Ozone is a colorless gas that occurs naturally in the atmosphere. It is particularly reactive and relatively unstable. The ozone molecule contains three oxygen atoms whereas the oxygen molecule contains only two. Ozone is normally made from oxygen, either from oxygen in the air or from high purity oxygen gas or mixtures thereof, and it reverts to oxygen upon decomposition.

Formation
The formation of ozone from oxygen requires an input of energy into the oxygen molecule by some method. This process is achieved by an electric discharge field as in the corona discharge (CD type) ozone generators or by ultraviolet (UV) radiation as in UV type ozone generators or as occurs in nature in the upper atmosphere by natural UV radiation. Ozone also may be made through electrolytic and chemical reactions.

Ozone in Nature
The ozone layer of the upper atmosphere at the altitude of 20,000 - 30,000 meters forms a natural barrier to protect all living species on earth from the harmful and powerful ultraviolet radiation of the sun. The beneficial effect of the ozone layer is considered to be so important that the manufacture and use of certain chemicals, such as chlorofluoro-carbon spray can propellants, are prohibited in some countries. When discharged into the air, these chemicals find their way to the upper atmosphere and destroy or diminish the ozone layer. For this reason, an international effort is underway to limit the production of chlorofluoro-carbon propellants worldwide.

In the atmosphere at ground level ozone is formed by the reaction of hydrocarbon pollutants in the air and atmospheric oxygen under the influence of sunlight. The amount of ozone so produced serves to indicate the extent of hydrocarbon pollution or smog in the air.

Common Applications

Ozone is a very powerful chemical oxidizing agent and a very powerful disinfectant. It has the unique feature of decomposing to a harmless, nontoxic, environmentally safe material being oxygen. These characteristics make ozone exceptionally suitable for the treatment of drinking water, wastewater and for the disinfections of high purity de-ionized water used in the pharmaceutical industry and in the manufacturing of integrated circuits in the electronics industry.

Ozone for Drinking Water
In municipal drinking water treatment, at least thirteen hundred water treatment plants throughout the world utilize ozone to produce a high quality of drinking water for the population of such cities as Los Angeles, Dallas, Montreal, Paris, Zurich, Dusseldorf, Budapest, and Moscow etc. Ozone is used in these plants to remove taste and odour, turbidity, iron and manganese, to oxidize dissolved organic pollutants and to disinfect the water.

Wastewater Applications
In wastewater treatment, ozone can be used to oxidize and destroy certain organic pollutants, such as phenols, cyanides etc. to increase the biodegradability of long lasting pollutants or to disinfect the wastewater already treated by other methods, such as biological oxidation in a conventional sewage treatment plant.

Industrial and Medical Uses
In the chemical industry, ozone is used to produce industrial chemical and chemical intermediates. There are many other widely varying uses of zone in the textile, pharmaceutical, pulp and paper, specialty chemicals and plastics industries as well as swimming pools, cooling towers, marine aquariums etc.. In some countries, ozone is also used for the treatment of certain diseases such as circulatory disorders, gangrene etc.