Evaluation of Disinfection By-products Formation During Ozonation of Bromide-Containing Groundwater

Abstract

Ozonation of natural waters containing bromide ion leads to the formation of inorganic bromate and many organic by-products, only a few of which have been identified. The object of this article is to identify primary ozone disinfection by-products (DBPs) and to ascertain the effects of bromide (Br⁻) concentration, pH, natural organic material (NOM) characteristics, ozone dosage, and other water quality parameters on their formation in ozonated waters derive from seven groundwaters. The results of this study show that bromate formation is favored at high pH, high initial bromide concentrations, and high ozone dosage, but low dissolved organic carbon (DOC), and ammonia levels. On the other hand, organic by-products were favored at low pH, high bromide levels, and high O₃/DOC ratios. In general, bromoform (CHBr₃) and aldehydes concentration first increased, then diminished, as the dosage of ozone was increased. Ammonia appears to reduce both bromate and bromoform. Additional brominated organic by-products produced via ozonation of a variety of groundwaters in this study were monobromoacetic acid (MBAA), dibromoacetic acid (DBAA), 2,4-dibromophenol (2,4-DBP), dibromoacetonitrile (DBAN). The levels of these by-products are affected by the water quality characteristics. The background organic nitrogen (organic-N) content of the different water sources may be correlated with amounts of DBAN formed. It was also found that the characteristic of organic precursors have significant influences on brominated organic by-products formation. Humic acid demonstrated the highest CHBr₃, DBAA, and 2,4-DBP formation, whereas hydrophilic neutral produced less CHBr₃ and 2,4-DBP than the rest of the organic fractions but produced the highest amount of DBAN.

Keywords:

• Ozonation
• Bromide
• Disinfection by-product
• Humic acid
• Hydrophilic neutral

Acknowledgments

The authors thank the National Science Council, R.O.C. for financial support of this research under contract No. NSC 90-2211-E-241-005.