Ozone Disinfection

Spartan Environmental Technologies supplies ozone generators for ozone disinfection applications including drinking water, cooling water, process water, aquaculture, marine parks among many other applications.

Below you will find technical information on how ozone disinfects and how it compares to other commonly used disinfectants. If you are interested in specific organisms inactivated by ozone you can follow the link: micro organisms inactivated by ozone. We also have a link to fish pathogens inactivated by ozone.

How Ozone Disinfects?

Ozone functions as both an oxidant and disinfectant in the treatment of drinking (potable) water and wastewater. This is similar to chlorine. Chlorine and Ozone, however, operate by different mechanisms when disinfecting water. As a result, ozone and chlorine can act synergistically.

Ozone's germicidal properties are associated with its high oxidation potential. Disinfection by ozone is a direct result of bacterial cell wall disintegration, also known as lysis. This mechanism is different than that by chlorine. Although the exact chemical action of chlorine is not clear, it is believed that the chlorine residual in aqueous solution diffuses through the cell wall of the microorganisms and attacks the enzyme group which results in the destruction of the microorganism.

The graphics below illustrate the process while the photomicrograph show actual bacteria before and after ozonation:

Ozone Inactivation of Micro Organisms - Untreated
Ozone Inactivation of Micro Organisms - Cell Wall Damage by Ozone
Ozone Inactivation of Micro Organisms - With Ozone
Ozone Inactivation of Micro Organisms - Multiple Ozone Attacks on Cell
Ozone Inactivation of Micro Organisms - Ozone Attack Begins
Ozone Inactivation of Micro Organisms - Ozone Destroys Cell
Photo Micrograph of Actual Ozone Inactivation of Bacteria

Disinfection Power of Ozone

To demonstrate the disinfection power of ozone and compare it with other oxidizing agents, Morris developed the lethality coefficient:

Lethality Coefficient= 4.6/(Ct99) where:

C = residual concentration in mg/L t99 = time in minutes for 99 percent microorganism destruction (2-log destruction)

Morris, J.C., "Aspects of the Quantitative Assessment of Germicidal Efficiency," in Chap. 1, J.D. Johnson (ED.), Disinfection, Water and Wastewater, Ann Arbor Science, Ann Arbor, MI 1975.

The table below lists parameters for disinfection by ozone for different organisms:

Parameters for Disinfection by Ozone (pH 7; 10-15 degrees C):
Organism Lethality Coefficient (a) C 99:10 (b)
Escherichia 500 0.001
Streptococcus faecalis 300 0.0015
Polio virus 50 0.01
Endamoeba histolytica 5 0.1
Bacillus megatherium 15 0.03
Mycobacterium tuberculosam 100 0.005
a - Lethality Coefficient = 4.6/(Ct99)
b - C 99:10 = concentration in mg/liter for 99 percent destruction or inactivation in 10 minutes
(Morris considered these values to be valid within a factor of two)

Comparison of the values in this table with similar values obtained for chlorine is shown in the table below. These values tabulated by Morris illustrate that ozone is a more powerful germicide against all classes of organisms listed by factors of 10 to 100. The table shows values of the lethality coefficient:

Lethality Coefficient at 5 degrees C [(mg/liter)-1(min.)-1]
Agent Enteric Bacteria Amoebic cysts Viruses Spores
Ozone 500 0.5 <5 2
HOCl as Chlorine 20 0.05 >1 0.05
OCl- as Chlorine 0.2 0.0005 <0.02 <0.0005
NH2Cl as Chlorine 0.1 0.02 0.005 0.001
Another way of looking at disinfection is to employ the CT concept. This associates a concentration of ozone multiplied using the CT concept.