When to replace granular activated carbon filter

Granular activated carbon, also known as GAC, has a larger particle size than PAC with an associated greater surface area.  Like PAC, GAC can remove trihalomethane precursors as well as taste and odor compounds.


GAC is used as a filter medium, either as a layer in a rapid-sand filter or in a separate filter known as a contactor.  When contactors are used, the contactor is placed downstream of the filter so that turbidity won’t clog the contactor.


During operation of a GAC filter or contactor, a variety of factors must be monitored.  If the GAC is part of a filter designed to remove particulate matter as well as to adsorb tastes and odors, then the effluent turbidity should be monitored.  Similarly, the taste and odor contaminants in the effluent should be monitored to determine whether the GAC is operating properly.  activated carbon pellets The operator should make regular checks for bacteria since microorganisms often grow on GAC filters and result in clogging problems.  Finally, head loss must be monitored as it would be for any other filter to determine when the unit needs to be backwashed.  Washing a GAC filter involves backwashing with a 50% bed expansion and surface washing.


Although GAC filters can be operated like a rapid sand filter in most ways, 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, just as a softener’s resin will become covered with magnesium and calcium ions.  A GAC filter can typically operate for months or years before reaching this state, depending on the contaminant levels in the influent water.  www.granular-activated-carbon.com 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.

Ambassador Asked on November 6, 2020 in Chemistry.
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