SPR 2018

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From top: Legionella is always a concern for HVAC systems, so when Arkansas Surgical Hospital recently upgraded its system, a cooling tower from Delta Cooling with antimicrobial properties was chosen. > This recently introduced antimicrobial cooling tower by Delta Cooling substantially reduces the risk of Legionella. TACKLING LEGIONNAIRES' I t has been well established that under certain common conditions, cooling towers can propagate Legionella, the bacteria that causes potentially fatal Legionnaires' disease. This has recently led ANSI/ASHRAE to publish its Standard 188, Legionel- losis: Risk Management for Building Water Systems. According to the Centers for Disease Control and Prevention, 84 percent of cooling towers tested across North America contained Legionella DNA. This indicated dangerous bacteria was present or had been at some point. To combat this growing epidemic, cooling tower manufacturers are releasing high-performance plastic cooling towers with new antimicrobial options that significantly reduce the infection risk. AT THE FOREFRONT Cooling towers have a long history of ef- fectively expelling heat from the water used in many commercial and indus- trial applications that involve chillers. However, the design of most cooling towers creates pockets where water may stagnate, a condition that can lead to microorganism development. "All facilities with HVAC or process cooling systems need to be aware of Legionnaires' disease and handle any concerns about it," says Rick Hill, facilities director at Arkansas Surgical Hospital, a physician-owned hospital specializing in joint and spine surgery in central Arkansas. "There have to be good procedures in place to prevent or control it." The hospital has always been at the forefront when it comes to the health and safety of its staff and patients. In fact, it boasts a low infection rate of less than .3 percent, compared to a national average of more than 3 percent among North American hospitals. So, when Steve Keen, president of Powers of Arkansas, the HVAC contrac- tor responsible for the hospital project, recommended an advanced cooling tower made with unique antimicrobial properties that could greatly reduce the risk of propagation of deadly pathogens, the hospital jumped at the opportunity. "Legionella is always a concern for HVAC systems using a cooling tower and anywhere you have water exposed to the atmosphere," said Keen. "The Delta Cooling towers' antimicrobial properties will help prevent that type of growth and exposure." Delta Cooling Towers, which pioneered the high-density polyethyl- ene plastic cooling tower in the 1970s, recently introduced a line of towers constructed of antimicrobial resin, which is fully compounded into the base cooling tower structural material and casing. The cooling tower fill and drift eliminator are also made from antimicrobial PVC. The antimicrobial resin contains wide-spectrum additives that operate on a cellular level to continuously dis- rupt and prevent uncontrolled growth of microorganisms and biofilm within the cooling tower. Efficacy tests were performed by Special Pathogens Labo- ratory, The Legionella Experts. Cooling tower design and materials can be very significant in the preven- tion of pathogen growth. To avoid problems of stagnant water leading to pathogen growth, experts recommend cooling tower designs feature a sloped basin and/or basin sweeper system. REDUCING COSTS AND MAINTENANCE The best water treatments for Legio- nella prevention are oxidizing bio- cides, which react aggressively toward metal surfaces, effectively attacking metal-clad cooling towers and severely shortening service life. However, because Delta's cooling tower fills and shells are constructed of antimicrobial plastic, they are virtually impervious to corrosive water treat- ments and also minimize the risk of microbial growth. According to Hill, he considered a metal cooling tower, but ultimately decided it would be too difficult to maintain. "Maintaining a metal cooling tower is more work than we wanted and the units have a shorter lifecycle because metal will rust and require mending and repair," said Hill. In addition to the antimicrobial properties of the new advanced anti- microbial cooling tower, the hospital is also significantly reducing energy costs, which was an added benefit. "Our previous air-cooled HVAC sys- tem required a lot of electricity," added Hill. "With the water-based cooling tower and very efficient chiller, howev- er, we expect to save tens of thousands of dollars annually in energy costs." Also, since the engineered molded plastic cooling towers are one piece, there are no problems with seams, welds and patches that wear prema- turely. Therefore, the plastic models offer extended longevity and require far less downtime for cleaning, repair or replacement. "In terms of lifecycle, the Delta Cool- ing tower has a 20-year warranty on construction," concludes Hill. "You don't get that with a metal cooling tower." CHECK OR CIRCLE #175 Hospitals heed warning, seek new antimicrobial options cooling towers/ case study HVACPproducts.com Spring 2018 \ HVAC & Plumbing Product News 31

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