Production of greenhouse gases from biological activated sludge processes: N2O Emission Factors and Influences of the Sampling Methodology

Abstract

The biological activated sludge reactors for the treatment of urban wastewater influence the environmental impact in terms of N2O production. The quantification of this impact highly depends both by reactors configurations, gases sampling points and analysis methodologies. In this paper the predinitrification-nitrification configuration was studied in real plant (80,000 PE). The N2O production was monitored by using fixed and floating samplers and by changing the sampling point at the head and at the end of the reactor. The monitored emitted concentrations were found in the range of 0.05–1.6 mgN2O/m3. The data were affected by the used sampling method. Higher concentrations resulted for fixed sampler when the sampling ratio of the head space volume and the air flowrate was lower than 0.05 l/m3/h. The N2O mass balance showed percentages of N2O for influent TN in the range of 0.004–0.0004% N2O/TN on the basis of the sampling position.