SOIL, SEDIMENT AND SLUDGE: IN-SITU CHEMICAL/PHYSICAL TREATMENT
Soil Flushing
Typical Soil Flushing (Spray Application)
Standard Process:
Cosolvent Flushing Enhancement
[Solvent mixture: water with a miscible organic solvent (e.g. alcohol)].
Uses:
Limitations:
Cost:
Largely affected bysoil permeability and the depth to the groundwater:
- Water (usually with flushing additives) is sprayed over land or injected into the ground to enhance the contaminant's solubility.
- The water table rises allowing contaminants to leach into the ground water for their extraction & treatment.
- Generally of short-medium-term duration.
- Enhanced by flushing with surfactants (Cosolvents).
Cosolvent Flushing Enhancement
- A solvent mixture can be injected into both the vadose or saturated zones - dissolves & treats both the source & plume of contamination.
- It must be injected up-gradient of the contaminated area & then extracted (with dissolved contaminants) down-gradient of the contaminated area.
- The treated water is then re-injected into/sprayed over the ground and re-used as the flushing fluid.
[Solvent mixture: water with a miscible organic solvent (e.g. alcohol)].
Uses:
- Treats inorganics (such as radioactive contaminants), VOCs, SVOCs, fuels, and pesticides.
- Potential recovery pf metals
- Mobilise a wide range of organic and inorganic contaminants from coarse-grained soils.
- Surfactants can be added to increase solubility of organic compounds (may alter soil properties).
Limitations:
- Difficult to treat low permeability/heterogeneous soils.
- Surfactants can adhere to soil - may reduce effective soil porosity & hence flow rates.
- Flushing fluids may react with the soil, reducing contaminant mobility.
- Must be able to contained & capture flushed contaminants & soil flushing fluid.
- Often less cost-effective for VOCs, SVOCs, fuels & pesticides than alternative technologies.
Cost:
Largely affected bysoil permeability and the depth to the groundwater:
- A less permeable soil requires a much greater treatment time - significantly increased cost.
- A deeper water table also increases the cost.