The regeneration process involves heating the carbon to very high temperatures to volatilise the adsorbed compounds.

Replacing the GAC on a regular basis results in high on-going treatment costs. The disadvantage is that it has a limited lifetime, and must be replaced or regenerated when its performance is no longer sufficient to provide high quality drinking water. The advantages of GAC are that it provides a constant barrier against unexpected episodes of contamination of water sources, and the large mass of carbon provides a very large surface area. Granular activated carbon is generally used as a final polishing step, after conventional treatment and before disinfection. The particle size is larger than that of PAC, usually between 0.4 and 2.5 mm. It is also becoming more widely used in Australia, particularly for taste and odour removal and insurance against the possibility of a toxic algae bloom in the water source. Granular activated carbon (GAC) is used extensively in Europe and the United States for the removal of micropollutants such as pesticides, industrial chemicals and tastes and odours. Newcombe, in Interface Science and Technology, 2006 2.4.2.

Activated carbon