Antimicrobial cooling towers

This antimicrobial option reduces the risk of Legionnaire's disease in cooling tower applications or chillers.

by Delta Cooling Towers

A new study by the Center for Disease Control and Prevention (CDC) in which 196 cooling towers were used across the country found that the 84 percent contained Legionella DNA, indicating that the dangerous bacteria that cause a type of severe pneumonia, which may even be deadly, were present or had been present at some time. This means that the real question is not "if there will be another outbreak", but "where and when" will occur.

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"During the 2000-2014 period, passive surveillance of legionellosis in the United States showed an increase of 286% in the cases reported by each 100.000 inhabitants," according to the CDC website.

The CDC also estimates that 5.000 cases of Legionnaires' disease are reported annually in the United States each year. Therefore, maintaining Legionella outside the water supply systems of buildings, within which cooling towers constitute a known risk, is essential to prevent infection.

In response to this problem, HVAC unit contractors are combining chillers and high performance plastic cooling towers with new antimicrobial options that significantly reduce the risk of infection.

Control of the growth of pathogens
Throughout the United States, as well as in most parts of the world, the pillar of large refrigeration systems remains the traditional combination of chillers, air conditioners and cooling towers. Cooling towers have a long history of effectiveness in expelling heat from the water used in many commercial and industrial applications where chillers are used.

However, it is well known that, under typical operating conditions, cooling towers can propagate Legionella. The design of many towers creates pockets where water can stagnate, a condition that can lead to the development of microorganisms.

This led recently to the American National Standards Institute (ANSI) and the American Society of Air Conditioning, Refrigeration and Heating (ASHRAE, for its acronym in English) to publish its 188 standard, called "Legionellosis: Management of risks in the Construction of Water Systems ", a document that establishes the new standards and requirements that must be taken into account in the design of new buildings and renovations of existing structures in order to mitigate the risks of contamination.

"All those responsible for facilities with HVAC or process cooling systems should be aware of the legionnaire's disease and be able to deal with any concerns that arise in this regard," says Rick Hill, director of facilities at Arkansas Surgical Hospital , a medical property hospital specializing in joint and spinal surgery in central Arkansas. "Good procedures must be implemented to prevent or control the disease."

When it came time to replace an air-cooled chiller at Arkansas Surgical Hospital, Steve Keen, president of Powers of Arkansas, the HVAC contractor responsible for the hospital project, recommended and installed a water-cooled chiller, along with an advanced cooling tower with microbial properties.

"Legionella is always a concern when using HVAC systems that use a cooling tower and wherever there is water exposed to the atmosphere," Keen says. "The antimicrobial properties of the Delta cooling towers help prevent that kind of growth and the exposure of patients and staff."

Delta Cooling Towers recently launched a line of towers built with antimicrobial resin, which is fully integrated into the structural material and housing of the cooling tower. The tower fill and dew point remover are also made of antimicrobial PVC.

The antimicrobial resin contains broad spectrum additives that operate at the cellular level to continuously interrupt and prevent the uncontrolled growth of microorganisms and biofilms inside the tower. The efficacy tests were performed by the Special Pathogens Laboratory, The Legionella Experts.

The design and materials of the tower can be very important in preventing the growth of pathogens. To avoid standing water problems that cause the growth of pathogens, experts recommend that the designs of the cooling towers have a collection tray and / or a system of sweeping pipes for the tray with slope.

While some tower manufacturers currently market a tower with an antimicrobial filler (the medium through which hot water is distributed while cooling), a better option is to have a tower whose fill, structural shell and sump are made of antimicrobial material .

"We decided that since we were replacing the air-cooled chiller with a water-cooled one, we wanted a cooling tower that was in keeping with our philosophy of protecting patient safety," says Hill, who advocated antimicrobial technology and found support for she among those in charge of the hospital. "We want to maintain one of the lowest infection rates among hospitals in the country."

The Arkansas Surgical Hospital already has a very low infection rate, of less than 0.3%, compared to a national average of 3% among US hospitals.

Energy savings and long lifespan
By proactively switching to an advanced antimicrobial tower cooler, along with a very high efficiency HVAC cooler, the hospital is also significantly reducing energy costs, which was also a primary concern.

"Our previous HVAC system, air-cooled, required a lot of electricity," adds Hill. "With the water-based cooling tower and the efficient chiller, we hope to save tens of thousands of dollars per year in energy costs."

The durability and long life of the cooling tower were additional issues that Hill considered.

Metal-coated cooling towers are vulnerable to corrosion by the action of salty air, industrial gases and even chemicals used to treat recirculating water. The best water treatments for the prevention of Legionella, in fact, are oxidizing biocides that react with aggressiveness to metal surfaces, attacking the metal-coated cooling towers and shortening their useful life.

As a result, metal cooling towers require more patching, more maintenance, more downtime and, ultimately, replacement.

Hill says that he thought about acquiring a metal cooling tower, but finally decided that its maintenance would be very difficult.

"Maintaining a metal cooling tower requires more work than we thought was desirable and the units have a shorter life cycle because the metal is oxidized and requires repair and repair," explains Hill.

By choosing Delta's cooling tower, whose filler, de-oiler and housing are made of corrosion-resistant antimicrobial plastic, the Arkansas Surgical Hospital now has a cooling tower immune to the corrosive effects of ambient air and substances. chemicals for water treatment, as well as oxidant biocides; all of which deteriorate the cooling towers with metallic coating.

In addition, since the molded plastic cooling towers are one-piece, there are no problems with premature natural wear of the joints, welds and patches. Therefore, plastic models have a longer life and cleaning, repairing or replacing them means much less downtime.

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