Chlorine dioxide has been used as a water disinfectant in water reclamation plants prior to the emergence of RO membrane process. However, the effects of chlorine dioxide on the integrity of RO membranes have yet to be fully understood. In this study, the influence of chlorine dioxide on RO membranes was investigated by observing chlorine dioxide reactions in the presence of iodide and bromide, structural changes of the RO membrane active layer polyamide and evolution in RO membrane assesses a solute passage (Rhodamine WT) and water flux. Batch experiments were performed to assess the reaction of chlorine dioxide, bromide and iodide in a potassium phosphate (10mM) buffered solution (pH=7.5). Iodide was found to react with chlorine dioxide over time while bromide did not under condition relevant to water treatment. On the other hand, chlorine dioxide oxidized bromide when the bromide concentration exceeded that of chlorine dioxide. Investigation of the influence of these compounds on the RO membrane polyamide using Rutherford back-scattering spectrometry (RBS) revealed that polyamide was underwent bromination but was more resistant to chlorination and iodination. These results suggest that chlorine dioxide oxidizes bromide although the reaction is slow, and it leads to polyamide bromination. Furthermore, RO membranes exposed to chlorine dioxide and bromide had significantly decreased the solutes rejection and water flux, while exposure to chlorine dioxide alone had no measureable influence. Therefore, we found that chlorine dioxide oxidation of bromide specifically leads to polyamide bromination and RO membrane deterioration
