Reduction of chlorinous odor by the combination of oxidation and ion-exchange treatments

To better control chlorinous odor in tap water, we assessed the performance of the combination of oxidation (ozonation or advanced oxidation processes, AOP) and ion-exchange treatment. In this process, the hydrophilic neutral fraction (a major dissolved organic matter (DOM) fraction) is converted to ionic species, and these ions and ammonium ion are effectively removed during ion-exchange processes. We found that each treatment process (e.g., oxidation alone or ion exchange alone) was effective for the reduction of chlorinous odor to some extent, but the chlorinous odor formation potential was lower when the oxidation process and ion exchange were applied in series. The combination of AOP (ozone/vacuum ultraviolet treatment) at a high ozone dose and ion exchange (both cation and anion) was most effective, and the chlorinous odor formation potential was reduced to approximately 30 TON (threshold odor number) from more than 100 TON. Also, dissolved organic carbon and ammonium ion were effectively removed with this process. Compared with ozonation, AOP was more effective at a higher ozone dose. The effectiveness of this process was also confirmed in continuous mode by pilot-scale experiment.