Incomplete interval type-2 fuzzy preference relations based on a multi-criteria group decision-making model for the evaluation of wastewater treatment technologies

Water pollution is a problem globally, where untreated human and industrial waste is directly discharged into water bodies. Choosing a suitable wastewater treatment technology (WTT) is vital. We develop a novel multi-criteria group decision-making framework to evaluate four WTTs (Anaerobic Anoxic Oxic, Triple Oxidation Ditch, Anaerobic Single Oxidation Ditch, Sequencing Batch Reactor Activated Sludge). It consists of four phases: (1) collecting incomplete linguistic pairwise comparisons; (2) characterizing this matrix by incomplete interval type-2 fuzzy sets; (3) repairing incomplete information to reach pre-defined consistency/consensus levels; and (4) calculating the arithmetic ranking values. We demonstrate the feasibility and superiority of the model, inviting experts to evaluate the WTTs against eight criteria. Finally, we conduct a series of comparative analyses and a sensitivity analysis. The model gives a thorough measure of WTTs across multiple criteria. The suitable WIT is different for small or medium towns, and big cities in developing or developed countries. (C) 2019 Elsevier Ltd. All rights reserved.