Treating water containing elevated bromide and iodide levels with granular activated carbon and free chlorine: impacts on disinfection byproduct formation and calculated toxicity

We evaluated the efficacy of granular activated carbon (GAC) adsorption for mitigating formation of chlorine disinfection byproducts (DBPs) in water with a wide range of bromide (20–1000 μg L−1) and iodide ( 30 000 bed volumes). In the GAC influent, total organic bromine increased from 10 to 84% of TOX as bromide levels increased from 20 to 1000 μg L−1. Dissolved organic carbon (DOC) removal by GAC increased the bromide-to-DOC (Br/DOC) concentration ratio in GAC effluent relative to influent. As a result, bromine incorporation into DBPs increased after GAC treatment, especially at early GAC service times and low bromide levels. Total organic iodine was 50%) in all samples despite the quantification of 70 DBPs targeted in this study, highlighting the need to assess toxicity associated with unknown DBPs.