Data summarized from the US EPA Workshop on UV Disinfection of Drinking ... Under the U.S. Safe Drinking Water Act, the US EPA is developing regulations.
Disinfection of Drinking Water with Ultraviolet Light Jackie Leinberger, P.Eng. Trojan Technologies Inc.
“Millions of people will die each year from dirty water and water-related diseases.” Chairman of the World Commission on Water for the 21st Century
“Water, this most precious commodity, is in peril in virtually all parts of the globe.”
Marq De Villiers
Pathogenic bacteria, viruses and protozoa in un-disinfected water and wastewater represent potential risks to Public Health Bacteria (E.coli)
Viruses
Protozoa
Protozoa
(Hepatitis, Polio)
(Giardia)
(Cryptosporidium)
UV Disinfection Theory
How UV Works D DN NA A
A
A
C T
T
G
A
C T
=
C
G T
G
A
A C T
G
T
G
T
C
=
T T
A
C
A
A
G
G
A C
UV light alters D N A des troying harmful bacteria and virus es
Bacterium Structure Cytoplasmic Membrane
Cell Wall
(DNA) Nucleic Acid
Classes of Microorganisms: The Microbial World Viruses: smallest (0.02-0.3 µm diameter); Rotavirus Bacteria: 0.5-2.0 µm diameter; E.coli Protozoa: most >2 µm - 2 mm; Bacteria no cell wall; wide range of sizes and shapes; Giardia, Cryposporidium and microsporidia. C. parvum oocyst
~5 um
UV Disinfection Effectiveness
Cryptosporidium Giardia
Least resistant
vegetative bacteria
viruses / spores
Most resistant
UV is effective for Cryptosporidium and Giardia control
UV Dose UV Dose = UV Intensity x Exposure Time (Units are measured in mJ/cm2) Microbe inactivation is directly related to UV Dose
UV Inactivation of Pathogens Pathogen
2
Average UV Dose (mJ/cm ) Required to Inactivate 1log
