The region of Grand Gabès currently has about 190,000 inhabitants. It is equipped with a sewerage network that covers 90% of the region, and a wastewater treatment plant ( WWTP) with a capacity of 17,800 m3 / d) built since 1995 and which no longer meets the technical, social and environmental requirements and also to the urban and economic growth of the governorate.
The Government of Tunisia currently is aiming to improve the quality of the sanitation service and the living environment of the citizens in addition to protection of the environment in the region of Grand Gabés.
That require the setting up of a new treatment system, based on two wastewater treatment plants separated by the diversion channel of the wadi of Gabès (south plant and north plant) and this, in accordance with the recommendations of the master plan of the governorate of Gabès developed in 2017. The estimated costs of the project is TND 175 million
Accordingly, adding new treatment capacity and improving treatment efficiency are considered the main two objectives of this project in order to utilize and reuse the treated wastewater. Moreover, that could help to significantly reduce gap in water demand in this area specially for agriculture purposes.
In order to enhance the current situation and improve treatment efficiency, we shall have a deep understanding of the current situation and current treatment scheme. Therefore, we will provide in the next section a comprehensive description for the existing WWTP at Gabès.
The Gabès City Wastewater Treatment Plant currently receives 20,000 m3/d of municipal wastewater from Gabès City. Under normal circumstances, sludge would be removed regularly; however, following the Tunisian revolution of 2010-2011, the treatment plant did not receive this routine maintenance, and the treatment efficiency has decreased as a result. During the revolution, the laboratory and some of the equipment at the facility were vandalized, and historical records were destroyed by fire.
Despite these challenges, the facility continues to operate, and a portion of the effluent is pumped to the Dissa Agricultural Area, located 8 km northwest of Gabès City, for irrigation purposes.
Current treatment scheme:
The treatment process currently adopted is considered as one of the conventional treatment processes that provides a secondary treatment for wastewater, which is the activated sludge process.
The section below provides a general overview on the system used in the treatment
An important part of the municipal wastewater treatment is the BOD-removal. A biological process, such as the suspended growth treatment process, does the removal of BOD. This biological process is an aerobic process and takes place in the aeration tank, in where the wastewater is aerated with oxygen. By creating good conditions, bacteria will grow fast. The grow of bacteria creates flock and gases. These flock will be removed by a secondary clarifier.
Activated sludge refers to a mixture of microorganisms and suspended solids. The bacterial culture is cultivated in the treatment process to break down organic matter into carbon dioxide, water, and other inorganic compounds. The typical activated sludge process has following basic components:
. Primary Clarifier to separate the solids carried along with Sewage/Effluent
. A reactor in which the microorganisms are kept in suspension, aerated, and in contact with the waste they are treating
. liquid-solid separation; and
. A sludge recycling system for returning activated sludge back to the beginning of the process.
There are many alternatives of activated sludge processes, including alternatives in the aeration method and the way the sludge is returned to the process.
Activated sludge process offers efficient reduction of BOD, COD and nutrients when designed and operated correctly. The process itself has flexibility and numerous
modifications can be tailored to meet specific requirements (e.g. for nitrogen removal).
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Project stage info
Stage 1: Initial Government Announcement
Government of Tunisia
Form of project announcement
Aiming to overcome water quality and capacity issues in the city of Gabes and the surrounding areas, the project’s main objectives are focused on adding new treatment capacities and improving treatment efficiency in order to utilize and reuse the treated wastewater. Therefore, that could help to significantly reduce gap in water demand in this area specially for agriculture purposes.
The sanitation master plan of the governorate of Gabès approved in December 2017, studied several sewage treatment scenarios of different cities and regions of the governorate of Gabès.
Proposed solution for treatment in Gabès Scope of work
For the sanitation of Grand Gabès the master plan proposed the following configuration:
. The creation of two new treatment plants with the creation and reconfiguration of corresponding networks and the eventual abandonment of the existing wastewater plant.
. A North WWTP of Gabès receiving wastewater from areas of North Gabès (collection basins located north of the diversion channel of the Gabed wadi), Ghannouche, Chnenni-Nahal and the industrial zone of Gabès and;
. Another WWTP on the southern coast of Gabès that receives wastewater from the southern Gabés areas (collection basins south of the diversion channel of Gabés wadi), Kettana, Zrig-El Guendri and the future tourist zone of Gabés (325 ha)
. Agricultural and industrial upgrading of treated wastewater (disposal of 10,000 m3/d for the factories of the chemical group in Gabés and reinforcement of the reuse of the existing agricultural perimeter in the Eddissa zone (located in the Gabés Nord region)
. Development of an outfall at sea at the southern Step Gabés estimated length of 2900 meters
Indicative timetable of project development
There are no Project documents available at this time
Project looking for additional PPF assistance
Project looking for additional MDB assistance
Is project multi jurisdictional?
Stage 2: Project Investigation
60 M USD 175 M TND
Indicative Funding Source
Not Yet Known
Have any external advisors been appointed yet
Is the project contained in national/sub national infrastructure plan or strategy
Please outline any studies (for example environmental, engineering etc.) that will be completed prior to a full business case development
Political-, Social, Technical Studies
Opportunity for Private Sector Involvement
Not yet known
Stage 3: Start of Project Feasibility / Business Case
Legal Advisors Appointed
Financial Advisors Appointed
Technical and Other Advisors (inc Project Preparation Facility) Appointed
Is a Business Case Being Prepared?
Business Case Prepared By
Preparer company/department name
Government of Tunisia
Estimated Business Case Completion Date
Estimated Time To Start Of Procurement
Unable to be estimated at this time