Hospital's Cooling Tower Retrofit Seeks to Eliminate Legionnaire's Disease
In New York City, outbreaks of Legionnaires’ disease have become an all too common occurrence. Over the last few years, hundreds have been severely sickened and dozens killed by the bacteria that proliferates in water systems, like cooling towers used in conjunction with large HVAC systems.
When a cooling tower supporting the HVAC system at NYC Health + Hospitals/Lincoln was nearing its expected end of life, the management of the hospital in the South Bronx saw an opportunity. The year before, the neighboring community had experienced outbreaks of Legionnaires’ disease, and even though the hospital’s cooling towers played no role in those outbreaks, the chance to increase protections against possible future exposures of the bacteria that cause the disease was an important consideration.
Accordingly, the hospital’s engineering and management teams prioritized the selection of an antimicrobial cooling tower option. They also gave extra weight to finding a system that would save energy.
Legionnaires’ disease is a severe form of lung infection caused by exposure to bacteria known as Legionella. Found naturally in freshwater environments, like lakes and streams, Legionella becomes a health hazard when it grows unabated in water that is not properly treated. While this can include showerheads, hot tubs, and hot water heaters, cooling towers are often found to be the source of outbreaks.
Cooling towers have a long history of effectively expelling heat from the water used in many commercial and industrial applications. However, a recent study from the Centers for Disease Control and Prevention (CDC) found that an overwhelming majority of the cooling towers they tested contained Legionella DNA. This indicates that the dangerous bacteria was either currently present or had been at some point and without proper precautions could eventually give rise to an outbreak.
NYC Health + Hospitals/Lincoln knew what was needed. Louis Iglhaut, associate executive director of the hospital, led the team responsible for the specification, acquisition, and installation of the new cooling towers.
Originally, one of Iglhaut’s design priorities for Lincoln Hospital’s new cooling tower was to focus on efficient and thorough water circulation. In other words, the design of the new towers should not have corners in the basin, as many do, including the stainless steel models the hospital was replacing.
“We needed to think outside the box,” explained Iglhaut. “Given our concern about the dangers of microbial growth, we decided to only consider towers with rounded basins.”
Iglhault’s search led his team to find a new breed of cooling towers that had just recently become available. Fully compounded with an antimicrobial resin, these towers contain wide-spectrum additives that operate on a cellular level to continuously disrupt and prevent the uncontrolled growth of microorganisms and biofilm.
“These towers, which are rounded, not only solved the circulation problem but also have antimicrobial chemicals embedded into the tower’s high-density polyethylene (HDPE) material, which helps to prevent the growth of dangerous bacteria, such as Legionella,” he said.
The towers the hospital selected were made by Delta Cooling Towers, which introduced the HDPE cooling tower in the 1970s. The company says its towers include an antimicrobial fill (the medium over which the hot water is distributed as it is being cooled) as well as a structural casing and sump all composed of antimicrobial material. Officials said this is significant because biofilm growth and microorganisms allow a place for bacteria to hide from chemical treatments and also provide nutrients for pathogen growth.
Convinced that the rounded design, HDPE durability, and protective features of the antimicrobial material were a good solution for Lincoln Hospital, the procurement team selected Delta’s Anti-Microbial™ Series models with 18 modular cooling towers that provide a combined total of 6,000 cooling tons.
To reduce future outbreaks, cities like New York are increasingly requiring extensive use of harsh chemicals to be used within all cooling towers. For Lincoln Hospital, this required a professionally maintained water treatment program that used strong biocides and acid feed treatment chemicals. While these could have a life-shortening corrosive effect on stainless steel towers, engineered plastic HDPE towers can withstand even the harshest chemicals.
Another major factor affecting Lincoln Hospital’s decision to adopt the new cooling towers was the promise of energy savings.
“We worked with New York Power Authority to ensure that the new cooling towers would be as energy efficient as possible,” Iglhaut says. “Our old towers used large, 30-hp fans on each unit, which required the use of a lot of electric power. The new modular units are equipped with smaller hp, 60-inch fans, so the energy consumption is far less.”
He added that the hospital installed VFDs are expected to give even more savings. Also, the installation of the new cooling towers added to efficiencies. Because the towers were smaller and lighter, the installation team was able to use a small crane to lift the towers into position, which ensured a seamless transition from the old system to the new one.