What Is Ozone?
That specific fresh scent after a thunderstorm.
Ozone is a molecule that consists of three negatively charged oxygen atoms and is sometimes known as “activated oxygen” or “triatomic oxygen”. The ozone molecule is very unstable and has a short half-life, causing it to fall back into its original form of oxygen after a short while. This makes ozone a very environmentally friendly oxidant.
Principally, an ozone molecule is nothing but an oxygen molecule that has received an extra oxygen atom by electric high voltage. Ozone is naturally produced through certain types of chemical reactions; the most commonly known example is the ozone layer, in which ozone is produced by ultra violet rays. Ozone is also formed during thunderstorms as a result of the high voltages that are involved.
When Was Ozone First Used?
Ozone’s ability to disinfect polluted water was first realized in Europe in 1886 and in 1906, France commissions the first municipal ozone drinking water plant in Nice.
How Is Ozone Created?
Ozone is created in basically two ways, Ultra Violet (UV) or corona discharge. Ultra-violet (UV) light creates ozone when a wavelength at 254 nm (nanometers) hits an oxygen atom. With corona discharge there are also two common ways of creating ozone. The first is to use glass tubes as a dielectric through which high voltage is passed. The tubes are put inside a chamber and oxygen is passed between it and the dielectric. The high voltage from the tubes grounds out to the chamber wall and the resulting spark breaks apart the oxygen atoms, creating ozone. The other way is to use a sealed aluminum cell in with high voltage contacts inside. As before, oxygen is fed through the cell and as the high voltage spark from the contacts grounds out inside the cell, ozone is formed.
How Does Ozone Work?
Ozone is one of the strongest known oxidants. It can be used to technically burn dissolved compounds (oxidation). The extra oxygen radical in an ozone molecule quickly binds to each component that comes in contact with ozone molecules. This is because of the instability of ozone and its inclination to return to its original form (O2). Both organic and inorganic substances may be oxidized by ozone (oxidation), but also microorganisms such as viruses, bacteria and fungi (disinfection). This causes the extra oxygen radical to be released from the ozone molecule and to bind to other materials, so that only pure and stable oxygen molecules (O2) are left.
How Well Does Ozone Disinfect?
Ozone is a very strong, broad spectrum disinfectant that is widely used in Europe. It is an effective method to inactivate harmful protozoa that form cysts. It also works well against almost all other pathogens in water as well as air.
Ozone kills bacteria 3,000 times faster than traditional chemicals such as chlorine and bromine without the potentially harmful byproducts and can do so using a fraction of the concentrations.
Ozone is also able to dissolve in water 13 times faster than standard chemicals.
The U.S. Food and Drug Administration has accepted ozone as being safe; and it is applied as an anti-microbiological agent for the treatment, storage, and processing of foods. http://www.fda.gov/OHRMS/DOCKETS/98fr/062601a.htm .
How Long Does Ozone Last?
Ozone, because of its makeup, is inherently unstable due to the weak bond with the third oxygen atom. The third atom is extremely reactive with anything it comes into contact with as it tries to return to its original state.
In air, ozone can have a half life of anywhere from 3 months at -50°c to 1.5 sec at 250°c. As with in air, ozone’s half life is greatly affected based on temperature when dissolved in water, from 30min at 15°c to 8min at 35°c. When in water, pH also plays a part in ozone’s life span, the higher the pH the shorter the half life.
What Is Half-Life?
Half-life is the length of time it takes ozone to dissipate. If the half life of ozone in water is about 30 minutes, it means that every half hour the ozone concentration will be reduced to half its initial concentration. For example, when you have 8 g/l, the concentration reduces every 30 minutes as follows: 8; 4; 2; 1; etc
What Are Safe Exposure Levels of Ozone?
Occupational Safety and Health Administration.
The maximum permissible exposure to airborne concentrations of ozone not in excess of 0.1 mg/L (by volume) averaged over an eight hour work shift.
American National Standards Institute/American Society for testing Materials (ANSI/ASTM). Control occupational exposure such that the worker will not be exposed to ozone concentrations in excess of a time weighted average of 0.1 mg/L (by volume) for eight hours or more per workday, and that no worker be exposed to a ceiling concentration of ozone in excess of 0.3 mg/L 9by volume) for more than ten minutes.
MSDS Information
CCOHS Information
US Department of Labor
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