Environmental Flows Assessment Based on the Coupling of Water Level and Salinity Requirements for Maintaining Biodiversity: A Case Study from the Ouémé delta in West Africa.

The present study carried out on the Ouémé delta in West Africa, addresses the implementation of the BBM approach for the determination e-flows in a context of high data limitation. It also highlights the potential challenges for the implementation of the recommended e-flows in West Africa countries. To do this, we first established the current ecological status of the delta based on data collection, measurements and scientists' observations. Then, we formulated ecological objectives for e-flows based on the environmental management vision for the delta. And finally, we determined the water requirements for the sustainability of the biodiversity and ecosystem services using a simple 2D hydrodynamic model. The results indicate that 100 and 50% of the average natural flows are required respectively in low-water and high-water periods (3.4 billion m3 per year) to maintain the Ouémé Delta in its current environmental management class. This recommendation for e-flows allocation is in direct competition with the water requirements for the economic development of the delta, which is estimated to be over 3.0 billion m3 per year in the Master Plan for Water Development and Management. While it is clear that the establishment of e-flows recommendations must be accompanied by measures to limit the degradation of ecological habitats, it is even more clear that the economic development remained the main concern of policymakers. The integration of environmental flows into water resources management policies in developing countries requires linking water needs for economic development with water needs for the ecological sustainability of rivers and their associated ecosystems.

Spatio-temporal dynamics of nutrients at the water-sediment interface: case of the Nokoue lagoon in Southern Benin.

Lake Nokoué, a major component of the hydrographic system of the Ouémé delta, is the largest lagoon-estuarine ecosystem in Benin. Recent studies have shown that benthic processes would actively participate in the maintenance of the eutrophication and biogeochemical cycle of this ecosystem. In order to understand the implication of the bottom on the quality of the waters of the lake, a monthly follow-up of ten (10) parameters of quality of the waters of the bottom was undertaken from July 2020 to December 2021 on a network of nineteen (19) stations distributed on the whole lake. Univariate and multivariate analysis techniques were used to assess the spatial and temporal dynamics of these waters. The Kruskal-Wallis test, PCA, correlation analysis and discriminant analysis all showed a very marked influence of the hydrological regime on the concentration of nutrients compared to the influence of anthropogenic activities around the lake and an influence of climatic conditions on internal processes. Indeed, water inflows from the Ouémé watershed are the main contributors of phosphorus in the lake while benthic processes are the most important contributors of nitrogen. Cluster analysis defined three significantly different areas in Lake Nokoué: the channel, the centre of the lake and the river mouth. A single station in each cluster could be used for a spatial assessment of water quality over the entire lake.

Growth kinetics and purifying performance of A. Platensis in stirring-free culture based on brewery effluent's supernatant.

Due to costs of setting up and operating electrical stirring systems to keep algae in suspension and exposed to light, cultivation of monospecific algae is poorly expanded in developing countries. However, some algal species, such as Arthrospira platensis, are equipped with gaseous vesicles that allow them to stay afloat and increase their exposure to light. In this study, we investigated in an unstirred outdoor environment, its growth kinetic and purifying performance in a brewery effluent-based media. Batch cultures were carried out in three experimental treatments and evolution of physicochemical and growth parameters were monitored. Then its contribution to depollution was determined. Results show that optimal conditions for producing A. platensis include the culture tank transparency, the effluent dilution (i.e. 10%), and the culture media amendment with sodium bicarbonate and sodium nitrate. The average productivity recorded reached 0.55 g DW·L-1·d-1 during the exponential growth phase, while preserving culture from contamination. COD and total nitrogen concentrations were reduced to 32.5 and 64.91%. Such results open up prospects for low-cost production of certain algae, in transparent and relatively high barrels, thus breaking the classic barriers related to shallow basin depth and mechanical agitation traditionally considered as critical to the success of algal production.

Physicochemical assessment of urban wastewater of Cotonou (Benin).

The present study aims to fill the data gap analysis in urban wastewaters characteristics in Benin and its statistical analysis. Physicochemical parameters such as pH, electrical conductivity (EC), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP) and UV Absorbance at 254 nm, were determined on domestic (greywater and blackwater) and industrial (hospital, pharmaceutical and commercial laundry) wastewater in Cotonou city. Analysis of variance showed a strong significant difference in the physico-chemistry of the various effluents. The pharmaceutical wastewater has the highest concentration of organic pollution (COD = 5,912 ± 1,026 mg/L, Abs.UV254 = 2.667 ± 0.327 cm-1). The organic load of blackwater is mainly in particulate and biodegradable form. Besides, the correlation study showed the limits of pH and EC as an indicator of organic load. Furthermore, the choice of COD or BOD5 as the main design parameter would be limited to blackwater treatment. Abs.UV254 was found to be the parameter having a strong relationship with other parameters of all effluents except blackwater. It then takes priority over COD for the treatment of greywater and industrial wastewater. For future wastewater treatment plant design, we recommend to consider Abs.UV254 as an important parameter.

Assessment of the Presence of Resistance Genes Detected from the Environment and Selected Food Products in Benin.

Gram-negative bacilli can spread from the environment and through food products. This study aimed to characterize ESBL production and virulence genes from multidrug-resistant Gram-negative bacilli isolated from specimen collected from the environment, kitchen, and food products. A total of 130 samples were collected at local markets in seven different communities in Benin (Abomey-Calavi, Ouidah, Bohicon, Abomey, Parakou, Djougou, and Grand-Popo). Samples were cultured on McConkey and ChromID™ ESBL agar plates. The isolates were identified by the API 20E gallery. An antibiotic susceptibility test was carried out, and the detection of ESBL production and virulence-associated genes was carried out by Polymerase Chain Reaction (PCR). The data collected was coded and analyzed using GraphPad prism 7 software and Excel. The software R was used to calculate the correlation coefficient between the results of the detection of ESBL+ on agar and by the effect of the double synergy. The results showed that sixty-three (63) bacterial strains were isolated from the 130 samples, of which the dominant species was Chryseomonas luteola (10/63). The kitchen samples were the most contaminated with 36.50%. More than 40% of the isolates were resistant to at least three different classes of antibiotics. Also, blaSHV gene was detected in 33.33% (21/63) of the isolates and in all isolates of Pseudomonas aeruginosa (5/5%). 11.11% (7/63) of isolates were virulent with dominance of the fimH gene, especially with Escherichia coli (83.33%). The kitchen samples showed a high prevalence of ESBL-producing strains with fimH gene. This raises the problem of non-compliance with hygiene rules in community cooking and food handling.

Optimization process of organic matter removal from wastewater by using Eichhornia crassipes.

This study aimed to determine the optimal conditions for organic matter removal from wastewater by Eichhornia crassipes (E.C). As a matter of fact, a complete factorial design was used to determine the effect of residence time (X1), plant density (X2) and initial chemical oxygen demand (COD) concentration (X3) on the phytoremediation process. The process's performance was measured on COD (Y1), NH4+ (Y2) and PO43- (Y3), with the results indicating a reduction of 8.59-81.71% of COD (Y1); 22.53-95.81% of NH4+ (Y2) and 0.54-99.35% of PO43- (Y3). Then, the first-order models obtained for COD, NH4+ and PO43- removal were validated using different statistical approaches such as statistical and experimental validation. Moreover, multi-response optimization was carried out through different scenarios. On the whole, the results obtained indicated that two serial ponds are required for an optimum organic matter removal by Eichhornia crassipes. Indeed, for the first pond, a residence time of 15 days is needed with a plant density of 60 ft/m2 and an initial concentration of about 944 mg/L. The second was the same residence time as the first with similar plant density of 60 ft/m2 and an initial load 192 mg/L (> 200 mg/L). Optimal organic matter removal from wastewater using Eichhornia crassipes requires two ponds arranged in chain.