Evaluation of simultaneous storage and growth model to explain aerobic biodegradation of acetate

Abstract

Though mathematical models have been developed to describe the process kinetics of microorganisms in activated sludge during the aerobic biodegradation of carbon sources, there is no commonly agreed model yet. ASM3 is a benchmark model which is based on the assumption that substrate is first stored as internal polymers before being used for growth during famine phase. But experimental observations indicated that the storage and growth occur simultaneously during the feast phase. Hence in this study, the evaluation of simultaneous storage and growth model (SSGM) is performed by comparing this with three established models such as ASM1, ASM3 and accumulation model for acetate biodegradation under aerobic conditions. Oxygen uptake rate (OUR) measurements of biomass were carried out through batch experimental studies. The model parameters were estimated by fitting the experimentally observed OUR to the model using the algorithms of the optimization toolbox included in MATLAB. Model calibration reveals that ASM1 model is not suitable to explain the observed experimental OUR during the famine phase implying storage compounds could play important role during that stage. Besides, the model corresponds to accumulation concept is not well fitted though it includes the storage phenomena. While both the ASM3 model and the model for simultaneous storage and growth on substrate can well describe the acetate biodegradation process, the SSGM seems to be sound from statistical point of view. However the OUR data alone is not sufficient to justify the suitability of those models. In this study, the statistically interpreted outcome related to parameter estimation appears to be quite reasonable as compared with previous study.