Novel insights into the control of N-nitrosodimethylamine (NDMA) and bromate formation during heterogeneous catalytic ozonation.

[Display omitted] • NDMA formation can be effectively controlled during the O 3 /Al 2 O 3 process. • NDMA formations are relatively high for O 3 /MnOx/Al 2 O 3 and O 3 /β-FeOOH/Al 2 O 3. • NDMA can be removed by MnOx/Al 2 O 3 and β-FeOOH/Al 2 O 3 catalysts via adsorption. • Bromate control: O 3 /β-FeOOH/Al 2 O 3 > O 3 /MnOx/Al 2 O 3 > O 3 /Al 2 O 3 > ozonation alone. N-nitrosodimethylamine (NDMA) and bromate (BrO 3 -) have been found to be disinfection by-products during ozonation, which need to be solved urgently. In this study, O 3 /Al 2 O 3 , O 3 /MnOx/Al 2 O 3 and O 3 /β-FeOOH/Al 2 O 3 were used to investigate the control of NDMA and BrO 3 - formation during the ozonation of daminozide (DMZ) and Br-. During ozonation alone, NDMA formation decreased from 0.66 to 0.37 μM with increasing ozone dosages (20–100 μM) without tert -butanol (TBA). Greater control efficiency for NDMA formation was observed during the O 3 /Al 2 O 3 process (0.55–0.21 μM), which was attributed to the high hydroxyl radical (•OH) yield, and NDMA formation during the O 3 /MnOx/Al 2 O 3 and O 3 /β-FeOOH/Al 2 O 3 processes changed negligibly (∼0.63 and ∼ 0.65 μM, respectively). The formation of NDMA was affected by different concentrations of Br - , HCO 3 – , tannic acid, and humic acid, which was attributed to the competition for ozone or •OH. During ozonation process, the addition of catalysts could effectively control BrO 3 - formation due to the decomposition of HOBr and the adsorption or reduction of BrO 3 - by catalysts. The control efficiencies of BrO 3 - formation were in the order of O 3 /β-FeOOH/Al 2 O 3 > O 3 /MnOx/Al 2 O 3 > O 3 /Al 2 O 3 > ozonation alone. In a real water sample without Br - , significant control of NDMA was observed in the presence of the catalysts. In a real water sample containing Br-, NDMA formation decreased in the presence and absence of catalysts, and a great control capacity for BrO 3 - formation was exhibited during the O 3 /Al 2 O 3 , O 3 /MnOx/Al 2 O 3 and O 3 /β-FeOOH/Al 2 O 3 processes. Therefore, the addition of catalysts can be utilized to control disinfection by-products during ozonation. [ABSTRACT FROM AUTHOR]