Nitrous Oxide Emissions from Nitritation Reactors under Hypersaline Conditions

This study focuses on nitrous oxide (N₂O) emissions during hypersaline (4 % salinity) nitritation in continuously fed and mixed fixed bed reactors. In the presence of high concentrations of nitrite and ammonium, the percent yield of N₂O emissions from ammonium removed decreased with increasing dissolved oxygen (DO). However, N₂O production continued even at a high DO of 15 mg/L. Bulk ammonium concentration (not ammonia) was found to be the main controlling factor for N₂O emissions under high and low DO during both nitritation and nitrification. Reducing bulk ammonium concentrations below 1 mg N/L in the nitritation reactor under both high and low DO conditions resulted in a reduction of N₂O emissions of approximately 90 %. Under full nitrification and low DO, reducing nitrite concentrations below 0.3 mg N/L resulted in a 60 % reduction in N₂O emissions. Similar results were observed in a low salinity reactor.