This study evaluated the performance of oxic-anoxic fixed-biofilm reactors (FBRs) using porous ceramic sticks with plastic rings as supporting media for nitrogen and organic carbon (as COD) removal from swine wastewater. Experimental results indicate that the removal efficiency of NH4+-N increased to 86–92% from 52–98% as the volumetric ammonium-nitrogen loading rate increased to 0.25 kg NH4+-N/m3-d from 0.082 kg NH4+-N/m3-d. Furthermore, during the denitrifying column test, the average removal efficiencies for COD and NOx-N were 83 and 76%, respectively. Only small amounts of NO2−-N and NO3−-N accumulated in the denitrifying FBR. The average values for NO2−-N and NO3−-N in effluent from denitrifying reactor were roughly 2 mg/L and 6 mg/L, respectively. Approximately 82% of NO3−-N was converted into N2 by denitrifying bacteria in the denitrifying FBR. Approximately 98–100% high removal efficiencies of NOx-N could be reached in denitrifying FBR, when the ratio of CODr/NOx-Nr was controlled at 9–12 throughout the test. Microscopic observations show that cell number on the ceramic sticks in denitrifying FBR was greater than that in nitrifying FBR in the final phase of colonization.
Keywords: denitrification, fixed-biofilm reactors (FBRs), nitrification, swine wastewater