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 Nov 15;598:628-638. doi: 10.1016/j.scitotenv.2017.04.097. Epub 2017 Apr 25.
This study was designed to investigate the presence and removal efficiency of Cryptosporidium and Giardia in wastewater treatment plants at the 20 most populated towns in Aragón (north-eastern Spain). Samples of influent and effluent wastewater and dewatered sewage sludge were collected seasonally from 23 plants and processed according to USEPA Method 1623. All samples from raw and treated wastewater tested positive for Giardia, at an average concentration of 3247±2039cysts/l and 50±28cysts/l, respectively. Cryptosporidium was identified in most samples from both raw (85/92) and treated (78/92) wastewaters in a concentration significantly lower than Giardia, at both influent (96±105oocysts/l) and effluent samples (31±70oocysts/l) (P<0.001). The (oo)cyst counts peaked in summer in most plants. The removal efficiency was higher for Giardia (1.06-log to 2.34-log) than Cryptosporidium (0.35-log to 1.8-log). Overall, high removal efficiency values were found for Giardia after secondary treatment based on activated sludge, while tertiary treatment (microfiltration, chlorination and/or ultraviolet irradiation) was needed to achieve the greatest removal or inactivation of Cryptosporidium. Most samples of treated sludge were positive for Giardia (92/92) and Cryptosporidium (45/92), at an average concentration of 20-593cysts/g and 2-44oocyst/g, respectively. The molecular characterization of Cryptosporidium oocysts and Giardia cysts were attempted at the SSU rRNA/GP60 and bg/tpi loci, respectively. G. duodenalis sub-assemblage AII was identified in all plants, with a large proportion of samples (15/47) harboring mixed assemblages (AII+B). Nine Cryptosporidium species and six subtypes were identified, with C. parvum IIaA15G2R1 being the most prevalent. The presence of significant numbers of (oo)cysts in samples of final effluents and treated sludge reveals the limited efficacy of conventional treatments in removing (oo)cysts and highlights the potential environmental impact and public health risks associated with disposal and reclamation of wastewater.
本研究旨在调查西班牙东北部阿拉贡自治区 20 个人口最多的城镇的污水处理厂中隐孢子虫和贾第鞭毛虫的存在及其去除效率。从 23 个工厂中采集了季节性进水和出水废水以及脱水污水污泥样本，并按照美国环保署 1623 号方法进行处理。所有原水和处理后废水的样本均检测出贾第鞭毛虫，平均浓度分别为 3247±2039 个囊孢/升和 50±28 个囊孢/升。在原水（85/92）和处理水（78/92）的大多数样本中均鉴定出隐孢子虫，浓度明显低于贾第鞭毛虫，进水样本（96±105 个孢囊/升）和出水样本（31±70 个孢囊/升）（P<0.001）。大多数工厂的（oo）囊泡计数在夏季达到峰值。贾第鞭毛虫的去除效率（1.06-2.34 对数）高于隐孢子虫（0.35-1.8 对数）。总体而言，基于活性污泥的二级处理后，发现贾第鞭毛虫的去除效率较高，而需要进行三级处理（微滤、氯化和/或紫外线照射）以实现对隐孢子虫的最大去除或灭活。大多数处理后的污泥样本均检测出贾第鞭毛虫（92/92）和隐孢子虫（45/92），平均浓度分别为 20-593 个囊孢/克和 2-44 个孢囊/克。在 SSU rRNA/GP60 和 bg/tpi 基因座分别尝试了隐孢子虫孢囊和贾第鞭毛虫囊的分子特征。在所有工厂中均鉴定出 G. duodenalis 亚群 AII，其中有很大一部分样本（15/47）携带混合亚群（AII+B）。鉴定出 9 种隐孢子虫和 6 种亚型，其中 C. parvum IIaA15G2R1 最为常见。最终出水和处理后的污泥样本中存在大量（oo）囊泡，这表明传统处理方法去除（oo）囊泡的效果有限，并强调了与废水处理和再利用相关的潜在环境影响和公共卫生风险。
