Efficacy of copper and silver as residual disinfectants in drinking water

Enue E. Sicairos-Ruelas, Charles P. Gerba, Kelly R. Bright

Research output: Contribution to journalArticle

Abstract

Contamination events and biofilms can decrease the amount of free chlorine available in drinking water systems. The efficacy of 100 μg/L silver and 400 μg/L copper, individually and combined, were evaluated as secondary, longer-lasting residual disinfectants against Salmonella enterica serovar Typhimurium, Escherichia coli, Listeria monocytogenes, and Mycobacterium fortuitum at 24 °C and 4 °C. A >5.0-log 10 reduction was observed in E. coli and L. monocytogenes after three hours and S. Typhimurium following seven hours of exposure to silver. M. fortuitum was the most resistant species to silver (1.11-log 10 after seven hours). Copper did not significantly reduce S. Typhimurium and E. coli at 24 °C; ≥2.80-log 10 reductions were observed in the Gram-positive L. monocytogenes and M. fortuitum. Longer exposure times were required at 4 °C to achieve significant reductions in all species. A synergistic effect was observed when silver and copper were combined at 24 °C. In addition, silver was not affected by the presence of organic matter at concentrations that completely inhibited 0.2 mg/L chlorine. The results of this study suggest that combinations of silver and copper show promise as secondary residual disinfectants. They may also be used in conjunction with low chlorine levels or other disinfectants to provide additional, long-lasting residuals in distribution systems.

Original languageEnglish (US)
Pages (from-to)146-155
Number of pages10
JournalJournal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering
Volume54
Issue number2
DOIs
StatePublished - Jan 28 2019

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Keywords

  • Silver
  • copper
  • disinfectant residual
  • disinfection
  • water distribution system

ASJC Scopus subject areas

  • Environmental Engineering

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