Critical factors for the rehabilitation of Hann Bay (Senegal, West Africa): Solutions for sustainable development

The advanced degradation of Hann Bay (Dakar, Senegal) has reached highly elevated levels, with serious environmental, health, and social consequences. Thus, this study focused on the determinants for rehabilitating Hann Bay and proposed solutions for sustainable development. The target area is currently home to 500,000 inhabitants and hundreds of industrial units, with virtually no suitable wastewater treatment systems. Socio-economic surveys and three rounds of effluent sampling were carried out between 2020 and 2022 at eleven sites in Hann-Bel Air, Dalifort Foirail, Thiaroye sur mer, Sicap Mbao, and Mbao. The study showed increased physicochemical, biological, and bacterial pollution of the heavily contaminated wastewater along the bay. The analytical results of the samples collected for the three series show that almost all sampling points exceed the limit value for TSS (50mg/l) and COD (200mg/l). This indicates that physicochemical and organic pollution are still present in the bay, causing fish to escape into the open sea. BOD measurements are also above the standard (N05-061; 80 mg/l) for series 1 and 2, showing an alteration in bay conditions. Analysis of the microbiological quality of the water in terms of oils and fats showed values well above the current standard (NS 05-061, 20-50 mg/l), which explains the frequent fish kills at the Hann marinas, Hann pêcheurs, and Cité ISRA sites. The same situation was observed in samples of fecal coliforms (CFU/100ml), helminth eggs (eggs/L), nitrogen, phosphorus, zinc, and lead at values outside the norm.

Through socio-economic surveys of the populations and workers in the industrial units, the recommended solutions focus on protection and prevention measures, enforcement of regulations, communication and awareness-raising, equipment acquisition, and monitoring and surveillance to rehabilitate the bay.