Mathematical Modelling of the Anaerobic Digestion Including the Syntrophic Acetate Oxidation

Anaerobic digestion is an effective biotechnological process for treatment of different agricultural, municipal and industrial wastes. However, it is a very unstable process in regard to the biogas reactors operation. This is due to the complicated interactions between different microbial species as well as of the complex transformations of the organic matter affected by a variety of environmental factors. Anaerobic digestion process can be divided in four main stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis. The syntrophic acetate oxidation is a two-stage process mediating by two different phylogenetical microbial groups, living in syntrophic consortia: acetate oxidizing Eubacteria which convert acetate to carbon dioxide and hydrogen, and hydrogenotrophic methanogenic Archae which use carbon dioxide and hydrogen for production of methane. Use of mathematical models is a powerful tool for investigations and optimisation of the AD. In this paper a new mathematical model of the AD of activated sludge from municipal wastewater treatment plants including hydrolysis and the syntrophic acetate oxidation process has been developed and verified experimentally and by computer simulations using Simulink. Analytical computer studies of the model have been performed using Symbolic Toolbox of Matlab.