Disturbance rejection control for the dissolved oxygen in a wastewater treatment process

Wei Wei,Zai-Wen Liu,Nan Chen,Min Zuo

doi:10.1177/0020294020909953

Wei Wei, Zai-Wen Liu + Show 2 more

Open Access

https://doi.org/10.1177/0020294020909953

Copy DOI

Abstract

In wastewater treatment processes, the concentration of dissolved oxygen affects the performance of wastewater treatment directly. It is one of the key factors that determines effluent quality of the wastewater treatment. However, a simple closed-loop control has a high-energy consumption, and it cannot guarantee the effluent quality due to large perturbations in wastewater treatment plants, such as the influent rate, the temperature, and the complex biochemical reactions. In this paper, a new disturbance rejection controller is designed to address those perturbations. Dynamics of dissolved oxygen is transformed into a controllable canonical form. Discrepancy between the dissolved oxygen dynamics and the controllable canonical form is estimated by a disturbance observer and compensated by a control law. Stability and the bound of tracking errors are obtained. Finally, numerical results on the benchmark simulation model number 1 are presented to confirm the proposed method.

Highlights

Shortage of the fresh water and increasing demand on it are a prominent contradiction
We focus on the disturbance rejection control and its application on the WWTPs
In new disturbance rejection control (NDRC), a controllable canonical form is taken as the standard dynamics

Summary

Introduction

Shortage of the fresh water and increasing demand on it are a prominent contradiction. Motivated by improving system performance, a new disturbance rejection control (NDRC) is designed to achieve satisfied dissolved oxygen (DO) concentration in WWTPs. In NDRC, a controllable canonical form is taken as the standard dynamics. DO: dissolved oxygen; IAE: integral of the absolute error; ISE: integral of the squared error; DEVmax: maximal deviation from the set point; NDRC: new disturbance rejection control; SOFC: self-organizing fuzzy control; PI: proportional–integral. It means that NDRC has much stronger disturbance rejection ability, and it is able to achieve superior performance in this case. That, in stormy days, NDRC still has much stronger disturbance rejection ability than PI

Discussion

Findings

Conclusion