Effect of residual H₂O₂ on the removal of advanced oxidation byproducts by two types of granular activated carbon

Advanced oxidation processes (AOPs) such as UV/hydrogen peroxide (H₂O₂) systems are typically paired with a polishing granular activated carbon (GAC) filter to remove degradation byproducts from AOP effluent. In this study, the impact of residual H₂O₂ on the removal of five frequently detected AOP byproducts (formic acid: FA, acetic acid: AA, oxalic acid: OA, formaldehyde, and glyoxal) by two types of GACs (Filtrasorb-600/F-600 and Centaur) was investigated in batch experiments. The presence of byproducts significantly inhibited the decomposition of H₂O₂ on Centaur, but no inhibition was observed on F-600. In multi-component systems, byproduct removal kinetics and capacity of both GACs decreased due to competition. Centaur showed a sequential removal of byproducts following OA >FA/AA >aldehydes in mixtures. The presence of 10 mg/L H₂O₂ showed a temporary inhibition (0–72 h) on the removal efficiency of FA and AA by F-600, respectively. However, in multicomponent tests the presence of H₂O₂ had little impact on the removal efficiency of byproducts. Abiotic control experiments suggested the mechanism of byproduct removal by GACs was likely a combination of adsorption, biodegradation, and catalytical decomposition.