Continuous discrete observer for an activated sludge process with bounded disturbances

A continuous-discrete observer is designed to estimate the concentration of soluble biodegradable organic nitrogen, the biodegradable substrate and bounded disturbance in activated sludge processes. These observers combine a nonlinear Lipschitz continuous time dynamical model with discrete time output measurements. Assuming some persistent excitation conditions to hold and the sampling steps to satisfy some boundedness assumptions, the system observability is ensured and consequently guarantees the convergence of the proposed observer. The stability analysis are performed using a Lyapunov function. The performances of the observer are shown through the application to an activated sludge process model for waste water treatment.