Ding Yizhe, Sun Qiya, Ping Qian, Wang Lin, Li Yongmei
State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, People's Republic of China.
State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, People's Republic of China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, People's Republic of China.
Water Res. 2024 Nov 15;266:122351. doi: 10.1016/j.watres.2024.122351. Epub 2024 Aug 30.
In this study, the transformation mechanisms of extracellular polymeric substances (EPS) during ultraviolet/peracetic acid (UV/PAA) disinfection were elucidated based on multiple molecular-level analyses. After UV/PAA disinfection, the contents of soluble EPS (S-EPS), loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) were reduced by 70.47 %, 57.05 % and 47.46 %, respectively. Fluorescence excitation-emission matrix-parallel factor and Fourier transform ion cyclotron resonance mass spectrometry analyses showed that during UV/PAA disinfection, EPS was transformed from the state characterized by high aromaticity, low saturation and low oxidation to the one with reduced aromaticity, increased saturation and higher oxidation. Specifically, sulfur-containing molecules (CHOS, CHONS, etc.) in EPS were converted into highly saturated and oxidized species (such as CHO), with the aromaticity index (AI) decreasing by up to 53.84 %. Molecular characteristics analyses further indicated that saturation degree, oxidation state of carbon and molecular weight exhibited the most significant changes in S-EPS, LB-EPS and TB-EPS, respectively. Additionally, mechanistic analysis revealed that oxygen addition reaction was the predominant reaction for S-EPS (+O) and TB-EPS (+3O) (accounting for 31.78 % and 36.47 %, respectively), while the dealkylation was the main reaction for LB-EPS (29.73 %). The results were consistent with functional groups sequential responses analyzed by Fourier transform infrared and two-dimensional correlation spectroscopy, and were further verified by density functional theory calculations. Most reactions were thermodynamically feasible, with reaction sites predominantly located at functional groups such as CO, CO, CN and aromatic rings. Moreover, metabolomics analysis suggested that changes in metabolites in raw secondary effluent during UV/PAA disinfection were strongly correlated with EPS transformation. Our study not only provides a strong basis for understanding EPS transformation during UV/PAA disinfection at molecular-level but also offers valuable insights for the application this promising disinfection process.
在本研究中，基于多种分子水平分析阐明了紫外/过氧乙酸（UV/PAA）消毒过程中胞外聚合物（EPS）的转化机制。UV/PAA消毒后，可溶性EPS（S-EPS）、松散结合EPS（LB-EPS）和紧密结合EPS（TB-EPS）的含量分别降低了70.47%、57.05%和47.46%。荧光激发-发射矩阵-平行因子分析和傅里叶变换离子回旋共振质谱分析表明，在UV/PAA消毒过程中，EPS从高芳香性、低饱和度和低氧化态的状态转变为芳香性降低、饱和度增加和氧化程度更高的状态。具体而言，EPS中的含硫分子（CHOS、CHONS等）转化为高度饱和和氧化的物种（如CHO），芳香性指数（AI）降低高达53.84%。分子特征分析进一步表明，饱和度、碳的氧化态和分子量分别在S-EPS、LB-EPS和TB-EPS中表现出最显著的变化。此外，机理分析表明，加氧反应是S-EPS（+O）和TB-EPS（+3O）的主要反应（分别占31.78%和36.47%），而去烷基化是LB-EPS的主要反应（29.73%）。结果与傅里叶变换红外光谱和二维相关光谱分析的官能团顺序响应一致，并通过密度泛函理论计算进一步验证。大多数反应在热力学上是可行的，反应位点主要位于CO、CO、CN和芳香环等官能团上。此外，代谢组学分析表明，UV/PAA消毒过程中原二级出水代谢物的变化与EPS转化密切相关。我们的研究不仅为在分子水平上理解UV/PAA消毒过程中EPS的转化提供了有力依据，也为这种有前景的消毒工艺的应用提供了有价值的见解。
