Optimal Subsystem Decomposition and Resilient Distributed State Estimation forWastewater Treatment Plants

The wastewater treatment plant (WWTP) is an important step in water recycling (Qu et al. 2013). WWTP is usually composed of several interconnected operation units. State estimation is a process of constructing system state based on output measurements and system model. State estimation is important for WWTP since many related states in WWTP cannot be measured or affected by significant noise. Cyber-physical systems (CPS) integrates communication network, engineering, computing, and physical process components and uses the network to realize the interaction between computing processes and physical processes (Zhang et al. 2021) and operate physical entities in a remote, reliable, real-time, secure (Wang et al. 2021), and cooperative way (Ding et al. 2020). When the distributed state estimation of sewage treatment system is carried out, in order to improve the efficiency, two or more computer equipment are often used for calculation and processing. That is, each computer processes a subsystem state estimation. Among the subsystems, the state information needs to be exchanged through the communication network. Therefore, WWTP can be regarded as an information physical system in which physical processes and networks are connected (Anter et al. 2020; Wei et al. 2020). In Barbu et al. (2011), deterministic and stochastic observers were developed. A univariate statistical technique was proposed in Baklouti et al. (2018) to enhance the monitoring of WWTP and the state estimation of two-time scale nonlinear systems was considered in (Kiss et al. (2011)). In Busch et al. (2013), a synthesis method based on optimization for design and estimation of sensor networks was proposed and was applied to the WWTP system.