Identification of water reuse potential in Metropolitan Regions using the Analytic Hierarchy Process

The use of reclaimed water as an alternative non-potable source is an increasing practice worldwide, especially in areas where water scarcity is becoming more severe. As with other environmental applications, reuse planning commonly faces a problem related to the selection of the best scheme to be adopted. To address this issue, this paper proposes, based on a Multi-Criteria Decision Analysis (MCDA) approach, the development of the Water Reuse Potential (WRP) index to indicate the potential for developing industrial and agricultural non-potable water reuse schemes. The study area selected was the Metropolitan Region of São Paulo (MRSP) in Brazil, a region that can be used as a model for most urban areas in the world. The model was built using the Analytic Hierarchy Process (AHP) applying technical, environmental, and socioeconomic criteria. Sensitivity analysis was carried out to verify the influence of criteria weights on the results. Geographic Information System (GIS) was used for data extraction and spatial allocation of the results. The study identified São Paulo (WRP ​= ​0.813), Suzano (0.363), Barueri (0.293), Mogi das Cruzes (0.282) and Guarulhos (0.252) as the municipalities with greater WRP. Considering that water reuse is not a common practice in many countries and that non-potable reuse may be a fundamental step for water sources diversification, the approach developed can be used as a planning tool to assess and classify any region according to its reuse potential, providing decision makers and planners with simple-understanding and versatile elements for prioritizing investments in further studies.