| Environnement, ingénierie & développement |  |
N°42 - Avril-Mai-Juin 2006
1. Éditorial n°42 Déchets Sciences et Techniques
La loi d’orientation sur la recherche a été votée ce printemps et l’Agence nationale de la recherche (ANR) a déjà un an de fonctionnement. Cette agence est une des composantes majeures de la réforme de la recherche en France et a géré et mis en place près de trente programmes l’an passé. Environ 1 400 projets ont été financés en 2005 pour un taux de succès moyens aux appels à propositions de 25 %. L’environnement, les nouvelles technologies de l’énergie sont parmi les thématiques prioritaires soutenues par l’ANR. Près de 100 millions d’euros ont été engagés dès 2005 sur ces thématiques et cet investissement est en progression pour l’exercice 2006.Les technologies de l’environnement constituent un domaine de recherche que l’ANR, avec le support de l’ADEME, souhaite favoriser au travers notamment du programme PRECODD (Programme de recherche sur les écotechnologies et le développement durable). L’objectif de ce programme est de favoriser l’émergence et la diffusion de technologies innovantes par un effort ciblé de recherche sur différents types de verrous technologiques mais aussi organisationnels, réglementaires, économiques et sociaux. Le programme se positionne comme un instrument visant à fédérer la communauté française par le montage de projets en partenariats public-privé.
2. Les lixiviats de la décharge de déchets urbains de la ville de Casablanca (Maroc), une pollution annoncée
Municipal solid waste (MSW) from the city of Casablanca (approximately 3 800 tonnes per day), containing 70% of organic matter (OM) has been stockpiled in a local landfill since 1986. The unsealed bottom of the landfill is a faulted quartzite formation in which unconfined groundwater flows and from which people draw water for farming and for human consumption. The leachate from the landfill has a high metallic content (lead: 0.5 milligrammes per litre) and a high daily flow estimated to be 1 400 m3 per day. It originates from the water contained in the organic matter, seeping into the aquifer and polluting it. It flows through a mainly agricultural area towards the city along the fault lines of the quartzite formation. Its environmental impact becomes more important due to the increase of its quantity produced by more stockpiled MSW, and occurring of drought.
3. Etude des échanges d’azote minéral entre les gels de polyacrylamide et une solution minérale nutritive dans un réacteur biologique de nitrification
We have conducted a study concerning the nitrification in a three phases biological reactor. First, a selection of the nitrifying bacteria was done by using an activated sludge taken from the biological and aerated tank at the waste water treatment plant. Then the nitrifying biomass selected was fixed on a granulated polyacrylamid gel to convert ammonia into nitrate. The chemical analyses show that 98 to 99 per cent and per day of ammonia were converted into nitrate. The immobilisation media absorbs a large quantity of ammonia and nitrates in the reactor. Substrate exchanges and other inorganic elements are continuous between solution and gel. In this way, when ammonia concentration decreases in the solution, a part of substrate absorbed by the media is released in solution until totally ammonia exhausting from reactor.
4. Influence du carbonate de sodium anhydre sur l’extraction de l’huile à partir d’un grignon d’olive humide
In this work, we shows that the addition of the anhydrous sodium carbonate to wet olive cake has an influence on the oil yield extracted using hexane.The model of Madueno applied to the experimental results obtained gives good adjustments. The elaborate statistical model according to the extraction time, the content sodium carbonate in the wet olive cake and the interaction between these two parameters gives results in agreement with those given by the experiment.
5. Action bactérienne sur un mâchefer d'incinération d'ordure ménagère
Micro-organisms such as bacteria are likely to be present in the weathered municipal solid waste incinerator (MSWI) bottom ash that will be used as aggregates in road construction. Microbial activity may impact the weathering process of such material and thus the rate of leaching of potentially toxic elements. Indeed, the deterioration of rocks, like that of materials of anthropogenic origin (stained glasses, cements, blast-furnace slags), depends partly on organic compounds and micro-organisms. However, the exact role of micro-organisms remains poorly understood. Some authors suggest that they play a considerable part in the degradation of stained glass in cathedrals but they do not specify neither the mechanisms, nor even the type of micro-organism (bacteria, fungi, lichens) involved. Other authors are of the opinion that bacteria accelerate the deterioration of marine basaltic glasses due to the observation of “hair channels” that could represent bacterial activity. In our opinion, the exact role of micro-organisms remains to be demonstrated apart for some well-defined materials: degradation of books by fungi and metal drains by bacteria like Thiobacillus. There is no existing experimental validation of the role of bacterial action in the degradation of complex silicates such as the glass contained in MSWI bottom ash. The major difficulty is to measure in such complex media the rate of deterioration with reliable tracers.Although studies have been conducted on the role […]
6. Réhabilitation d’une lagune de déballastage par combinaison enceinte active / stabilisation in situ : une solution originale et économique
La réhabilitation présentée concerne une lagune située dans le port de Brest, dédiée à la récupération de résidus provenant du déballastage des navires. La solution retenue associe deux techniques complémentaires :-Traitement par inertage in situ pour réduire le relargage des hydrocarbures ;-Construction d'une barrière active permettant de récupérer les éventuels lixiviats résiduels. Grâce aux améliorations géotechniques apportées par le traitement d'inertage ainsi qu'aux garanties à long terme fournies par la barrière active, cette solution permet la réutilisation du site à des fins industrielles telles que la construction de réservoir, parkings, routes d'accès… Cette approche paraît être un bon compromis en termes de coût et de considérations techniques pour la réhabilitation de lagunes industrielles.
7. Étude des effets combinés du glutaraldéhyde et des surfactants contenus dans les effluents hospitaliers vis-à-vis de Daphnia magna
Glutaraldehyde and surfactants are widely used in hospitals. These substances were detected in urban sewer network and in surface water. The ecotoxicity of hospital wastewater has been reported in the literature, which identifies detergents and disinfectants as principal cause of toxicity. The aim of this study was to determine combined effects of glutaraldehyde and three surfactants towards Daphnia magna. Three binary mixtures were studied in five predefined ratios: the glutaraldehyde with SDS (an anionic surfactant) then TX- 100 (a non-ionic surfactant) and finally CATB (a cationic surfactant).The joint action toxicity of binary mixtures was studied by the acute bioassay on Daphnia magna. The TI model was used to evaluate combined effects of the mixtures on the selected organism. An additive effect was observed between glutaraldehyde and surfactants and that for all the studied ratios. Additive action could be a good method to evaluate hospital wastewater effect on Daphnia magna. Moreover, these results lead to better knowledge of the mechanism of action of pollutants towards aquatic organisms. The realization of new binary mixtures using some other disinfectants could be envisaged to generalize our conclusion with the whole of the binary mixtures of detergents/disinfectants.