Removal of high concentrations of NO3- from nuclear industrial wastewater by using a fixed-bed bioreactor

In this work, a down-flow fixed bed anaerobic biofilm reactor filled by biological ceramsites were prepared to remove the high concentration of NO3- (> 20 g/L) from nuclear industry wastewaters. The effects of hydraulic retention time, the concentration of NO3-, the molar ratio of C/N and temperature on the removal efficiencies of NO3- were investigated. The results showed that the removal rate of NO3- with the initial concentration of 6 g/L can reach 99% or more by controlling the hydraulic retention time at 0.75 h, the molar ratio of C/N at 1.5 and the temperature over 18 degrees C. In the process, the NO2- was not accumulated, and the autotrophic denitrifying bacteria grow well in anaerobic biofilm reactors, proving a usable method for removing the high concentration NO3- from nuclear industrial wastewaters.