Granular activated carbon (GAC) has a strong attraction for organic compounds and other non-polar contaminants in water and adsorbs them onto the carbon surface.

Typical uses:

Dechlorination: GAC has the ability to reduce chlorine from an oxidizer (NaOCl) to a salt (NaCl) by taking away the reactive oxygen.

Removal of taste, odour, colour, organics etc: GAC (granular activated carbon) is widely used to reduce undesirable taste, odour and colour and to improve the safety of drinking water by also effectively removing common disinfection byproducts (THMs), organic contaminants like chlorinated solvents and other industrial pollutants, pesticides

Removal of selected heavy metals:  such as lead and mercury.

Radon removal: GAC has been shown to achieve greater than 90% reduction of radon from treated drinking water.  It is recommended though that media be replaced at least once a year.