1. Lessons learned from the Mediterranean countries using TWW for
agricultural production.
Xanthoulis Dimitri: Gembloux Agro-Bio Tech – Liege University
Reuse of treated wastewater (RTWW) began in Tunisia since 1965 to alleviate the great
pressure of the agricultural demand on water resources with 80% used for irrigation. The
practice of reusing treated wastewater is now widespread throughout the Mediterranean
area with limited success due to various reasons.
For example in Tunisia, after almost half a century of TWW reuse practice, many area
irrigated with wastewater suffer from low agricultural value. At the national level, only 25 %
of the WW are reused directly or indirectly in agriculture.
Factors that may hinder the use of treated wastewater are essentially inadequate quality of
water, the health risks and restrictions of use. Soil salinization is also mentioned in a lesser
proportion. Improving the quality of treated wastewater removes numbers of these
constraints.
Despite the stated desire to promote RTWW at national level, the poor quality of TWW is the
main constraint to reuse of treated wastewater in irrigated areas. This handicap limits the
full development of reuse despite all efforts to raise awareness, encouragement by applying
discount price, and the significant contribution of fertilizers in the TWW.
The poor quality of TWW has a direct negative impact on the irrigation equipment: (1) the
introduction of modern irrigation techniques such as drip irrigation is difficult and (2)
frequent maintenance of equipment is required, which makes costly and cumbersome the
irrigation activity.
Major new projects of RTWW are being prepared. Certain aloofness is necessary to assess
the situation and learn to avoid the same mistakes of the past and move eventually to new
options.
Many studies have been carried out, or are under development. Some correspond to
technical and environmental studies and others are prospective and strategic studies (such
as long distance transfer of TWW, groundwater recharge, irrigation of forest, irrigation of
energy crops to produce biofuel ...). All these studies agree that the success of irrigation
projects with TWW requires (1) the compliance of the TWW reuse standards for agriculture,
(2) the irrigation perimeter shall be as close as possible to the wastewater treatment plan (3)
the inter- seasonal storage should be possible and (4) involvement of beneficiaries must be
acquired . Moreover, the existence of an alternative water resource can divert the interest
of farmers for the RTWW.

2. Based on these findings, FAO, in collaboration with the World Bank and the Tunisian Ministry
of Agriculture, launched a strategic review to identify activities and necessary measures,
including the possibility of an integrated pilot project to improve the quality of treated
wastewater and the reuse.
After counting of studies on the treatment of wastewater at different Tunisian cities,
groundwater recharge studies, the transfer of TWW studies and agricultural reuse of treated
wastewater in several irrigated area, it is proposed to take immediate measures to rectify a
situation that seems to be deteriorating. It is proposed to launch four actions, some of which
will have a long term effect (the master plan) and other results in the short and medium
term (pilot projects):
1. A national master plan for wastewater reuse is developed to support the national
strategy for sustainable management of water resources.
2. The quality of treated wastewater is improved and allows reuse in agriculture by 2
activities:
a) Improving the management of industrial wastewater in the most relevant areas
(priority) for the RTWW,
b) Check the chain of public sanitation and identify, classify and remediate
anomalies according to relevance to the RTWW.
3. External conditions (support) are improved and farmers convinced of its interest.
4. The implementation of pilot projects can form and demonstrate simple techniques for
tertiary treatment and boost quickly unrestricted RTWW.
It is proposed that three pilot projects:
a) A first pilot project involving the monitoring of groundwater recharge,
b) A second pilot project for tertiary treatment by sand infiltration followed by a maturation
pond for direct reuse,
c) A third pilot project involves the implementation of a complementary treatment (tested of
different types of sand filters) before groundwater recharge to prevent clogging of
infiltration basins and the need for periodic partial regeneration.
Since the presentation of this strategy, GIZ launch an initial study for the implemantation of
a pilot project. The pilot project will be to choose a location based on local knowledge and
experience of the operators, in an area where the problem of salinity of wastewater does
not arise. The site should be installed downstream of a sewage treatment plant providing
TWW of medium quality that can be improved by sand filtration. The dimensions of the
infrastructure must be able to provide a volume of TWW of good quality to irrigate 10 ha.
The systems will be tested with surface and drip irrigation.