DETERMINATION OF THE INHIBITION OF AMMONIA-N AND UREA-N OXIDATION BY THE FED-BATCH REACTOR (FBR) TECHNIQUE

Nitrification of ammonium nitrogen and urea nitrogen was studied in a submerged biofilm reactor. The reactor was operated as a fed-batch rea ctor to which an excessive mass loading was applied. The increases in TKN, ammonium-N, NOx-N and NO2-N concentrations inside the reactor wer e investigated to assess inhibitory behaviour under non-steady state c onditions. The maximum ammonium oxidation rate was about 60 mg NH4-N/h that corresponded to a surface removal rate of 8.5 g NH4-N/m(2).d. Th e major factor for nitrite accumulation was the presence of free ammon ia. In the oxidation of urea where the free ammonia concentrations wer e very small no nitrite accumulation was observed. Overall, the result s showed that the fed-batch reactor technique could be applied to a ni trifying biofilm reactor to evaluate the effect of slug doses in a sho rt time period. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.