Legionella: Beyond the Cooling Tower Threat

February 19, 2020 | By: Molly Looman

In 2015, New York City saw an outbreak of Legionnaire’s disease spread through a cooling tower. Legionnaire’s disease is a type of pneumonia caused by the Legionella bacteria. Since this outbreak, cooling tower maintenance has been a top priority for the commercial real estate industry. Not only is it a cost consideration, but also a major health and safety consideration. Here is what happened in New York and what can be done to prevent outbreaks.

The Bacteria

In 2015, nine cooling towers tested positive for the bacteria in the South Bronx. The outbreak killed 12 residents and affected over 120. Since 2000, cases of Legionnaire’s disease have increased by 400%. The reason Legionella is spread through cooling towers is because the bacteria prefers wet conditions between 98 and 109 degrees. Cooling towers are the perfect location for the bacteria growth as they hold large basins of water. The bacteria has been seen in similar machines such as humidifiers, whirlpool spas and domestic hot water systems. However, the spreading of Legionella can be avoided with proper cooling tower maintenance and consideration.

The Maintenance

The American Society of Heating, Refrigeration and Air Conditioning Engineers published the Legionellosis Risk Management for Building Water Systems in June 2015. This document provided an industry standard for the maintaining of water cooler systems to prevent an outbreak from occurring again. A few approaches can be made to decrease the chances of bacteria growth. First, cut off any dead legs or disconnected pipe. You can also install a recirculating pump for any stagnant water. Other strategies for preventing bacteria growth is a bio dispersant, controlling corrosion through anticorrosive additives and instituting a frequent cleaning protocol. Overall, the main way to prevent bacteria growth is proper maintenance and capital investment for water quality.

What Now?

After the New York outbreak, maintenance staff began taking extra precaution with cooling towers. More tests have been developed to catch the bacteria early or monitor counts that could lead to the formation of the bacteria such as the heterotrophic colony count. Property managers and operations staffs are taking better care in the water quality and assessing the need for a cooling tower on their property. Maintaining cooling towers is a financial gain as poorly maintained ones are less efficient and take more power.

Going Beyond

Water is just one place disease can breed. There are other maintenance considerations that must be made in order to prevent bacteria growth. Air filters and HVAC systems can house mold which can spread across an entire property. Poor maintenance of facilities can spread disease or be a safety risk. Maintaining and replacing air filters and HVAC systems can help retain air quality and decrease chances of spreading bacteria. Another consideration is amenities. Gyms and pools can be prime locations for a spread of illness. Maintaining proper cleaning schedules helps ensure the health and safety of your tenants. The same is true of any other high contact or high traffic areas on your property. Furthermore, the green cleaning movement has made great strides in making sure harmful chemicals stay off your property. Take a lesson from the missteps of the past, and make sure all systems are maintained property.


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