再生水消毒过程中脂肪胺类抗抑郁药物及其活性代谢产物的降解机理及消毒副产物生成特性研究

Disinfection is required of sewage regeneration，the safety of disinfected reclaimed water is key to its utilization. Antidepressant pharmaceuticals and their active metabolites, a group of new emerging contaminants with aquatic toxicity, have been frequently detected in the secondary effluent. However, the characteristics of their transformation mechanisms and the formation of by-products during the disinfection of reclaimed water have not been clearly demonstrated, which could present potential risks to the water quality safety of reclaimed water. This research attempts to investigate the transformation characteristics and degradation mechanisms of citalopram and venlafaxine as well as their active metabolites desmethyl-citalopram and O-desmethyl-venlafaxine during typical disinfection processes of reclaimed water in light of their frequent occurrences in the secondary effluent. Kinetics analysis and intermediate products identification are used to reveal degradation pathways. The formation of disinfection by-products, such as nitrosamines, from the above four pharmaceuticals degradation during disinfection process is also studied since aliphatic amines with dimethylamine function group are the common structure in these compounds. The key factors influencing disinfection by-products generation are investigated based on results from nitrosamines formation characteristics and the effects of reclaimed water composition. And then the method of disinfection by-products control is proposed. The transformations of the antidepressants during disinfection process are also studied in full-scale municipal wastewater reclamation treatment plants. The results will be able to provide a scientific basis for assessing the potential hazards of antidepressants to environment, and are helpful for controlling the disinfection by-products of reclaimed water.

消毒是污水再生利用的必需环节，保障再生水消毒后的水质安全是再生水利用的关键。抗抑郁药物及其活性代谢产物是一类新型环境污染物，具有水生生物毒性，在污水二级处理出水中被频繁检出。然而，此类药物在污水再生消毒过程中的转化机制及副产物的生成规律尚不明确，这势必会对再生水水质安全构成潜在风险。本项目拟选取检出频率较高的脂肪胺类抗抑郁药物西酞普兰、文拉法辛及其活性代谢产物去甲基西酞普兰、O-去甲文拉法辛为研究对象，考察其在典型再生水消毒工艺中的转化特性和降解机理，通过动力学研究、降解产物检测，阐明其降解途径。针对上述药物结构中含有二甲胺基团的特性，辨识其降解过程中生成的亚硝胺类消毒副产物及生成规律，结合水质影响分析，探明重要影响因素和控制方法。最后，对实际再生水厂消毒过程中抗抑郁药物的降解进行调查研究，为进一步评价抗抑郁药物对水环境产生的危害提供科学依据，为有效控制再生水中的消毒副产物提供基础数据。

本项目主要研究了七种含二甲胺基团的常见抗抑郁药物在不同氯消毒过程中生成亚硝基二甲胺（NDMA）的特性，考察了初始浓度、消毒剂量、水质条件等对NDMA生成的影响。重点研究了水环境中检出率较高的西酞普兰、文拉法辛在紫外消毒过程中的去除情况，并对文拉法辛降解过程中的中间产物进行了检测分析，初步提出其降解途径。还针对次氯酸钠、二氧化氯消毒过程中的西酞普兰降解进行了探讨。旨在明确潜在的NDMA前体物，揭示NDMA生成的特性，从而优化消毒工艺。. 研究得出：西酞普兰、文拉法辛等七种抗抑郁药物在三种氯消毒的过程中均会导致NDMA的产生。采用氯胺消毒时，七种药物的NDMA产率最高，次氯酸钠次之，二氧化氯最低。NDMA的产率主要与药物的结构性质有关，而不易受到溶液pH值影响。污水二级出水中共存的有机物等物质会导致更多的NDMA产生。紫外光可通过直接光解以及自敏化作用有效去除水中的西酞普兰、文拉法辛，降解过程符合伪一级动力学模型，分别在pH值为6、10时，降解速率最快。水体中的天然有机物如腐殖酸、富里酸等会抑制药物的降解。常见的无机阴离子Br-、Cl-、NO3-和NO2-均会抑制文拉法辛降解，其中NO2-的抑制作用最强。并通过中间产物分析，提出文拉法辛降解的5种主要途径。研究还发现次氯酸钠、二氧化氯消毒过程西酞普兰的去除可在40 min内完成，且不易受溶液pH值影响。而NDMA的生成则持续了10 d，且呈两个阶段，其中第一阶段为反应的第1天，反应速率明显大于第二阶段。实际水体中西酞普兰的降解受到了抑制，然而NDMA的生成并未受此影响。相反地，反而会导致了更多的NDMA产生。