Note: The CT factor is the product of the ozone concentration and the contact time in minutes. Essentially, the higher the CT factor, the more difficult the organism is to kill. Note also that a microbial species with a CT factor of 0.01 for example will be killed by an ozone concentration of 0.01 mg/L end a contact time of 1.0 minutes, or an ozone concentration of 1.0 mg/L for 0.01 minutes, (0.6 seconds), e.g., the case with Staphylococcus aureus. – Similarly, 2.0 mg/L ozone, in the case of Staphylococcus will produce a CT factor of 0.01 in 0.005 minutes, or 0.30 seconds
Organism | mg/O3/L | Minutes | CT |
Algae (blue green) | 0.30 | 5.0 | 1.5 |
Bacteria (all species), recommended | 0.10 | 1.0 | 0.1 |
Aeromonas & Actinomycetes | yes | ||
Bacillus, all | yes | ||
Campylobacters | yes | ||
Clostridium Botulinum & others | yes | ||
Escherichia coli (E. coli) | 0.04 | 1.0 | 0.04 |
coliphage MS2 | 0.20 | 0.5 | 0.1 |
Flavobacterium | yes | ||
Helicobacter (pylori) | yes | ||
Heterotrophic Bacteria,- HPC | 0.20 | 0.5 | 0.1 |
Leqionella pneumophlia | yes | ||
Micrococcus, all | yes | ||
Mycobacterium tuberculosis, leprae | 0.01 | 6.0 | 0.06 |
Pseudomonas aeruginosa, fluorescens | 0.01 | 1.0 | 0.01 |
Salmonella, all | 0.01 | 1.0 | 0.01 |
Shigella shigellosis dysentery | yes | ||
Staphylococcus sp, albus, aureus | 0.01 | 1.0 | 0.01 |
Streptococcus all | 0.01 | 2.0 | 0.02 |
Vibrio: aiginolyticus, anguillarium | yes | ||
cholerae, comma, parahemolyticus | yes | ||
Yersinia enterocolitica | yes | ||
Fungus, Molds, Yeasts | 0.3 | 5.0 | 1.5 |
Mold Spores | 0.03-0.30 | ||
Nematodes, all, recommended | 1.0 | 5.0 | 5.0 |
Hook worm & etc. | 0.3 | ||
Protozoa. all, recommended | 7.5 | 5.0 | 0.1 |
Acanthamoeba & Naegleria | 0.2 | 0.5 | 1.6 |
Amoeboe Trophozoites cysts | 0.4 | 4.0 | 7.5 |
Cryptosporidium, recommended | 5.0 | ||
Cyclospora | yes | 4.0 | |
Entamoebea (histolytica) | yes | 2.5 | |
Giardia lamblia | 0.8 | 5.0 | |
Giardia muris | 0.50 | 5.0 | 2.5 |
Microsporidium | yes | 5.0 | |
N. gruberi | 0.50 | 5.0 | |
Trematodes, all, recommended | 1.0 | 5.0 | 1.6 |
Flat worms, flukes & etc. | 0.3 | 0.9 | |
VIRUS, all, recommended | 0.40 | 4.0 | |
Adenovirus, 7A | 0.30 | 3.0 | |
Astrovirus | yes | 1.2 | |
Calicivirus | yes | ||
Echovirus 5,12 & 29 | 0.40 | 4.0 | 1.2 |
Encephalomyocarditis | yes | 0.6 | |
Enterovirus, over 35 types | 0.30 | 4.0 | 1.2 |
coxsachie, B3 & B5 | 0.60 | 1.0 | |
poliovirus, 1, 2 & 3 | 0.30 | 4.0 | |
Hepatitis, A E & HAV | yes | ||
nonA and nonB | yes | ||
Myxovirus Influenza | yes | ||
Norwalk | yes | ||
Picobimavirus | yes | ||
Reovirus 3 types, | yes | ||
Rotavirus, 3 types | yes |
Information written for the Drinking Water Unit of EPA’s Region 10 by Jim Eagleton.