Nonlinear PI control for dissolved oxygen tracking at wastewater treatment plant

Two‐Level Multivariable Control System of Dissolved Oxygen Tracking and Aeration System for Activated Sludge Processes

“…The airflow required by each diffuser is maintained through positioning throttling valves. Throttling valves are characterized by a nonlinear relationship between the airflow (Q air ), pressure drop across Dp v , and the angular valve position u. Characteristics of the blowers, diffusers, and throttling valves used in the Kartuzy aeration system can be found in literature by Piotrowski et al (2008).…”

“…The article further develops results presented in literature by Piotrowski et al (2004). Contrary to previous articles by Brdys et al (2002), Piotrowski and Brdys (2005), Piotrowski et al (2008), and Duzinkiewicz et al (2009), a nonlinear multivariable MPC is applied to design the ULC. This controller extends to facilities with several aerobic zones supplied by an aeration system of limited capacity.…”

“…In most instances, the aeration system dynamics have been neglected. The following different control technologies have been researched over the years: adaptive controller, including respiration and an oxygen transfer estimator (Yoo and Lee, 2004); optimal controller (Chachuat et al, 2005); adaptive and predictive controller (Chotkowski et al, 2005); on/off controller with genetic algorithms (Holenda et al, 2007); predictive controller Caraman et al, 2007;Holenda et al, 2008); nonlinear multiregional proportional-integral controller (Han et al, 2008;Zubowicz et al, 2010); multivariable proportional-integral-derivative controller; (Wahab et al, 2009); and a neural-fuzzy controller (Mingzhi et al, 2009). Other control strategies of dissolved oxygen control using N-NH 4 ,N -NO 3 , and P-PO 4 measurements have also been designed and tested (Åmand and Carlsson, 2012;Galluzzo et al, 2001;Gerkšič et al, 2006;Lindberg, 1997;Lukasse et al, 1999;Vrečko et al, 2006;Vrečko et al, 2011).…”

“…Energy consumption of aeration processes comprises the most significant share of an energy bill at a WRRF. Articles by Brdys et al (2002), Piotrowski and Brdys (2005), and Piotrowski et al (2008) propose that a biological reactor be coupled with an aeration system and a two-level hierarchical controller to track prescribed dissolved oxygen trajectories. The upper level controller (ULC) prescribes trajectories for the airflows to be delivered into the aerobic biological reactor zones.…”

“…The LLC is synthesized as a hybrid MPC to follow the prescribed set points. The MPC control variables are valves and blowers (Piotrowski et al, 2008).…”