Effects of temperature and chemical addition on the formation of bromoorganic DBPs during ozonation

The effects of temperature and addition of OH radical scavengers/enhancers or HOBr scavenger on the formation of bromoorganic disinfection byproducts (DBPs) from ozonation of six raw waters were studied in true batch reactors. The formation of bromoorganic DBPs during ozonation generally increased with the increase of temperature, but might also decrease for the waters with somewhat higher values of specific UV absorbance (SUVA). The addition of hydrogen peroxide, ethanol, or ammonium dramatically decreased the formation of bromoorganic DBPs; t-butanol addition significantly increased the formation of bromoorganic DBPs; bicarbonate addition might increase or decrease bromoorganic DBP formation depending on the water source. For all the waters treated with the chemical addition, the level of total organic bromine (TOBr) varied with the same pace as that of ozone exposure (CT), which suggests that TOBr formed during ozonation may be used to estimate the CT, a measure for the achieved degree of disinfection. The results demonstrate that for each water, the correlation between TOBr and CT was less affected by the change of chemical composition of the water than that between BrO3− and CT; for a given chemical composition and temperature of a water, there generally were well-defined relationships between TOBr and CT, and bromoform and CT just as that between BrO3− and CT. The possible mechanisms behind the linear functions of TOBr or BrO3− versus CT were given. Further study is needed to examine whether the trends found in this research can be applicable for the high SUVA waters.