Activated carbon is one of the most widely used filtration materials in water treatment. It is particularly effective at reducing chlorine, unpleasant tastes and odours, and many dissolved organic contaminants.
However, not all activated carbon is the same. Different raw materials, manufacturing processes and surface properties affect what each carbon can remove and how efficiently it performs.
Understanding these differences is important when selecting filtration media for domestic, commercial and industrial applications.
What Is Activated Carbon?
Activated carbon is produced from carbon-rich materials such as coconut shells, coal and wood.
During manufacturing, the material undergoes an activation process that creates an extensive network of microscopic pores.
These pores provide a very large internal surface area, allowing contaminants to be retained through a process known as adsorption.
Unlike absorption, where a substance is taken into the body of a material, adsorption involves molecules adhering to its surfaces.
Activated carbon is particularly useful for removing certain dissolved organic compounds that conventional sediment filtration cannot effectively capture.
What Does Activated Carbon Remove from Water?
Depending on the carbon type and operating conditions, activated carbon can be effective at reducing:
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Free chlorine: Commonly used for dechlorination and improving taste and odour.
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Organic contaminants: Including many volatile organic compounds (VOCs), pesticides and other organic chemicals.
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Taste and odour compounds: Responsible for unpleasant smells or flavours.
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Some disinfection by-products: Including certain trihalomethanes (THMs).
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Natural organic matter: Certain compounds responsible for colour, taste or odour.
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Chloramines: Particularly when using appropriately selected catalytic activated carbon.
The removal efficiency varies considerably between contaminants.
Carbon type, bed depth, contact time, water temperature, pH and competing contaminants all influence performance.
What Does Activated Carbon Not Remove?
Activated carbon is not a universal water purification medium.
Standard activated carbon should not normally be relied upon to remove:
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Dissolved calcium and magnesium hardness
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Nitrates
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Dissolved salts
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Most dissolved iron and manganese
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Fluoride
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Arsenic
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Bacteria and viruses
Specialist modified carbons may have additional capabilities, but these must be supported by the manufacturer's specifications and appropriate water testing.
Activated carbon is not a disinfectant. Where microbiological contamination is present, suitable additional treatment is required.
The Different Types of Activated Carbon
1. Coconut Shell Activated Carbon
Coconut-based activated carbon is manufactured from coconut shells and is particularly valued for its hardness and highly developed microporous structure.
It is widely used for:
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Free chlorine reduction
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Taste and odour improvement
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Adsorption of selected organic contaminants
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Pretreatment for reverse osmosis systems
Its physical durability makes it suitable for many cartridge and granular filtration applications.
Examples available from GAPS Water Treatment:
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Chemviron Aquacarb 207C Coconut Granular Activated Carbon
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Chemviron 607C Acid Washed Coconut Activated Carbon
Acid-washed carbon is processed to reduce certain mineral impurities, making it useful where low extractables and consistent water quality are important.
2. Coal-Based Activated Carbon
Coal-based activated carbon is typically manufactured from bituminous coal.
It generally provides a broader distribution of pore sizes than many coconut-based carbons, which can be advantageous when treating water containing a mixture of organic compounds.
Common applications include:
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Organic contaminant reduction
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Taste and odour control
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Reduction of certain disinfection by-products
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Municipal and industrial water treatment
Example available from GAPS Water Treatment:
Jacobi AquaSorb 1200 Bituminous Coal Activated Carbon.
The choice between coal and coconut carbon should depend on the contaminants being treated rather than assuming one material is always more effective.
3. Wood-Based Activated Carbon
Wood-based carbon is often selected for applications involving larger organic molecules.
Depending on its manufacture and pore structure, it can be particularly useful for:
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Colour reduction
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Selected natural organic compounds
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Industrial process water
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Certain wastewater treatment applications
Wood-based carbon is available in different grades, including granular and powdered forms.
4. Catalytic Activated Carbon
Catalytic activated carbon has enhanced surface properties that promote specific chemical reactions in addition to conventional adsorption.
It is particularly useful in applications involving:
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Chloramine reduction
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Hydrogen sulphide treatment under suitable operating conditions
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Certain oxidation and reduction processes
Chloramine is generally more difficult to remove than free chlorine, so adequate contact time is especially important.
Catalytic carbon should be selected according to the manufacturer's stated application and operating requirements.
Example available from GAPS Water Treatment:
CTX-L1000 Catalytic Activated Carbon.
The effectiveness of catalytic carbon for hydrogen sulphide or iron treatment depends on factors such as dissolved oxygen, pH, contaminant concentration and system design.
What About Bone Charcoal?
Bone charcoal, also called bone char, is sometimes grouped with activated carbon products, but it is a different type of filtration material.
It is manufactured by heating animal bones under controlled conditions.
Unlike conventional activated carbon, bone char contains a substantial proportion of calcium phosphate minerals, particularly hydroxyapatite, alongside its carbon content.
These minerals give bone char different adsorption characteristics.
It has traditionally been used for specialist applications, particularly fluoride reduction, and may also be suitable for reducing certain metals under appropriate conditions.
However, performance depends on water chemistry, contact time and the particular contaminant.
Bone char should therefore be considered a specialist treatment medium rather than a direct substitute for ordinary activated carbon.
GAPS Water Treatment also supplies bone activated charcoal for suitable specialist applications.
Granular Activated Carbon vs Carbon Block Filters
Activated carbon is available in several physical forms.
Granular Activated Carbon (GAC)
Granular carbon consists of loose particles through which water flows.
It is commonly used in:
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Automatic backwashing pressure vessels
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Commercial filtration systems
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Whole-house filtration
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Industrial process water treatment
Larger granular systems can provide substantial media volumes and extended contact times.
Carbon Block Filters
Carbon block cartridges are manufactured by compressing or bonding fine carbon particles into a solid structure.
Depending on their construction, carbon blocks can provide both adsorption and particulate filtration.
They are commonly used in:
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Under-sink drinking water systems
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Domestic reverse osmosis pretreatment
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Point-of-use filtration
Carbon blocks may provide improved particulate retention compared with loose granular carbon, although they can introduce greater pressure loss.
The manufacturer's flow and contaminant-reduction ratings should always be checked.
Why Contact Time Matters
One of the most important considerations when designing an activated carbon system is contact time.
Water must remain in contact with the carbon for long enough to achieve the intended treatment.
A filter that successfully removes free chlorine
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