Activated Carbon (Granular and Solid Block)

Granular activated carbon is a well established and proven technology for the reduction of a wide range of aesthetic contaminants (see chapter on Aesthetic Water Quality Problems), and is quite effective in the reduction of some health contaminants such as volatile organic compounds like benzene, trichloroethylene, and other “petroleum” based contaminants.

Because of its molecular makeup, activated carbon can adsorb well, meaning that it can take in or collect many organic molecules on its surface. Carbon filter’s effectiveness depends on the amount of carbon in the unit and how long the water stays in the unit. The longer the water is in contact with the carbon medium, the more of the impurities are removed. Granular activated carbon filters are relatively inexpensive, and maintenance involves replacing the cartridge every two months or so depending on the quality of raw water and the pre-carbon filter media (first stage filter cartridge). Activated carbon granular filters do not provide physical microfiltration.

Specially designed solid block and coated fibre activated carbon filters are also available. These filters are more expensive but are effective at reducing heavy metals such as lead and mercury. Solid block carbon filters with a pore size smaller than 0.2 microns are often effective against biological contaminants by filtering them out physically.

Carbon filter cartridges must be replaced when taste or odour problems reappear.