ISCO Pilot Test

It is proposed as an alternative for the remediation of the dissolved plume area located downstream the former Bailin landfill.
The implementation of the test will permit to verify that it is possible to transfer the obtained results from lab to field. It will also allow us to assess the viability of ISCO as a remediation technique in a site that presents relevant geologic and hydro-geologic singularities.

Methodology

 

The implementation of the technique involves the introduction of the oxidant agent (persulphate with caustic soda) in the main paths of groundwater flow. It also involves the recirculation of the mixture (water and oxidant) through the cell (aquifer) using the most appropriate injection and extraction wells.

The pilot area consists of an aquifer section with the following characteristics:

-It is located in the high affected area of the dissolved plume.
-It is representative of the hydrogeological and geochemical conditions.
-Its geological features are known in depth.
-It has already a monitoring network.

 

The SELECTED AREA is located in the M layer, between gully 3 and 4.

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Location of the selected area for the pilot test
Location of the selected area for the pilot test

 M LAYER CHARACTERISTICS 

• Length: 100 m
• Thickness: 4 m
• Main fracture pathways: between 30 - 50m depth
• Fracture density: 0,75 - 1,5 fracture/m
• Rock volume: 8.000 m3
• Volume of water to be treated: 30 - 120 m3

 

 

 

 

 

Necessary infrastructures to implement the test

Diagram of the monitoring wells in M Layer
Diagram of the monitoring wells in M Layer

 

To implement the test, a network with 10 control points is required:


• 1 borehole upstream the treatment area
• 3 boreholes downstream the treatment area
• 1 monitoring borehole in a different layer downstream the treatment area
• 1 injection borehole upstream the cell
• 1 extraction borehole downstream the cell
• 3 monitoring boreholes along the treatment cell

 

In situ implementation and monitoring

 

Once the basic infrastructures are ready, the pilot test will be initiated.

Its operation will follow a scheme with a recirculation loop in the selected cell and monitoring actions both in the cell itself and in the environment.

Recirculation entails:


1. To inject oxidant at a specific well upstream the cell.
2. To pump at a specific well downstream the cell.


The aim of recirculation is to optimize the consumption of oxidant and to minimize the risk of uncontrolled reactions outside the treatment area.

 

Sketch of recirculation in the treatment area (M layer)
Sketch of recirculation in the treatment area (M layer)

Expected results

It is foreseen that the ISCO pilot test will start in the middle of 2015. Real results are not available yet, but from the ISCO technique it is expected:

• To check in situ the results obtained in the lab.
• To assess the pilot test effectiveness for the existing pollutants mixture identified in the aquifer.
• To assess and quantify the necessary doses of oxidant/activator and to verify the results obtained in the lab.
• To assess the applicability of the technique as well as its technical limitations and determinants.