The prevalence of improved sanitation among higher-income groups suggests that the necessary technologies are already supplied in the local market but that affordability remains an issue. There may be a need to work further on the development of lower-cost technologies or to consider the possibility of capital subsidies.
But on-site sanitation also has its limits. As urban population grows, water consumption also increases, creating the challenge of handling large volumes of wastewater. Also, with population densities rising in urban areas, the availability of land now constrains the use of latrines (particularly the simpler types) that require rotation of sites.
Sooner or later, Africa’s burgeoning cities will need to develop more extensive sewerage networks; however, conventional waterborne sewerage, at a per capita cost of $400, is far beyond the reach of all but the most affluent neighborhoods, and the public subsidies that would be required to support such sewerage networks in poorer areas are equally unaffordable.
The cost of sewer networks will have to be reduced through technological innovation. One lower-cost alternative developed in Latin America is condominial sewerage systems, which promise cost savings of up to 65 percent. Senegal—one of the most successful African countries at expanding high-end on-site sanitation (see figure)—has piloted condominial sewerage in the periurban areas of the capital, Dakar. By 2009, the Dakar system was to furnish 60,000 households (270,000 people) with on-site sanitation and to support 160 condominial schemes serving 130,000.
Senegal’s successful experience in expanding use of improved forms of sanitation