Water Disinfection with Dual-Wavelength (222 + 275 nm) Ultraviolet Radiations: Microbial Inactivation and...

Area of Science:

• Microbiology
• Photochemistry
• Environmental Engineering

Background:

• Emerging mercury-free UV sources like KrCl* lamps and UV-LEDs offer distinct inactivation mechanisms.
• Combined UV wavelengths present potential for enhanced disinfection through synergistic effects.

Purpose of the Study:

• To develop and evaluate a dual-wavelength UV (DWUV) system combining KrCl* (222 nm) and UV-LED (275 nm) for disinfection.
• To investigate the synergistic effects of DWUV on microbial inactivation and reactivation suppression.

Main Methods:

• A mini-fluidic photoreaction system was designed to deliver precise UV doses at 222 nm and/or 275 nm.
• Inactivation and reactivation of Escherichia coli (E. coli) and PR772 bacteriophage were assessed under different UV conditions.
• Mechanisms, including reactive oxygen species (ROS) and cellular damage, were analyzed.

Main Results:

• DWUV radiation exhibited significant synergistic effects on E. coli inactivation (synergistic coefficient up to 1.92).
• No synergistic inactivation effect was observed for PR772 bacteriophage.
• DWUV significantly suppressed the reactivation of both E. coli and PR772.
• Increased ROS levels and damage to DNA repair enzymes in E. coli were observed.
• Protein damage in PR772 prevented viral DNA repair, suppressing reactivation.

Conclusions:

• DWUV disinfection using KrCl* and UV-LEDs demonstrates potent synergistic inactivation and reactivation suppression against E. coli.
• The mechanisms involve enhanced ROS production and damage to critical cellular components and repair pathways.
• This technology offers a promising mercury-free alternative for effective UV disinfection.