A comparative study of water quality using two quality indices and a risk index in a drinking water distribution network

This study compares the Canadian Council Water Quality Index (CCME WQI) and the Arithmetic Water Quality Index (WAWQI) methodologies for determining the quality of water in the city of Azogues (Ecuador). Additionally, a drinking water quality risk index (IRCA) was determined to evaluate the degree of risk of disease occurrence related to water consumption. The data generated came from the analyses of twelve physicochemical parameters (pH, turbidity, colour, total dissolved solids, electrical conductivity, total hardness, alkalinity, nitrates, phosphates, sulfates, chlorides, residual chlorine) from 172 samples of water over six months. The calculated average value of CCME WQI (97.59 ± 1.08) indicates that 100% of the drinking system was of ‘excellent’ quality. The WAWQI average value was calculated to be 26.36 ± 1.13 indicating that 16.67% of the distribution system was of ‘excellent’ quality and 83.33% of the distribution water was of ‘good’ quality. The IRCA calculated in all the distribution zones is between 0 and 5% and therefore, the distributed water is considered suitable for human consumption and is rated at the no-risk level. Furthermore, WAWQI is influenced by parameters with low maximum allowed concentration (for example, turbidity value 1 NTU in the Ecuadorian standard was used instead of 5 NTU recommended by the WHO); conversely, CCME-WQI is influenced by parameters with a high maximum allowed concentration (no parameter exceeded the norm in this study). The IRCA is a support instrument to guarantee that the water supplied by the provider companies complies with the characteristics established for drinking water.

本研究对比评估了加拿大委员会水质指数（Canadian Council Water Quality Index, CCME WQI）与算术水质指数（Arithmetic Water Quality Index, WAWQI）两种水体质量评价方法，以分析厄瓜多尔阿索格斯市的水质状况。此外，本研究还通过计算饮用水水质风险指数（IRCA），评估了与饮水相关的疾病发生风险程度。本研究的数据来源于6个月内采集的172份水样的12项理化指标检测结果，具体包括pH值、浊度、色度、总溶解固体、电导率、总硬度、碱度、硝酸盐、磷酸盐、硫酸盐、氯化物及余氯。经计算，CCME WQI的平均值为97.59±1.08，表明该城市100%的饮用水供水系统水质等级为“优秀”。WAWQI的平均值为26.36±1.13，其中16.67%的供水管网系统水质达到“优秀”等级，剩余83.33%的供水水质为“良好”等级。所有供水区域的IRCA值介于0至5%之间，因此本次研究中的供水可安全供人饮用，属于无风险等级。进一步分析表明，WAWQI受最大允许浓度较低的指标影响更为显著——例如，本研究采用厄瓜多尔标准规定的1 NTU浊度限值，而非世界卫生组织推荐的5 NTU限值；与之相反，CCME WQI受最大允许浓度较高的指标影响，本研究中所有指标均未超出规范限值。此外，IRCA可作为保障供水企业供应的饮用水符合既定水质标准的辅助工具。