ARX and NARX Modeling and Control of a Continuous UV/H2O2 Photoreactor for the Aqueous PVA Degradation

Water-soluble polymers are commonly employed as additives in many manufacturing industries, raising the need to treat sewage contaminated with water-soluble polymers to prevent persistent pollutants from entering our environment. The advanced oxidation process (AOP) UV/H2O2 is great at non-selectively degrading organic, polymeric compounds. However, most of the available information came from our research group, and there exist many gaps in other previous studies. The first part of this study presents a comprehensive literature review, modeling, and development of a control strategy of the UV/H2O2 process in degrading water- soluble polyvinyl alcohol (PVA), a commonly used polymeric additive.

The second part comprises the dynamic modeling using UV/H2O2 photoreactor identification. The input-output model development was performed using the linear AutoRegressive with eXogenous input (ARX), non-linear ARX (NARX), and Hammerstein-Wiener techniques sigmoid-network-based NARX produced the best representation of the process dynamics. The design of PID controllers tuned using ARX and sigmoid-network-based NARX models is discussed, and the controller performance is analyzed for set-point tracking and disturbance rejection. The closed-loop response of ARX-PID and NARX-PID are deemed adequate. The NARX-PID seems more suitable for the studied process, whereas the ARX-PID has lower IAE and produces a more aggressive controlled output response, but it is robust in disturbance rejection. Thus, ARX-PID is adequate for frequent process disturbances but less for process set-point tracking.