Non-conventional sewerage services

Non-conventional sewerage services.
When to choose this option, how to implement this solution.

A study financed by the Syndicat Interdépartemental pour l’Assainissement de l’Agglomération Parisienne (SIAAP), the Agence de l’eau Seine Normandie and the French Agency for Development (AFD)


There are two main types of sanitation system that can be used to meet household demand for sanitation services in developing countries: on-site sanitation, whereby individual facilities are built for each household; and conventional sewerage, such as that used in many towns and cities. However, in some areas, installing these types of sanitation is not always possible and alternative sewerage systems have had to be developed. These systems, called ‘non-conventional sewerage’ in this guide (and which include both simplified and settled sewers), overcome some of the constraints associated with conventional sewerage (smaller diameter pipes, which are laid at shallower depths, and simplified connections, etc.), which results in a lower investment cost. Non-conventional sewerage services also differ from conventional sewerage by virtue of their scope (covering a residential area rather than the whole town), allocation of responsibilities and the management method used.

Consequently, non-conventional sewerage is an option that is only suitable for specific types of urban area. Before embarking on a non-conventional sewerage project, it is important to be fully aware of the complexities of managing a non-conventional sewerage service and ensure that all the necessary conditions for launching such a service are in place.

The present study aimed to identify strengths and weaknesses of non-conventional sewerage and appraise its suitability. The study was based on a 5 case studies of non-conventional sewerage services around the world.


Outputs of the study: