Supervisory Control System for Adaptive Phase and Work Cycle Management of Sequencing Wastewater Treatment Plant

Abstract

The paper presents the design of the integrated control system applied to Sequencing Batch Reactor (SBR) in a biological Wastewater Treatment Plant (WWTP) in Swarzewo, which operates under activated sludge technology. Based on the real data records, ASM2d biological processes model and aeration system model, hierarchical control system for dissolved oxygen tracking and cycle management is designed. Internal Model Controller (IMC) was applied to control the air flow at the lower control level. Higher level dissolved oxygen controller is based on Direct Model Reference Adaptive Control (DMRAC) method. The supervisory system performs management of reactor work cycle, determines the phase length, controls sludge age, calculates setpoint of dissolved oxygen and adapts parameters of the lower control layer. Proposed control system allowed to: increase the efficiency, improve the quality of outflow and reduce the cost of aeration and chemical treatment plant, in relation to existing solutions in case study plant.

Improving SBR Performance Alongside with Cost Reduction through Optimizing Biological Processes and Dissolved Oxygen Concentration Trajectory

“…The maximum acceptable pollutant concentrations of effluent, according to the water-law permit for Swarzewo WWTP, are listed in Section 2 of this paper. In the course of the conducted tests, three different types of control systems were compared: new control system with optimizer (symbol OP), reference control system mentioned above (symbol CU) and the heuristic system with supervisory controller [29] (symbol HE).…”

“…Each cycle is divided into a series of sequences depending on the intensity of wastewater inflow and the level of contamination. The capacity limit determines the specific volume of the last filling, regardless of the intensity of sewage inflow [29]. The air flow controller (lower level of the presented control system) is responsible for controlling fast-changing variables (seconds), while the adaptive DO controller manages the slowly changing ones.…”

“…Major changes affect the values of learning rates, anti-windup filter parameters and DMRAC starting points, which can be now adjusted during the optimization process to meet various conditions. In addition, the anti-windup filter reduces the impact of the control signal constraints, such as maximum rotational speed of blowers [27][28][29]. This part of the control system uses the control error e DO and Q air to calculate the Q air ref for the lower-level controller mentioned above.…”

“…Each cycle is divided into a series of sequences depending on the intensity of wastewater inflow and the level of contamination. The capacity limit determines the specific volume of the last filling, regardless of the intensity of sewage inflow [29]. Appl.…”

“…In order to maintain the desired SRT, the proper volume of excess sludge has to be pumped out of the SBR. This amount depends on, among others, total suspended solids in the tank and outflow of treated wastewater [29].…”