A new approach to controlling halogenated DBPs by GAC adsorption of aromatic intermediates from chlorine disinfection: Effects of bromide and contact time

Abstract

Abstract Granular activated carbon (GAC) adsorption has been traditionally used to remove natural organic matter (NOM), the major precursor of halogenated disinfection byproducts (DBPs), in drinking water treatment plants. Recently, a new approach has been developed to effectively control the formation of trihalomethanes, haloacetic acids, and total organic halogen (TOX) in chlorinated drinking water by targeting intermediate aromatic halogenated DBPs instead of NOM using GAC adsorption. However, the applicability of this new approach to different source water matrices and disinfection conditions remained unclear. In this study, the effects of bromide and contact time on the performance of the new approach for DBP control were investigated. Same source waters were also treated with the traditional approach (i.e., using GAC to remove NOM prior to chlorination) and with chlorination only for comparison. With increasing the initial bromide level from 0 to 2 mg/L, the TOX removal with the new approach increased from 52% to 74%, while the removal with the traditional approach increased from 18% to 37%. Besides, as the chlorine contact time increased from 0.5 to 3.0 h, the TOX removal with the new approach increased from 61% to 75%, while the removal with the traditional approach increased from 21% to 36%. Increasing the bromide level and chlorine contact time enhanced the halogenated DBP removal with both new and traditional approaches, but the removal with the new approach was always two times higher or more than that with the traditional approach, which justified the superiority of the new approach. Moreover, various intermediate aromatic halogenated DBPs were detected in the chlorinated water samples and their levels were significantly decreased after the GAC adsorption, which further corroborated the effectiveness of the new approach for DBP control.