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In-situ thermal remediation, Bellinzona (Switzerland)

In-situ remediation with electric heating elements for the cleaning of soil contaminated with LCHCs
  • Aerial view of the remediation area in the old town © SBB CFF FFS
    Aerial view of the remediation area in the old town © SBB CFF FFS
  • The renovation field with the heating elements. © ZUT
    The renovation field with the heating elements. © ZUT
  • Activated carbon air filter in the foreground, beautiful old town in the background © ZUT
    Activated carbon air filter in the foreground, beautiful old town in the background © ZUT
Place
Bellinzona (Switzerland)
Client
SBB- Swiss Federal Railways
Special features
Limited space, close proximity to railroad tracks and residential buildings
Parameters
- Pollutants: CHC, almost exclusively PCE
- Floor air extraction with 1,100 m³/h, negative pressure up to 300 mbar
- Groundwater purification system up to 25 m³/h
- Installed heating capacity 730 kW, 350 kW cooling capacity
- Removal of approx. 210 kg of pollutants (corresponds to approx. 95 % of the inventory)
Performance period
March 2020 to December 2022

Thermal remediation of an CHC leak

The site of a former dry cleaning facility was heated using fixed, electrically operated heat sources (Video clip) and soil vapor extraction. The subsoil has a very inhomogeneous structure and low permeability. The LCHCs were located in the unsaturated soil zone at a depth of up to 15 m below ground level. The heating of the soil body and the extraction of the CHCs took place over an area of approx. 1,000 m². The outflow was hydraulically secured with the help of a groundwater purification system.

The remediation has been successfully completed and the remediation objectives have been achieved.

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Principle of the thermal renovation process (ISTH) with fixed heat sources © ZUT
Principle of the thermal remediation process (ISTH) with fixed heat sources

Scope of services

  • ISTH refurbishment: 194 drill holes for
    • 60 electric heating elements
    • 56 pcs. soil vapor extraction level
    • 77 temperature lances
  • Soil air purification: Air activated carbon filter
  • Groundwater purification plant
    • Sand filter, activated carbon water filter
    • Telecontrol technology, process visualization
  • Supply and operation of heating and measurement technology
  • Delivery and operation of the two-stage soil vapor extraction system and soil vapor purification via activated carbon air filters
  • Groundwater purification system in a narrow alley in the old town
    Groundwater purification system in a narrow alley in the old town

System technology in the narrow streets of the old town

The treatment system for the hydraulic barrier was designed for the confined installation area. Out of consideration for the residential area, the sound insulation of the system was of particular importance.