Nitrogen Removal and N20 Emission in a Full-Scale Domestic Wastewater Treatment Plant with Intermittent Aeration

Nitrous oxide (NzO) is emitted from wastewater treatment processes. It is known as a greenhouse gas that contributes to global warming (over 200 times more per molecule than carbon dioxide) and to the destruction of the ozone layer. It is therefore of great importance to develop technology that can suppress N20 emission. The effects of an anoxic period on NzO emission and nitrogen removal were investigated in an actual domestic wastewater treatment plant. When operated with intermittent aeration, most of the NzO was emitted into the atmosphere during the aerobic period. NzO emission from the intermittent process was estimated to be 0.431.89 g NzO person-l year-‘. Maintaining a dissolved oxygen (DO) concentration of over 0.5 mg 1-l during the aerobic period resulted in the complete conversion of the influent N&-N to NOJ-N and a 60-min anoxic period was sufficient for denitrification to be completed. The findings show that an optimum combination of aerobic and anoxic conditions and their suitable control are very important for improving nitrogen removal efficiency and controlling NzO emission.