Pilot studies were performed to study the effect of ozone dose (0.6-3.5 mg/L), pH (6.0-7.5), and contact time (12-38 min) on bromate (BrO3) formation, for different sand-filtered water qualities from the Neuilly-sur-Marne Treatment Plant (COT 1.3-2.2 mg/L, TAC 190-230 mg CaCO3, [Br-] 25-50 μg/L, and T 5°-26°). Whatever the water quality studied, the main factors affecting bromate formation were ozone dose, pH, and a cross factor between them. Bromate formation was proportional to bromide concentration, and to increase only slightly with temperature, depending on the ozone dose and the pH. Temperature has an important effect on disinfection, especially when considering Cryptosporidium inactivation, resolving the challenge of ensuring disinfection while limiting bromate formation was quite easily achievable, at intermediate temperatures, and with more stringent conditions at high temperatures (because of bromate formation) or at low temperatures (because of disinfection).