Ma Ben, Seyedi Saba, Wells Emma, McCarthy David, Crosbie Nicholas, Linden Karl G
Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, 4001 Discovery Dr., Boulder, CO, 80303, United States.
Department of Civil Engineering, Monash University, Clayton, Vic, 3800, Australia.
Water Res. 2022 Jun 15;217:118379. doi: 10.1016/j.watres.2022.118379. Epub 2022 Mar 31.
Opportunistic pathogens (OPs), such as Pseudomonas spp., Legionella spp., and mycobacteria, have been detected in biofilms in drinking water distribution systems and water storage tanks and pose potential risks to finished drinking water quality and safety. Emerging UV technologies, such as UV light emitting diodes (LEDs) and krypton chloride (KrCl*) excimers, could provide an alternative to chemical-based secondary disinfection (i.e., chlorine or chloramines) for controlling biofilm-bound OPs. UV systems offer long lifetimes, ability to select wavelength, small size with high power density, and limited-to-no disinfection by-product formation. In this study, inactivation of biofilm-bound Pseudomonas aeruginosa cells across different maturities was investigated using five UVC devices with different peak emission wavelengths, including a KrCl* excimer (222 nm), a low pressure mercury vapor lamp (254 nm), and three UV LEDs (260 nm, 270 nm, and 282 nm). The UV transmittance and absorbance through the biofilm structure was also documented for the first time using a unique approach. Our results show all UVC devices can inactivate biofilm-bound P. aeruginosa cells up to a point, among which the UV LED with peak emission at 270 nm provided the best disinfection performance. UV sensitivities of biofilm-bound cells decreased with biofilm maturity and while initial rates of inactivation were high, no more than 1.5-2.5 log reduction was possible. Re-suspended biofilm bacteria in aqueous solution were highly sensitive to UV, reaching greater than 6 log reduction. UV shielding by biofilm constituents was observed and was likely one of the reasons for UV resistance but did not fully explain the difference in UV sensitivity between biofilm-bound cells versus planktonic cells. This study improves upon fundamental knowledge and provides guidance for innovative designs using emerging UV technologies for biofilm and pathogen control in water distribution systems.
在饮用水分配系统和储水箱的生物膜中已检测到诸如假单胞菌属、军团菌属和分枝杆菌等机会性病原体（OPs），它们对成品饮用水的质量和安全构成潜在风险。新兴的紫外线技术，如紫外线发光二极管（LED）和氯化氪（KrCl*）准分子，可为控制生物膜结合的OPs提供一种替代基于化学的二次消毒（即氯或氯胺）的方法。紫外线系统具有寿命长、能选择波长、尺寸小且功率密度高以及几乎不产生消毒副产物的特点。在本研究中，使用五个具有不同峰值发射波长的UVC设备，包括一个KrCl*准分子（222纳米）、一个低压汞蒸气灯（254纳米）和三个紫外线LED（260纳米、270纳米和282纳米），研究了不同成熟度的生物膜结合铜绿假单胞菌细胞的失活情况。还首次采用独特方法记录了穿过生物膜结构的紫外线透过率和吸光度。我们的结果表明，所有UVC设备都能在一定程度上使生物膜结合的铜绿假单胞菌细胞失活，其中峰值发射波长为270纳米的紫外线LED消毒性能最佳。生物膜结合细胞的紫外线敏感性随生物膜成熟度降低，虽然初始失活率很高，但最大失活不超过1.5 - 2.5个对数级。重新悬浮在水溶液中的生物膜细菌对紫外线高度敏感，失活超过6个对数级。观察到生物膜成分对紫外线有屏蔽作用，这可能是抗紫外线的原因之一，但不能完全解释生物膜结合细胞与浮游细胞之间紫外线敏感性的差异。本研究完善了基础知识，并为利用新兴紫外线技术进行创新设计以控制配水系统中的生物膜和病原体提供了指导。
