With the recent Legionnaires’ disease outbreak in New York City, more is being done to prevent the occurrence of further outbreaks. The New York City outbreak — which was preventable — killed 12 people and infected about 127 others.
The outbreak was linked back to cooling towers, which vary from small rooftop units to huge structures standing 660 feet tall. These towers are responsible for recycling water through buildings in an effort to be more efficient, but outbreaks may occur if those towers aren’t properly maintained.
The Centers for Disease Control and Prevention define Legionnaires’ disease as a severe form of pneumonia cause by bacteria. Older people and those with respiratory issues or weakened immune systems are the most at risk when it comes to this disease. Death occurs in about 30% of all cases.
The reason cooling towers are often such a hotbed for outbreaks like this is because bacteria grow best within warm water, which is found in cooling towers, fountains, hot tubs, or plumbing systems. Even just breathing in mist containing bacteria may infect people, though it cannot move from person to person. So how can those with cooling towers prevent other outbreaks?
Dr. Rajiv Sahay, a lab director of Environmental Diagnostics Laboratory (EDLab), a division of Pure Air Control Services in Clearwater, Florida, weighed in on the issue. Sahay said, “Aquatic habitats with temperatures ranging from 5.7° to 63°C and containing organic constituents (nutrients) are most favorable for the growth of Legionella species.”
Other conditions favorable to the bacteria are water stagnation, high pH levels, and a buildup of sediment, says Richard Gerbe, cofounder of Highmark in New York City, which operates multiple divisions focusing on HVAC, energy services, and water management.
“The dust and debris that bacteria like to propagate in can be removed and kept out through proper maintenance, filtration, water treatment, and monitoring. This will control the growth of bacteria, such as Legionella, and ensure that outbreaks, such as Legionnaires’, are prevented,” Gerbe said.
James T. Turrisi, president and CEO of Matco Service Corp., a commercial HVAC contractor serving New York, New Jersey, and Connecticut, also added, “Most cooling towers are maintained chemically by water treatment companies, and they are maintained mechanically by service companies, such as Matco.”
Cleaning and replacing parts frequently is essential in order to keep the tower in working order and will keep the water moving through the system safe.
“The goal is to keep the unit as clean as possible,” Gerbe said. He suggests having a contractor “conduct ongoing inspections to identify any mechanical deficiencies; repair any mechanical issues a cooling tower may have — such as leaks and broken panels, fans, and infill — so it operates as designed; ensure drift eliminators are sufficient and functional; and perform regular cooling tower cleanings.”
Also important during this process is controlling the accumulation of scale and biological growth, which contaminates the water. Philippe Boileau, a consulting chemist based in Montreal, says biocides “are ineffective if microbes are hiding inside the protection of mineral deposits. You have to clean first and then disinfect and decontaminate.”
He adds, “Biocides do not work where they do not go. Make sure to circulate everywhere when you inject a biocide. Coordinate with control people to make sure the required pumps are activated when and as long as required.”
Also, he added, “Use as much as required, but no more than needed. Knowing the volume of the system, make sure you inject enough to reach the minimum required concentration for the minimum required contact time at given water conditions. When you inject in the middle of the day, where water demand is high, it’s possible your biocide will get diluted before it has the time to be efficient. Try injecting it right before evening hours, when demand is minimal and contact time is maximal, if you can.”
Outbreaks have continued across the country in recent months, with outbreaks also occurring in Illinois, San Quentin, California, and another outbreak in New York City.
