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Why is granular activated carbon often used in water filtration?

Granular activated carbon (GAC) is commonly used for removing organic constituents and residual disinfectants in water supplies. This not only improves taste and minimizes health hazards; it protects other water treatment units such as reverse osmosis membranes and ion exchange resins from possible damage due to oxidation or organic fouling. Activated carbon is a favored water treatment technique because of its multifunctional nature and the fact that it adds nothing detrimental to the treated water. powdered activated carbon suppliers

Most activated carbons are made from raw materials such as nutshells, wood, coal and petroleum.

Typical surface area for activated carbon is approximately 1,000 square meters per gram (m2/gm). However, different raw materials produce different types of activated carbon varying in hardness, density, pore and particle sizes, surface areas, extractables, ash and pH. These differences in properties make certain carbons preferable over others in different applications.

The two principal mechanisms by which activated carbon removes contaminants from water are adsorption and catalytic reduction.Organics are removed by adsorption and residual disinfectants are removed by catalytic reduction.

Activated carbon beds are filters and need to be backwashed periodically. A freeboard of about 50 percent should be incorporated into the vessel design to allow backwash inplace. Otherwise, external backwash is required. The backwash step does not 'regenerate' the carbon or de-adsorb contaminants. The backwash step reclassifies the bed and removes any fines or suspended matter.

Carbon fines are generated during transport, handling and loading of activated carbon. These fines need to be backwashed out before service. Pre-wetted and backwashed carbons are available that minimize the fines and also eliminate the problems mused by carbon dust in a facility, Loading carbon tanks with dry carbon is a messy, hazardous job. Using pre-wetted carbon eliminates the airborne dust and makes for a clean plant environment.

Processed grades of activated carbon are available that include medical/pharmaceutical grades, electroplating grades, and powdered or pelletized carbons.

Activated carbon is a proven technology for the removal of naturally occurring organics and residual disinfectants. Designing an activated carbon filtration system needs to take into account the differences in the water to be treated, the type of activated carbon used, and the effluent quality and operating parameters.

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