| Environnement, ingénierie & développement |  |
N°41 - 1er trimestre 2006
1. Fluides de forages : gestion, traitement et recyclage pour les travaux sans tranchée
Trenchless Technology, mainly Horizontal Directional Drilling (HDD) & Micro tunnelling using drilling fluids, has been expanding for several years. These new construction methods have undoubtedly gained wide acceptance, particularly in highly congested urban areas and in environmental engineering like soil remediation of industrial sites. In the framework of the National Project “Microtunnels” a work group of FSTT (French Society for Trenchless Technology) has proposed “a drilling fluids research program” to manage the drilling fluids used during soil’s excavation. It’s worth looking at for various criteria: technical performances, economic and environmental considerations to reduce dumping and wastage during the underground works. HDD requires the use of large volumes of drilling fluids that provide the following functions: hydraulic cutting with a jet, providing energy to the drill motor, lubricating and cooling the cutting head to reduce torque and drag, transporting drill cuttings to the surface, stabilising the hole against collapse, guarding against loss of drilling fluid into surrounding formations. The drilling mud is pumped downhole, circulates back to the surface and is collected in return the pit, then passed through machinery that separates the cuttings from the slurry. Drilling muds are bentonite based. They are very sensitive to either physical chemical contamination. During drilling operation, their physico-chemical properties are constantly […]
2. Valorisation de déchets de caoutchouc dans les matériaux de construction : cas d’un composite cimentaire cellulaire
In this work, the idea is to use rubber waste particles as a raw material, to develop a new lightweight construction materials. The objective of the research reported in this paper is to investigate the physico-mechanical properties of Aerated Cement-Rubber Composites (ACRC), based on rubber particles. The volume content ratio of the rubber particles ranged from 0% to 50%. The aerated composite was produced using a new type of proteinic air-entraining agent, in accordance with a specific aerating process derived in the laboratory. The aerated composite was produced to be used in cellular concrete applications. Results from tests performed on fresh aerated composites have demonstrated many attractive properties, such as improved workability and a high stability of air bubbles within the matrix. A study conducted on hardened composite properties has indicated a significant reduction in sample unit weight, thereby resulting in a level of compressive strength. The composite satisfies the basic requirement of construction materials, and could be used for insulated load-bearing wall this study has also highlighted the effect of the proteinic air-entraining agent on the cementrubber interaction system, as regards the composite’s compressive strength. However, an examination of the composite’s water capillary absorption reveals that the addition of rubber particles tends to restrict water propagation and reduce water absorption; sorptivity values decrease with increasing rubber […]
3. Etude de la matière organique réfractaire à la coagulation-floculation et à son procédé alternatif, l'électrocoagulation, lors du traitement d'un lixiviat stabilisé
The organic matter (OM) and more specially humic substances (HS) represents the major organic constituent of a landfill leachate. It plays a dual but a very important role in both biogeochemistry of medium and pollutant chemistry. The removal of this organic matter can be realised by the use of the classical coagulation-flocculation process or by the electrocoagulation process. The organic matter fractionation of a stabilised landfill leachate has been realised by the Malcolm & Mac Carty (1992) fractionation protocol which combines the use of non-ionic XAD resins assembled in series (DAX-8 & XAD-4) in order to divide up the organic matter in more numerous fractions. The analysis of the size of the OM has been realised by ultrafiltration (30KDa, 3KDa and 0,5KDa).The quantity of the residual organic matter is the same for the two processes but the composition of this residual matter appears different: electrocoagulation show a more important pourcent of small organic molecules.
4. LOFT-ERI : un outil d'aide au choix de filières de traitement d'eaux résiduaires industrielles
This study contributed to the automatic choice of industrial wastewater treatment lines after obtaining UV spectra. Treatment lines taken into account are: advanced oxidation processes (H2O2/UV), biological treatment, coagulation/flocculation/precipitation, activated carbon adsorption or destruction methods like incineration. For the choice of treatment processes, a UV spectra mathematical treatment aims at the determination of several parameters. A decision making tool based on the parameters and developed with Excel® has been validated with 4 different industrial samples.
5. Carbonatation des mâchefers d’incinération d’ordures ménagères : étude pilote et modélisation des effets thermiques
Carbonation of the bottom ashes resulting from the incineration of municipal solid waste (MSWI) is the main chemical reaction occurring during their weathering. In real conditions, MSWI weathering consists in a several months storage under atmospheric conditions. The carbonation of portlandite (Ca(OH)2) which is the major calcium compounds permit to reduce the soluble fraction and the pH of the aqueous solutions in contact with material. As a matter of fact, solubility of certain heavy metals (Pb, Zn…) is reduced and the risk of their mobilization is also reduced.The aim of the study is to quantify bottom ashes carbonation, by characterizing volumes of carbon dioxide likely to react with the solid. A lab-scale pilot was used. It was essentially composed by a metallic cylinder which contains approximately 10 dm3 of MSWI, which can be swept by a pure CO2 flow. Gas temperature was measured at 5 points. As a matter of fact, carbonation reaction is exothermic and temperature evolutions permit to obtain thermodynamic and kinetic characteristics of this reaction. Heat transfers in pilot were modelled to obtain these characteristics.Results obtained permit to confirm the role of portlandite. Inside the pilot, the carbonation progress according to an ascending face current. So that temperature increase very quickly and then decrease slowly controlled by conduction
6. Etude des paramètres physico-chimiques de la biométhanisation des ordures ménagères
The methanization of the domestic wastes constitutes a treatment and a technical valorization with several advantages: reduction of environmental harmful effects, production of biogas and obtaining an organic fertilizer matter. The sequence of the methanization has been realized with a fermentation reactor containing selected and ground household refuse. The main purpose of this work was the control of various parameters for the starting of the fermentation pilot in a discontinuous way and the methanization procedure, also to verify feasibility of scaling up at industrial level. Our results constitute a first step towards other experimentations to be performed in this field. A mesophilic range of temperature, a neutral acidity value, convenient stiring, a well-balanced VFA/CAR ratio are the major parameters to be controlled, in addition to the good selection and grinding of the domestic wastes. Otherwise a deficient stiring system and an excessive VFA production contribute in addition to the heterogeneous nature of wastes to the inhibition of methanogenesis process. The obtained compost is mature, humid and rich in organic matter. After valorization, it could be used as amendment for deficient soils in organic matter.