Nitritification and Denitritification of High-Strength Ammonium and Nitrite Wastewater with Biofilm Reactors

Two sets of fixed-film biological processes were operated separately for nitritification of amnonium and for denitritification of nitrite associated with organic compounds. High strength amnonium wastewater (50-1000 mg NH4+-N/l) could be effectively nitritified by a draft-tube fluidized bed which was operated at an extremely high loading of 1.0 kg NH4−1-N/m3.day with 95% amnonium conversion and 60 to 95% nitrite formation. Additionally, a biofilm fixed-bed was employed to denitritify the high strength nitrite (200 to 1000 mg NO2−-N/l) associated with organic compounds of glucose, acetate and benzoic acid. Complete nitrite removal could be achieved with sufficient HRT and COD/NO2−-N ratio. The conversion ratios were estimated experimentally at 2.5 for glucose and acetate, and 2.0 g ∆COD/g ∆NO2−-N for benzoic acid. A proposed process of an aerobic nitritifying biofilm reactor combined with an anoxic denitritifying biofilm reactor in series could be employed for complete nitrogen removal.