| Environnement, ingénierie & développement |  |
N°18 - 2ème trimestre 2000
1. Valorisation de mâchefers d’incinération d’ordures ménagères: Partie 2 : étude sur le terrain (chaussées) et en laboratoires (lysimètres)
Bottom ash (BA) is the main residue obtained after incineration of municipal solid wastes. In France, its production rises 2.7 million tons annually. Utilization of BA in road works and embankments is encouraged in France but strictly regulated. In order to evaluate the environmental impact of BA used in road construction under real conditions, two road sections were studied. Nevertheless, this study requires technical and financial means which are important. In this context, a laboratory tool (lysimeter) has been developed in which it is possible to reproduce the conditions of utilization. The experiments carried out during three years, have shown a low contribution of BA on the composition of the percolation water and a low toxicity has been measured on percolates at the end of the study. The different tests carried out in lysimeters have shown a good reproducibility of the composition of the percolate. The correlation between the lysimeters and the road sections has not been clearly observed.
2. Mise au point d’une boîte à outils de tests de lixiviation pour l’évaluation du flux de polluants émis d’un déchet solide
This project aims to identify parameters controlling the release of pollutants contained in the solid waste by means of a « toolbox » comprising some simple laboratory leaching tests. The leaching tests : Pore Water simulation test (PW), Maximal Mobile Fraction test (MMF), Acid Neutralization Capacity test (ANC) and Leaching Test on Monolith (LTM) have been performed in order to characterize materials obtained by wastes stabilization using hydraulic binders. Three types of binders were used : the CPA-CEM I, the CPJ-CEM II and a binder from road construction. 1 % of PbO were added in all materials. The interpretation of results showed that the release of the pollutant species Pb (II) was controlled by the chemical context of the pore water relating to the type of cements. The setting tests allowed us to determine the fundamental parameters to initialize an environmental behavioural model for a long-term prediction of pollutant release.
3. Valorisation d’un déchet polysaccharidique : la pulpe de betterave. Applications à l’élimination d’ions métalliques dans l’eau
The fixation of metal ions on sugar beet pulp, a low-cost material, has been studied. After a simple treatment of the sorbent, the results have shown that the kinetics are fast (≤ 90 min), and the pulp presents different fixation capacities according to the metals sorbed (Ni2+ < Cu2+ << Pb2+) and comprised between 11 and 57 mg.g-1. The mode of fixation is attributed to ion exchange while a non negligible part of adsorption could sometimes occur.
4. Solidification/stabilisation des vases à base de chaux et additifs. Concepts comportementaux et lixiviation
Sludge materials pose a problem for harbour and coastal engineers in respect with the environment rules. The stabilization/solidification (S/S concept) constitutes one way to reuse them as civil construction materials. After determination the fundamental mechanisms governing the complex physical-chemical evolutions of this composites, lixiviation tests were improved in order to study the efficiency and type of contaminants mobility. The results allow to consider different mobility potentials according to the studied metals.
5. Technologies propres et traitement de surface
The application of the clean technologies to the metal finishing workshops can be obtain by three ways: the optimization, the substitution and the modification of the production process by, for example, the introduction of valorization processes. We have developed a method which allows industrialists to choose the best valorization techniques of their effluents. This method which is based upon each industrial and process constraints (technical, regulation, etc.) lead us to develop a decision support system (3R-ETS).
6. Étude de la capture du cadmium par des adsorbants à haute température
Because of its importance in incineration plants, the interaction of heavy metals with various sorbents has recently lead to a great amount of work. Most of these studies were performed with fixed bed or thermogravimetric apparatus and it is often difficult to correlate the results of these experiments with incineration flue gas conditions. The GRE laboratory has developed a drop tube furnace in order to quantify the adsorption of cadmium chloride on different sorbents in conditions representative of incinerators : short contact time, low concentrations of metal vapour and metal, high temperature. A study of the adsorption of cadmium chloride onvarious sorbents has been done. Alumina and calciumoxide were found to be more effective for cadmiumcapture than silica or alumino silica. The leachable fraction of cadmium on each sorbent appears to be very low. The influence of sorbent surface area, gas temperature, and metal vapour concentration was studied.
7. Valorisation de mâchefers d’incinération d’ordures ménagères: Partie 1 : caractérisation des mâchefers
France incinerates about 40% of its municipal solid waste (MSW), producing 2.7 million tons of bottom ash annually. Utilization of bottom ash is encouraged in France but strictly regulated. Only bottom ash meeting specific criteria and produced in accordance with a quality assurance plan can be used in road works. It is then important to study their characteristics before its utilization in real conditions. Geotechnic characteristics and low leachable fraction obtained on a studied bottom ash are in accordance with the regulation to be used in road construction. The study of its composition has shown the presence of major elements (Si, Ca, Al, S), minor elements (Cr, Mn, Cu, Pb, Ni, Zn) and trace elements (As, Cd, Hg, Se) which have been quantified.
8. Proposition d’une méthode de pré-diagnostic environnemental basée sur l’accès à l’informationApplication à des entreprises tunisiennes
Small and medium size enterprises (SMEs) play an important role in the economic growth of emerging countries. However, their environmental impact on ecosystems and population should not be neglected. A review is made of existing methods of environmental diagnostic. A new one is proposed to assess the capacity of enterprise managers to access to environmental information and use it in their technical, administrative, economic, social and decisional structures. It has been used to estimate obstacles and catalysts of integration of the environment in six Tunisian enterprises. Industrial managers who have been interviewed consider environmental integration as a strategic factor which may help them to improve their relationships with public authorities, therefore environment is rather well integrated in their decisional structure. Because of a search of optimization of production equipment, the economic structure is also generally well controlled. On the other hand, their main weak point lies in their social structure. This is mainly caused by a cultural gap between management and workforces and lack of intermediaries. Some communication dysfunction between public and private actors have also been noted. This method could be used to make enterprises aware of environmental stakes as well as to help local communities to define industrial risk for the environment and enterprises needs in order to target their environmental protection programs.