Étude et modélisation dynamique d'un procédé par biofiltration en nitrification tertiaire

Authors: Vigne, Emmanuelle
Advisor: Lessard, Paul; Héduit, Alain
Abstract: Nitrogen removal in wastewater treatment plants becomes more and more used due to the harmful impact of nitrogen on the natural environment. After medium and highly loaded secondary treatment, practitioners could use biofiltration for tertiary nitrification, which is an intensive process adapted in areas with strong land pressures. This technology can remove very strong loading rate in a restrained space by its capacity to developp an important amount of active biomass into the filtering media. Simulation of such technique’s behaviour is not direct, and few studies led to a useful tool for engineers. However, its use is necessary in order to validate design in real operating conditions and dynamic conditions. The main objective of this work concerned the study and validation of a biofiltration model which already exists but has still never been tested with real data in tertiary nitrification treatment. In order to reach this objective, the behaviour of a semi-industrial pilot plant, fed by real domestic effluent from an activated sludge plant, was studied. In order to operate in dynamic conditions, different daily volumetric nitrogen loading rates were applied, in which dynamic peak-loads were carried out. The calibration and the validation of the model parameters were done thanks to on-line ammonia and nitrate analysers during one year and more, in association with a calibration procedure and a sensitivity analysis. The protocol required the implementation of specific tests for characterization of the biofilm inside the filtering media. These tests increased the number of the observed state variables to compare with the model predictions. That allows a better evaluation of the model robustness. At the same time, the dynamics of processes taking part in the nitrogen removal into the biofilm were investigated thanks to these specific tests. So, parameters which influence the nitrogen removal, overall performance, activity and quantification of autotrophic biomass, its solids retention time or its repartition inside the filtering media, could be determined. Combination of experimental observations and numerical modelling highlighted the capacity of the biofiltration model to provide good predictions on real nitrogen removal performances. Furthermore, this study allowed to evaluate mechanisms included in the model and their limitations with different operating conditions applied in the system. Finally, weaknesses of the model concerning solids compounds and the evolution of head loss in the pilot plant were established.
Document Type: Thèse de doctorat
Issue Date: 2007
Open Access Date: 13 April 2018
Permalink: http://hdl.handle.net/20.500.11794/19727
Grantor: Université Laval
Collection:Thèses et mémoires

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