Factors controlling the adsorption of natural organic matter onto virgin and thermally reactivated granular activated carbons during full-scale water treatment

This thesis compares the performance and characteristics of reactivated GACs with their virgin counterparts during full-scale water treatment at the Richard Miller Water Treatment Plant in Cincinnati, Ohio. It was shown that with each passing cycle of thermal reactivation, the GACs pore structure was further widened. Despite the dissimilarities in pore structure, reactivated GACs generally performed the same as their virgin counterpart. For the virgin GAC, adsorption occurred most extensively in the micropores and also in the small mesopores. With each passing cycle of water treatment and reactivation, the zone of pore volume loss had shifted into larger pore sizes.;During the first few months of water treatment, there was no apparent correlation between pore structure (for virgin versus reactivated GACs) and the removal of various NOM molecular weight fractions. After 3--4 months of service, a subtle correlation existed between molecular weight of NOM being removed and the pore structure of each GAC. During the first 2--6 weeks of service, adsorption was significantly governed by pore structure since the adsorption pores (e.g. those <40A) were very similar in size to the TOC being adsorbed (mostly <20A). Subsequent uptake of NOM continued to result in a decline in the volume of pores <40A for the virgin GAC. In contrast, subsequent uptake by the reactivated GACs resulted in a substantial decline in the volume of pores larger than <40A. Trends provide strong evidence that a portion of the NOM that adsorbed onto pores larger than 20A thereafter migrated into the micropores.;The reactivated GACs possessed a greater amount of net positive charge than did the virgin. Yet, results indicate that (adsorption enhancing) electrostatic interactions between the negative NOM and positive GAC surface sites occurred more extensively for the virgin than for the reactivated GACs during the first 15 days of service.