MPC advanced control of dissolved oxygen in an activated sludge wastewater treatment plant

A hierarchical model predictive control for the biological treatment process of an activated sludge wastewater treatment plant is presented. On the basis of a previously developed PI control for the dissolved oxygen concentration and air pressure in the aeration system, an improved optimization strategy based on Model Predictive Control (MPC) is added. The MPC based control loop keeps the output substrate concentration under the legal imposed limitation and computes the optimal reference for the dissolved oxygen concentration. The closed loop performances are improved by choosing the linear prediction model using a gain-scheduling technique. The controllers are designed and simulated on the mathematical model of the WWTP of Romanofir, Talmaciu.