The effect of organic characteristics land bromide on disinfection by-products formation by chlorination

In this study, organic fractions, namely, humic acid, fulvic acid, hydrophobic base, -neutral, hydrophilic -acid, -base, and -neutral were extracted from source water. First, the characteristics of the organic fractions, such as carboxylic acidity, phenolic acidity, ultraviolet absorbance, and aromatic content were analyzed. Then each fraction was chlorinated separately, and the THMFP, HAAFP, and AOXFP of the chlorinated water measured. Further, the effect of bromide on halogenated organic formation were also studied. The results indicate that the characteristics of the aquatic organic matter, including carboxylic/phenolic acidity, aromatic/aliphatic content, ultraviolet absorbance, appear to affect the formation of halogenated organics. Hydrophobic organics, having higher phenolic acidity, aromatic content, and ultraviolet absorbance, have higher chlorine consumption and produce higher concentrations of halogenated organics than hydrophilic organics. As far as bromide effect is concerned, the THMFP values (in mu mole/L) of humic acid were found to be decreased with increasing bromide concentration the reverse was true for hydrophilic neutral organics, while the THMFP and HAAFP variation of fulvic acid with bromide was minor. Furthermore, the portion of THMFP and HAAFP contributed by brominated species was increased with increasing bromide concentration, and the brominated THMFP and HAAFP converted from hydrophilic neutral organics were higher than those from humic acid or fulvic acid. These phenomena may be explained by the preference of aliphatic precursors to undergo bromination, while aromatic precursors prefer chlorination.