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 mu g/l and a temperature of 12 degrees C the removal rates were 0.6 and 0.8 pg 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 mu g/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. (C) 1999 Elsevier Science Ltd. All rights reserved.