Top-Flight Army Hospital Benefits from "Green" Chemical Treatment
of Heating/Cooling Systems

Brooke Army Medical Center's Amputee Care Center opened in 2005 to treat soldiers injured in Iraq and Afghanistan. Photo courtesy of Brooke Army Medical Center.

Brooke Army Medical Center (BAMC) is a teaching hospital occupying 1.5 million square feet at Fort Sam Houston Army base in San Antonio. Licensed as a level-one trauma unit, the hospital serves up to 450 patients, including 48 who need intensive care. The center is renowned for its 40-bed burn unit—the only one of its kind serving American military personnel.

Adding to its unique status among military hospitals is a fairly new Amputee Care Center—the second to be created after the Walter Reed Army Medical Center in Washington—for soldiers who lose limbs during combat in Iraq and Afghanistan.

Institutions such as BAMC rely on efficient and well-maintained heating and cooling systems, especially during San Antonio's relentlessly hot summers. (The city's average high temperature during July and August is 95º F.) The hospital has a 6,000-ton cooling tower that is much larger than the average 500-1,200-ton units found on many other Army bases. To air condition the hospital, water and air flow through the cooling tower, where evaporation cools the water, keeping the hospital cool and comfortably safe.

In July 2005 the Corps of Engineers and contractor Garratt-Callahan began a two-pronged effort to help Army maintenance teams improve their ongoing battle against corrosion and microorganisms that foul and infect cooling and heating systems. These problems threaten human health, damage equipment, and increase energy consumption. At BAMC and four other Army facilities, the Corps introduced green chemicals for heating and cooling systems that are effective and safer for the environment. They also installed "smart" control systems to efficiently feed the chemicals into the systems.

The projects were funded using 2.6 million from the Army's Installation Management Agency and the Pentagon-based Corrosion Policy and Oversight Office. Besides using those dollars at BAMC, the Corps of Engineers treated 11 cooling towers at Fort Hood near Killeen, TX; seven cooling towers at Fort Rucker, AL; and three cooling towers at the Army's Redstone Missile Arsenal in Huntsville, AL. Both boilers and cooling towers benefited from Army/DoD project funds at the Red River Army Depot in Texarkana, TX, where the Army maintains and repairs ground combat equipment and tactical systems.

A Matter of Life and Death

"In the burn ward at BAMC temperature and humidity are critical," said Drozdz, a chemist and project leader at the Army's Construction Engineering Research Laboratory (CERL) in Champaign, IL, part of the Engineer Research and Development Center. The biggest threats to keeping these levels constant are corrosion and the build-up of scale and algae, and potentially harmful bacteria such as legionella premophilia, which causes the sometimes fatal Legionnaires' disease.

Brooke Army Medical Center's heating and cooling plant has benefited from "green" chemical treatments and new smart monitoring systems. Photo courtesy of Garratt-Callahan.

At the hospital an effective, well-managed water-treatment program is vital. It minimizes water and energy consumption, reduces corrosion, and extends equipment life, Drozdz explained. Such programs require good data tracking and reporting, and, in turn, yield significant savings, enabling heating, ventilating, and air-conditioning (HVAC) systems to use energy, water, and chemicals more efficiently. The BAMC approach provides continuous corrosion monitoring and supports the regular chemical program with a supplemental application of corrosion inhibitors on an "as-needed" basis, Drozdz said.

"At Brooke, we're using THPS—short for tetrakis hydroxymethyl phosphonium sulfate—a green biocide chemical that, when properly applied, does an excellent job of combating aerobic and anaerobic bacteria," Drozdz said. "Because THPS doesn't work as well on algae, we have to alternate the green chemical with an oxidizing biocide such as chlorine to help control the algae."

The water supply BAMC depends on for cooling and heating presents another challenge as well. BAMC uses gray water to supply its heating, cooling, and irrigation needs. It comes in with higher levels of phosphates and lower chlorine levels than potable water, Drozdz said. "We must add more chlorine, which is corrosive to copper, so we have to pay particular attention to maintaining the proper level of the copper corrosion inhibitor." As more and more HVAC facilities are required to use gray water that needs continuous chlorination, the risk of corrosion to cooling systems will rise.

Protecting Heat-Exchange Equipment and Patient Care

Should corrosion, scale, or biological growth foul cooling or boiler heat-exchange equipment at BAMC, it can adversely affect patient health and treatment. "The boilers are also used for autoclaves to sterilize the surgical instruments, so a high-quality steam is very important for the sterile conditions in the operating room." Damage to boilers may cause interruptions in heating, making operations less reliable, less efficient and possibly endangering patient care, Drozdz said. "Reduced heat transfer in boilers and condensers and component failures can also occur, resulting in increased energy consumption and premature replacement of equipment."

To prevent these problems from happening, equipment operators at the hospital treat boiler feed water with chemicals that are less toxic and that provide scale and corrosion protection to boiler tubes, steam lines, and auxiliary equipment components.

Under the current project, Army maintenance teams are also treating microbiological growth in the boilers using biocides to kill bacteria. They have also introduced phosphonates and new polymers to inhibit scale within the boilers. These chemical formulations are less toxic, biodegradable (while producing nontoxic byproducts), safer for human-handling, and cheaper to dispose of. "With these chemicals and a system that efficiently controls chemical usage, any negative impact on the environment is minimal," Drozdz said.

Besides greener chemicals, the heating at BAMC also benefits from a system that improves how regularly and efficiently the chemicals are dispensed. "The control system also reduces the need for people to manually handle chemicals, which is safer," she added. "By using better chemicals and application equipment, we're able to better control the temperature in the hospital and create a safe environment for the patients," Drozdz said.

For the Corps of Engineers, ensuring that the Army's heating and cooling systems are well treated can be a matter of life and death. "The reliable operation of these plants is vital, not only for hospital safety and controlling energy use, but for the welfare of soldiers, their families, and the staff who treat them when they return from combat," Drozdz said.

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