UV inactivation of pathogenic and indicator microorganisms

Area of Science:

• Microbiology
• Environmental Science
• Public Health

Background:

• Disinfection is crucial for water treatment to eliminate pathogenic microorganisms.
• Ultraviolet (UV) light is a non-thermal disinfection method used in water purification.
• Different microorganisms exhibit varying resistance to disinfection agents.

Purpose of the Study:

• To determine the UV light doses required for inactivating various microorganisms.
• To compare the UV disinfection efficacy across different microbial types.
• To assess the relative resistance of bacteria, viruses, spores, and cysts to UV light.

Main Methods:

• Survival of Escherichia coli, Salmonella typhi, Shigella sonnei, Streptococcus faecalis, Staphylococcus aureus, Bacillus subtilis spores, poliovirus type 1, simian rotavirus SA11, Acanthamoeba castellanii cysts, total coliforms, and standard plate count microorganisms was measured.
• Doses of germicidal UV light were applied to achieve 99.9% inactivation.
• UV dose requirements were compared across the tested microbial groups.

Main Results:

• Comparable UV doses were needed for 99.9% inactivation of vegetative bacteria, total coliforms, and standard plate count microorganisms.
• Viruses required 3-4 times the UV dose needed for E. coli.
• Bacterial spores and amoebic cysts required 9 times and 15 times, respectively, the UV dose for E. coli.

Conclusions:

• UV disinfection efficacy varies significantly among different types of microorganisms.
• Bacterial spores and protozoan cysts are more resistant to UV inactivation than vegetative bacteria and viruses.
• UV disinfection offers a potentially narrower relative dose range compared to chlorine for inactivating diverse waterborne pathogens.