CONTROLLED EVALUATION OF COPPER-SILVER IONIZATION IN ERADICATING LEGIONELLA-PNEUMOPHILA FROM A HOSPITAL WATER DISTRIBUTION-SYSTEM

A controlled evaluation was made of the efficacy of copper-silver ioni zation in eradicating Legionella pneumophila from a hospital water sup ply. Copper-silver ionization units were installed on the hot water re circulation line of one building with water fixtures positive for Legi onella species. Another building with the same water supply served as a control. Legionella species persisted within the system when copper and silver concentrations were <0.3 and <0.03 ppm, respectively. When copper and silver concentrations were >0.4 and >0.04 ppm, respectively , there was a significant decrease in Legionella species colonization, but the percentage of water fixtures positive for organisms was uncha nged in the control building. When the ionization unit was inactivated , water fixtures continued to be free of Legionella species for 2 addi tional months. Copper-silver ionization can eradicate L. pneumophila i n a water distribution system. The advantages of copper-silver ionizat ion include relatively low cost, straightforward installation, easy ma intenance, nontoxic by-products, and the presence of a disinfecting re sidual.