Photo-disinfection processes for bacterial inactivation and underlying principles for water constituents' impact: A review

Photo-disinfection processes for removal of bacteria, namely solar disinfection (SODIS), ultraviolet (UV) light disinfection, and light promoted advanced oxidation processes (AOPs) based disinfection have been extensively studied. Here we aim to present the literature status of these photo-disinfection processes for bacterial inactivation and elucidate the underlying basis responsible for water constituents' impact on the efficacy of the photodisinfection processes. SODIS is a low-cost technology, effective in abundant sunlight place, and has been applied at small community level. Importantly, UV disinfection technology is very effective and has been used in fullscale treatment plants, as well as at the point of use (POU). Disinfection with light promoted AOPs are emerging and needs more research. Mainly, water constituents such as turbidity, pH, dissolved organic matter (DOM), inorganic ions, salinity, temperature, and dissolved oxygen (DO) were reported to cause a positive, negative, or neutral impact on these photo-disinfection processes. The basis for a water constituents' impacts may be due to photo-thermal, photosensitization, electrostatic interaction, coagulation, photocatalyst corrosion and passivation, aeration, ligand to metal charge transfer (LMCT) excitation, light attenuation and scattering, inner filter, blocking, UV photolysis of ions, radical formation, and scavenging effects. Water constituents causing negative effects even at a concentration below their permissible limit of drinking water standard are identified. Control of constituents in feed water is important for effective photo-disinfection.

Automated summary

Photo-disinfection processes, including solar disinfection (SODIS), ultraviolet (UV) light disinfection, and light promoted advanced oxidation processes (AOPs), have been extensively studied for bacterial inactivation. Water constituents such as turbidity, pH, dissolved organic matter (DOM), inorganic ions, salinity, temperature, and dissolved oxygen (DO) were found to have positive, negative, or neutral impacts on these photo-disinfection processes, and controlling the constituents in feed water is crucial for effective disinfection.