Urban sanitation technologies : the challenges of reaching the urban poor

In the densest urban areas of the world, it is impossible to treat and manage excreta and greywater on site. Instead it must be transported out of the city and be safely disposed of. The problem of delivering sustainable sanitation services in these conditions is one of scale, to deal with the excreta and greywater from millions of people. Particular care must be taken when extrapolating results from pilot projects of a few hundred households to whole cities, due to the institutional complexities that arise and the sheer volume of sewage. For 2,000 years, various societies have used a piped system with water as the transport medium in dense urban areas. The problem then as now has been an inability to treat of the sewage before discharge into the environment. This is demonstrated by the fact that only 8% of the sewage in the developing world is currently treated. Although the poor generate less greywater than the rich, mainly due to lack of access to water, this is not a state of affairs that is desirable or likely to persist. Any solution will eventually have to deal with vastly increased volumes of greywater. Given the institutional complexities surrounding dense urban slums it is unrealistic to expect that sustainable sanitation services can be provided. The objective is to minimise risks as far as possible so as to maximise the health benefits to the residents. This paper discusses the various technical options and makes recommendations for how to achieve this.

(authors abstract)