Two-step model based adaptive controller for Dissolved Oxygen control in Sequencing Wastewater Batch Reactor

Dissolved Oxygen (DO) concentration is a crucial parameter for efficient operation of biological processes taking place in the activated sludge Wastewater Treatment Plant (WWTP). High-quality DO control is difficult to achieve because of complex nonlinear behavior of the plant and substantial influent disturbances. A method to improve the Direct Model Reference Adaptive Control (DMRAC) technology in application to DO tracking for a Sequencing Batch Reactor (SBR) is proposed. Classic DMRAC is ineffective when applied to the SBR operating with step-feed strategy in the presence of influent fluctuations. It has been shown that additional stepwise adaptation of DMRAC parameters (learning rates, anti-windup filter gains, and starting points) can improve the quality of DO control within a wide operating range. Simulations were done using validated SBR and aeration system models. The solution was validated by comparing with classic DMRAC. Reduction of the Integral Square Error (ISE) indicator by 75% on average was achieved for DO control, as compared to classic DMRAC.