Changes in GAC pore structure during full-scale water treatment at Cincinnati: A comparison between virgin and thermally reactivated GAC

During full-scale water treatment operation at the Richard Miller water treatment plant (Cincinnati, Ohio) we frequently evaluated the changes in pore volume distributions of a reactivated (F-400) granular activated carbon (GAC), as compared with that of its virgin counterpart. The reactivated GAC had experienced six cycles of water treatment and thermal reactivation. The reactivated GAC was slightly more effective at removing TOC (total organic carbon) than was the virgin GAC during the first half-year of service. Yet, the pore size distributions of the two GACs were very different. The virgin GAC was mostly microporous, with less mesopores. Conversely, the reactivated GAC was mostly mesoporous, with less micropores. For the virgin GAC, adsorption changed the volume of pores below 50 Å in width most significantly, and there was minor change in pores larger than 50 Å. In contrast, the reactivated GAC showed the greatest volumetric change in pores that were 100 to 500 Å in width.