Pilot-scale assessment reveals effects of anode type and orthophosphate in governing antimicrobial capacity of copper for Legionella pneumophila control.
Water Res
; 242: 120178, 2023 Aug 15.
Article
em En
| MEDLINE
| ID: mdl-37307684
ABSTRACT
Copper (Cu) is sometimes applied as an antimicrobial for controlling Legionella in hot water plumbing systems, but its efficacy is inconsistent. Here we examined the effects of Cu (0 - 2 mg/L), orthophosphate corrosion inhibitor (0 or 3 mg/L as phosphate), and water heater anodes (aluminum, magnesium, and powered anodes) on both bulk water and biofilm-associated L. pneumophila in pilot-scale water heater systems. Soluble, but not total, Cu was a good predictor of antimicrobial capacity of Cu. Even after months of exposure to very high Cu levels (>1.2 mg/L) and low pH (<7), which increases solubility and enhances bioavailability of Cu, culturable L. pneumophila was only reduced by â¼1-log. Cu antimicrobial capacity was shown to be limited by various factors, including binding of Cu ions by aluminum hydroxide precipitates released from corrosion of aluminum anodes, higher pH due to magnesium anode corrosion, and high Cu tolerance of the outbreak-associated L. pneumophila strain that was inoculated into the systems. L. pneumophila numbers were also higher in several instances when Cu was dosed together with orthophosphate (e.g., with an Al anode), revealing at least one scenario where high levels of total Cu appeared to stimulate Legionella. The controlled, pilot-scale nature of this study provides new understanding of the limitations of Cu as an antimicrobial in real-world plumbing systems.
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Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Legionella
/
Legionella pneumophila
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Anti-Infecciosos
Idioma:
En
Ano de publicação:
2023
Tipo de documento:
Article