OFFICE NATIONAL DE L'ASSAINISSEMENT DU SENEGAL (ONAS) is a public institution responsible for managing the sanitation sector in Senegal. Established by law in 1996, ONAS is tasked with various responsibilities, including investment planning, project management, infrastructure design and control, operation and maintenance of wastewater and stormwater facilities, development of autonomous sanitation systems, and utilization of by-products from treatment plants. With a vision to improve the sanitary, environmental, and socio-economic conditions of the population, ONAS is actively involved in ongoing projects such as the sanitation project in Cité Soleil and its surroundings, the wastewater treatment project in Joal-Fadiouth, the drainage project in Colobane, Rebeuss, and Yoff, and the sanitation project in other cities.

These initiatives aim to significantly enhance living and health conditions, reduce floods, and promote sustainable development in Senegal. Driven by core values and guided by legislative texts, ONAS works in collaboration with partners, conducts studies and insights, and keeps the public informed through articles, videos, and publications. To ensure efficient service, ONAS has a dedicated customer service department for sewer connection requests, complaint handling, and tracking of applications.

For further information, the public can contact ONAS via the provided phone number or email address