Matter and energy

Types of Activated Carbon


Powdered activated carbon (PAC) and granular activated carbon (GAC) are the two types of activated carbon. Don’t get confused. This article will guide you through the background and the strength of each activated carbon.

Powdered activated carbon is a form of activated carbon with a very small particle size. The feed location of PAC can be at any point prior to filtration.  The most common locations are in the flash mixer or flocculator since these pieces of equipment will mix the PAC into the water very well.

Regardless of the feed location, PAC can be added to water. The effectiveness of PAC in adsorbing tastes and odours depends on adequate mixing, contact time, dosage, the cause and concentration of the taste/odour problem.
Granular activated carbon has a larger particle size than PAC with the greater surface area.  Like PAC, GAC can remove taste and odour compounds.

GAC is used as a filter medium and GAC filters can be operated like a rapid sand filter in most ways. However, backwashing and surface washing are not the only cleaning required for the units.  The entire surface of the GAC will eventually become covered with contaminants.  A GAC filter can typically operate for months or years before reaching this state, depending on the contaminant levels in the influent water.  Once the GAC has reached its adsorption capacity, it must be regenerated using the same heating process used to activate the carbon.  In many plants, GAC is simply replaced rather than investing in the equipment required for regeneration.
How to choose the type of activated carbon?

GAC and PAC each have advantages and disadvantages.  In general, GAC is used for applications such as water and air industries. PAC is usually used for filtering gas in factories. Also, PAC is used more often due to the low initial cost and to the flexibility of dosage. However, PAC has a high operating cost if used continuously and cannot be regenerated. Thus, GAC becomes a more economical choice in larger systems or where taste and odour must be controlled continuously.

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