A social choice-based methodology for treated wastewater reuse in urban and suburban areas

Reusing treated wastewater for supplying water demands such as landscape and agricultural irrigation in urban and suburban areas has become a major water supply approach especially in regions struggling with water shortage. Due to limited available treated wastewater to satisfy all water demands, conflicts may arise in allocating treated wastewater to water users. Since there is usually more than one decision maker and more than one criterion to measure the impact of each water allocation scenario, effective tools are needed to combine individual preferences to reach a collective decision. In this paper, a new social choice (SC) method, which can consider some indifference thresholds for decision makers, is proposed for evaluating and ranking treated wastewater and urban runoff allocation scenarios to water users in urban and suburban areas. Some SC methods, namely plurality voting, Borda count, pairwise comparisons, Hare system, dictatorship, and approval voting, are applied for comparing and evaluating the results. Different scenarios are proposed for allocating treated wastewater and urban runoff to landscape irrigation, agricultural lands as well as artificial recharge of aquifer in the Tehran metropolitan Area, Iran. The main stakeholders rank the proposed scenarios based on their utilities using two different approaches. The proposed method suggests ranking of the scenarios based on the stakeholders' utilities and considering the scores they assigned to each scenario. Comparing the results of the proposed method with those of six different SC methods shows that the obtained ranks are mostly in compliance with the social welfare.