UV and solar photocatalytic disinfection of municipal wastewater: inactivation, reactivation and regrowth of bacterial pathogens
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Pollution of water sources by pathogens is a major concern worldwide. This study investigated critical disinfection aspects such as bacterial regrowth or decay and evaluation of metal-ion leaching during photocatalytic disinfection. The inactivation of waterborne bacterial pathogens (Escherichia coli, Salmonella species, Shigella species and Vibrio cholerae) using ultraviolet and solar photocatalysis was evaluated. Bare and metal-ion (silver, copper and iron)-doped titanium dioxide photocatalysts were used to explore comparative performance. The influence of photocatalyst concentration (0.1–1.0 g/L), source of radiation (ultraviolet or solar light) and water type (synthetic and municipal wastewater) was examined. The disinfection data were fitted to the pseudo-first-order model. The disinfection efficiency was higher in saline deionized water (99.9998–100%) that was spiked with the target pathogens (106 colony forming units/mL), compared to actual wastewater samples. Within 180 min of treatment under solar irradiation, disinfection efficacy of 86.8–100% was achieved, while 99.4–100% disinfection efficacy was attained under ultraviolet irradiation within 60 min. A significant difference (p < 0.05) between ultraviolet and solar photocatalysis was observed, and silver-doped titanium dioxide displayed the best performance under all conditions tested. Nevertheless, after a contact time of 180 min, there was no bacterial regrowth observed even for the solar photocatalysis processes; in fact, bacterial decay occurred. The elution of doping metals into the treated wastewater was insignificant. Therefore, the metal-ion-doped photocatalysts were effective under solar radiation, thus overcoming the limitation of bare titanium dioxide which is only effective under ultraviolet light and preventing bacterial regrowth.
KeywordsMetal-ion doping Pathogens Titanium dioxide Ultraviolet and solar radiation Wastewater
The authors thank the National Research Foundation (NRF) for funding this study through the Egypt–South Africa joint project collaboration (Grant number 78636).
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