Nouceiba Adouani, Lionel Limousy, Thomas Lendormi, Eberhard O. Voit and Olivier Sire* Simulation of the Denitrification Process of Waste Water with a Biochemical Systems Model: A Non-Conventional Approach Abstract: Matching experimental and theoretical approaches have often been fruitful in the investigation of complex biological processes. Here we develop a novel non-conventional model for the denitrification of waste water. Earlier models of the denitrification process were compiled by the International Association on Water Quality group. The Activated Sludge Models 1–3, which are the most frequently used all over the world, are presently not adapted towards the integration of both nitrous and nitric oxide emissions during the denitrifica- tion process. In the present work, a Generalized Mass Action model, based on Biochemical Systems Theory, was designed to simulate the nitrate reduction observed in specific experimental conditions. The model was implemented and analysed with the software package PLAS. Data from a representative experiment were chosen (T ¼ 10°C, pH ¼ 7, C/N ¼ 3, with acetate as carbon source) to simulate greenhouse NO and N 2 O gas emis- sions, in order to test hypotheses about the correspond- ing bacterial metabolic pathways. The results show that the reduction of nitrate and nitrite is kinetically limiting and that nitrate reduction is limited by diffusion and support that distinct microbial subpopulations are involved in the denitrification pathway, which has consequences for NO emissions. Keywords: denitrification, greenhouse gas emissions, simulation, Biochemical Systems Theory, PLAS DOI 10.1515/ijcre-2014-0050 1 Introduction The denitrification pathway is a major component of the network of reactions that allow microbes to catabolize ammonia from animal dejections and turn it into gaseous nitrogen. One of the main pitfalls of this treatment option is that it may cause pollution transfer towards the atmosphere, since greenhouse gases are produced as intermediary reactants. In particular, the production of N 2 O and NO during the denitrification process is related to several key parameters such as the carbon/nitrogen ratio, the concentration of pollutants, the temperature, the pH, and the nature of the carbon source. Hence, modelling the denitrification pathway is expected to help with assessing which physical, chemical, and biolo- gical variables are mostly involved in the accumulation and subsequent gases emissions. N 2 O ranks third in greenhouse gases after carbon dioxide (CO 2 ) and methane (CH 4 ) and before hydrofluor- ocarbons (HFC), perfluorocarbons (PFC), and sulphur hexafluoride (SF 6 ). N 2 O only accounts for around 0.03% of total greenhouse gas emissions, but when expressed – according to the Intergovernmental Panel on Climate Change (IPCC) – in approved units of CO 2 equivalents, it accounts for 10% of the total emissions [1]. N 2 O is a powerful greenhouse gas with a very long atmospheric lifetime of 150 years and a global warming potential 320 times stronger than CO 2 . Nowadays, the atmospheric con- centration of N 2 O is about 324 ppbv and is increasing at *Corresponding author: Olivier Sire, Univ. Bretagne-Sud, EA4250, Laboratoire d’Ingénierie des Matéraiux de Bretagne (LIMATB), F-56300 Pontivy, France, E-mail: osire@univ-ubs.fr Nouceiba Adouani, Univ. Bretagne-Sud, EA4250, Laboratoire d’Ingénierie des Matéraiux de Bretagne (LIMATB), F-56300 Pontivy, France. Present address: Laboratoire Réactions et Génie des procédés, LRGP, Nancy, France, E-mail: nouceiba.adouani@univ-lorraine.fr Lionel Limousy, Univ. Bretagne-Sud, EA4250, Laboratoire d’Ingénierie des Matéraiux de Bretagne (LIMATB), F-56300 Pontivy, France. Present address: Institut de Science des Matériaux de Mulhouse, CNRS, UMR-7361, 3 bis rue Alfred Werner, 68093 Mulhouse, France, E-mail: lionel.limousy@uha.fr Thomas Lendormi, Univ. Bretagne-Sud, EA4250, Laboratoire d’Ingénierie des Matéraiux de Bretagne (LIMATB), F-56300 Pontivy, France, E-mail: thomas.lendormi@univ-ubs.fr Eberhard O. Voit, Department of Biomedical Engineering, Georgia Tech and Emory University, 313 Ferst Drive, Suite 4103, Atlanta, GA 30332-0535, USA, E-mail: eberhard.voit@bme.gatech.edu International Journal of Chemical Reactor Engineering 2014; aop Authenticated | osire@univ-ubs.fr author's copy Download Date | 11/1/14 3:02 PM