[Departement_IRSTEA]GMA [TR1_IRSTEA]21 - TECHNEAU / EPURE | International audience | This study deals with wastewater treatment plant (WWTP) loading and performance when receiving combined sewage. A yearly data set from an activated sludge plant operating at very low food-to-mass ratio (F/M) and being intermittently aerated was analyzed statistically to compare loading and discharge during dry and wet weather. The results show that despite some loading increase, the nitrogen removal performance is only slightly affected by rain, whereas higher soluble COD load discharge is observed. This approach was supplemented with dynamic simulations with the Activated Sludge Model No 1 (ASM1). It was first calibrated on data from an intensive 48-h dry weather sampling campaign at 20 °C. A good fit between simulated and measured variables was obtained after adjusting five parameters of the ASM1. This parameter set was then validated on a wet weather sampling campaign. Once the confidence in the simulations' results was established, several wet-weather scenarios were simulated, with maximum flow and variable pollutant loading. They show that the higher COD load discharge is due to a hydraulic flush of soluble inert compounds, and how the biological potential can be used to treat almost any realistically possible carbon and nitrogen overload. | Cette étude traite du comportement d'une station d'épuration en temps de pluie. Dans un premier temps, les données routinières d'une station par boues activées faible charge aérée de façon intermittente ont été analysées statistiquement pour comparer les affluents et effluents temps sec et temps de pluie. Il ressort de cette analyse que, malgré une hausse des charges entrantes à la station en temps de pluie, la performance au niveau de l'enlèvement de l'azote n'est que peu affectée, alors qu'on observe une augmentation de la charge de DCO soluble rejetée. En deuxième lieu, pour compléter cette analyse, une simulation dynamique du comportement de la station en temps de pluie a été effectuée à l'aide du modèle ASM1. Le modèle a tout d'abord été calé à l'aide de données récoltées lors d'une campagne intensive d'échantillonnage de temps sec de 48 h. Une bonne représentation du comportement de la station a été obtenue en ajustant 5 paramètres du modèle. Le calage a ensuite été validé avec des données récoltées en temps de pluie. Par la suite, plusieurs scénarios de temps de pluie, avec le débit nominal maximal et des charges variables, ont été simulés pour vérifier et expliquer le comportement de la station en temps de pluie. Les résultats montrent que l'augmentation de la charge de DCO soluble dans l'effluent de la station est due à un lessivage hydraulique de la DCO soluble inerte, et que le potentiel biologique peut être utilisé pour traiter toute charge supplémentaire d'azote ou de carbone susceptible d'arriver en temps de pluie.

International audience | The aim of this paper is to show the impacts of the vertical discretization in a physical soil numerical model on the calculation of the heat and mass transfer equations. The Simple Soil Plant Atmosphere Transfer (SISPAT) model was used in this study. It solves the coupled equations of mass and energy transfers in the soil and can deal with several horizons for vertically non-homogeneous soils. A series of numerical experiments have been performed to assess the influence of the vertical resolution grid on the simulation of the heat and water transfers using the SISPAT model in a one horizon configuration (homogeneous soil). In the studied case, a minimum of 20 layers has been found for a single 1.4 m thick horizon. Based on this analysis, numerical tests have been performed using SISPAT in a four horizons configuration. Key words: soilatmosphere exchanges, numerical model, vertical resolution, heat and mass transfer.

This paper proposes a direct and continuous method to measure convective heat flux (phi(c)) during batch deep-frying, based on signal reconstruction techniques applied to local oil temperature measurements. The method was applied on the assessment of convective heat transfer of 1.5 mm thick cassava slices, for various conditions of stirring and oil temperature (140-160 degreesC), and validated independently from mass balance results on slices. Finally, frequency information on the dynamic of convective heat transfer was used to propose a mechanistic interpretation of internal coupled heat and mass transfer identified within thin materials. Three regimes of coupling were identified during the first minute of frying and were respectively related to (i) an unstable superficial vaporization with phi(c) values higher than 100 kW m(-2), (ii) a regular internal vaporization with phi(c) values oscillating between 15 and 35 kWm(-2) controlled by liquid water transport from core, (iii) a decreasing vaporization rate subsequent to the rapid vanishing of the saturated region.