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THIS INFORMATION IS IN NO PARTICULAR ORDER Ozone is a form of elemental oxygen. In its most stable form, elemental oxygen exists as diatomic molecules (O2). The molecules of ozone contain three oxygen atoms (O3) and are unstable with respect to O2. Ozone is a very reactive gas, and even at low concentrations it is irritating and toxic. It occurs naturally in small amounts in the Earth's upper atmosphere, and in the air of the lower atmosphere after a lightning storm. At room temperature, ozone is a pale blue gas with a sharp odor, characteristic of the air after a thunderstorm or near an old electric motor. It condenses to a dark blue liquid at 112°C and freezes at 193°C. Ozone is much more reactive than O2. It is a very powerful oxidizing agent, second among elements only to fluorine. It can oxidize many organic compounds and is used commercially as a bleach for waxes, oils, and textiles, and as a deodorizing agent. Because it is a powerful germicide, it is also used to sterilize air and drinking water. Disinfection by triatomic oxygen (ozone) occurs through the rupture of the cell wall. This is a more efficient method than chlorine which depends upon diffusion into the cell protoplasm and inactivation of the enzymes. An ozone Level of 0.04 ppm for 4 minutes has been shown to kill any bacteria, virus, mold and fungus. Ozone oxidizes the transition metals to their higher oxidation state in which they usually form less soluble oxides that are then easy to separate by filtration. Iron, for example, is usually in the ferrous state when dissolved in water. With ozone it yields ferric iron which is further oxidized in water to ferrum hydroxide; a molecule that is very insoluble and precipitates out. Other metals such as Arsenic (in the presence of Iron), Cadmium, Chromium, Cobalt, Copper, Lead, Manganese, Nickel, and Zinc can be treated in a similar way. At Ozone levels above 4 ppm however, Manganese will form soluble permanganate, showing up as a pink color. Surface waters are generally colored by natural organic materials such as humid, fulvic and tannic acids. These compounds result from the decay of vegetative materials and are generally related to condensation products of phenol-like compounds. They have conjugated carbon double bonds. When the series of double bonds extend upwards of twenty, the color absorption shows up in the visible spectrum. Ozone is attracted to breaking organic double bonds. As more of these double bonds are eliminated, the color disappears. Surface water can usually be decolorized when treated with 2 to 4 ppm of ozone. Ozone destroys all odors that are present. it does not merely mask them. The eradication of odors is impossible when air is circulated only, or when oxygen is used. This fact has been proven in cold storage warehouses, where all kinds and any food products are stored. Odors are not present regardless of how strong they might be, or where they may originate, even if only low concentrations of ozone is used The use of ozone for decades in water purification was mainly due to its toxic effects on micro-organisms found in water, effects which exceed those of any other disinfectant. Experience has demonstrated that it destroys with extreme efficiency the spores of molds, amoebae, and viruses and bacteria as well as various pathogenic and saprophytic germs. These micro-organisms represent a wide variety of species, genera and families. Therefore, organisms were to be selected for further investigations, which would best represent typical pathogenic effects on humans and animals. It was similarly the long and successful use of ozone that created interest in its utilization as a general germicide and sterilizing age and for highlighting its advantages over the other germicides used generally for water purification, primarily chlorine. Special importance can be attached to investigations relating to the specific destructive power of ozone on selected bacteria, including quantitative data and the mechanism of sterilizing and germicidal effects. As is known, bacteria are microscopically small, single-cell creatures having a primitive structure, and they take up foodstuffs from and release metabolic products to the exterior and multiply by division. The bacteria body is sealed off towards the exterior by a relatively solid cell membrane. Most tastes and odors in water supplies come from naturally occurring or man-made organic material contamination. Bacterial decomposition of humid material imparts taste to surface waters. The action of algae and actinomycetes gives rise to objectionable tastes. Chlorination of humid material leads to chlorophenols that are of far stronger odor and more antagonistic to the taste than the original phenol and unreacted chlorine. Most of these odors are removed with ozone treatment. Even some sulfur compounds such as hydrogen sulfide, mercaptans or organic sulfides can be oxidized to sulfates with ozone. Their vital processes are controlled by a complex enzymatic system to which macromolecular organic compounds, frequently containing phosphorus or sulfur contribute. Viruses are extremely small, independent particles, built up by crystals and macromolecules. Unlike bacteria they multiply only within the host cell. They transform the protein of the host cell, to a certain extent auto catalytically, in proteins of their own. Germicides and sterilizing agents interfere with the metabolism of bacterium-cells, most likely through inhibiting of blocking the operation of the enzymatic control system. A sufficient amount of oxidizing agent breaks through the cell membrane and this leads to the destruction of the bacteria or virus. The free electrical charge of the cell membrane constitutes in most cases a strong obstacle for the effective operation of the disinfectant. Chlorine is known to enter into reaction with water and the reaction products generated will have a distribution depending on the pH of the water. Free chlorine and undissociated HOCl can penetrate relatively easily into the bacterium cell; penetration, however, is not so easy for the negative OCl (Hypo chlorite) ion. Therefore, it is more difficult for chlorine to kill germs in an alkaline solution. Germicides and sterilizing agents interfere with the metabolism of bacterium-cells, most likely through inhibiting of blocking the operation of the enzymatic control system. The destruction rate of germs depends in general, on the concentration, the number of bacteria in unit volume and on the pH of the medium. The process of necrosis of bacterium cells and the contribution of the penetration of germicides throughout the cell membrane and the part played by the various reactions taking place in metabolism have not been fully explored yet. On the basis of considerations referred to above, and bearing in mind that ozone does not react with water, it can be assumed that the free electrical charge of the cells does not reduce the effect. Holluta and Unger showed that the destruction rate of germs has no measurable dependence on pH. This fact constitutes one of the major advantages of ozone over other disinfectants. Measurements carried out by Fetner and Ingols indicated the need for higher ozone concentrations and longer exposure times under approximately identical conditions. Deviations can probably be contributed to changes in the technique used for the analysis and to the differences between experimental conditions. The curve for chlorine is logarithmic, however, the effect of ozone below a certain critical concentration value is small, of zero, but practically all germs above this level are destroyed. This effect is called "all or none response" and the critical concentration is referred to as "flash point". The critical concentration lies just at the level, generally between 0.4 and 0.5 mg dm that produces a small amount of residual ozone in water. Several research workers in case of the viruses of influenza and polio, certain coliform bacteria and the spores of clostridium botulinum observed the threshold value of 0.4 to 0.5 mg/dm3. For water purification it is the residual concentration which is the critical factor in controlling the destruction of micro-organisms. At the beginning of the 1960’s it was unanimously established that ozone solutions, particularly various unpleasant smells and body odor, cigarette smoke, etc., can be eliminated in practice by treatment with a small amount of ozone.
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