In this thesis, some control strategies to improve the wastewater treatment efficiency and methods to estimate interesting process variables are developed. The work is focused on the activated sludge process. The controller has the possibility to use separate penalties for the part of the control signal which originates from measurable disturbances and the part which originates from unmeasurable disturbances. By adding an external dosage of carbon, the effluent concentration of nitrate can be reduced. For controlling the external carbon dosage, three types of controllers are evaluated in a simulation study.
All controllers utilize feedforward.
The respiration rate and the oxygen transfer function are interesting parameters for process diagnosis and control. Different models of the nonlinear oxygen transfer function and time-varying respiration rate are discussed. The approach is also successfully applied to real data from Kungs ngsverket, Uppsala, Sweden. The control of the dissolved oxygen concentration in an activated sludge process is of considerable importance because of economy and process efficiency. Two strategies for designing a DO controller are developed.