A modified active disturbance rejection control for a wastewater treatment process

Waste water treatment process(WWTP) control has been attracting more and more attention. However, various undesired factors, such as disturbance, uncertainties, and strong nonlinear couplings, propose big challenges to the control of a WWTP. In order to improve the control performance of the closed-loop system and guarantee the discharge requirements of the effluent quality, rather than take the model dependent control approaches,an active disturbance rejection control(ADRC) is utilized. Based on the control signal and system output, a phase optimized ADRC(POADRC) is designed to control the dissolved oxygen and nitrate concentration in a WWTP. The phase advantage of the phase optimized extended state observer(POESO), convergence of the POESO, and stability of the closed-loop system are analyzed from the theoretical point of view. Finally, a commonly accepted benchmark simulation model no. 1.(BSM1) is utilized to test the POESO and POADRC. Linear active disturbance rejection control(LADRC) and the suggested proportion-integration(PI) control are taken to make a comparative research. Both system responses and performance index values confirm the advantage of the POADRC over the LADRC and the suggested PI control. Numerical results show that, as a result of the leading phase of the total disturbance estimation, the POESO based POADRC is an effective and promising way to control the dissolved oxygen and nitrate concentration so as to ensure the effluent quality of a WWTP.