George William Kajjumba, Ceonie M. M. Washington, Cagri Utku Erdem, Daekyun Kim, Tanju Karanfil, Zaid K. Chowdhury, Katherine Crank, Daniel Gerrity, Rebecca A. Trenholm, R. Scott Summers, Eric R. V. Dickenson
High Resolution Image Download MS PowerPoint Slide This study evaluated the effectiveness of parallel field-scale granular activated carbon (GAC) and biological activated carbon (BAC) filters for removing brominated and iodinated disinfection byproducts (Br-/I-DBPs) from a drinking water distribution system and associated changes in calculated additive toxicity (CAT). Over an 11 month period, 23 of 37 monitored DBP species were detected in the feedwater, with Br-/I-DBPs constituting 72% of trihalomethanes (THMs), 20% of haloaldehydes (HALs), 67% of haloacetonitriles (HANs), and 48% of haloacetic acids (HAAs). GAC effectively decreased all ambient HANs, HALs, and HAAs to below method reporting limits and completely removed THMs up to 3000 bed volumes, resulting in a 99% reduction in CAT. BAC removed all HANs, HALs, and HAAs but showed limited THM removal; however, CAT was reduced by 99%. Following GAC or BAC treatments, supplemental chlorination led to the formation of THMs, HALs, and HAAs─though no HANs─restoring 30–55% of the original CAT, primarily driven by brominated HALs. Microbial analysis revealed taxa, (e.g., Sphingomonas, Rhodospirillales, and Nitrosomonadales ) capable of DBP/precursor degradation, alongside taxa associated with opportunistic pathogens underscoring the need for post-treatment disinfection. Overall, GAC and BAC are effective strategies for mitigating Br-/I-DBPs in distribution systems, though rechlorination partially offset treatment benefits.