| Environnement, ingénierie & développement |  |
N°73 - mai 2017
1. Analyse du cycle de vie (ACV) d’une filière de valorisation terrestre de sédiments de dragage marins contaminés
The dredging of the French harbors generates every year between 25 and 40 million tons of sediments, however few adapted treatment and valorization systems exist. Consequently, numerous research programs emerged such as SEDiGEST, which envisaged a scenario of backfill of the careers by treated marine sediments.The objective of this article is to assess results of the marine sediment terrestrial valorization systems in order to better identify the most impacting part of the systems. The assessment has been performed following the life cycle assessment (LCA) methodology via the GaBi 6 software, EcoInvent v2.2 databases with the characterization method ReCiPe.In the backfill scenario, the comparative study of the two treatments within the same terrestrial valorization system concluded that the addition of the stabilization step with hydraulic binders seems not to be beneficial and do not reduce the potential environmental impacts.
2. Éditorial n°73 Déchets Sciences et Techniques
Après le numéro 72 paru en novembre dernier, consacré au congrès E3D 2016 (« Eau, Déchets et Développement Durable ») qui s’est tenu à Lomé (Togo) en mars 2016, et le numéro 71 publié à peine un mois plus tôt, nous retrouvons avec le présent numéro 73 un rythme de publication plus habituel pour la revue. Celui-ci, avec une moyenne de 3 à 4 numéros par an, a permis à la revue DST de publier 73 numéros en une vingtaine d’années d’existence. Il résulte à la fois du nombre de manuscrits soumis pour publication par la communauté scientifique, et du taux d’acceptation résultant du travail des lecteurs qui révisent les manuscrits. Je m’efforcerai, ainsi sans nul doute que mes successeurs, à maintenir ce rythme encore au moins vingt années supplémentaires !En cohérence avec la ligne éditoriale de la revue, ce nouveau numéro regroupe des contributions de diverses équipes de recherche francophones. Ainsi, les deux premiers articles du numéro sont issus de travaux conduits par des équipes togolaises, qui ont certainement bénéficié de l’effet positif d’entrainement du congrès E3D 2016 de Lomé. Les autres articles proviennent d’équipes françaises, égyptienne et algérienne.La revue DST conserve son ambition de publier en français des articles de recherche et de retour d’expérience, avec un délai de relecture que nous nous efforçons de maintenir court, auprès d’un lectorat de scientifiques et autres professionnels […]
3. Défluoruration des eaux à l’aide des résidus du traitement des phosphates naturels et des argilites feuilletées
This study is a contribution to the development of adsorption techniques for the removal of fluoride in natural waters. The work is carried out on a laboratory scale using local geo-materials sorbents, on the one hand the residues from the treatment of natural phosphorite of Hahotoé-Kpogamé and on the other hand the attapulgite clay mineral from the costal basin of Togo. The work carried out concerns the adsorption of fluoride on those sorbents. The following parameters are batch tested on synthetic fluoride solutions: time, solution pH, geo-material dose and fluoride concentration. The fluoride is analyzed by absorption spectrometry. The adsorption yields on the phosphorite treatment residues for aqueous fluoride solutions at an initial concentration of 10 mg/L and an adsorbent concentration of 10 g/L are 49 % at pH 6.5 and 66 % at pH 4.0. In the same experimental conditions, the yields on clay minerals are 28.2 % and 36.3 %. These yields are logically improved by increasing the adsorbent dosage (from 2 to 30 g/L). Additional tests are carried out on natural water at an initial fluoride concentration of 3.76 mg/L.
4. Traitement de déchets ménagers par co-compostage avec la légumineuse Cassia occidentalis L. et quelques adjuvants de proximité pour améliorer la qualité agronomique de composts
This study aimed to improve the agronomic quality of standard composts drawn from household garbage, by co-composting with the biomass of an invading leguminous plant in Togo, Cassia occidentalis and other additives such as manure, natural raw phosphate, and the industrial ashes of cotton grains’ shells. Six composts were made in a tank; One is the standard compost derived from household garbage while others were differently mixed with each of the aforementioned additives. The maturity and the fertilizer value of the finished products were assessed through basic chemical analyses, the dosage of the AH and AF, the Visible UV spectroscopy and a phytotoxicity test. The pH of the composts drawn from Cassia remained slightly acid with an average C/N ratio of 20. They were 1.5 times richer in organic matter, namely in humic acids and retained about 1.15 times more water. Their great richness in nutriments partially explains their high salinity rate (4,3-4,60 mS.cm‑1). They had the best germination rate (93%) at a dose of 25%. The heavy metals (Cu, Zn, Cd, Ni, Pb) were largely inferior to international norms no matter the type of compost which is considered. Thus, the co-composting of household garbage with Cassia occidentalis biomass, manure, natural raw phosphate and ashes, significantly upgrades the composition of the finished products in major fertilizers and in humic acids.
5. Contribution à l’amélioration de la gestion des déchets d’équipements électriques et électroniques ménagers au Cameroun : cas de la ville de Douala
The rapid evolution of technology in recent years has undoubtedly contributed to improving the living conditions of mankind. However, this has led many symmetrically ecological consequences, including the production and accumulation of waste electric and electronic equipment (WEEE) dangerous to human health and the environment. In developing countries (DCs), these D3E only undergo a traditional and artisanal valuation due to insufficient financial, technical and logistical resources, exposing people to serious health consequences. Douala is no exception to this rule, where the present study whose general objective is to contribute to improving the management of D3E in Cameroon, particularly in the city of Douala. To do this, a questionnaire survey was conducted among 400 households installed in Douala selected by stratified random sampling. Data analysis revealed an annual output of D3E 37.4 kg / household / year for a total of 16 765.6 tons / year. Regarding management, 76 % of respondents said that they eliminate their D3E mixed with other household waste, although 77 % of them claim to be informed of the consequences of this waste. We can then conclude that the current management of D3E in the city of Douala is unsatisfactory from an ecological point of view and requires improvement in order to protect people and the environment from harmful substances contained in the waste.
6. Prise en compte de la sensibilité paysagère dans la sélection des sites d’enfouissement de déchets ménagers par systèmes d’information géographique et analyse multi critère
Open dumps are often located in urban peripheries. They are places where household and similar wastes are traditionally evacuated, but also other special waste materials like industrial and medical wastes. The emergence of such places leads to sanitary nuisances, devaluation of the places and disfigurement of the landscapes.In Algeria, regulations on waste management have gradually been strengthened. Since 2001, public dumps are forbidden; They are replaced by Sanitary Landfill. These latter must meet strict environmental protection standards (soil sealing, effluent treatment, etc.) and rehabilitation of the site at the end of the activity.However, the environmental impact assessments imposed since then on these classified installations have not integrated the notion of landscape and the role it plays in a complex and dynamic anthropized system.This paper proposes a site selection process for sanitary landfall intended for landfilling of household and similar wastes. We aim integrating the sensitive dimension of the landscape in the earliest steps of impact or feasibility studies. This process is based on two complementary phases: a multi-criteria analysis using geomatic methods to prospect suitable sites for receiving landfill activity is followed by an assessment of landscape’s sensitivity of the selected sites to validate the choices. This process has been experimented in the municipality of El Affroun - Blida province (Algeria).