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Modelling anaerobic degradation of carbohydrates under different feeding strategies

Budiastuti, H., Pullammanappallil, P. and Cord-Ruwisch, R. (2003) Modelling anaerobic degradation of carbohydrates under different feeding strategies. In: National Environmental Engineering Conference, 18 - 20 June, Brisbane, Australia


A mathematical model was developed to describe the anaerobic mineralisation of carbohydrates in continuously and intermittently fed anaerobic stirred tank reactors. The model was based on the Anaerobic Digestion Model No.1 (ADM1) developed by IWA Task Group for Mathematical Modelling of Anaerobic Digestion Processes. Using the fitting parameters and bacterial yields as provided by ADM1, resulted in about 10% error in the COD balance. This error could be rectified by accounting for organic matter produced from microbial decay and by including the anabolic reactions for biomass. Upon selecting appropriate fitting parameters the model could satisfactorily predict the trends of steady state and dynamic conditions of continuously fed digesters. In ADM1 the formation of volatile fatty acids from carbohydrates is modelled as occurring in fixed ratios irrespective of loading rate and conditions within digesters. Therefore, it could not predict changes in microbial fermentation behaviour or the long term microbial population. This is the likely reason for its failure of predicting intermittently fed anaerobic digesters. Possible modifications of the model are discussed.

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