USING THE FUZZY HIERARCHY PROCESS FOR SELECTING WASTEWATER FACILITIES AT PREFECTURE LEVEL

Although decision makers involved in environmental management issues usually agree on the necessity of interventions, conflicts emerge when interventions are specified and touch upon citizens’ reality in their local societies. In this context, a rationalization of the decision-making process is clearly needed in order to deal with conflicting objectives and divergent interests. We propose a multicriteria approach based on the Analytic Hierarchy Process (AHP) for selecting wastewater facilities at prefecture level. On the one hand we take for granted that there is consensus on the structure of hierarchy, i.e. the treatment processes and the criteria used for their evaluation. Evaluation of alternative treatment processes is performed with respect to the number, size, treatment method, and facilities location, and the evaluation criteria are based on the land planning, the environmental and techno-economic considerations, such as construction and operating costs. On the other hand, we propose the fuzzy extension of AHP for dealing with the vagueness of decision makers’ judgments. Since decision makers are not normally able to provide a quantitative evaluation of the alternatives but only a qualitative one, the pairwise comparisons are expressed in fuzzy terms. We use this method in a case study, we discuss its application in real world situations, and we conclude that this approach is a viable evaluation device and a good communication tool between analysts and decision-makers.