The National Office of Sanitation of Senegal (ONAS) is a public institution of an industrial and commercial nature in charge of the management of the sanitation sector. It was created by the law n ° 96-02 of February 22nd, 1996, and organized by the decree 96-667 of August 7th, 1996.

ONAS is responsible for:

- Planning and programming of investments
- Project management and project management, design and control of studies and works of wastewater and rainwater infrastructure;
- Operation and maintenance of wastewater and rainwater sanitation facilities;
- The development of autonomous sanitation;
- Recovery of by-products of wastewater treatment plants;
- All operations directly or indirectly related to its purpose, within the limits of urban and peri-urban areas