臭氧促进氯/氯胺消毒NDMA生成的高贡献率前体物识别及调控机制研究

N-Nitrosodimethylamine (NDMA) is a kind of new emerging nitrogen containing disinfection byproduct (DBP) and possesses highly carcinogenic effect. The probability for some precursors and certain water matrix to promote the NDMA formation during disinfection processes by pre-ozonation, restricts the widely application of ozone in the drinking water treatment, and it cannot be ignored for the safety of drinking water. This project aims to develop a coupling evaluation technology of formation potential and generation rates of NDMA, and accurately screen out the precursors with high contribution rates from model precursors and water matrix, which react with ozone easily and facilitate the NDMA formation from subsequent chlorination/ chloramination processes; then, by analyzing the steady-state products by mass spectrometry (MS) and isotope labelling techniques, and capturing transient radicals by time-resolved spectrum and Electron Spin Resonance (ESR), a path analytic technique was created according to the results of transient products and steady products; meanwhile, the promotion mechanisms as well as the key factors that affect NDMA generation from the high contribution rates precursors were revealed from the view of quantum mechanics and molecular level; finally, based on the coupling regulating methods with the front-end control and the process control, a comprehensive integrated control scheme is put forward to prevent or reduce the NDMA formation from high contribution rates precursors during disinfection process by pre-ozonation. The results of this research would provide theoretical basis and technical supports for the widely application of ozone and the promotion of drinking water quality.

二甲基亚硝胺(NDMA)是具有强致癌性的一种新型含氮消毒副产物，臭氧预氧化会促进某些前体物或水体后续消毒生成这种物质，危害饮用水安全，限制臭氧在饮用水处理中的推广应用。本课题拟开发NDMA生成潜能和生成速率耦合评价技术，从典型前体物及实际水体中识别出易与臭氧反应促进后续氯、氯胺消毒生成NDMA的高贡献率前体物；利用质谱及同位素标记技术分析稳态产物，采用时间分辨吸收光谱和电子自旋共振波谱法(ESR)捕捉瞬态粒子，创建基于瞬态粒子和稳态产物相结合的路径解析技术；同时，从量子力学和分子水平探究影响高贡献率前体物生成NDMA的关键因子及其作用机制；建立基于前端调控和过程调控的耦合调控方法，提出防止或消减预氧化促进高贡献率前体物后续消毒NDMA生成的综合控制方案。研究成果为臭氧的更广泛应用提供理论依据和技术支撑，保障饮用水安全。

消毒在灭活微生物的同时，不可避免与水中有机物反应生成副产物。二甲基亚硝胺(NDMA)是具有强致癌的新型含氮消毒副产物，一旦生成，很难去除，亟需在生成前去除其前体物。臭氧氧化性强，常作为削减NDMA生成的预氧化措施，但也存在促进某些物质或水体生成该副产物风险，危害饮用水安全。. 选择典型胺基化合物，考察其在臭氧、氯、氯胺、臭氧/氯、臭氧/氯胺过程中NDMA生成量，建立与前体物结构（摩尔折射率MR、解离系数pKa、辛醇水分配系数logKow、偶极矩μ）的构效关系（QSAR）模型。结果表明，臭氧促进后续消毒生成NDMA是易与臭氧反应，但与氯和氯胺生成有限的物质；一般含偏二甲肼(CH3)2N-N-或(CH3)2N-R-N-结构（R-易移去基团或者吸电子基团）。亲水性组分、带正电组分含量高的实际水体易生成NDMA；这也正与QSAR模型结论一致，lgKOW越小，亲水性越强，NDMA生成越多。. 选择植物生长抑制剂丁酰肼和合成表面活性剂原料N,N-二甲基-1，3-丙二胺（DMAPA），考察臭氧促进后续消毒生成NDMA促进机制和影响因素，以期提出控制措施。预臭氧促进丁酰肼后续氯/氯胺生成NDMA，且随臭氧量增加而增加；可在碱性条件下使用预臭氧工艺。对于DMAPA类物质，随臭氧量增加，氯胺消毒时NDMA生成量先增加后降低，氯消毒时却一直增加；且随pH变化不大；对于这类前体物，应选择氯胺消毒，通过提高臭氧量或采用催化臭氧来削减其生成。质谱结果证实臭氧促进NDMA生成原因是中间产物的摩尔产率大于母体物质；电子自旋共振波谱表明羟基是影响其生成的重要因素。. 针对不同前体物应采取防止或削减NDMA生成的应对措施也不同，如通过提高臭氧投加量、采用催化臭氧或改变预氧化方式，实现前端调控；而通过选择合适的消毒方式，实现过程调控，提出综合控制方案。研究成果为臭氧的更广泛应用提供理论依据和技术支撑，保障饮用水安全。