Water Quality Indices - Methods for Evaluating the Quality of Drinking Water

Abstract

Water quality is assessed through the biological, physical and chemical parameters. The limits of these parameters that are harmful to human health have been established at national or international level (WHO, EPA, MECC) by various laws, regulations, normative. An efficient and simplified to express the quality of water for consumption is given by the water quality index. It reflects the quality of water in a single value by comparing data obtained from the investigation of a number of physico-chemical and bacteriological parameters with existing limits. This number is placed on a relative scale to justify the quality of water in categories ranging from very poor to excellent. In this study are discussed various water quality indices used to assess the quality of drinking water (surface water). National and international agencies involved in assessing water quality and pollution control defines different quality criteria used for drinking water which is why there are many water quality specific indices for each region or area. In this context, it will present a comparative study of the most important quality indices used to assess water quality worldwide.

Various methods for calculating the water quality index

“… It cannot provide definitive information regarding changes in toxics concentrations, habitat or biology;  It cannot evaluate all the toxic elements for health (bacteria, metal, toxics) [21,22].…”

“… This index may not provide enough information about the real situation of the water quality;  This index does not include all the parameters which can describe the quality of a body of water [21,22];  This index only quantifies the direct effect of pollution on a body of water. Index (CCME-WQI) utilizes the following parameters for determining the water quality in a stream: temperature, conductivity, color, turbidity, dissolved oxygen (OD), pH, alkalinity, Ca, Na, Mg, K, SO4, Cl-, F-, Dissolved Organic Carbon, P, Nitrates, Nitritis, N, SiO 2 , Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Se, Sr, V, Zn [27].…”

“…. Disadvantages: It does not utilize a complex scale of water quality parameters;  Some of the data get lost while being manipulated[21,22]. is used to describe the quality of surface waters bodies from Oregon, as well as from other geographical areas.…”

“…The corresponding values of water quality in conformity with CCME-WQI Index[22,29,30] All the variables have the same importance in the determination of the index.  It cannot be mixed up with other indicators or with other biological data.…”

“… The water quality gets described only partially.  F 1 does not work appropriately when too few variables are taken into consideration[21,22].…”