Studies on ultraviolet light-emitting diode (UV-LED) water disinfection have shown advantages, such as safety, flexible design, and lower starting voltages. However, information about reactivation after UV-LED disinfection is limited, which is an important issue of UV light-based technology. In this study, the photoreactivation and dark repair of Escherichia coli after UV-LEDs and low pressure (LP) UV disinfection were compared. Four UV-LED units, 265 nm, 280 nm, the combination of 265 + 280 (50%), and 265 + 280 (75%) were tested. 265 nm LEDs was more effective than 280 nm LEDs and LP UV lamps for E. coli inactivation. No synergic effect for disinfection was observed from the combination of 265 and 280 nm LEDs. 265 nm LEDs had no different reactivation performances with that of LP UV, while 280 nm LEDs could significantly repress photoreactivation and dark repair at a low irradiation intensity of 6.9 mJ/cm². Furthermore, the UV-induced damage of 280 nm LEDs was less repaired which was determined by endonuclease sensitive site (ESS) assay. The impaired protein activities by 280 nm LEDs might be one of the reasons that inhibited reactivation. A new reactivation rate constant, K_max, was introduced into the logistic model to simulate the reactivation data, which showed positive relationship with the maximum survival ratio and was more reasonable to interpret the results of photoreactivation and dark repair. This study revealed the distinct roles of different UV lights in disinfection and reactivation, which is helpful for the future design of UV-LED equipment.

中文翻译：

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UV-LED和低压UV用于水消毒的比较：大肠杆菌的光活化和暗修复

对紫外线发光二极管（UV-LED）水消毒的研究已显示出诸如安全性，灵活的设计和较低的启动电压等优点。但是，有关UV-LED消毒后重新激活的信息是有限的，这是基于UV光的技术的重要问题。在这项研究中，比较了紫外线LED和低压（LP）紫外线消毒后大肠杆菌的光活化和暗修复。测试了265 nm，280 nm，265 + 280（50％）和265 + 280（75％）的四个UV-LED单元。对于大肠杆菌， 265 nm LED比280 nm LED和LP UV灯更有效灭活。从265和280 nm LED的组合中未观察到消毒的协同作用。265 nm LED与LP UV没有相同的重新激活性能，而280 nm LED在6.9 mJ / cm ²的低照射强度下可以显着抑制光重新激活和暗修复。此外，通过内切核酸酶敏感位点（ESS）测定可以确定紫外线对280 nm LED造成的损害的修复程度较低。280 nm LED破坏的蛋白质活性可能是抑制再激活的原因之一。新的重新激活速率常数，K _max，将其引入逻辑模型以模拟再活化数据，该数据与最大存活率呈正相关，并且更合理地解释光再活化和暗修复的结果。这项研究揭示了不同的紫外线在消毒和重新活化中的独特作用，这对紫外线LED设备的未来设计很有帮助。