Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, 4001 Discovery Drive, Boulder, CO 80303, United States.
Water Res. 2023 Aug 1;241:120169. doi: 10.1016/j.watres.2023.120169. Epub 2023 Jun 3.
Concerns over human health risks associated with chemical contaminants (micropollutants) in drinking waters are rising due to the increased use of reclaimed water or water supplies impacted by upstream wastewater discharges. Ultraviolet (UV)-driven advanced oxidation processes (UV-AOPs) using radiation sources that emit at 254 nm have been developed as advanced treatments to degrade contaminants, while those UV-AOPs can be improved towards higher radical yields and lower byproduct formation. Several previous studies have suggested that Far-UVC radiation (200-230 nm) is a promising radiance source to drive UV-AOPs because the direct photolysis of micropollutants and production of reactive species from oxidant precursors can both be improved. In this study, we summarize from the literature the photodecay rate constants of five micropollutants by direct UV photolysis, which are higher at 222 than 254 nm. We experimentally determine the molar absorption coefficients at 222 and 254 nm of eight oxidants commonly used in water treatment and present the quantum yields of the oxidant photodecay. Our experimental results also show that the concentrations of HO, Cl, and ClO generated in the UV/chlorine AOP can be increased by 5.15-, 15.76-, and 2.86-fold, respectively, by switching the UV wavelength from 254 to 222 nm. We also point out the challenges of applying Far-UVC for micropollutant abatement in water treatment, including the strong light screening effect of matrix components (e.g., carbonate, nitrate, bromide, and dissolved organic matter), the formation of byproducts via new reaction pathways, and the needs to improve the energy efficiency of the Far-UVC radiation sources.
由于再生水或受上游废水排放影响的供水的使用增加，与饮用水中化学污染物（微量污染物）相关的人类健康风险引起了人们的关注。使用在 254nm 处发射的辐射源的紫外线 (UV)-驱动高级氧化工艺 (UV-AOP) 已被开发为降解污染物的高级处理方法，而这些 UV-AOP 可以朝着更高的自由基产率和更低的副产物形成方向改进。先前的几项研究表明，远紫外线辐射 (200-230nm) 是一种很有前途的辐射源，可以驱动 UV-AOP，因为可以改善微量污染物的直接光解和氧化剂前体产生的反应性物质。在这项研究中，我们从文献中总结了五种微量污染物通过直接 UV 光解的光降解速率常数，在 222nm 时比 254nm 更高。我们在实验中确定了在 222nm 和 254nm 处常用的八种氧化剂的摩尔消光系数，并提出了氧化剂光解的量子产率。我们的实验结果还表明，通过将 UV 波长从 254nm 切换到 222nm，UV/氯 AOP 中生成的 HO、Cl 和 ClO 的浓度可以分别增加 5.15 倍、15.76 倍和 2.86 倍。我们还指出了在水处理中应用远紫外线去除微量污染物的挑战，包括基质成分（例如碳酸盐、硝酸盐、溴化物和溶解有机物）的强烈光屏蔽效应、通过新反应途径形成副产物以及需要提高远紫外线辐射源的能源效率。
