Removal of bromate and assimilable organic carbon from drinking water using granular activated carbon

This study investigated the feasibility of using granular activated carbon (GAC) to remove bromate ion (BrO₃^-) and assimilable organic carbon (AOC) from drinking water through a rapid small-scale column test (RSSCT) method and a pilot-scale study. Results from RSSCT indicated that the GAC capacity for BrO₃^- removal was dependent on the GAC type, empty bed contact time (EBCT), and source water quality. The GAC with a high number of basic groups and higher pHpzc values showed an increased BrO₃^- removal capacity. BrO₃^- removal was improved by increasing EBCT. The high EBCT provides a greater opportunity for BrO₃^- to be adsorbed and reduced to Br^- on the GAC surface. On the other hand, the presence of dissolved organic carbon (DOC) and anions, such as chloride, bromide, and sulfate, resulted in poor BrO₃^- reduction. In the GAC pilot plant, a GAC column preloaded for 12 months achieved a BrO₃^- and AOC removal range from 79-96% and 41-75%, respectively. The BrO₃^- amount removed was found to be proportional to the influent BrO₃^- concentration. However, the BrO₃^- removal rate apparently decreased with increasing operation time. In contrast, the AOC apparently increased during the long-term operation period. This may be a result of the contribution due to new GAC being gradually transformed into biological activated carbon (BAC), and the bacterial biomass adsorbed on GAC surface hindering BrO₃^- reduction by GAC either by blocking pores or adsorbing at the activated sites for BrO₃^- reduction.