NITRITIFICATION AND DENITRITIFICATION OF HIGH-STRENGTH AMMONIUM AND NITRITE WASTE-WATER WITH BIOFILM REACTORS

Two sets of fixed-film biological processes were operated separately for nitrification of ammonium and for denitrification of nitrite associated with organic compounds. High strength ammonium wastewater (50-1000 mg NH4+-N/l) could be effectively nitrified by a draft-tube fluidized bed which was operated at an extremely high loading of 1.0 kg NH4+-N/m3.day with 95% ammonium conversion and 60 to 95% nitrite formation. Additionally, a biofilm fixed-bed was employed to denitrify 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 DELTA-COD/g DELTA-NO2--N for benzoic acid. A proposed process of an aerobic nitrifying biofilm reactor combined with an anoxic denitrifying biofilm reactor in series could be employed for complete nitrogen removal.