The works of maintenance and upkeep of sanitation facilities represent major activities for the operation units. These works include in particular: 

clearing of pumping stations sumps;
maintenance of the equipment installed in pumping stations;
operation and maintenance of treatment plants.

The maintenance of the sewerage network is conducted by the use of advanced mechanical equipment and machinery. Indeed, the ONAS equipment and machinery fleet comprises:

* 79 hydro jetting vehicles (including 11 mini hydro jetting vehicles);

* 13 large vacuum trucks

* 45 sludge equipment

* 30 vacuum trucks

* 56 mini jetting units on trucks for rapid intervention

* 01 combined hydro jetting/vacuum truck equipped with a recycling system

* 11 mini hydro jetting units capacity 2m3

* 04 mini combined hydro jetting/vacuum units capacity 2m3

* 02 mini vacuum trucks capacity 2m3

* 08 network inspection vehicles with camera systems

In order to carry out the activities above, the operation units draw up every year an annual programme for clearing the networks and annexed facilities, as well as for preventive maintenance of the wastewater and pumping facilities, and this in view of the human resources and equipment available and also of the profitability of the equipment and periodicity of the clearing operations. The intervention zones are listed in priority order and in terms of the relevant schedule. The annual programme is updated at the end of each month in view of the progress of the works.

Components of the operated network as of December 2023

Total network length:12720 km;
Inspection manholes:  438338 units
Storm water gutters:  62351 units

Connection boxes: 879351 units

Pumping stations: 838

Besides, ONAS has entrusted private developers with the activities of operating part of the network and its annexed facilities as follows:

Total network length: 5523 km ;
 Annex facilities : 176174 units

Connection boxes: 347082 units

Clearing of sewerage networks as of December 2023

ONAS services have undertaken as of December 2023, together with the private sector, the clearing of :
5 425 km of networks;
198434 inspection manholes and 1796 Storm water gutters.

 238590 connection boxes

Operation and maintenance of wastewater treatment plants

As of end of 2023, the number of wastewater treatment plants (WWTPs) amounted to 127 WWTPs, including the plants constructed in rural environment.
   These are the treatment processes used:
Activated sludge  
Oxidation ditch
  Natural ponds
Biological clarifiers
 Filtration sewer  

 Reed bed treatment systeme

Modern technologies are used in all wastewater treatment plants constructed by ONAS, which allow automatic operation of these plants. The latter are managed by specialised staff and technicians with expertise in wastewater treatment and maintenance of the electro-mechanical equipments. The quality of treated wastewater is regularly controlled in the laboratories installed at the plants or in private laboratories. Every year, some 40270 laboratory analysis operations are performed in this regard.