Optimal time control of bioreactors for the wastewater treatment

In this work the time optimal control problem for a biological sequencing batch reactor, used for wastewater treatment, is solved. This operation strategy increases greatly the efficiency of these plants. New is the consideration of the substrate concentration in the input flow, the main disturbance for these systems, as a variable signal and not as a constant parameter. The problem will be solved using a known method based on Green's theorem that allows one to obtain analytically the unique global solution. Furthermore, an optimal feedback control law can be derived that can be made robust against parameter uncertainties and the input disturbance. Simulations of a realistic model of an industrial wastewater treatment plant show the advantages of using an optimal strategy in the control of the plant, since this reduces, among other aspects, the costs of operation and the size of the plant.