Nutrients removal by interactions between functional microorganisms in a continuous-flow two-sludge system (AAO-BCO):...

Area of Science:

• Environmental Science
• Microbiology
• Water Treatment Engineering

Background:

• Denitrifying phosphorus removal (DPR) is crucial for simultaneous nitrogen (N) and phosphorus (P) removal from low COD/N ratio wastewater.
• Understanding the interactions between denitrifying phosphate-accumulating organisms (DPAOs), denitrifying glycogen organisms (DGAOs), and denitrifying ordinary heterotrophic organisms (DOHOs) is vital for optimizing DPR processes.

Purpose of the Study:

• To investigate the performance of a novel anaerobic anoxic oxic - biological contact oxidation (AAO-BCO) system for simultaneous N and P removal.
• To identify the optimal influent COD/N ratio for maximizing DPR efficiency and understand microbial community dynamics.

Main Methods:

• A novel AAO-BCO system was utilized to treat actual sewage with varying influent COD/N ratios (3.5-6.7).
• Stoichiometric calculation methodology was employed to quantify the contribution of different microbial groups to nutrient removal.

Main Results:

• High removal efficiencies for total inorganic nitrogen (TIN) (76.5%) and phosphate (PO43-P) (94.4%) were achieved at COD/N ratios between 4.4 and 5.9.
• Optimal DPR performance (88.7%) and phosphorus uptake capacity (1.84 mg/mg) were observed at a COD/N ratio of 5.7 ± 0.2, with a predominance of DPAOs.
• Low COD/N ratios (3.7 ± 0.2) favored GAOs, limiting N removal, while high COD/N ratios (6.5 ± 0.2) led to DOHOs outcompeting for NO3-, hindering DPR.

Conclusions:

• The AAO-BCO system demonstrates robust performance for simultaneous N and P removal, particularly at moderate COD/N ratios (4.4-5.9).
• Microbial community composition, specifically the balance between DPAOs, GAOs, and DOHOs, significantly influences DPR efficiency.
• Stoichiometric analysis provides valuable insights into nutrient removal mechanisms, aiding in the optimization of DPR systems facing fluctuating carbon sources.