Ozone / Ozone Information
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Ozone Information Ozone is a naturally occurring gas created from oxygen atoms. The oxygen molecule is made up of 2 oxygen atoms. These oxygen molecules are broken into atoms by the corona discharge during lightning storms or by UV light from the Sun. Single oxygen atoms cannot exist alone without regrouping back into di-atomic oxygen molecules. During this recombination stage some atoms will regroup into loosely-bonded tri-atomic oxygen. This new molecule is called Ozone, as seen to the right (d = 1.28, Theta= 116.5). Due to the loose bond in this oxygen molecule, ozone is a very strong oxidant and an ideal chemical-free purification and a disinfecting agent. Ozone is frequently misdiagnosed and equated to low-altitude pollution. Nothing could be farther from the truth. In fact, Ozone breaks down pollutants and should be welcomed when found in the air. The most effective way to produce Ozone commercially is through the use of pulse injected corona discharge. |
| Removal of Algae from Water with Ozone In a study done at the Mount Valerien plant in the suburb of Paris the following results were obtained: 1. Pre-ozonation of the raw water with 1.6 ppm of Ozone resulted in 83% removal of Algae. When 2.1 ppm of Ozone was applied, the removal rate was lower. 2. The combination of pre-ozonation and coagulation flocculation settling procedure improves the removal of Algae to 98.4%. The ozone dosage was 1.6 ppm, and the coagulant was 70 mg/l of Aqualenc (Aluminum salt). 3. With added filtration, 99.8% of Algae was removed. This effect is similar to the removal of turbidity. Secondary ozonation after the filtration is most beneficial for final sanitation. 4. When followed with Granular Activated Charcoal (GAC) filtration, better than 99.99% algae removal was achieved. 6. It has been observed that if the coagulant is held at 50 ppm, and the pre-ozonation dosage is increased to 2.6 ppm, the Algae removal will also be maximized. 7. The following Algae are more resistant and traces may still be found in the water after Ozone and GAC: Chlorophycae Chlamydomonas
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Improved Coagulation Oxidation of dissolved Organic materials with Ozone results in polar and charged molecules that can react with Polyvalent Aluminum or Calcium to form precipitates. Treatment of surface water with up to 0.5 ppm of Ozone results in a decrease in turbidity, improved settleability, and a reduction in the number of particles. This treatment, referred to as pre-ozonation, destabilizes the colloid with a resulting reduction in the amount of coagulant needed to produce a clear filtrate. |
Color Removal Surface waters are generally colored by natural organic materials such as humic, 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/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 usualy be decolorized when treated with 2 to 4 ppm of Ozone. |
Removal of Heavy Metals 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 Ferric 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. |
Ozone Vs. Chlorine When comparing disinfection efficiency, Ozone is 25 x more effective than Hypochlorous acid (HOCl), 2,500 x better than Hypochlorite (OCl) and 5,000 x more than Chloramine (NH2Cl). These results are measured from the comparison of CT constants ? the Concentration x Time needed to kill 99.99% of all micro-organisms. Chlorine reacts with organic materials to form organics containing Chlorine such as Chloroform, Carbon Tetrachloride, Chloromethane and others, generally known as Trihalomethanes (THMs). Ozone reacts with Organics to break them down into simpler compounds. These organics (Oxalic Acid for example) do not readily break down all the way to Carbon Dioxide with just Ozone, but if subjected to bacterial degradation on activated charcoal, they will be removed. This water can be later treated with a low level of Chlorine, say 0.2-0.3 ppm, to maintain sanitation in the distribution system. This way no THMs will be formed. THMs have been implicated as carcinogens in the development of Kidney, Bladder and Colon Cancer. The regulatory authorities are again decreasing the allowable levels of THMs in Community water systems. At the present time the limit is 0.05 ppm. Based on the scientific research, the level will be most likely soon be lowered to 0.01 ppm. Ozone does not react significantly with THMs as they are more resistant to oxidation - it takes a very long time to achieve full oxidation. Some THMs are removed as a result of physical sparging by the aeration action of the ozone/air mixture. |
Ozone Reactions to Organics Ozone reacts rapidly with most simple aromatic compounds and unsaturated aliphatics, such as Vinyl Chloride, 1,1-dichloroethylene, trichloroethylene, p-dichlorobenzene. Benzene, etc. But it reacts slowly with complex aromatics and saturated aliphatics. Ozone will degrade many organic compounds, such as sugars, phenols, alcohols, and as it degrades these materials it turns again into Oxygen. Coupling Ozone with Hydrogen Peroxide will cause the formation of very active Hydroxyl ions which initiate a nucleophilic attack on organic compounds. This can result in the displacement of Halogens and other functional groups such as Amines, Sulfides. |
| Ozone Solubility The solubility of Ozone depends on the water temperature and the Ozone concentration in the gas phase:
If oxidable chemicals are present in the water, larger amounts of Ozone will dissolve to satisfy the demand. One limiting factor is the efficiency of the mass transfer device used. When using Venturi more turbulence and smaller bubbles facilitate better mass transfer. When using Bubble Diffusers, the water column should be at least 16 ft. high. Higher concentrations of Ozone in water cause more vigorous oxidation of even more resistant organic compounds. |
Taste & Odor Control Most tastes and odors in water supplies come from naturally-occurring or manmade organic material contamination. Bacterial decomposition of humic material imparts taste to surface waters. The action of algae and actinomycetes gives rise to objectionable tastes. Chlorination of humic material leads to chlorophenols that are of far stronger odor and more antigonistic to taste than the original phenol and unreacted Chlorine. Most of these odors are removed with Ozone treatment. Even some sulphur compounds such as hydrogen sulfide, mercaptans or organic sulphides can be oxidized to Sulfates with Ozone. |
Turbity Removal Oxidation of dissolved Organic materials with Ozone results in polar and charged molecules that can react with Polyvalent Aluminum or Calcium to form precipitates. Treatment of surface water with up to 0.5 ppm of Ozone results in a decrease in turbidity, improved settleability, and a reduction in the number of particles. This treatment, referred to as pre-ozonation, destabilizes the colloid with a resulting reduction in the amount of coagulant needed to produce a clear filtrate. |
