The virus removal in UV irradiation, ozonation and chlorination

Abstract

The COVID-19 pandemic draws much attention to virus inactivation since the SARS-CoV-2 was detected in miscellaneous environments and the wastewater can be a potential transmitting pathway. UV irradiation, ozonation and chlorination are widely used disinfection processes in water treatment. In this review, the mechanisms and applications of three disinfection processes are introduced, and their inactivation effects on virus as well as other microorganisms are compared and discussed. The resistance of viruses to UV irradiation is generally stronger than that of bacteria. 4-log inactivation of bacteria can be easily obtained within a UV dose of 10 ​mJ/cm 2 . However, the doses to reach the same virus removal rate vary greatly from 10 to 140 ​mJ/cm 2 . The coronaviruses have even stronger UV resistance. Comparatively, ozonation and chlorination are effective methods to inactivate viruses, and the CT values of 4-log removal for most viruses concerned are lower than 1 ​mg·min/L and 10 ​mg·min/L, respectively. Protozoa, fungal spores and bacterial spores are more resistant to disinfection. Temperature, pH, organic matters, turbidity and other parameters all have influences on the disinfection. With a 10 ​°C decrease in temperature, the CT value required for certain removal rates doubles. Generally low pH promotes disinfection and high pH is against it. In drinking water and wastewater treatment process, the resistance properties of microorganisms and other influence parameters should be taken into consideration when choosing disinfection technologies.

A Review on the Potential of Common Disinfection Processes for the Removal of Virus from Wastewater

“…However, one of the main concerns in this area is the formation of harmful and carcinogenic disinfection by-products (Joo and Choi 2021 ). Chlorine mostly reacts with intracellular components and inactivates viral capsids by damaging them and destroying virus nucleic acids (Kong et al 2021 ). Chlorine elements, chloramines, sodium hypochlorite, chlorine dioxide, calcium hypochlorite, and chloroisocyanurates are the main sources of chlorine (Teymoorian et al 2021 ).…”

“…Chlorine elements, chloramines, sodium hypochlorite, chlorine dioxide, calcium hypochlorite, and chloroisocyanurates are the main sources of chlorine (Teymoorian et al 2021 ). Chlorine reacts with water to produce chloride ions and hypochlorous acid, which can be ionized further to produce hypochlorite (Kong et al 2021 ). Hypochlorous acid has chlorine disinfectant properties, and hypochlorite is a powerful oxidizer that effectively oxidizes organic contaminants (Kuzniewski 2021 ).…”

“…The most efficient way to inactivate viruses is to use chlorine as a hypochlorite ion or hypochlorous acid (Teymoorian et al 2021 ). However, hypochlorous acid is usually considered the main disinfectant (Kong et al 2021 ).…”

“…pH is a determining factor in the inactivation of viruses in wastewater, with low pH inactivation rates being higher than high pH inactivation rates (Singh et al 2021 ). However, because hypochlorous acid is a weak acid, the pH of the wastewater can have a significant impact on the ionization balance of the acid (Kong et al 2021 ). In addition, pH affects the disinfection efficiency of chlorine by determining the rate of dissociation of hypochlorous acid into hypochlorite ions (Singh et al 2021 ).…”

“…Turbidity, on the other hand, is influenced by effective composition. When humic acid is used to create turbidity, the disinfection efficiency of chlorine is significantly reduced when the turbidity reaches 1 NTU, but when chalk is used to create turbidity, the disinfection efficiency remains unchanged even at 5 NTU turbidity (Kong et al 2021 ). On the other hand, the efficiency of all chemical reactions is affected by temperature.…”