Copper Silver Distribution
"Intermittent Use of Copper-Silver Ionization for
Legionella Control in Water Distribution Systems: A Potential Option in
Buildings Housing Individuals at Low Risk of Infection"
Clinical Infectious Diseases 1998;26:138-40
Zeming Liu, Janet E. Stout, Marcie Boldin, John Rugh, Warren F. Diven,
and Victor L. Yu
From the University of Pittsburgh and Veteran Affairs Medical
Center, Pittsburgh, Pennsylvania.
"One copper-silver ionization system was sequentially
installed onto the hot-water recirculation lines of two hospital
buildings colonized with Legionella pneumophila, serogroup 1. A third
building with the same water supply and also colonized with Legionella
served as a control. Four weeks after activation of the system, distal
site positivity for Legionella in the first test building dropped to
zero. After operating for 16 weeks, the system was disconnected and
installed onto the second test building. Twelve weeks of disinfection
reduced the distal site positivity for Legionella in the second test
building to zero. Legionella recolonization did not occur in the first
test building for 6 - 12 weeks and in the second test building for 8 -
12 weeks after inactivation of the system. The control building
remained Legionella-positive throughout the experimental period. A
significantly higher copper concentration was found in the biofilm
taken from a sampling device than in that from water. This is likely to
be the reason that the copper-silver ionization system had the residual
effect of preventing early recolonization. Our study raises the
possibility that one copper-silver unit could be rotated among several
buildings to maintain a Legionella-free environment. Such an approach
may be cost-effective for buildings housing individuals at low risk for
contracting legionnaires' disease."
"In the first test building, the Legionella positivity was
reduced from 50% (before start-up) to zero after 4 weeks."
Full Study (PDF)