Carbon water filters use activated carbon to remove impurities from water through adsorption. They can be either granular activated carbon or carbon blocks and are effective against chlorine, VOCs, pesticides, herbicides, and mercury. Regular replacement of activated carbon is necessary for effectiveness.
A carbon water filter can be any type of water purification system that uses carbon to remove impurities. Common examples include large municipal granular activated carbon (GAC) systems, “charcoal” aquarium filters, and household or over-the-counter water filters, sometimes called household drinking water filters. Carbon water filters generally use either granular activated carbon or carbon blocks for purification, both of which remove impurities through a process called adsorption.
In a granular activated carbon (GAC) water filter, the water moves through small pieces of activated carbon. The texture of this carbon has been described as fine black sand or extremely fine coffee grounds, and has a large surface area for water to pass through. Impurities are trapped on the carbon through adsorption, resulting in cleaner water. GAC water filters can sometimes suffer from channeling, where water travels through a specific path that offers little resistance and results in little purification, if overused or improperly packaged.
In carbon block filtration, the carbon is pressed into a single block, usually cylindrical in shape. The water is then forced through the blockage, resulting in purification. While carbon block filters still use adsorption to clean water, dense carbon block filters can even physically block the passage of some microbiological agents, which less dense filters such as GACs generally cannot accomplish.
A carbon water filter removes many impurities from your water. Chlorine, volatile organic compounds (VOCs), pesticides, herbicides, and mercury are the factors these filters work best on. Some carbon block filters have also been designed to remove PCBs (polychlorinated biphenyls), lead and asbestos. Silver is sometimes added to granular activated carbon filters to provide antimicrobial properties. Carbon water filters are generally ineffective at removing other inorganic compounds, radionuclides, and many microbiological agents.
For a carbon water filter to be effective, the activated carbon needs to be changed regularly. While there are industrial ways to “recover” activated carbon, home users will need to replace the activated carbon during the recommended interval, usually after a specific number of gallons has been purified. Most retail carbon water filters use prepackaged cartridges to make it easier to replace the carbon, but you can still find some granular activated carbon filters that allow consumers to handle the carbon themselves.
As mentioned earlier, a carbon water filter uses a process called adsorption to purify water. In adsorption, small particles are removed from water or air and adhere to the surface of another substance. The porous nature of carbon has a large surface area which allows this process to work very well.
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