In the summer of 2015, more than 100 people in the Bronx, New York City, fell ill, and a dozen of them died. The culprit was not Ebola, Zika, or any other of the nightmarish viruses that haunt the news media. It was water—specifically, water contaminated with the bacteria Legionella, which are responsible for the lung infection Legionnaires’ disease.
Eventually, it came to light that the bacteria were growing in the cooling tower of a Bronx hotel; when the cooling tower emitted water droplets into the air, at-risk individuals (e.g., the elderly, smokers and those with weakened immune systems) breathed them in and became sick.
Cooling towers are used in many applications, from keeping the air conditioning running in hotels, office buildings, hospitals and schools to cooling manufacturing equipment and server farms. Proper treatment of the water in cooling towers prevents the formation of biofilm, which can impede a tower’s efficiency, increase corrosion and provide a safe haven for bacteria like Legionella to grow.
“About the time that you can see biofilm—so, about 5-mm-thick biofilm—[it] will reduce efficiency of a large heat exchanging system somewhere between 40% and 60%,” said Christine McInnis, water platform leader at Dow Microbial Control.
Treatment in the Tower
Treatment of biofilm entails using biocides, which often come in 55-gal, 500-lb drums full of liquid. This can pose a problem to commercial and institutional markets, said Mike Hunter, global technical director of AP Tech Group—a customer of Dow specializing in solid water treatment chemicals.
“You’re talking about taking chemicals into buildings that aren’t really designed to handle big bulk liquid chemicals,” Hunter said.
Many problems in water treatment, Hunter said, have to do with spills, leaks, or bursts. “If you were to drop a gallon of milk, it makes a mess. If you can imagine somebody dropping a 55-gal barrel for whatever reason, that’s an awful lot of chemical that would go everywhere.”
To remedy these issues, Dow manufactures a solid biocide and has partnered with APTech to bring it to market. The solid biocide comes in smaller containers and is available at higher concentrations than liquid biocides. The solid biocides’ chemistry is chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT), a “common chemistry used in the industry,” according to McInnis, but also one primarily used in liquid form.
Because the solid biocide product weighs less, its shipping costs are lower and its carbon footprint is reduced. “Customers are getting financial benefit by not having to pay for as much freight,” McInnis said.
Registered with the U.S. Environmental Protection Agency for biofilm control, the biocide contains nonoxidizing chemistries, which target specific parts of the cell (e.g., the cell membrane, metabolic pathways) to kill it.
Beyond Commercial Cooling
While losing cooling capacity in an office building might give rise to disgruntled workers, losing cooling capacity in a manufacturing situation could prevent a company from turning out product, resulting in losses in the millions of dollars per day.
A manufacturing plant’s biocide choices depend on “the volume of water that’s used in the system and what the discharge regulations for that facility are going to be,” McInnis said.
For instance, a fairly small manufacturing facility might be able to discharge into municipal wastewater treatment plants, while a larger manufacturing facility might install its own wastewater treatment plant or draw water from—and discharge it into—nearby surface water bodies.
While solid biocides could benefit the smaller facilities, larger facilities—such as massive industrial power plants, which use several hundred gallons of product in a week—are more comfortable handling chemistries and therefore might not gravitate toward solid biocide technology.
Nevertheless, with water scarcity issues constantly looming—and with the difficulty of protecting cooling water systems during attempts to cut down on water use—solid biocides could be a suitable solution for both industrial and commercial applications in the future.
