Two coagulated and settled waters of differing qualities and DOC concentrations, but with the same bromide concentration, 0.53 mg/L, one natural and one spiked, were studied by robust ozonation followed by biodegradation. These waters were then tested for the formation of THMs, and in some cases HAAs, following free chlorination. The formation of bromate ion during treatment was also determined. The final study involved attempts to prevent the formation of bromate ion by ozonating at low pH and by adding ammonia prior to ozonation. The results of this study were very promising. In general, the data indicate that in a water with quite high concentrations of bromide ion concentration, TTHM and HAA concentrations can be controlled by ozonation and biodegradation without excessive bromate ion formation. Future studies on waters with more typical bromide ion concentrations, at higher ozone doses and possibly with a combination pretreatment of low pH and ammonia addition should prove fruitful.