Abstract:
There has been growing concern over human exposure to adenoviruses through drinking water due to their apparent high resistance to UV irradiation and the anticipated widespread use of UV disinfection in drinking water treatment processes. As an effort to protect the public from these important waterborne pathogens, we investigated the effectiveness of sequential disinfection with a promising alternative UV technology (medium-pressure (MP) UV) and monochloramine against human adenovirus serotype 2 (Ad2) in a typical drinking water treatment condition. Purified Ad2 was suspended in phosphate buffered saline (PBS, pH 7.2) to give a final concentration of ~107 50% Tissue Culture Infectious Dose (TCID50)/mL. A small volume (5mL) was aliquoted to a 60X15 mm cell culture dish and irradiated with a UV dose of 40 mJ/cm2 of MP UV irradiation. After UV irradiation, the UV-irradiated Ad2 was exposed to 4 mg/L of monochloramine at pH 7.0 and 10°C in PBS for 120 minutes. A small volume of samples was removed at various time points, serially diluted 10-fold, and assayed onto A549 cells grown in 24-well cell culture plates using TCID50 method. The inactivation of Ad2 by a UV dose of 40 mJ/cm2 of MP UV irradiation was ~2.4 log10. Although the inactivation of UV-irradiated Ad2 by monochloramine was slow, ~1.5 log10 inactivation was achieved within a contact time of 120 minutes. Overall, ~3.8 log10 inactivation of Ad2 was achieved with the treatment condition simulating a typical drinking water treatment. Therefore, the results of this study suggest that sequential disinfection with MP UV irradiation and monochloramine could provide an effective control measures against contamination of drinking water by human adenoviruses in typical drinking water treatment conditions.