44 research outputs found

    Impact du déversement direct des eaux usées et de drainage dans la nappe libre de l'Oued Souf et son influence sur la qualité des eaux souterraines.

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    Ces vingt dernières années la région de l'Oued Souf souffre du phénomène de la remontée des eaux de la nappe libre, qui inonde les « ghouts » et les maisons, entrainant de graves problèmes sociaux, agriculturaux et environnementaux. Le réseau d'assainissement qui ne couvre qu'une partie de la ville d'El-Oued rend la situation plus dramatique. Jusqu'a la fin de l'année 2010 une zone, située au Nord-Est de la ville d'El-Oued, a été aménagée pour que les eaux de drainage (système pour rabattre la nappe) et les eaux usées soient déversées directement sans aucun traitement préalable. L'objectif de cette étude est de déterminer l'extension du déversement dans la nappe libre de l'Oued Souf, surtout des eaux usées, et d'évaluer les risques de pollution des eaux souterraines de la nappe libre, plus particulièrement dans la zone de rejet. Six campagnes de mesures hydrochimiques ont été faites : trois durant l'année 2007 (avril, juin et septembre), deux durant l'année 2010 Ganvier et avril) et une en mai 2012 âpres l'arrêt de rejet. L'analyse des échantillons et leur interprétation ont permis l'établissement d'une carte de l'indice de pollution organique. Cette dernière a montre que le terrain a un pouvoir autoépuratoir élève ce qui réduit considérablement les effets de la pollution d'origine organique. Cette tendance est confirmée par les valeurs de la dispersivité longitudinale αL faibles, déterminées au niveau de la zone de rejet. Pour ce qui est des teneurs de certains éléments majeurs naturels (Na+, Ca++, SO4-, Cl-...), celles-ci restent élevées et posent un sérieux problème d'aptitude de ces eaux à l'Irrigation.Mots clés: Nappe libre - Remonte des eaux - Eaux usées - Pollution organique - Oued Souf More than twenty years the region of Oued Soufis suffering from the rising of the water table in the unconfined aquifer, causing flooding of "ghouts" and damaging houses, which induces serious social, agricultural and environmental problems. The sewerage system that covers only a part of the city ofEl-Oued makes the situation more dramatic. Until the end of 2010, the drainage water and wastewater are discharged directly without any preliminary treatment in an area located north-eastern of El-Oued city. Nowadays a wastewater treatment plant was constructed and this area is not more used. The purpose of this study is to determine the extension of the contaminated area by discharged wastewater in the unconfined aquifer and to assess the risk of pollution of groundwater, particularly in the discharging zone. Three hydrochemical surveys were conducted in the discharging area and in its vicinity during 2007 (april, june and september), two during 2010 Ganuary and april) and one in may 2012. The interpretation of analysed samples shows that the pollution has a very short extension and the soil has an important self purifying role that reduces the effects of organic pollution that is shown in the established map of index of organic pollution. The low value of longitudinal dispersivity αL of the soil, evaluated in the discharging area, confirms this trend. We note that the content of some major natural elements such as (Na+, Ca++, SO4-, Cl-...) is high and the use of the groundwater is not advised for irrigation.Keywords: Unconfined aquifer- Rising water level - Wastewater- Organic pollution - Oued Sou

    Dynamique de la nappe et qualités physico-chimiques des eaux souterraines du lac Fetzara (Nord-Est algérien)

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    Le lac Fetzara est l'un des plus importants lacs de l'extrême Nord-Est Algérien, avec une superficie de 18600 ha. Il a été officiellement classe sur la liste des zones humides d'importance internationale, ce qui impose une protection de ce site. Cette étude a été menée afin d'étudier l'état actuel de la chimie des eaux souterraines et de déterminer l'origine de la salinité. Les résultats analytiques montrent la présence de trois facies chimiques : chlorure sodique, chlorure calcique et bicarbonate sodique. La conductivité électrique des eaux oscille entre 350 et 3500 μS/cm avec de fortes valeurs enregistrées dans les régions Nord-Est (Oued Zied) et au Sud-Est du lac (Cheurfa). L'étude statistique par l'analyse en composantes principales (ACP) montre que les chlorures et le sodium sont les principaux éléments responsables de la forte minéralisation des eaux. Cet excès de minéralisation serait lie éventuellement au lessivage des terrains traverses ou par l'infiltration des eaux de surface qui sont fortement influencées par la forte évaporation en période estivale et les échanges ioniques avec la matrice argileuse.Mots clés: Salinité - Minéralisation - Contamination - Piézométrie - Facies chimique -ACP. Fetzara lake is one of the most important lakes in the North-Eastern of Algeria; with an area of about 18600 ha, it was officially classified on the list of Wetlands of International Importance. This dictates the protection of this location. This study was conducted to examine the current state of groundwater chemistry and the origin of their salinity. The results obtained show a presence of three chemicals facies: sodium chloride, calcium chloride and sodium bicarbonate. The electrical conductivity of groundwater oscillates from 350 to 3500 μS I cm where high values are recorded in the North-East (Oued Zied) and the South-East of the lake (Cheurfa). Statistical study by principal component analysis (PCA) showed that chloride and sodium are the main elements responsible for the high mineralization of the water. This excess of mineralization is due to the leaching of subsurface formations and surface waters infiltration; these are strongly influenced by evaporation and ionic exchanges with clay matrix.Keywords: Salinity - Mineralization - Contamination - Piezometry - Chemical facies - PCA

    Extrapolation de spectre avec contraintes : La méthode des coefficients de réflexion subordonnés à un poids

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    Mechanism of phenol adsorption onto electro-activated carbon granules

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    The main purpose of this paper is to determine the mechanisms which govern the adsorption of the phenol onto electro-activated carbon granules. This new activation technique allowed an increase of the performance of the adsorbent. Two models were utilised to understand the improvement in the performance of electroactivated carbon granules. The first, a simple external resistance model based on film resistance, gave acceptable predictions, with an error of less than 15%, between the theoretical results and experimental data independent of the activation potential and phenol initial concentration. The second linear model, based on diffusion phenomena, was more representative in describing the experiment than the first model. It was observed that the electro-activation method did not change the mechanism which governs phenol adsorption onto granular carbon. Indeed, the same mathematical model based on diffusion phenomena made it possible to predict with a very low error (less than 5%) the experimental data obtained for the favourable activation potential, without activation potential and with an unfavourable activation potential. The electro-activation technique makes it possible to increase the number of active sites that improve the performance of the electro-activated granular carbon compared with conventional granular activated carbon

    A Test for Spectrum Flatness

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    We investigate a new tool for measuring whiteness. We first introduce a quantity which has suitable properties for constructing a test for randomness. We provide the exact asymptotic power of our test. Finally, we experimentally assess the power and usefulness of our test. Copyright 2007 The Author Journal compilation 2007 Blackwell Publishing Ltd.

    Economic study of groundwater defluoridation of the North African Sahara

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    The economic evaluation of defluoridation of Sahara groundwater is presented for three processes: electrodialysis, reverse osmosis and the electrochemical bipolar reactor (EBR). The economic study was accomplished for a drinking water unit production of 100 m3/h. One of the findings was that the costs per cubic metre of treated water obtained with different processes were not too costly for the states of the North African region. The results also indicated that the most efficient process uses the EBR, followed by the electrodialysis and reverse osmosis process. However, the water produced by the first process does not have the required quality for drinking water; therefore, it has to be utilised for agricultural purposes. On the other hand, the electrodialysis unit do produce quality drinking water and appears to be an interesting solution to the fluorisis disease. Reverse osmosis method technique provides higher quality of drinking water with a salinity not exceeding 0.1 gsalts/l
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