Élimination des oeufs de nématodes et des kystes de protozoaires des eaux usées domestiques par lagunage à microphytes en zone soudano-sahélienne

La station expérimentale pilote d'épuration des eaux usées par lagunage de l'École Inter-États d'Ingénieurs de l'Équipement Rural (EIER), Ouagadougou, Burkina Faso, reçoit les eaux usées des bâtiments administratifs et de l'internat des étudiants. Dans les eaux usées brutes, des oeufs d'helminthes (Ascaris lumbricoides, Ankylostoma duodenale), des kystes de protozoaires (Entamoeba coli, Entamoeba histolytica) et des larves d'Anguillule ont été mis en évidence.Avec un temps de séjour de 16,4 jours dans les bassins de lagunage (2 à 3 heures dans le décanteur, 3,4 jours dans le premier bassin, 13 jours dans le deuxième bassin), les kystes d'Entamoeba coli et d' Entamoeba histolytica sont éliminés respectivement à 94 et 96 %, les oeufs d'Ascaris lumbricoides à 100%, les oeufs d'Ankylostoma duodenale à 90 % et les larves d'Anguillule à 92 %. Quand on considère tous les parasites confondus, le décanteur a un rendement éliminatoire de 33 %, le premier bassin 62 % (malgré la forte charge appliquée), le deuxième bassin 78 %. Le rendement global obtenu pour l'ensemble des parasites est de 94 %.Si les évolutions des concentrations des parasites fluctuent dans le temps, il y a une différence très significative entre les concentrations obtenues en sortie du lagunage et celles des eaux usées brutes.On a constaté l'absence des oeufs d'Ascaris lumbricoides pendant toute la période de l'étude ; il en a été de même pour les oeufs d'Ankylostoma duodenale durant une période de 10 mois. Par conséquent, les eaux usées épurées rejetées répondent aux recommandations de l'OMS quant à leur réutilisation agricole.La mise en place des systèmes rustiques d'épuration des eaux usées dans les pays en voie de développement, surtout dans les zones où les ressources en eau sont limitées, pourrait contribuer sensiblement à la diminution des risques sanitaires liés aux pratiques courantes de réutilisation agricole des eaux usées en agriculture.Experimental waste stabilization ponds to purify domestic wastewater from the École Inter-États d'Ingénieurs de l'Équipement Rural (EIER) were built in Ouagadougou, Burkina Faso. The waste stabilization ponds system consists of a raising tank, a decanter, and two ponds in series. The first pond is 1.22 m deep with a surface area of 62 m2; the second pond is 1.07 m deep and covers an area of 340 m2. The inflow averaged 22 m3/d, giving a normal retention time of 3.4 days in pond number 1 and 13 days in pond number 2. The average daily BOD5 load was 1500 kg/ha/day for pond number 1 and 200 kg/ha/day for pond number 2.Different parasites were identified in the raw wastewater, such as cysts of Entamoeba coli and Entamoeba histolytica, eggs of Ascaris lumbricoides and Ankylostoma duodenale and larval stages of Anguillula . The quantitative estimation of cysts, eggs and larvae was obtained using a Mac Master cell after concentration by a formol-ether technique (RITCHIE, 1948). Of 24 samples of raw wastewater analyzed, all contained cysts of E. coli and E. histolytica and Anguillula larvae. Similarly, 100 % of final effluent samples (Fig. 2-B) contained cysts of E. coli and E. histolytica, but the concentrations were respectively 16 and 22 times lower than in raw wastewater. Six of the 24 samples (25 %) contained Anguillula larvae (Fig. 9), 17 % contained Ankylostoma duodenale eggs and no samples (0 %) contained Ascaris lumbricoides eggs (< 1 egg/L).This study were not carried out on Ouagadougou urban wastewater, due to the lack of a wastewater collection network, but the raw wastewater of the central market of Ouagadougou was analyzed for comparison because it represented a larger population than that in the EIER. In the raw wastewater of the central market, the concentration of parasites was high: Ascaris lumbricoides (110 eggs/L), Taenia saginata (53 eggs/L), Ankylostoma duodenale (39 eggs/L), Trichuris trichiura (19 eggs/L), Entamoeba coli (552 cysts/L), Entamoeba histolytica (479 cysts/L), Anguillula (62 larvae/L). The concentration of parasites identified in raw wastewater from EIER (Entamoeba coli (395 cysts/L), Entamoeba histolytica (269 cysts/L), Ascaris lumbricoides (4 eggs/L), Ankylostoma duodenale (9 eggs/L), Anguillula (26 larvae/L)) seemed consistent with the contamination level of the users of EIER stabilization ponds system. With a total retention time of 16.4 days in the stabilization ponds, removals of E. coli and E. histolytica cysts were respectively 94% and 96%. Ascaris lumbricoides and Ankylostoma duodenale eggs were 100 and 90% removed, respectively, and removal of Anguillula larvae was 92%. Grimason et al. (1995), suggest that cumulative retention time of up to 55.3 days at Eldoret, Kenya and 40 days at Meze, France were sufficient to remove between 99.1 % and 99.7 % of cysts of Giardia lamblia, respectively. Global efficiency of the system for all parasites was 94%. In the decanter, where retention time was 2-3 hours, the removal efficiency was 33%. With 3.4 days retention time, the first pond (anaerobic due to the high organic load applied) increases removal to 62%. The second pond (optional) afforded a 78% removal efficiency with a 13 days retention time.If the number of parasites fluctuated with time, the number observed in the effluent was significantly lower than those observed in the influent.The effluent of EIER waste stabilization ponds system was free of Ascaris lumbricoides eggs throughout the study period and free of Ankylostoma duodenale eggs during 10 months; the effluent thus satisfied the WHO recommendations for reuse in agriculture. Waste stabilization pond systems would seem to have a significant place in Sudan- Sahara area for removal of parasite ova and cysts, being economical and advantageous. They would also contribute to reduce sanitary risks associated with reuse of untreated wastewater in agriculture

Potential of the Coupled WRF/WRF-Hydro Modeling System for Flood Forecasting in the Ouémé River (West Africa)

Since the beginning of the 2000s, most of the West-African countries, particularly Benin, have experienced an increased frequency of extreme flood events. In this study, we focus on the case of the Ouémé river basin in Benin. To investigate flood events in this basin for early warning, the coupled atmosphere–hydrology model system WRF-Hydro is used, and analyzed for the period 2008–2010. Such a coupled model allows exploration of the contribution of atmospheric components into the flood event, and its ability to simulate and predict accurate streamflow. The potential of WRF-Hydro to correctly simulate streamflow in the Ouémé river basin is assessed by forcing the model with operational analysis datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF). Atmospheric and land surface processes are resolved at a spatial resolution of 5 km. The additional surface and subsurface water flow routing are computed at a resolution of 500 m. Key parameters of the hydrological module of WRF-Hydro are calibrated offline and tested online with the coupled WRF-Hydro. The uncertainty of atmospheric modeling on coupled results is assessed with the stochastic kinetic energy backscatter scheme (SKEBS). WRF-Hydro is able to simulate the discharge in the Ouémé river in offline and fully coupled modes with a Kling–Gupta efficiency (KGE) around 0.70 and 0.76, respectively. In the fully coupled mode, the model captures the flood event that occurred in 2010. A stochastic perturbation ensemble of ten members for three rain seasons shows that the coupled model performance in terms of KGE ranges from 0.14 to 0.79. Additionally, an assessment of the soil moisture has been developed. This ability to realistically reproduce observed discharge in the Ouémé river basin demonstrates the potential of the coupled WRF-Hydro modeling system for future flood forecasting applications

Safeguarding public health concerns, livelihoods and productivity in wastewater irrigated urban and periurban vegetable farming

The goal of the project was to develop integrated and user-oriented strategies to safeguard public health concerns without compromising livelihoods and land and water productivity in wastewater irrigated urban and peri-urban vegetable farming. In this project, assessment of land and water productivity in wastewater irrigated farming was done, levels of contamination on irrigation water and vegetables quantified at different levels along the food chain (farms, markets and consumer level) and appropriate lowcost risk reduction strategies identified and participatory testing done with stakeholders at farm and consumer levels. A large number of students were involved in the project, significantly building human capacit

Development in Astronomy and Space Science in Africa

The development of astronomy and space science in Africa has grown significantly over the past few years. These advancements make the United Nations Sustainable Development Goals more achievable, and open up the possibility of new beneficial collaborations.Comment: Paper published in Nature Astronomy. Figures 1 and 2 are included in the published version, that can be seen at https://rdcu.be/2oE

Introduction de l’assainissement écologique en Côte d’Ivoire

L’introduction de l’assainissement écologique (EcoSan) en milieu rural s’est fait avec succès. L’utilisation de l’urine comme fertilisant en culture d’igname est possible sur le plan technique agronomique et socio-anthropologique. Des ouvrages d’assainissement ont été installés en milieu communautaire de même que des parcelles expérimentales fertilisées à l’urine. La richesse de l’urine en azote et en potassium permet d’accroitre la productivité des sols pauvres. Les sols ainsi fertilisés permettent, en culture d’igname, d’obtenir un rendement largement supérieur à ce celui obtenu avec la culture traditionnelle lorsque la culture est placée en tête de rotation. Ces résultats sont d’autant plus encourageants que l’on se trouve à la deuxième répétition culturale sur les mêmes terres. La valorisation de l’urine en agriculture améliore le cadre de vie en éliminant les excréta avec la réduction des mixions sauvages dans et alentour du village. De plus, les populations manifestent une forte adhésion au projet avec l’adoption de la démarche et des ouvrages. Elles n’hésitent pas non plus dans leur grande majorité à consommer les produits de récoltes provenant de champs fertilisés à l’urine parce que la qualité organoleptique n’est pas affectée par ce fertilisant. La pratique culturale endogène pratiquée sur les dépotoirs familiaux ou lélougoun constitue le facteur dynamisant de l’adoption du concept EcoSan

Classification of large-scale environments that drive the formation of mesoscale convective systems over southern West Africa

Mesoscale convective systems (MCSs) are frequently observed over southern West Africa (SWA) throughout most of the year. These MCS events are the dominant rain-bearing systems, contributing over 50 % of annual rainfall over SWA. However, it has not yet been identified what variations in typical large-scale environments of the seasonal cycle of the West African monsoon may favour MCS occurrence in this region. Here, nine distinct synoptic states are identified and are further associated with being a synoptic-circulation type of either a dry, transition, or monsoon season using self-organizing maps (SOMs) with inputs from reanalysis data. We identified a pronounced annual cycle of MCS numbers with frequency peaks in April and October that can be associated with the start of rainfall during the major rainy season and the maximum rainfall for the minor rainy season across SWA, respectively. Comparing daily MCS frequencies, MCSs are most likely to develop during transition conditions featuring a northward-displaced moisture anomaly (2.8 MCSs per day), which can be linked to strengthened low-level westerlies. Considering that these transition conditions occur predominantly during the pre- and post-monsoon period, these patterns may in some cases be representative of monsoon onset conditions or a delayed monsoon retreat. On the other hand, under monsoon conditions, we observe weakened low-level south-westerlies during MCS days, which reduce moisture content over the Sahel but introduce more moisture over the coast. Finally, we find a majority of MCS-day synoptic states exhibiting positive zonal wind shear anomalies. Seasons with the strongest zonal wind shear anomalies are associated with the strongest low-level temperature anomalies to the north of SWA, highlighting that a warmer Sahel can promote MCS-favourable conditions in SWA. Overall, the SOM-identified synoptic states converge towards high-moisture and high-shear conditions on MCS days in SWA, where the frequency at which these conditions occur depends on the synoptic state.</p

Comparative Study of the Sensitivity of Different Diagnostic Methods for the Laboratory Diagnosis of Buruli Ulcer Disease

Background. Several diagnostic laboratory methods are available for case confirmation of Buruli ulcer disease. This study assessed the sensitivity of various diagnostic tests in relation to clinical presentation of the disease, type of diagnostic specimen, and treatment history. Methods. Swab samples, 3-mm punch biopsy tissue specimens, and surgically excised tissue specimens from 384 individuals with suspected Buruli ulcer disease were obtained at 9 different study sites in Ghana and were evaluated with dry reagent-based polymerase chain reaction (PCR), microscopic examination, culture, and histopathological analysis. The study subjects presented with nonulcerative and ulcerative lesions and were divided into 3 treatment groups: (1) previously untreated patients scheduled for antimycobacterial treatment, (2) patients treated with surgery alone, and (3) patients treated with surgery in combination with previous antimycobacterial treatment. Results. Of 384 suspected cases of Buruli ulcer disease, 268 were confirmed by at least 1 positive test result. The overall sensitivity of PCR (85%) was significantly higher than that of microscopic examination (57%) and culture (51%). After data were stratified by treatment group, type of lesion, and diagnostic specimen type, analysis revealed that PCR of 3-mm punch biopsy tissue specimens (obtained from previously untreated nonulcerative lesions) and of swab samples (obtained from previously untreated ulcers) had the highest diagnostic sensitivity (94% and 90%, respectively). Although duration of the disease did not significantly influence the sensitivity of any test, previous antimycobacterial treatment was significantly associated with decreased sensitivity of PCR and culture. Conclusions. Across all subgroups, PCR had the highest sensitivity. PCR assessment of 3-mm punch biopsy tissue specimens proved to be the best diagnostic tool for nonulcerative lesions, and PCR assessment of swab samples was the best diagnostic tool for ulcerative lesions. For monitoring of antimycobacterial treatment success within controlled trials, however, only culture is appropriat

Projected future daily characteristics of African precipitation based on global (CMIP5, CMIP6) and regional (CORDEX, CORDEX-CORE) climate models

We provide an assessment of future daily characteristics of African precipitation by explicitly comparing the results of large ensembles of global (CMIP5, CMIP6) and regional (CORDEX, CORE) climate models, specifically highlighting the similarities and inconsistencies between them. Results for seasonal mean precipitation are not always consistent amongst ensembles: in particular, global models tend to project a wetter future compared to regional models, especially over the Eastern Sahel, Central and East Africa. However, results for other precipitation characteristics are more consistent. In general, all ensembles project an increase in maximum precipitation intensity during the wet season over all regions and emission scenarios (except the West Sahel for CORE) and a decrease in precipitation frequency (under the Representative Concentration Pathways RCP8.5) especially over the West Sahel, the Atlas region, southern central Africa, East Africa and southern Africa. Depending on the season, the length of dry spells is projected to increase consistently by all ensembles and for most (if not all) models over southern Africa, the Ethiopian highlands and the Atlas region. Discrepancies exist between global and regional models on the projected change in precipitation characteristics over specific regions and seasons. For instance, over the Eastern Sahel in July–August most global models show an increase in precipitation frequency but regional models project a robust decrease. Global and regional models also project an opposite sign in the change of the length of dry spells. CORE results show a marked drying over the regions affected by the West Africa monsoon throughout the year, accompanied by a decrease in mean precipitation intensity between May and July that is not present in the other ensembles. This enhanced drying may be related to specific physical mechanisms that are better resolved by the higher resolution models and highlights the importance of a process-based evaluation of the mechanisms controlling precipitation over the region

The MeerKAT Absorption Line Survey (MALS) data release I: Stokes I image catalogs at 1-1.4 GHz

The MeerKAT Absorption Line Survey (MALS) has observed 391 telescope pointings at L-band (900 - 1670 MHz) at $\delta\lesssim$ $+20\deg$. We present radio continuum images and a catalog of 495,325 (240,321) radio sources detected at a signal-to-noise ratio (SNR) $>$5 over an area of 2289 deg$^2$ (1132 deg$^2$) at 1006 MHz (1381 MHz). Every MALS pointing contains a central bright radio source ($S_{1\,\mathrm{GHz}} \gtrsim 0.2$ Jy). The median spatial resolution is $12^{\prime\prime}$ ($8^{\prime\prime}$). The median rms noise away from the pointing center is 25 $\mu$Jy beam$^{-1}$ (22 $\mu$Jy beam$^{-1}$) and is within $\sim$ 15% of the achievable theoretical sensitivity. The flux density scale ratio and astrometric accuracy deduced from multiply observed sources in MALS are less than 1% (8% scatter) and $1^{\prime\prime}$, respectively. Through comparisons with NVSS and FIRST at 1.4 GHz, we establish the catalog's accuracy in the flux density scale and astrometry to be better than 6% (15% scatter) and $0.8^{\prime\prime}$, respectively. The median flux density offset is higher (9%) for an alternate beam model based on holographic measurements. The MALS radio source counts at 1.4 GHz are in agreement with literature. We estimate spectral indices ($\alpha$) of a subset of 125,621 sources (SNR$>$8), confirm the flattening of spectral indices with decreasing flux density and identify 140 ultra steep-spectrum ($\alpha<-1.3$) sources as prospective high-$z$ radio galaxies ($z>2$). We have identified 1308 variable and 122 transient radio sources comprising primarily of AGN that demonstrate long-term (26 years) variability in their observed flux densities. The MALS catalogs and images are publicly available at https://mals.iucaa.in.Comment: 64 pages, 25 figures, accepted for publication in the ApJS (full version of the paper with complete tables is available at DR1 release notes

Histopathologic Features of Mycobacterium ulcerans Infection

Because of the emergence of Buruli ulcer disease, the World Health Organization launched a Global Buruli Ulcer Initiative in 1998. This indolent skin infection is caused by Mycobacterium ulcerans. During a study of risk factors for the disease in Ghana, adequate excisional skin-biopsy specimens were obtained from 124 clinically suspicious lesions. Buruli ulcer disease was diagnosed in 78 lesions since acid-fast bacilli (AFB) were found by histopathologic examination. Lesions with other diagnoses included filariasis (3 cases), zygomycosis (2 cases), ulcerative squamous cell carcinomas (2 cases), keratin cyst (1 case), and lymph node (1 case). Thirty-seven specimens that did not show AFB were considered suspected Buruli ulcer disease cases. Necrosis of subcutaneous tissues and dermal collagen were found more frequently in AFB-positive specimens compared with specimens from suspected case-patients (p<0.001). Defining histologic criteria for a diagnosis of Buruli ulcer disease is of clinical and public health importance since it would allow earlier treatment, leading to less deforming sequelae