Uncertainty on flow rate and temperature measurement for the detection of illicit flows in sewers

[Display omitted] •Simultaneous measures of flow rates and temperatures can detect illicit flows.•Uncertainty analysis to identify the most cost-effective gauges configuration.•Scheme B has a less expensive setup and better efficiency than schemes A and C.•A small illicit flow and/or the temperature difference imply higher uncertainty. Sewers often undergo crucial problems because of the combined effects of urbanization and extreme rainfall events. In addition, unexpected flows drained or discharged into the network, the so-called illicit flows, can overload the drainage systems. Their presence involves several environmental problems and increases both the flood risk, and the operational costs of the wastewater treatment plants.This study investigates the performances of combining flow rate and temperature measurements to estimate illicit flows in sewer systems. The goal is to identify an optimal configuration of flow meters and temperature sensors that can enhance reliability, accuracy, and money saving. Two applications have been used to validate the proposed framework. The first is a set of significant computational examples. The second is an application to an existing sewer network in Milano (Italy) within a research project funded by Regione Lombardia. The proposed method has proved to be suitable thanks to its simplicity, adaptability, and cost-effectiveness.