El Hajeb Perimeter

Time period :


Implementing Institution/ Organization:

Monastir Governorate in central-eastern Tunisia

Funded by :

ONAS Sfax/ CRDA Sfax and GDA


1) promoting the use of recycled water from wastewater treatment plants at the national level.
2) rehabilitation and increasing the capacity of wastewater treatment plants and improving the quality of the recycled water.
3) mitigation of environmental and health impacts of the treated wastewater discharges into the natural environment

Methodology (approach)

1) Analysis of documentation on the perimeter and the Sfax Sud WWTP 2019 studies on the rehabilitation and extension project of the El Hajeb Perimeter (feasibility study, detailed design study, execution study, and environmental and social impact study) and operating reports.
2) Consultation with staff, resource persons and local populations to collect data on the Sfax Sud WWTP and the current state of the El Hajeb Perimeter. This consultation was to verify the collected information to accurately complete the data tables. Some data could not be collected, however, especially at the level of ONAS.
3)Field observations, investigations and direct contact with the farmers at the site of the El Hajeb Perimeter were also carried out to determine which crops are grown and current resource and use constraints.
4)ONAS (National Sanitation Office) operating reports of Sfax Sud Wastewater Treatment Plant, 2009–2013 and operating reports of the Sfax Sud WWTP (not complete reports), 2016–2017 and 2018.

Study Results

The Sfax Governate is an arid to semi-arid zone on the east coast of Tunisia with an average temperature of 20°C. It has an annual negative water balance of 1,000 mm, which is when demand exceeds supply. This means that irrigation is necessary to help farmers achieve the best crop yields. Given the scarcity of natural water resources including both groundwater and surface water, recycled water from wastewater treatment plants provides a valuable new water source that can be used for irrigation. This approach forms part of the national strategy for agricultural water recycling and has been adopted in the Public Irrigated Perimeter of El Hajeb (hereinafter the El Hajeb Perimeter). The El Hajeb Perimeter is the first of its kind in Sfax. It was developed in 1988 on state-owned land and covers 240 ha. It is irrigated by recycled water from the Sfax Sud Wastewater Treatment Plant (hereinafter Sfax Sud WWTP). Given the good results achieved in terms of agricultural development and both the ongoing and predicted climatic conditions in the area, the perimeter area was extended several times during the 1990s and 2000s and now covers 444 ha divided between seven farmers (Figures 3.1 and 3.2). Sfax Sud WWTP serves a population of around 526,800 people and is located 6 km south of Sfax city. Collected wastewater enters the station from basins in Sfax Centre and Sfax Sud from domestic (47%) and industrial water (21%) sources. Upon arrival, it is treated at a secondary level using a low-load activated sludge treatment system (Figure 3.3), which biologically removes biodegradable organics and nutrients. Currently, Sfax Sud WWTP is undergoing rehabilitation works under the oversight and management of the National Office of Sanitation (ONAS) at an estimated cost of USD 2.8 million, financed by the African Development Bank. The size of the rehabilitation and expan sion works are based on a projected average flow of 52,000 m3 /day by 2026. This compares to its current capacity of 49,500 m3 /day. Recycled water reaches the El Hajeb Perimeter from Sfax Sud WWTP (Figures 3.3 and 3.4) via:
1. An intake structure that diverts part of the recycled water flow leaving Sfax Sud WWTP into a confined concrete inlet pipe that leads to the pumping station’s suction tank.
2. A pumping station that has a buried suction tank, a pumping room with four electric pumps and hydromechanical and electrical equipment.
3. An asbestos-cement delivery pipe that is 12 km long and conveys the recycled water to a tank in a 14 m high tower located at the head of the perimeter.
4. A distribution network from the tank consisting of asbestos-cement pipes equipped with irrigation hydrants.

The volume of water that is pumped to the perimeter varies between 1.4 m3 –3.7 m3 /year, giving a reuse rate of between 10–47%. This figure is variable due to the frequent breakdown of the pumping units and deterioration in the quality of the recycled water. Service to the seven farms within the El Hajed Perimeter is on demand.


Commitment of ONAS in projects concerning the improvement of wastewater treatment and the important potential of water reuse from the Sfax Sud WWTP: currently an average of 42,000 m3 /day and planned to reach 52,000 m3/day by 2026. Fertilizing power of recycled water: less mineral fertilizer inputs. High potential for agricultural land to be irrigated by recycled water and high motivation of farmers in the area for the project. No other source of water for irrigation near the existing perimeter. Development of cattle breeding in the area and the presence of a milk collection center nearby as well as oil mills. More than 30 years of experience with recycled water irrigation in the project area and a high rate of intensification in the existing perimeter (155%).

Poor treated wastewater quality that does not meet the requirements of the discharge standard (NT106-02) and the standard for reuse in irrigation (NT106-03). Lack of storage tanks at the head of the irrigation network. Restrictive list of authorized crops with few high-value crops. Low pricing set at USD 0.072/m3 . The costs of the reuse of the treated wastewater are largely borne by the CRDA. Increased operating costs due to the degradation of existing facilities (for the Sfax Sud WWTP and the El Hajeb Perimeter). Noncompliance with treated wastewater quality control frequencies and parameters to be analyzed, both at the Sfax CRDA and more recently at ONAS (since the launch of the Sfax Sud WWTP rehabilitation project in 2016). At the operational level, few material and human resources were allocated to the treated wastewater operator, especially given insufficient flows transferred to the perimeter due to the failure of the existing infrastructure. Lack of user awareness of the risks of treated wastewater and lack of resources to raise user awareness.

A political will to promote recycled water from wastewater treatment plants as a new source of water. Many users are willing to pay more for the quality of recycled water. Less discharge of treated wastewater into the sea reduces potential pollution, especially near the Sfax salt flats (RAMSAR site). The El Hajeb Perimeter has been in operation for about 33 years and constitutes an extensive field of research on the reuse of treated wastewater in irrigation. A desire on the part of the distributing body (Sfax CRDA) to promote the use of recycled water in the El Hajeb Perimeter and extend irrigated areas as a result of a general political will to promote the water reuse. Climate change is reducing conventional water resources, with water stress affecting Tunisia, particularly in the Sfax area including the salinization of groundwater, meaning water reuse is becoming even more critical. Flagship projects such as the Ouardanine Public Irrigation Perimeter for various fruit trees in addition to the El Hajeb Perimeter for fodder crops, dairy cattle breeding and olive trees.

Low rate of progress in the rehabilitation of the Sfax Sud WWTP. Illegal connection of polluting industries to the ONAS network affects the quality of treated wastewater. The producer and the treated wastewater quality controller belong to the same ministry which can create risks of conflicts of interest. It is noted that the treated wastewater produced often does not comply with the NT106-02 discharge standard, yet it sometimes is discharged into the sea or transferred to the perimeter without immediately informing the CRDA. Insufficient coordination amongst producers, distributors, managers and users. A lack of control over the quality of the treated wastewater produced. Difficulties in mobilizing funds for the upkeep and maintenance of existing installations and the realization of new complementary wastewater treatment projects provided by ONAS to address the majority of cases not compliant with the NT106-03 standard.

Supervision and monitoring of farmers is an important factor in the success of public irrigated perimeters.

The monitoring of treated wastewater shows quality fluctuations due to the existence of illicit polluted discharges in ONAS sewers despite continuous control of the networks. ONAS must commit to ensuring a good quality of treated wastewater and consider installing a complementary water treatment plant at the head of the perimeters irrigated through the water reuse project.

References (resources) Found is the case study

CRDA (Regional Commission for Agricultural Development). 2006. Feasibility study of the extension project of the El Hajeb Perimeter irrigated by recycled water from Sfax Sud Wastewater Treatment Plant. Tunisia. CRDA. .

CRDA. 2019. Feasibility study of the rehabilitation and extension project of the El Hajeb Perimeter irrigated by recycled water from Sfax Sud Wastewater Treatment Plant. Tunisia. CRDA.

CRDA. 2020. Detailed preliminary design study of the rehabilitation and extension project of the El Hajeb Perimeter irrigated by recycled water from Sfax Sud Wastewater Treatment Plant. Tunisia. CRDA.

DGGREE (Directorate General of Rural Engineering and Water Management). 2020. Environmental and social impact study of the rehabilitation and extension project of El Hajeb Perimeter irrigated by recycled water from Sfax Sud Wastewater Treatment Plant. Tunisia. DGGREE.

MARHP (Ministry of Agriculture, Hydraulic Resources and Fisheries). 2017. Fee policy evaluation study and review and implementation of new pricing schemes, Dual pricing of treated wastewater at the level of the Public Irrigated Perimeter – Phase 1 diagnosis. MARHP; DGGREE (Directorate General of Rural Engineering and Water Management); KFW (Kreditanstalt für Wiederaufbau).

MARHP. 2018. Preliminary study for a national plan Reuse of treated wastewater for Tunisia - Diagnosis of the existing situation. MARHP; ONAS (National Sanitation Office); the Ministry of Health.


ANPE: National Environmental Protection Agency
CRA: Agricultural Outreach Unit
GDA: Agricultural Development Group
CRDA: Regional Commission for Agricultural Development
CTV: Territorial Extension Unit
DGGREE: Directorate General of Rural Engineering and Water Management
DHMPE: Directorate of Environmental Health and Environmental Protection
MALE: Ministry of Local Affairs and the Environment
MARHP: Ministry of Agriculture, Water Resources and Fisheries
MSP: Ministry of Public Health ONAS Official Sanitation Office
ONAS: Official Sanitation Office
WWTP: Wastewater Treatment Plant