Active Carbon is pretty miraculous in terms of it’s abilities to remove contaminants, odor and bad taste from tap water. But how does it work, what does it remove and do you need an activated carbon water filter?
We explore the topics based on the facts available.
How does activated carbon remove contaminants?
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 has a surface area of 5,000-30,000 square feet. 4 grams is the equivalent of a football field. It’s the massive 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. Activated carbon filters range from around 50 microns to 0.5 microns. The smaller the more effective but smaller pores also may reduce water flow.
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. In reality it’s a lot more but these are chemicals that have been thoroughly tested.
There are also contaminants that active carbon doesn’t remove which we will cover below. For a 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 (by-products from chlorine). The same is true for all 14 listed pesticides and 12 herbicides. This includes nitrates as well as pesticides such as glyphosate (also referred to as roundup)
Understanding water contaminants can be difficult. Therefore it’s easier to focus on the specific contaminants in your tap water.
Most public tap water in Europe and North America is highly regulated, tested and certified for drinking. However, to make it safe, chlorine is added which may make it taste and smell bad. Activated Carbon filters are excellent at removing chlorine and related poor taste and odor. High quality activated carbon filters can remove 95% or more of the chlorine.
For more details on this read about total and free chlorine.
Chlorine should not be confused with Chloride which is a mineral combined by sodium and calcium. Chloride may actually increase slightly when the water is filtered with activated carbon.
The most common concern about tap water is by-products (VOCs) from chlorine such as THMs that are identified as potentially cancerous. Activated carbon is more effective than any other filter technology in removing these.
Special Activated Carbon Filters
In addition to the standard contaminants removed by charcoal filters there are additional things that can be removed with high quality carbon block filters such as TAPP 2.
- 95% or more of Chloramine
- 95% or more of lead, mercury and zinc with catalytic activated carbon
- 100% of microplastics
By adding Ion Exchange and/or ultrafiltration layers it’s possible to remove further content including calcium (limescale) and pathogens (bacteria, coliform and viruses).
What Activated Carbon doesn’t filter
Despite the 80+ contaminants Activated Carbon filters there is also some materials it doesn’t remove
- Dissolved solids including minerals, salts or metals such as iron that are not considered contaminants (this means TDS does not reduce with activated carbon)
- Most microbiological contaminants incl cysts, coliform and bacteria
- Inorganic contaminants such as arsenic and asbestos
- Radionuclides although these are reduced
Note: Some carbon block filters made of activated carbon such as TAPP 2 are specially designed to remove coliform and lead.
Activated carbon water filters generally does not reduce minerals or TDS (Total Dissolved Solids) which is a common measure used by water filter sales people. Read our separate blog about TDS and minerals in tap water.
More specifically charcoal filters may not be sufficient in removing the following substances:
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 on their own are generally not sufficient to remove such contaminants.
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.
In case of uncertainty about which contaminants are filtered 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/