Elimination of Pseudomonas Aeruginosa in Drinking Water by Ultraviolet – C (UV-C) Radiation

As far as the consumer is concerned presence of pathogenic bacteria in drinking water is of great health concern. Ubiquitous bacteria like Pseudomonas aeruginosa present in water are opportunistic pathogens that affect immunocompromised individuals when contaminated water is consumed. Drinking water already treated with UV radiation at the factory before bottling have been reported to contaminated with Pseudomonas aeruginosa. This controversy caught our attention as UV-treatment is intended to eradicate Pseudomonas aeruginosa in drinking water. This study aimed to systematically evaluate the efficacy of UV irradiation in eliminating P. aeruginosa in water. The proof of concept was first established by exposing sterile distilled water spiked with P. aeruginosa to varying intensities of UV-C irradiation over different exposure intervals: 10,350, 17,300 and 24,500 µW cm^-2 for 5, 10, 20 and 60 second durations and bacterial viability was tested post exposure to UV-C radiation. Further, three randomly picked bottled water brands were first analyzed for the presence of P. aeruginosa by the membrane filtration technique, using cetrimide agar supplemented with 15 mg/l of nalidixic acid and all three brands tested were positive for P. aeruginosa. Total elimination of P. aeruginosa was observed with UV-C doses of approximately 17,300 µW/cm² and 24,500 µW/cm² just with 5 seconds exposure in spiked water samples, while 10,350 µW cm^-2 showed 4-fold reduction of bacterial counts. Each of the three UV doses resulted in complete eradication of P. aeruginosa in bottled water just with 5 seconds exposure. The presence of P. aeruginosa in drinking water is not acceptable and it could raise health concerns, hence regular monitoring of the purification process and disinfection of the drinking water by using appropriate exposure levels to UV irradiation is highly recommended to safeguard the health of the consumer.