Abstract
Water treatment facilities report that when reactivated granular activated carbon (GAC) is returned to service, pH excursions may occur, resulting in high pH of the treated water (e.g., pH > 9) as a result of a calcium chemistry mechanism. While air treatments and carbon dioxide (CO2) treatments following reactivation and prior to return to service create pH stable carbons (pH < 8.5), there has been no study on the impact of these treatments on the subsequent performance of the GAC. In a comparison of adsorption performance for 2-methylisoborneol (MIB), a common taste- and odor-causing compound, untreated reactivated GAC removed more MIB than the air-treated reactivated GAC in organic free water, while this trend was reversed when natural organic matter was present. In both waters, the CO2-treated reactivated GAC removed the greatest quantity of MIB. CO2 was proven effective since it deterred water adsorption, which is deleterious to MIB adsorption.
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