Active Carbon is pretty miraculous in terms of it’s abilities to remove toxins, odor and bad taste from tap water. But understanding how and when it works can be complicated and confusing.
Here’s a simple overview.
How does it work?
Activated carbon filters are small pieces of carbon, in granular or block form, that have been treated to be extremely porous. Just one gram of activated carbon can easily have a surface area of 5k-30k square feet. It’s the surface area that allows active carbon filters to be very effective in adsorbing (essentially removing) contaminants and other substances.
In addition to the surface area active carbon filters have different capabilities in terms of the size of contaminants they remove. These range from around 50 microns to 0.5 microns. The smaller the more effective.
When the water flows through active carbon filters the chemicals stick to the carbon resulting in purer water output. The effectiveness depends on the flow and temperature of the water. Therefore most smaller active carbon filters should be used with low pressure and cold water.
Activated carbon is usually made of coconut shells, wood or coal and sold as granular activated carbon or carbon blocks.
What does active carbon filters remove and reduce?
Active carbon is very effective in removing at least 81 chemicals, effective in another 30 and moderately effective for 22. However, it doesn’t remove everything from the tap water. For complete lists see links below in sources.
According to EPA (the Environmental Protection Agency in the United States) Activated Carbon is the only filter recommended to remove all 32 identified organic contaminants including THMs. The same is true for all 14 listed pesticides and 12 herbicides.
But understanding water contaminants can be difficult. Therefore it’s easier to focus on specific problems that your tap water may encounter.
Potable (approved for drinking) tap water
Most public tap water in North America is highly regulated, tested and certified for drinking. However, to reach this goal, and disinfect water from pathogens, chlorine is added. Unfortunately, Chlorine may make water taste and/or smell bad. Activated Carbon filters are excellent at removing chlorine and its byproducts, as well as removing the taste and odor associated with it.
Chlorine and by-products
The most common concern about tap water is by-products (VOCs) from chlorine such as TTHMs that are identified as potentially cancerous. Activated carbon is very effective in removing these.
What Activated Carbon doesn’t filter
Despite the 80+ contaminants Activated Carbon filters, there is also some content it doesn’t remove
- Dissolved solids including minerals, salts or metals such as iron that are not considered contaminants
- 3 out of 4 microbiological contaminants incl cysts, coliform and bacteria
- Inorganic contaminants such as lead, arsenic and asbestos
- Radionuclides although these are reduced
Activated carbon generally does not reduce TDS (Total Dissolved Solids) which is a common measure used by water filter salespeople. Read our separate blog about TDS and minerals in tap water.
More specifically activated carbon is usually not sufficient for removal of the following substances.
In areas and buildings with soft water and old pipes, there can be a risk of lead in tap water. Granulated activated carbon (G.A.C) is not effective in removing lead but Carbon Block filters such as TAPP 2 remove lead very effectively.
This is one of the most common drinking water issues in less developed countries. Especially for waterborne gastrointestinal diseases (e.g. diarrhea that visitors not used to the local water get). Activated carbon filters are generally not sufficient to remove such contaminants. Carbon block filters with dense pores (under 2micron) such as TAPP 2 – do filter out Cryptosporidium, often present in raw water.
Common in some places where the groundwater has been contaminated. Activated Carbon removes 30-70% of arsenic but is not sufficient in places where this is highlighted as a real problem.
If your local water contains one or more of these substances then you should ensure that the filter reduces them to a safe level. Most of the time this means combining activated carbon with other types of filters such as Ion Exchange. Read more about the best filtering technologies.
Activated Carbon is a brilliant technology for water filtering and solves many issues but not all. Therefore it’s important to understand the capabilities and limitations and in case of uncertainty feel free to contact us with your questions.
How Activated Carbon adsorption works – http://www.lenntech.com/library/adsorption/adsorption.htm
What does Activated Carbon remove – https://iaspub.epa.gov/tdb/pages/treatment/treatmentOverview.do?treatmentProcessId=2074826383
How does Granular Activated Carbon Work – http://www.health.state.mn.us/divs/eh/hazardous/topics/gac.html
What does Activated Carbon remove http://www.purewaterproducts.com/articles/carbon
Microbiological contaminants – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4372141/