Granular Activated Carbon Filter

In water treatment, a granular activated carbon filter (short: GAC filter) serves for removal of certain dissolved or suspended molecular substances, or of certain emulsified liquids, primarily by means of adsorption. The adsorbent (or "filter" material) is a packed bed of granular activated carbon, with equipment and filter vessel design (but not process design) being basically identical to actual bed filters, e.g. →sand filters. Typical applications are removal of organic compounds (e.g. measured by TOC = total organic carbon), removal of oil and grease, or removal of chlorine. With increasing service life, the granular activated carbon adsorbent will eventually become depleted, and need to be replaced. This is due to the useable active surface of the adsorbent being reduced by adsoprtion of the adsorbate, but for certain applications also biological fouling, or – in case of chlorine removal – consumption of the adsorbent due to chemical reactions.