饮用水组合消毒工艺中有机氯胺的生成转化规律与风险控制研究

Due to the widespread presence of amino compounds in water sources, a kind of chlorinated derivative organic chloramines, which was usually ignored, can be produced during chlor(am)ination. They can not only interfere with the measurement of total chlorine in finished water, but also be transformed to other highly toxic N-DBPs. However, very few studies on organic chloramine control have be reported. This project will focus on the organic chloramine formation and transformation mechanisms during UV combined disinfection processes. The purpose is to explore a high-efficiency and low-risk method for organic chloramine control from the perspective of precursors and organic chloramines themselves. After the precursors are treated by UV alone and UV advanced oxidation, the effect of precursor structure change on organic chloramine generation, degradation and N-DBP transformation will be studied during the subsequent chlor(am)ination. For the generated organic chloramines, the direct removal by UV combined disinfection processes will be investigated, mainly exploring the mechanism of "UV/organic chloramines" reaction system as well as the degradation efficiency and mechanism of organic chloramines under different UV advanced oxidation processes. Besides, the risk of DBP formation during organic chloramine degradation under different processes will also be figured out. All the results of this project are expected to help control the organic chloramine generation and DBP transformation in drinking water.

水源水中普遍存在氨基类化合物，其在氯（胺）消毒过程中会生成一类常被忽略的氯代衍生物有机氯胺，其存在不仅会干扰出厂水中总余氯浓度的检测，还会转化生成其它高致毒性N-DBPs，而相关的有机氯胺削减控制技术却鲜有报导。本项目拟开展UV组合消毒工艺中有机氯胺的生成与转化机制研究，从有前体物和有机氯胺本身入手，探寻高效、低风险的有机氯胺控制技术。通过对有机氯胺前体物开展单独UV和UV高级氧化处理，探寻有机结构改变对后续氯（胺）消毒中有机氯胺生成、降解及高毒性N-DBPs转化风险的影响；针对已生成的有机氯胺，开展UV组合消毒工艺的直接去除研究，重点探索单独UV光解下“UV/有机氯胺”体系的反应机制，同时关注不同UV高级氧化工艺对有机氯胺的直接去除效能和机理，明确各工艺降解有机氯胺过程中的DBPs生成风险。研究结果将为饮用水中有机氯胺的生成及DBPs转化风险控制提供理论依据和技术支持。

氯（胺）消毒是当前国内外饮用水处理中广泛采用的消毒方式，但因水中普遍存在含氨基类溶解性有机氮物质，导致氯（胺）消毒过程极易产生一类氯代衍生物有机氯胺，属于无效余氯组分。其存在严重干扰出厂水和管网水中总余氯的测定，导致实际有效消毒剂浓度被高估，并降低了消毒剂利用率，且会转化生成其它高致毒性消毒副产物（DBPs），给水质带来生物与化学安全风险。项目重点考察了基于紫外（UV）的组合消毒工艺中有机氯胺的生成与转化规律，提出了有机氯胺与DBPs的协同控制方法。在掌握供水系统全流程中不同形态余氯分布规律基础上，揭示了混合余氯体系中包括有机氯胺在内不同形态氯的衰减转化机制，并提出在原水预氯化除藻过程中采用精准二次分段加氯方式，可有效削减余氯中有机氯胺含量，在降低氯耗、强化除藻的同时，实现三卤甲烷（总量）指标控制在0.3以内。针对富含有机氯胺前体物的高藻水源，提出采用UV辐照预处理，可实现长距离输水过程藻细胞与藻源嗅味物质高效削减，并通过光解改变藻源有机物分子结构，加速后续水厂氯胺消毒过程中有机氯胺的衰减速率，且不会导致明显DBPs产生。对于生物DNA碱基嘌呤和嘧啶等无法被UV光解的特定有机氯胺前体物，研究发现采用UV/氯高级氧化反应进行强化去除，可有效削减后续氯（胺）消毒过程中有机氯胺生成量，并且在弱碱性条件下采用275 nm UV-LED光源替代传统254 nm低压UV汞灯可实现UV/氯处理过程DBPs生成控制。针对供水系统末端已存在的有机氯胺，可采用254 nm波长的UV进行直接光解去除，且在500 mJ/cm2的UV剂量下可实现有机氯胺去除率达80%，并且常规DBPs生成量仅比未处理时增加约20%。此外，在供水系统末端混合态余氯体系中应用UV辐照，还可实现新兴高致毒性碘代DBPs生成量削减达50%。本课题研究成果可为我国供水系统中氯（胺）消毒衍生的有机氯胺风险削减提供理论依据和技术支撑。