Nitrous and Nitric Oxides and the Effect of Oxygen Level and Nitrite Concentration on its Emission from Nitritation and Nitrification-Denitrification Reactors

Two different laboratory scale experiments were performed to evaluate nitric oxide (NO) and nitrous oxide (N₂O) production from ammonium-rich wastewater using both continuous stirred tank reactor (CSTR) and sequencing batch reactor (SBR). A nitritation reactor (CSTR) based on a Sharon (single reactor system for high activity ammonium removal over nitrite) process was used for the partial nitrification of 1000 mg per liter of ammonium-nitrogen (NH₄-N) resulting in a high concentration of nitrite-nitrogen (NO₂-N) in the reactor while a 12-hour cycle SBR with anoxic-aerobic phases was used for the complete nitrification and denitrification of 340 mg per liter ammonium-nitrogen of wastewater. Concentrations of NO and N₂O were measured from these reactors and the results showed that nitrite concentration in the reactor has significant effect on the production of NO and N₂O for both CSTR and SBR On the other hand, oxygen level also has a significant effect on the emission of NO and N₂O observed in the two reactors. When no oxygen is supplied to the reactor, both NO and N₂O concentrations in the off gas rise sharply while Upon gradual lowering of the DO in the reactor, the NO level decreases, but the N₂O level increases.