Performances épuratoires d’une filière de trois bassins en série de lagunage à microphytes sous climat sahélien : cas de la station de traitement des eaux usées de 21E (groupe EIER-ETSHER)

Des études portant sur l’épuration des eaux usées domestiques ont été menées sur une filière de trois bassins en série de lagunage à microphytes à la station expérimentale de l’Institut International d’Ingénierie de l’Eau et de l’Environnement (2IE). Cette filière comporte : un bassin anaérobie (BA), un bassin facultatif (BF) et un bassin de maturation (BM). Des mesures d’indicateurs de qualité ont été effectuées pendant dix mois sur des échantillons prélevés suivant une fréquence bihebdomadaire pour certains et hebdomadaire pour d’autres. Les rendements épuratoires moyens atteignent 66 % pour les MES, 81 % pour la DCO et 87 % pour la DBO5. Le résiduel de MES de l’effluent traité répond, dans 76 % des mesures, aux normes de rejet recommandées par la directive de l’Union Européenne (< 150 mg L‑1). L’élimination du phosphore est faible et instable avec un rendement moyen de 17,2 % pour le phosphore total et 19,2 % pour les ortho-phosphates. La réduction de la pollution azotée atteint en moyenne 76 % en NTK et 38,4 % en azote ammoniacal. De manière globale, les teneurs résiduelles en azote et en phosphore restent assez élevées par rapport à la limite tolérable pour un rejet d’effluent dans un écosystème sensible à l’eutrophisation. L’abattement de la pollution bactérienne est important allant jusqu’à 4,9 ulog pour les coliformes fécaux; mais la teneur résiduelle moyenne (5,4 × 103 unités formant des colonies (ufc)/100 mL) reste tout de même supérieure à la directive OMS (≤ 1 000 ufc/100 mL) pour une réutilisation non restrictive en irrigation. Concernant la charge parasitaire, les études ont montré que la filière assure une élimination totale (100 %) des oeufs d’helminthes et des kystes de protozoaires.Waste stabilization ponds (WSP) are considered to be one of the main methods for municipal wastewater because of their advantages over other methods (conventional treatment) relating to treatment effectiveness, system flexibility and simplicity, and cost (Arthur, 1983; Mara, 1976; Mara and Pearson, 1986; Silva, 1982). Moreover, it has long been accepted that tropical climates provide an ideal environment for the natural treatment of sewage in ponds.Since 1989, the 2IE (International Institute for water and Environmental Engineering) wastewater treatment plant in the city of Ouagadougou (Burkina Faso) has been investigating the performance of pilot-scale systems in order to establish regional design parameters and removal efficiencies. Several experiments have been carried out on pond series with different configurations and operational characteristics aiming to improve the design, operation and performance of waste stabilization ponds in Sahelian climate conditions. The purpose of the present study was to evaluate the efficiency of a new series of three stabilization ponds.The series was composed by one anaerobic pond (AP), one facultative pond (FP) followed by one maturation pond (MP). The characteristics (depth, area, volume and hydraulic retention time) were respectively 2.6 m, 69.7 m2, 181.2 m3, and three days for the AP, 1.4 m, 415.3 m2 and 581.4 m3 and 9.5 days for the FP, 0.9 m, 336.9 m2, 303.2 m3 and 5.5 days for the MP. The ponds were constructed with concrete to ensure water tightness. Field studies indicated a wide fluctuation in the biochemical oxygen demand (BOD5) loading applied. The average volumetric organic load ranged from 104 to 225 g BOD5 m‑3j‑1 with an average load of 105.2 g BOD5 m‑3j‑1 for the AP, the average surface BOD5 load on the FP was 117 kg BOD5/ha/j.The series was monitored for ten months from October 2004 to July 2005. The assessment involved an intensive program of sampling and analysis. The composite samples (obtained daily by mixing equal volumes of grab samples collected) were taken from the influent and effluent of each pond twice per week. Global physico-chemical parameters (T°, pH, Dissolved Oxygen (DO), conductivity ) were measured in situ. Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD) were analyzed according to standard methods. Suspended solids (SS) were determined gravimetrically after filtration through Whatman GF/C glass fiber filters and drying at 105°C. Total Kjeldahl Nitrogen (TKN) and ammonia nitrogen (AN) were analyzed according to AFNOR methods. Nitrate nitrogen (NT), total phosphorus (TP) and orthophosphate (OP) were determined by HACH methods. Faecal coliforms (FC) were counted by layer technique using the chromocult coliform agar, helminth eggs and protozoan cysts were determined by sodium acetate formalin (SAF) adapted method.Results showed during the study period average removal rates of 66% for SS, 87% for filtered BOD5, and 81% for COD. For COD and BOD5, removal performances were relatively constant over the study period with ranges of (60,9% ‑ 96,1%) and (65,6 ‑ 6,8%), respectively. In 83.8% of filtered BOD5 measures (n = 68) on the final effluent, BOD5 removal efficiency were higher than 80%. However, for SS removal efficiency, it indicated a wide fluctuation. The same fluctuation was observed on SS concentration on the final effluent, with a variation coefficient of 34.3%. Effluent SS concentrations from the series varied between a minimum of 4 mg/L and a maximum of 326 mg/L with average of 110 mg/L. The higher values of SS were observed during the warm period (March-April) corresponding to the abundance of algal proliferation in facultative and maturation ponds. In this period, effluent SS concentrations were higher than the influent ones, leading to negative efficiencies for these ponds. Despite this disturbance due to algal proliferation, the final effluent quality met the European Union (EU) quality requirements, i.e suspended solids concentration < 150 mg per litre. This standard was achieved in 76% of SS measures (n = 75) during the study period.The capability of the system for phosphorus removal was weak and variable, with average removals around 17% and 19% respectively for TP and OP removals. The mean residual concentrations of TP and OP in the final effluent were respectively 12.5 mg/L and 4.6 mg/L, values higher than the maximum concentration of 0.1 mg/L PT for the discharge of effluent in water sensitive to eutrophication (Ayers and Westcot,1985; WHO, 1989). Average TKN removal was 76%. Global efficiencies of the three-pond series for nutrients (nitrogen and phosphorus) reduction were weak and the effluent concentration of these nutrients did not satisfy the quality recommended to discharge in water sensitive to eutrophication. However, they could be useful as fertilizer for reuse for irrigation.With a total hydraulic retention time (HRT) of 18 days, the removal of faecal coliforms (fc) reached a maximum removal of 4.9 log units. The residuals fc concentration in the final effluent ranged between 1 × 103 fc/100 mL to 3.4 × 105 fc/100 mL, with an average of 5.4 × 103 fc/100 mL. According to the WHO recommendation (1989) for reuse in agriculture, the effluent did not meet the WHO guideline (≤ 1000 fc per 100 mL) for unrestricted irrigation. In spite of an average HRT of 18 days, the results showed that the fc removal for the WSP system (AP + FP + MP) in a Sahelian climate did not meet the WHO standard for faecal coliform reduction. The performance results of this study were, however, slightly better than those obtained by Maderaet al. (2002) on a similar study in wet tropical climate (in Colombia). Concerning helminths eggs and protozoan cysts, different parasites were identified in the raw wastewater such as: eggs of ankylostoms ranging from 0 to 4 eggs/litre, ascaris eggs 0 ‑ 10 eggs/litre, trichuris eggs 0 ‑ 1 egg/litre, and larval stages of anguillula 0 ‑ 5 eggs/litre. Two protozoan cysts were identified in the raw wastewater: Entamoeba coli ranged 6 ‑ 272 cysts/litre and entamoeba histolitica 2 ‑ 55 cysts/litre. Concerning helminths eggs and protozoan cysts removals, they were all completely (100%) removed in the final effluent of the series after 18 days HRT. Helminth eggs and protozoan cysts removal was very good. Most were removed in the anaerobic and facultative ponds, and the WHO guideline values for crop irrigation (both restricted and unrestricted) of < 1 egg/litre were achieved after the two first ponds (AP + FP). Regarding sanitary concerns during the ten‑month study period, the final effluent of the three ponds series correspond to B category effluent (WHO,1989) which could be reused for irrigation of cereal crops, industrial crops, fodder crops, pasture, and trees

Light concentration solar cell: temperature proper and dynamic effects on electrical parameters determined by using J-V and P-V characteristics

The solar cell is assumed to be under light concentration (C=50 Suns) which leads us to take into consideration the electric field induced by electrons concentration gradient. We also take into consideration temperature influence on electron and hole diffusion parameters, on carrier generation rate, on carrier intrinsic concentration and on silicon energy gap. It emerges from results analysis that increase in temperature leads to decrease of open-circuit voltage and the photovoltaic parameters at the maximum power point (MPP) such as electric power, photo-voltage and photocurrent with however a slight increase of short-circuit photocurrent density. It also appears that temperature has a double effect on electrical parameters. The temperature dynamic effect which is characterized by parameters variations linked to operating point displacement caused by temperature variations. And the temperature proper effect which is characterized by parameters variation with temperature at a given operating point. Thus, the combination of these two effects represents temperature effective effect

Damage mechanisms of pathogenic bacteria in drinking water during chlorine and solar disinfection

This study aimed at elucidating the inactivation mechanisms of pathogenic bacteria in drinking water during chlorine and solar disinfection using a simple plating method. The well-known bacterial model Escherichia coli was used as pathogenic bacteria for the experiments. The damage mechanisms of E. coli were evaluated by simple plating method on selective, less selective and non-selective media. Results showed that, injured E. coli were detected at different levels during chlorine and solar disinfection. The use of selective media during water quality control showed effectively the destruction of E. coli during solar disinfection while the removal of E. coli during chlorine disinfection was not ensured. The damage of cell components and/or metabolic functions showed that there is a primary and mainly damage of E. coli during chorine and solar disinfection. Chlorination firstly and mainly damaged membrane cell followed by that of enzymatic functions and nucleic acid; while solar disinfection damaged mainly nucleic acid. The use of simple plating method in water quality control is limited by the choice of plating media depending on the disinfectant used. The understanding of the damage mechanisms of pathogenic bacteria cells during disinfection helps improve drinking water quality control and develops more effective disinfection strategies.© 2016 International Formulae Group. All rights reserved.Keywords: Drinking water, pathogenic bacteria, E. coli, damage mechanisms, chlorine disinfection, solar disinfectio

Feeding behaviour of potential vectors of West Nile virus in Senegal

Background: West Nile virus (WNV) is a widespread pathogen maintained in an enzootic cycle between mosquitoes and birds with occasional spill-over into dead-end hosts such as horses and humans. Migratory birds are believed to play an important role in its dissemination from and to the Palaearctic area, as well as its local dispersion between wintering sites. The Djoudj Park, located in Senegal, is a major wintering site for birds migrating from Europe during the study period (Sept. 2008-Jan. 2009). In this work, we studied the seasonal feeding behaviour dynamics of the potential WNV mosquito vectors at the border of the Djoudj Park, using a reference trapping method (CDC light CO(2)-baited traps) and two host-specific methods (horse- and pigeon-baited traps). Blood meals of engorged females were analysed to determine their origin. Results: Results indicated that Culex tritaeniorhynchus and Cx. neavei may play a key role in the WNV transmission dynamics, the latter being the best candidate bridging-vector species between mammals and birds. Moreover, the attractiveness of pigeon-and horse-baited traps for Cx. neavei and Cx. tritaeniorhynchus varied with time. Finally, Cx. tritaeniorhynchus was only active when the night temperature was above 20 degrees C, whereas Cx. neavei was active throughout the observation period. Conclusions: Cx. neavei and Cx. tritaeniorhynchus are the main candidate vectors for the transmission of WNV in the area. The changes in host attractiveness might be related to variable densities of the migratory birds during the trapping period. We discuss the importance of these results on the risk of WNV transmission in horses and humans

Etude Comparative Des Produits Issus De La Transformation En Filature Des Fibres De Trois Nouvelles Variétés De Cotonnier

Résumé - Au Mali, comme ailleurs en Afrique, la sélection variétale est à la base du succès de la culture cotonnière. Le coton du Mali est presqu’entièrement exporté ; les fibres issues des variétés cultivées doivent répondre aux exigences du marché en termes de caractéristiques technologiques des fibres, facteurs clés du fonctionnement de la filature. Cette étude comparative a été réalisée sur trois nouvelles variétés de cotonniers A, B et C, issues d’un point d'expérimentation. L'objectif de l'étude est d’identifier les variétés ayant les meilleures performances variétales et industrielles pour la vulgarisation en production commerciale par les sociétés cotonnières. 1 échantillon représentatif de 100g de coton fibre, 20 échantillons de 5 m de rubans de carde, d’étirage et de 10 m de mèches, 30 échantillons de 100 m de fil et 40 échantillons de 500 mm de fil ont été respectivement prélevés par balle de chaque variété et à différentes étapes du processus de transformation par variété. Ces échantillons ont été testés sur des appareils de mesure dans les conditions requises au laboratoire de métrologie textile du CERFITEX, Ségou - Mali.L’analyse de variance (ANOVA) des données relatives aux fibres, rubans, mèches et fils et la comparaison de leurs principales caractéristiques de qualité à celle de la production mondiale avec l’application des USTER STATISTICS 2018 ont montré que les variétés de cotonnier A et B sont nettement meilleures que celle de C. Les performances variétales et industrielles de A et B, meilleures que celles de C sont recommandées à la vulgarisation Mots clés : Coton, caractéristiques technologiques, qualité, fibres, fils. [Comparative Study Of The Products Resulting From The Transformation Into Spinning Of The Fibers Of Three New Varieties Of Cotton]Abstract - In Mali, as elsewhere in Africa, varietal selection is the basis of the success of cotton growing. Cotton from Mali is almost entirely exported; fibers from cultivated varieties must meet market requirements in terms of the technological characteristics of fibers, key factors in the operation of the spinning mill. This comparative study was carried out on three new varieties of cotton A, B and C, from an experimental point. The objective of the study is to identify the varieties with the best varietal and industrial performance for popularization in commercial production by cotton companies. 1 representative sample of 100g of cotton fiber, 20 samples of 5m of carding and drawing slivers and 10m of rovings, 30 samples of 100m of yarn and 40 samples of 500mm of yarn were respectively taken per bale of each variety and at different stages of the transformation process by variety. These samples were tested on measuring devices under the required conditions at the CERFITEX textile metrology laboratory, Ségou - Mali.The analysis of variance (ANOVA) of fiber, sliver, roving and yarn data and the comparison of their main quality characteristics to that of world production with the application of USTER STATISTICS 2018 showed that cotton varieties A and B are clearly better than those of C. The varietal and industrial performances of A and B, better than that of C are recommended for popularisation Keywords : Cotton, technological characteristics, quality, fibres, yarns

Analysis of Preventive Interventions for Malaria: Exploring Partial and Complete Protection and Total and Primary Intervention Effects.

Event dependence, the phenomenon in which future risk depends on past disease history, is not commonly accounted for in the statistical models used by malaria researchers. However, recently developed methods for the analysis of repeated events allow this to be done, while also accounting for heterogeneity in risk and nonsusceptible subgroups. Accounting for event dependence allows separation of the primary effect of an intervention from its total effect, which is composed of its primary effect on risk of disease and its secondary effect mediated by event dependence. To illustrate these methods and show the insights they can provide, we have reanalyzed 2 trials of seasonal malaria chemoprevention (SMC) in Boussé, Burkina Faso, and Kati, Mali, in 2008-2009, as well as a trial of intermittent preventive treatment of malaria in infants in Navrongo, Ghana, in 2000-2004. SMC completely protects a large fraction of recipients, while intermittent preventive treatment in infants provides modest partial protection, consistent with the rationale of these 2 different chemopreventive approaches. SMC has a primary effect that is substantially greater than the total effect previously estimated by trials, with the lower total effect mediated by negative event dependence. These methods contribute to an understanding of the mechanisms of protection from these interventions and could improve understanding of other tools to control malaria, including vaccines

Clinical Variation of Plasmodium falciparum eba-175

The association between P. falciparum eba-175, ama-1, and msp-3 polymorphism in the pathogenicity of malaria disease was investigated. We therefore compared the prevalence of different alleles between symptomatic and asymptomatic malarial children under five years of age living in Burkina Faso. Blood filter papers were collected during the 2008 malaria transmission season from 228 symptomatic and 199 asymptomatic children under five years of age. All patients were living in the rural area of Saponé at about 50 km from Ouagadougou, the capital city of Burkina Faso. P. falciparum parasite DNA was extracted using QIAGEN kits and the alleles diversity was assessed by a nested PCR. PCR products were then digested by restriction enzymes based on already described polymorphic regions of the eba-175, ama-1, and msp-3 genes. The individual alleles eba-175_FCR3 and msp-3_K1 frequencies were statistically higher (p<0.0001) in the asymptomatic group compared to the symptomatic ones. No statistically significant difference was noted in the prevalence of ama-1-3D7, ama-1-K1, and ama-1-HB3 genotypes between the two groups (p>0.05). The comparative analysis of P. falciparum genotypes indicated that the polymorphism in eba-175 and msp-3 genotypes varied between asymptomatic and symptomatic clinical groups and may contribute to the pathogenesis of malaria

Antibodies to malaria vaccine candidates are associated with chloroquine or sulphadoxine/pyrimethamine treatment efficacy in children in an endemic area of Burkina Faso

<p>Abstract</p> <p>Background</p> <p>Patient immune status is thought to affect the efficacy of anti-malarial chemotherapy. This is a subject of some importance, since evidence of immunity-related interactions may influence our use of chemotherapy in populations with drug resistance, as well as assessment of the value of suboptimal vaccines. The study aim was to investigate relationship between antibodies and anti-malarial drug treatment outcomes.</p> <p>Methods</p> <p>Some 248 children aged 0.5 and 15 years were recruited prior to the high malaria transmission season. Venous blood (5 ml) was obtained from each child to measure antibody levels to selected malaria antigens, using ELISA. Blood smears were also performed to assess drug efficacy and malaria infection prevalence. Children were actively followed up to record clinical malaria cases.</p> <p>Results</p> <p>IgG levels to MSP3 were always higher in the successfully treated group than in the group with treatment failure. The same observation was made for GLURP but the reverse observation was noticed for MSP1-19. Cytophilic and non-cytophilic antibodies were significantly associated with protection against all three antigens, except for IgG4 to MSP1-19 and GLURP.</p> <p>Conclusion</p> <p>Acquired anti-malarial antibodies may play an important role in the efficacy of anti-malarial drugs in younger children more susceptible to the disease.</p