Treated wastewater reuse is a valuable water source in water scarcity conditions. If its technical feasibility is largely demonstrated, less attention is paid to the economic assessment. By applying an ex-post Cost-Benefit Analysis to Ouardanine irrigation district, in eastern Tunisia, the economic feasibility of wastewater treatment and reuse in irrigation was assessed. Data on costs and benefits were evaluated throughout the lifespan of the project and four scenarios – no treatment, treatment, treatment with reuse, and treatment with reuse without considering the environmental benefits – were considered. The results prove that: the project is economically profitable for all scenarios except the first; it is still profitable with an increase in costs or a decrease of benefits up to 30%; farmers are the main beneficiaries of the project which is financially not viable for both the treatment plant company and the public body charged of the distribution of water; the affordability of the treated wastewater price depends on the cropping pattern: with increased water pricing peach growers will still have substantial benefit while olive growers will reduce significantly their benefits.
