A two-year study at the City of Scottsdale and the City of Phoenix resulted in important findings for surface water utilities that use granular activated carbon (GAC) for disinfection byproduct (DBP) precursor removal. The research team investigated the effects of pre‐oxidants on total organic carbon (TOC) in terms of DBP formation potential and adsorption onto GAC. They also looked at the potential for chlorine to react with organics adsorbed on GAC to form DBPs if water with chlorine residual enters the GAC adsorber. The team also sought to understand the impact of pre‐oxidation on GAC reactivation frequency and the overall economics of including pre‐oxidation with GAC. The team found that pre-oxidation with chlorine can a viable strategy for some utilities. Pre-chlorination forms regulated total trihalomethanes and haloacetic acids, which can then be removed by GAC, resulting in a lower DBP formation potential. The project is also summarized in a brief video.