Multi-criteria methodology for selection of wastewater treatment systems with economic, social, technical and environmental aspects

The design, implementation and use of wastewater treatment systems (WTS) are fundamental to mitigate hydrological and environmental problems, and to improve population health. Furthermore, the significant advances in treatment systems technology offer, nowadays, several alternatives and provide many combinations of WTS which must be correctly evaluated and constitute a decision problem for public and private investors and decision makers. Thus, this article presents a multi-criteria methodology based on six steps for the evaluation of WTS considering relevant economic, social, technical and environmental criteria. Particularly, forty-eight main criteria were identified and ranked considering their importance based on the previous literature. This methodology was applied in a Brazilian sanitation company in a specific treatment area of approximately five thousand inhabitants and with recurrent environmental problems, such as the contamination and low efficiency of wastewater treatment. Twenty available alternatives were considered and twelve criteria were selected for this application. The AHP and ELECTRE II methods were combined to weight the different criteria and to rank the most suitable WTS. This methodology can be extended and applied in different scenarios to improve the decision-making process.