• To the north of Tunis, the adduction of waste water by underground route and their discharge into the sea create a disposal system that respects the environment and depollutes the beaches.
• Of all the samples taken at sea, 96% contain a content of bacteria considered safe by the health authorities and 97% have a concentration of detergents considered harmless.
• Thanks to a greater volume of treated wastewater, devoted to agriculture and urban spaces, Tunisia and other countries deprived of water resources can adapt to water shortages exacerbated by climate change.
According to an article recently published on its website, the World Bank indicates that in the north of Tunis, the beach of Raoued, which had been prohibited for swimming for years, was able to reopen in 2020 following the green light from the Tunisian health authorities. , with significant benefits for the local economy, and fishermen satisfied with the changes observed in the quality of the marine environment. What looks like a miracle is, in fact, the work of engineers and scientists, as well as careful sanitation work. The batch of seawater samples taken in Raoued in 2020 were found to be 96% safe for bacteria content, and 97% safe for detergent concentration. Treated wastewater is now evacuated by underground pipes to an underwater outlet (technical term designating a conduit under the sea) 6 km long, discharging effluent 20 m below the surface. At this depth and at this distance, wastewater, from human activities and treated, as well as other liquid wastes, disperse in the Gulf of Tunis, diluting the pollution generated by modern domestic life and agricultural practices.
Adapt to water scarcity
Purifying gray water for reuse on agricultural land also increases the country’s ability to adapt to water scarcity, which is intensifying due to climate change. Investing in a new, environmentally risk-free treated wastewater disposal system preserves the country’s beautiful Mediterranean coastline and benefits the people who live, work and play there.
Tunisia is one of the most water-poor countries in the world. In 2017, the water available per capita was 367 cubic meters (m3) for a country that is home to just under 12 million people, while the regional average is 526 m3 and the world average and 5,700 m3. A resource that is all the more solicited by urban development, the increase in demand and the need to irrigate to support employment in rural areas.
An old and poorly maintained sewer system
Pollution from agricultural drainage and municipal effluents threatened the country’s coastal and marine ecosystems. When the Gulf of Tunis was identified as “the biggest pollution black spot”, the government made it a priority. The National Sanitation Office (Onas) and the ministries have drawn up a program to tackle the problem. Thirty years old and poorly maintained, the sewer system might no longer cope with the volume of waste produced. Its channels evacuated waste water, outcropping in the open air, from the Choutrana wastewater treatment plant, south of Raoued, towards Wadi Khalij, which discharged it at its mouth on the beach. The population complained regarding the smells and the dangers to health. The waste diminished the attractiveness of the area for tourism and other development activities. Even if treated, the quality of the wastewater was too poor for agriculture.
Wastewater can be safely reused
These improvements were made possible through a $60.6 million project that closed in 2021. Supported by the World Bank and co-financed by the Global Environment Facility (GEF), the Tunis-Nord sanitation project has supported the construction of underground pipes, the outlet and a wastewater retention basin.
The funds have made it possible to create two parallel and sealed pipes that carry wastewater from the Choutrana station to a large sludge settling basin located nearby, in El Hissiene, where solid waste is separated from effluent. By burying the pipes, pollution of the surroundings by waste water and its contamination downstream is avoided.
The basin’s flow can be regulated for irrigation purposes, providing Borj Touil’s approximately 500 farmers with several million cubic meters of good quality recycled water. Faced with rapid urbanization and land use change in the region, Onas has reached an agreement with urban developers so that part of the wastewater irrigates the green spaces of the new district of Tunis Bay City. To convince the general public that recycled wastewater poses no danger to plant cultivation, plots belonging to three Borj Touil operators have been irrigated with treated wastewater. Other demonstration plots were created near a wastewater treatment plant on the coast, in Sidi Amor, northwest of Borj Touil. The lands of Sidi Amor are equipped with filtration systems, water cisterns, a pumping station, an irrigation system, a laboratory and a demonstration center. Thanks to the Sidi Amor pilot project, the various stakeholders have strengthened their coordination; in addition, its quality control laboratory is open to agricultural students. The water distribution company and Onas now have a modernized billing system, which simplifies the collection of bills. Upgraded, Onas’ computer system now includes real-time data analysis, which allows remote management of water flows and efficiency gains.
