| Environnement, ingénierie & développement |  |
N°21 - 1er trimestre 2001
1. Éditorial n°21 Déchets Sciences et Techniques: « Du microscope au grand angle »
Le plus surprenant, à mes yeux, dans les travaux de recherche en environnement tient à l’extrême diversité des thèmes abordes et des méthodes et techniques utilisées. S’agissant des thèmes cela apparait, a la réflexion, somme toute normal puisque l’environnement concerne tous les milieux physiques (eau, air, sol) et tous les milieux vivants (végétaux, animaux, humains) et comme, de surcroit, tous ces milieux sont en interactions multiples les possibilités d’investigation confinent à l’infini. J’observe par contre, de plus en plus fréquemment, une sorte de bipolarisation des études avec d’une part des approches microscopiques et d’autre part des approches que je qualifierai de « grand angle ». Dans le domaine des déchets par exemple de grands progrès ont été réalises sur la connaissance des solides minéraux complexes avec les travaux sur la spéciation des métaux, l’identification des traces, les mécanismes de la mobilité de certaines espèces au sein de matrices solides, etc. et cette exploration, quasi « génétique » du solide a bénéficié largement des récents progrès en matière d’analyse microscopique. Parallèlement, on a vu émerger et se multiplier des travaux d’une grande ampleur macroscopique : la modélisation de la circulation des éléments au niveau d’un pays, d’un continent voire de la planète, les cycles biogéochimiques naturels et anthropiques de divers éléments, les analyses de cycle de vie […]
2. Procédé de réduction des déchets de pesticides
The absorption and the desorption of a drug model by a commercial superabsorbent, a crosslinked copolymer of acrylamide and sodium acrylate, are investigated according to various operative conditions in order to use it as a controlled delivery system of pesticide in the agricultural section. Therefore, sorption isotherms are determined as a function of active agent concentration and of the type of the release medium : air, water and soil. Simple models are set up in order to simulate the sorption kinetics in some cases. This work shows that the release of the drug model is slackened in all cases; the delay is particularly important when the superabsorbent is used with a sandy soil.
3. Évolution temporelle de la composition du lixiviat d’une décharge à ciel ouvert: Effets des précipitations
This study is based on monthly (1998-1999) sampling of domestic landfill leachates situated in Etueffont (Belfort, France). The results show that rain flows and water flows are not correlated. Overall, the measurements carried out monthly on leachates demonstrated a seasonal evolution of some chemical parameters all over the year. During summer, the rise of the ambient temperature resulted in an increase of the overall bacterial activity as shown by the decrease of the BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand) parameters and a rise of pH (8). Therefore, the BOD/COD ratio which describes the biodegradability of the medium reaches 0.18. Chloride concentrations are high (700 mg. l-1) and concentrations of total nitogen (NT) and ammonia (NNH4+) increase. During winter, the dilution induced by the rain flow points out a reversed pattern. This resulted in a decrease of the chloride concentrations (100 mg. l-1) and that of NT (198 mg. l-1). Consequently, the BOD and the zinc concentrations increase. The variation of zinc concentrations are well correlated with precipitations. This is mainly due to the heterogenous distribution of the zinc in the landfill.
4. Devenir des métaux lourds (cuivre et nickel) dans les décharges d'ordures ménagères
This paper deals with main mechanisms which are likely to increase the solubility of heavy metal trapped under reduced forms (sulfur species) in landfills. Three mechanisms were studied under batch conditions: air induced sulfur species oxidation, complexation of metals to the soluble organic matter of leachate and pH range variation. The tests carried out in laboratory upon synthetic solid sulfur phases of iron and of two metals (nickel and copper) indicate that the latter behavior is very different. Copper, the solubility of which under reduced conditions is low, is solubilized only under complete oxidation conditions and at low pH. Nickel is solubilized as soon as oxidation starts and at pH close to neutral values. Oxidation influences these metal solubilization but acidification and complexation can also contribute to increase at a significant level these two metals solubilization. These results show that these mechanisms are likely to occur in long-term landfills or when rehabilitation operations are proceeded.
5. Utilisation de la margine en tant qu’adjuvant dans le béton
In this work, we studied the incorporated proportion of Olive Mill Waste Water on the measure of Slump test. That showed that subsidence of fresh concrete increases as the amount of Olive Mill Waste Water increased. The influence of the amount of this additive on the compressive strength and specific weight of concrete was investigated. We noticed for a percentage of Olive Mill Waste Water below 0,2 %, the additive increase the compressive strength of concrete ; beyond this value, the compressive strength decreases. Regarding the concrete’s specific weight, it decreases when the rate of Olive Mill Waste Water increases by a linear function.
6. Comparaison environnementale des systèmes de gestion des déchets solides municipaux. Analyse de cas de Yaoundé au Cameroun
The evaluation of environmental impact of urban waste management systems is the objective of this work. The case of Yaounde is analysed in this paper. Four systems of management have been considered for the analyses. System 1 is the traditional collection and landfill disposal. In system 2 the biogas produced in the landfill is recovered to produce electricity. In systems 3 and 4, in addition to the collection, a centralised composting or biogas plant has been introduced before the landfill disposal of refuse. Life Cycle Assessment (LCA), has proven more adapted to evaluate these four systems. The stages which have been studied are : the collection, the transportation, the treatment, the transportation of compost on a distance of 70 km, the landfill disposal of refuse. The analysis of the different outputs has allowed to take into account six impact classes allocated by the waste management systems studied. These impact classes constitute the environmental criteria taking into account the multicriteria analysis of the four systems. At the environmental level, system 2 has been shown as the most effective.
7. Comment nettoyer des fibres cellulosiques contaminées par des impuretés minérales ?
Sorted materials for recycling contain a part of impurities, even if it is a small part. Specific thresholds have been set concerning the fibrous materials but not on the mineral impurities (sand, dust, glass, etc.).The members of FNADE of Nord-Pas de Calais have wished to fill this deficiency (at a first time for their own use). The study which they have get to do has permitted to identify technical solutions to clear of mineral materials the flows of fibrous materials (corrugated cardboard, newspapers and magazines, mixed papers) and to analyze the effectiveness of the equipment, in order to improve the quality and to secure the outlets of the materials to recycle.
8. Incinération des déchets: Essai relatif aux représentations mentales et sociales et à leurs origines
The incineration of wastes (its past, present and future) is not only a matter of technological process, but also of psycho-sociological process, which includes the production of mental and social images. Some of them have deep roots. The image of fire is strongly, ambivalent, then the image of incineration is ambiguous. This characteristic is favourable to divergent views (the pros and the cons). In spite of technical progress, the pollutants remain the sign of the imcompletion of the “purification process” and the hydra of pollution has grown a new terrific face, that is to say the dioxins. A new “fire” invades the imagination and will be difficult to extinguish.
9. Utilisation de la photooxydation UV/H2O2 pour l'élimination du carbone organique dissous (COD) dans les effluents contenant des composés non biodégradables
The purpose of this study was to investigate the use of photooxidation UV/H2O2 to remove DOC of industrial effluents and landfill leachates containing biorefractory compounds. Experiments were first conducted on a 7.5mL spiral reactor to examine the effects of pH and H2O2 dosage on DOC removal. It was observed that acidification improved the efficiency of wastewater treatment either by removing humic substances (leachate samples) or by eliminating CO32- and HCO3- ions (both leachate and industrial samples). DOC removal also increased with higher hydrogen peroxide dosage. Nevertheless, there is a dosage in H2O2 over which no improvement is obtained. DOC removal exceeded 90 % on some samples. Using best conditions obtained on spiral recator, effluents have been treated using an annular photoreactor (380 ml). Organic pollution elimination was very satisfying, which is encouraging to continue on more important pilots with several UV lamps and varying irradiation thickness.