Estimation and optimal control design of a biological wastewater treatment process

This paper deals with the on-line estimation and optimal control of a biological wastewater treatment process. The objective of the control is to force the residual substrate and the dissolved oxygen concentrations to track a given reference model despite the disturbances and system parameter uncertainties. The control law is based on one step ahead prediction of the controlled variables and minimization of an appropriate quadratic cost function. The technique is based on direct exploitation of the nonlinear model representing the wastewater treatment process and is coupled with an asymptotic estimator for on-line tracking of simultaneously unavailable states and time varying parameters. The estimated variables are used in the explicit design of the control algorithm according to certainty equivalence principle. A simulation study subject to measurement noise and abrupt jumps in the kinetic parameters shows the feasibility and robustness of the control strategy.