Fractionnement et mobilité des métaux lourds dans un sol en amont des eaux usées de tanneries

La migration et la spéciation de Cr, de Cu et de Pb sont étudiées sur le sol d'une colonne alimentée par les eaux usées de tanneries. La localisation des métaux est évaluée à l'aide du schéma d'extractions sélectives préconisé par Legret et al. (1988). Les résultats ont montré que l'horizon superficiel renferme des teneurs en métaux très élevées. Parmi les métaux étudiés, le Cr s'avère retenu essentiellement dans la phase résiduelle mais il se présente aussi sous des formes plus mobiles. Le Cu est principalement associé avec la phase résiduelle et organique. Le Pb est lié aux phases acido-soluble et réductible. De ce fait, l'épandage des eaux usées de tanneries, sans aucun traitement préalable, peut être une source de contamination des sols et des eaux souterraines, notamment pour le Cr.In Morocco, the town of Marrakesh, as in other areas of the country, is subject to multiple daily aggressions generated by industrial pollution, in particular from tanneries. The tannery waste water is discharged directly into the aquatic and terrestrial ecosystems without any preliminary processing. In order to evaluate the danger that can be generated by tannery effluents in the receiving ecosystems, and to study the ecotoxicological and environmental impact resulting from that chemical treatment of these effluents, we determined, before and after treatment, the inhibitory effect of the two most polluted effluents originating from manufactured leather: liming-deliming and chromium tanning.The purpose of our investigation was thus to evaluate the acute toxicity of the chromium tanning and epilage-coat waste waters before and after chemical treatment. The invertebrate Daphnia pulex was used for the toxicity test and the toxicity due to these industrial waste waters was evaluated by regression analysis. The processing carried out on the chromium tanning waste water consisted of precipitation with sodium carbonate at different pH values. The treatment of liming-deliming wastewaters consisted of an elimination and recovery of the sulphide compounds without carrying out their degradation.The chromium level was determined by atomic absorption spectrophotometry with graphite furnace atomization. The results of the toxicity test showed that the investigated chromium tanning and liming-deliming effluents presented were toxic, with respective IC50-24h values of 0.15 and 3.36 (expressed as dilution ratios). This toxicity could be explained by high levels of chromium, sulphides and organic matter in these waste waters. It is however difficult to correlate the IC50 values obtained with those of the physical-chemical parameters. The tested effluents are very complex matrices. On the other hand, we noticed a notable difference between these two effluents. The mineral tanning effluent is contaminated with chromium and organic matter, whereas the second is especially rich in organic matter and sulphide.The total chromium concentration corresponding to the IC50-24h value of the raw chromium tanning effluent is lower than that which would be expected on the basis on the known toxicity of K2Cr2O7, showing the toxicity of raw chromium waste waters is due not only to chromium, but also to other chemicals used during the manufacturing process of leather. After processing by chemical precipitation, the IC50-24h values increased from 0.15 to 26.6 and from 3.36 to 11.1 respectively, for the chromium tanning and the epilage-coat effluents. Consequently, these treated sewages can be classified as low toxicity wastes. The comparison of the results is very difficult considering that the test conditions and the physicochemical and heavy metal characteristics of the effluents vary enormously over time, without forgetting the physicochemical composition of the experimental solution used by standard OECD (fresh water) and the standard ISO (synthetic water). From where necessity to vary tests for determining well the degree of an effluent toxicity which the effects appear differently at various levels trophic.The diminution observed in the toxicity of the effluents is linked to a reduction of suspended matter (95 %), COD (55 %), Cr (90 %) and sulphides (50 %). Hence, this treatment presents at least two advantages. The first is environmental as just mentioned. The second is economic since chromium can be recycled for reuse in leather tanning. The results suggest that the recovered chromium is similar to commercial tanning chromium. These results also show that the fixing of chromium does not depend on the nature of the treated skin. In fact, a technical and economic analysis showed that proposed treatment can be economically beneficial (3112,5 $ per 1000 tons of skins)

Treatment and reutilization of effluents: one Mediterranean project

The problematic of effluent treatment from olive oil industry as been the subject of an European Commission funded project (INCO-MED programme): “Mediterranean Usage of Biotechnological Treated effluent Water”. The potential that effluent offers to increase the availability of water, in mediterranean regions, was the final goal of the project, co-ordinated by INETI with partners from EU and MPC. In the project different systems for the treatment of this effluent had been studied: reactors systems (Intensive type) based on the jet-loop principle (JACTO) and an anaerobic UASB hybrid type reactor technology; lagoons (extensive type) for municipal wastewater treatment were also applied. The aerobic JACTO system demonstrated high unit capacity for biological conversion and operation at different loadings, allowing the removal of the pollutant organic load and the toxicity associated with this effluent. The use of this type of reactor for pre-treatment of OOWW prior to disposal on a lagoon system was tested at FSS (Morocco). Use of fungi as a pre-treatment was tested by UNITUS (Italy), EBC (Turkey) and CBS (Tunisia). In this way the effluent could be “improved” as demonstrated in the case of anaerobic digestion and biogas production (CBS). Effluent improvement and enrichment with phosphate was also tested by UNITUS. Analytical monitoring methodologies were developed at IA (Spain) and treated effluents were tested for a number of agricultural applications in different countries. The different alternatives studied will be analysed and compared taking account of technological and socio-economical criteria in relation with the project objectives

MEDLEM database, a data collection on large Elasmobranchs in the Mediterranean and Black seas

The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains more than 3,000 records (with more than 4,000 individuals) of large elasmobranch species from 21 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The principal species included in the archive are the devil ray (1,868 individuals), the basking shark (935 individuals), the blue shark (622 individuals), and the great white shark (342 individuals). In the last decades, other species such as the thresher shark (187 individuals), the shortfin mako (180 individuals), and the spiny butterfly ray (138) were reported with increasing frequency. This was possibly due to increased public awareness on the conservation status of sharks, and the consequent development of new monitoring programs. MEDLEM does not have homogeneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the northern sectors and the absence of some species in our database does not imply their actual absence in these regions. However,the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected species, the overall area coverage, and which species are involved as bycatch by different fishing gears.S

Conference highlights of the 15th international conference on human retrovirology: HTLV and related retroviruses, 4-8 june 2011, Leuven, Gembloux, Belgium

The June 2011 15th International Conference on Human Retrovirology: HTLV and Related Viruses marks approximately 30 years since the discovery of HTLV-1. As anticipated, a large number of abstracts were submitted and presented by scientists, new and old to the field of retrovirology, from all five continents. The aim of this review is to distribute the scientific highlights of the presentations as analysed and represented by experts in specific fields of epidemiology, clinical research, immunology, animal models, molecular and cellular biology, and virology

Effets des métaux lourds - Cu, Hg, Cd - sur les larves de trois espèces de moustiques (Diptera : Culicidae)

Les effets de trois métaux lourds (Cu, Hg, Cd) sur le développement d'Anopheles hispaniola, vecteur potentiel du paludisme, de Culex pipiens et Culex hortensis ont été étudiés dans l'oued N'fis près de la station Agadir Tachraft, dans les bassins expérimentaux de traitement des eaux usées de Marrakech (Maroc) et dans un bassin d'élevage des grenouilles. Les effets varient selon l'espèce, en fonction du développement et selon la nature et la dose du métal. A. hispaniola au stade L4 se montre le plus sensible aux trois métaux Cu, Hg, Cd. La CL50 (24h) est respectivement de 3,78, 1,52 et 4,81 mg.L-1, plus faible que celle de C. hortensis (5,02 , 3,1 et 9,91 mg.L-1) et de C. pipiens (5,91, 4,43 et 17,48 mg.L-1). Par contre, la sensibilité au Cd ne diffère pas significativement chez A. hispaniola et C. hortensis au stade L2 selon le test de Newman - Keuls. Cette étude montre qu'A. hispaniola qui a un cycle de vie relativement court et qui est facile à élever au laboratoire, présente une sensibilité 2 fois plus élevée pour le Hg, 3,4 fois plus élevée pour le Cd et 8,6 fois plus importante pour le Cu que Aedes aegypti. Cette dernière est proposée comme espèce-test pour les mêmes propriétés pour étudier les effets biologiques des métaux lourds sur les insectes aquatiques

Évaluation de la toxicité des eaux usées industrielles de tanneries: Impact du traitement chimique

The purpose of our investigation was the acute toxicity evaluation of the chromium tanning and liming-deliming wastewaters before and after chemical treatment. The invertebrate Daphnia pulex was used for toxicity test. The toxicity due to these industrial wastewaters was revealed by the equations of the regression lines. The results of the toxicity test showed that the investigated chromium tanning and liming-deliming presented higher toxicity with respective ICSO 24hr values of 0.15 and 3.36. This toxicity could be explained by higher levels of heavy metals (Cr, Cu and Pb), sulphides and organic matter in these sewages. After processing by chemical precipitation, ICSO 24hr increased from 0.15 to 26.58 and from 3.36 to 11.1 respectively for chromium tanning and the epilage-coat. Consequently, these processed sewages can be classified as little toxic rejects. This diminution of the toxicity is linked to dejection percentages of MES (95%), DCO (55%), Cr (90%) and sulphides (50%).Le monde industriel est de plus en plus confronté au problème du contrôle des émissions des substances toxiques dans l'environnement, particulièrement sous forme d'effluent liquide (Forstner et Wittmann, 1983). La complexité et la difficulté du problème résultent de la diversité des sources de rejets, de l'importance quantitative de ces rejets et de leur composition très variée (Crine, 1993). Au Maroc, à l'instar d'autres régions du pays, la ville de Marrakech connaît de multiples agressions quotidiennes engendrées par la pollution industrielle, en particulier celles des tanneries. Les eaux usées de la tannerie sont rejetées directement dans les milieux récepteurs (cas de l'Oued Issil) sans aucun traitement préalable. Ce qui pourrait être à l'origine de la dégradation de la qualité du sol et de la contamination des eaux de la nappe phréatique de la région. Afin de mettre en évidence le danger qui peut être causé par les effluents de cette industrie dans le milieu récepteur, nous nous sommes attachés à déterminer, avant et après traitement, le pouvoir inhibiteur des deux effluents les plus pollués du synoptique de fabrication du cuir à savoir l'épilage-pelanage et le tannage au chrome