Ozone Cooling Water Treatment

Spartan Environmental Technologies supplies ozone generators and fully integrated ozone water treatment systems for cooling towers and cooling water treatment applications. Call Spartan help selecting one of our turnkey packages.

Ozone Treatment of Cooling Water Summary

Ozone generators have been used extensively for the treatment of cooling water. This is due to the fact that ozone is a powerful, but environmentally friendly biocide. It effectiveness has been study by both the US government (see Federal Technology Alert on ozone for Cooling Water Treatment>) and industrial water treatment companies (see Application of Ozone in Cooling Water Systems, a study of ozone on the laboratory, pilot and commercials scale). To download a shorter technical bulletin, click on the following link Ozone Cooling Water Treatment PDF.

The unimpeded growth of bacteria, algae, fungi and mussels in cooling circuits promotes the formation of deposits in pipes, heat exchangers and the internal parts of cooling towers. This can lead to a reduction of heat transfer efficiency, corrosion and in some cases, emissions of harmful pathogens such as legionella. In fact, ASHRAE has recently proposed regulations for controlling biological growth in cooling towers in order to minimize the potential for the growth and emission of legionella. A more detailed discussion on the need for water treatment in cooling circuit can be found by following this link.

Ozone is a powerful biocide, which, when compared to organochlorine-based biocides, not only combats microbial growth processes but also continuously reduces organic impurities. These impurities, measured as COD and AOX, can be reduced to acceptable discharge levels. No undesirable secondary reactions or salt build-ups occur. A more detailed discussion on the effects of ozone in a cooling tower can be found by following this link.

Ozone is produced in an ozone generator and usually injected continuously into the cooling water system in a branch stream. The microorganisms in the systems are thus under permanent attack and microorganism counts are held at a very low level. This also applies to the bio films in the systems, so the tendency for coatings to form is kept to a minimum. This means that intervals between overhauls and maintenance sessions can be extended. A residual ozoneconcentration of 0.1 to 0.2 ppm is typically effective in keeping the cooling tower and the cooling circuit clean.

Some suppliers of ozone systems suggest that ozone can universally protect a cooling tower from microbiological films as well as scaling and corrosion problems with zero blow down. While there are examples of this type of operation it is highly dependent on the water chemistry of the tower and make-up water. Spartan believes that there are situations when ozone should be used in conjunction with anti-scaling agents and corrosion inhibitors.

The chemical added to an ozone treated system need to be compatible with ozone. Spartan supplies a chemical formation for ozone treated cooling towers should these additional materials be needed. In any event, before applying any treatment to a cooling tower the tower owner should consult with a professional water treatment company that has analyzed the water chemistry.

In conclusion, the advantages of ozone generator use in cooling towers include:

  • Low corrosion rates
  • No persistent chemicals or disinfectants in bleed. Ozone breaks down to oxygen.
  • In some cases ozone can replace disinfectants as well as dispersant and inhibitors
  • In many cases, a lower overall cost
  • Effective in a wide pH range
  • Effective against mussels

Ozone use in cooling towers requires consideration of the following factors:

  • Make-up water with high hardness and COD levels is less suitable for ozone water treatment
  • Dead spots in the circulation system need to be eliminated.
  • The temperature of the cooling water in which ozone is used should be limited to around 45°C.
  • Materials of construction should be compatible with ozone.