紫外辐射对饮用水碘代消毒副产物生成的影响机制与调控

Drinking water disinfection by-products (DBPs), which are formed during the chemical disinfection process, are reported to be very carcinogenic, mutagenic and teratogenic. As the DBPs issue is directly related to the drinking water safety, they have already aroused great concerns in water treatment area. Therefore, it has great theoretic and practical implications to study on the formation mechanism, influencing factors as well as control methods of emerging high toxic iodinated disinfection by-products (I-DBPs). In our previous studies, the applicants were the first to report the UV phototransformation pathways of these emerging iodine sources (iodate and iodinated X-ray contrast media) as well as their I-DBPs formation characteristics during subsequent oxidation. However, further investigations on this topic are still urgently needed. In the presence of dissolved organic matter and iodine source precursor, the phototransformation effect of UV irradiation could be greatly enhanced, which will have significant impact on the I-DBPs formation during subsequent oxidation process. On this account, this subject aims to investigate the UV influencing mechanisms and control efficiency of UV/chlorine on the formation of I-DBPs. Through the study of I-DBPs formation characteristics and iodine fate, the influencing mechanisms of UV irradiation on the two different iodine source systems of iodide and iodate could be revealed. Then the transformation characteristics of UV/chlorine process on iodate and I-DBPs formation features in the following oxidation process, which is a practical UV photo-induced advanced oxidation process, will be studied. The degradation ability on iodate and control efficiency on I-DBPs formation of UV/chlorine can be evaluated. The results of this subject could provide effective theoretical support for I-DBPs control during drinking water treatment in our country.

饮用水消毒时所产生的“三致性”消毒副产物直接关系到饮用水安全，一直受到高度关注。而对新兴高毒性碘代消毒副产物（I-DBPs）影响机制和控制方法的研究尤其具有重要的理论和现实意义。申请人在前期已率先报道了紫外对碘酸盐和碘化显影剂降解与氧化生成I-DBPs的特性。但相关研究仍需进一步深入，尤其在有机物与碘源共存时紫外转化作用将大大增强，这必然会对后续消毒产生的I-DBPs造成显著影响。为此本课题拟研究紫外辐射对I-DBPs生成的影响机制及相关工艺调控作用。通过研究紫外处理碘离子尤其是最新碘源前体—碘酸盐体系氧化生成I-DBPs的特性及碘形态归趋，揭示其生成I-DBPs的紫外影响机制。通过研究紫外/氯对碘酸盐的降解特性及后续氧化中I-DBPs的生成规律，探索这种实用组合式高级氧化工艺对碘酸盐的转化效能及对I-DBPs的调控作用。从而为我国饮用水处理中I-DBPs的有效削减提供理论依据和技术支持。

饮用水消毒时所产生的“三致性”DBPs直接关系到饮水安全一直受到高度关注。而对新兴高毒性碘代消毒副产物（I-DBPs）影响机制和控制方法的研究尤其具有及其重要的理论和现实意义。本课题以饮用水消毒过程中UV对I-DBPs生成的影响机制及相关工艺的调控作用为研究重点，针对目前已确认的有机碘源前体（iopamidol）和最新无机碘源前体（iodate）系统性开展了基于UV的AOP技术对其转化特性、归趋行为与削减规律等方面工作。以碘帕醇为研究对象，对比考察了基于UV的常用AOP技术（包括UV/Cl2, UV/NH2Cl, UV/ClO2和UV/H2O2）对其降解转化特性、能耗需求及后续消毒过程中生成DBPs相关毒性。这些工艺中碘帕醇降解效能排序为UV/Cl2>UV/H2O2>UV/NH2Cl>UV/ClO2>UV。UV与这些常用氧化剂的协同增效效是由其各自系统中产生的自由基所致。进而考察了不同因素包括氧化剂投加量、光强、pH及氯离子、铵离子和NOM等的作用。这些工艺能耗排序为UV/ClO2>UV>UV/NH2Cl>UV/H2O2>UV/Cl2，而DBPs相关水质毒性排序为UV/NH2Cl>UV/Cl2>UV>UV/H2O2>UV/ClO2。UV/Cl2被证明是降解碘帕醇中最有成本/效率的过程，而UV/ClO2则表现出了对DBPs毒性尤其是I-THMs的绝对控制优势。本成果昭示了对这些UV-AOPs的应用考量中须寻求成本效益评估和DBPs相关毒性控制的权衡与取舍。还以碘酸盐为研究对象系统考察了UV/H2O2 这种最常见的AOP对碘酸盐的转化特性和对后续氯胺化中I-DBPs的产生规律。UV/H2O2不仅明显提高碘酸盐的降解速率，且能显著提高氯胺化I-THMs的生成。由于多种高活性自由基组分贡献，UV/H2O2比单独UV或H2O2处理碘酸盐分解快得多。而相关参数如H2O2用量、pH、UV强度及NOM存在等对碘酸盐的降解有不同作用。UV/H2O2比UV更能促进碘酸盐向I-THMs的转化，从而提高了消毒水在后续氯胺化中的毒性。本研究首次揭示了碘酸盐这种新兴碘源前体在UV/H2O2中转化为I-THMs的特性，为全面了解诸多AOP调控I-DBPs可行性技术打开了一扇探究之窗。本课题探索解决了饮用水处理出现的新兴高毒性I-DBPs的调控这一新难题，有利于有效降低其带来的水质风险。