| Environnement, ingénierie & développement |  |
N°36 - 4ème Trimestre 2004
1. Stockage en profondeur des déchets nucléaires bitumés: Problématique et recherches
This work is concerned with the experimental validation of a constitutive model developed at the “Commissariat à l'Energie Atomique” to simulate radioactive bituminized waste leaching. In this aim, two types of experimental studies have been performed. First, the porosity created by water in leached bituminized waste samples has been observed thanks to an Environmental scanning electron microscope (ESEM) and quantified by standard image analysis techniques. Second, the diffusion coefficient of water in leached bituminized waste samples, a key parameter with respect to leaching kinetics, has been measured experimentally. The correlation between model-based results and experimental data on porosity profiles and water diffusion coefficients confirms to a certain extent the validity of the proposed mathematical description.
2. Valorisation des fluides de coupe usés: Partie I : cas des techniques membranaires
In order to regenerate used cutting fluid in mechanic industries, ultrafiltration has been studied firstly with a micro-emulsion (thin droplets) and secondly with a solution (less thin droplets). As well foreign oils as bacterial contamination are removed from the micro-emulsion, on the other hand, positive corrosion tests carried out on the filtrate do not allowed it reuse. On the other hand, filtrate obtained from the used cutting fluid solution can be reused as lubricant with some additive adds.
3. Valorisation des fluides de coupe usés: Partie II : cas de l'évaporation à compression mécanique de vapeur
The cutting fluids produced by mechanical industrial processes are generally eliminated by evapo-incineration. The cost of treatment can be greatly reduced by simply extracting the water contained in the cutting fluids. Mechanical compressor evaporation has been studied with industrial microemulsion. The concentration factor has a value contained between 10 and 15 and the COD of distillate is near to 3 g/l. The COD is due to evaporation of fraction of basic oil. The economical analysis presents the financial viability of this process for evaporation of a volume of cutting fluids superior at 200 m3/year in actual conditions.
4. Les agents de la bioremédiation des sols pollués par les hydrocarbures polycycliques aromatiques
Soil PAHs contamination is now becoming of great concern. This pollution has a negative impact on activities directly or indirectly related to the soil, but it has also potential consequences for human health and the quality of the ecosystem. Indeed, polycyclic aromatic hydrocarbons (PAHs) represent an important class of environmental pollutants, of which some are known to be mutagenic and carcinogenic. Consequently, the US Environmental Protection Agency (EPA) has listed some PAHs among the priority pollutants to be monitored in aquatic and terrestrial ecosystems. Bioremediation, the use of organisms for the treatment of soil pollution, have received considerable interest in recent years because of its ecological aspect and because of potential cost savings compared to conventional non biological techniques. The objective of this paper is to review findings concerning the potential of the organisms used for bioremediation of soils polluted with PAHs. At present, numerous organisms (bacteria, fungi, algae and plants) are reported to metabolise PAHs. The several enzymatic mechanisms known to be involved in the PAHs degradation by the different biological systems will be underlined.
5. Étude des surfaces et calcul théorique des sites actifs de charbons actifs par adsorption de l'acide tartrique
The theoretical calculation of the number of active sites of four activated carbon samples (2SAP/C, COM3, NC 35 and NCF O.5/2) during the adsorption of tartaric acid from solution has revealed that the number of accessible active sites on the surface increases with increased pH. It also appears that the number of active sites for the basic activated carbon (NC 35 and NCF 0.5/2) is greater than that of the acidic activated carbon (2 SAP/C and COM 3). The results obtained are in agreement with those obtained by Freundlich and Langmuir models such that the classification for the four samples is as follows: 2 SAP/C < COM 3 < NC 35 < NCF 0.5/2. It is also observed that the dispersion on the surface of the activated carbon increases with the total number of accessible activated sites and decreases with the total number of sites in the sample.
6. Évaluation du comportement à la lixiviation de déchets stabilisés/solidifiés: Apport des méthodes d'analyses multivariées
Experimental data supplied from a Leaching Test on Monolith (TLM) were analysed using multivariate techniques such as Principal Component Analysis (PCA) and Correspondence Factor Analysis (CFA). The test was applied to cement matrix containing less than 5% of an organic pollutant (naphthalene). The leachant was demineralised water or water/methanol mixtures which alcohol content were 5 or 10%. This study permits to analyse the leaching behaviour of these monolithic matrix. It reveals some relationships between the quantity of naphthalene incorporated in the cement matrix or the composition of the leachant and the release dynamics of the analysed species (naphthalene, calcium, sodium and potassium). The analysis of the correlations between experimental and simulated data ascertain the quality of the model developed for the long-term prediction of organic and inorganic species release.