Ultraviolet (UV) light has emerged as an efficient and eco-friendly disinfection technology and is now a key component in water treatment. Compared with chlorination, UV disinfection requires no chemical additives, produces almost no harmful by-products, has a small footprint, rapid reaction time, and is easy to maintain. It is widely used for drinking water, wastewater, and reclaimed water treatment. However, in practical applications, certain microorganisms inactivated by UV irradiation may still undergo reactivation through photoreactivation or dark repair mechanisms, which can impact overall disinfection performance. To prevent microbial reactivation, higher UV doses are often required, leading to increased energy consumption and operating costs, as well as concerns about equipment lifespan and reliability. Therefore, how to ensure effective inactivation while suppressing microbial reactivation has become a key focus in UV disinfection research.

A recent article published in Environmental Science & Technology (ES&T), titled "Water Disinfection with Dual-Wavelength (222 + 275 nm) Ultraviolet Radiations: Microbial Inactivation and Reactivation", explores the effects of dual-wavelength UV (DWUV) radiation, combining far-UVC and conventional UVC, on microbial inactivation and reactivation.

Study Overview

Emerging mercury-free UV sources such as krypton chloride (KrCl*) excimer lamps and UV light-emitting diodes (UV-LEDs) can emit distinct UV wavelengths and possess unique inactivation mechanisms. Their combined application offers the potential for enhanced disinfection through synergistic effects. This study developed a microfluidic photoreactor system equipped with a KrCl* lamp (222 nm) and a UV-LED strip (275 nm), capable of delivering precise single or dual-wavelength UV irradiation at intensities of 0.32 mW cm–2 (222 nm) and 0.50 mW cm–2 (275 nm).

Research Findings

DWUV irradiation showed a significant synergistic effect on the inactivation of Escherichia coli (E. coli), with a synergy factor as high as 1.92. However, no synergy was observed for the inactivation of PR772 bacteriophage. DWUV also significantly (p < 0.05) suppressed the reactivation of both E. coli and PR772 during subsequent light/dark treatments. For E. coli, the underlying mechanism was attributed to increased levels of reactive oxygen species (ROS) induced by DWUV, which enhanced inactivation by damaging proteins and lipids, and inhibited reactivation by impairing DNA repair enzymes. For PR772, although DWUV-induced DNA and protein damage did not show synergy, the protein damage prevented viral DNA from entering the host cell for repair, thus inhibiting reactivation. This study supports the development of more effective UV disinfection technologies using DWUV irradiation.

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GMY specializes in the R&D and manufacturing of lighting technology applications and offers a full range of 222 nm product solutions, including core light source components, modules, fixtures, and equipment. These solutions are suitable for water disinfection, specialized space disinfection, surface disinfection, and personal/home care disinfection applications.

Full article: https://doi.org/10.1021/acs.est.4c10128