Ozone (O3,  allotropic oxygen)is an unstable gas composed of three oxygen atoms, it is produced mainly by subjecting oxygen to electrical discharges, ultraviolet radiation and also some chemical processes.

At room temperature, ozone is a colorless gas, sharp and penetrating odour. The olfactory threshold of perceptibility for humans is at concentrations between 0.02 and 0.05 ppm, equivalent to about 1 / 20 of the threshold concentration for a defined safe exposure time of 15 minutes and about ¼ of the safe threshold of exposure defined in the environments work.

State of training (corona effect), ozone appears violet, shown considerable instability and tends to decompose rapidly with increasing temperature. For the above reasons, ozone must always be produced on the place of use could not be stored in a gaseous state that for very short periods.

Ozone is a strong oxidizing agent that can react with organic substances with double bond (unsaturated) and this feature has been readily used in many processes for treating water and air. Its effect bactericide, fungicide and inactivating of the virus has been known for a long time (Sonntag, 1890).

Since 1906 there is in Nice the first municipal water purification plant with ozone. Currently, large cities such as Amsterdam, Moscow, Paris, Turin, Florence, Bologna and Ferrara have facilities that provide drinking water taken from rivers and treated with ozone. The advantage of ozone on the products who develop free chlorine, which are often used for water purification, is that the first sterilization is much better against bacteria viruses; also ozone does not alter the characteristics of the water in particular flavor (Viebahn, 1977), and produces fewer harmful by products.

A validation of the absolute compatibility of ozone, in the right measures, with human activities, from 26 June 2001, the FDA allows the use of ozone also in the food production process. Ozone is used for disinfection of bottled water since 1982 and from 1984 all the swimming pools of the Olympic Games must be purified with ozone. In July 1996, Protocol 24482, the Ministry of Health has approved ozone as "PRESIDIO FOR STERILIZATION OF NATURAL ENVIRONMENTS.

PHYSICAL AND CHEMICAL PROPERTIES OF OZONE

The solubility of ozone in water is higher than that of oxygen and is dependent on temperature and the concentration of ozone in gas phase.

Ozone is an unstable gas and therefore it is important to know the time of decomposition. For ozone in solution the half-life (time required to halve the concentration) depend on many factors. In particular, we can highlight the dependence on pH (T = 21 ° C, D = 1 bar):

• At pH = 6.0, about 20 minutes

• At pH = 7.0, about 15 minutes

• At pH = 8.0, about 5 minutes

Under standard conditions.

Also the temperature dependence is significant. At pH = 7:

• T = 15 ° C, about 30 minutes

• T = 20 ° C, about 20 minutes

• T = 25 ° C, about 15 minutes

• T = 30 ° C, about 12 minutes

Gas-phase decomposition is much slower in theory:

• at T = - 50 ° C, about 90 days

• at T =- 35 ° C, about 8 days

• at T =- 25 ° C, about 18 days

•     T = 20 ° C, about 3 days

•     T = 120 ° C, approximately 1.5 hours

•     T = 250 ° C, 1.5 seconds

In practice, the decomposition is usually much faster because of the influence of parameters such as humidity, presence of nouns organics, the presence of catalytic decomposition.

EXPOSURE TIME FOR DIFFERENT CONCENTRATIONS IN THE AIR AND THE HUMAN CONSEQUENCES

Due to the high oxidizing power, ozone gas phase at high concentrations can be dangerous to health, particularly with regard to the respiratory rways.

The maximum allowable concentration for work environments with exposure 8 h / g - 5 days / week is equivalent to 0.1 ppm. A concentration of 1 ppm can be tolerated for short exposures (eg 15 '). Concentrations of 100-1000 ppm can be fatal even in a short time.
In any case the sensitivity to ozone depends greatly on the individual and environmental parameters, primarily temperature. It is recommended to use particular caution in high temperature environments.
The following graph illustrates the effects of ozone on human health in different concentrations and different contact times.

 

Less risk is associated with skin exposure to ozone in solution, because in this case the concentrations are normally very low. In situations where people are exposed to water containing ozone (eg swimming pools), usually the main concern remains the possibility of accumulation in the above phenomena due to degassing

PROPERTIES OF OZONE IN WATER DISINFECTANTS

Ozone, due to its high oxidizing power, is capable of damaging cell walls and to break the large macromolecular components that underpin the integrity of viable bacterial cells, fungi, protozoa and viruses. That's potent broad-spectrum disinfectant action is used both in the disinfection of water, water purification, and the treatment of wastewater.
Comparison of overall effects of disinfectants using drinking.

+ + + + + + excellent + good + + + moderately weak - non-existent.

Below are listed the times given for the elimination of different families of pathogens:

DISINFECTANT AND DEODORANT POWER IN THE AIR

Several researchers describe the bactericidal effect, bacteriostatic, and deodorant found:

• Wagner and Harvard: positive concentration of 0:04 to 0:06 ppm vol.

• Ewell: positive at concentrations of 0.1 - 0.2 ppm vol.

• Elford and Van den Ende: positive on Streptococcus salivarius spray on glass plate at a concentration of 0.04 ppm vol.

• Bruni and Pernice: positive on Serratia mercescens

• Nagy positive bacteria and molds to 0.1 ppm vol.

• Summer: inhibits the growth of fungi

• Ceccacci: positive at concentrations harmful to humans

• Watson: positive elimination of odours from the human body to 0015 ppm vol. or other foodstuffs and tobacco smoke.

• Bisbino: positive in the neutralization of odours from organic substances to 0.03 ppm vol.

• Durres: positive in the elimination of odours from the human body in military dormitories 0:01 to 0:02 ppm vol.

• Scassellati - Sforzolini: it destroys the carbon monoxide in the garage from 53% to 67% at concentrations of less than 0.05 ppm vol.

APPLICATIONS

Ozone finds many uses in industrial and civil. The following list is only indicative

and more information are available by contacting us directly. 

WATER TREATMENT

• discoloration / sterilization / deodorization waste

• surface treatment (removal surfactants)

Open "Ozone Relation"