Microbial UV fluence-response assessment using a novel UV-LED collimated beam system

Area of Science:

• Microbiology
• Photochemistry
• Environmental Engineering

Background:

• Ultraviolet light-emitting diodes (UV-LEDs) offer advantages over traditional mercury lamps, including mercury-free operation, design flexibility, and longer lifespan.
• Optimizing UV-LED collimated beam design is crucial for effective microbial inactivation applications.

Purpose of the Study:

• To determine the ultraviolet (UV) fluence-response of non-pathogenic microorganisms to UV-LEDs.
• To compare the efficacy of UV-LEDs with traditional low-pressure mercury lamps for microbial inactivation.

Main Methods:

• Collimated beam tests were performed using optimized UV-LED and mercury lamp apparatus.
• The study evaluated the inactivation of Escherichia coli, MS-2, and T7 surrogate microorganisms.
• UV fluence-response was assessed using 255 nm UV-LEDs, 275 nm UV-LEDs, and 254 nm low-pressure mercury lamps.

Main Results:

• Low-pressure mercury lamps achieved greater inactivation of E. coli and MS-2 compared to both 255 nm and 275 nm UV-LEDs.
• T7 inactivation was similar between 275 nm UV-LEDs and mercury lamps.
• 275 nm UV-LEDs were more effective than 255 nm UV-LEDs for T7 and E. coli inactivation, with comparable MS-2 inactivation between the two UV-LED wavelengths.

Conclusions:

• UV-LEDs show potential for microbial inactivation, but their efficiency varies with wavelength and microorganism.
• Observed differences in inactivation may be attributed to microbial repair mechanisms and deviations from the time-dose reciprocity law.