Anzali Wastewater Treatment Plant Eastern Zone

Client: Guilan Water & Wastewater Company
Partner: Mushrif of Kuwait
Type of contract: Design-Build-Operate (DBO)
Contract Period: 30 months construction, 12 months operation
Location: Guilan Province, Iran
Status: Under Construction

Project Outline

The main objective of East Anzali Wastewater Treatment Plant is to stem the increasing pollution of Anzali lagoon, rivers, and the Caspian Sea. The plant’s daily sewage treatment capacity stands at 12,000
cubic meters and it is designed to treat the household sewage of 57,000 of the city’s population which can be increased to serve a population of up to 120,000 in the future.

Anzali Wastewater Treatment Plant employs an activated sludge process and has an A2O biological system. The plant comprises two grit and grease removal, two circular primary sedimentation tanks, a wastewater pumping station, two biological units, two secondary sedimentation tanks and two coagulation unit tanks, four gravity sand filter units and finally UV disinfection basins. Units of coagulation tank, gravity sand filter (as complementary filtration) and odor removal system are what make this wastewater treatment plant distinctive compared to the other plants which are being designed and constructed in the country.

Treatment Process

Usually the first unit in a wastewater treatment plant is the “screening unit”. In Anzali Wastewater Treatment Plant, this unit is located in the pumping station outside the plant area. After screening unit, the wastewater flows into two parallel, aerated grit and grease removal chambers. When the grits are removed, the wastewater gets into two parallel “circular primary settling tanks” where 50% of suspended coarse particles are removed. Now the wastewater is ready to be biologically treated by aeration tanks. After biological treatment, wastewater flows into two parallel chambers known as “circular secondary settling tanks” where secondary sedimentation takes place. At the end of the process, effluent is transferred to four gravity sand filters (Aquazur V) where all the remaining suspended particles are removed and the wastewater is ready to be disinfected by two UV sets of lamps. The wastewater is now clear, disinfected and free from any hazardous bacteria and can be safely discharged into Anzali lagoon that is one the most valuable and important lagoons all over the world, having the international ecological aspect.

Key Statistics

Concrete: 9,100 m3
Formwork: 21,000 m2
Reinforcement: 725 t
Light & heavy steel work: 155 t
Earth & sludge removal: 70,000 m3
Earthfill: 150,000 m3
Rubble masonry: 8,190 m3


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