The Center for Disease Control (CDC) stated that “9 in 10 investigations show almost all outbreaks were caused by problems preventable with more effective water management.” Regular testing and water maintenance are of high importance because of how Legionella spreads to cause illness. Cooling towers use water as the heat transfer medium to provide comfort or process cooling. System water is cooled through evaporation within the tower, creating a warm, stagnate environment which is ideal for bacteria growth. If legionella is present and allowed to grow through improper water management, the aerosolized mist created by the cooling process will spread the bacteria to the surrounding area and into buildings via air intake systems. Inhalation of the aerosolized legionella bacteria can lead to a severe form of pneumonia (Legionnaires’ disease), which can result in hospitalization or even death for immunocompromised individuals.
How can we minimize the risk of spreading Legionella from the cooling tower? The first step is to test the cooling tower water on a regular basis. Public Works and Government Services Canada recommends, “Weekly dipslide tests to determine the total bacteria count (TBC) at each water sampling location. While the system is in normal operation, perform monthly Legionella bacteria culture tests to identify total Legionella pneumophila including all serogroups (LPTOT) bacteria levels.” The second step is to determine a water management and sanitization program to minimize bacterial growth in the cooling tower. This can include a clean out and disinfection of a system upon initial start-up and after shut-down (twice yearly) along with a comprehensive ongoing water treatment program for corrosion and bacteria control.
CDC states that “There is no known safe level of Legionella in building water systems. The intent of a water management program should be to manage building water systems to reduce the hazardous conditions that allow the Legionella to grow and spread to susceptible people.” To contain and prevent further spread of the respiratory disease-causing bacterium, Legionella, owner/operators can work with local water treatment specialists like PACE Chemicals to determine the best management plan for their cooling towers.
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