Kinetic modeling of the synergistic thermal and spectral actions on the inactivation of viruses in water by sunlight

Sunlight can be an effective tool for inactivating pathogens in water disinfection processes. In clear water,
photoinactivation of viruses is driven by the absorption of UVB radiation and it is more efficient at
shorter wavelengths. Moreover, the temperature can significantly improve the efficiency of the process.
To date, no kinetic model has been reported that describes the simultaneous thermal and spectral effects
that occur during the solar inactivation of viruses. This work presents a novel comprehensive kinetic
model for the solar inactivation of MS2 coliphage as a function of the water temperature, irradiance, and
spectral distribution of the incident radiation. The model is based on a combination of the modified
Arrhenius equation, a wavelength-dependent first-order inactivation model with the quantumyield, and
thermal parameters estimated from laboratory data. Model predictions have a 9% error with respect to
experiments in the temperature range from 30 to 50 C and UV irradiance range from 15 to 50 W/m2.
Moreover, the model was validated in three scenarios using different plastic materials that modify the
spectral range of the radiation reaching the water, confirming an accurate prediction of inactivation rates
for real solar disinfection systems worldwide using containers made of any material.