Construction of the new Sjölunda wastewater treatment plant

Expansion and remodeling of the Sjölunda wastewater treatment plant

The new Sjölunda wastewater treatment plant with a new treatment process will be built on the same site as the current wastewater treatment plant, while it is in full operation. To be successful, the work must be carried out in stages with major temporary diversions. 

Scope
Time: the work is divided into two phases: phase 1 – design planning is estimated to take 1,5-2 years and phase 2 – production is estimated to take around 8 years 
Treatment capacity: 820 000 population equivalent
Maximum flow: 10 cubic metres per second
Area: 600x350 metres
New buildings: around 20, totalling 30 000 square metres
New basins outdoors: 40 000 square metres
Pipelines: 10 000 metres
Concrete: 60 000 cubic metres
Excavation: 180 000 cubic metres

The new wastewater treatment process

Water treatment line

When the wastewater reaches the new wastewater treatment plant via the inflow pumping station, it first passes through screens that capture larger particles. Sand and gravel are then separated in sand traps before the wastewater passes to pre-sedimentation tanks where higher density particles sink to the bottom of the tank and form a sludge. The wastewater is then passed on to a biological process, the membrane bioreactor (MBR). There, the treated water is separated from the sludge by membranes with very small pores that allow only the treated wastewater to pass through. The wastewater then reaches the outflow pumping station. Most of the water treatment line will be new or reconstructed. Screens and sand traps are retained.  

The water treatment line will also consist of high flow treatment to be used when flows are high.  

Sludge treatment

The water treatment line produces sludge which is pumped to the sludge treatment plant. Sludge treatment will consist of mechanical thickening, pasteurisation, digestion and sludge dewatering. These plants components will be constructed or reconstructed.