Improvement of water disinfection process by UV-C irradiation
In order to improve the process of water disinfection (waste water and drinking water) by UV-C irradiation, a low pressure UV lamp was supplied by two types of electronic power: traditional power at 50 Hz and high frequency power at 64 KHz. The simulation of bacterial inactivation kinetics using a mathematical model of « series-events » demonstrated the ability of the high frequency UV lamp to provide an effective UV dose capable of inactivating bacteria over a shorter exposure time than that determined for a conventional UV-C lamp. Moreover, the determination of bacterial reactivation factor (Cr) after a rest time in the presence and or in absence of visible light showed an irreversible inactivation in the tested bacteria of the photo-dependent and photo-independent reactivation mechanisms in the case of irradiation by the high frequency UV-C lamp. The increase in the bacterial inactivation without subsequent reactivation, for a reduced time of UV exposure, is consistent with the increase of the monochromatic UV spectral radiant flux at 253,7 nm provided by the high frequency power supply UV-C lamp (64 KHz). The increase of germicidal UV flux overcomes the disadvantages related to the use of a conventional UV lamp, namely the determination of a lethal dose and problems related to bacterial reactivation after treatment by ultraviolet light.