Water distribution networks (WDNs) are critical infrastructures, since the availability of clean water affects population's prosperity and safety. Therefore, suitable water quality is a fundamental requirement that must be assured. However, WDNs are inherently vulnerable to both intentional and accidental contaminations due to their large size and number of served users and access points (e.g., hydrants, consumer connections, tanks, reservoir, and leak points) (Qiu et al., 2021). These are some of the reasons why the safety of drinking water has recently been receiving more attention in the context of water safety plans (WSPs) (Avvedimento et al., 2020;Bartram, 2009).An efficient strategy used for monitoring and securing WDNs against contamination is the installation of a water quality sensor system (WQSS) (AWWA, 2005) that may provide early detection of conditions of risk for the population health. However, the assessment of the contamination risk is highly uncertain due to the variety of contaminants and the conditions for their intrusion in the WDN (time, duration, and location). To maximize the WQSS performance, the most suitable locations must be identified for sensor location, by balancing the system detection reliability and economic investment (Murray et al., 2008). Indeed, securing the whole WDN is infeasible because of budget constraints on the number of installable sensors.In the last decades the problem of the optimal water quality sensor placement has been explored in WDNs, and various methodologies have been proposed to define optimality of WQSSs (Chang et al., 2013;Lee and Deininger, 1992;Uber et al., 2004). However, the challenge is still open especially with reference to the reliability of the adopted hydraulic/water quality models and the applicability of the methodologies to real cases. Furthermore, due to the complexity of WDNs and the huge number of potential contamination scenarios, the problem of the optimal WQSS layout is computationally burdensome, especially for large networks. Therefore, continuous efforts have been made to develop increasingly efficient numerical optimization techniques. For example, Zhao et al. (2016) proposed a branch and bound sensor placement algorithm running on repeated randomly sample subsets of the events to speed up the process. Khorshidi et al. (2018) used the information entropy theory to reduce the computational burden of the problem and warranting objective selection of sensor placement. De Winter et al. (2019) introduced two greedy-based algorithms considering multiple objective functions for investigating the influence of sensor imperfection. Other results were provided by Ciaponi et al. (2019), who combined the water network sectorization and the installation of water quality sensors for improving the detection performance and reducing the investment costs. Giudicianni et al. (2020) presented an approach based on a priori clustering of the WDN and on the installation of sensors at the topologically most central nodes of each cluster in the case of scarc...