Removing NO3- from the polluted groundwater in in-situ leaching uranium mine by DNB

The effects of main factors, such as pH of solution, the ratio of COD concentration to NO3-concentration, the different kinds of carbon sources and temperature on removing NO3- by denitrifying bacteria (DNB), are studied. The experimental results show that the suitable pH value is 6-8. When pH≤5, the removal rate of NO3- decreased. The end pH value of solution is about 7. When the ratio of COD concentration to NO3- concentration ≥1, the removal rate of NO3- is more than 90%. The suitable ratio of COD concentration to NO3- concentration is about 1-1.5. The different kinds of carbon sources affected the removal rate of NO3- and the removal effect of NO3- was the best when sodium lactate was used as carbon source. When oxidation-reduction potential (ORP) was -50-200 mV, the lower the ORP was,the faster the removal rate of NO3- was by DNB. Dissolved oxygen (DO) affected the removal rate of NO3-. When DO>1 mg/L, the removal effect of NO3- was restrained. The removal rate of NO3- increased with the increasing of the temperature. When the experimental temperature was 17 degree C, the removal effect of NO3- was also good. (authors)