氯消毒是目前应用最广泛的一种消毒方法。但是研究者发现有些细菌对氯的耐受性很高，这些“耐氯菌”对饮用水微生物学安全构成了威胁。本研究以实际供水管网中分离出的多株耐氯性细菌为研究对象，考察了四种消毒方法对其灭活特性，给出了有效灭活这几株耐氯菌的消毒剂有效浓度等参数，并对其中一株条件致病菌——分支杆菌的耐氯机理进行了探索。研究的主要结论如下：从实际管网中分离出七株耐氯菌，经鉴定为类龟分支杆菌、血红鞘胺醇单胞菌和甲基杆菌。这些细菌均具有较强的耐氯性，其中一株类龟分枝杆菌耐氯性最强，使用自由氯99.9%灭活时需要的CT值为120mg/L•min，达到金黄色葡萄球菌的260倍。不同含氯消毒剂在相同的有效氯投加量下，24小时内消毒效果的排序为：二氧化氯> 顺序氯化> 一氯胺> 游离氯。3.0mg/L一氯胺、1.0mg/L二氧化氯（以Cl2计）可以有效控制上述耐氯菌的生长。在本消毒试验中，细菌会影响消毒剂衰减，并生成有机氯胺。当控制初始菌浓度为105CFU/ml左右时，菌体对消毒剂的消耗量很小可以忽略。消毒剂种类对于耗氯量和有机氯胺生成量具有显著的影响：游离氯衰减迅速，并生成较多的有机氯胺；一氯胺衰减缓慢并且与细菌反应生成少量有机氯胺，二氧化氯由于强氧化性而衰减较快，但不与菌液反应生成有机氯胺；短时游离氯后转氯胺的顺序氯化工艺中余氯衰减速率和有机氯胺的生成量均介于游离氯和一氯胺之间。消毒剂的投加量和有机氯胺的生成之间具有线性关系。在投加等量消毒剂的条件下，水中有机物的存在对于细菌确实起到了保护的作用。通过对分支杆菌脂肪酸组成和细胞膜功能的研究发现，分支杆菌特殊的细胞膜结构是造成其耐氯性较强的原因之一。分支杆菌细胞膜中饱和脂肪酸占95.7%，是耐氯性较差的金黄色葡萄球菌的4.98倍。消毒30分钟后分支杆菌细胞膜功能受损的细菌占总量的18.62%，而金黄色葡萄球菌为87.59%，说明分支杆菌细胞膜更耐受游离氯的破坏。通过对比实验，该菌消耗余氯和生成有机氯胺的性能未见特异情况，因此消耗余氯生成有机氯胺不是该菌耐氯的主要原因。
Chlorine disinfection processes are most widely used in water treatment plants in China. However chlorine-resistant bacteria have been detected resently in the distribution systems, which could endanger drinking water microbial safety. To improve the biological stability of the distribution system, this research studied the disinfection characteristics of several strains of chlorine-resistant bacteria isolated from real distribution systems, using free chlorine, monochloramine, chlorine dioxide and sequencial chlorination process, respectively, for inactivation. Moreover, the research also has explored the mechanism of disinfection of the bacteria. These strains of chlorine-reisitant bacteria were identified as Mycobacterium mucogenicum, Sphingomonas sanguinis and Methylobacterium. They all showed high resistance to chlorine, especially for M. mucogenicum. The CT value of 99.9% inactivation for M. mucogenicum by free chlorine was 120mg/L•min which was 260 times more than that of Staphylococcus aureus. For Mycobacteria, the effects of each disinfectant are: chlorine dioxide> potassium monopersulfate> monochloramine> free chlorine under the same consentration.In disinfection experiment, the bacteria cells were the main reason of disinfectant decay and the generation of organic chloramines. No organic chloramines formation was detected with the cell concentration equal to or less than 105 CFU/mL. Four disinfectants had apparently different decay characteristics and organic chloramines formation behaviors. Free chlorine decayed fastest and formed the highest concentration of organic chloramines. Monochloramine decayed very slowly and formed limited organic chloramines. Chlorine dioxide did not form organic chloramines although it exhibited a similar decay behavior as free chlorine. Sequential chlorination was a combination of free chlorination and monochloramination.The formation of organic chloramines was proportional to the initial concentration of the disinfectant. Meanwhile the presence of organic matter played a protective role for the bacteria in disinfection.Different composition of cell membrane might endow M. mucogenicum with high chlorine resistance. Lipid analysis of the cell construction revealed that 95.7% of cell membrane lipid of M. mucogenicum was composed of saturated long chain fatty acids which was 4.98 times of that of S. aureus. From the Flow cytometry experiment result, 18.62% of M. mucogenicum showed cell membrane structure damage while the percentage of S. aureus was 87.59% under the same experimental conditions.The analysis of chlorine consumption on two bacteria with different chlorine resistance indicated that higher amount of chlorine consumption was not the direct reason of the chlorine resistance of mycobacteria.
