Disinfection performance of a drinking water bottle system with a UVC LED cap against waterborne pathogens and heterotrophic contaminants

Abstract

Background: The purgaty One systems (cap+bottle) are portable stainless-steel water bottles with ultraviolet subtype C (UVC) disinfection capability. This study examines the bottle design, verifies disinfection performance against Escherichia coli, Pseudomonas aeruginosa, Vibrio cholerae and heterotrophic contaminants and addresses the public health relevance of heterotrophic bacteria. Methods: Bottles were inoculated with bacterial strains and disinfection efficacy examined using colony forming unit (CFU) assay. The heterotrophic plate count (HPC) method was used to determine the disinfection performance against environmental contaminants at day 0 and after 3 days of water stagnation. All UVC irradiation experiments were performed under stagnant conditions to confirm that the preset application cycle of 55 seconds offers the desired disinfection performance under worst-case condition. To determine the effectiveness of purgaty One systems (cap+bottle) in disinfection, inactivation efficacy or log reduction value (LRV) was determined using bacteria concentration between UVC ON condition and controls (UVC OFF). The study utilized the 16S rRNA gene for isolate characterization by identifying HPC bacteria to confirm if they belong to groups that are of public health concern. Results: Purgaty One systems fitted with Klaran UVC LEDs achieved 99.99% inactivation (LRV4) efficacy against E. coli and 99.9% inactivation (LRV3) against P. aeruginosa, V. cholerae and heterotrophic contaminants. Based on the 16S rRNA gene analyses, the study determined that the identified HPC isolates enriched by UVC irradiation are of rare public health concern. Conclusion: The bottles satisfactorily inactivated the target pathogenic bacteria and HPC contaminants even after 3 days of water stagnation.