The Impact of Storms on Legionella pneumophila in Cooling Tower Water, Implications for Human Health

Abstract

At the U.S. Department of Energy’s Savannah River Site (SRS) in Aiken, SC, cooling tower water is routinely monitored for Legionella pneumophila concentrations using a direct fluorescent antibody (DFA) technique. Historically, 25–30 operating SRS cooling towers have varying concentrations of Legionella in all seasons of the year, with patterns that are unpredictable. Legionellosis, or Legionnaires’ disease (LD), is a pneumonia caused by Legionella bacteria that thrive both in man-made water distribution systems and natural surface waters including lakes, streams, and wet soil. Legionnaires’ disease is typically contracted by inhaling L. pneumophila, most often in aerosolized mists that contain the bacteria. At the SRS, L. pneumophila is typically found in cooling towers ranging from non-detectable up to 108 cells/L in cooling tower water systems. Extreme weather conditions contributed to elevations in L. pneumophila to 107–108 cells/L in SRS cooling tower water systems in July–August 2017. L. pneumophila concentrations in Cooling Tower 785-A/2A located in SRS A-Area, stayed in the 108 cells/L range despite biocide addition. During this time, other SRS cooling towers did not demonstrate this L. pneumophila increase. No significant difference was observed in the mean L. pneumophila mean concentrations for the towers (p < 0.05). There was a significant variance observed in the 285-2A/A Tower L. pneumophila results (p < 0.05). Looking to see if we could find “effects” led to model development by analyzing 13 months of water chemistry and microbial data for the main factors influencing the L. pneumophila concentrations in five cooling towers for this year. It indicated chlorine and dissolved oxygen had a significant impact (p < 0.0002) on cooling tower 785A/2A. Thus, while the variation in the log count data for the A-area tower is statistically greater than that of the other four towers, the average of the log count data for the A-Area tower was in line with that of the other towers. It was also observed that the location of 785A/2A and basin resulted in more debris entering the system during storm events. Our results suggest that future analyses should evaluate the impact of environmental conditions and cooling tower design on L. pneumophila water concentrations and human health.

Digital transformation of legionella-safe cooling towers: an ecosystem design approach

“…Contextual information about the cooling tower is also important. For example, the meteorological conditions such as warm temperature, low winds, high humidity (Russo et al , 2018) or storms that may increase the risk of legionella proliferation and diffusion, even if biocides are used (Brigmon et al , 2020). It is now clear that climate change will escalate the problem of legionnaires’ disease and call for action from governments, academics and private organizations (Walker, 2018).…”

Rising Incidence of Legionnaires’ Disease and Associated Epidemiologic Patterns, United States, 1992–2018

“…Similarly, temperatures in the South reach Legionella -promoting temperatures, which also increase cooling tower use, earlier in the year than in the Northeast or Midwest, which might explain why the LD season begins first in the South ( 33 ). Furthermore, hurricane-produced rainfall increased during 1998–2016 ( 34 ), and hurricanes have been associated with elevated concentrations of Legionella bacteria in cooling towers and surface water ( 35 , 36 ). Travel is also a cyclical risk factor for LD but does not appear to influence seasonality; seasonal patterns for travel-associated cases were nearly identical to those for non–travel-associated cases during 2015–2016 ( 37 ).…”

Microbial Interactions — Underexplored Links Between Public Health Relevant Bacteria and Protozoa in Coastal Environments

“…Freshwater is considered the major reservoir for the pathogenic Legionella pneumophila ( Boamah et al, 2017 ). However, Legionella is often studied in man-made water systems, such as cooling towers ( Brigmon et al, 2020 ), due to the thermophily of the pathogen L. pneumophila ( Lesnik et al, 2015 ). Even though it is known that Legionella exist in freshwater and have cold-adapted variants ( Lesnik et al, 2015 ), few studies have reported their occurrence in natural aquatic environments, such as in lakes, rivers, and estuaries ( Carvalho et al, 2007 ; Parthuisot et al, 2010 ; Shimada et al, 2020 ).…”