Alternative Sanitation and Strategic Directives for the Well Water Security in Cotonou (Benin) and Lomé(Togo)

In the coastal cities of West Africa, land use change, rapid population growth, bad sanitation systems and poor environmental governance degrade the quality of groundwater. This study aimed to assess alternative, acceptable, affordable sanitation disposal and practices for groundwater quality rehabilitation in the cities of Cotonou and Lomé. The study was based on the participatory transdisciplinary approach, field surveys, feedback from interactions with stakeholders, experiences of the practitioners and institutional consultations. This multi-stakeholder approach helped to appreciate ecological aspects of sanitation disposal and its implications on water quality improvement. SWOT model was used to analyze the relevance of assessed ecological system. Well water quality is deteriorated by traditional waste management disposal. Ecological sanitation systems are septic tanks on polyethylene, above-ground latrines and phytoremediation technique in the swamp areas. Collected wastes are used for composting and biogas production. Based on the optimist scenario at 2030 horizon, kind success factors of groundwater security are participation of citizens, existence of sanitation market, valorization of the waste by category, low-cost disposal adaptable to the individual, household and neighborhood’s scales. The strategic directions rely on funding and public policies for WASH, ecological sanitation disposal, cultural environment and good sanitation practices for emergence of new sanitation system to secure and sustain well water quality. But the social acceptability of ecological disposal is limited by the society’s multicultural heritage. These findings could help in decision-making concerning urban groundwater quality protection in the African coastal cities.

Effects of Urban Metabolism on the Well Water Quality in Cotonou (Benin) and Lomé(Togo)

Urban metabolism, a process of material, energy and water flows, consumption or transformation in the cities and outflows of wastes, has impacts on the shallow groundwater. This study addressed the relationship between the urban metabolic system and well water physicochemical and bacteriological quality in the coastal cities of Cotonou and Lomé. A participatory transdisciplinary approach, involving non-academics and academics stakeholders was used to analyse urban inflows and outflows related to groundwater quality. Standard methods were used to measure well water quality from 100 seasonal samples. Waste management revealed poor sanitation and hence a linear urban metabolism with no solid and liquid wastes and excreta recycling. This form of city metabolism reinforced by the seawater inflow is the main source of groundwater quality deterioration in Cotonou and Lomé. The principal water types Ca2+–Mg2+–Cl-– SO2-4 (48.21%), Na+–K+–Cl-–SO2-4 (65.9%) and the Gibbs diagram suggested water-rock interactions and dominance of cations exchange on the hydrogeological compositions, also seasonally controlled by saltwater intrusion or anthropogenic salinization. The water quality index on the range of 35.90 to 169.60 in Cotonou and 82.94 to 364.68 in Lomé indicated well water very poor quality to unsuitable for drinking. Moreover, the bacteriological quality was bad due to total coliforms (112 - 1812;1 - 1000 UFC/100 mL respectively in Cotonou and Lomé), Escherichia coli (40 - 780;1 - 112 UFC/100 mL), faecal enterococci/streptococcus (18 - 736;1 - 118 UFC/100 mL). The findings could help to sustain groundwater quality by controlling the pollution sources linked to urban metabolism.