Kigali is a city built on grand planning ambitions, yet one of its most pressing development challenges remains largely hidden underground. For years, urban planners and residents have looked towards the proposed 92-kilometre centralised sewerage system, designed to channel the capital’s wastewater to a central treatment plant in Giti Cy’Inyoni. However, with recurring delays and contractual setbacks affecting the project, it may be time to reconsider whether a single, citywide sewerage network is the most practical solution for Kigali. There is a geographical reality we cannot ignore. Kigali is a city of hills and valleys, with steep slopes in some areas reaching 50 per cent. Moving wastewater across such terrain towards one central treatment facility presents considerable engineering and financial challenges. Pumping wastewater across multiple ridges, installing lift stations and maintaining extensive pipelines could make the system expensive to build and operate. If we are to achieve the sanitation ambitions set out in Vision 2050, Kigali should not have to wait for one massive infrastructure project to solve the entire city’s wastewater problem. Instead, we should consider a decentralised approach, establishing wastewater treatment systems at the cell level, designed around natural drainage patterns and supported by innovative public-private partnerships (PPPs). Using the cell (akagari) as the basic planning unit brings infrastructure development closer to the communities it serves. However, decentralisation must be guided by more than administrative boundaries. It must also respect the physical geography of the land. A cell may extend across a hill, with settlements on opposite sides draining into different valleys. Forcing both sides into one treatment network could recreate the same pumping challenges associated with a centralised system. The solution is to design networks around natural watersheds, allowing a single cell to have more than one treatment facility where its topography requires it. Locating compact, modern treatment facilities at suitable low points within these natural catchments allows wastewater to flow through gravity-fed collection networks. This reduces the need for expensive pumping infrastructure, lowers energy consumption and allows Kigali’s natural landscape to become an asset rather than an obstacle. The immediate question, of course, is how to finance hundreds of smaller treatment systems across the city. This is where well-structured PPPs could make a difference. Today, many Kigali households rely on septic tanks. Emptying them comes at a considerable cost—about Rwf200,000 for a vacuum truck service. As a result, some households avoid the expense altogether, allowing wastewater to seep into the surrounding soil rather than arranging proper emptying. This is not only a sanitation and environmental concern. In a city as hilly as Kigali, uncontrolled wastewater infiltration could also contribute to soil instability, particularly on steep slopes, increasing the risk of erosion and potentially landslides. We may therefore be allowing a sanitation problem to develop quietly into a wider environmental and public safety risk. Under a properly structured PPP arrangement, private-sector consortia could finance, construct and operate decentralised networks. The private sector would bring the investment, technical expertise and operational discipline required to maintain these facilities. The government would retain regulatory and oversight responsibilities, ensuring compliance with service standards and environmental safeguards while protecting affordability. The revenue model could build on existing utility arrangements. A dedicated sanitation tariff, collected through WASAC’s monthly water bills, could provide a predictable revenue stream for private operators. For connected households, this would replace the recurring cost of septic tank emptying with a more structured sanitation service. Nkwandi Andrew, a veteran entrepreneur with decades of experience in water treatment and environmental management, believes that Kigali’s gravity must be our asset, not our adversary. “By confining treatment infrastructure strictly within the natural hydrographic catchments of each cell, we eliminate the immense energy loads required for uphill pumping. This localised, engineering-first approach reduces upfront capital expenditure, making individual cell networks more attractive to private investors through tailored PPP frameworks,” he explains. His observation captures an important point. Infrastructure should be designed around the realities of the land, not simply around lines drawn on an administrative map. A decentralised, watershed-based sanitation model would also allow Kigali to implement infrastructure in phases. Individual cells could be assessed and prioritised according to population, sanitation needs, topography and available financing. Equally important, sanitation must be integrated into master planning, particularly in areas earmarked for future development and settlement. Wastewater networks, drainage and treatment facilities should be planned alongside roads and water supply, not introduced as an afterthought once communities have settled. Retrofitting such infrastructure into established neighbourhoods often comes at a much higher financial and social cost. The writer is an ideator and a strategist in development and alternative financing at Halisi Consulting Ltd.
