Modeling Nitrogen Removal, Including Greenhouse Gas, for a Biofiltration Wastewater Treatment Plant

Abstract

Nitrous oxide (N 2 O) is a major greenhouse gas, heavily contributing to global warming. N 2 O is emitted from various sources such as wastewater treatment plants, during the nitrification and denitrification steps. ASM models, which are commonly used in wastewater treatment, usually consider denitrification as a one-step process (NO 3 -directly reduced to N 2 ) and are as such unable to provide values for intermediate products of the reaction like N 2 O. In this study, a slightly modified ASM1 model was implemented in the GPS-X TM software in order to simulate the concentration of such intermediate products , NO and N 2 O) and to estimate the amounts of gaseous N 2 O emitted by the denitrification stage (12 biofilters) of the Seine-Centre WWTP (SIAAP, Paris). Simulations running on a one-year period have shown good agreements with measured effluent data for nitrate and nitrite. The calculated mean value for emitted N 2 O is 4.95 kgN-N 2 O/d, which stands in the typical range of estimated experimental values of 4 to 31 kgN-N 2 O/d. Nitrous oxide emissions are usually not measured on WWTPs and so, as obtained results show, there is certain potential for using models that quantify those emissions using traditionally measured influent data.