Application of Fuzzy Analytical Hierarchy Process in Determining the Optimum Alternative of Brackish water Desalination

In this research a fuzzy decision making model was presented to assess and rank various water desalination methods and ultimately select the best alternative. The desalination alternatives which were investigated included Reverse Osmosis، Electrodialysis، Multi-Stage Flash Distillation، Multi-Effect Distillation، Vapor Compression and Ion Exchange. The model was carried out in three steps: problem definition، fuzzy computations and ranking of alternatives. The hierarchy structure used for problem definition included 5 levels of: goal، main criteria، sub-criteria، factors، and desalination alternatives. The criteria، sub-criteria and factors and the relative importance of each were determined based on the experts'' opinions and the literature results. In the next step، by using Chang''s extent analysis، various desalination alternatives were evaluated on the basis of the selected criteria، sub-criteria and factors. For assessment of accuracy and its practical application، the model was used in a case study concerning quality management of the brackish water from a number of wells located in the City of Torbat-e-Heydaryieh. The results of the research indicated that the Electrodialysis process، with the final weight of 0. 255، was the best method of desalination for the investigated wells. The sensitivity analysis also showed that the fuzzy model has a low degree of sensitivity in regard to the changes in criteria weights، meaning that the results are adequately reliable. The results furthermore pointed out that the fuzzy analytical hierarchy process can be used as an efficient tool for systematic decision making in the area of qualitative water resource management.