3 Steps for Legionella Bacteria Control in Cooling Towers in Periods of Extreme Weather
By Hilary Nardone, MPH, Environmental Group Training Manager
Certified ASSE 12080 Legionella Water Safety and Management Specialist
This summer, intense weather has been bearing down on large parts of the United States. Heavy rain and flooding are widespread across the Midwest, and extreme heat is cloaking most of the country. Recent studies and advisories have reinforced the impact these extreme weather events can have on cooling tower systems. New York City issued a heat advisory to all cooling tower owners to remind them how cooling towers could be impacted. According to the heat advisory, “Hot temperatures may impact cooling tower operation by causing higher water temperatures, faster depletion of disinfectants, and increased drift loss.” Findings from a study released earlier this year suggest that the “increase in Legionnaires’ disease across the US may be explained by flooding…” and that Legionnaire’s disease hospitalizations increased in months with anomalously high precipitation.
It is common for Legionella bacteria to be found in cooling tower systems at a higher abundance in the summer months compared to the rest of the year. Figure A summarizes this trend and correlates to the weather-related information from recent research and public health notifications.
While these weather-related events can increase the risk of Legionella bacteria amplification in cooling tower, fortunately there are some easy ways to significantly minimize risk. Keep reading for actionable ways to protect your cooling tower systems during times of extreme weather!
3 Proactive Steps to Minimize Legionella Bacteria Growth in Cooling Towers During the Summer Months:
- Monitor your cooling tower system’s water quality. Oxidant (chlorine or bromine) levels, pH, temperature, bacteria dip slides, and Legionella bacteria culture samples are all indicators of your cooling tower system’s overall water quality. High dip slide counts and/or positive Legionella bacteria results could indicate the need for an increase in oxidant residual. With the right chemicals and automation, this can quickly be addressed.
- Increase the oxidant level in your cooling tower system. A higher-than-normal dosage level of chlorine- or bromine-based biocide can help minimize the risk of Legionella growth in cooling tower systems during the summer months. In fact, the New York City Department of Health and Mental Hygiene requires that all cooling towers receive one summertime hyperhalogenation between July 1 – August 31 each year.
- Inspect your equipment. Cooling tower system equipment parts, such as drift eliminators, fill, and basins can all harbor biofilms and scale, allowing Legionella bacteria to amplify. By performing routine inspections on equipment, these findings can be acted upon promptly.
Barclay’s team of licensed pesticide applicators apply industry-leading best practices that give peace of mind to cooling tower owners. Contact Barclay Water Management today to ask how Barclay can help you protect your cooling tower from Legionella bacteria amplification.
 New York City Department of Health and Mental Hygiene. Heat Advisory for Cooling Towers. Office of Building Water Systems Oversight. Email correspondence, July 23, 2022.
 Lynch VD, Shaman J. The effect of seasonal and extreme floods on the hospitalizations for Legionnaires’ disease in the United States, 2000 – 2011. BMC Infectious Diseases. 2022; 22(550). doi: 10.1186s12879-022-07489x
 The Rules of the City of New York, Chapter 8 Title 24 §8-04(f). Accessed July 27, 2022. https://codelibrary.amlegal.com/codes/newyorkcity/latest/NYCrules/0-0-0-42699.