Zanjan sewage project (collection network and treatment plant)

Project features

Zanjan is the capital of Zanjan province .with an area of 22162 square kilometers in the northwest of Iran and is located at a distance of 324 km from Tehran. The city with a population of over 341801 people (in 2006) is considered as one of the country's major and important cities due to its location.

The first phase of sewage project was started in 1992 and implementation operation started in 1995. Principles and criteria for designing the city's wastewater collection system can be succinctly stated as follows.

The first phase of the city sewage collection has been done according to the needs of the Horizon Plan (2021) for a population of 566000 people and in an area of 7500 hectares. In the second phase, maps of the sewage network plan have been prepared on an area of 4500 hectares.

Principles of project

  1. Plan period: 25 years.
  2. Horizon of Project: 2021.
  3. The amount of waste produced per capita: 178 liters a day per person.
  4. Leakage of water entering the sewage network in the southern part of city: 22.5cubic meters; in the center and north of city it is 15 cubic meters per km network.
  5. The exploitation rate of the sewage system: 90% for the end of the plan year.
  6. The amount of waste produced in the city: 1.2 cubic meters per second.

The main components of the project

Primary and secondary sewage network lines

  The ramifications of domestic wastewater

   WWTP: Wastewater Treatment Plant of the city has been studied in three modules.

  1.  The first modules is designed is in operation in with a capacity of 320 liters per second (27648 cubic meters per day) for a population of 125 thousand
  2.  The second module with a capacity of 640 liters per second (250 thousand people)
  3.  The third module with a capacity of 320 liters per second (125 thousand people)


  • Prevention of pollution of surface and groundwater resources and protection of drinking, industry and agriculturewater resources
  • Promotion of public health and reduction of illness from contaminated water
  • Solving the problem of sanitation and public places sewage
  • Prevention of the spread of epidemics of intestinal infectious diseases
  • Reducing the level of government investment in treatment
  • Creating job opportunitiesfor labor.
  • Prevention of contamination of water, soil and air
  • providing continued survival for aquatic life
  • prevention of rising groundwater levels within city limits
  • Prevention of the degradation of agricultural land
  • Remove the adverse effects of moisture reaching the building foundation
  • allowing optimum utilization of available water resources through secure reuse of wastewater
  • Multiple circulation of water in resources and development of green spaces
  • Possibility of artificial recharge of groundwater aquifers by using effluents from sewage treatment plant
  • increasing the acreage and increasing agricultural production as well asfertilizing or reforming agricultural lands with wastewater
  • Fish breeding facilities using waste
  • Saving potable water and reduction of household and societyspending
  • Achieving sustainable development and protecting the environment and improving public welfare

Achieving these goals is possible by implementing wastewater collection network of the city for treatment according to Environmental Protection Agency standards and transfer for agricultural purposes or dispose to Zanjan River.

Project specifications

- Covered Area: 7500 hectares

- The population covered by the network: 566000 people

- Main pipelines: 48 km

- Semi-main and peripheral network: 492 km

- Diameter of sewage pipe line: 1200 and 1400 mm

- The length of the transmission line: 5 km

The total plant capacity: 3.1 cubic meters per second

Number of modules: 3 modules

- The population covered by the project: 566000 people

- The number of modules implemented in this stage: 1 module

- Covered Population: 125000 people

Wastewater treatment method: activated sludge - Conventional aeration

Main units: garbage-remover, grain-remover, primary sedimentation, aeration, secondary sedimentation, disinfection, gravity and mechanical concentration of sludge, sludge mixing and anaerobic digestion of sludge

Wastewater treatment method: gravity and mechanical concentration, anaerobic digestion