Simulating water quality of the N'Djili River using the WEAP model in the Democratic Republic of Congo

In the Democratic Republic of Congo, some of the key challenges that urban areas face are river pollution. The current study simulated the water supply and quality of the N'Djili sub-catchment using the WEAP system. The N'Djili subcatchment was selected for this study because it is a vital source of water supply to over 7 million residents of Kinshasa and faces significant pollution levels with increasing water demand. Results show that unmet demand will rise to 198 million cubic meters by 2035, which is 66% of the total water demand from 55% in 2024. On water quality, a WWTP with tertiary treatment (80% mercury removal efficiency) reduced the downstream mercury concentration by 59.88%. In contrast, primary treatment (basic sedimentation with 20% E. Coli removal) had a negligible impact on reducing E. Coli concentrations. Only tertiary treatment, through advanced filtration and chemical processes with 80% E. Coli removal efficiency, was able to substantially lower the pollutant concentration in the river at a minimum efficiency of 90%. The results obtained clearly show how much investment in infrastructure for advanced wastewater treatment is urgently needed to ensure integrated water management strategies that mitigate pollution and guarantee sustainable water supply for urban populations.