Powdered Activated Carbons are used by water treatment plants for taste and odour control and to ensure the removal of organic chemicals. Powdered Activated Carbons are added early in the treatment process to enable a period of sole contact time before other treatment chemicals are added to the water stream.
They should not be coated with any other water treatment chemicals before they have been allowed sufficient contact time with the water stream (typically Powdered Activated Carbons will require at least 15 minutes sole contact time with the water stream). Most importantly, Powdered Activated Carbons should never be added concurrently with chlorine or potassium permanganate as such water treatment chemicals will simply be adsorbed by the activated carbon powder.
Typical required dosages can range anywhere between 1 to 100 mg/L depending on the type and level of contaminant, but dosages of 1 to 20 mg/L are most typical where treating water streams for the purpose of taste and odour control. Higher dosages will be required where PACs are added later in the treatment process, to allow for any adsorption of other treatment chemicals added earlier in the process. Powdered Activated Carbons are later removed from water streams through a process of sedimentation or by filter beds.