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Unlike many structuring projects, treated wastewater reuse projects are rarely subject to economic analysis. When they are analyzed social and environmental benefits are often not properly quantified. Here we show that widely used cost-benefit analysis method showing a project's interest from the whole collectivity point of view can be adapted to treated wastewater reuse projects. The remaining evaluation difficulties are more related to the system complexity rather than methodological limits. Indeed, the operator must be able to understand, formalize and imagine constraints and risks associated with different domains like urbanism, agriculture, climate, hydrology and trade. Remaining uncertainties on key parameter values can however be properly considered through scenarios and/or stochastic approaches. We illustrate the implementation of this methodological approach through a Clermont-Ferrand case study where treated wastewater is reused by a collective irrigation network. This case study highlights how economic analysis, dealing with uncertainties, can support decision makers.
