Evaluation of Different WQI Methods for Drinking Water Assessment with a Case Study of Groundwater from Vizianagaram District, AP, India

Application of Water Quality Index (WQI) to assess the water quality for drinking water suitability and intensity of contamination is in practice worldwide. Many WQI methods have been in use since their conceptualization, and some are country-specific or use-specific. A generalized and widely acceptable method that can project ground truths in non-dimensional numerical form to evaluate the water quality, especially for drinking uses, is lacking. Complexity and disagreement among different methods are adding to incongruence among the scientists. The concept and a simple calculation method of WQI are deliberated. Five different WQI methods using water chemistry results of Vizianagarm District are discussed. The WQI output obtained from these methods displays discrepancies in the proper projection of water quality. Some samples show similarities in WQI values obtained from two to four methods. However, the suitability status of water for drinking purposes could not be precisely ascertained from these indices. Since the water chemistry results and WQI values are incompatible, the output from these methods could be red herring. Few issues are identified among the studied methods which need improvisation. The use of ideal value in the weighted arithmetic index method and arbitration in assigning Weight for each parameter gives scope for speculation. Non-uniformity in the categorization of water and the suitability statuses of drinking water are discouraging factors. The WQI is an effective tool in screening the vast database for identifying and addressing the issues in water quality. Since drinking water standards and water supply are government-sponsored, an institutional intervention is required to standardize the WQI computation procedure. Such an initiative is necessary for the practical application of water quality data to contain water-borne diseases.