Review of the Tunisian experience in treated wastewater reuse from the beginning of the 1960s, with a focus on results and the legal and regulatory measures taken to encourage the process
At the beginning of the 1980s, a discussion was initiated in Tunisia on the feasibility of large-scale wastewater reuse in agriculture, and the possible implementation within the same decade of a national reuse policy.
The use of treated wastewater in Tunisia is an important component of the national water saving strategy for irrigation, and the practice also helps to save good-quality waters for other purposes. Using reclaimed water to irrigate some specific crops including cereals, fodder crops and fruit trees is authorised by law under specific conditions. In addition, treated wastewater has been used for non-agricultural purposes, such as irrigating green areas and golf courses, since the beginning of the 1970’s with the development of tourism in Tunisia. The authorities also consider groundwater recharge as an additional option.
The current situation of the use of treated wastewater in irrigated areas
With the success of the experiments carried out by the Ministry of Agriculture using treated wastewater to protect 600 hectares of citrus fruits in the La Soukra area (Governorate of Ariana) from the beginning of the 1960s, and due to the increasing volumes of available treated wastewater while the country is facing water scarcity, the public authorities embarked on the implementation of large-scale projects to exploit treated wastewater by creation new irrigated perimeters and protecting other irrigated areas suffering from water shortages.
The currently volume of reused treated wastewater is estimated at 57 mm3 , of which 39 mm3 is reused in irrigation (22 mm3 for agriculture, 10 mm3 watering golf courses, and 7 mm3 for green spaces), while 18 mm3 is disposed into wetlands and rivers.
(See table)for Wastewater treatment and reuse data in 2014.
The total size of areas irrigated with treated wastewater is around 8,100 hectares, spread over 27 irrigated perimeters that receive water from 26 wastewater treatment plants, including the areas of Cebala-Borj Touil (Governorate of Ariana) (3200 hectares) and Mornag (Governorate of Ben Arous) (1,087 hectares), representing nearly 57 percent of the total area equipped for irrigation. It should be noted that some of these irrigated areas suffer from dilapidated equipment and require immediate rehabilitation and expansion due to the availability of additional reclaimed water volumes.
(See table) for Percentage of treated wastewater reused.
The authorities are currently developing an innovative project in the perimeter of Mornag, funded by KFW, that includes a groundwater recharge of about 5 mm3 through a tertiary treatment process.
It should be noted that in terms of cost recovery, reclaimed water tariffs paid by the farmers do not cover the total operating and maintenance costs of wastewater treatment plants, and the state continues to subsidise the projects. On the other hand, reclaimed water is provided free of charge to golf courses in order to reduce the pressure on conventional water resources.
A comprehensive and updated legal framework
The reuse of treated wastewater for irrigation has been enabled by the existence of a comprehensive and updated legal framework comprising legal provisions, regulations and standards to encourage the use of reclaimed waters in agriculture.
Worth mentioning in this context is Article 106 of the Tunisian Water Code, passed in 1975: “The use of wastewater for agricultural purposes is authorised only after appropriate treatment of these waters in a wastewater treatment plant and by decision of the Ministry of Agriculture, taken after approval by the Ministry of Public Health.”
At the beginning of the 1990s, a whole legal arsenal was established through a series of decrees and decisions. With this legislation, the government: set the conditions of use of treated wastewater for agricultural purposes; approved the Tunisian standard NT 106-003 on the use of treated wastewater for agricultural purposes; established the list of crops that could be irrigated by treated wastewater; and, finally, articles 86 and 87 of Law 2001-116 of November 26, 2001 on Amending and Supplementing the Water Code considered the reuse of treated wastewater for production and service purposes as a water resource development that has a public utility character.
Tunisia’s standards comply with the relevant FAO and WHO recommendations and permit the irrigation of a wide range of crops (e.g. industrial crops, cereal crops, fodder crops, fruit trees, fodder shrubs, forest trees, and floral plants for drying or industrial purposes).
Concerning the institutional aspects, different stakeholders intervene in the process of reclaimed water reuse. The National Office of Sanitation is in charge of producing treated wastewater and operating the treatment plants; different public authorities are in charge of sanitary control, especially the Ministry of Health and the Environmental Protection Agency; and the Regional Agricultural Development Offices (MAWRF) provide reclaimed waters to farmers, while installing and maintaining the water system—from the plants themselves to the irrigated perimeters.
More than 30 years after the creation of the first irrigated perimeters using reclaimed water, one of the challenges encountered was the high salinity recorded in some treatment plants, due mainly to the combined collection of domestic and industrial wastewaters. The majority of treatment plants in Tunisia are limited to a primary or secondary treatment stage (only five plants provide tertiary treatment). Furthermore, some plants are now showing limited performance due to overload, faulty operation and poor maintenance.
It is now clear that there is a need to rehabilitate and upgrade the infrastructure in order to increase the quality and efficiency of treated wastewater resources. Both users and the authorities view tertiary treatment as the best option going forward. Some studies have shown that a majority of farmers are willing to pay more for better-quality water.
- Reused treated wastewater volume is estimated at 57 mm3, representing around 30 percent of the overall treated wastewater volume
- Existence of a public policy dedicated to wastewater reuse
- An adapted and updated legal framework
- Availability of public resources for investment to develop and improve wastewater treatment and reuse
- Providing treated wastewater to users at a low price or for free
- Quantity of treated wastewater reused
- Percentage of reused wastewater, compared to the overall volume of treated wastewater
Repeatability requires the existence of wastewater treatment functional infrastructures, as well as a demand for and acceptance from farmers to use reclaimed waters.
- ACWUA, “Wastewater Reuse in Arab Countries: Comparative Compilation of Information and Reference List”, March 2010
- Akissa Bahri, “Water reuse in Tunisia: stakes and prospects”, National Institute for Research on Agricultural Engineering, Water and Forestry, BP 10, Ariana 2080, Tunisia
- Hella Ben Brahim-Nejia, Alberto Ruiz-Villaverde, Francisco González-Gómez. “Decision aid supports for evaluating agricultural water reuse practices in Tunisia: The Cebala perimeter”
- General Directorate of Water Resources; Ministry of Agriculture, Water Resources and Fisheries