Assessment of Drinking Water Quality Using Water Quality Index: A Review

Nowadays, declining water quality is a significant concern for the world because of rapid population growth, agricultural and industrial activity enhancement, global warming, and climate change influencing hydrological cycles. Assessing water quality becomes necessary by using a suitable method to reduce the risk of geochemical contaminants. Water's physical and chemical properties are compared to a standard guideline to determine its quality. The water quality index (WQI) model is a commonly helpful technique for evaluating surface and groundwater quality. The model mainly employs aggregation techniques to diminish large amounts of data to a sole value. The WQI model has been used across the globe to assess ground and surface water using regional standards. The model has become popular for its ease of use and general structure. Typically, WQI models include five stages: (1) choosing water quality indicators, (2) generating sub-parameters for each variable, (3) calculating variable weighting numbers, (4) aggregating sub-parameters to finding the total WQI value, and (5) classification of WQI value to highlight the category of water quality. In addition, the model creates ambiguity when converting vast volumes of data into a single value. The study considered 2011-2021 blinded peer-reviewed articles and book chapters to assess WQI models and their application in evaluating drinking water quality. This study mainly concentrated on the comparison of WQI models and their applications. The study also focused on the selection of parameters and problems associated with the accuracy of the models.