"Makeup" water is added to replace. what is lost by . quantities of makeup water flowing to the . the switch to ozone treatment, the makeup . | Ozonation of Cooling Tower Water: A Case Study by Stephen Osgood Water Conservation Unit East Bay Municipal Utility District June 1991 Completed under Contract to the California Department of Water Resources Water Conservation Office Ozonation of Cooling Tower Water: A Case Study by Stephen Osgood, Water Conservation Unit East Bay Municipal Utility District Summary In 1988, Providence Hospital in Oakland, California changed the method it uses to treat the water in two cooling towers, replacing a multiple chemical treatment program with ozone gas treatment. As a result, the hospital reduced water use feeding the cooling towers by 13 percent. In addition, after changing the cooling tower water treatment, the hospital: more than doubled the cycles of concentration (based on conductivity), eliminated fouling and scaling of exposed surfaces, experienced no new scaling of exposed surfaces, dramatically improved water clarity, greatly reduced bacteria levels, achieved low corrosion rates, experienced minor pitting and scaling of heat exchange tubes, discovered corrosion of condenser tube end bells, and replaced two fan motors due to corrosion. On the whole, the hospital is pleased with the performance of the ozone system. It values ozone's excellent microbiological control and environmental compatibility. It does not believe there has been any serious destruction of equipment. Consequently, the hospital has not only continued to use ozone in the cooling towers of the main building, it has also recently selected ozone to replace a multiple chemical treatment program at the cooling tower in a second building. The experience at this site suggests that ozone treatment of cooling tower water should be considered at least where the following conditions are met: the cooling water's chief function is to remove heat from medium sized heating, ventilation, and air conditioning (HVAC) systems; the ozone system is well designed, monitored, and maintained: the makeup water quality is
