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Overview: Ozone for Pools

Overview: Ozone for Pools

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Overview: Ozone for Pools

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  1. Overview: Ozone for Pools

  2. Ozone O3 History • Molecular ozone is a naturally occurring gas, made-up of 3 oxygen atoms • Discovered in 1840 • Name derived from the Greek word “ozein”, which means “to smell” • 1886: Europeans discover ozone can disinfect water • 1893: First full scale application using ozone for drinking water in Oudshoorn, Netherlands • 1906: Ozone first used to disinfect drinking water in Nice, France • 1915: At least 50 major ozone installations operating throughout Europe • 1937: First commercial swimming pool to use ozone in the U.S.A. • 1939: Ozone system displayed at the New York World’s Fair as the future of water treatment • 1940s: Ozone first used in U.S.A. to disinfect municipal drinking water • Ozone decomposes naturally into oxygen in the process of oxidation O3

  3. Ozone – Oxidation Strength • Ozone is the most powerful OXIDIZER commercially available • Other commercially available oxidizers include Chlorine (gas and liquid), Hydrogen Peroxide and Bromine. • Oxidizers react with organic and inorganic compounds by donating or receiving electrons. • Oxidizers can improve water quality by sanitizing and precipitating (making other chemicals come out of the water as solids) O3

  4. What Ozone Does • Oxidation • Because of its high oxidation potential ozone can precipitate a variety of organic and inorganic contaminants from pool water via direct filtration including iron, manganese, sulfides, metals, body oils, sweat and saliva among others. • Disinfection • Ozone kills bacteria, cysts and viruses up to 3,125 times faster than chlorine which is one reason it it used to purify municipal drinking water and bottled water worldwide. • Taste and Odor Control • Ozone oxidizes organic chemicals responsible for 90% of taste/odor/color related problems • Kills Algae Spores • Ozone effectively kills algae spores in the contact system, but an additional algaecide, like PhosFee from Natural Chemistry, Inc., is needed to control algae in pools treated exclusively with ozone. Fe Mn H2S Bacteria Organics

  5. Benefits of Ozone Use • Ozone changes the molecular structure of organic & inorganic compounds: • Kills spores, cysts, viruses, bacteria and bio-film • Precipitates dissolved inorganic compounds, like metals, to be removed by pool filters • Oxidizes and precipitates dissolved organic compounds, like suntan lotions, body oils, saliva, etc. • Acts as micro-flocculant for organic and inorganic contaminants to be filtered from pool water • Neutralizes chlorine byproducts • Generated onsite, on-demand • No transportation or storage of hazardous chemicals required • More powerful than chlorine • 1.5 time the oxidizing power of chlorine and up to 3,000 times faster acting • pH neutral • Doesn’t change the pH of water greatly simplifying water chemistry • Reverts to oxygen leaving no chemical byproducts, telltale taste or odor • Ozone’s only chemical by-product from oxidations is oxygen • Unlike chlorine, ozone creates no chloramines or their carcinogenic by-products like trihalomethanes (THMs) • Meets new Federal & State water regulations for THMs • Ozone is the only recognized disinfectant capable of practical inactivation of Cryptosporidium cysts and Giardia cysts

  6. Ozone Limitations • High Water Temperature • Ozone’s effectiveness is greatest at low water temperatures. Water temperatures above 40o C (104o F) accelerate ozone’s decomposition. • High Water pH • Ozone’s effectiveness is greatest at neutral (7.0) pH. Water pH above 9.0 will require higher initial concentrations of ozone to achieve desired results. Water pH above 10.0 neutralizes ozone and requires pre-treatment. • Ambient Ozone Exposure in the Air • High levels of ambient ozone in air can damage trachea and lung tissues. • EPA 8.0 hour exposure guidelines for ozone in air vary from .05 to .08 ppm. • Ozone dissolved in water is safer since lung tissue is the only tissue known to to be sensitive to ozone. • Limited residual effect in water • Ozone has half life of around 20 - 30 minutes in typical pool water temperatures • Hard Water • Ozone cannot oxidize calcium, magnesium, carbonate, or bicarbonate ions; consequently, ozone can not treat water hardness or alkalinity. • Radon • Ozone is incapable of oxidizing radon, methane, or nitrate ion. • Algae may be able to survive in an ozonated pool • Especially in areas of low circulation with a lot of sun • Ozone effectively kills algae spores in the contact system, but an an additional algaecide like PhosFree from Natural Chemistry, Inc. is needed to control algae in pools treated exclusively with ozone. pH

  7. Critical Success Factors for Ozone in pool water • Concentration of ozone in water • Concentration of ozone gas by weight • Quantity of ozone gas grams per hour (g/h) • CD production vs. UV production • CD feed gas • Oxygen • Dry Air • Ambient Air • Pressure • Gas & water temperature • Bubble size • Contact Time • Contact tank • Bottom feed into pool

  8. CD Ozone – Mass Transfer Henry’s Law (calculations below) - dissolved concentration of a substance in a liquid is proportional to its concentration in a gas Water treatment effectiveness depends on concentration of ozone DISSOLVED • “Mass Transfer” technology gets ozone from its natural gas phase into solution Factors affecting mass transfer of a gas into solution: • Concentration of ozone, in percent by weight, higher percent higher dissolved concentration (see chart) • Pressure - as pressure increases, more gas is forced into the liquid • Temperature of the water/gas mixture - at lower temperatures, ozone gas is more easily absorbed. At higher temperatures, water tries to release the gas rather than absorb it • Bubble size - as bubble size is reduced, the total bubble surface area increases, increasing the area for interaction between ozone and water • Quantity of ozone, in grams per hour The ozone gas concentration is determined at a standard temperature of 20 degrees C (68˚ F) and a standard pressure of 1 atmosphere.

  9. CD Ozone – Mass Transfer Effectiveness • Factors affecting transfer of a gas into a liquid: • Pressure: As pressure increases, more gas is forced into the liquid. • Temperature of the water/gas mixture: At lower temps, ozone gas is more easily absorbed by the liquid. At higher temps, water tries to release gas rather than absorb it. • Bubble size: As a gas is broken down into more and smaller bubbles, the total surface area of the bubbles increases, thus increasing the area for interaction of ozone and water. • There are two basic mass transfer approaches – diffusion, and injection:

  10. Solubility of Ozone in Water (ppm)

  11. Ozone Half Life versus Temperature * These values are based on thermal decomposition only. No wall effects, humidity, organic loading or other catalytic effects are considered.

  12. Ozone Decomposition Rates in Water Ozone decomposition in different types of water at 20 °C. Dissolved ozone can react with a variety of matter, such as organic compounds, viruses, bacteria, etc. As a result, ozone decomposes to other matter. This figure illustrates that the half-life of ozone in double-distilled water (1) is much longer, when compared to lake water (5) or tap-water (3). 1 = double-distilled water; 2 = distilled water; 3 = tap water; 4 = groundwater of low hardness; 5 = filtered water from Lake Zurich (Switzerland); 6 = filtered water from the Bodensee (Switzerland)

  13. Ozone - Contact Time • Disinfection power is the result of ozone concentration (mg/L , ppm) in combination with treatment time – Concentration x Time – “CT Value” • 1 ppm ozone in water for 1 minute = CT of 1, which kills most pathogenic organisms • Kill rate is measured in LOG reductions. 1 Log reduction kills 90%, 2 Log kills 99%, 3 Log kills 99.9%, etc. • Bacteria is killed by ozone very quickly and effectively upon contact • Viruses and cysts require longer contact times (higher concentrations of ozone in the water shorten the contact time necessary)

  14. Target Pool Conditions • Though requirements can vary, the commonly accepted ranges for swimming pool water parameters are generally as follows: • ParameterRange • pH 7.2 - 7.6 • Alkalinity 80 - 125 ppm • Hardness 200 - 270 ppm • Free Chlorine 0.6 - 1.0 ppm • ORP > 700 mV • Temperature 24 - 28 °C • ORP (Oxidation Reduction Potential) or Redox is used in pool water treatment as an indication of sanitation in relation to free chlorine parameter. ORP technology has gained recognition worldwide as a reliable indicator of bacteriological water quality.

  15. Target Pool Conditions The table below illustrates the Kill Time of E.Coli bacteria as a function of ORP value. With a value of 600 mV, the life of the bacteria is almost 2 minutes; at 650 mV it reduces to 30 seconds. Above 700 mV the bacteria is killed within a few seconds. It is therefore necessary for the water to have an ORP value of at least 700 mV to ensure good water quality.