The Legionella bacteria was named after an outbreak in 1976 at the American Legion Convention that lead to 221 cases of illness and 34 deaths. The legionella bacteria can cause the serious respiratory disease, Legionellosis, or what is commonly referred to as, Legionnaires’ disease. As a facility owner, it’s important to recognize that cooling towers are susceptible to harboring and spreading the bacteria. Regular testing and proper treatment for Legionella can help protect your facility and surrounding area.

Knowing The Risk Legionella is a waterborne bacterium that can live and grow in all surface water, including ground water and wastewater. The bacteria thrive in the presence of a biofilm (slime) and can live inside amoebas, protozoan, and other microbiological organisms in the fouled water. Water between 75°Fand 115°F is the ideal environment for the Legionella bacteria, making cooling towers one of the main distribution methods of the bacteria. Hot tubs, decorative fountains, large plumbing systems, and hot water tanks and heaters are also prone to spreading the bacteria.

Spreading Legionella Legionella can only be contracted by inhaling contaminated mist or water droplets. It cannot be transmitted person to person. Cooling towers produce small water droplets that are propelled outside of the tower by the fan, making them a common source for spreading the bacteria.

Who’s At Risk? The majority of generally healthy people do not get sick after exposure to the Legionella bacteria. People with weakened immune systems, chronic lung disease, current or former smokers, and people over 50 are most vulnerable to the disease.

Preventing And Controlling The Bacteria The first line of defense against Legionella is a water treatment program that uses a dual alternating biocide program. One biocide needs to be an oxidizing biocide, like stabilized bromine, and the other needs to be a non-oxidizing biocide with or without a dispersant. The two chemicals work together to increase the effectiveness of your water treatment program, and can destroy and control the microbiological growth that can harbor the potentially dangerous bacteria.

When To Test There is currently no legislation mandating Legionella testing or the frequency but, there are recommendations based upon the facility type. Industrial sites should be tested at least twice a year, while office buildings should be tested quarterly. Schools, hospitals, and other locations where people are at a high risk of contracting the bacteria should be tested monthly.

If your facility receives a positive result after testing for Legionella, a water treatment technician will review the results and determine if system disinfection is necessary.

To learn more about Brady’s water treatment program and how it can help protect your facility from Legionella, visit or call (800) 849-1915.

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