Granular activated carbon filter applications

Granular activated carbon is also sometimes used as replacement for sand in conventional treatment filters as this is a low-cost alternative to retrofitting GAC filters in an existing plant, where space constraints may not allow additional filters to be built. The effectiveness of this method of application is determined by the flow of the water and depth of the filters, and sometimes the contact time with the activated carbon is too low to allow prolonged adsorption of problem compounds. 

Granular Activated Carbon, or GAC has a mean particle size between 1-5 mm. It is usually used in fixed bed adsorbers in continuous processes and with low pressure drops, in both liquid and gas phase applications. Most of the gas phase applications (gas purification, solvent recovery, air filtering and gas masks, gas separation by PSA, catalysis, etc.) use GAC. In addition, GAC is displacing PAC in many liquid phase applications such as gold extraction and drinking water treatment GAC has the advantage, compared to PAC, of offering a lower... 

Besides composite applications of electrospun carbon nanofibers, these materials can be used as filter media also and be applied to remove disinfection b5rproducts from water [168], for gas separation, solvent recovery and catalyst support [169]. These activated carbon nanofibers have low pressure drop compared to granular activated carbon. 

These properties of activated carbons caused their great application to water treatment. In Poland adsorption is also more and more frequently used. Activated carbons may be used to water treatment in static and dynamic conditions. The use of powdered carbon is often cotmected with coagulation, and granular carbon may be a bed of various kinds of filters such as open and close, parallel and operating in series with stationary and mobile bed, adsorptive and mechanical - adsorptive filters [15-17]. 

Activated carbon, in powdered (PAC) or granular (GAC) form, has many applications in drinking water treatment. It can be used for removing taste and odor (T O) compoimds, synthetic organic chemicals (SOCs), and dissolved natural ot] nic matter (DOM) from water. PAC typically has a diameter less than 0.15 mm, and can be applied at various locations in a treatment system (Fig. 1). GAC, with diameters ranging from 0.5 to 2.5 mm, is employed in fixed-bed adsorbers such as granular media filters or post filters. Despite difference in particle size, the adsorption properties of PAC and GAC are fundamentally the same because the characteristics of activated carbon (pore size distribution, internal surface area and smface chemistry) controlling the equilibrium aspects of adsorption are independent of particle size. However, particle size impacts adsorption kinetics. 

The gas-adsorptive properties of wood charcoal were recognized as early as 1773 by Scheele (Deitz, 1944) however, it was not until the middle of the nineteenth century that the property was utilized commercially. This application consisted of the use of charcoal air-filters in the ventilation and disinfection of sewers (Stenhousc, 1961). The next major step in the development of active carbon for gas ad.sorption occurred during World War I, when the use of poison gas by the Germans made it necessary to develop a hard, granular carbon for gas-mask use. 

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