Impact of carwash discharge on stormwater quality (Toulouse, France)

The contribution of discharge from carwashes to pollutant levels in stormwater was evaluated. Five carwashes and two outlets in the city of Toulouse (France) were selected. Water samples were collected from December 2006 to December 2007. Concentrations and loadings of classical water quality parameters (conductivity, pH, turbidity, chemical oxygen demand, nitrogen, phosphorus, ammonium, nitrate, suspended solid and volatile suspended solid) and five groups of organic compounds (polycyclic aromatic hydrocarbons, polychlorinated biphenyls, lauryl alkyl benzene sulphonates, methyl tert-butyl ether and total hydrocarbons) were determined. The results suggest that the wastewater derived from carwashes was negligible compared to the volume and flow rates within the stormwater network. However, high concentrations of polycyclic aromatic hydrocarbons, phosphorus and lauryl alkyl benzene sulphonates in liquid waste from carwashes, and the impact of these pollutants on stormwater quality could not be neglected

Impact of dry weather discharges on annual pollution from a separate storm sewer in Toulouse, France

The city of Toulouse with its separate sewer system is ideal for studying stormwater. However, during dry weather, the storm sewer also discharges water into the environment, and it is the impact of these discharges on annual pollution from storm sewer that is the object of this study. Samples have been taken from the outlets of two storm drains located in heavily and moderately urbanized areas. Sampling has been undertaken during wet weather and during dry weather between January 2010 and February 2011. Three dry weather and two wet weather samples have been taken every three months and from each outlet. The overall pollution parameters have been analyzed (chemical oxygen demand, biological oxygen demand, total nitrogen, ammonium, nitrate, total phosphorus, suspended solid matter, volatile suspended matter, pH, conductivity, turbidity). Characterization has been completed by analysis of trace organic compounds: polycyclic aromatic hydrocarbons, total hydrocarbons, methyl tert-butyl ether, diethylhexylphthalate, nonylphenols, hormones (estradiol, ethinylestradiol). For certain parameters, the results obtained did not conform to legislative requirements concerning discharge into the natural environment. Correlations between these parameters have been studied, and identified between several of them using principal component analysis. The most important correlation observed was between conductivity and concentration in total phosphorus for one of the outlet. Results showed that dry weather had an impact on annual pollution load from separate storm sewer and that level of urbanization was also a factor. The effect of season has been studied but no significant impact was found

Monitoring of stormwater between 2002 and 2010. What is the evolution of stormwater quality ?

The city of Toulouse with its separate storm sewer system is ideal for studying stormwater. That is why since 2002, three stormwater sampling campaigns were conducted. Samples were taken from the outlets of two storm drains located in heavily and moderately urbanized areas. Sampling was undertaken during wet weather and dry weather during the year 2002 for the first campaign, during the year 2007 for the second one and during the year 2010 for the last one. The overall pollution parameters were analyzed (chemical oxygen demand, biological oxygen demand, total nitrogen, ammonium, nitrate, total phosphorus, suspended solid matter, volatile suspended matter, pH, conductivity, turbidity) and the presence of some micropollutants was studied (6 PAHs, MTBE and total hydrocarbons). Results showed an evolution of stormwater quality between the three campaigns and an improvement of nutrient and suspended solid concentrations. They indicated also that dry weather had an impact on annual pollution load from separate storm sewer and that level of urbanization was also a factor whatever the year of sampling

Optimal orientation estimators for detection of cylindrical objects

International audienceThis paper introduces low level operators in the context of detecting cylindrical axis in 3 D images. Knowing the axis of a cylinder is particularly useful since cylinder location, length and curvature derive from this knowledge. This paper introduces a new gradient-based optimal operator dedicated to accurate estimation of the direction toward the axis. The operator relies on Finite Impulse Response filters. The approach is presented first in a 2-D context, thus providing optimal gradient masks for locating the center of circular objects. Then, a 3-D extension is provided, allowing the exact estimation of the orientation toward the axis of cylindrical objects when this axis coincides with one of the mask reference axes. Applied to more general cylinders and to noisy data, the operator still provides accurate estimation and outperforms classical gradient operators

Contribution of X-ray CMT and image processing to the modelling of pyrocarbon Chemical Vapour Infiltration

International audienceThe Chemical Vapour Infiltration (CVI) process is used to fabricate the pyrocarbon matrices of C/C composites. This process involves complex physico-chemical phenomena such as the transport of precursor, carrier, and by-product gases in the reactor and inside a fibrous preform, heat transfer, chemical reactions (pyrolysis and deposition), and the structural evolution of the preform. It is able to provide high-quality materials because the processing conditions are rather mild with respect to the fibres; however it is expensive and sometimes difficult to optimize. This process has been the object of extensive modelling efforts, because of imperative optimization needs. The present work presents an approach suited to the exploitation of computerized microtomographs of C/C composites, which features image acquisition, computation of geometrical and transport properties, and infiltration modelling, as applied to the infiltration of needled carbon fibre fabrics. Another application to the reinforcement of carbon foams is also presented, as an example of inserting this approach in a global modelling strategy

Non-parametric synthesis of laminar volumetric texture

International audienceThe goal of this paper is to evaluate several extensions of Wei and Levoy's algorithm for the synthesis of laminar volumetric textures constrained only by a single 2D sample. Hence, we shall also review in a unified form the improved algorithm proposed by Kopf et al. and the particular histogram matching approach of Chen and Wang. Developing a genuine quantitative study we are able to compare the performances of these algorithms that we have applied to the synthesis of volumetric structures of dense carbons. The 2D samples are lattice fringe images obtained by high resolution transmission electronic microscopy (HRTEM)

Prédiction de la structure et des propriétés de pyrocarbones à partir d'une reconstruction à l'échelle atomique

National audienceNous présentons ici une approche originale permettant de construire des modèles à l'échelle atomique de matériaux nanotexturés à partir de leurs images de Microscopie Electronique en Transmission à Haute Résolution (HRTEM). Partant d'une image HRTEM filtrée à hautes et basses fréquences (a), un ensemble de descripteurs statistiques est collecté puis imposé à une synthèse d'image 3D aléatoire (b). Cette dernière est ensuite utilisée comme champ de potentiel attirant les atomes sur les franges lors d'une simulation de trempe d'un liquide de carbone par dynamique moléculaire (c). Une simulation d'image HRTEM à partir du matériau virtuel obtenu permet de valider la qualité de la reconstruction (d). Nous présentons en détail cette méthode ainsi que la structure et les propriétés mécaniques calculées pour des pyrocarbones laminaires rugueux, tels que préparés et traités thermiquement

Structural features of pyrocarbon atomistic models constructed from transmission electron microscopy images

International audienceWe report on atomistic models of laminar pyrocarbons constructed using a combination of 2D high resolution transmission electron microscopy (HRTEM) lattice fringe image analysis, 3D image synthesis and atomistic simulated annealing. In a first step, the effectiveness of the method and the convergence of the models with respect to the quench rate are checked on small systems. Then, the nanostructural features of large fully carbonaceous atomistic models obtained from the HRTEM images of a rough laminar pyrocarbon, asprepared and after partial graphitization, are discussed. Both models show a very pronounced sp2 character (≥ 97%), essentially made of hexagonal rings (≥ 88%) and pentagonal and heptagonal rings in similar amounts (≈ 6%). The latter mostly form pentagon-heptagon pairs or networks of line defects between misoriented hexagonal domains. Numerous pairs of screw dislocations, connecting different graphene domains, are also observed while edge dislocations with unsaturated carbon atoms are almost absent. The models are validated with respect to experimental pair distribution functions, showing excellent agreement

Algorithmes non paramétriques pour la synthèse de textures volumiques à partir d'un exemple 2D

National audienceCet article traite de synthèse non paramétrique de textures volumiques anisotropes à partir d'une observation 2D unique. Nous proposons différentes variantes originales d'un algorithme non paramétrique et multiéchelle de synthèse de textures. L'originalité réside d'une part dans le fait que le processus de synthèse 3D s'appuie sur l'échantillonnage d'une seule image 2D d'entrée en garantissant la cohérence selon deux des trois vues de la texture 3D de sortie et, d'autre part, dans les stratégies de parcours 3D et d'optimisation utilisées. Les différentes variantes algorithmiques proposées sont appliquées à la synthèse de textures volumiques de matériaux carbonés, à partir d'une observation 2D unique obtenue par Microscopie Electronique en Transmission (MET). Nous développons une étude qualitative et quantitative des résultats de synthèse qui permet d'une part d'identifier les stratégies les plus pertinentes pour la synthèse et d'autre part de les comparer de façon objective à certains algorithmes de la littérature

Modelling Chemical Vapour Infiltration in C/C composites: numerical tools based on µ-CT images

ISBN 978-3-00-032049-1International audienceIn the production of high-quality Ceramic-Matrix Composites, matrix preparation is often made by Chemical Vapor Infiltration (CVI), a process which involves many phenomena such as gas transport, chemical reactions, and structural evolution of the preform. Control and optimization of this high-tech process are demanding for modeling tools.In this context, a numerical simulation of CVI in complex 3D images, acquired e.g. by X-ray Computerized Microtomography, has been developed. The approach addresses the two length scales which are inherent to a composite with woven textile reinforcement (i.e. inter- and intra-bundle), with two numerical tools.The small-scale program allows direct simulation of CVI in small intra-bundle pores. Effective laws for porosity, surface and transport properties as infiltration proceeds are produced by averaging. They are an input for the next modeling step.The second code is a large-scale solver which accounts for the locally heterogeneous and anisotropic character of the pore space. Simulation of the infiltration of a whole composite material part is possible with this program.Validation of these tools on test cases, as well as some examples on actual materials, are shown and discussed