Design and Evaluation of Hierarchical Control Strategies for Wastewater Treatment Plants Using Bürger-Diehl Settler Model in BSM1 Framework

Abstract

In this paper, the well-known Benchmark Simulation Model No. 1 (BSM1) was modified with a new model for the secondary clarifier to improve its prediction capability. The Bürger-Diehl settler model was integrated with the activated sludge models to represent a complete model of an activated sludge train. Based on this integrated model, twin-level control strategies were developed to enhance the model effluent quality. The secondary controllers at the lower level were proportional integral (PI) and model predictive control (MPC), and the primary controllers at the supervisory level were MPC and fuzzy controllers. The controllers were developed on the identified plant models using prediction-error methodology. Based on these, different controller combination strategies such as PI-Fuzzy, MPC-Fuzzy, PI-MPC, and MPC-MPC were evaluated. Results indicated that the Bürger-Diehl settler model achieved better effluent quality than the traditional Takacs settler model due to a significant reduction in effluent violations. In terms of overall performance, the PI-Fuzzy controller combination was able to deliver improved plant performance.