| Environnement, ingénierie & développement |  |
N°72 - N° Spécial LOMÉ, Congrès E3D 2016
1. Elimination de la matière organique par le procédé d'électrocoagulation : comparaison à la coagulation chimique
Organic matter is a major component of natural and anthropic medium. Coagulation-flocculation is as an effective technics for its treatment, but requires the addition of chemicals products and generates an important sludge. The purpose of this study had to treat a natural water of Ilauko dam (which contained natural organic matter) and a leachate from Ouèssè Sanitary Landfill (which contained anthropic organic matter) by electrocoagulation process with aluminium electrodes. The performance of these methods was determined according to the water quality. From the results, it was shown that the electrocoagulation could be used instead of the chemical coagulation, for the hydrophobic and particular organic matter fractions. The treatment efficacy depends on the origin of the organic matter: about 50% and 75% of Dissolved Organic Carbon were eliminated of natural water and leachate respectively. However, according to different removal rate of SUVA indication, electrocoagulation is more adequate on aromatic compounds. Furthermore, electrocoagulation requires an optimal dose of metal less than chemical coagulation.
2. Modélisation et simulation de l'écoulement réactif en régime laminaire ou turbulent dans un four cylindrique
The present study aims to optimize volatile organic compounds combustion during municipal solid wastes incineration. A numerical study of volatile organic compounds combustion in laminar or turbulent regime is presented.In laminar regime, mixed convection equations, associated to radiative transfer equation and a global kinetics model are proposed and solved.In turbulent regime, transfer equations associated to global kinetics model and radiative transfer equation are proposed and solved using Fluent Software. The standard k – ε model was used for the modeling of the turbulence phenomena and discrete ordinate method for radiative heat transfer. The turbulence-chemistry interaction is depicted by Eddy–Dissipation model.The results showed that the efficiency of the combustion of organic compounds decreases with the increase of the flow rate of the smokes. The turbulence parameters such as turbulent kinetic energy and its dissipation rate are strongly affected by the combustion and reciprocally, showing the interaction between combustion and turbulence. These parameters values increase with the augmentation of the flow rate of the smokes. The combustion of volatile organic compounds is more efficient in laminar regime than in turbulent regime, for this kind of cylindrical geometry of the incinerator.
3. Traitement d'une eau naturelle polluée par adsorption sur du charbon actif (CAK) préparé à partir de tourteaux de karité
The study concerns organic and inorganic pollutants and its removal from natural water (Be Lagoon) using activated Shea cake (CAK). The activated carbon CAK has the following characteristics: BET surface area is equal to 1148 m2.g-1 and the pore volume is equal to 0.607 cm3.g-1. This activated carbon is essentially microporous with the volume of micropores representing over 70% of the total pore volume. The “batch method" was used for pollutant removal and it reveals that the contact time values are equal to 10 h for BOD and 15 h for COD. A systematic study was done to assess the influence of the mass of activated carbon on its adsorption capacity of BOD and COD. The Langmuir and Freundlich isotherm models agreed with experimental data. The maximum adsorption capacity obtained using Langmuir isotherm model was 12.66 mg/g for all the organic and inorganic pollutants and 11.24 mg/g for organic pollutants only.
4. Un cas de compensation écologique dans le secteur minier : la réserve forestière Dékpa (Côte d'Ivoire) au secours des forêts et des populations locales
After an environmental assessment about gold mine’s operation, a mining company agreed to create a safe area for biodiversity offsets: Dékpa Botanical Reserve. We describe various steps conducted in order to its creation. The objective was to assess the plant diversity of this site, its value for flora conservation, availability of plants for traditional uses in the locality. The study also shows the partnership between scientific, the mining company and local people. Meetings with mining company and local communities of the 5 closest reserve villages, permits to have approval and membership of chiefs’ customary, chiefdoms. They selected 30 young people to serve as community liaisons. These will help in achieving the other development phases of the reserve. Botanical surveys identified 358 species of which 30 are among those classified as rare, threatened or different levels of endemism. These are species such as Cola lorougnonis and Drypetes singroboensis considered as very rare in Ivorian flora. Interviews of local people show that 24% of species can be used in the treatment of various diseases, for food, crafts use or timber. The creation of the Dekpa reserve was the source of improvements for the community and scientific advances. The study suggests that development of reserve activities should consider needs of local people, as their traditional knowledge may be a factor in the preservation of species.
5. Éditorial n°72 Déchets Sciences et Techniques
Ce numéro spécial de DST regroupe une sélection de 6 articles qui ont fait l’objet de communications orales lors du Colloque E3D 2016 (Eau, Déchets & Développement Durable, http://www.e3d-lome.tg.refer.org/index.php) organisé du 7 au 11 mars 2016.à l’Université de Lomé, Togo, par L’Association Innovation et Technologie de Sfax (Tunisie), les Ecoles des Mines d’Alès et de Saint Etienne (France), l’Université Senghor d’Alexandrie (Egypte) et les Universités de Lomé et de Kara (Togo). Il s’agissait de la de la 5ème édition du Colloque E3D, qui est organisé tous les deux ans. Les précédentes éditions ont eu lieu en 2008 à Hammamet, Tunisie, en 2010 à Alexandrie, Egypte, en 2012 à Agadir, Maroc, et en 2014 à Alès, France.Outre la diffusion de connaissances scientifiques, de développements techniques et de pratiques managériales en sciences et génie de l’environnement, les objectifs d’E3D sont de stimuler les échanges et le dialogue Nord- Sud entre les chercheurs, les professionnels, et les pouvoirs publics et administrations dans le domaine de l'environnement et du développement durable. Au travers de ce numéro spécial, la revue DST contribue à ces objectifs qui rejoignent parfaitement sa ligne éditoriale, comme elle l’avait déjà fait dans son numéro 62 consacré à l’édition E3D 2012 d’Agadir.L’édition E3D 2016 de Lomé a regroupé 8 conférences plénièreset une centaine de communications thématiques de […]
6. Valorisation de la jacinthe d’eau (Eichhornia crassipes) par la production de biocarburant : expérimentation
The efficient management of water hyacinth on Benin's waters remains a challenge. Moreover, given the urgency to find alternative energy sources due to the scarcity of fossil fuels, renewable energy obtained from lignocellulosic biomass is a promising route. The objective of the study is to determine the potential ethanoic water hyacinth. For this, the production of bioethanol from the water hyacinth was made chemically, which results in: a physical pretreatment of the raw material, a pre-hydrolysis with dilute acid, alcoholic fermentation yeast baker (S. cerevisiae) and batch distillation. pH measurement and content Volatile Fatty Acid in various fermented samples allowed the determination of optimal conditions for better fermentation. Indeed, 120 hours of fermentation are found to be satisfactory for optimum fermentation of water hyacinth. This required a yeast contribution of 2.5 % on the dry matter and L/S = 20. The dosage of distillate obtained after distillation of fermented mash by chronometer method was used to determine the concentration of ethanoic. Hyacinth which is 0.95 % V/V distillate from fermented biomass.
7. Application de l'impression 3D à l'élaboration de filtres en céramique pouvant servir au traitement de l'eau au point d'utilisation
Water is an indispensable resource for the survival of every human being; it’s essential for the health and a fundamental human right. So, in order to provide enough quality water to populations whatever the context, researchers are now further focusing on innovative procedures of easy and cheap exploitation allowing access to enough quality water at the user end. Therefore, one of the innovative techniques used in various area in science is three-dimensional (3D) printing. Thus for this study, a 3D printer, “Ultimaker 1”, initially designed for plastic printing has been tailored for the confection of ceramic filters. These filters can treat the water to be consumed at the user end. From this experience we can notice that this innovative concept, could very soon become a reliable alternative in the provision of enough and quality water in developing countries.