Examining the efficacy of copper‐silver ionization for management of Legionella: Recommendations for optimal use

Abstract

Although copper‐silver ionization (CSI) has been used for 30 years to inactivate Legionella bacteria and other opportunistic pathogens in water, the literature is a mix of both successes and failures. This paper reviews the technology and case studies to help improve the success of CSI installations. Important is a properly designed system capable of consistent delivery of copper/silver ions at their target levels. However, even the most advanced system will fail if not properly operated and maintained. Water chemistry can impact the performance of CSI systems and attention should be on conductivity, temperature, oxygen, flow, pH, chloride, sulfate, alkalinity, hardness, phosphate and dissolved organic carbon levels. Several case studies are provided to demonstrate the effectiveness of CSI treatment even at high pH levels. The report concludes that the use of CSI to control Legionella and other opportunistic pathogens is highly effective when the units are properly designed, maintained, and operated.

Moving beyond silver in point-of-use drinking water pathogen control

“…Another is that copper and silver ion concentration fluctuations lead to insufficient inactivation of L. pneumophila allowing for regrowth. 54 To date, the mechanism(s) underlying silver ion resistance in many DWPIs is unknown. Possible non-specific heavy metal efflux pumps, similar to that seen for copper resistance, 56 could be present within L. pneumophila and other DWPIs.…”

“…51 However, studies on CSI report an initial decrease followed by an increase in the number of culturable Legionella (over varying time periods) before returning to pre-installation concentrations. 52 One explanation for this observation is the emergence of resistance due to consistent, sub-lethal exposure to copper and silver 53 (sub-lethal due to poor transport through biofilms, 54 poor building plumbing hydraulics, 55 or pH influences on ion release). Another is that copper and silver ion concentration fluctuations lead to insufficient inactivation of L. pneumophila allowing for regrowth.…”

“…Another is that copper and silver ion concentration fluctuations lead to insufficient inactivation of L. pneumophila allowing for regrowth. 54…”