Regulation of Volatile Fatty Acids and Total Alkalinity in Anaerobic Digesters

Abstract 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.

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