Bromate Formation in the Raw Water of the Huangpu River and the Yangtze River during Ozonation Process

A series of bench-scale experiments was conducted in order to study the bromate(BrO-3) formation during ozonation process by using raw water from the Huangpu River and the Yangtze River.The results showed that the bromide(Br-) level was very low in the Huangpu River raw water,thus leading to very low risk of violating national standards in terms of bromate formation by ozonation treatment.However,bromide ion(Br-) as high as 103.5 μg/L was found in the Yangtze River raw water.Ozonation tests indicated that 15.2 μg/L of BrO-3 was formed after 30 minutes of contact time when the dissolved ozone,pH,initial Br-, and temperature were 1.6 mg/L,7.3,100 μg/L and 25 ℃ respectively,which was higher than 10 μg/L,the limit defined by the national standard GB 5749—2006.Results also demonstrate that BrO-3 formation could be well controlled by decreasing the values of operating pH,initial O3 concentration and/or temperature.Furthermore,the linear relationship was observed between ct value and bromate production during ozonation process in Yangtze River raw water,while the linear relationship was not observed between OUT value and bromate production during experiments,which implied that OUT could not be used to calculate bromate production as ct.