| Environnement, ingénierie & développement |  |
N°5 - 1er Trimestre 1997
1. Les emballages souillés: Déchets banals ou dangereux ? Quelles solutions ?
ln relation with the product it has contained, packaging waste would be classified in non hazardous waste or in hazardous waste. lt means that for its elimination, a non hazardous packaging waste must be valorised with, if it's necessary a treatment before. ln the same way, a hazardous packaging waste could become a non hazardous waste with an appropriate treatment and so be valorised. If this is not possible, it would be treated in a hazardous waste treatment plant. ln any case, prevention (means for example to reduce the production ofwastes) is a priority to manage in a better way the elimination of wastes.
2. Étude de l’évolution d'ordures ménagères en conditions simulées de mise en balles enrubannées
This study concern the biological evolution of munici pal wastes in baies. The work has been done with semi synthetic municipal wastes. The effects of organic mat ter content, humidity and the conditions of aeration have been studied. Results show a very limited biode gradation. For the two months and a half of study, the temperature has not varied, fluctuating from 1 to 2 °C around room temperature (27 to 31 °C). The highest biogas production was 29.3 l/kg of organic matter (O.M.) for the test realized with 50 % of humidity and 25 % of organic matter, and the lowest was 8.5 l/kg of O.M. for the test realized with 40 % of humidity and 45 % of O.M. A complete anaerobic biodegradation of organic matter would have produced 292 l/kg of O.M. The relatively big quantity of volatile fatty acids at the end of the tests shows that after two months and a half, the biological evolution has remained stopped at the level of the acidogenic phase. The production of methane or H1S has not been detec ted in any of the tests. Results suggest that the baling process is a good method for storage of municipal wastes, if the aim is to reduce the waste biological evolution temporarily. The very small biological activity seems to be related to the acidification of the medium caused by the accumulation of volatile fatty acids which are produced by facultative anaerobes under anoxie conditions during the first days of incubation.
3. Extraction et analyses de composés organiques volatils (COV) dans un sol contaminé: Exploitation des résultats obtenus
We have developed an extraction and analysis of volatile organic compounds presents in contamined soils. The extraction is undertaken after sampling. The analysis is made by gas chromatography after identification by GC/MS coupling. The good results, verified by supercritical fluid extraction, allow us to conclude to the reliability of the proposed method. The obtained result examination allows to show the possibility of pollution cartography, but also to analyse the migration of pollutants according to their physical properties.
4. Le comportement de la population face à l'implantation d'une usine d'incinération
5. Traitement d'ordures ménagères. Analyse de cycle de vie de l’incinération avec valorisation énergétique et d'autres filières classiques de chauffage
lncineration with energy recovery seems to be an interesting solution to face needs of household waste treatment and heat production. These needs are analysed through an environmental approach including the life cycle concept. The incineration with energy recovery is compared with conventional systems fulfilling the functions of household waste treatment and energy production (i.e. landfilling combined with a collective or individual or urban heating system). The energy and materials used as well as wastes released into the environment are inventoried and their impacts are evaluated. In the last step, a multi-criteria analysis enables a comparison of these different systems towards the environment.
6. Solutions analytiques pour l’évaluation simplifiée de l’impact des sites de stockage de déchets sur les eaux souterraines
The transfer of contaminants from a waste-disposal site towards an environmental receptor is an essential aspect of the impact of such a site. This paper presents several analytical solutions that allow a simplified analysis of the impact of a waste-disposal site on groundwater resources. These solutions allow the estimation of the average groundwater concentration in an aquifer located below the disposai site, and of the pollutant flux at the interface between the clay barrier and the aquifer. Example applications illustrate the usefulness of these solutions, which provide information concerning the overall behaviour of the storage facility, that can be most helpful for the practician. Taking into account the impact of the storage site in the evaluation of its performance, and the role of each individual component, is necessary in order to adequately identify objectives for each component, and the means required to meet those objectives.
7. Le traitement hydrothermal des déchets ; une solution innovante
The environmental regulation evolution and the increasing wastewater disposal cost lead to a new concept of complete destruction of toxic substances and sludges. Thus, hydrothermal oxidation of wastes as an alternative technique in order to limit the risks of secondary pollution is developed. In this field, we have developed in our laboratory, in collaboration with the Electrolyse (Bordeaux - France), a continuous reactor which permits to treat 3 kg per hour of wastes containing 10 weight percent of organic compounds. After a brief presentation of supercritical water properties and technological developments of hydrothermal oxidation of wastes, we will present the results obtained in our laboratory concerning two model molecules: methanol and glucose. The influence of various parameters governing the transformation has been investigated (pressure, temperature, residence time, additive). The kinetics has been modeled for elementary compounds. This study has evidenced high destruction rates (> 99 %).
8. Une démarche intégrée pour la maîtrise de la gestion des déchets solides urbains au Cameroun
Between 1993 and 1995, the main town of Cameroon been going through a multifaceted waste management crisis. This is observed at several domain: collecting, treatment and recycling. From this situation, the town planning laboratory of the national Engineering school of Yaoundé with the financial support of some councils and International Donator undertook some operation to solve definitively the problem. At the first time, our effort has been concentrated on Douala and Yaoundé town. This paper presented the main result. Another to defined the strategy of management of garbage, an evaluation of the global flow is hence proposed. It gives a global production of 920 tons of sol id wastes in Yaounde of which 800 tons are from households; and 1232 tons in Douala, 1000 tons coming from households. In Yaounde, one phase composting has been developed in some poor neighbourhoods. This seems to be a good alternative solution as most of the population is taking to it.