1. Chlorine reacts with organic waste and forms a large number of highly toxic chloro-organic compounds, also referred to as combined chlorine. These are well known carcinogens, and are also very poisonous to marine life. In swimming pools these toxins may accumulate to very high concentrations. Red eyes and rashes are the most instant and obvious effects, and should be considered signals of a much more serious risk to human health. Pools usually use makeup water to dilute these dangerous compounds. As a result, an equal amount of pool water must be released into the environment.

2. Ozone systems are available to assist flocculation of organic waste at the overflow pond prior to filtration. In these systems ozone removes as much organic waste as possible thus leaving less waste for chlorine (bromine) to react with. The target level of combined chlorine is not to exceed 1.5 ppm. Bromine is more suitable than chlorine for cooperation with ozone.
While this is a very significant improvement, on average, the human body will absorb about half a liter of pool water every hour. The best pools have their water quality in compliance with the standards for drinking water supplies.

3. There are more then 30,000 swimming pools in Europe treated with ozone. In North American pools, the ozone dosage has often been underrated and a proof of ozone output was usually not required. Some ozone suppliers will then claim that chlorine is needed anyway and use this as an excuse. In the past this has caused understandable mistrust and this explains why the use of ozone in North America is at least 30 years behind Europe.

4. In Canada, B.C. Pool Regulations (Section 75) require that "a suitable residual of disinfectant shall be maintained throughout the swimming pool water". Section 47 further states: "If means other then chlorine are used as a disinfectant, residuals of equivalent oxidation strength shall be maintained in the pool water in accordance with Section 75." Yet, Some health inspectors and most surprisingly ? some engineering consultants continue to claim that a chlorine residual must be used. This is probably the result of a long-time misconception that ozone is too unstable to provide sufficient residual. In truth this is all a matter of dosage and water distribution within the pool.

5. Where the water distribution is to the latest building code, and the turnover time is below six hours, freshly charged water will reach every spot in the pool in less than five minutes. The halflife of ozone in water is 15 to 20 minutes. The best way to prove ozone?s effectiveness is by measuring the ozone residual returning from the pool. It should read at least 0.05 mg/L. The maximum allowable in Europe is 0.15 mg/L. Our systems monitor the dissolved ozone in the return from the pool, and just prior to further ozonation.
Some questions have been raised as to whether dissolved ozone is toxic to humans. No toxicity was observed for exposures of over 8 hours at levels of 0.15 mg/L of dissolved ozone. It is absolutely certain that dissolved ozone is by far less toxic than equivalent levels of chlorine or bromine.

6. Bromine, ozone and hydrogen peroxide have been used successfully in the past with or without chlorine residual. Ozone is the strongest and most convenient oxidant of all. Its stability in water is most convenient and it appears to be ideal. Present technology allows simple, automatic maintenance of the appropriate ozone residual level.

7. There are many advantages of treating pool water with ozone:
  • Filtration support. Ozone assists flocculation of organic waste materials, thus enhancing the effectiveness of sand filters.
  • Water purification. Ozone directly decomposes organic waste by oxidation.
  • Water cleaning. Properly dissolved ozone residual of 0.05 mg/L or higher assures the water is clean.
  • Water ozonation. Unused ozone slowly decomposes to normal oxygen and remains dissolved in the water to the point of saturation. This makes the pool water clean, sparkling and appealing.
  • Leaves no toxic residues in the treated water.
  • Ozone is produced on site and does not require storage or transportation.
  • Dissolved ozone at levels below 0.15 mg/L do not cause adverse health effects even during long term exposure.
  • Undissolved ozone off-gas is easy to separate from treated water in the off-gas tank, long before entering the pool, while chlorine is being constantly released in its highly toxic gas form right above the pool water.
  • Ozone ends water discharge liabilities.
  • Ozone prevents calcium carbonate scaling, removes existing scale, cleans and prevents greasy sediments on pool sides. Ozone treated water has a much lower cleaning cost.

8. Chlorine is controversial
Some older engineering specifications for Ozonation systems may still require that "all ozone is destroyed prior to entering the pool by passing through a carbon bed, then chlorine is introduced instead to maintain a disinfecting residual". Such requirements are partially based on a 30 years old German DIN procedure, an archiac design which has been changed. Reliable off-gas systems are now able to strip all undissolved ozone gas from the water flow safely thus no free ozone gas can escape to the pool. In the meantime, fear of ozone has diminished thanks to hundreds of published scientific studies. Ozone has become known as being of major health benefit to swimming pool users, and is being used by countless hospitals and rehabilitation centres. Today's technology does not always require chlorine assistance, except as a backup in case of maintenance or power blackout.
Using bromine (or chlorine) residual may be more acceptable where economics do not allow the best solution. In such cases, AZCO's modular system allows for easy expansion at a later date when the funds become available. Bromine is much more suitable than chlorine where there is a need to complement an ozone system (bromine cooperates with ozone chemically). While bromine is more expensive to buy, much less bromine is needed since ozone will recycle bromine up to 14 times in the pool water.

9. AZCO's own research has been verified at a number of public, commercial and hospital pools. The dosage in most cases is only 0.25 grams of Ozone per m3 (or 1 gram per 1000 gallons) of pool volume. A typical former German Engineering specification would require only about one third of this amount of ozone. But together with some extra carbon filters, large mixing and contact tanks and considerable space demand, the total cost of an old German system may easily end to be 2 to 5 times higher. Even for this much money the bathers are still treated with chlorine. Chlorine-free pools have been in operation for over 50 years in many non-German speaking countries as well ? especially in France.

10. During ozone start up in pools where chlorine was previously used, ozone may cause a few hours of foaming, flocculation, and milky water color. These are proper oxidation processes, carried out in a one-time event with no harmful effects. The filtration system will remove the oxidation byproducts and the water will become sparkling clean and sky-blue with a pleasantly clean smell.

11. All AZCO installations are approved by the health authorities and Worker's Compensation Boards, where applicable.

12. AZCO's ozone generators provide all the necessary ozonation power to purify, ozonize, and clean swimming pools, whirlpools, ponds, water works, and lakes of any size. The production of ozone is automatically maintained at the desirable levels anywhere in the whole pool. AZCO's modular system provides spare capacity in case of failure of any part of the ozonation system. Chlorine backup will be automatically employed in the unlikely case of extreme overload.


There are seldom two identical swimming pools or spas in the world. AZCO's engineers are ready to review and utilize your pool(s), existing equipment (such as tanks, pumps, filters, buildings) to be fitted for ozonation. To do so most efficiently, please answer the attached questionnaire. Your answers will be kept in strict confidence. The systems are engineered for fully automatic and worry free operation. Many features are included to prevent an overdose of ozone. Any single failure will not result in any increased risk for the bathers.

Ozone generators must be installed in a well-ventilated and dust-free room. In most cases, only a few square feet of floor space is needed. Detailed instructions for installation and operation will be provided when the project is ordered. The systems are easy to operate and maintain. The overall warranty is for three years, except on pumps where the manufacturer?s warranty is applied (generally one year).