Yu Zhe, Xie Yicheng, Li Xiqi, Liu Wenzong, Han Jing-Long, Zheng Chunyuan, Zheng Qun, Zhao Xuezhi, Wang Aijie
School of Civil and Environmental Engineering, Harbin Institute of Technology Shenzhen, Shenzhen 518055, China.
School of Civil and Environmental Engineering, Harbin Institute of Technology Shenzhen, Shenzhen 518055, China; State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150001, China.
Water Res. 2025 Apr 15;274:123122. doi: 10.1016/j.watres.2025.123122. Epub 2025 Jan 9.
Due to the global outbreaks caused by pathogens, disinfection has attracted widespread attention, especially as the final inactivation step in wastewater treatment plants (WWTPs). Ultraviolet (UV) radiation is regarded as one of low carbon disinfection methods without chemical agents, but in practice, the effects are sometimes unsatisfactory, e.g., Escherichia coli (E. coli) still stay alive excessively at low concentrations of suspended solids (SS) that meets the discharge standards (<10 mg l). WWTPs focus on each process's efficiency, while the particle influence of different upstream processes on UV radiation is ignored. This study investigated the changes in extracellular polymeric substances (EPS) structure and biofilm from the perspective of single cell and cell-to-cell interactions at low SS concentrations before and after UV radiation. We disclosed that the effective characteristics of effluent SS particles were mainly related to some specific operation units, like coagulation sedimentation or sand filtration, which induced EPS secretion and biofilm formation, and subsequently caused the different responses of cells within the biofilm to UV radiation. Compared with filtrating sand particles, the magnetic coagulant induced more polysaccharide secretion and expanded the EPS structure, leading to a thicker and more effective protective layer to weaken UV intensity and reduce reactive oxygen species levels inside cells. The microbial community analysis of a real WWTP confirmed the survival of microorganisms with abilities of EPS secretion and sheltering others. Therefore, considering the potential positive effect of particles (such as metal particles) in the upstream process on the microbial aggregation in the subsequent process, it is recommended that the UV disinfection requires a lower SS concentration standard or a higher UV radiation dose. This study provides a basis for effective UV disinfection at the present application standards.
由于病原体引起的全球疫情爆发，消毒受到了广泛关注，尤其是作为污水处理厂（WWTPs）中的最终灭活步骤。紫外线（UV）辐射被视为无化学药剂的低碳消毒方法之一，但在实际应用中，其效果有时并不理想，例如，在符合排放标准（<10 mg l）的低悬浮固体（SS）浓度下，大肠杆菌（E. coli）仍大量存活。污水处理厂关注每个工艺的效率，而不同上游工艺对紫外线辐射的颗粒影响却被忽视。本研究从单细胞和细胞间相互作用的角度，研究了低SS浓度下紫外线辐射前后细胞外聚合物（EPS）结构和生物膜的变化。我们发现，出水SS颗粒的有效特性主要与一些特定的操作单元有关，如混凝沉淀或砂滤，这些操作会诱导EPS分泌和生物膜形成，进而导致生物膜内细胞对紫外线辐射产生不同反应。与滤砂颗粒相比，磁性混凝剂诱导更多的多糖分泌并扩展了EPS结构，形成了更厚且更有效的保护层，以减弱紫外线强度并降低细胞内活性氧水平。对实际污水处理厂的微生物群落分析证实了具有EPS分泌和保护其他微生物能力的微生物的存活。因此，考虑到上游工艺中颗粒（如金属颗粒）对后续工艺中微生物聚集的潜在积极影响，建议紫外线消毒需要更低的SS浓度标准或更高的紫外线辐射剂量。本研究为当前应用标准下的有效紫外线消毒提供了依据。
