组合消毒工艺中持久性人工甜味剂的转化规律及其氯代DBPs的生成机理研究

Artificial sweeteners acesulfame (ACE) and sucralose (SUL) which are characterized with high hydrophilicity, outstanding persistence are recognized as emerging contaminants in recent years. Their ubiquitous occurrences in aqueous environments such as surface water, ground water, marine water and even drinking water at high concentrations attracted more and more attention. However, the contamination threats they bring to the drinking water and the effective control processes are not thoroughly understood due to limited research. In this project, to fulfill the major requirement of drinking water safety and contamination risk management, laboratory simulation methods together with field investigations are proposed to reveal the transformation and fate of persistent sweeteners in combined disinfection processes of drinking water. For the first time, chlorinated nitrogenous DBPs and dechloro(chlorosugar)-DBPs are proposed to be formed from parent sweeteners, and their producing conditions, influencing factors and also generative pathways are investigated and discussed following the establishment of the assembly detection methods of DBPs. Characteristics such as toxicity, stability and taste & odor of DBPs are generally explored. Aesthetics of taste and odor is evaluated to describe the human exposure to sweeteners and corresponding DBPs. Aesthetics together with DBPs formation potentials and toxicity is used to evaluate the influences from water matrix and operating conditions of disinfection processes, therefore, the control mechanisms of DBPs during the processes are investigated. The achievements of this project will provide theory and technology for the identification and control of sweetener contaminants and their DBPs, so as to improve the safety of water supply.

人工甜味剂安赛蜜和三氯蔗糖是一类高极性、持久性新型污染物，因其在各类水环境中以高浓度水平广泛检出而成为近年来的热点问题，然而此类污染对饮用水可能造成的特征危害及其有效控制技术仍缺乏深入研究。本项目围绕持久性甜味剂在饮用水组合消毒工艺中的转化行为，构建成组检测分析方法，系统剖析氯代消毒副产物—含氮DBPs及脱氯（氯代糖类）DBPs等与安赛蜜和三氯蔗糖的源生关系，展开典型DBPs生成条件、影响因素及产生机理研究；全面阐释安赛蜜和三氯蔗糖衍生DBPs的毒性、稳定性及嗅与味等污染特性；提出饮用水甜味剂及其DBPs暴露下的Taste & odor指标，结合DBPs生成势及毒性效应变化构建指标体系，深入剖析不同组合消毒技术和工艺条件中DBPs的过程调控机理。成果可为饮用水新型污染物的风险管理、消毒副产物的早期预警及过程控制提供理论依据和技术支撑，对保障饮用水供水安全具有重要的科学及社会意义。

三氯蔗糖（sucralose, SUC）和安赛蜜（acesulfame, ACE）等人工甜味剂（artificial sweeteners，ASs）是一类人工合成蔗糖代替物，作为添加剂用于食品、药品及个人护理中。不为人体吸收或降解，大部分通过污水排放进入水环境中。SUC和ACE难以生物降解，具有持久性，在水环境中半衰期可达数月乃至数年，是水环境中广泛检出，存在浓度较高的微量有机污染物。本项目建立了简便、快捷及易于常规检测的水中微量ASs的液相色谱和气质联用分析方法，展开了水处理系统及饮用水中ASs污染水平调查，考察了持久性SUC和ACE等典型ASs在净水工艺中的迁移和转化，阐明了在常用氯消毒，氯胺消毒和臭氧/氯消毒过程中衍生消毒副产物（disinfection by-products, DBPs）的规律，提出了可有效减少ASs及其衍生DBPs的控制技术。结果表明在选定的调研区域内，持久性SUC（1033.4~ 2626.3 ng/L）在污水处理中难以降解，地表水源中SUC（376.2~ 2070.0 ng/L）进入净水工艺，常规和深度处理净水工艺均无法彻底，约有11.2%~25.5%最终进入饮用水供水管网（177.7~ 409.7 ng/L）到达用户，当浓度高于阈值后将产生甜味或其他协同嗅味类水质影响；另外一部分SUC将在净水工艺中产生风险转化，深度处理的降解产物和氯消毒阶段产生的DBPs。SUC具有抗氯性，但在臭氧/氯消毒过程中可产生较高量的三氯乙酸（23.32μg/mg SUC），三氯甲烷产量低。ACE和糖精（saccharin, SAC）等ASs在净水工艺及管网中的存在浓度低于SUC，但在直接氯消毒和臭氧/氯消毒过程中均可产生DBPs。ACE在直接氯消毒过程中产生三氯甲烷（6.72μg/mg ACE），卤乙酸（8.74μg/mg ACE），二氯乙腈（0.143 μg/mg ACE），臭氧/氯消毒可减少三氯甲烷的产量，卤乙酸产量略有上升。UV及硫酸盐高级氧化体系可有效的控制水中ASs，但工艺参数和水中基质等可影响ASs的转化，可导致后续氯消毒工艺中DBPs含量升高。在水源地栽种石菖蒲、水葱等水生生物可实现ACE的吸收去除，减少进入净水工艺的人工甜味剂，为水源新型污染物ACE的去除提供了有效的生态处理途径，是减少ASs导致饮用水水质风险的有效途径之一。