Carbon water filters are generally made from either charcoal or coconut carbon. While coconut carbon is considered the best or healthiest for drinking water treatment, charcoal is still used by some manufacturers as a more economic alternative.
The carbon is either broken up and graded into a granular form or ground into a powder and processed into a carbon block filter. Hollow carbon technology is now the latest advancement in carbon filtration providing 10 times the surface area of standard granular carbon with considerably higher flow rates and substantially higher filter capacity. Hollow carbon is derived from granular form.
The general term all of these types of carbon is activated carbon.
How Does Carbon Work
Carbon filters remove or reduce water contaminants by physically trapping them or by absorption. Each piece of carbon is generally activated with a positive charge and is designed to attract negatively charged water contaminants absorbing them as they pass over the carbon surface area. The larger the surface area of the carbon and the slower the water moves past the carbon or through the filter, the higher the contaminant removal.
Carbon coated filters have very low absorption. Higher absorption rates are achieved by carbon block filters followed by granular filters and hollow carbon.
Carbon filters are very effective at removing chlorine, herbicides, pesticides and other volatile organic compounds (VOC’s) from water but are not very effective at removing minerals, salts and dissolved inorganic compounds such as aluminum, copper, fluoride, iron, lead, silver, etc.
While carbon filters remove contaminants they also remove chlorine and other sanitisers that kill and prevent bacteria growth within the cartridge. Therefore after a period of time bacteria will start to grow with carbon cartridges. For this reason manufacturers put a usable lifespan on their cartridges much the same as a use by date on food. This is usually 6 or 12 months; after this time the cartridge should be removed from the system and disposed of even if the system has only been used for a few days during the year.
Some cartridge filters do however use secondary media such as silver or KDF-55 to prevent bacteria growth within the filter. This media cannot really be said to kill bacteria but more inhibit its growth, providing an unpleasant environment for it to grow.