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. 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.
Understanding water contaminants can be difficult. Therefore it’s easier to focus on the specific contaminants in your tap water.
Potable (approved for drinking) 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.
Chlorine and by-products
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 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
- Most microbiological contaminants incl cysts, coliform and bacteria
- Inorganic contaminants such as lead, 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 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 TDSs and minerals in tap water.
More specifically activated carbon may not be sufficient in removing the following substances.
In areas and buildings with soft water and old pipes there can be a risk of lead in tap water. Normal activated carbon is not effective in removing this but there are special filters such as TAPP 2 that 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 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 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/