The information below is provided by the Water Quality Association.

Activated Carbon (Granular and Solid Block)

Granular activated carbon is a well-established technology for the reduction of a wide range of aesthetic contaminants, and is quite effective in the reduction of some health contaminants such as volatile organic compounds (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. Granular activated carbon filters are typically inexpensive, and maintenance involves replacing six to twelve cartridges a year, depending on the quality of the raw water and the filter media.

Specially designed solid block and pre-coated activated carbon filters are also available, which are effective at reducing heavy metals such as lead and mercury. Solid block filters with a pore size smaller than 0.2 microns are often effective against biological contaminants as well.

Micro filtration

Micro filtration uses a filter media with a pore size smaller than 0.2 microns to physically prevent biological contamination from passing through. Ceramic and solid block carbon are commonly used to provide micro filtration. Ceramic filters have and advantage in that they can often be cleaned and reused a number of times before they lose effectiveness.

Carbon block media usually has to be disposed of after each use. This media, however, provides additional treatment for a variety of other health and aesthetic contaminants (see activated carbon section). Micro filtration is effective for treating the full range of biological contaminants, including hard-shelled cysts like Cryptosporidium.