BROMATE REMOVAL IN A DENITRIFYING BIOREACTOR USED IN WATER TREATMENT

摘要

Bromate (BrOs), 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 BrO~-_3 was reduced in a denitrifying bioreactor supplemented with ethanol, when NOs was almost completely removed. At BrO~-_3 concen- trations of 25 and 35 / mug/l and a temperature of 12 deg C the removal rates were 0.6 and 0.8mu g l-1 min-1, respectively. Calculations based on bromate concentration profiles in the bioreactor revealed that con- tact times of 25-50 min will be necessary to obtain concentrations below 3 mu g/l, the 10~-3 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 BrO~-1_3-removal from (ozo- nated) surface water