| Environnement, ingénierie & développement |  |
N°28 - 4ème Trimestre 2002
1. Recherche de synergies matières/énergie entre secteurs industriels: Réflexions et perspectives
Industrial Ecology is an emerging field, wich gives a systemic approach of the industrial world. Recycling of industrial waste or energy excess by implementing trophic networks is one of its main tasks.Knowledge of the synergies or of the potential connections between the different industry components is a key point to increase the number of those exchanges.This paper, based on survey of for different sectors, attempts to test the interest from a sectorial point of view, and also features the limits of this approach. It then assesses the importance of a mass and energy flow functional description.
2. Écocompatibilité des eaux de percolation de déchets stabilisés: Évaluation écotoxique au laboratoire et étude expérimentale en canaux artificiels extérieurs
The aim of the research programme on wastes called Ecocompatibility, launched by the French Environmental and Energy Management Agency, was to characterize the potential toxicity of polluting flows (hazard) from waste matrices and to define the conditions of exposure without negative effects for the environnement (risk) according to several experimental studies. In order to develop, validate and calibrate this methodology, two scenarios were used for experimental studies. They correspond to percolation of water through a granular waste deposit, with a high content of metals and salts. Bottom ash from household waste incineration and lead secondary smelting slags were used for experimentation. Among the studies on environmental impact, benthic invertebrate assemblages were reconstituted in experimental systems to test and to predict the effects of some pollutants on different community variables. The experimental systems were microcosms in the laboratory (series of partitioned glass tubes) and outdoor mesocosms (artificial steel channels) for the field-like experiments. The complementarity between the two approaches has been validated: a 1:100 toxicity ratio in the experiment with lead slags showed the risk of separation laboratory and field-like studies. The former allowed to establish scales of toxicity, whereas the latter measure the ecological effects on in situ communities and on the structure and functioning of the receiving environnement. A high variability was however […]
3. Entropie et recyclage: Quelques exemples
A limit to sustainable development could be the exhaustion of some natural resources. A counterpoint is represented by a global closed-loop replenishing system, but real cycles cannot be completely closed. Concerning material systems a factor of entropy lies in losses of physical properties. However recycling is a way to reduce or slow up entropy of material systems. To reach very high recycling rates, loop recycling, and not only cascade recycling, is needed.Cases of some materials provide illustration : at first the case of paper (and cardboard) for the year 2000 at an European level (on the basis of data from the European Recovery Paper Council). The case of plastics is surveyed too ; by comparison with paper, their recycling rates are low ; however not only mechanical recycling but also chemical (feedstock) recycling and energy recovery have to be taken into account. Another case is aluminium, with a high recycling rate, and the case of glass has been considered previously (Déchets, Sciences et Techniques n° 13, 1994).For a global view, the logic in terms of material entropy would have to be supplemented by energy and environmental balances and economic and social aspects.
4. Amélioration des caractéristiques du phosphogypse en vue de son utilisation en technique routière
In order to transform phosphogypsum, an industrial waste, into a material for road construction, many studies of characterization, mechanical behavior, durability and environmental impact must be done. Our paper presents a contribution to the valorization of Tunisian phosphogypsum in road construction. First we confirmed that phosphogypsum presented a bad mechanical behavior in damp curing conditions and especially in presence of water. This deterioration of the material in water can largely be explained by a phenomenon of decohesion of phosphogypsum particles by water, supported by its acidity. To increase the pH and improve strength, we used several additions: sandy-silty soil, lime, portland cement and blast furnace slag. The addition of Tunisian slag and lime allowed to get enough strength: 3 MPa in compression and 0,5 MPa in tension after 28 days in dry curing conditions, and only 30 % lower if a contact with water takes place after 7 days of dry curing conditions.
5. Adsorption de l’iode par des charbons actifs de rafles de régimes de palmes
The iodine-iodide-water system has been used to study adsorption by activated carbons obtained from local Cameroonian palm-tree cobs. The adsorbent is characterized in terms of micropore volume and effective surface area as provided by the Langmuir theory and Freundlich theory of adsorption. It was found that iodine adsorption is not restricted to monolayer coverage and that filling of transitional porosity occurred. The correct isotherm must employ free iodine concentration and not total iodine concentration. Thus, we have been able to establish factors that influence the preparation of the activated carbons and in particular the enlargement of their pores – conditions tied to their method of activation.
6. Biolysis E & Biolysis O: Deux innovations technologiques pour la réduction de la production de boues à la source
Management of the excess sludge production resulting from biological wastewater treatment is one of the most important economic and environmental issues for the next decade. Due to the intensification of wastewater treatment, a large increase in sludge production from biological processes must be anticipated. Moreover, sludge agricultural valorisation and landfilling, which are the main solutions adopted for final sludge disposal, are debated and sludge incineration cannot be a systematic solution. So, new stringent regulations regarding sludge treatment and disposal imposed in several countries as well as social and environmental concerns, have resulted in an increasing interest in emergent processes aimed at the reduction or minimization of excess sludge production. Following a 5 years on-going research program, Ondeo-Degrémont has developed a new set of processes designed to reduce sludge production inherent to biological wastewater treatment: Biolysis. The results presented in this paper relate to two case studies aimed at assessing the effect of Biolysis O and Biolysis E associated with an activated sludge process. This paper highlights results concerning reduction of sludge production and provides a comprehensive and accurate set of results dealing with the influence of Biolysis processes on the remaining sludge and effluent characteristics. An economical evaluation of the Biolysis technologies is also provided.
7. Développement de nouvelles méthodes de caractérisation des boues de rectification
The aim of the paper is to study new methodologies for a simple and fast estimation of the organic content of an oily solid waste largely produced by the metal working industries: the grinding sludges. Primarily, a measure of weight loss after low temperature pyrolysis is performed. This procedure proves efficient for the quantification of global organic matter of the sludge. In the second instance, an extraction step with n-hexane is carried out and the dilute extract is then analysed using UV spectrophotometry. UV spectra exploitation by a deconvolution method which compares grinding sludge extracts to reference spectra corresponding to oils used in metal processing allows the separate quantification of cutting fluids and lubricants. UV spectra also provide qualitative information on oil evolution by the way of the search of isobestic points.
8. Evolution des paramètres physiques et mécaniques d'un déchet stabilisé soumis au vieillissement
The physical and mechanical features study is essential for assessment of stabilized waste long term behaviour. Particularly, this could be carried out using classical mechanical tests (Rc, Rt), which have to be coupled with accelerated aging tests (H/S, G/D). In order to check the relevance of these tools, two successive stages of aging have been effected, the first one natural, the second one artificially accelerated. During the accelerated aging, the evolution of the following parameters was measured : weigh of the samples, mean pore radius, porosity and wet apparent density. Classical mechanical tests (Rc et Rt measurements) were performed in parallel. This study gives data on the influence of aging on the evolution of physical and chemical characteristics of the stabilized waste matrix.
9. Éditorial n°28 Déchets Sciences et Techniques: Argent public, argent privé : une nécessaire synergie.
Le CNRS a inscrit dans son contrat d’action pluriannuel 2002-2005 cinq axes prioritaires, dont l’un concerne l’Environnement, l’Energie et le Développement Durable.Un objectif affiché par le CNRS est en particulier de devenir un acteur de premier plan de la recherche en Environnement et Energie en Europe et dans le monde. Pour cela il faut inciter les laboratoires à s’investir dans une recherche par essence interdisciplinaire, en relation avec les autres organismes de recherche et les industriels. Un colloque a réuni en décembre environ 400 chercheurs du CNRS et des grands organismes concernés (INRA, BRGM, CEMAGREF, CIRAD, CNES, IRD, LCPC, IFREMER…) pour établir la synthèse des travaux de prospective qui se sont déroulés pendant l’année écoulée (http://www.insu.cnrsdir.fr/pdf/prospective_sic.pdf).Une programmation de la recherche sera pilotée par l’INSU (Institut National des Sciences de l’Univers) qui devient l’INSUE (E comme environnement). Cet institut transversal par rapport aux diverses directions du CNRS (Sciences de l’Univers, Sciences de la Vie, Sciences Humaines et Sociales, Sciences pour l’Ingénieur, Sciences Chimiques…) aura comme mission de structurer des actions collectives de recherche et d’affecter les moyens nécessaires à leur mise en œuvre. La mobilisation des chercheurs est aujourd’hui forte pour s’engager hors des « sentiers battus » de leurs champs disciplinaires respectifs et très nombreux sont les […]