Bromate

The Bromate anion, BrO₃, is a bromine-based oxoanion. A bromate is a chemical compound that contains this ion. Examples of bromates include sodium bromate, (N_aB_rO₃), and potassium bromate, (KB_rO₃).

Bromates are formed when ozone and bromide ion react according to the following abbreviated reaction:
B_r + O₃ → B_rO₃

Bromate is also formed in electrochemical processes, such as formation of hypochlorite ion used in municipal water processes, when bromide ion is present. Additionally bromate ion is produced when chlorine dioxide is used in water, the bromide ion is present, and the water is exposed to sunlight.

This reaction occurs in water systems where bromide is dissolved in water and ozone is used to disinfect the water, especially under high pressures. This reaction is undesirable because bromate is a suspected carcinogen. The presence of it in Coca Cola's Dasani forced a recall of that product in the UK. Proposals to reduce bromate formation include switching to atmospheric tank contact systems, lowering the water pH to between 5.9 - 6.3, and limiting the doses of ozone.