Water quality index and grade.

This study assessed the physical, chemical, and microbiological quality with emphasis on risk score, source apportionment, geochemistry, feacal coliforms and water quality index of drinking water from selected water sources. A cross-sectional study was conducted in six villages in Mbarara city, south-western Uganda. Each selected source was inspected using a WHO-adopted sanitary inspection questionnaire. Each source’s risk score was calculated. Thirty-seven samples were taken from one borehole, nine open dug wells, four rain harvest tanks, and twenty-three taps. The values for apparent color and phosphate were higher than the permissible level as set by the World Health Organization and Ugandan standards (US EAS 12). The isolated organisms were Klebsiella spp. (8.11%), Citrobacter divergens (62.16%), Citrobacter fluendii (2.7%), E. coli (35.14%), Enterobacter aerogenes (8.11%), Enterobacter agglomerus (5.4%), Proteus spp. (2.7%), Enterobacter cloacae (13.5%), and Proteus mirabilis (2.7%). Twelve water sources (32.4%) had water that was unfit for human consumption that was unfit for human consumption (Grade E), Five sources (13.5%) had water that had a very poor index (Grade D), nine (24.3%) had water of poor index (Grade C), eight (21.6%) had water of good water index (Grade B), and only three (8.1%) had water of excellent water quality index (Grade A). The piper trilinear revealed that the dominant water type of the area were Mgso4 and Caso4 type. Gibbs plot represents precipitation dominance. PCA for source apportionment showed that well, tap and borehole water account for the highest variations in the quality of drinking water. These results suggest that drinking water from sources in Mbarara city is not suitable for direct human consumption without treatment. We recommend necessary improvements in water treatment, distribution, and maintenance of all the available water sources in Mbarara City, South Western Uganda.本研究针对选定饮用水水源的物理、化学与微生物学质量展开评估，重点关注风险评分、源解析（source apportionment）、地球化学特征、粪大肠菌群（faecal coliforms）以及水质指数（water quality index）。本研究于乌干达西南部姆巴拉拉市的六个村庄开展横断面研究，所有选定水源均采用世界卫生组织（WHO）推荐的卫生检查问卷进行核查，并计算各水源的风险评分。本次研究共从1口钻井、9口露天挖掘井、4座雨水收集池以及23个供水龙头处采集了37份饮用水样本。研究发现，水样的表观色度与磷酸盐浓度均超出世界卫生组织（WHO）及乌干达国家标准（US EAS 12）规定的限值。本次分离得到的菌株包括：克雷伯菌属（Klebsiella spp.，8.11%）、异型柠檬酸杆菌（Citrobacter divergens，62.16%）、Citrobacter fluendii（2.7%）、大肠杆菌（E. coli，35.14%）、产气肠杆菌（Enterobacter aerogenes，8.11%）、聚团肠杆菌（Enterobacter agglomerus，5.4%）、变形杆菌属（Proteus spp.，2.7%）、阴沟肠杆菌（Enterobacter cloacae，13.5%）以及奇异变形杆菌（Proteus mirabilis，2.7%）。水质分级结果显示：12处水源（占比32.4%）的水质不适宜人类直接饮用，属于E级；5处水源（占比13.5%）的水质指数极差，属于D级；9处水源（占比24.3%）的水质指数较差，属于C级；8处水源（占比21.6%）的水质指数良好，属于B级；仅3处水源（占比8.1%）的水质指数优秀，属于A级。派珀三线图（Piper trilinear diagram）分析结果显示，该区域的优势水型为硫酸镁型与硫酸钙型。吉布斯图（Gibbs plot）表明该区域水体受降水主导。用于源解析的主成分分析（Principal Component Analysis，PCA）结果表明，钻井水、露天井及供水龙头水是导致该区域饮用水水质产生最大变异的来源。上述研究结果表明，乌干达西南部姆巴拉拉市各水源产出的饮用水若未经处理，均不适宜人类直接饮用。据此，本研究建议对乌干达西南部姆巴拉拉市所有现有饮用水水源的处理、配送及维护流程开展必要改进。