Copper-silver ionization at a US hospital: Interaction of treated drinking water with plumbing materials, aesthetics and other considerations

Abstract

Tap water sampling and surface analysis of copper pipe/bathroom porcelain were performed to explore the fate of copper and silver during the first nine months of copper-silver ionization (CSI) applied to cold and hot water at a hospital in Cincinnati, Ohio. Ions dosed by CSI into the water at its point of entry to the hospital were inadvertently removed from hot water by a cation-exchange softener in one building (average removal of 72% copper and 51% silver). Copper at the tap was replenished from corrosion of the building's copper pipes but was typically unable to reach 200 μg/L in first-draw and flushed hot and cold water samples. Cold water lines had >20 μg/L silver at most of the taps that were sampled, which further increased after flushing. However, silver plating onto copper pipe surfaces (in the cold water line but particularly in the hot water line) prevented reaching 20 μg/L silver in cold and/or hot water of some taps. Aesthetically displeasing purple/grey stains in bathroom porcelain were attributed to chlorargyrite [AgCl(s)], an insoluble precipitate that formed when CSI-dosed Ag(+) ions combined with Cl(-) ions that were present in the incoming water. Overall, CSI aims to control Legionella bacteria in drinking water, but plumbing material interactions, aesthetics and other implications also deserve consideration to holistically evaluate in-building drinking water disinfection.

Interactive Effects of Copper Pipe, Stagnation, Corrosion Control, and Disinfectant Residual Influenced Reduction of Legionella pneumophila during Simulations of the Flint Water Crisis

“…Comparing copper versus PEX pipe materials further illustrated the potential for premise plumbing conditions to mediate the effects of the distribution system water chemistry. Copper is of particular interest because of its known antimicrobial properties towards L. pneumophila [ 28 , 39 , 40 , 41 ]. Ironically, the lack of corrosion control, which triggered higher iron and lower chlorine residuals and exacerbated Legionella problems in some portions of the Flint distribution system during the crisis [ 3 ], also released high levels of copper that might have helped to control Legionella growth in some buildings and homes.…”

Smartphone-powered efficient water disinfection at the point of use

“…The copper ionization controls the copper ion dosage precisely, relieving the problem of material storage and transportation. Thus, copper ionization systems have been used for disinfection in drinking water, wastewater, hospitals, cooling towers, etc 22,33,46,49,50 . The major obstacle of the conventional copper disinfection is that the dosage for efficient disinfection (>1500 µg L −1 ) brings secondary contamination that is toxic to both the human and the environment 51,52 .…”

Métodos de desinfección del agua y su implicación en la legionelosis

“…Otros estudios sugieren que la ionización cobre-plata no es del todo eficaz frente al desarrollo de la bacteria (Triantafyllidou, Lytle, Muhlen, & Swertfeger, 2016), existiendo una tolerancia a iones plata o que una concentración de ion plata de 3 µg/l es suficiente para controlar el crecimiento de legionellae en el agua caliente en circulación, pero no en determinados puntos críticos de las instalaciones (Kusnetsov, Iivanainen, Elomaa, Zacheus, & Martikainen, 2001); o simplemente que la ionización cobre-plata es una modalidad de desinfección con muchos criterios positivos de evaluación (Stout & Yu, 2003).…”