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UNDERSTANDING OZONE
What is ozone?
Ozone is a gas, which is formed naturally during a thunderstorm when lightning converts oxygen into ozone. The fresh sweet smell in the air after a storm is the smell of ozone. Ozone is generated when a high voltage electric discharge passes through the air. The oxygen molecules are converted to ozone, with three oxygen atoms instead of two.
What does ozone do?
Ozone is a very strong oxidant. When it comes into contact with micro-organisms such as bacteria and fungi, or with odour making particles, it oxidizes them.
This process is non-selective, which means that a given target such as legionellosis cannot develop an immunity or resistance to ozone.
Why is that important?
Because ozone is such an effective oxidant, it neutralizes all organic and inorganic material. This means that it kills viruses, bacteria, mould, mildew, fungus and germs. It can be used to kill impurities and odours in the air and water. In other words, ozone gas can clean the air and water as effectively, and often more effectively than any chemicals.
Why not just use chemicals?
When we use chemical sprays to clear the air of bacteria, or put chemicals into water to kill the germs, the chemicals leave a residue behind which is unhealthy for humans. When ozone is used to do the same thing, it leaves behind no chemical residues. It is also far more effective for killing odours than chemicals, because it actually kills the bacteria responsible for the smell, rather than just masking the smell with another.
Where can ozone be used?
Ozone can be used anywhere where germs and smells are unwanted, which is of course anywhere. It is used for sanitizing, deodorizing and making areas hygienic. It can be used domestically, in the home or office, commercially in hotels, restaurants and hospitals and industrially for water purification and sterilization in factories and agricultural warehouses.
Is ozone dangerous?
At high levels, ozone can be toxic for humans. However, ozone generators produce ozone at levels to kill micro-organisms, levels that are too low to be dangerous to humans. All our units conform to Guidance Note EH/38/96 of the UK Health and Safety Executive.
APPLICATION OF OZONE
Occurrence of Ozone
Ozone, 03, is a blue gas under normal conditions. Ozone is heavier than air or oxygen. At altitudes from 60 to 90 thousand feet ozone occurs naturally in concentrations from 10 to 20 parts per million by volume (ppm/v) (l). At ground level or sea level, however, it exists in a greatly diluted state and is present in minute quantities (.001 to .003ppm) as we breathe it.
Chemical and Physical Properties of Ozone
Ozone is one of the purest and most powerful oxidants and germicides known. Ozones reaction is rapid with most materials as it is unstable and readily decomposes to ordinary oxygen. This decomposition is very slow at ordinary temperatures but is accelerated by heat and moisture. The decomposition is almost instantaneous at temperatures of several hundred degrees F. Ozone is also decomposed photochemically by the action of sunlight. Ozone was first detected in 1785, but it was not until the 1800s that the first machine was constructed to generate ozone. The first commercially developed ozone generators were put to use in the early 1900s.
Generation of Ozone
The most practical technique of generating ozone is the conversion of oxygen to ozone in an electrical or corona discharge. Ultraviolet light also produces ozone, but the energy required is ten times that of the discharge technique for the same quantity of ozone.
Ozone generators produce ozone by passing dry air between two parallel or concentric electrodes separated by a dielectric. The oxygen in the air is broken down to charged oxygen atoms, some of which recombine to form molecules of ozone. Ultraviolet lamps with glass that transmits some radiation below 2000 Angstrom units, produce some ozone from the oxygen of the air. Such lamps exert a double bactericidal action by ultraviolet irradiation and liberation of ozone.
The corona discharge can take place in ambient air at atmospheric pressure, or in dried air under pressure. Ambient air equipment is not as efficient in operation as dried pressurized air equipment. Ambient air equipment produces low concentrations and small quantities of ozone in the air stream passing through the discharge. Ozonators operating on dry air and under pressure produce far greater quantities of ozone in much higher concentrations and at greater efficiency of operation. Both types of ozonator are used in commercial applications today. Each has its specialized area.
Existing commercial applications of ozone include:
Purification of drinking water,
Production of chemicals including synthetic fibres, jet lubricants and pharmaceuticals,
Treatment of industrial liquid wastes, such as cyanides and phenols,
Deodorization of sewage gases, rendering plant exhausts and exhausts from other industrial processes,
Deodorizing air in inhabited areas,
Food and plant preservation in cold storage,
Sterilization of containers for aseptic packaging
Ozone and its use in Food Preservation
The use of ozone in food preservation is not new. For example, the American Society of Heating, Refrigeration and Air Conditioning (ASHRAE), in its Application and Equipment Guides, cites ozones usefulness in cold storage warehouses, restaurants and supermarket coolers, and ships and trains among other places. The ozone concentrations normally used are below 3ppm/v. where prolonged storage is necessary and where prevention of spoilage, mould growth and transfer of odours between materials is desired. The principle of ozones usefulness in food preservation involves its ability to check, reduce and eliminate the bacteria causing the majority of the spoilage problems, as well as its power to oxidize odours.
Materials successfully stored in ozone atmospheres include eggs, vegetables, apples, cheeses, citrus and other fruits, nuts, poultry and meats. Most of the present day application information is based upon work done by A. W. Ewell.
Fruits:
By far the most frequently used area of ozone application is in fruit storage. Ozone concentrations normally recommended range from 1 to 3ppm/v. Several excellent papers on this topic have been presented by the U.S. Dept. of Agriculture. Ozone controls surface mould on packages and walls, and reduces scale developments and decay. As determined in the USDA tests, there is no difference in taste and other physiological properties between ozonized and non-ozonized apples.
In the work by Schoner of the USDA it was found that intermittent use of ozone would be satisfactory in preserving the quality of apples, preventing the growth of moulds and eliminating or reducing other spoilage. This has been shown in a State of Washington warehouse where ozone is used only during evening hours.
Ozone has been recommended for the use in the storage of apples and small fruits. Growth of surface moulds, the mould spore count in the air, germination of spores and infection of the fruit were reduced and offensive odours were destroyed. A concentration of 1 2ppm for a few hours a day was effective and not injurious to the fruit. Decay of apples that were already infected was not reduced by ozone.
Concentrations of 3.25ppm seemed to increase decay, causing pitting, and also caused a musty flavour to develop in apples of some varieties.
Other fruits, including strawberries, raspberries, currants, grapes, peaches and all types of nuts, can be stored in ozone atmospheres to reduce mould growth and extend the storage period. Fruits are kept fresh longer and losses during shipment are substantially reduced. In fact, some experiments show that the pleasant aroma from these fruits is even enhanced.
Egg storage:
The storage of eggs in large commercial warehouses calls for protective measures to prevent decay of the egg material. In egg storage the presence of high humidity is necessary to reduce shrinkage caused by loss of moisture through the permeable egg shell. Further, the high humidity necessary to prevent this is conducive to mould growth. However, eggs stored in ozone atmospheres at a 90% humidity and 31 degrees F. temperature for up to 8 months are free of mould growth and indistinguishable from fresh eggs, raw or cooked. The recommended dosage to accomplish this is 1 to 2ppm.
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