Chlorine Dioxide Advantages:

  • It is a very powerful disinfectant and biocide;
  • It prevents and removes biofilm;
  • Unlike chlorine, chlorine dioxide is effective at pH between 4 and 10. The corrosive effects of chlorine dioxide are minimal compared to the corrosive effects of plain tap water;
  • The bactericidal efficiency is relatively unaffected by pH values between 4 and 10. Chlorine dioxide can be used as a spray. All parts, therefore, can easily be reached;
  • And, last but not least: less environmental impact.

Biofilm Removal – Cooling Towers & Closed Loops

Aqua Disinfect, a division of Aqua Service, is a service company providing chlorine dioxide generators and CLO2 in solution (Aqua D3000) to solve bacteria problems in a building’s mechanical (process water) and drinking water (potable) systems as well as bacteria problems in many other industries and businesses.

Of the oxidizing biocides, chlorine dioxide is the most selective oxidant. Both ozone and chlorine are much more reactive than chlorine dioxide, and they will be consumed by most organic compounds. Chlorine dioxide, however, is more selective and is not wasted on peripheral compounds, allowing it to go directly to the application. This allows much lower dosages of chlorine dioxide to achieve a more stable residual than either chlorine or ozone. Chlorine dioxide can be effectively used in much higher organic loading than either ozone or chlorine because of its selectivity.


A biofilm is a layer of microorganisms contained in a matrix (slime layer), which forms on surfaces in contact with water. Incorporation of pathogens in biofilms can protect the pathogens from concentrations of biocides that would otherwise kill or inhibit those organisms freely suspended in water.

Biofilms provide a safe haven for organisms like Listeria, E. coli and Legionella, where they can reproduce to levels where contamination of products passing through that water becomes inevitable.

It has been proven beyond doubt that chlorine dioxide removes biofilm from water systems and prevents it from forming when dosed at a continuous low level. Hypochlorite, on the other hand, has been proven to have little effect on biofilms.


Cleaning and disinfecting cooling towers is essential for several reasons, most of which are well known. Clean pipes mean higher heat exchange efficiency, pump lifetime improvement, and lower maintenance costs.

Most people, however, are unfamiliar with the fact that cooling towers pose a possible health risk. The high temperature condition is ideal for the growth of several pathogen organisms (such as Legionella).


Scrubbers are similar in design to cooling towers. The primary difference between the two is that scrubbers are pressurized systems, while cooling towers are vacuum systems. Scrubbers re-circulate water and spray it across the top of the system, counter-currently to the airflow.

Chlorine dioxide added to the re-circulated water reacts rapidly with odor-causing species that have been absorbed in the water, as well as those species that remain in the air. Usually, a very low chlorine dioxide residual, around 0.2 ppm, is sufficient to ensure odor control.