States and variables estimation in an upflow anaerobic sludge blanket reactor for the leachate wastewater treatment using nonlinear observers

In this paper an observer to estimate states and parameters in an anaerobic digestion process of leachate treatment is formulated. The observer is based on a simplified mathematical model. The model is expressed in terms of organic matter, biomass and volatile fatty acids concentrations. It involved a Monod and Haldane kinetics modified included temperature and pH inhibitory effects. The observer shows a good performance for the estimation of substrate and biomass concentration at the outlet of the bioreactor, and the maximum growth rates. The estimation is made from the measurement of the volatile fatty acids concentration at the outflow stream. The observer performance is tested by numerical simulations and a non-linear least squares method is used for model calibration. The results showed a good agreement with experimental data, it evidences the reliability of the observer to estimate states and variables, which implies a minimization of the parametric model uncertainty. The proposed observer is potentially useful for the design of control strategies for bioprocess.

Keywords: anaerobic digestion, bioreactor, nonlinear observer, mathematical model, wastewater.