Formation control of bromate and trihalomethanes during ozonation of bromide-containing water with chemical addition: Hydrogen peroxide or ammonia?

To ensure the safety of drinking water, ozone (O) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM). However, the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br). Considering the risk of bromate (BrO) formation in ozonation of the sand-filtered water, the inhibitory efficiencies of hydrogen peroxide (HO) and ammonia (NH) on BrO formation during ozonation process were compared. The addition of HO effectively inhibited BrO formation at an initial Br concentration amended to 350 µg/L. The inhibition efficiencies reached 59.6 and 100% when the mass ratio of HO/O was 0.25 and > 0.5, respectively. The UV and total organic carbon (TOC) also decreased after adding HO, while the formation potential of trihalomethanes (THMsFP) increased especially in subsequent chlorination process at a low dose of HO. To control the formation of both BrO and THMs, a relatively large dose of O and a high ratio of HO/Owere generally needed. NH addition inhibited BrO formation when the background ammonia nitrogen (NHN) concentration was low. There was no significant correlation between BrO inhibition efficiency and NH dose, and a small amount of NHN (0.2 mg/L) could obviously inhibit BrO formation. The oxidation of NOM seemed unaffected by NH addition, and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH. Considering the formation of BrO and THMs, the optimal dose of NH was suggested to be 0.5 mg/L.