Activated Carbon Filters

• Adsorption — organic substances, taste and odour compounds attach to the very large inner surface of the carbon grains, 800–1,200 m² per gram.
• Dechlorination — free chlorine reacts at the carbon surface within seconds. Chloramines react much more slowly and need catalytic carbon and a longer contact time.
• Operation — the water flows downwards through the bed. A periodic backwash loosens the bed and removes trapped particles; it does not restore the adsorption capacity.
• Exhaustion — when the capacity is used up, the substances break through. The carbon is then replaced, or thermally reactivated in the case of large quantities.

• Empty bed contact time (EBCT) — the bed volume divided by the flow. Dechlorination needs 2–5 minutes, chloramine removal about 10 minutes with catalytic carbon, organics and taste and odour 10–20 minutes.
• Example — 10 m³/h with a contact time of 10 minutes needs a bed of about 1.7 m³.
• Filtration velocity — typically 10–20 m/h; the bed depth is usually 1.0–1.5 m.
• Carbon type — coconut-shell carbon with many fine pores for chlorine and small molecules, coal-based carbon for larger organic molecules, catalytic carbon for chloramines.
• Hygiene — carbon beds remove the disinfectant and can grow bacteria. Regular backwashing, hot water or steam sanitisation, or a UV unit downstream keep the water quality stable.

Ahead of reverse osmosis the carbon filter is followed by a cartridge filter that catches carbon fines. Vessels are FRP pressure tanks or coated steel.

• Bed volume — contact time multiplied by flow; it sets the vessel size and the first carbon fill.
• Carbon grade — catalytic and acid-washed grades cost more than standard grades.
• Vessel and valves — FRP with a multiport valve for small flows, steel with a valve nest for large flows or steam sanitisation.
• Operating cost — carbon replacement. The interval ranges from months to several years, depending on the load of organics and chlorine.

What does an activated carbon filter remove?

Granular activated carbon removes chlorine, chloramines, trihalomethanes (THMs), total organic carbon (TOC), taste and odour from drinking water and process water. Chlorine is reduced by more than 99% to below 0.05 mg/L, and TOC reduction of up to 80% is possible depending on the contact time.

Which type of activated carbon is right for my application?

Coal-based GAC is a versatile standard media, while coconut-shell GAC offers the highest surface area (1,000 m²/g and above) for maximum adsorption capacity. Catalytic carbon is the right choice where chloramine has to be removed, which is critical for protecting RO membranes.

How is an activated carbon filter sized and how often must the media be replaced?

The vessel is sized for a minimum empty bed contact time (EBCT) of typically 5–15 minutes, depending on the application, at flows from 0.2 to 200 m³/h per vessel. Regular backwashing keeps the bed porous and prevents compaction, and the media normally lasts 2–5 years before replacement, depending on the contaminant load.

What information do you need for a quotation?

Please tell us the flow rate, the contaminants to be removed and their concentrations (for example chlorine, chloramine or TOC), the application (drinking water, RO pre-treatment or process water), the operating pressure and temperature, your preferred vessel material and whether manual or automatic backwash control is required. Send us your requirements and we will prepare a proposal within 48 hours.