Control of the dissolved oxygen concentration (DO) in an activated sludge process is of considerable importance because of economy and process efficiency. A strategy for designing a nonlinear DO controller was developed. The basic idea was to take the nonlinear oxygen transfer function into account in the controller design. Simulations illustrated that a nonlinear DO controller outperforms a standard PI controller. This was also confirmed in a pilot-scale plant experiment. A supervision (set-point) controller for the DO is also outlined. Initial simulations showed promising results where the aeration system is used more efficiently and the effluent ammonia concentration could be maintained low.
Lindberg, C. F., & Carlsson, B. (1996). Nonlinear and set-point control of the dissolved oxygen concentration in an activated sludge process. In Water Science and Technology (Vol. 34, pp. 135–142). Pergamon Press Inc. https://doi.org/10.1016/0273-1223(96)00565-3