给水管网中微量污染物的迁移转化过程及其对生物膜群落结构的影响机制

The micro-pollutants are frequently detected in source water of our country today, which is one of the important issues that affect the drinking water quality. The micro-pollutants will go into the drinking water distribution systems (DWDSs), if they cannot be removed by water treatment processes. A series of physical, chemical, and microbial transformation processes of the micro-pollutants will probably occur in DWDSs. This will influence the safety of tap water quality. This project aims at the micro-pollutants and the risks of water quality which may be caused by the migration and transformation processes of the micro-pollutants, in the water of DWDSs. Three kinds of micro-pollutants, including sulfonamides, fluoroquinolones and chloramphenicols, are selected in this study. Firstly, the formation processes of different disinfection by-products during the reaction between micro-pollutants and chlorine/chloramine will be studied. Meanwhile, the effects of the migration and transformation processes of micro-pollutants on the genotoxicity of the water in DWDSs will be ascertained. Then, the micro-interfacial processes of the micro-pollutants on the corrosion products will also be studied to reveal the transformation mechanisms of micro-pollutants due to the synergic effects of corrosion products and microorganisms. Moreover, the influence mechanisms of the migration and transformation processes of micro-pollutants on the biofilm bacterial community structures and the microbial risks will also be studied according to the analysis of biofilm bacterial communities, antibiotic resistance genes, enzymatic activities and extracellular polymeric substances. Lastly, the synergic control method for micro-pollutants and microorganisms will be suggested, in order to reduce the genotoxicity and microbial risks of the water in DWDSs, and provide theory basis for the protection of water quality safety in DWDSs.

当前我国水源水中普遍存在的微量污染物是影响饮用水水质的重要问题之一。微量污染物如果不能被净水工艺有效去除进入管网，可能会发生一系列物理、化学和微生物的转化过程，影响管网末端龙头水水质安全。本项目针对管网水体存在微量污染物及其迁移转化可能导致的水质风险问题，以磺胺类、氟喹诺酮类和氯霉素类等微量污染物为主要研究对象，首先研究管网中微量污染物在氯/氯胺作用下持续生成不同消毒副产物的过程，明确该过程对管网水体遗传毒性的影响；然后研究不同微量污染物在腐蚀产物上的微观界面过程，揭示腐蚀产物和微生物协同转化微量污染物机制；另外通过微生物群落、抗药基因、酶活性及胞外多聚物等的表征，阐明微量污染物迁移转化对生物膜群落结构的影响机制及其可能导致的微生物风险。最后提出基于管网中微量污染物和微生物的协同控制措施，降低管网水体遗传毒性和微生物风险，为保障给水管网水质安全提供理论基础。

当前我国水源水中普遍存在的微量污染物是影响饮用水水质的重要问题之一。本项目针对管网水体存在微量污染物及其迁移转化可能导致的水质风险问题，以磺胺嘧啶和环丙沙星等抗生素为主要研究对象，首先研究了微量环丙沙星在加氯消毒和管网生物膜共同作用下的迁移转化过程，结果表明环丙沙星在氯化过程中未矿化，但其哌嗪环被破坏。一些没哌嗪环的氯化产物在管网中进一步被生物转化和生物矿化。氯和微生物对管网中环丙沙星氯化产物的转化起到协同作用，这使得管网出水遗传毒性明显降低，但是抗生素的生物转化会增加管网中抗药基因的风险。其次，在添加磺胺嘧啶和环丙沙星的管网中，铜绿假单胞菌、嗜肺军团菌、鸟分枝杆菌等条件致病菌明显增加。磺胺嘧啶和环丙沙星对这些条件致病菌的增加表现出更强的联合效应。这主要是因为磺胺嘧啶和环丙沙星的联合作用诱发了管网中更多的胞外多聚物EPS产生。蛋白质和二级结构β-折叠含量较高的EPS导致了更大的细菌聚集和粘附，从而形成更大的悬浮颗粒。因此，与颗粒物粘附的条件致病菌抗氯能力增强。第三，与原水管网相比，在磺胺嘧啶和环丙沙星的联合作用下的管网生物膜中，微生物表现出更高的酶活性，分泌更多的EPS。较高的EPS蛋白含量和二级结构β-折叠促进了细菌在管道表面的吸附并形成生物膜。因此，使用抗生素的管网生物膜中细菌总数增加，这也导致了ARGs的升高。最后，采用多相芬顿高级氧化-活性炭（Fenton-GAC）过滤和臭氧-活性炭（O3-GAC）过滤对管网进出水微量污染物和条件致病菌等进行控制。结果表明，Fenton-GAC对有机物中酪氨酸类蛋白和富里酸类物质的去除较多。O3-GAC对腐殖酸类化合物和色氨酸类蛋白质的去除较多。Fenton-GAC生物膜中与碳水化合物代谢相关的功能基因较高，导致其生物膜中EPS蛋白含量较高。因此，能从该生物膜中脱落进入到水中的微生物较少，而且包括条件致病菌在内的微生物比O3-GAC出水中更容易被氯灭活。然而，臭氧氧化比芬顿氧化灭活更多的微生物，这有助于控制O3-GAC出水中的微生物包括条件致病菌。