Set-point regulation of an anaerobic digestion process with bounded output feedback

Abstract

Abstract-This work addresses the robust output feedback tracking problem for a biological wastewater treatment process in the presence of input constraints and limited knowledge on the process parameters. The considered process is an anaerobic up-flow fixed bed biological reactor within a semi-industrial scale pilot plant for the treatment of industrial wine distillery wastewater. A mathematical model describing the dynamic behavior of the biological process is considered and nonlinear control techniques are used to design a bounded output feedback control law. Local asymptotic stability and local set-point tracking of the resulting closed-loop system is proved when the dilution rate is selected as the manipulated variable and the output methane gas flow-rate as the measured and controlled variable. Finally, the implementation of the nonlinear output feedback control law is described and experimental results are reported. It is observed that the proposed controller yields set-point regulation, rejects disturbances and preserves stability despite uncertainty on the kinetic parameters.Index Terms-Bounded output feedback control, continuous biological reactors, input constraints, waste-water treatment plants (WWTPs).

An optimizing start-up strategy for a bio-methanator

“…The most popular ones are robust output feedback control [1][2][3] and adaptive control [4][5][6]. In [7], the authors have reviewed a number of control strategies for anaerobic digestion systems and have concluded that neither the classical nor the advanced control methods have succeeded in overcoming all the difficulties which arise in the efficient operation of these processes.…”

Control of a Bioreactor with Quantized Measurements

“…The (classical) output is the biomass growth (through gaseous production), the control is the dilution rate (see [22] for a review of control strategies). For scalar continuous output, there exists many approaches based on well-accepted models ( [7]), using constant or adaptive yield [18,3]. Some original approaches make use of a supplementary competitor biomass [20].…”

Output Feedback Stabilization of an Anaerobic Digestion Model

“…Anaerobic digestion is a process where microorganisms decompose the organic compounds into biogas (a gas mixture of methane and carbon dioxide). The process can also be adapted to wastewater treatment, because it reduces the chemical oxygen demand (COD) in the outlet stream below a specified value, usually fixed by environmental and safety rules, see e. g. [ 2,7,10 ].…”

“…In this paper we consider a well known model of an anaerobic digestion process, based on two main reactions [ 2,7,8 ]: (a) acidogenesis, where the organic substrate (denoted by s 1 ) is degraded into volatile fatty acids (VFA, denoted by s 2 ) by acidogenic bacteria (x 1 ); (b) methanogenesis, where VFA are degraded into methane CH 4 and carbon dioxide CO 2 by methanogenic bacteria (x 2 ). The mass balance model in a continuously stirred bioreactor is described by the following nonlinear system of ordinary differential equations:…”

“…Such a feedback for this model is proposed and studied by the authors in [ 5,6 ]. There, following [ 2,10 ], the dynamic model (1) is extended by adding an additional (auxiliary) differential equation of the form…”