Adsorption / reduction of bromate from drinking water using GAC: effects on carbon characteristics and long-term pilot study

Abstract

This study investigated the feasibility of using granular activated carbon (GAC) to remove bromate (BrO₃^-) from drinking water through batch experiments, rapid small-scale column tests (RSSCT) and a pilot-scale study. The results indicated that the GAC capacity for BrO₃^- removal was dependent on the GAC surface characteristics and empty-bed contact time (EBCT). The GAC with a high number of basic groups and higher pHpzc values showed an increased BrO₃^- removal capacity. On the other hand, BrO₃^- removal was improved by increasing EBCT. In the GAC pilot plant, a GAC column (operating with 15 min EBCT) preload for 12 months achieved a BrO₃^- and assimilable organic carbon (AOC) removal rate ranging between 7 and 96 % and between 41 and 85 %, respectively. The amount of BrO₃^- removed was found to be proportional to the influent BrO₃^- concentration. Based on the results of our long-term experiment, the BrO₃^- and AOC removal rate during the transition from initial GAC to biological activated carbon (BAC) was calculated as 0.12 % w/w and 0.27 % w/w, respectively. However, the BrO₃^- removal rate apparently decreased with increasing operating time (after 3 months). This may be a result of the contribution of the bacterial biomass being adsorbed on the GAC surface which hindered BrO₃^- reduction by GAC, either by blocking the pores or adsorbing on the activated sites for BrO₃^- reduction.


WaterSA Vol.30 (3) 2004: 369-375