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Recommended Treatment Levels of Ozone For Particular Microbial Species

There is a two-step procedure for determining the recommended treatment levels of ozone. First, the grams of ozone that you need to produce to oxidize the grams of contaminants. The second is the disinfection calculation, measured in mg/l of ozone over a specific period. Inactivating a living organism requires concentration and time (Ct).


Concentration (ppm)



Algae (blue-green) 0.3 5.0 1.5
Bacteria (all species), recommended 0.1 1.0 0.1
Escherichia coli (E. coli) 0.04 1.0 0.04
coliphage MS2 0.2 0.5 0.1
Heterotrophic Bacteria HPC 0.2 0.5 0.1
Mycobacterium tuberculosis, leprae 0.01 6.0 0.06
Pseudomonas aeruginosa, fluorescens 0.01 0.1 0.01
Salmonella, all 0.01 0.1 0.01
Staphylococcus, sp, albus, aureus 0.01 0.1 0.01
Streptococcus, all 0.01 2.0 0.02
Fungus, Mold, Yeasts 0.3 5.0 1.5
Nematodes, all, recommended 1.0 5.0 5.0
Protozoa, all, recommended 1.5 5.0 7.5
Acanthamoeba & Naegleria 0.2 0.5 0.1
Amoeboe Trophozoites cysts 0.4 4.0 1.6
Cryptosporidium, recommended 1.5 5.0 7.5

By Jim Eagleton


  • The CT factor is the product of the ozone concentration (ppm) and the contact time (minutes). Essentially, the higher the CT factor, the more difficult the organism is to kill.
  • Amicrobial species with a CT factor of 0.01 for example will be killed by an ozone concentration of 0.01 mg/L for a contact time of 1 minute or an ozone concentration of 1.0 mg/L for 0.01 minutes, (0.6 seconds).

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