The advances in open-source electronics as well as low-cost, miniaturized and portable sensors have enhanced the accessibility of physicochemical measurements of water quality (conductivity, pH, turbidity, COD, temperature, redox, dissolved O₂, energy) (Guyard et al., 2017; Spinelli and Gottesman, 2019). These developments have paved new paths for monitoring and supervising installations dedicated to treating and reusing residual waters thanks to a more accurate spatiotemporal characterization (to the meter, minute). This type of approach, run as a so-called “SMART Project”, has gained considerable favor in other types of environmental applications, e.g. air pollution (Al-Haija et al., 2013), hydrology (Clément et al., 2018; Guyard et al., 2017). The major advantage of these open-source tools lies in their tremendous flexibility (in choosing the measurements, number of sensors, measurement frequency).

Generally speaking, the “poorer” (though not systematically) metrological quality of these sensors is compensated by raising the number of measurement points, thus increasing the level of information detail.

For now, no feedback exists (reliability, uncertainties, constraints) on measurements performed to address problems associated with residual water treatment and reuse. The benefit of such sensors can be anticipated through efforts to sustainably manage the protocols implemented, whether they be intensive or extensive. An increased number of sensors would serve to:

• Improve knowledge of the steps involved in the processes (their dynamics and resilience), by an accurate assessment of key parameters using sensors of both spatial and temporal variability;
• Propose accessible and continuous tracking sensors to assist with system oversight and thereby heighten operator reactivity in the event of dysfunction;
• Contribute new information on the characteristics of processes and procedures, e.g. operational limitations with respect to the maximum load, non-homogeneous flows and their ensuing impact on treatment performance, adaptation of energy expenditures across the various consumer items, modulation of emissions depending on water quality at the outfall.

As an example, in an aeration basin, the benefit would be to derive greater mapping resolution of the parameters: within reactors (e.g. aeration basin) and between reactors (possibility of intermediate measurements). For smaller water authorities and extensive processes, these sensors would offer the possibility of efficient continuous monitoring at a cost deemed to be acceptable, in quickening response times should a dysfunction arise, so as to secure not only treatment plant operations but also the quality of water discharged into the natural environment. The online energy measurement would also serve to remedy the lack of parameter monitoring, in pursuit of optimizing the energy consumption of protocols in place.

This project is aimed at controlling the performance of these new low-cost sensors, in addition to defining their limitations and applicability in the treatment and reuse of residual waters.

The specific objectives herein consist of:

• Assessing measurement requirements depending on treatment plant size, and distilling key parameters by taking into account the sampling frequency needs for establishing a set of specifications that incorporate regulatory parameters as well as additional parameters potentially worth measuring
• Defining an evaluation protocol for qualifying the sensors, in collaboration with the RMC Water Agency, according to the needs identified by sector actors located within the jurisdiction.