Dynamical model development and parameter identification for an anaerobic wastewater treatment process

Abstract

This paper deals with the development and the parameter identification of an anaerobic digestion process model. A two-step (acidogenesis-methanization) mass-balance model has been considered. The model incorporates electrochemical equilibria in order to include the alkalinity, which has to play a central role in the related monitoring and control strategy of a treatment plant. The identification is based on a set of dynamical experiments designed to cover a wide spectrum of operating conditions that are likely to take place in the practical operation of the plant. A step by step identification procedure to estimate the model parameters is presented. The results of 70 days of experiments in a 1-m(3) fermenter are then used to validate the model.

Robust Fuzzy Control for Anaerobic Digestion System Subject to Unknown Inputs

“…Since the state variables are not all available for measurement, a two stage design procedure is used to decouple the controller design from the observer design [17]. As indicated in [6], the fuzzy sliding mode observer allows a robust state estimation of the anaerobic digestion subject to unknown inputs.…”

“…There are several models available for the simulation of the anaerobic digestion of wastewater solids and sludges. Some of these models focus on a specific component of anaerobic digestion, such as microbial kinetics, while others attempt to encompass the overall digestion process [3], [17]. …”

Steady state multiplicity of two-step biological conversion systems with general kinetics

“…In a (simplified) two-step anaerobic digestion model [3], x 1 represents organic substrate, which is consumed by acidogens (x 3 ) to VFA (x 2 ), which methanogens (x 4 ) subsequently convert to methane gas (P ). In an alternative two-step anaerobic digestion model [7], VFA (x 1 ) is converted to hydrogen (x 2 ) by acetogens (x 3 ), while hydrogen is further converted to methane (P ) by methanogens (x 4 ).…”

“…As a rule, these kinetic expressions all consider substrate limitation, but they differ in the number and type of inhibition terms considered -from no inhibition terms to all inhibition terms in (5) and (6). Anaerobic digestion processes are usually described with substrate inhibition of the second reaction as the only inhibition effect (see [3]; [14]), which is described by the term in d 2 . other parameter values and to other processes satisfying the stoichiometry and general kinetics given by (1) and (3)- (6), respectively.…”

“…the associated reaction kinetics. Anaerobic digestion is another widely applied wastewater treatment process that can be described as a two-step conversion system [3]. During this process, which takes place in absence of oxygen, acidogenic bacteria consume organic substrate and produce volatile fatty acids (VFA), which methanogenic bacteria subsequently convert to methane gas.…”