Alumnus, Department of Civil and Environmental Engineering, National University of Singapore, Singapore; School of Environment and Society, Tokyo Institute of Technology, Tokyo, Japan.
Department of Civil Engineering, Malaviya National Institute of Technology, Jaipur, India E-mail:
Water Sci Technol. 2022 Jul;86(2):261-291. doi: 10.2166/wst.2022.206.
Though chlorine is a cost-effective disinfectant for water and wastewaters, the bacteria surviving after chlorination pose serious public health and environmental problems. This review critically assesses the mechanism of chlorine disinfection as described by various researchers; factors affecting chlorination efficacy; and the re-growth potential of microbial contaminations in treated wastewater post chlorination to arrive at meaningful doses for ensuring health safety. Literature analysis shows procedural inconsistencies in the assessment of chlorine tolerant bacteria, making it extremely difficult to compare the tolerance characteristics of different reported tolerant bacteria. A comparison of logarithmic reduction after chlorination and the concentration-time values for prominent pathogens led to the generation of a standard protocol for the assessment of chlorine tolerance. The factors that need to be critically monitored include applied chlorine doses, contact time, determination of chlorine demands of the medium, and the consideration of bacterial counts immediately after chlorination and in post chlorinated samples (regrowth). The protocol devised here appropriately assesses the chlorine-tolerant bacteria and urges the scientific community to report the regrowth characteristics as well. This would increase the confidence in data interpretation that can provide a better understanding of chlorine tolerance in bacteria and aid in formulating strategies for effective chlorination.
尽管氯是一种用于水和废水消毒的高性价比消毒剂，但经过氯化消毒后存活的细菌会对公共健康和环境造成严重问题。本综述批判性地评估了不同研究人员所描述的氯消毒机制；影响氯化效果的因素；以及处理后的废水中微生物污染物在氯化后的再生潜力，以确定确保健康安全的有意义的剂量。文献分析表明，对耐氯细菌的评估存在程序不一致性，这使得很难比较不同报道的耐氯细菌的耐受特性。经过氯化后的对数减少与主要病原体的浓度-时间值的比较，为评估氯耐受性生成了一个标准协议。需要严格监测的因素包括应用的氯剂量、接触时间、确定介质的氯需求，以及在氯化后和氯化后样品（再生）中立即考虑细菌计数。这里设计的方案可以适当地评估耐氯细菌，并促使科学界也报告再生特性。这将提高对数据解释的信心，从而更好地了解细菌的氯耐受性，并有助于制定有效的氯化策略。
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