Significant levels of both bromate (BrO3-) and brominated organics, me
asured as total organic bromine (TOBr), form during ozonation of water
containing bromide and natural organic matter (NOM). Ozonation of sev
eral ultrafiltration and reverse osmosis membrane NOM isolates leads t
o approximately 17 percent of the bromide converting to bromate and 7
percent to TOBr. Depressing pH or adding hydroxyl radical scavengers d
ecreases BrO3- production but promotes TOBr formation. In the presence
of NOM, hydrogen peroxide addition lowers TOBr formation and may incr
ease or decrease BrO3- formation, depending on other water quality fac
tors. Ammonia addition decreases both BrO3- and TOBr production. Both
BrO3- production and TOBr production decrease when the initial bromide
concentration is decreased and the ratio of ozone dosage to dissolved
organic carbon is lowered.