Model-based evaluation of competition between polyphosphate- and glycogen-accumulating organisms

Abstract

Many studies show that glycogen-accumulating non-polyphosphate organisms (GAOs) can compete with polyphosphate-accumulating organisms (PAOs) for organic substrate under anaerobic conditions and may indeed cause the deterioration of enhanced biological phosphorus removal (EBPR) systems. Understanding their behaviors in an anaerobic/aerobic (A/O) system at different operational conditions is essential in developing control strategies that ensure EBPR. A model-based evaluation of competition between PAOs and GAOs under different operational conditions was presented in this study. At 30 °C and a 10-day sludge age, the dominance of GAOs in the A/O sequencing batch reactor (SBR) was strongly dependent upon their considerable kinetic advantage in anaerobic acetate uptake. At 20 °C and a 10-day sludge age, the kinetic advantage of GAOs in anaerobic acetate uptake could be less, compared to that at 30 °C and a 10-day sludge age, leading to the relative dominance of PAOs and a stable phosphorus removal in the A/O system. At 30 °C and a 3-day sludge age, the parameters responsible for determining the aerobic distribution of anaerobically stored X PHA for both PAOs and GAOs, other than kinetic parameters of anaerobic acetate uptake, are important for them being dominant in the A/O SBR. In a situation when the q PHA , P value is lower than q PHA , G but comparable, PAOs may still be dominant in the A/O SBR, presumably because their aerobic conversion fraction of biomass production from PHA was higher than that of the GAOs.