Department of Animal Pathology, Faculty of Veterinary Sciences, University of Zaragoza, 50013 Zaragoza, Spain.
Department of Animal Pathology, Faculty of Veterinary Sciences, University of Zaragoza, 50013 Zaragoza, Spain.
Sci Total Environ. 2017 Feb 15;580:1007-1013. doi: 10.1016/j.scitotenv.2016.12.055. Epub 2016 Dec 16.
This paper collects the first large-sample-size study on the presence of Cryptosporidium oocysts and Giardia cysts in drinking water plants at the 20 most populated towns in Aragón (north-eastern Spain). Samples of influent raw water and effluent finished water were collected from each plant during different seasons and processed according to USEPA Method 1623. Cryptosporidium oocysts and Giardia cysts were detected in samples collected from 55% and 70% plants, respectively, with nine plants being positive for both protozoa and only four plants being negative over the study period. Both parasites were identified in the raw water throughout the year, with a lower frequency in autumn and a peak in winter, at a mean concentration of 67±38 oocysts per 100l and 125±241 cysts per 100l. The turbidity of raw water was not related to the presence or concentration of (oo)cysts, and the (oo)cyst removal efficiency was not related to the type of water treatment. One or both pathogens were identified in the finished water in 7 out of 11 plants with a conventional treatment process (coagulation, flocculation, sedimentation, filtration, and disinfection processes) compared to 4 out of 9 plants that did not apply one of the pre-chlorination treatment steps. Protozoa were detected in the finished water of positive plants at a mean concentration of 88±55 oocysts per 100l and 37±41 cysts per 100l, and most of them excluded propidium iodide so were considered potentially viable. The ubiquity of these parasites in the drinking water sources and the inefficiency of conventional water treatment in reducing/inactivating them may present a serious public health issue in this geographical area.
本文收集了在西班牙东北部阿拉贡自治区 20 个人口最多的城镇的饮用水厂中存在隐孢子虫卵囊和贾第鞭毛虫囊的首例大型样本研究。在不同季节，从每个工厂的原水进水和出水处理水采集样品，并按照美国环保署方法 1623 进行处理。在采集的样品中分别检测到 55%和 70%的工厂中存在隐孢子虫卵囊和贾第鞭毛虫囊，在研究期间，有 9 个工厂同时存在两种原生动物，而只有 4 个工厂为阴性。这两种寄生虫全年都在原水中被发现，秋季频率较低，冬季达到高峰，平均浓度分别为每 100l 有 67±38 个卵囊和 125±241 个囊。原水浊度与（oo）囊的存在或浓度无关，（oo）囊去除效率与水处理类型无关。在 11 个采用常规处理工艺（混凝、絮凝、沉淀、过滤和消毒工艺）的工厂中有 7 个工厂的出水发现了一种或两种病原体，而在没有采用预氯化处理步骤的 9 个工厂中有 4 个工厂发现了一种或两种病原体。在阳性植物的出水发现，平均浓度分别为每 100l 有 88±55 个卵囊和 37±41 个囊，大多数囊都排除了碘化丙啶，因此被认为具有潜在的生存能力。这些寄生虫在饮用水源中的普遍存在以及常规水处理在减少/灭活它们方面的低效可能会在该地区造成严重的公共卫生问题。
