Silver ions and nanoparticles can reduce the amount of bacteria, and some fungi and viruses, in water. Silver ions bind to the cell membrane and prevent DNA replication, killing the microbe. However, silver should not be used as a primary method of water purification, but always in conjunction with another method, such as carbon or ceramic filtration.
We need clean water to lead not only healthy lives but also to remain safe from water-borne diseases. One method is to purify water through the use of silver. While it might seem complicated, using silver to purify water is quite simple.
If you are concerned your water contains bacteria and might be unfit for drinking, and are considering using silver, read on to find out what form of silver is best, how silver purifies water, and what products to consider for home use.
How Silver Purifies Water
Silver is bacteriostatic, which means it prevents bacteria from growing and reproducing.
Researchers found that silver inhibits bacteria DNA from replicatingREF1, which prevents the bacteria from reproducing, and reduces the size of bacteria populations in water.
It is these antibacterial or antimicrobial properties that has seen water purification systems begin to use silver to control bacterial and algae growth.
Commercial water filters also use silver nanoparticles (particles between 1 and 100 nanometers in diameter) combined with activated carbon to control bacteria.
It is well known that while activated carbon effectively removes many contaminants, it does not kill bacteria. By combining silver with carbon filters, bacteria are also removed from water.
There are two main types of silver used to purify drinking water:
- Silver ions / ionic silver
- Silver nanoparticles
Silver ions
Silver ions are usually made from silver salts, such as silver nitrate or silver chloride, or produced chemically. Ionic silver has been shown to successfully reduce many bacteria in water, including:
- Legionella pneumophila
- Pseudomonas aeruginosa
- Escherichia coli (E. Coli)
- Stenotrophomonas maltophilia
- Acinetobacter baumannii
Water Purification Guide has more information on water filter pitchers that can remove bacteria available here.
Silver nanoparticles
Silver nanoparticles can come in a range of forms, such as resin beads, or used to coat or impregnate different surfaces, such as polyurethane foam, fibreglass or ceramics.
Silver nanoparticles are equally successful at reducing bacteria in water, including:
- Pseudomonas aeruginosa
- Escherichia coli (E. Coli)
- Bacillus subtilis
- Staphylococcus aureus
- Enterococcus faecalis
But these two types of silver essentially purify water in the same way – by killing microbes.
Water Purification Systems with Silver
Ionic silver and silver nanoparticles are used in water purification systems with:
- Activated carbon filters (granular and powdered carbon)
OR
- Ceramic filters
Carbon filters
Carbon filters that use silver can be found in faucet-filters, water filter pitchers, refrigerator filters and reverse osmosis systems.
Activated carbon filters are very effective at removing contaminants such as heavy metals, and also provide tiny pore spaces for bacteria to attach to, but it does not kill them. The silver impregnated into the filter will kill the bacteria, making the water safe for drinking.
It is important to know that carbon filters that don’t have silver have been shown to actually INCREASE the amount of bacteria in water. This is because the filter can provide a perfect breeding ground for them. Investing in a filter that also contains silver is the perfect way to avoid this issue, and to improve the quality of your drinking water.
Ceramic filters
Ceramic filters often use silver nanoparticles, and typically comprise two containers. The upper container, made of ceramic, filters the water that passes through, by using tiny holes to help filter out dirt, debris, chemicals, and even bacteria.
Silver nanoparticles that are impregnated into the ceramic, or coated on the ceramic, then help kill off the pathogens and bacteria in the water. Silver is added when mixing the various components of ceramic and before it is heated to harden it.
During filtration, water passes through the ceramic filter into a second container. It is generally advised not to drink the water collected the first time the filter is used, but to discard it.
Instead, refill the filter and use the new water after the initial filtration. This ensures much cleaner and safer water, as any loose particles from transport or installation will be removed in the initial filtration.
Does silver kill bacteria in water?
Silver kills bacteria, fungi, and certain viruses present in the water.
Silver is able to
- Interact with the proteins in the cell membranes of bacteria, compromising their functionality
- Penetrate bacteria cells and damage their DNA
- Bind to the surface of bacteria, changing the cell membranes properties
Silver ions can even breach the bacteria’s cell membrane and are able to STOP cell division. This prevents the bacteria from reproducing and populating.
In fact, silver ions can even attack or block the respiratory system of bacteria, ultimately, causing the cell membranes to burst and the bacteria to die.
How Much Silver Do You Need To Disinfect Water
Silver should only be used to disinfect water when used in conjunction with a water purification system, such as carbon filters or ceramic filters, or in the form of water purification tablets in cases of emergency or travel. Colloidal silver should never be used to disinfect water.
Since your water filter or purifier is already impregnated or coated with silver you should never add silver yourself to disinfect water.
Excessive silver is deposited in body organs, including the liver, kidneys, brain, muscle, spleen, and skin. This can cause argyria (bluish skin).
Colloidal silver can also affect drug absorption making medication less effective and can thus prolong sickness.
According to the United States Environmental Protection Agency (EPA), your silver intake should not go past 5 micrograms per kg of body weight.
As per the World Health Organization (WHO), the safe silver concentrations that can be tolerated by our bodies without risk of adverse health issues is 0.1mg/L.
In cases of emergency or travel, silver-based water purifying tablets can be used. Katadyn Micropur Classic MC Tablets, are a good option and expires after a whopping 10 years, with each tablet coming individually wrapped.
Can Colloidal Silver Purify (disinfect) Water?
Colloidal silver is silver nanoparticles (tiny particles) suspended in a liquid. It is the form of silver frequently sold as a dietary supplement or homeopathic remedy. However, there is no scientific evidence to support the use of colloidal silver as a supplement, and the WHO considers it ineffective against the reduction of bacteria and viruses in water.
References:
Ref 1: 110. Feng Q.L., Wu J., Chen G.Q., Cui F.Z., Kim T.N., Kim J.O. A mechanistic study of the antibacterial effect of silver ions on escherichia coli and staphylococcus aureus. J. Biomed. Mater. Res. 2000;52:662–668. doi: 10.1002/1097-4636(20001215)52:4<662::AID-JBM10>3.0.CO;2-3. [PubMed]
