Modelling anaerobic biomass growth kinetics with a substrate threshold concentration (original) (raw)

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Mathematical Study of a Two-Stage Anaerobic Model When the Hydrolysis Is the Limiting Step

Processes

A two-step model of the anaerobic digestion process is mathematically and numerically studied. The focus of the paper is put on the hydrolysis and methanogenesis phases when applied to the digestion of waste with a high content of solid matter: existence and stability properties of the equilibrium points are investigated. The hydrolysis step is considered a limiting step in this process using the Contois growth function for the bacteria responsible for the first degradation step. The methanogenesis step being inhibited by the product of the first reaction (which is also the substrate for the second one), and the Haldane growth rate is used for the second reaction step. The operating diagrams with respect to the dilution rate and the input substrate concentrations are established and discussed.

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MODELLING AND SIMULATION OF METHANOGENIC PHASE OF AN ANAEROBIC DIGESTER

Journal of Engineering Research, 2009

A biological dynamic model for the methanogenic phase of an anaerobic digester with and without wall growth factor is developed for the substrate and microorganisms concentration. The model assumes a continuous feed of acetic acid to the continuously stirred anaerobic reactor. The model was numerically solved, without pH restriction, by the semi-implicit Runge-Kutta method combined with step-size adjustment strategy. The model was used for simulations on transient conditions namely the effects of initial conditions on the start-up of a digester and of changing the feed characteristics via a step increase in the influent substrate concentration for both cases of excluding and taking cognisance of microoganism growth on the digester wall. Inclusion of the wall growth factor in the model improves the stability of an anaerobic digester under drastic changes of its operational conditions. Simulated results obtained herein agree exceedingly well with the general observations in the literature.

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Modelling anaerobic biomass growth kinetics with a substrate threshold concentration (original) (raw)

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