COMPARISONS OF PROCESS IDENTIFICATION METHODS AND SUPERVISORY DO CONTROL IN THE FULLSCALE WASTEWATER TREATMENT PLANT

Abstract

Dissolved oxygen (DO) control in the wastewater treatment plant (WWTP) has been the most critical factor in terms of improving the wastewater treatment efficiency and energy saving. However, the result of DO control with simple PID controller is not satisfactory since the dynamics of DO show some time-varying and nonlinear characteristics. The objectives of this study are as follows. First aim is to apply and compare some process identification methods of PID autotuning for stable DO control in a real coke WWTP. Second, a simple algorithm for the supervisory control of set point decision is proposed to decide a proper DO set point for the current operation condition of the aeration basin by estimating the respiration rate simultaneously during process identification step. The key idea in this method is that the DO set point is proportional to the respiration rate, which is the indicator of the biologically degradable load. In the experimental results, process identification methods have been practiced and compared at the modeling and control performance and supervisory control reduced the aeration cost in the full-scale WWTP.