Modelling the metabolic shift of polyphosphate-accumulating organisms

Area of Science:

• Environmental Microbiology
• Biochemical Engineering
• Wastewater Treatment Technologies

Background:

• Enhanced biological phosphorus removal (EBPR) is crucial for municipal wastewater treatment.
• Polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) compete for volatile fatty acids (VFAs) under anaerobic conditions.
• PAO metabolic pathways can shift based on intracellular polyphosphate (poly-P) storage.

Purpose of the Study:

• To develop an advanced metabolic model for PAOs that incorporates the ability to switch metabolic pathways.
• To enable the model to represent both phosphorus-driven and glycogen-driven VFA uptake.
• To improve the accuracy of EBPR process modeling under varying conditions.

Main Methods:

• Adapted existing PAO metabolic model equations to allow for pathway switching.
• Incorporated Monod-type expressions to modify stoichiometric parameters based on internal poly-P content.
• Calibrated and validated the model using seven experiments with varying internal poly-P concentrations.

Main Results:

• The model successfully represented the metabolic shift in PAOs at low poly-P concentrations.
• Demonstrated the ability to transition from P-driven to glycogen-driven VFA uptake using unified process equations.
• Sensitivity and error analyses confirmed the model's robustness and satisfactory performance in describing pathway changes.

Conclusions:

• The developed model provides a more comprehensive representation of PAO metabolism in EBPR systems.
• It accurately captures the dynamic metabolic shifts crucial for understanding and optimizing phosphorus removal.
• The model's robustness allows for wider applicability across diverse EBPR plant operating conditions.