Bromate removal in a denitrifying bioreactor used in water treatment

Bromate (BrO3−), an anion with carcinogenic properties, may be present in drinking water when bromide-containing water is ozonated during treatment or when it is present in surface water used as the source. Experiments showed that the concentration of BrO3− was reduced in a denitrifying bioreactor supplemented with ethanol, when NO3− was almost completely removed. At BrO3− concentrations of 25 and 35 μg/l and a temperature of 12°C the removal rates were 0.6 and 0.8 μg l−1 min−1, respectively. Calculations based on bromate concentration profiles in the bioreactor revealed that contact times of 25–50 min will be necessary to obtain concentrations below 3 μg/l, the 10−5 cancer risk level. Furthermore, intensive post treatment of the filtrate is required to remove biomass and excess ethanol applied for complete denitrification. Therefore, bromate removal in a denitrifying bioreactor does not seem to be a realistic option in drinking water treatment. Soil passage under anoxic conditions as occurring during artificial recharge or river bank filtration may enable BrO3−-removal from (ozonated) surface water.