Bifurcation and stability analysis of a two step model for monitoring anaerobic digestion processes

Abstract

This paper deals with the equilibria and stability analysis of the two step anaerobic model initially proposed by [12] to describe the dynamical behavior of an anaerobic fixed-bed wastewater treatment process. In a first part, the model is analyzed: its equilibria and their stability are established considering qualitative properties of the kinetics. In a second part, it is shown that the overloading tolerance (denoted herein OT), a parameter proposed in [9] to monitor anaerobic processes on-line, may not be suitable for monitoring the system and even causes serious problems under certain functioning conditions. Based on the analysis results established in the first part, a modified OT is proposed and evaluated in simulation

On the dynamic optimization of methane production in anaerobic digestion via extremum-seeking control approach

“…The dynamical characterization of the dynamical behavior for uncontrolled AD process (3-6) is based on the analysis developed in (Benyahia et al, 2012;Hess and Bernard, 2008;Sbarciog et al, 2010). Firstly, if we focused on the subsystem (3-4) it is clear that is closed to a classical two-dimensional chemostat model with monotonic kinetics (Monod-like) but slightly modified by the constant term a.…”

Anaerobic membrane bioreactor modeling in the presence of Soluble Microbial Products (SMP) – the Anaerobic Model AM2b

“…We proved in [2] that the AM2 model has at most six equilibrium points and that it can exhibit a bistability. Here, we propose to modify the reaction network (1)-(2) by adding a new compound SMP, named S. We model the SMP production from the degradation of S 1 , S 2 and the decay of biomasses…”

“…In particular, under some operating conditions (for 0 < m < m c1 ), the system AM2b (7)- (11) behaves exactly as the original system AM2 [2] and functions in bistability. However, under other operating conditions, when the value of m changes the system AM2b can have nine equilibria (for m c3 < m < m c4 ) and functions in quadri-stability while for other values of m, it can function in tristability.…”

“…Our model is based on the modification of the two-step model AM2 proposed in [1] that has been analyzed by [11] in a chemostat and by [2] in a more generic case. In such models, anaerobic digestion is considered as a two-step process:…”

Optimal biogas production in a model for anaerobic digestion

“…After identifying conditions for the existence of two stable equilibria together with an unstable equilibrium, the authors used an approximating system to develop a risk index for operating conditions that are likely going to lead to system failure. A modified risk index was recently defined in [2], which improves predictions for system failure in cases when the concentration of the organic inflow is low. In [24], this model was developed further with the inclusion of additional factors such as the impact of carbon dioxide, a buffer such as sodium bicarbonate, and liquid-gas phase transitions.…”