Stockholm Vatten AB, the city’s main water company, commissioned Sweco to design and supervise works to double the capacity of Henriksdal Wastewater Treatment Plant from 800 000 PE to 1 600 000 PE. In order to achieve the required expansion of the treatment capacity at the existing site, Sweco identified Membrane Bioreactor (MBR) as the process solution. When it is completed, the Henriksdal WwTP will be the largest MBR plant in the world.
Client: Stockholm Water Company/ Stockholm Vatten AB
Location: Stockholm, Sweden
Fee Value: SEK 204m (£18.48m)
Time period: 2013 - 2021
The Henriksdal WwTP in central Stockholm is the largest underground plant in the world, covering 300,000 square metres and consisting of 18km of tunnels.
Sweco’s project was to develop and implement a solution for future wastewater treatment that would result in cleaner water in Lake Malaren, fewer discharges into the Baltic Sea and an end to shipments of sludge through residential areas.
Sweco’s pre-feasiblity study identified four possible solutions which included enlarging the existing plants, introducing different process solutions or constructing a new plant. The final decision was to to centralise the wastewater treatment of large parts of the city to Henriksdal WwTP by enlarging its size and decommissioning Brooma WwWTP. The land from Brooma would then be made available for future development.
Sweco has led the major components of the project, including the pre-feasibility study to detailed design and construction followed by the supervision / commissioning of the plant. The services provided include:
As the plant is located within rock caverns, the ability to extend were limited and as such Sweco had to define a robust process with a small footprint. In order to meet future discharge demands of BOD7 6mg/l, Tot-N 6 mg/l and Tot-P 0.2 mg/l and the limitations on space, we identified Membrane Bioreactor (MBR) as the process solution.
Membrane filtration allows more capacity within existing volumes. Also, the MBR system improves the separation of the activated sludge and the clean treated wastewater, or permeate.