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Water treatment plant – Sisikon bypass tunnel, Sisikon (CH)

On behalf of the Implenia & Frutiger consortium, we have been operating our water treatment plant at the large construction site for the Sisikon Tunnel since late summer 2025 – one of Switzerland’s key infrastructure projects.
  • A picture of the tunnel water treatment plant, with Lake Lucerne in the background ©ZUT
    A picture of the tunnel water treatment plant, with Lake Lucerne in the background ©ZUT
  • Image of the pumping and analysis equipment installed in a container ©ZUT
    Image of the pumping and analysis equipment installed in a container ©ZUT
  • Photo of two Züblin Umwelttechnik employees at the plant ©ZUT
    Photo of two Züblin Umwelttechnik employees at the plant ©ZUT
  • Top view of the tunnel water treatment plant ©ZUT
    Top view of the tunnel water treatment plant ©ZUT
  • A picture of the tunnel water treatment plant, with Lake Lucerne in the background ©ZUT
    A picture of the tunnel water treatment plant, with Lake Lucerne in the background ©ZUT
Location
Sisikon (Switzerland)
Client
Implenia & Frutiger Consortium
Key figures
Flow rate up to 90 L/s
Special features
Cramped conditions with an outlet into Lake Lucerne
Period of service
Handover of the facility at the end of September 2025

Sources of wastewater at the construction site

The treatment plant processes all water from the construction site: water from tunnel boring operations and natural inflow into the tunnel, as well as surface water from the construction site.

Scope of services

  • 300 m³ buffer tank (to be provided by the client), including automated transfer
  • Pump sump and raw water pump
  • Neutralisation (using CO2 and chemicals)
  • Coagulation / Flocculation
  • Sedimentation using three inclined clarifiers connected in parallel
  • Nitrite treatment using sodium hypochlorite (bleach)
  • Sludge dewatering using a chamber filter press
  • Alert system via text message and email, remote access to systems
  • View of the entire construction site, including the tunnel water treatment plant
    View of the entire construction site, including the tunnel water treatment plant ©ZUT

Space-saving system design

Due to the severely limited space available on site, a plant design was chosen that requires a minimal footprint on the construction site. To this end, the entire plant has been constructed as a multi-storey structure. In addition to the actual tunnel water treatment, a further process stage for the removal of nitrite has been integrated. To ensure long-term compliance with the discharge limits into Lake Lucerne, the plant is equipped with several automatic analysis and measurement systems.