High nitrite buildup during nitrification in a rotating disk reactor.
Incomplete nitrification with high nitrite accumulation has three practical advantages: lower oxygen consumption, less need for organics for denitrification, and lower sludge production during denitrification. Nitrification leading to high nitrite formation was experimentally studied in a continuous single rotating disk reactor (RDR) and compared to a modeled continuous completely stirred tank reactor (CSTR). The results of this model show that to accumulate nitrite greater than 50% at oxygen levels higher than 3.5 mg O2/L, pH levels higher than 8.5 and 9.0 are required for a CSTR with and without cell washout, respectively. For a CSTR without cell washout at pH 7 and 1 mg O2/L, it was predicted that a nitrite accumulation less than 5% could be reached. Conversely, for a partially submerged continuous RDR without any additional aeration supply (already at pH 7 and 1.3 mg O2/L), high nitrite accumulation (more than 75%) was achieved and the influence of pH from 7 to 9 was not significant. This difference is believed to be caused by mass transfer. In addition, nitrification was observed to occur under oxygen transport limitation for a totally submerged continuous RDR.
Antileo
Christian
C
Department of Chemical Engineering, University of La Frontera, Chile. cantileo@ufro.cl
Roeckel
Marlene
M
Wiesmann
Udo
U
D019149:Bioreactors; D058440:Denitrification; D058465:Nitrification; D009573:Nitrites; D010100:Oxygen; D012722:Sewage
D009573:Nitrites; D012722:Sewage; D010100:Oxygen