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In this paper, the robust regulation of volatile fatty acids (VFA) and total alkalinity (TA) is addressed to improve the stability of continuous anaerobic digestion (AD) processes. The control scheme is derived from an AD model that includes TA as state variable and it is composed of a model-based multiple-input multiple-output feedback control and an extended Luenberger observer which not only allows the estimation of the process kinetics and variations in the influent composition but also the introduction of an antiwindup structure. The wastewater flow rate is used to regulate the VFA concentration, whereas an alkali solution is added directly to the digester to regulate TA. The controller performance is evaluated via numerical simulations showing excellent responses under the influence of control input saturations, noisy measurements, load disturbances and uncertain kinetics. Finally, it is shown that well-known practical stability criteria for AD processes can be also fulfilled by the proposed control scheme.

International audience; This paper is focused on the experimental implementation of a robust control scheme for the regulation of volatile fatty acids (VFA) in continuous anaerobic digestion processes. The robust scheme is made of an output feedback control, and an extended Luenberger observer is used to estimate the uncertain terms of the process (i.e., influent concentration and process kinetics). The control scheme is implemented in a pilot plant up-flow fixed-bed reactor that is treating industrial wine distillery wastewater. The performance of the robust scheme is tested over a period of 36 days, under different set-point values and several uncertain scenarios, including model mismatch, badly known parameters, and load disturbances. Experimental results show that the VFA concentration can be effectively regulated over a wide range of operating conditions. In addition, it is shown that the control scheme has a structure that improves its performance in the presence of noisy measurements and control input saturations.

This paper deals with the simultaneous regulation of volatile fatty acids (VFA's) and total alkalinity (TA) in anaerobic digesters. The control scheme is conformed by an output feedback control and an extended Luenberger observer used to estimate the uncertainties associated to the controlled states ( i.e. , kinetics terms and inlet composition). The inlet flow rate is used to regulate the VFA's concentration, whereas an alkali solution is added directly to the digester for the regulation of the TA concentration. The control scheme is evaluated via numerical simulations under different operating conditions. Results show that the control law is capable to regulate the VFA's and TA despite of load disturbances, uncertainties in the kinetics terms, noisy measurements and control inputs restrictions.

This paper presents the design and the experimental validation of a nonlinear control approach for the regulation of volatile fatty acids (VFA) in an anaerobic digester. Such an approach is conformed by an output feedback control and an extended Luenberger observer which allows the estimation of the uncertain terms associated to the VFA dynamics (i.e., in∞uent composition and kinetic terms). The nonlinear approach is experimentally validated in a 0.528m 3 up-∞ow flxed-bed anaerobic digester used for the treatment of industrial wine distillery wastewater. The experimental results show that the VFA regulation is achieved in spite of uncertain kinetics, restrictions in the control input and unknown load disturbances. Copyright c ∞2007 IFAC

This paper deals with the robust regulation of volatile fatty acids (VFA) in an anaerobic digester. The digester is used for the treatment of industrial wine distillery wastewater. The robust approach is composed by an input-output linearizing feedback control and a Luenberger observer used to achieve the VFA regulation in spite of modelling errors (uncertain kinetics), actuator restrictions and load perturbations due to uncertain changes in the influent composition. The robust stability of the control approach is evaluated via numerical simulations under different operation conditions.