El Guelta wadi at the Ouardanine perimeter

Time period :


Implementing Institution/ Organization:

Monastir Governorate in central-eastern Tunisia

Funded by :

ONAS Ouardanine / Monastir / CRDA Monastir


1) promoting the use of recycled water from wastewater treatment plants at the national level.
2) rehabilitation and extending WWTPs and improving the quality of treated wastewater.
3) using recycled water enables the preservation of agricultural land located near the discharge outlet of the plant at the Oued El Guelta.
4) increasing agricultural production.

Methodology (approach)

1) Analysis of documentation concerning the Ouardanine Public Irrigated Perimeter and the Ouardanine WWTP.
2) Consultation with staff at local structures, resource persons and local populations to collect required data on the plant and the current state of the existing perimeter. Note that some data could not be obtained, especially concerning ONAS.
3)Field observations and investigations, which were carried out on June 17, 2021, at the Ouardanine Public Irrigated Perimeter. The investigations included direct communication with farmers to determine crops grown and current operating constraints.

Study Results

The Ouardanine Perimeter is irrigated by recycled water from the Ouardanine WWTP, which is located 2 km north of Ouardanine town in the Monastir Governorate. Wastewater collections come from predominantly domestic sources in the town, although some wastewater comes from industrial sources, for example, car washes and slaughterhouses. The Ouardanine WWTP was built with a design flow of 1,500 m3 /day, which is expected to be increased to 2,900 m3 / day when the current extension project is completed. Wastewater is treated at a secondary level by a medium-load activated sludge treatment system at the plant and then conveyed to the Oued El Guelta wadi upstream of the Ouardanine Perimeter (Figure 4.2) by means of: A storage basin with a capacity of 1,000 m3 that is located near the Ouardanine WWTP’s discharge point into the El Guelta wadi. A filtration plant consisting of two gravel filters, two screen filters and two disc filters. A pumping station with a suction tank equipped with three 20 L/s pumps of 40 m in height, one of which is an emergency pump. A 2.4 km long DN250 asbestos cement delivery pipe. A semi-underground reinforced concrete regulation tank with a capacity of 500 m3 is located at the head of the perimeter. A buried piping distribution network fed by gravity from the regulation tank equipped with 22 irrigation hydrants. The irrigation hydrants are reinforced concrete manholes with tamper-proof closures and equipped with valves and a meter, although it is noted that these meters are generally out of order. The payment of volumes used by each farmer is made on a flat rate basis in relation to the irrigated area. A common fee is applied corresponding to an annual amount of USD 99/ha/year/farmer. Plot networks with buried PVC pipes installed by farmers. The irrigation techniques used are localized for arboriculture while sprinkler irrigation is used for forage crops. The creation of the Ouardanine Perimeter has resulted in significant socio-economic, health and environmental benefits. Economic benefits include an increase in the value of agricultural land. The price of an irrigated hectare increased from USD 1,800 in 1996 to USD 1,364 in 2014. It is currently valued at USD 7,182. There has also been an increase in the agricultural production of the irrigated farms, which represents triple the average recorded in the whole of the Republic of Tunisia including: 25 ha of peach trees with an average production of 30 tons/ha. 10 ha of fig trees with an average production of 10 tons/ha. 15 ha of pomegranate trees with an average production of 40 tons/ha. 24 ha of olive trees intercropped with various fruit trees. Jobs have also been created for young people in the project area as the number of working days has increased from 20 days/ha in 1996 to 155 days/ha just four years after the perimeter was irrigated. Environmental benefits include minimizing the discharge of recycled water from Ouardanine WWTP into the El Guelta wadi. In 2019, between March to September, all of the recycled water was used within the perimeter as a result of a significant lowering of the water table, which is an ongoing challenge. This enabled the return of agricultural activity on 7.2 km of land located near the wadi that had been previously damaged because of discharge (Image 4.1). Other benefits include the use of treatment sludge from the plant as an organic fertilizer. The Ouardanine Perimeter also plays an important role in raising awareness of irrigation by recycled water from wastewater treatment plants at the local as well as national levels. It receives an average of 1,000 visitors each year. The Ouardanine Perimeter is located in an extensive agricultural area where both arboriculture (especially dryfarmed olive trees) and cattle rearing (without a grazing area owing to the absence of irrigation and fodder production) play an important role in generating income for the population. The absence of other sources of conventional water and the aridity of the climate makes the possibility of extending the irrigated area highly probable, particularly given the demands made by a large proportion of the farmers in the area who deem it necessary.


A significant potential in continuous recycled water availability throughout the year. Fertilizing power of recycled water means less mineral fertilizer use. High potential for agricultural land to be irrigated and high motivation of farmers in the area for the project. No other continuous source of water for irrigation near the existing perimeter. More than 24 years of experience with recycled water for irrigation in the project area and a high rate of intensification in the existing perimeter (140%).

Restrictive list of authorized crops with few high-value crops. Poor pricing, set at USD 0.072/m3 , which means costs of reusing treated wastewater are largely borne by the CRDA. Frequencies of non-compliance with recycled water quality control and all other parameters to be analyzed, at the CRDA and the ONAS. Poor management of the additional treatment equipment installed at the head of the perimeter including algal growth in the storage tank. This tank is very deep (3 m), which favors the development of septic conditions.

A political will to promote water reuse. Many users are willing to pay more for recycled water from wastewater treatment plants to get better quality water. Less discharge into the wadi and sometimes all of the recycled water produced is used (from March to September).

Poor flow of the El Guelta wadi following discharges of treated wastewater and sludge which generate the development of vegetation formed by reeds and other halophilic plants which slow down water flow. This causes a rise in the static level of the water table which can asphyxiate the fruit trees, salinization of the soil and proliferation of insects, as well as odor nuisance. Difficulties related to the quality of the recycled water.

Lessons learned

The supervision and monitoring of farmers is an important factor in the success of public irrigated perimeters.
The quality of the water produced by the WWTPs and supplied for irrigation must comply with at least the NT106-02 discharge standard to ensure efficient operation of the public irrigated perimeters. The installation of a complementary treatment plant at the head of the perimeters, as in this case, is becoming a necessity given the fluctuations in the quality of treated wastewater throughout the operation of the WWTPs and illicit polluted discharges into the ONAS sewers despite continuous control of the networks.

References (resources) Found is the case study

CDRA (Regional Commission for Agricultural Development). 2020a. Irrigated Perimeter, Follow up sheet. Ouardanine. CRDA. .

CRDA. 2020b. Physico-chemical and bacteriological analysis sheets for treated wastewater collected from the Ouardanine Public Irrigated Perimeter storage basin (2019 and 2020). Monastir. CRDA.

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. Tunisia. MARHP; DGGREE (Directorate General of Rural Engineering and Water Management); KFW (Kreditanstalt für Wiederaufbau).

ONAS (National Sanitation Office). 2003. Feasibility study for the development of treated wastewater reuse in the Ouardanine region. Republic of Tunisia. ONAS.

ONAS. 2018a. Preliminary study for a national plan: Reuse of treated wastewater for Tunisia - Diagnosis of the existing situation. Tunisia. MARHP (Ministry of Agriculture, Hydraulic Resources and Fisheries); ONAS; the Ministry of Health.

ONAS. 2018b. Ouardanine wastewater treatment plant activity report. Ouardanine. ONAS.


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
WWTP: Wastewater Treatment Plant