2.7.2.7 Conclusion
The results of laboratory tests in fully controlled conditions show that surfactant
flushing and surfactant foam flushing are promising techniques. The reduced interfacial tension and increased viscosity significantly reduce residual saturation. Surfactant foam flushing can overcome the effects of heterogeneity within a medium.
The techno-economic analyses show that these recovery techniques hold a
prominent place on the free product remediation market.
However, in contrast with laboratory tests, field tests carried out with surfactant
flushing and surfactant foam flushing were less convincing. They require comprehensive understanding of field heterogeneities (variations of porosity, permeability,
transmissivity), absolute control of the injection material, and finally, a very detailed
multiphase modeling. In order to overcome the abovementioned constraints, another
research project named PAPIRUS is currently underway.
2.8 General Conclusions and Recommendations
Pumping actions are necessary for recovering pure products (free products) before
implementing any other remediation action. These pumping operations are
performed by a pump-and-treat technique. They are lengthy (sometimes over several
decades), and expensive, and are not very effective in the long term because of
residual saturation, and slow release of contaminants into the aqueous phase.
For these reasons, enhanced technologies are frequently implemented to improve
the overall remediation yield. Hydraulic displacement, thermal treatment, and surfactant- or foam-enhanced extraction methods are the most commonly used remediation technologies to decrease the residual saturation, and reduce the duration of
operations.
Continued research must be conducted to better measure the effectiveness of pure
product recovery treatments, including conventional and indirect measurement and
monitoring methods (e.g., geophysics, partitioning interwell tracer test, etc.).
Other research and development actions must be carried out in order to better
appreciate the effects of a partial remediation of the pure product and associated
discharges. Efforts are also needed to better understand the physical/chemical/
biological interactions at NAPL interfaces.
Further investigation into Enhanced Oil Recovery (EOR) techniques is needed to
find sustainable ways to reduce residual saturation (and associated discharges), i.e.,
thermal enhancements, waterflooding, chemical enhancements, and foam injection.
Other avenues of research also include studying issues inherent to upscaling
(from lab scale to full scale) particularly as it relates to groundwater media heterogeneities. Further studies should also include numerical model calibration with
experimental data.
Finally, additional investigation should be carried out into remediation of polluted soils in fractured media and karst aquifers.
138
S. Colombano et al.
The results of laboratory tests in fully controlled conditions show that surfactant
flushing and surfactant foam flushing are promising techniques. The reduced interfacial tension and increased viscosity significantly reduce residual saturation. Surfactant foam flushing can overcome the effects of heterogeneity within a medium.
The techno-economic analyses show that these recovery techniques hold a
prominent place on the free product remediation market.
However, in contrast with laboratory tests, field tests carried out with surfactant
flushing and surfactant foam flushing were less convincing. They require comprehensive understanding of field heterogeneities (variations of porosity, permeability,
transmissivity), absolute control of the injection material, and finally, a very detailed
multiphase modeling. In order to overcome the abovementioned constraints, another
research project named PAPIRUS is currently underway.
2.8 General Conclusions and Recommendations
Pumping actions are necessary for recovering pure products (free products) before
implementing any other remediation action. These pumping operations are
performed by a pump-and-treat technique. They are lengthy (sometimes over several
decades), and expensive, and are not very effective in the long term because of
residual saturation, and slow release of contaminants into the aqueous phase.
For these reasons, enhanced technologies are frequently implemented to improve
the overall remediation yield. Hydraulic displacement, thermal treatment, and surfactant- or foam-enhanced extraction methods are the most commonly used remediation technologies to decrease the residual saturation, and reduce the duration of
operations.
Continued research must be conducted to better measure the effectiveness of pure
product recovery treatments, including conventional and indirect measurement and
monitoring methods (e.g., geophysics, partitioning interwell tracer test, etc.).
Other research and development actions must be carried out in order to better
appreciate the effects of a partial remediation of the pure product and associated
discharges. Efforts are also needed to better understand the physical/chemical/
biological interactions at NAPL interfaces.
Further investigation into Enhanced Oil Recovery (EOR) techniques is needed to
find sustainable ways to reduce residual saturation (and associated discharges), i.e.,
thermal enhancements, waterflooding, chemical enhancements, and foam injection.
Other avenues of research also include studying issues inherent to upscaling
(from lab scale to full scale) particularly as it relates to groundwater media heterogeneities. Further studies should also include numerical model calibration with
experimental data.
Finally, additional investigation should be carried out into remediation of polluted soils in fractured media and karst aquifers.
138
S. Colombano et al.