Tunisian Republic Ministry of Infrastructure and spatial planning

National Sanitation Utility

WASTEWATER TREATMENT IN TUNISIA

WASTEWATER TREATMENT IN TUNISIA

Elaborated by

- Nabiha OUERFELLIApril 2014

SUMMARYSUMMARY

ONAS : PRESENTATION

ONAS:ONAS: Principal Principal Operator of Sanitation in Tunisia Operator of Sanitation in Tunisia

ONAS was established ONAS was established by Law N° 73/1974by Law N° 73/1974, this law was , this law was amended by virtue of Law N° 41/1993, ONAS was amended by virtue of Law N° 41/1993, ONAS was entrusted with the mission of management of the entrusted with the mission of management of the sanitation sectorsanitation sector

ONAS is a public institution of an industrial and ONAS is a public institution of an industrial and commercial charactercommercial character

enjoys civil status and financial autonomy enjoys civil status and financial autonomy

ONAS actions include the following fields: Studies, Works, ONAS actions include the following fields: Studies, Works, Operation and maintenance (O & M) of sanitation Operation and maintenance (O & M) of sanitation networks and facilities and Technical assistance.networks and facilities and Technical assistance.

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Missions:Missions:

Combating the sources of water pollution under ONAS Combating the sources of water pollution under ONAS purview purview

Management, operation, maintenance, rehabilitation Management, operation, maintenance, rehabilitation and construction of all facilities intended for the and construction of all facilities intended for the sanitation of the towns assigned to ONAS by decreesanitation of the towns assigned to ONAS by decree

Promoting the sector of the sale and distribution of the Promoting the sector of the sale and distribution of the sub-products of wastewater treatment plants, such as sub-products of wastewater treatment plants, such as treated wastewater and sludgetreated wastewater and sludge

Planning and implementation of the sanitation sector Planning and implementation of the sanitation sector programmesprogrammes

Planning and implementation of integrated projects Planning and implementation of integrated projects related to the treatment of wastewater and disposal of related to the treatment of wastewater and disposal of storm water. storm water.

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ONAS : PRESENTATION

State budgetState budget

External loans and External loans and grants 59 % grants 59 %

Sanitation feesSanitation fees 59 % 59 %

InvestmentsInvestments94 million TND94 million TND

Operating costsOperating costs264,8 Million 264,8 Million TNDTND

39 %

41%

FINANCIAL RESSOURCES OF ONAS

Other incoms Other incoms 2 % 2 %

ONAS : PRESENTATION

Principales implementationsPrincipales implementations

Major achievements have been identified from the Major achievements have been identified from the

sanitation master plans and feasibility studies. They sanitation master plans and feasibility studies. They

were concerned at the beginning to the major cities, were concerned at the beginning to the major cities,

tourist and industrial development zones.tourist and industrial development zones.

Secondly, priority was given to small and medium-sized Secondly, priority was given to small and medium-sized

cities and suburban areas.cities and suburban areas.

Finally, the districts have in turn benefited from a major Finally, the districts have in turn benefited from a major

program involving 1.5 million people spread over 1000 program involving 1.5 million people spread over 1000

districts. districts. 6

ONAS : PRESENTATION

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Tataouine

Kébéli

Medenine

Tozeur

Gabès

Gafsa

KasserineSidi Bouzid

Sfax

Kef Béjà

Jendouba

Bizerte

Kairouan

Mahdia

Sousse

Zaghouan

NabeulThe total number of The total number of

wastewater treatment plants: wastewater treatment plants: 110110

- 101 plants treat wastewater 101 plants treat wastewater of urban origin,of urban origin,

- 2 plants treat industrial 2 plants treat industrial wastewater,wastewater,

- 7 plants treat wastewater of 7 plants treat wastewater of rural areasrural areas

Connection rate to ONAS: 90%Connection rate to ONAS: 90% For the area supported by For the area supported by

ONAS ONAS

ONAS : PRESENTATION

The capacity of these treatment plants varies from 200 The capacity of these treatment plants varies from 200 m3/d (Hammem Bourguiba) up to 78,000 m3/d m3/d (Hammem Bourguiba) up to 78,000 m3/d (Choutrana1).(Choutrana1).

Treatment plants in operation have been used to treat Treatment plants in operation have been used to treat 232 million m3 of wastewater 232 million m3 of wastewater - 41% of TWW from Greater Tunis,- 41% of TWW from Greater Tunis,-19% of TWW from northern Tunisia in which The -19% of TWW from northern Tunisia in which The region of Nabeul represents 50% of the total volumeregion of Nabeul represents 50% of the total volume-23% of the TWW from the center of Tunisia,-23% of the TWW from the center of Tunisia,-17% of TWW from southern Tunisia -17% of TWW from southern Tunisia

8% of treated wastewater is of industrial origin8% of treated wastewater is of industrial origin

ONAS : PRESENTATION

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Distribution of WWTP by type of methods of treatmentDistribution of WWTP by type of methods of treatment

84% of wastewater treatment plants are activated sludge-type 84% of wastewater treatment plants are activated sludge-type (medium and low load), the most effective method of treatment (medium and low load), the most effective method of treatment efficiency with up to 98%efficiency with up to 98%

85

14 2 7

activated sludge

lagoon

trickling

constructed wetland

ONAS : PRESENTATION

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SLUDGE MANAGEMENTSLUDGE MANAGEMENT

Issues:

Reviving the agricultural use for sustainable sludge

Avoid the impact of sludge management on the quality of treatment and environment

Meet the conditions of Land filling (specific or mixed)

Extend the value of the sludge to produce energy

Thermal recovery of sludge in the industry (cement)

In treatment

- Aerobic Stabilization:

- anaerobic Stabilization-

In drying

-Natural drying : 39 %

- Mechanical drying : 61 %

Sludge disposal

- Landfill: 24%- Storage in site of WWTP : 35%- Storage in deposit site of ONAS : 41%

Control of wastewater are carried out at the Control of wastewater are carried out at the laboratory level of WWTPs and in private laboratories. laboratory level of WWTPs and in private laboratories.

(Last year ONAS done by private 4039 analysis)(Last year ONAS done by private 4039 analysis)

Control parameters must obey to the effluent standards

For water (raw or treated): NT 106 002 (1989)

For sludge: NT 106.20 (2002)

For reuse : NT 106.003

ONAS : PRESENTATION : quality control

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Parameters for monitoring

Pollution indicators : Biological oxygen demand (5 days) BOD5 Chemical oxygen demand COD Suspended solids TSS Ionic balances (anions and cations) total nitrogen Ntot total phosphorus Ptot Nitrates, nitrites, ammonium, NO-3, NO 2, NH 4 Heavy metals (Cr tot, Cr VI, Ni, Cd, Pb, Fe, Zn, Cu, Hg) Oils and fats Bacteriology (total and fecal coliforms, Faecal streptococci, E. coli) Parasitic (helminth eggs)

In some cases, wastewater can be clean enough for In some cases, wastewater can be clean enough for reuse for particular purposes. reuse for particular purposes. ((Reuse rate : 30 %Reuse rate : 30 %))

Currently, treated wastewater from 34 WWTP are reused Currently, treated wastewater from 34 WWTP are reused in agriculture, golf courses and green spacesin agriculture, golf courses and green spacesWe have We have modest experience in the field of groundwater modest experience in the field of groundwater recharge in the region of Nabeulrecharge in the region of Nabeul

ONAS conducts additional treatment in order to remove ONAS conducts additional treatment in order to remove microbial pollution, phosphorous and nitrogen in certain microbial pollution, phosphorous and nitrogen in certain wastewater treatment plants located in the vicinity of wastewater treatment plants located in the vicinity of sensitive water mediums, as well as to prevent health-sensitive water mediums, as well as to prevent health-related hazards, according to the final destination of related hazards, according to the final destination of treated wastewater disposaltreated wastewater disposalIn Tunisia we have 17 WWTP using tertiary treatmentIn Tunisia we have 17 WWTP using tertiary treatment

the different technologies used are:the different technologies used are: Sterilisation by ultra-violet rays ; (5 WWTP)Sterilisation by ultra-violet rays ; (5 WWTP) Sand filtration (percolation) + sterilisation by ultra-violet Sand filtration (percolation) + sterilisation by ultra-violet rays ; (4 WWTP)rays ; (4 WWTP) Maturation ponds; (8 WWTP)Maturation ponds; (8 WWTP)

ONAS : PRESENTATION : Reuse and complementary treatment

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The main axes of development focus on the following programs:The main axes of development focus on the following programs: Development and extension of sanitation infrastructure to meet Development and extension of sanitation infrastructure to meet

an urgent demandan urgent demand - Extension and rehabilitation of WWTP- Extension and rehabilitation of WWTP - Improve the processing to reach standards;- Improve the processing to reach standards; sludge Management program sludge Management program - Equipping treatment plants through technologies that improve - Equipping treatment plants through technologies that improve

the dryness of the sludge producedthe dryness of the sludge produced- Construction of sludge deposit sitesConstruction of sludge deposit sites

Energies efficiency programEnergies efficiency program- Energy optimisation of sludge : this consist in the production of Energy optimisation of sludge : this consist in the production of

Electrical and thermal energy based on biogazElectrical and thermal energy based on biogaz- Substitution of the old aeration to ameliorate the energy Substitution of the old aeration to ameliorate the energy

consumption consumption

Industrial Wastewater program (Industrial Wastewater program (Establishment of common Establishment of common treatment plant for treating industrial wastewater, treatment plant for treating industrial wastewater, separate separate WWTP between urban and industrial)WWTP between urban and industrial)

Program for the reuse of treated wastewaterProgram for the reuse of treated wastewater

ONAS : PRESENTATION :Major programs

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IMPROWARE Project

WWTP of Korba : WWTP of Korba : Korba’s wastewater treatment plant is Korba’s wastewater treatment plant is a conventional activated sludge, followed by three a conventional activated sludge, followed by three maturation ponds in series acting as a tertiary maturation ponds in series acting as a tertiary treatment (MP1, MP2, and MP3).treatment (MP1, MP2, and MP3).

Treated effluent is essentially Treated effluent is essentially used for artificial recharge of used for artificial recharge of Korba aquifer; the rest is Korba aquifer; the rest is discharged into the Korba discharged into the Korba lagoon to maintain its lagoon to maintain its ecological equilibrium ecological equilibrium

Flow : 7764 m3/dFlow : 7764 m3/d

Pollution load : 3164 kg/dPollution load : 3164 kg/d

Population equivalent : 74 898 Population equivalent : 74 898 inhabitant inhabitant

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IMPROWARE ProjectIMPROWARE Project

In the WWTP of Korba, A hydrodynamic study In the WWTP of Korba, A hydrodynamic study demonstrated the existence of short circuits and dead demonstrated the existence of short circuits and dead zones in the zones in the maturation pondsmaturation ponds, so how to improve the , so how to improve the removal efficiency of these pondsremoval efficiency of these ponds..

to reduce the short to reduce the short circuiting flow and the circuiting flow and the

dead zonedead zone

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CONCLUSIONCONCLUSION

An An appropriate engineering intervention reduces dead zone and appropriate engineering intervention reduces dead zone and dispersion, optimises the hydraulic retention time; and dispersion, optimises the hydraulic retention time; and consequently improves the bacterial removalconsequently improves the bacterial removal

Maturation ponds installed at the end of activated sludge WWTP, Maturation ponds installed at the end of activated sludge WWTP, need better hydraulic design to improve bacteriological removal need better hydraulic design to improve bacteriological removal and to reach the and to reach the guidelines of waste water reuse.guidelines of waste water reuse.

Actions are :Actions are :Improving the quality of treated wastewater Improving the quality of treated wastewater

- Filter Sand before maturation ponds - Filter Sand before maturation ponds - Buffles in the first and second ponds- Buffles in the first and second ponds

Monitoring (quality of treated waste water and aquifer)Monitoring (quality of treated waste water and aquifer)

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