water Review Modification of the Water Quality Index (WQI) Process for Simple Calculation Using the Multi-Criteria Decision-Making (MCDM) Method: A Review Naseem Akhtar 1 , Muhammad Izzuddin Syakir Ishak 1,2,*, Mardiana Idayu Ahmad 1 , Khalid Umar 3 , Mohamad Shaiful Md Yusuff 1, Mohd Talha Anees 4, Abdul Qadir 5 and Yazan Khalaf Ali Almanasir 1 1 School of Industrial Technology, Division of Environmental Technology, Universiti Sains Malaysia, Gelugor 11800, Pulau Pinang, Malaysia;
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[email protected] (Y.K.A.A.) 2 Centre for Global Sustainability Studies, Universiti Sains Malaysia, Gelugor 11800, Pulau Pinang, Malaysia 3 School of Chemical Sciences, Universiti Sains Malaysia, Gelugor 11800, Pulau Pinang, Malaysia;
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[email protected] Abstract: Human activities continue to affect our water quality; it remains a major problem world- wide (particularly concerning freshwater and human consumption). A critical water quality index Citation: Akhtar, N.; Ishak, M.I.S.; (WQI) method has been used to determine the overall water quality status of surface water and Ahmad, M.I.; Umar, K.; Md Yusuff, groundwater systems globally since the 1960s. WQI follows four steps: parameter selection, sub- M.S.; Anees, M.T.; Qadir, A.; Ali indices, establishing weights, and final index aggregation, which are addressed in this review.