Input concentration estimation for an anaerobic digestion process using EKF and SM observers. A comparative study

It is well known that in the case of the wastewater treatment bioprocesses, including anaerobic digestion process, usually, the complete knowledge of inputs is not available and therefore the implementation of the control laws becomes a difficult problem. Therefore, in the sequel, for the above mentioned process two observer structures, able to estimate the unknown concentration of the input will be presented and analyzed. The paper deals with a comparative analysis of two types of observers: a stochastic one - Extended Kalman Filter and a deterministic one - Sliding Mode Observer. The estimation methods are analyzed in realistic frame taking into consideration the presence of the measurement noise but especially the usual variations in the case of an anaerobic digestion process, such as the variation of the maximum growth rate of the microorganisms. The effectiveness of the proposed observers has been validated by numerical simulations.