Tallec, Gaëlle (2005) Nitous oxide emissions during nitrogen removal in wastemater treatment plant - The parisian conurbation. PhD thesis, ENPC.
Abstract
Biological nitrogen removal systems (nitrification and denitrification), could emitted a greenhouse gas, the nitrous oxide (N2O). The aim of this study was to estimate and identify processes and factors at the origin of N2O emissions during nitrogen removal from wastewater treatment plants of the Parisian conurbation, and to estimate their impact on global N2O emissions at the Seine basin scale. Laboratory-scale experiments allowed us to simulate nitrogen removal processes used by the Parisian conurbation - secondary activated sludge and tertiary treatment on fixed culture - and to measure N2O emissions, under controlled conditions. We have shown that N2O emissions represent 0.1 to 0.8 % of the treated nitrogen load, depending on oxygenation and methanol supply. Optimal conditions for N2O emissions were around 1 mgO2 L-1 during nitrification; around 0.3 mgO2 L-1 and a methanol supply which permit only 60 % of the total nitrate reduction, during denitrification. Experiments with specific inhibitors allowed us to identify the two major processes responsible for N2O emissions: autotrophic nitrifier denitrification and heterotrophic denitrification. Our estimates lead to present N2O emissions from WWTPs of the Parisian conurbation of 60-120 kg N-N2O d-1, which will increase to 320-480 kg N-N2O d-1 in 2005-2008 and will reach 370-750 kg N-N2O d-1 in 2012 - 2015. The emission levels could reached the lower range if the nitrification of nitrogen is realised at an oxygenation higher than 2 mgO2/L and denitrification in total anoxic conditions and a methanol addition allowing 100 % of nitrate load reduction. According to our results, N2O emissions, currently emitted in the lower Seine river which receive the effluents not treated for nitrogen, will be increased by moving them from natural environments to WWTPs. However, at the scale of the Seine basin, nitrous oxide emissions issued from nitrogen treatments in WWTPs of the Parisian conurbation (at present or in the future), will continue to represent a low ratio, 1 to 10 %, in comparison with the emissions from agricultural lands.
| Item Type: | PhD Thesis (PhD) |
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| Thesis Supervisor: | Garnier, Josette |
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| Date: | November 2005 |
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| Board of examiners: | Mouchel, Jean-Marie and Bernet, Nicolas and Martinez, José and Gousailles, Michel and Pujol, Roger and Garnier, Josette |
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| Collection (Fonds): | ENPC |
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| Institution: | ENPC |
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| Subjects: | 6. Chemistry, Physical Chemistry and Chemical Engineering |
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| Uncontrolled Keywords: | N2o, Nitrification, Denitrification, WWTPs, Activated sludge, Fixed culture, N2o, Nitrification, Dénitrification, Step, Boue activée, Culture fixée |
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