ICID paper : Clermont-Ferrand and Cannes case studies' cost-benefits analysis

Abstract

Unlike many structuring projects, treated wastewater reuse projects are rarely subjected to economic analysis. And when they are, social and environmental benefits and costs are often not accounted for or are not properly quantified. Here we show that the 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 due to the system's complexity rather than its methodological limits. Indeed, the operator must be able to understand, formalize and imagine constraints and risks associated to 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 with 2 case studies: Clermont-Ferrand where treated wastewater is reused by a collective irrigation network; and Cannes where surface and groundwater recharge could enable indirect reuse for multiple purposes including indirect potable water production. These 2 French case studies highlight how economic analysis, dealing with uncertainties, can support decision making.