NITROGEN REMOVAL AND N2O EMISSION IN A FULL-SCALE DOMESTIC WASTE-WATER TREATMENT-PLANT WITH INTERMITTENT AERATION

Nitrous oxide (N2O) 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 destructi on of the ozone layer. It is therefore of great importance to develop technology that can suppress N2O emission. The effects of an anoxic pe riod on N2O emission and nitrogen removal were investigated in an actu al domestic wastewater treatment plant. When operated with intermitten t aeration, most of the N2O was emitted into the atmosphere during the aerobic period. N2O emission from the intermittent process was estima ted to be 0.43-1.89 g N2O person(-1) year(-1). Maintaining a dissolved oxygen (DO) concentration of over 0.5 mg l(-1) during the aerobic per iod resulted in the complete conversion of the influent NH4-N to NO3-N and a 60-min anoxic period was sufficient for denitrification to be c ompleted. The findings show that an optimum combination of aerobic and anoxic conditions and their suitable control are very important for i mproving nitrogen removal efficiency and controlling N2O emission.