David M. Dziewulski, Erin Ingles, Neculai Codru, John Strepelis, Dianna Schoonmaker-Bopp
Elsevier, American Journal of Infection Control, July 2015
This study examined two healthcare facilities using copper-silver ionization to control Legionella in alkaline water conditions. One facility was an acute care facility with a pH range of 8.7-9.9. The other was a long-term care facility with a pH range of 8.9-9.7. Both had previously used disinfection methods without success, including superheat-and-flush, hyperchlorination, and chlorine dioxide.
Acute care facility
The acute care facility reported six cases of Legionnaires’ disease before installing the copper-silver ionization system. After installation, the Legionella positivity rate (percentage of test sites within the building positive for Legionella) was reduced to 0%.
- After chlorine dioxide treatment: Legionella positivity rate varied from 22-100% throughout treatment and never reached 0%
- After copper-silver ionization treatment: Legionella positivity rate reduced from 30% to 0%
Long-term care facility
The long-term care facility reported two Legionnaires’ cases before installing the copper-silver ionization system. During the early stages of treatment, instabilities in both copper and silver concentrations occurred and were attributed to electrode scaling. This was followed by an increase in Legionella. Once ion concentrations were stabilized, the Legionella positivity rate was reduced to 0%.
- After hyperchlorination treatment: Legionella positivity rate reduced from 43% to 10%
- After copper-silver ionization treatment: Legionella positivity rate reduced from 10% to 0%
Copper-silver ionization successfully controlled Legionella under alkaline water conditions but required frequent monitoring and system adjustments to maintain efficacy.
The study found that alkaline water conditions reduce copper ion concentrations, however, the facilities were able to achieve non-detect as silver ions were less impacted and appeared to be the main ion controlling Legionella.