| Environnement, ingénierie & développement |  |
N°22 - 2ème Trimestre 2001
1. Éditorial n°22 Déchets Sciences et Techniques: Écologie industrielle, beurre et argent du beurre
Une récente réunion des ministres de l'environnement de l'OCDE a proposé une « stratégie de l'environnement de l'OCDE pour les dix premières années du XXIème siècle » (voir le site www.odce.org). J'ai relevé l'analyse caustique qu'en a fait Herve Kempf, (le Monde du 27/05/01) et sa conclusion : « on ne peut pas avoir le beurre et l'argent du beurre ». Le journaliste résume ainsi de manière abrupte le constat fait par les ministres que « la dégradation de l'environnement a généralement progressé à un rythme légèrement inférieur à celui de la croissance économique » et qu'ainsi « les effets en volume de l'augmentation totale de la production et de la consommation ont plus que compensé les gains d'efficience obtenus par unité produite ». Pour une stratégie d'avenir, il faudrait alors découpler cet effet mécanique apparemment inéluctable d'une augmentation de la dégradation de l'environnement entrainée par la croissance économique, dont la nécessité n'est pas remise en cause. Les propositions des experts (supprimer les subventions aux secteurs les plus polluants comme l'énergie et l'agriculture industrielle et taxer les produits selon leur cout environnemental) laissent sceptique Hervé Kempf, qui considère peu convaincantes les attitudes actuelles des gouvernements des pays de l'OCDE. Croissance et environnement sont-ils définitivement […]
2. Les nouvelles exigences en matière d’évaluation de l’impact sur la santé des projets d’aménagement industriel et de transport: Analyse des applications de la démarche d’évaluation des risques sanitaires (ERS) dans le cas des installations de traitement des déchets
The assessment of impacts on human health linked to an industrial plant became mandatory through several regulations, especially the French Law of December 30th 1996 (“Law on Air”). This is complementary to the studies of environmental impact. It is achieved through an approach called Health risk assessment, which is detailed in several guidelines and is based on the following steps : i) an inventory of pollutants and their fluxes, ii) a determination of their hazards, based on available toxicological data, including dose/effect relationship, in order to set up reference doses, iii) a study of exposure of the populations (routes and levels of exposure), iiii) a characterization of the health risk, by comparing exposure levels and reference doses.
3. Les lixiviats de décharges d’ordures ménagères: Genèse, composition et traitements
This bibliographical review summarizes the main physico-chemical and microbiological characteristics of landfill leachates. Then, it reviews the latest advances in landfill organic load removal. Neither chemical precipitation nor coagulation-flocculation can eliminate more than 50 % of organic pollution. Simple oxidation, using O3 or H2O2, or adsorption are not satisfying enough to treat water to be able to release it into natural ecosystem. Nevertheless, membrane processes and advanced oxidation processes seem to be promising techniques to fully treat leachates. Bioprocesses are adapted only to effluent with high biodegradability.
4. Cendres volantes issues de l’incinération des déchets solides d’une papeterie: Caractérisation, lixiviation et valorisation
In Safripac, the use of waste paper as raw material to make paper produce important quantity of solid waste. The issues of solid waste in the paper industry has become not only an environmental concern, but also an economic one for many industries. In many cases incineration is the method to be preferred for the disposal of solid waste, and interest in this method is expected to increase. Ashes are unavoidable inorganic residues from incineration. Fresh ash from solid waste may contain up to 20 % lime (CaO). A rather natural may to dispose of these ashes is to use them as a complete or partial substitute for lime in construction materials. The incorporation of ashes allows: to decrease the quantity of mixing water, to increase the homogeneity and the compactness of the concrete and to improve its installation. These ashes acting by their smoothness, their form, their surface quality and their low density, improve the mechanical resistances of the concretes.
5. Suivi permanent et mesures ponctuelles de dioxines et furanes sur des effluents gazeux 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 l-TEQ/m3 has to be met for the clean gas of hazardous waste incinerators and likely coming up as a limit for municipal waste incinerators as well.Since a recent time new sampling’s methods have been developed. The AMESA system is one of them. It gives the possibility to realize a long time sampling with a result which is representative of a few weeks of incineration and emission. The signification of the value has been improved.
6. Étude de la qualité physico-chimique du sol d’un champ d’épandage d’eaux usées (Zemamra, Maroc)
The Zemamra wastewater is a mixture of domestic, from sugar rafinery’s waste and slaughterhouse one. In 1990, a natural lagoon treatment system was established. However, this system was not efficient because of the increasing wastewater volume as a result of the demographic expansion and the economic growth. As a matter of fact the system was useless and so system was abandoned and all wastewater is evacuated in open waste-pipe established in south west of the town where this wastewater is speeded without any control in a sewage farm of 10 ha superficies (called daya Z3). The sewage brings a cost not negligible pollution to the level of the daya Z3. The influent bring a important pollution load to daya Z3: 512 kg/day in COD (chemical oxygen demand), 227 kg/j in SS, 55,8 kg/day in TKN (total kjeldhal nitrogen) and 14,3 kg/day in TP (total phosphorus). These costs increase particularly during the countryside sugar rafinery. Indeed the sewer of the city receives in this period a part of rejects of the sugar rafinery. In order to evaluate the impact of spreading of the Zemamra wastewater relatively to daya, we have relied on such physicochemical quality of soil. The comparison physicochemical quality of the soil of daya Z3 to a witness soil (soil situated near the daya Z3 and that does not receive used waters) and others soil not contaminated, the salts and the heavy metals are more raised in the soil of the daya Z3. The electrical conductivity of the soil of the daya Z3 […]
7. Étude de la faisabilité de la désorption thermique pour les sols pollués par des molécules organiques
A better knowledge of the phenomena governing the thermal decontamination of soils allows to improve the conception of the thermal treatment processes: this study was realised in this aim. The first stage of this work was done by thermogravimetric analysis with small amounts of soils artificially polluted. The fundamental mechanisms controlling the release of typical organic pollutants from the soil matrix during the thermal treatment have been identified. Results have shown the importance of the inter-particle diffusive transport of the gaseous pollutants within the porous media and above the bed of soil. Furthermore, decontamination rate and decontamination temperature domains were easily obtained with this tool for several polluted soils. In a second time, the study of the thermal decontamination of soils was led on a laboratory-scale pilot : decontamination temperatures, residual contamination level and the toxicity of the gases released were studied. To validate the fundamental results obtained and to confirm the feasibility of the thermal desorption process at the semi-industrial scale, a thermal treatment unity (30kg/h) was developed. The influence of the main parameters (temperature, pressure, residence time and air flow-rate) was carried out for soils polluted with HAP. Treatment temperature and air flow-rate are the most important factors influencing the residual HAP level in the treated soils.
8. Caractérisation chimique, biologique et écotoxicologique des effluents hospitaliers
This present study proposes to realize the biological, physico-chemical and ecotoxicological characterization of the hospital wastewater before their discharge in the municipal sewage system. Wastewater from the infectious diseases service of a french hospital have been collected and tested. A concentration of bacterian flora of 2,4x103/100 mL lower than that of the 108/100mL generally present in the municipal sewage system was deducted for the hospital wastewater. An average report BOD5 / COD of 0,43 was determined for these effluents. The tests of toxicity MICROTOX and Daphnie show that the hospital wastewater have a high toxicity. Polluting substances of hospitable origin were identified in the effluents of the STEP. This study suggest the treatment upstream of hospital wastewater before their discharge in the municipal sewage system.
9. Modélisation chimique d’un déchet à partir de tests expérimentaux
The disposal or utilisation of waste containing materials implies the assessment of the environmental behaviour, particularly the evaluation of the leaching behaviour. The adopted methodology for the evaluation of the leaching behaviour contains a modelling step of the source term (the material in his disposal or utilisation scenario). An experimental and modelling approach was proposed here in order to identify the solid phases responsible for the chemical elements release. This approach was applied for a solidified/ stabilised MSWIBA. The mineralogical data (determined by X ray analysis) supplied the departure hypothesis for the chemical model. The experimental data obtained by applying two selected leaching tests, i.e. the “pH influence on the solubilisation” test and the “pore water” simulation test, allowed the validation of the chemical model and a quantitative determination of the solid phases.