Kinetic and stoichiometric characterization for efficient enhanced biological phosphorus removal (EBPR) process at high temperatures

A recently reported stable and efficient EBPR system at high temperatures around 30 degrees C has led to characterization of kinetic and stoichiometric parameters of the Activated Sludge Model no. 2d (ASM2d). Firstly, suitable model parameters were selected by identifiability analysis. Next, the model was calibrated and validated. ASM2d was found to represent the processes well at 28 and 32 degrees C except in polyhyroxyalkanoate (PHA) accumulation of the latter. The values of the kinetic parameters for PHA storage (q(PHA)), polyphosphate storage (q(PP)) and growth (mu(PAO)) of polyphosphate-accumulating organisms (PAOs) at 28 and 32 degrees C were found to be much higher than those reported by previous studies. Besides, the value of the stoichiometric parameter for the requirement of polyphosphate for PHA storage (Y-PO4) was found to decrease as temperature rose from 28 to 32 degrees C. Values of two other stoichiometric parameters, i.e. the growth yield of heterotrophic organisms (Y-H) and PAOs (Y-PAO), were high at both temperatures. These calibrated parameters imply that the extremely active PAOs of the study were able to store PHA, store polyphosphate and even utilize PHA for cell growth. Besides, the parameters do not follow the Arrhenius correlation due to the previously reported unique microbial clade at 28 and 32 degrees C, which actively performs EBPR at high temperatures.