What is Ozone?

What is ozone?

Ozone is an allotrope of oxygen.

What's an allotrope of oxygen?

Allotrope means; "another form". Put correctly, ozone is triatomic oxygen. An ozone molecule, O3, contains three atoms of oxygen. A highly unstable molecule with a very short half-life (22 minutes on average), it prefers to revert back to its more stable state, O2. In order to return to that diatomic state, O2, it must release one atom of oxygen. Ozone’s desire to release a lone molecule of oxygen is referred to by chemists as its power to oxidize. This natural oxidizing tendency is what makes it such an attractive industrial disinfectant.

Why is ozone such a strong industrial disinfectant?

The unpaired oxygen atom that ozone releases will attach itself to other compounds in water, thus, oxidizing them into different compounds. That single oxygen atom will oxidize virtually all organic and many inorganic compounds. Once oxidized, they will proceed to precipitate out of the water.

Because ozone will break down, oxidize, almost anything that it contacts, it is an enormously powerful disinfectant and oxidizer. In fact, ozone is 150% stronger in terms of oxidation potential than chlorine, and is the second strongest, commercially available chemical in the water treatment industry, after the hydroxyl free radical. Ozone kills organisms and viruses by cell lysis, the rupturing of a cell’s wall, a process, according to the EPA, “to which microorganisms cannot develop immunity.” On the other had, some parasitic species have shown resistance to low doses of chlorine, including, ococysts of Cryptosporidium parvum, cysts of Endamoeba histolytica and Giardia Lamblia, and eggs of parasitc worms. By contrast, “residual ozone concentrations of as little as 0.1 mg/L will reduce populations of Legionella pneumophilia in cooling towers to 80%.

Why do we use ozone?

We use ozone because it is a safe and environmentally friendly tool for treating and disinfecting water. Because it is such a powerful oxidizer, little else is needed to clean condenser water, chilled water, cooling towers, tube bundles, and pipes. Compared to the cost of storage and labor required to apply chemical, not to mention the danger, ozone is a comparatively cheaper alternative.

Its exceptional oxidizing power aside, one of the strongest motors propelling ozone’s increased use is the fact that it’s use does not harm our planet like chlorine does. Chlorine is a carcinogen, that is, it causes cancer, whereas, ozone is not a carcinogen. In fact, chlorine’s carcinogenic presence in our drinking water is, according to the EPA, one of the largest causes of cancer in America. Chlorine became so popular years ago because of its ability to disperse itself across nearly 100% of a body of water, and, therefore, kill many microorganisms. This same ability to diffuse so completely makes it nearly impossible to remove, meaning that blowdown or discharge water from a chlorine treated cooling tower or wastewater plant still contains chlorine when it returns to the environment where it continues to kill organisms in our ecosystems and bio-accumulate in fish and mammals: from shrimp to salmon to bears, etc. and eventually in human beings. In fact, chlorine and organochlorines have even managed to contaminate arctic mammas like reindeer that live thousands of miles from the nearest chlorine treated water plant. Chlorine persists in our environment, where, ironically it is not even found naturally. Ozone on the other hand is nature’s disinfectant. Pure oxygen is its sole ingredient, and when its done disinfecting it reverts back into pure oxygen, on average after only 22 minutes. In other words, there is no harmful residual. It is the environmental and responsible alternative.

Is Ozone Generation a brand-new technology?

No. In fact, it is quite old. Wener von Siemens, a German and a co-founder of the modern-day technology giant Siemens AG, discovered a method or producing ozone artificially in the 19th century. His technique led to the first use of ozone disinfection in water treatment in 1906. Given its superior strength and effectiveness as an oxidant, virucide, and biocide, ozone has become one of the dominant water treatment technologies in Europe. Its popularity and use is increasing in America as Americans become increasingly cognizant of its superior disinfecting and oxidizing power and of the malicious effects of chlorine on public health, the environment, and air quality. Extensive research into the generation of ozone has produced an array of viable systems, many producing large quantities of ozone gas for injection into water. It’s use has become so widespread that today it treats the water in the world’s largest aquarium in Hualien, Taiwan and the drinking water for the city of Los Angeles.


Ozone (O3) is the triatomic, allotropic form of oxygen (O). It is an unstable gas with a pungent odor.
Since ozone is unstable, it must be generated at the point of application.

The ozone molecule, having a molecular weight of 48, is made up of three oxygen atoms bound by equal oxygen-oxygen bonds at an obtuse angle of 116°49'. This structure is inherently unstable and is the reason for ozone's powerful oxidizing ability. Ozone has approximately 150% the oxidizing potential of chlorine. The physical properties of ozone and comparative oxidizing potentials for other chemical oxidants are presented in Table 1 and Table 2, respectively.


Molecular Weight 48.0
Boiling Point, °Celsius 111.9
Melting Point, °Celsius -193
Gas Density, 0°C grams/liter 2.144
Critical Temperature, °C -12.1
Critical Pressure, atm 54.6
Critical volume, cm3/mole 111


Flourine (F2) 2.87
Ozone (O3) 2.07
Hydrogen Peroxide (H2O2) 1.78
Potassium Permanganate (KMnO4) 1.70
Hypobromous Acid (HOBr) 1.59
Hypochlorous Acid (HOCl) 1.49
Chlorine (Cl2) 1.36
Chlorine Dioxide (ClO2) 1.27
Oxygen (O2) 1.23
Chromic Acid (H2Cr2O4) 1.21
Bromine (Br2) 1.09
Nitric Acid (HNO3) 0.94
Iodine (I2) 0.54

1. Unites States Environmental Protection Agency, April 1999, EPA Guidance Manual: Alternative Disinfectants and Oxidantshttp://www.epa.gov/safewater/mdbp/alternative_disinfectants_guidance.pdf

2. Strategic Environmental Research and Development Program, February 1995, Ozone Treatment for Cooling Towers — New Energy and Water Saving Technology for Reducing Cooling Tower Operating Costs, US Department of Energy. http://www.eere.energy.gov/femp/prodtech/pdfs/FTA_OTCT.pdf

3. United States Environmental Protection Agency, September 1999, Wastwater Technology Fact Sheet: Chlorine Disinfection. http://www.epa.gov/owm/mtb/decent/download/chlorine.pdf

4. Strategic Environmental Research and Development Program, February 1995, Ozone Treatment for Cooling Towers — New Energy and Water Saving Technology for Reducing Cooling Tower Operating Costs

At Finnegan-Reztek our mission is to reliably provide environmentally responsible water treatment solutions to our customers at a fair rate.

It is our desire that relationships that we create with our customers will not end after we render our services but continue on for many years in a manner that is both profitable to us and our clients.

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