Prediction of Full-Scale GAC Adsorption of Organic Micropollutants

The principal goal of this research was to develop a new scale-up procedure with which the adsorption of organic micropollutants (MPs) by granular activated carbon (GAC) can be predicted from bench-scale tests. To develop scale-up approaches, the adsorption of 29 environmentally relevant MPs was studied in both pilot-scale GAC adsorbers and rapid small-scale column tests that were based on the proportional diffusivity design (PDRSSCT). Four surface waters with different dissolved organic carbon (DOC) concentrations were spiked with MPs at ng/L levels and tested in PD-RSSCTs simulating full-scale empty bed contact times of 7 and 15 min. Corresponding pilot-scale tests showed MP breakthrough occurred earlier than in PD-RSSCTs, and MP-specific differences between the PD-RSSCT and pilot column breakthrough curves were described by fouling parameters. On average, the PD-RSSCT overpredicted pilot-scale MP breakthrough by a factor of 3.0 +/- 1.2 (n = 101). Two approaches were developed for predicting bed volumes that can be treated to 10% MP breakthrough in full-scale adsorbers (BV10%,full-scale). In the first approach, a predictive relationship for the fouling parameter was developed and based on the MP to DOC concentration ratio in the adsorber influent, BVs to 10% MP breakthrough in the PD-RSSCT (BV10%,PD-RSSCT), and pH-dependent octanol-water partition coefficient (log D). In the second approach, BV10%,full-scale was directly predicted from BV10%,PD-RSSCT. These relationships were verified by adequately predicting full-scale GAC breakthrough curves for several MPs in a fifth water from a drinking water treatment plant on the Ohio River.