Ultraviolet (UV) irradiation can inactivate a broad range of pathogens effectively and has been used for disinfection of drinking and wastewater. No disinfection byproducts formation is one of the advantages of using UV. But the UV irradiated pathogens may recover their reproduction abilities by photoreactivation and dark repair. The probability of adding titanium dioxide (TiO₂) particles during the UV disinfection process for repressing the recovery was investigated. Results showed that the addition of low concentrations of TiO₂ during UV irradiation can repress the photoreactivation and dark repair of coliform bacteria under different conditions. When coating TiO₂ on glass or using hydrogen peroxide (H₂O₂) instead of suspending TiO₂ particles, a similar repressive effect was shown....[ Read more ]

Ultraviolet (UV) irradiation can inactivate a broad range of pathogens effectively and has been used for disinfection of drinking and wastewater. No disinfection byproducts formation is one of the advantages of using UV. But the UV irradiated pathogens may recover their reproduction abilities by photoreactivation and dark repair. The probability of adding titanium dioxide (TiO₂) particles during the UV disinfection process for repressing the recovery was investigated. Results showed that the addition of low concentrations of TiO₂ during UV irradiation can repress the photoreactivation and dark repair of coliform bacteria under different conditions. When coating TiO₂ on glass or using hydrogen peroxide (H₂O₂) instead of suspending TiO₂ particles, a similar repressive effect was shown.

By the study of oxidative stress of E. coli ATCC 15597, not only the oxidative stress, also the highly reactive intracellular hydroxyl radical concentration was increased during the TiO₂-UV and H₂O₂-UV co-exposure, compared to UV irradiation. This gives one of the possible explanations for the repressive effect. The pilot evaluation of a UV disinfection unit with TiO₂ coating was conducted to study the effectiveness and catalyst poisoning effect of TiO₂ in long-term runs in different water matrixes. The results showed TiO₂ was poisoned by multi-valent cations in seawater, but the activity can be recovered by rinsing with deionized water. Organic matters also poisoned the catalyst and the adsorbed organic matters can not be washed out by deionized water only because of its hydrophobic nature.