| Environnement, ingénierie & développement |  |
N°66 - mars 2014
1. Éditorial n°66 Déchets Sciences et Techniques
Créée il y a près de 20 ans, “Déchets Sciences et Techniques” est aujourd’hui encore l’unique revue scientifique francophone à comité de lecture affichant la gestion des déchets comme positionnement thématique principal.A l’heure où les déchets sont rebaptisés “ressources alternatives” ou “ressources secondaires”, au moment où les principes de l’écologie industrielle et de l’économie circulaire leur offrent une place centrale dans les flux de matière et d’énergie échangés au sein d’un territoire, à l’époque donc où les déchets ne font plus parler d’eux qu’habillés de ces étiquettes, la pertinence du titre et du positionnement de la revue est questionnable. On peut d’ailleurs constater que parmi les 5 articles publiés dans le présent numéro, un seul fait apparaître le mot “déchet” dans son titre et/ou ses mots-clés.Les déchets sont-ils pour autant devenus une préoccupation révolue ? N’y a-t-il plus que de “l’or dans nos poubelles” ?
2. Caractérisation géotechnique des sédiments de dragage marins en vue de leur valorisation en techniques routières
In order to receive modern ships with more important size and to avoid different harbours entry siltation, significantly dredging operations are constantly required ever y year. These ports activity generate a great quantity of dredged marine sediments. In France, this quantity exceeds 45 Mm3/an. Immersion is usually adopted with respect to the national and international regulations. However, marine sediment management is facing legal, financial, technical and social difficulties that need innovative, economical and sustainable solutions and more restrictive environmental regulations.This paper presents and discusses the first results of physical and geotechnical characterization of sediments sampled from different French ports. Knowing that the variability of the sediments characteristics is one of the limits to their reuse in geotechnical applications, the results will be presented and put in prospect towards this variability and the reuse of sediment as a subgrade layer.The different sediments are classified from a geotechnical point of view and treated with hydraulic binders. Even if the sediments belong to the same geotechnical class, they show different responses in terms of mechanical behavior and in particular, swelling and tensile strength.
3. Revue de littérature détaillée sur les tests statiques et les essais cinétiques comme outils de prédiction du drainage minier acide
Sulfidic mine wastes like tailings and waste rocks may generate acid mine drainage (AMD) when their sulfide minerals oxidize in contact with oxygen and water. AMD is considered the most significant environmental problem associated with the mining industry and therefore its prediction is of outmost importance. A reliable prediction enables to determine the type and cost of mine site remediation. AMD prediction is realized using static and kinetic testing. Static testing corresponds to acid-base accounting, which is the balance between the acid generating potential (AP) and acid neutralizing potential (NP). Static tests are widely used to determine the net neutralization potential (NNP=NP-AP) and/or the NP/AP ratio. However, this classification method involves an uncertainty area when AP and NP values are similar. In these cases, kinetic testing is used to rule out the acid generating potential of the wastes. Kinetic testing submits the material to an accelerated and controlled weathering process and gives information on the rates of sulfide oxidation and acid neutralization, the lag time before the onset of AMD, and the quality of the leachates. In this paper, the different static and kinetic tests are reviewed and compared with regards to their advantages and limits. The extensive literature review is summarized into tables on AMD prediction techniques.
4. Influence de la température sur la méthanisation de boues primaires d’épuration
The influence of temperature and organic load on the anaerobic digestion of primary sludge was studied in the range of 28-60°C with organic loads ranging from 2 to 8.5gCOD.L-1.j-1. The work was carried out from a mesophilic inoculum with prior adaptation. The incubation was conducted in 10-L perfectly mixed thermo-regulated digesters which were fed fed daily. Results showed that the daily production of methane was more influenced by the load than by temperature. The performances obtained at 28°, 37° and 49°C were found similar but slightly reduced at 55°C. The digester operated at 60°C with the highest load quickly led to acid inhibition resulting in a drastic drop of methane production. The rise in temperature lead to an accumulation of ammonium NH4+ in the digesters as well as soluble COD (measured after filtration to 0.45 microns). These variations suggested a change in the balance of biodegradation pathway. The effect of temperature on the acceleration of hydrolysis / acidogenesis phases was more acute than on the acetogenic and methanogenic phases, thereby leading to the accumulation of intermediate metabolites.
5. Valorisation des rejets miniers du district Pb-Zn de Touissit-Boubker (région orientale-Maroc)
In Morocco, several mine sites were abandoned after closure without any rehabilitation plan. These sites are characterized by the presence of significant tailings volumes, which has produced significant environmental impacts. The objective of this research is to study the use of mine tailings, sourced from the abandoned Pb-Zn district of Touissit-Boubker (Morocco), as aggregates for surface finishing mortars. The study consist firstly of a fine physical, chemical and mineralogical characterization of mine tailings, followed by an evaluation of tailings-based mortars mechanical properties. The pollution potential of the tailings based mortars was also assessed in this study. The results show that mine tailings are characterized by the presence of high fine content and significant concentrations of As, Cu, Cd, Pb and Zn. The use of tailings as aggregate produces a significant increase in the amount of water needed for mixing mortars as well as a decrease in mechanical strength. The dissolution of Pb and Zn in tailings-based mortars is very limited.
6. Etude et caractérisation des déchets ménagers de la ville de Mostaganem (Ouest-Algérie)
Our study focuses on the characterisazation of municipal solid waste in the city of Mostaganem (West Alegria) and this in order to introduce one of serval recover y processes (valorisation). For this purpose, the study was made by area (sector) and season.The collect was performed by the cleaning service of the city of Mostaganemand forwarded to the place of our work. Manual and meticulous sorting is performed for waste characterization.Analysis of physico-chemical parameters (density, fire loss, electric conductivity, the average pH, moisture level, lower calorific value, organic carbon and nitrogen) was performed on samples by applying the method of quartering.Waste generation per inhabitant and per day for the citizens of Mostaganem is 0.82 kg.inhab-1 day-1. The organic matter represents 65.5% from the waste, paper and cardboard 13%, plastic 7%, glass 4%, metals 3.5%, textile 3% and diverse 4%. These figures are comparable to those of contries being development. The study according to the seasons showed that the organic matter went to 80.3% in summer which is justified by the consumption of vegetables and fruits while the paper fall to 8,3%. Municipal solid waste of the city of Mostaganem are rich in organic matter (loss on ignition of about 62% of the dr y mass) and nitrogen (1.4%) and have a relatively high moisture content (the around 57% of the gross weight).from these data, we showed that 27.5% were potentially recyclable waste, and die the most appropriate valuation […]