管网内含氮和碘代消毒副产物的降解性能及其QSAR研究

Disinfection of drinking water is a vital process to control microbial risks in water. However, the addition of disinfectant can trigger formation of a series of carcinogenic disinfection byproducts (DBPs), which are either regulated already or of emerging concerns. Recently, two groups of emerging DBPs, iodinated DBPs (I-DBPs) and nitrogen-containing DBPs (N-DBPs), have attracted considerable attention from researchers with regard to their highly geno- and cyto- toxic implications. Therefore, their occurrence, formation, control, and monitoring issues in water treatment and supply systems need to be addressed...Being a special type of pollutant produced at the endpoint of water treatment plant (WTP), DBP once formed cannot be readily removed by any engineering processes in WTP without harming subsequent microbial safety. The piping system as a connector between WTP and consumer has previously demonstrated the ability of degrading some regulated DBPs like haloacetic acids. However, relatively less study was conducted toward emerging DBPs. It is uncertain if any type(s) of factors in water distribution system can impact the degradation kinetics of emerging DBPs, which mechanism is dominant, and why DBPs with similar structures behave differently from each other...In this proposal, laboratory tests are designed to investigate the reaction rates of hydrolysis, reduction, oxidation, and biodegradation processes on eight classes of halogenated compounds including halomethanes (HMs) haloacetic acids (HAAs), haloacetonitriles (HANs), haloacetaldehyde (HAs), halogenated cyanogens (HCs), haloacetamides (HAMs), haloethanes (HEs), and halonitromethanes (HNMs), with focus on N-DBP and I-DBP species. The effects of environmental factors, such as pH, temperature, dissolved oxygen, residual chlorine, chloramines, pipes, microbes, and organic matter characteristics, are to be evaluated. By an in-depth use of quantitative structure-activity relationship (QSAR) analysis, this study also commits to discovering the associations among the functional groups (e.g., NO2,C≡N，halide) and the degradability of different classes of compounds in various piping conditions. ..The information to be provided may enhance current understandings in the fate and occurrence of N-DBPs and I-DBPs in distribution systems, which are important for selecting monitoring locations, considering new DBPs to monitor, estimating exposures, and developing new treatment systems to removing emerging DBPs.

饮用水中含氮和碘代消毒副产物（DBPs）因毒性大分布广而备受关注。因DBPs产生于水厂末端的消毒环节，其生成后缺乏有效的去除方法。管网作为连接水厂和消费者的必经环节，其间发生的降解作用可影响DBPs的稳定性，并决定其发生、分布和毒性。因此，DBPs降解性能的研究已引起学术界的高度重视，并取得了一定进展。然而，有关新型DBPs在管网内的环境行为目前了解较少，不同DBPs之间行为差异的原因也不明确。据此，本课题拟模拟管网条件，以碘代和含氮DBPs为重点，分别测试八类卤代化合物的水解、氧化还原和生物降解性能；考察管网环境因素（pH、温度、溶氧、管材、消毒剂、微生物和有机物等）对DBPs稳定性的影响；同时，通过建立和验证定量构效关系（QSAR）模型，阐释官能团种类和数目对DBPs降解的作用机制。研究结果将进一步明确新型DBPs在管网中的环境行为，为其毒性评估、生成和控制提供依据。

结题摘要..饮用水中消毒副产物（DBPs）因种类多毒性大分布广而备受关注。因DBPs产生于水厂末端的消毒环节，生成后缺乏有效的去除方法。管网和家庭作为水厂和消费者的中间环节，其间发生的去除降解作用可能影响DBPs的发生种类、多少、分布和毒性。因此，有关DBPs在生成后的降解性能的研究已引起学术界的高度重视。..据此，本课题经模拟管网条件，以国家已限定和碘代、含氮DBPs为重点目标研究物质，分别测试卤代乙氰、卤代乙醛、和卤代甲烷的水解、热解和酸碱催化降解性能；考察了环境因素（pH、温度、时间、消毒剂种类和浓度和有机物等）对DBPs稳定性的影响；同时，建立了定量构效关系（QSAR）模型阐释官能团种类和数目对DBPs水解性能的影响。..本课题研究结果显示，现国标限定的三氯乙醛是一种在饮用水环境中较为稳定的物质，其水解半衰期为５天左右；但在pH超过9的碱性环境或者温度提高到40度以上时，其降解速度可显著增加从而降低其发生几率。综合本实验结果和文献结果，可建立一个三氯乙醛随ｐＨ、温度和初始浓度变化的数学模型。余氯的存在在一定浓度范围内对其降解速率没有影响，但余氯以次氯酸钠方式的投加会提高水样pH值，从而间接提高三氯乙醛的去除。整个过程中既有脱羟基效应也有脱卤效应，因此在产物中观察到了三氯甲烷、甲酸、和氯离子。此外，本研究也对碘代甲烷、卤代乙腈等碘代和含氮消毒副产物在管网和家庭加热方式等条件下进行了研究，进一步从反应速度、反应机理等多方面对ＤＢＰ的稳定性进行了了解。..通过本研究的探索，我们已经以ＮＳＦＣ为第一支持机构发表高水平ＳＣＩ期刊论文７篇、国际会议论文２篇（ＥＩ和ISTP收录）、参加国际会议两次、邀请了国外专家访问交流一次、支持了8位硕士生的培养。尽管有部分研究结果仍在投稿和数据整理过程，但基本实现了本项目申请时的研究目标。..该项目的研究结果可进一步明确各种DBPs在管网和家庭环境中的环境行为，从而为其毒性评估、生成和控制提供方法和依据。