| Environnement, ingénierie & développement |  |
N°37 - 1er trimestre 2005
1. Éditorial n°37 Déchets Sciences et Techniques: Après 15 ans de recherches, un grand débat se prépare sur les déchets radioactifs
La France s’est dotée en 1991 d’une loi pour organiser la future gestion des déchets de haute activité générés par l’industrie électronucléaire. Elle doit beaucoup à son promoteur, le député Christian Bataille, dont elle porte le nom. La loi Bataille a prévu d’importants travaux de recherche et a fixé un calendrier avec un rendez-vous en 2006 pour établir un bilan et proposer les nécessaires décisions. Il est donc prévu que le gouvernement saisisse le Parlement pour débattre, au printemps 2006, d’une nouvelle loi mettant en place la ou les solutions identifiées. Déjà l’Office parlementaire a lancé des auditions et publiera un premier rapport d’ici avril 2005 au Parlement. Au lendemain du choc pétrolier de 1973, la France décidait de se doter d’un parc nucléaire civil important. Ce parc est actuellement de 58 centrales de type eau légère, dont la plus ancienne a passé le cap des 20 ans. Il représente une puissance électrique installée de 60 GWe, et une production de 427 TWhe en 2004, couvrant 80 % du besoin du pays en électricité. Lors du débat national sur l’énergie qui a eu lieu en 2003, il est apparu que l’énergie nucléaire devrait continuer à occuper une place de premier plan dans la production d’électricité. Cela n’exclut en aucun cas les énergies renouvelables, mais il semble que ces énergies ne puissent, au moins à court terme et toutes seules, satisfaire les besoins de puissance exprimé. […]
2. Dépollution des sols : étude expérimentale du traitement par venting
The aromatic hydrocarbons (BTEX) and the alkanes are the majority components of the fuels. The period of time passed in the ground induced them different behaviors in the moment of depollution. The goal of this study was initially to develop a simple experimental technique and a reliable exploitation of the obtained results. In particular, we studied the effect of ageing of toluene (BTEX) and heptane (alkanes) on the depollution process by venting. In the mean time, we built a simple mathematical model based only on the physical processes which take place during the ageing and depollution period. From an assumption of homogeneity of the soil and equilibrium between the existence phases of pollutants, the model enabled us to evaluate the output of the current systems and to give the forecast of the progress of venting process.
3. Traitement par stabilisation/solidification à l’aide de liants hydrauliques des boues issues des industries de traitement de surface par galvanoplastie
The achieved works concern the treatment of strong contaminated mud originating from the industry of surface treatment by electroplating. The procedure consists in a Stabilisation/Solidification treatment with the help of hydraulic binding for the purpose of decreasing the surface through which pollutant transfers or losses are made and limiting the solubility and/or the mobility of the constituents. In fact, the ideal think would be a treatment that would make this mud completely innocuous by transforming the dangerous products into less toxic ones. The mud passes after homogenization to mixing with an amount of cement and water corresponding to the tested formulation. The thus gotten smooth dough will serve for the realization of normalised test tubs on which, after 28 days of hardening, tests of lixiviation and measures of compression resistance are carried out.The Stabilization/Solidification adsorbs physically, traps or changes the physico-chemical shape of the pollutant by forming a more stable product. The concentrations of pollutants in the treated mud are weaker.
4. Évolution de la qualité physico-chimique et bactériologique d’un effluent laitier sur un cycle annuel
The chemical-physical and bacteriological quality of an effluent produced by a dairy industry located in El Jadida city (Morocco) was studied during 12 months (March 1998-February 1999). The analyzed parameters are temperature (T), pH, suspended matter (SM), chemical oxygen demand (COD), biological oxygen demand in five days (BOD5), total Kjeldahl nitrogen (TKN-N), ammonia (NH4+-N), nitrates (NO3--N), total phosphorus (TP-P), sodium (Na+), chlorides (Cl-), metals heavy (Fe, Zn, Ni, Cd and Mn), total aerobic flora (TAF), fecal coliforms (FC) and fecal streptococci (FS). The results of the chemical-physical characterization show that the studied effluent assumes a variation more or less important during the same day for flow, temperature, pH, salinity and polluting load. The average annual organic matter concentration is very high (average COD= 6140 mg O2/l ± 10% and average BOD5= 3067 mg O2/l ± 10%), the average annual contents of nitrogen and phosphorus are significant (average TKN-N= 148 mg/l ± 10% and average TPP= 29 mg/l ± 10%). The average annual report COD/BOD5 is equal to 2 indicating the biodegradable character of this effluent. The bacteriological characterization indicates that the analyzed effluent undergoes a significant fecal contamination (FC= 2.33 104 CFU/ml ± 10% and FS= 4.00 104 CFU/ml ± 10%). The ratio FC/FS < 1 proves the animals origin of faecal contamination of dairy efluent. The obtained results reveals that the studied wastewater present a […]
5. Étude des écoulements à travers des couches de cendres volantes compactées saturées et non saturées en eau
This study contributes to the prediction of the environmental behavior of the thermal processes residues used like materials of public works. To predict the long-term behaviour of wastes, several stages are necessary of which the characterisation of waste as well as the characterisation of various pollutants transfers mechanisms in solution using leaching tests. In the case of a percolation, these mechanisms can be analysed in hydrodynamic and physicochemical term and can be modelled by considering simplifying assumptions. The adjustment of these models requires the knowledge of various physicochemical or hydrodynamic parameters. This study aims to characterise the flow through coal fly-ashes compacted in column, using tracing experiments in water saturated and unsaturated medium and to thus identify the hydrodynamic parameters necessary to the adjustment of the waste long-term behaviour prediction models in road engineering scenario (fill).
6. Étude de la dénitratation par des adsorbats naturels (chitine et chitosane)
This study relates to the preparation of three natural adsorbent materials: rough chitin, chitin and chitosane extracted starting from shellfish shrimps, in order to study the elimination of nitrates from a synthetic effluent. The process of nitrates adsorption on these supports is described using the models of Freundlich and Langmuir in its linearized form. The study of the influence of some physicochemical parameters on the process of denitratation was undertaken. And in order to approach the operational conditions of denitratation water, we were also interested to study the influence of the presence of counter ions on the elimination capacity of the ions nitrate on the chitosane. Beside, we sought the optimum conditions for desorption by using a basic solution.