| Environnement, ingénierie & développement |  |
N°19 - 3ème trimestre 2000
1. Éditorial n°19 Déchets Sciences et Techniques: Dialogue (imaginaire) entre la Société et l’Expert en environnement
Lundi matinLa Société : Aide-moi, toi, l'Expert en environnement ! J’ai toujours des tas de soucis et en plus je ne sais plus quoi faire de tous ces déchets qui m’encombrent !L’Expert : Tu dois bien les traiter, bien les valoriser, bien les recycler, bien les éliminer, pour rester en bonne santé !La Société : Ah bon ! Tu es aussi médecin pour savoir ce qui est bon pour ma santé ?L’Expert : Non, pas du tout ! Il faut que tu consultes un médecin pour savoir déjà si tu es en bonne santé.Le lendemainL’Expert : Bonjour, comment vas-tu ?La Société : J’ai été voir un médecin hier après-midi, il m’a fait peur : je risque d’attraper des tas de maladies, si je m’occupe pas de mes déchets. Il faut que je consulte des spécialistes.L’Expert : Ça ne m’étonne pas. Et lesquels ?La Société : Il m’a recommandé un écologiste, un économiste, un juriste en me disant que ce serait peut-être suffisant dans un premier temps…
2. Recherche des origines du mercure dans les boues de station d’épuration: Mise au point d’une nouvelle méthode
Water treatment leads on the one hand to purified water and on the other hand to large amount of sludge. This by-product is representative of the quality of dirty water because it concentrates its metallic pollutants. This situation limits the re-use of the sludge in agriculture. That’s why a new localization method of mercuric pollution was developed in a dirty water duct, using terrestrial bryophytes. Moreover, this method will be helpful in other places and with other pollutants, as organic ones.
3. Valorisation des agrégats issus de bétons de démolition dans la fabrication de nouveaux bétons
This study concerns the reuse and the valorization of raw waste materials. The main objective consists in the use of aggregates issued from the concrete for making a new manufactured one. In literature, many investigations have stated on the fact that the reuse of the sand (size < 5 mm) is more difficult than the reuse of gravels. Effectively most of pollutants are fine size particles thus they can be concentrated with the sand. Also the sands have a greater specific surface and so they need more water by absorption, what poses a problem at different levels of workability, for the resistance to 28 days and to the level of durability. In this study, we have decided to run tests on the resistance of mortars recycled to 100 % aged of 28 days and a number of tests have been performed on cylindrical concrete samples with only reused gravel to 100 %. Here the used aggregates are clean because waste are coming from samples tested in laboratory. That allows us to characterize the performances of concrete with reused aggregates without pollutants. Results are good, the fall of the resistance by recycling gravels does not exceed 11 % for a fixed characteristic resistance of 26 MPa.
4. Note sur les caractéristiques des profils de dioxines et furannes émis dans les gaz de combustion d’usines d’incinération d’ordures ménagères
Several mechanisms, well known with the collective term « de novo-synthesis », are leading to the formation of polychlorinated dibenzo (p) dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the flue gas downstream from combustion processes. Due to the harmonization of the EC legislation the limit value of 0.1 ng I-TEQ/m3 has to be met for the clean gas of hazardous waste incinerators and is likely coming up as a limit for municipal waste incinerators as well. This demands a lot of requirements not only referring to the flue gas cleaning devices but also to the sampling techniques, the analysis of PCDD/F and at least the overall quality assurance of the obtained results. The high reproducibility of the so called « combustion profiles » in the flue gas from municipal waste incinerators supplies an important contribution as a part aspect of the quality assurance.
5. Étude de la sorption d’hydrocarbures aromatiques polycycliques en milieux poreux naturels saturés par chromatographie éluto-frontale
The individual retention of three PAH (naphtalene, fluorene and phenanthrene) by two sands was studied by mean of column experiments, following the methods of frontal chromatography. The first sand naturally contained 2 % organic carbon, as the second one was coated with a heavy C16 apolar hydrocarbon. Column experiments show that retention is non linear, since the breakthrough curve location depends on the PAH feed concentration, and sorption and regeneration fronts are more or less sharpening or broadening, following the retention isotherm convexity. Retention by the organic sand follows a Langmuir isotherm and the initial slope is in good agreement with the prediction of the Karickhoff law. Retention on the coated sand can be described by a Freundlich isotherm with an exponent slightly greater than unity. Thus, retention is enhanced if a nonpolar hydrocarbon is present, that means that HAP propagation is lowered. The quantitative determination of equilibrium interaction parameters enables us to predict HAP transport through porous media, e.g. the results of lixiviation experiments at the pilot scale.
6. Bilans énergétiques et environnementaux de l’utilisation en cogénération du biogaz issu du traitement des eaux usées urbaines
The aim of this paper is to present a fast method to consider the energy and environmental effect of the use of biogas (resulting from municipal waste water treatment) in cogeneration. The analyzed atmospheric emissions are composed by methane and carbon dioxide, principal gases producing greenhouse effect. À spark ignition engine, as CHP cell, is used for biogas valorization. An example of calculation for a real case offers estimated values, useful to take a decision concerning a biogas plant. If biogas is composed by 65 % of methane, electric needs are provided by CHP cell for a specific production greater than 0.18 Nm3/m3 waste water and heat is provided from 69 % of methane. The results prove that the use of biogas in cogeneration offers significant energy autonomy for a municipal waste water treatment plant. The environmental impact (reduction of the presence of CH4 and the greenhouse effect) represents a significant aspect to evaluate a biogas exploitation.
7. HIPS recyclé pour la fabrication de composants de télévision
The recycling of polymers can undergo thermomechanical degradation processes with the results of a poor secondary material, regarding its properties. In this paper an investigation of rheological and mechanical properties of three samples of HIPS (high impact polystyrene, « polystyrene choc ») one virgin and two different recycled, is reported as a function of the number of reprocessing operations and of the fraction of recycled material added to the virgin material.
8. ÉVALUATION DÉTAILLÉE DES RISQUES POUR LA SANTÉ DANS LES ÉTUDES D’IMPACT ET SUR DES SITES POLLUÉS. Réalisation technique et scientifique. Approche juridique
The technical and scientific realization, and also the reglementation approach of detailed Health Risk Assessments for Impact Studies and for contaminated sites are described.This publication described in detail :– methods for definition of exposition scenarios,– exposition quantification,– quantification of health, risks,– the legal context for detailed Health Risk assessments,– the definitions of acceptable and not-acceptable risks.The use and the utility of Health Risk Assessments are described for the French legal context in civil and penal laws.