A Comparative Approach to a Series of Physico-Chemical Quality Indices Used in Assessing Water Quality in the Lower Danube

Abstract

Water quality indices are suitable tools used for assessing water quality because of their capacity to reduce a large number of water quality indicators into one value which defines the water quality class. In this study, Water Quality Index (WQI), Water Pollution Index (WPI) and Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) were applied in order to evaluate the seasonal and spatial variation of the water quality in the Romanian Lower Danube sector. Fourteen physico-chemical parameters, i.e., pH, DO, BOD5, COD, N-NH4+, N-NO3−, N-NO2−, N-total, P-total, SO42−, Cl−, Fe-total, Zn2+ and Cr-total, were monitored along the Danube course (on a distance of about 120 km), during the four seasons between the autumn of 2018 and the summer of 2019 in order to calculate the three indices mentioned above. Indices results showed that the water analysed was ranked into different water quality classes, although the same dataset was used. These differences were due to the contribution of each parameter taken into account in the calculation formula. Thus, the WQI scores were mostly influenced by those parameters whose maximum allowable concentration was low (e.g., heavy metals, N-NO2−), while the WPI and CCME-WQI scores were influenced by those parameters which exceeded the maximum allowable concentration (BOD5, DO, COD, N-NO3−, N-NO2−). Based on the WQI results, the water was ranked into quality classes II and III. WPI and CCME-WQI assessed water only in quality class II, with one exception in the case of CCME-WQI when water was ranked into quality class III. The temporal assessment identified the seasons in which the water quality was lower, namely summer and autumn. The variation of the indices values between the sampling stations demonstrates the existence of pollution sources in the study area. Moreover, the indices results illustrated the contribution of the main tributaries (Rivers Siret and Prut) to the Danube River water quality. The appropriate applicability of the three indices was also discussed in this study.

Physicochemical Quality of Water from Chuho Springs, Kisoro District, Uganda

“…The WQI is used to interpret complex analytical data obtained from water analysis into a water quality information that is easily understood by decision makers and the general public [62]. The WQI expresses the overall quality of any water sample under investigation so that the water status can be known (for instance fit for drinking or unfit).…”

“…The WQI expresses the overall quality of any water sample under investigation so that the water status can be known (for instance fit for drinking or unfit). The CCME-WQI value enables the water to be ranked as poor (0-44), marginal (45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63)(64), fair (65-79), good (80-89), very good (90-94) and excellent (95-100) [33]. The WQI index obtained in this study (Table 2) shows that the water quality of springs A, B and C are marginal while water of springs D and tap water are fair and good, respectively.…”

A Forecasting and Prediction Methodology for Improving the Blue Economy Resilience to Climate Change in the Romanian Lower Danube Euroregion

“…They observed reductions in the nutrient loads in the water of the Danube River; however, the river is still at risk of degradation due to organic pollution. Other studies calculated the Water Quality Index (WQI), which integrates different physicochemical parameters into the formula and synthetizes the data into a single number to highlight the ecological status of the water body in Chiciu, Romania [65] near Galat , i, Romania [66], between the sector of Brăila and Tulcea within Romania [67]. All authors highlighted in their studies a general good water quality status in the Danube River.…”

Predictive Innovative Methods for Aquatic Heavy Metals Pollution Based on Bioindicators in Support of Blue Economy in the Danube River Basin

“…For instance, water quality index (WQI), Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) and heavy metal pollution index (HPI) use in their specific equations more than 1 variable. In addition to Fe, Zn and Cr, WQI takes into consideration other water quality parameters such as phosphorous, nitrates, chlorides, alkalinity, total dissolved solids, total hardness, pH, electrical conductivity, dissolved oxygen, turbidity, biological oxygen demand, chemical oxygen demand [51,52]. In addition, HPI takes into consideration the concentrations of chromium, cobalt, nickel, copper, zinc, cadmium, mercury, arsenic, manganese and iron [52].…”