Disinfection byproduct (DBP) formation depends on the presence and reactivity of oxidants and precursors, including natural organic matter (NOM), bromide ions, and/or iodide ions and is influenced by water quality and treatment conditions. Controlling DBP formation has historically focused on removing NOM through various treatment processes, altering disinfectant types or sequences, or changing treatment conditions. Bromide and iodide ions react with oxidants and NOM to form intermediates and produce regulated and non-regulated organic or inorganic DBPs. Brominated and iodinated organic DBPs pose greater human health risks than chlorinated analogs. This project will investigate the source factors influencing the temporal and spatial occurrence of bromide ions, and total organic bromine or chlorine in drinking waters and identify potential treatment strategies to control bromide and iodide within water treatment plants.