Traditional disinfection technologies not only consume corrosive agents (such as Cl₂ and O₃) but also generate toxic disinfection by-products. Without these drawbacks, ultraviolet disinfection technology has been used widely in water and wastewater treatment. However, some pathogenic bacteria can repair their ultraviolet damage and reactivate, which brings health risk. Photocatalytic disinfection is a safe alternative, since photogenerated reactive oxygen species are confirmed to destroy not only DNA but also plasma membrane and effluent protein, then killing pathogenic bacteria utterly. Furthermore, both UV and photogenerated reactive oxygen species participate in the sterilization process and increase the rate of disinfection. Therefore, compared to ultraviolet disinfection, photocatalysis displays a superior ability to kill microorganisms fastly and thoroughly. This paper presents the advantages of photocatalysis over other disinfection technologies including chlorine-containing disinfectant, ozone and ultraviolet. Special attention is paid to the disinfection mechanisms of various photogenerated oxidative radicals. Typical photocatalytic composites including semiconductor-carbon with membrane stress, semiconductor-metal with oxidative stress and semiconductor-DNA aptamer with ability to capture microbial cell are summarized. Furthermore, three kinds of possible application modes of photocatalytic disinfection, including annular reactors, fixed bed reactors and membrane separation reactors, are reviewed. Finally, research prospects are proposed for the future development of photocatalysis in disinfection.
Contents
1 Introduction
2 Disinfection mechanism on photogenerated reactive oxygen species
2.1 Hydroxyl radical
2.2 Singlet oxygen
2.3 Hydrogen peroxide
2.4 Halogenic radical
3 Pathogenic microorganisms
3.1 Common bacteria
3.2 Viruses
3.3 Protozoa
3.4 Antibiotic resistant bacteria and antibiotic resistance genes
4 Photocatalytic materials for disinfection
4.1 TiO₂
4.2 Non-TiO₂-based photocatalysts
4.3 Composite of photocatalyst and nano carbon material with membrane stress
4.4 Composite of photocatalyst and nano metal materials with oxidative stress
4.5 Composite of photocatalyst and DNA aptamer
5 Reactors for photocatalytic disinfection
5.1 Annular reactors
5.2 Fixed bed reactors
5.3 Membrane separation reactors
6 Conclusion