Controlling Growth of Legionella in Water Systems

How to Control Legionella Growth in Cooling Towers

Cooling towers are a marvel of the modern age - a truly ingenious invention which allows us to cool large spaces relatively quickly, making life more comfortable and convenient. If not cleaned and maintained properly, however, cooling towers can become a potentially deadly structure that harbors bacteria which can cause life-threatening complications.

In order to control the growth of Legionella, you should have your cooling towers regularly disinfected. Otherwise, your cooling towers could become the source of a Legionnaires’ outbreak.

What is Legionnaires’ Disease?

Legionnaires’ Disease is a condition that affects the lungs as a result of breathing in or drinking water or air particles contaminated with Legionella, a bacteria which accumulates in damp, dark places, including untreated cooling towers. For many individuals, especially those with underlying health conditions, Legionnaires’ can cause lifelong respiratory problems and even fatal pneumonia.

While the chances of developing Legionnaires’ Disease are quite rare, even for individuals exposed to the bacteria, the average fatality rate for those who develop Legionnaire’s is concerning. According to studies conducted by the Centers for Disease Control and Prevention, as many as 1 in 10 individuals who contract the disease through contaminated water or air will die, while 1 in 4 who contract the disease in a hospital or healthcare facility will die.

LEARN MORE: Reducing Risk of Legionnaires' Disease

Signs and Symptoms of Legionnaires’ Disease

The earliest signs and symptoms of Legionnaires’ Disease and exposure to Legionella are:

  • Headache

  • Nausea

  • Vomiting

  • Cough

  • Trouble breathing

  • Muscle and body aches

  • Fever

Gastrointestinal symptoms such as diarrhea and severe stomach cramps are also not uncommon. If an individual has been exposed to Legionella growth, he or she should seek emergency care as soon as possible.

Treatment of Legionnaires’ Disease

The CDC notes that Legionnaires' Disease is often successfully treated with antibiotics, although individuals with lung damage may experience lifelong respiratory problems as a result of the disease. Chronic smokers and individuals with pre-existing conditions like COPD or asthma may also experience lifelong symptoms of Legionella exposure regardless of whether or not they contract Legionnaires’ Disease.

LEARN MORE: Legionella Growth Control Guides

Control of Legionella Bacteria in Water Systems

The most important and essential way to reduce the risk of Legionella is to properly clean and maintain water systems. The control of Legionella should be a continual process, and every organization should have standards in place for preventing the growth of bacteria in water supply systems.

  1. Be aware of areas where Legionella could grow.

  2. Prevent water stagnation and water temperature fluctuations which can cause bacterial growth.

  3. Establish a cleaning procedure and water treatment team who will clean water systems on a scheduled date to prevent scale and bacterial growth.

  4. Utilize independent cooling tower consultants to ensure the cleaning process is efficient.

  5. Document all cleaning procedures and evidence of bacteria growth.

  6. Notify authorities if bacterial growth is found.

Legionella Cooling Tower Treatment Toolkit

For routine treatment of cooling towers to control the growth of Legionella, use the following procedure.

  1. Feed a halogen source such as chlorine or bromine continuously and maintain a free residual.

  2. Monitor the residual at sample points throughout the water system to ensure adequate distribution. The effectiveness of either halogen decreases with increasing pH; bromine is relatively more effective at a higher pH (8.5 to 9.0).

  3. Dispose of system water directly to surface water. This may require dehalogenation.

Note: A biodispersant/biodetergent may aid in the penetration, removal, and dispersion of biofilm and often increases the efficacy of the biocide.

CTI’s Guide to Legionella Control and Regulations on Water Treatment Programs

To learn more about the use of halogens in the cleaning process and guidelines for routine and emergency water system treatment, download CTI’s Best Practices for Controlling Legionella Growth.


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