Conducted jointly by UL and UAC, this research explores the variability of wastewater pollution between Cotonou and Grand-Nancy.
Key Takeaway: Conducted jointly by UL and UAC, this research explores the variability of wastewater pollution between Cotonou and Grand-Nancy.
Nelly Chrystelle Houéfa Atinkpahoun, researcher at LRGP (Université de Lorraine).
Thesis defended in 2018 at the doctoral school RP2E - Ecole Doctorale Sciences et Ingénierie des Ressources, Procédés, Produits, Environnement.
This research was conducted as part of a Franco-Beninese joint supervision (cotutelle), ensuring it is simultaneously grounded in local field conditions and international academic standards.
Referenced in the ABES/STAR network, this thesis meets the rigor standards of French higher education.
Context and Problem Statement
Wastewater pollution is a major problem for both public health and the environment, significantly affecting water resources in Benin and France. Urban wastewater, when untreated or poorly treated, has harmful consequences for aquatic ecosystems and population health. The research conducted by Nelly Chrystelle Houéfa Atinkpahoun aims to examine the variability of urban wastewater pollution in two distinct geographic contexts: Cotonou, Benin, and Grand-Nancy, France. This study aims to provide empirical data and explore the relationships between wastewater pollution, socio-economic and cultural contexts, and sanitation infrastructure.
Methodology
The methodological approach adopted in this research is based on rigorous sampling of urban wastewater over several months. Samples were taken at hourly intervals over 24 hours, both at the inlet of wastewater treatment plants (WWTPs) in Cotonou and in the municipality of Maxéville, in Grand-Nancy. In situ flow rate measurements were carried out, complemented by laboratory analyses to quantify the pollutants present. In parallel, a virtual wastewater generation model was developed to simulate wastewater variability, incorporating data on the lifestyle of the collection catchment areas.
Samples taken in Cotonou were also analyzed in the collection network to assess pollution at different stages of the sanitation system. The data collected made it possible to identify trends and variations in wastewater quality, as well as to assess the effectiveness of the sanitation infrastructure in place.
Key Findings
The results of this study reveal significant differences in wastewater pollution between Cotonou and Grand-Nancy. The analyses show that Cotonou's wastewater has a higher pollution level than that of Grand-Nancy, despite a number of inhabitants connected to the Cotonou WWTP (approximately 1,200 population equivalent) that is markedly lower than that of Grand-Nancy (approximately 275,000 population equivalent). This situation raises concerns about the effectiveness of the sanitation systems installed in Cotonou.
Inflow rates at the Grand-Nancy WWTP show marked daily variability, with three notable peaks at 10 a.m., 2 p.m., and 9 p.m. on weekdays. In contrast, a decrease of 2% (Saturdays) and 9% (Sundays) in these flow rates is observed, accompanied by a 2-hour shift in the appearance of the first peak on weekends. For Cotonou, although pollution is more pronounced, the electrical conductivity of the wastewater remains higher in Grand-Nancy, which shows a higher excess of europium.
The data analysis also revealed that daily variations in pollution parameters are very pronounced in the collection catchments, with the exception of pH, which shows similarity between the two contexts. The virtual wastewater generation model developed demonstrated its ability to simulate variations in flow and pollution, consistent with experimental observations. This model is currently being extended to include heavy metals, which could enrich the understanding of wastewater pollution.
Discussion and Outlook
The results obtained underscore the need to reassess sanitation infrastructure in Benin, highlighting the disparities observed compared to France. Managing wastewater across varied geographic and cultural contexts requires a tailored approach that takes local specificities into account. Optimizing sanitation systems could be facilitated by adopting virtual wastewater generation models, which make it possible to better anticipate variations in flow and pollution and to develop more effective control strategies.
Integrating heavy metal data into future iterations of the model could also contribute to a better understanding of the risks associated with wastewater pollution. Future research could explore the impacts of wastewater pollution on public health, assessing the potential consequences for local communities and identifying sustainable solutions.
Establishing partnerships between academic institutions and local authorities is essential for implementing the proposed solutions. This could help ensure that the public policies developed are based on solid data and tailored to the realities of each context. The results of this research thus provide a framework for concrete actions aimed at reducing wastewater pollution and improving sanitation infrastructure, thereby contributing to public health and the protection of water resources in Benin and France.
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Sources and Access
Nelly Chrystelle Houéfa Atinkpahoun. Relations entre la variabilité de la pollution des eaux usées urbaines et les contextes géographiques, socio-économiques et culturels au Bénin et en France. Génie des procédés. Université de Lorraine; Université d'Abomey-Calavi (Bénin), 2018. Français. ⟨NNT : 2018LORR0092⟩. ⟨tel-01883653⟩