Innovative Electrodes to Control Trace Metal Ionization Used to Treat Pathogens in Water Distribution Systems

摘要

The control of hazardous pathogens in water distribution systems, is a priority for health authorities world wide. An estimated 8,000-18,000 people get Legionnaires' disease in the United States each year. Hospitals, hotels, old people's homes, prisons and ships are high risk environments due to the nature of the water distribution system. Treatment is essential, and one of the most effective methods is copper-silver ionization. The positively charged copper and silver ions thus released, form electrostatic bonds with negatively charged sites on bacterial cell walls; this leads to cell lysis and cell death. The amount of copper and silver must remain within a certain range for efficiency, and at the same time remain well below the WHO and other guidelines. High oral intake of copper and silver can result in liver failure and argyria (blue-bluish grey discoloration of the skin) for copper and silver respectively. Recommended values for copper are between 0.3 and 0.5 mg L~(-1) and, for silver, between 0.03 and 0.05 mg L~(-1). Currently there is no method available (outside the laboratory) to monitor copper and silver concentrations on-site at a ppb level. The specific aim of this work was to study the electrochemical behaviour of screen-printed graphite electrodes in the determination of silver and copper, with the final purpose of development and construction of mercury-free electrodes to be used in the determination of silver and copper concentrations in water samples by anodic stripping voltammetry.