoxic–oxic combining with biological contact oxidation (A2/O-BCO) system treating real municipal wastewater was operated for 205 days, and COD-to-PO43--P ratio was confirmed as the key parameter for balancing denitrifying phosphorus-accumulating organisms (DPAOs) and denitrifying glycogen-accumulating organisms (DGAOs) to enhance N and P removal. When DPAOs dominated in nutrients removal, the increase in COD/P from 17.1 to 38.1 caused the deterioration in nitrogen removal performance decreasing to 71.8 %. As COD/P ratio decreased from 81.3 to 46.8, Ca.Competibacter proliferated from 3.11 % to 6.00 %, contributing to 58.9 % of nitrogen removal. The nitrogen and phosphorus removal efficiency reached up to 79.3 % and 95.2 %. Overall, establishing DGAOs-DPAOs balance by strengthening the effect of DGAOs could enhance the nutrients removal performance and accordingly improve the stability and efficiency of the system.