A spatial decision support system for optimally locating treatment plants for safe wastewater reuse: an application to Saudi Arabia

In this study, we developed a non-linear optimizing spatial decision support system that combines multi-criteria analysis with a geographical information system. We consider dedicated tertiary treatment for agricultural, industrial, and landscape uses by evaluating economic, social, and environmental objectives based on distances from opportunity costs and water quality standards. Saudi Arabia is used to illustrate decisions. Numerical simulations revealed that the budgeted number of plants is completely used, although tertiary treatment for all uses is seldom supported. Agricultural reuse is almost always suggested, whereas reuse in the industrial sector is not always suggested in provinces with current or planned industrial districts. Landscape reuse is always coupled with agricultural uses. The optimal wastewater treatment plants' location significantly improves welfare, although to a different extent for different sectors. The system achieves a satisfactory sectoral equity, in terms of the ability to meet the needs of, and reduce the impacts for industrial, agricultural, and landscape sectors except for social features in small cities. Sensitivity analyses revealed that the best location is robust with respect to the relative weights of economic, social and environmental features and the predicted future treatment efficiencies, but not robust with respect to water quality standards.