The main objective of this presentation is to teach the audience that disinfectant residuals in potable water from building water systems with copper-silver ionization secondary disinfection systems may require different sample preservation approaches in order to neutralize copper and silver disinfectant residuals during transit to a laboratory for Legionella testing, and that an EDTA/sodium thiosulfate cocktail will serve this purpose. 

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- Building water samples collected for culture detection of Legionella generally have an added reducing agent, such as sodium thiosulfate, to neutralize chlorine or other halogen disinfectant residuals, in order to prevent bactericidal action from continuing during transit to the laboratory.

-Disinfectant residuals in potable water from building water systems with copper-silver ionization secondary disinfection systems may require different sample preservation approaches in order to neutralize copper and silver disinfectant residuals during transit to a laboratory for Legionella testing.

- Research by Resgalla et al. (Chemosphere 89, 102-107, 2012) has shown that EDTA and sodium thiosulfate will neutralize the toxicity of copper and silver in water, respectively.  We will present our results, adding EDTA + sodium thiosulfate formulas to potable water samples containing copper and silver ions, thus preventing the continuing bactericidal action of Cu and Ag ions during transit and providing a more accurate Legionella culture result.

Richard D. Miller. Ph.D., Environmental Safety Technologies, Inc.

Brandon Smith, University of Louisville, School of Medicine

Water samples collected for culture detection of Legionella generally have an added reducing agent, such as sodium thiosulfate, to neutralize chlorine or other halogen disinfectant residuals, in order to prevent bactericidal action from continuing during transit to the laboratory.  However, disinfectant residuals in potable water from copper-silver ionization secondary disinfection systems may require different sample preservation approaches in order to neutralize copper and silver disinfectant residuals.  Metal chelating agents, such as ethylene-diamine-tetraacetate (EDTA), have been recommended for this purpose.  A study by Resgalla et al. (Chemosphere 89, 102-107, 2012) has shown that EDTA effectively removed metal toxicity of copper in water.  Silver toxicity was not removed by EDTA, but was removed by sodium thiosulfate (at concentrations used for de-chlorination).  However, EDTA chelation of metals does have some anti-bacterial activity at high concentrations.  Thus, the purpose of the present study was to evaluate the ability of EDTA/thiosulfate formulas (at different EDTA concentrations, EDTA salts, and pH not harmful for Legionella), to neutralize the metal toxicity of water from building water systems that are using a Cu/Ag secondary disinfection system. We will present our findings on the addition of such a cocktail to water samples collected for Legionella culture-based validation of control by these Cu/Ag ionization systems, thus preventing the continuing bactericidal action of Cu and Ag ions during transit and providing a more accurate culture result.

Dr. Richard D. Miller has a Ph.D. in microbiology from Penn State University in 1975, followed by two years of post-doctoral microbiology research at Oregon Health Sciences University.  His training has been in infectious diseases microbiology, as well as applied and environmental microbiology.  As a faculty member at the University of Louisville, School of Medicine, and as a co-owner of Environmental Safety Technologies, Inc,  Dr. Miller has worked with Legionella continuously for the past 42 years, including both Legionella published reseach, as well as Legionella testing of building water samples.  He has presented widely on Legionella and other microbiology topics at scientific conferences and professional organization meetings.