Sanitation techniques that are low cost and non-conventional are the adequate solution for the treatment of wastewater for small communities in rural areas. This work presents the experience of the ONEP used in some small and medium sized communities. Also, within the framework of the sanitation programme, the ONEP carried out a series of studies for sanitation treatment plants for urban and rural centres in Morocco. Currently, the ONEP manages about twenty wastewater treatment plants in Morocco. The most widespread process is the lagoon system.