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Disinfectants Copper-Silver ionization

Most metals such as copper and silver can be used for water disinfection, if they are ionized. Both copper and silver have been applied for centuries because of their biocidal mechanism. Most anti-fouling paints contain copper, reducing the number of marine species growing on the walls of ships. Because of this measure, ships can reach their destination faster.

How are copper-silver ions produced?

Copper-silver ionization is brought about by electrolysis. An electric current is created through copper-silver, causing positively charged copper and silver ions to form.
Copper-silver ionization liberates an ion; an electrically charged atom, has a positive charge when it gives up an electron and a negative charge when it takes up an electron. During ionization, atoms turn into cations or anions. When copper-silver ionization is applied, positively charged copper (Cu+ and Cu2+) and silver (Ag+) ions are formed.
The electrodes are placed close together. The water that is disinfected flows past the electrodes. An electric current is created, causing the outer atoms of the electrodes to lose an electron and become positively charged. The larger part of the ions flows away through the water, before reaching the opposite electrode. The ion concentration is determined by the water flow and amount of electrical current applied to the electrodes. When copper ions (Cu+) dissolve in water, they are oxidized immediately to form Cu2+ ions. Copper can be found in the water in free form. It is commonly bond to water particles. Ions are unstable in water, unless a stabilizing ligand is present, or unless they combine in a cluster to form nanoparticles which are negatively charged.

What are the applications of copper-silver ionization?

Copper-silver ionization became of interest when NASA used copper-silver ionization for drinking water prodcution aboard Apollo space ships in 1960. Because of copper-silver ionization, drinking water could be produced safely in space without the use of chlorine, which causes cancer..

In England, copper-silver ionization is applied in about 120 hospitals successfully for the deactivation of Legionella bacteria.
In the United States, copper-silver ionization is mainly used for swimming pool water disinfection. Copper-silver is often used to limit disinfection byproducts formation during chlorine disinfection.
Because of its specific properties, copper-silver ionization is very suitable for fishpond disinfection. Copper-silver ionization is not dependent on temperatures. It is active in the entire water system.
Copper-silver ionization is used by water bottling companies and companies that recycle water throughout the United States.

What is the disinfection mechanism of copper-silver ionization?

Electrically charged copper ions (Cu2+) in the water search for particles of opposite polarity, such as bacteria, viruses and fungi. Positively charged copper ions form electrostatic compounds with negatively charged cell walls of microorganisms. These compounds disturb cell wall permeability and cause nutrient uptake to fail. Copper ions penetrate the cell wall and as a result they will create an entrance for silver ions (Ag+). These penetrate the core of the microorganism. Silver ions bond to various parts of the cell, such as the DNA and RNA, cellular proteins and respiratory enzymes, causing all life support systems in the microbe to be immobilized. As a result, there is no more cellular growth or cell division, causing bacteria to no longer multiply and eventually die out. The ions remain active until they are absorbed by a microorganism.

What are the disinfection applications of copper-silver ionization?

Swimming pools and copper-silver ionization

In the United States, copper-silver ionization is applied as an alternative for chlorine disinfection. Chlorine use in swimming pools and hot tubs can be reduced by over 80%.

Cooling towers and copper-silver ionization

Copper-silver ionization is commonly used to kill Legionella bacteria in cooling towers.

Legionella in hospitals and nursing homes and copper-silver ionization

Copper-silver ionization is applied in hospitals and nursing homes to prevent the distribution of Legionella bacteria. The main source of Legionella distribution is the warm water system. Circumstances in warm water systems are ideal for Legionella bacteria to grow and multiply. Contagion mainly takes place through inhalation of shower steam. Copper-silver ionization can sufficiently kill Legionella bacteria.

Drinking water and copper-silver ionization

In the United States, several drinking water production companies use copper-silver ionization as an alternative for chlorine disinfection and to prevent the formation of disinfection byproducts. The standard for trihalomethanes was decreased by EPA from 100 to 80 µg/L.  When copper-silver ionization is combined with chlorine disinfection, it is an excellent disinfection mechanism to deactivate viruses and bacteria.

What are the terms of copper-silver ionization?

Firstly, the concentration of copper and silver ions in the water should be sufficient. The required concentration is determined by the water flow, the volume of water in the system, the conductivity of the water and the present concentration of microorganisms.
Secondly, the electrodes should be in good condition. When the water is hard or fouling takes place as a consequence of water hardness and quality, there will be a decrease in electrode release and the additional effect will decrease. By using pure silver and pure copper, the supply of copper and silver ions can be regulated separately. These electrodes suffer from less limestone formation and fouling.
Thirdly, the affectivity of copper-silver ionization depends on the pH value of the water. When pH values are high (alkaline), copper ions are less effective. When the pH value exceeds 6, insoluble copper complexes will precipitate. When the pH value is 5, copper ions mainly exist as Cu(HCO3)+; when the pH value is 7 as Cu(CO3) and when the pH values is 9 as Cu(CO3)22-.
Fourthly, copper-silver ionization affectivity is determined by the presence of chlorine. Chlorine causes silverchlorine complex formation. When this occurs, silver ions are no longer available for disinfection.

How effective is copper-silver ionization?

Copper-silver ionization can deactivate Legionella bacteria and other microorganisms in slow-running water and still water. Legionella bacteria are very susceptive to copper-silver ionization. Copper-silver ionization also takes care of bio film. Copper remains within the bio film, causing a residual effect.
It appears that copper-silver ionization additon causes the number of Legionella bacteria to diminish. After a short period of time, however, the number of Legionella bacteria will rise again because they can also be found in the bio film. Copper that stays behind in the bio film takes care of these bacteria. When copper and silver ions are added to water constantly, the concentration of Legionella bacteria remains low.
The deactivation rate of copper-silver ionization is lower than that of ozone or UV. A benefit of copper-silver ionization is that ions remain in the water for a long period of time. This causes long-term disinfection and protection from recomtamination. Copper and silver ions remain in the water untill they precipitate or absorb to bacteria or algae, and are removed from water by filtration after that.

What are the benefits and drawbacks of copper-silver ionization?


Copper-silver ionization affectively deactivates Legionella bacteria and bio film and it improves water quality. Copper-silver ionization has a larger residual effect than most other disinfectants. Copper and silver ions remain in the water for a long period of time. Because of its local affectivity, the effect is larger than that of UV. Copper-silver is effective throughout the entire water system, even in dead-end points and parts of the system that contain slow-running water. Copper-silver use affectivity does not depend on water temperature. When copper-silver is used, less maintenance to the water system is required. Copper-silver is non-corrosive; it causes less strain on the distribution system. Because of a decrease in the use of chemicals, the lids and pumps are not affected. Furthermore, shower heads, tanks and taps are not contaminated. When copper-silver ionization is applied, there are no transport and storage difficulties.

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