Microbiological evaluation of copper: Silver disinfection units for use in swimming pools

The bactericidal effects of electrolytically generated copper:silver ions on pathogenic bacteria of concern in swimming pools, hot tubs and cooling towers were evaluated in disinfection experiments. Copper:silver ion concentrations generated in well water were 400:40 μg/L, respectively. Pure cultures of Legionella pneumophila, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Streptococcus faecalis, were individually tested in water containing copper:silver ions alone, copper:silver ions with free chlorine, and free chlorine alone. Greater numbers of organisms were killed after exposure to copper:silver ions with 0.2 mg/L free chlorine than in either the copper:silver ions or free chlorine alone. L. pneumophila showed greater than a 5 log₁₀ reduction in numbers after 7 minutes exposure to copper:silver ions with 0.2 mg/L free chlorine. In comparison, less than a 2 log₁₀ decrease was obtained after exposure to free chlorine alone. E. coli numbers decreased over 4 log₁₀ after 1 minute exposure to copper:silver ions with 0.2 mg/L free chlorine and less than a 3 log₁₀ decrease after exposure to free chlorine alone. The majority of the other organisms tested showed the same effect. Electrolytically generated copper:silver ions with low levels of free chlorine appear to have greater bactericidal activities than either disinfectant alone.