New water disinfection system using UVA light-emitting diodes

Abstract

Aim: To evaluate the ability of high‐energy ultraviolet A (UVA) light‐emitting diode (LED) to inactivate bacteria in water and investigate the inactivating mechanism of UVA irradiation. Methods and Results: We developed a new disinfection device equipped with high‐energy UVA‐LED. Inactivation of bacteria was determined by colony‐forming assay. Vibrio parahaemolyticus, enteropathogenic Escherichia coli, Staphylococcus aureus and Escherichia coli DH5α were reduced by greater than 5‐log10 stages within 75 min at 315 J cm−2 of UVA. Salmonella enteritidis was reduced greater than 4‐log10 stages within 160 min at 672 J cm−2 of UVA. The formation of 8‐hydroxy‐2′‐deoxyguanosine in UVA‐LED irradiated bacteria was 2·6‐fold higher than that of UVC‐irradiated bacteria at the same inactivation level. Addition of mannitol, a scavenger of hydroxyl radicals (OH˙), or catalase, an enzyme scavenging hydrogen peroxide (H2O2) to bacterial suspensions significantly suppressed disinfection effect of UVA‐LED. Conclusion: This disinfection system has enough ability to inactivate bacteria and OH˙ and H2O2 participates in the disinfection mechanism of UVA irradiation. Significance and Impact of the Study: We newly developed UVA irradiation system and found that UVA alone was able to disinfect the water efficiently. This will become a useful disinfection system.

Effect of Polyphenols on Reactive Oxygen Species Production and Cell Growth of Human Dermal Fibroblasts after Irradiation with Ultraviolet-A Light

“…Irradiation with ultraviolet-A UV-A light at wavelengths of 320-400 nm, and in particular light at a wavelength of 365 nm, has been reported to have lethal effects on bacteria, including pathogenic microbes Gadelmoula et al, 2009Hamamoto et al, 2007Mori et al, 2007 . UV-A light causes the generation of reactive oxygen species ROS such as singlet oxygen, superoxide anions, hydrogen peroxide and hydroxyl radicals in cells by photosensitization processes Pourzand and Tyrrell, 1999Hamamoto et al, 2007Morita et al, 1997 , resulting in lipid peroxidation and DNA oxidation Hamamoto et al, 2007 and .…”

“…UV-A light causes the generation of reactive oxygen species ROS such as singlet oxygen, superoxide anions, hydrogen peroxide and hydroxyl radicals in cells by photosensitization processes Pourzand and Tyrrell, 1999Hamamoto et al, 2007Morita et al, 1997 , resulting in lipid peroxidation and DNA oxidation Hamamoto et al, 2007 and . High bactericidal activity is caused by the combined use of UV-A light and a biocide in both cases, the bactericidal mechanism involves ROS Shirai et al, 2014 .…”

UV-LEDs Efficiently Inactivate DNA and RNA Coliphages

“…UV-absorption of proteins generally peaks at 280 nm [37] although proteins of some viruses may efficiently be affected by wavelengths below 240 nm [33,34]. In addition, wavelengths on UVA region (above 315 nm) may produce reactive intermediates and oxidative damage to DNA and other components of the bacterial cell [38,39]. Compared to a single wavelength, simultaneous treatment with multiple wavelengths of UV-C and UV-A have yielded higher reductions of fecal enterococci and total and fecal coliforms in wastewater and in pure cultures [40,41] and Vibrio parahaemolyticus in pure culture [42].…”

Combination of Light Emitting Diode at 375 nm and Photo-reactive TiO2Layer Prepared by Electrostatic Spraying for Sterilization

“…Sterilization by UV is friendlier to the environment and inactivates bacteria and viruses [2][3][4]. For many UV applications, however, there are sustainability issues that arise from current low-pressure lamp in use.…”