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. These ozone assisted flocculation systems remove 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.
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.

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. 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.
  • Ozone directly decomposes organic waste by oxidation.
  • Water ozonation. Unused ozone slowly decomposes to normal oxygen and remains dissolved in the water to the point of saturation.
  • Leaves no toxic residues in the water.
  • Ozone is produced on site and does not require storage or transportation.
  • Undissolved ozone off-gas is easy to separate from treated water in an 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 can help resolve water discharge liabilities.
  • Ozone prevents calcium carbonate scaling, removes existing scale, oxidizes and prevents greasy sediments on pool sides. Ozone treated water has a much lower cleaning cost.

8. Chlorine is controversial
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.

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.


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.

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. we look forward to working with your engineers on how to incorporate ozone into the system design.