Solar water disinfection (SODIS): Impact on hepatitis A virus and on a human norovirus surrogate under natural solar conditions

This study evaluates the effectiveness of solar water disinfection (SODIS) in the reduction and inactivation of hepatitis A virus (HAV) and of the human Norovirus surrogate, murine Norovirus (MNV-1), under natural solar conditions. Experiments were performed in 330 ml polyethylene terephthalate (PET) bottles containing HAV or MNV-1 contaminated waters (10³ PFU/ml) that were exposed to natural sunlight for 2 to 8 h. Parallel experiments under controlled temperature and/ or in darkness conditions were also included. Samples were concentrated by electropositive charged filters and analysed by RT-real time PCR (RT-qPCR) and infectivity assays. Temperature reached in bottles throughout the exposure period ranged from 22 to 40° C. After 8 h of solar exposure (cumulative UV dose of ~828 kJ/m² and UV irradiance of ~20 kJ/l), the results showed significant (P < 0.05) reductions from 4.0 (±0.56) ×l0⁴ to 3.15 (±0.69) × 10³ RNA copies/100 ml (92.1%, 1.1 log) for HAV and from 5.91 (±0.59) × 10⁴ to 9.24 (±3.91) × 10³ RNA copies/100 ml (84.4%, 0.81 log) for MNV-1. SODIS conditions induced a loss of infectivity between 33.4% and 83.4% after 4 to 8 h in HAV trials, and between 33.4% and 66.7% after 6 h to 8 h in MNV-1 trials. The results obtained indicated a greater importance of sunlight radiation over the temperature as the main factor for viral reduction.