Murray Anna L, Kumpel Emily, Peletz Rachel, Khush Ranjiv S, Lantagne Daniele S
Department of Civil and Environmental Engineering, Tufts University, 200 College Avenue, Medford, MA 02155, USA E-mail:
The Aquaya Institute, Riara Corporate Suites, Suite #203, Riara Road, Kilimani Estate, Nairobi, Kenya.
J Water Health. 2018 Feb;16(1):70-77. doi: 10.2166/wh.2017.077.
In microbiological water quality testing, sample dechlorination with sodium thiosulfate is recommended to ensure that results accurately reflect the water quality at sample collection. Nevertheless, monitoring institutions in low-resource settings do not always dechlorinate samples, and there is limited research describing how this practice impacts drinking water quality results. The effect of dechlorination on indicator bacteria counts was evaluated by spiking laboratory water with five Escherichia coli (E. coli) concentrations (10-10 CFU/100 mL), chlorinating at six doses (0-0.6 mg/L), holding samples with and without sodium thiosulfate for 5-7 hours, and enumerating E. coli by membrane filtration with m-lauryl sulfate media. Additionally, sub-Saharan African water suppliers enumerated thermotolerant coliform by membrane filtration in paired chlorinated water samples collected with and without sodium thiosulfate. Across all E. coli and chlorine doses in the laboratory, and all field tests, samples held without sodium thiosulfate had lower bacteria counts (p < 0.001). Additionally, chlorinated water supply samples held without sodium thiosulfate had an 87.5% false negative rate. Results indicate the importance of dechlorinating microbiological water quality samples, discarding data from chlorinated samples collected without dechlorination, and reinforcing dechlorination recommendations in resource-limited environments to improve water safety management.
在微生物水质检测中，建议使用硫代硫酸钠对样品进行脱氯处理，以确保检测结果能准确反映采样时的水质情况。然而，资源匮乏地区的监测机构并非总是对样品进行脱氯处理，而且关于这种做法如何影响饮用水质量检测结果的研究也很有限。通过向实验室用水中加入五种不同浓度（10-10 CFU/100 mL）的大肠杆菌（E. coli），以六种剂量（0-0.6 mg/L）进行氯化处理，对加入和未加入硫代硫酸钠的样品分别保存5-7小时，并用含月桂基硫酸盐的培养基通过膜过滤法对大肠杆菌进行计数，从而评估脱氯对指示菌计数的影响。此外，撒哈拉以南非洲地区的供水商对采集的成对氯化水样（一份含硫代硫酸钠，一份不含）通过膜过滤法对耐热大肠菌群进行计数。在实验室中所有大肠杆菌浓度和氯剂量条件下，以及所有现场测试中，未添加硫代硫酸钠的样品中细菌计数更低（p < 0.001）。此外，未添加硫代硫酸钠的氯化供水水样假阴性率达87.5%。结果表明对微生物水质样品进行脱氯处理的重要性，舍弃未脱氯采集的氯化样品数据，并在资源有限的环境中强化脱氯建议，以改善水安全管理。
