| Title |
Adaptive Control and Strategies of Dissolved Oxygen in a Sequencing Batch Reactor |
| Authors |
김동한(Dong Han Kim),김성홍(Seong Hong Kim),정태학(Tai Hak Chung) |
| Abstract |
Dissolved oxygen (DO) is an essential variable to accomodate the aerobic environment for the removal of organics, nitrogen, and phosphorus in a biological nutrient removal process. The proportional-integral-derivative (PID) controller has been commonly used to control DO in a wastewater treatment plant due to simplicity and robustness. However, it is difficult to tune gains of the controller and it can not reflect uncertainties, nonlinearities, and time-varying parameters sufficiently. Especially, DO dynamics in a sequencing batch reactor (SBR) highly varies because of batch operation and the SBR process has little buffer capacity for surplus aeration in the secondary aeration period. The PID controller shows the poor control performance for DO in the secondary aeration period and great maximum overshoot, oscillations, and root mean square error. The autoregressive with exogenous input (ARX) controller of the first order of inputs shows the good performance, but a little unstability due to the control law of minimum variance in the latter period of the first aeration, in which DO dynamics highly varies. The ARX of the second order of inputs shows the better control performance, stability, and softening the control actions. By applying an adaptive control strategy of the dual set-point in the control of DO, the reduced air flow and enhanced denitrification could be obtained. |