Granular activated carbon (GAC), which adsorbs harmful or odorous organic compounds from drinking water, can be reactivated and reused to reduce costs. In fact, the costs of reactivating and reusing GAC are about a third of the cost of replacement with virgin GAC. However, accumulated metals on GAC affect its thermal reactivation as well as the adsorption process. The metal calcium (Ca) is notorious for having the most deleterious effect on GAC during reactivation and reuse in that it can catalytically convert micropores to mesopores and even cause the water pH to increase when reactivated GAC is put back in service. The objective of this study was to determine whether Ca loading could be mininized by adjusting pH or coagulants without compromising other water treatment goals. The results indicate that lowering pH or adding iron coagulants could indeed reduce Ca loading onto GAC. The authors intended for their findings to provide a tool for utilities that may need to consider Ca buildup on GAC in addition to other requirements of finished water quality. They hope their article will help water suppliers who use GAC treatment better understand Ca's role in the adsorption process and maybe even correct any Ca loading problems they may have. Includes 39 references, table, figures.