process and installation for the biological remediation of polluted soil placed in the form of a mound

Abstract

The invention relates to a biological remediation process for polluted soil (2) in the form of a mound, characterized in that the process comprises a step of injecting a shear-thinning aqueous fluid into the soil. Figure for the abstract: Fig. 1

Description

Title of the invention: method and installation for biological decontamination of polluted soil in the form of a mound Technical field of the invention

[0001] The present invention relates generally to the decontamination of soils.

[0002] It relates more particularly to a process for the biological decontamination of polluted soil in the form of a mound.

[0003] It also relates to an installation making it possible to implement such a method.

[0004] The invention finds a particularly advantageous application in the creation of bio-tertres. State of the art

[0005] Many bacteria naturally present in soils are capable of degrading pollutants such as hydrocarbons, provided that these pollutants are bioaccessible and biodegradable. Bacteria of the Mycobacterium strain are, for example, effective in degrading pyrene present in soils.

[0006] Biodegradation, or biological degradation, of polluted soils is mainly based on the establishment of conditions that favor the development of these bacteria, which, by proliferating, come to degrade the pollutants (which constitute their food source). To develop, the bacteria need in particular a sufficient level of humidity and preferably nutrients (carbon, nitrogen, phosphorus, potassium) and oxygen for aerobic biodegradation.

[0007] Conventionally, the treatment of soil by bio-pile involves excavating the polluted soil and constructing a mound, sometimes more commonly called a pile. Conventional decontamination installations then include: a hydraulic circuit for dispersing water, typically via nozzles, at the top of the mound in order to guarantee a sufficient humidity level; a gas pumping system to provide oxygen; and a water treatment system and, if necessary, gas treatment.

[0008] However, soil is an anisotropic porous medium. In other words, soil exhibits contrasts in permeability. Some less permeable areas of soil are difficult to access to bring water, and therefore potentially nutrients contained in the water, or even oxygen.

[0009] In addition, water infiltrating into the mound by gravity tends to follow preferential paths, like canals, to flow. Areas distant from these preferential paths are then not very humid.

[0010] Thus, the water supply is not homogeneous in the soil. Certain areas of the soil therefore see bacteria develop less efficiently, which limits pollution control yields. Presentation of the invention

[0011] In this context, the present invention proposes a method for the biological decontamination of polluted soil in the form of a mound, characterized in that the method comprises a step of injecting a rheofluidifying aqueous fluid into the soil.

[0012] Thus, thanks to the invention, the non-Newtonian fluid (for example a foam, composed of water, surfactants and air) is better suited to reaching the low permeability zones of the soil than a Newtonian liquid.

[0013] Indeed, since the fluid is shear-thinning, injecting the liquid into low-permeability zones increases the pressure and therefore reduces its viscosity. As a result, the fluid spreads in the soil, forming a flat front. In other words, the fluid spreads more homogeneously despite the differences in soil permeability.

[0014] The fluid being aqueous, the water is thus supplied with better homogeneity to the entire soil. The fluid, aqueous and rheofluidifying, makes it possible in particular to supply water to areas which would not be reached by gravitational infiltration of water.

[0015] Furthermore, since the fluid propagates in a substantially flat front in the ground, it generates few or no preferential paths.

[0016] As a result, since humidity is controlled more homogeneously in the soil, bacteria develop there with greater homogeneity, which makes it possible to increase decontamination yields.

[0017] Finally, the liquid according to the invention makes it possible to save water, in particular by avoiding or reducing its flow via preferential paths.

[0018] According to an optional and advantageous characteristic of the invention, the rheofluidifying aqueous fluid comprises oxygen.

[0019] Indeed, since most soil decontaminating bacteria are aerobic, it is necessary to bring oxygen into the soil. Thus, as with water, the non-Newtonian fluid makes it possible to bring oxygen in the form of air into the soil in a homogeneous manner, even though the latter is an anisotropic porous medium.

[0020] According to an optional and advantageous characteristic of the invention, the oxygen is injected into the soil solely by means of the rheofluidifying aqueous fluid.

[0021] In addition, the fluid makes it possible to reduce the use of, or even do without, the expensive ventilation systems that equip conventional decontamination installations. These ventilation systems make it possible to create a depression at the level of the mound, which is then covered by a plastic tarpaulin. The fluid therefore makes it possible to save energy and materials.

[0022] According to an optional and advantageous characteristic of the invention, the rheofluidifying aqueous fluid comprises a surfactant.

[0023] Thanks to the surfactant, for example contained in a foam, the fluid facilitates the passage of pollutants from a solid phase, on which they are adsorbed in the soil particles, to a liquid phase. In other words, the surfactant allows desorption and solubilization of the pollutants in the fluid or in a liquid naturally contained in the soil (for example water). Thus, the surfactant improves the availability, and more specifically the bioavailability, of the pollutants since the bacteria decompose the pollutants more efficiently in the liquid phase than in the solid phase. In addition, thanks to the shear-thinning fluid, the surfactant is supplied homogeneously to the soil.

[0024] According to an optional and advantageous characteristic of the invention, the rheofluidifying aqueous fluid is a foam comprising air bubbles and an aqueous solution which comprises a surfactant, the air bubbles being dispersed in the aqueous solution.

[0025] The fluid is thus made rheofluidifying thanks to compounds which are themselves useful for decontamination. The foam in fact provides water and oxygen (and potentially nutrients) for the proliferation of bacteria as well as the surfactant for increasing the bioavailability of pollutants. In addition, the viscosity of the fluid is easily adaptable by adjusting the size of the bubbles. Advantageously, the air used to generate the foam is also used to bring oxygen into the soil.

[0026] According to an optional and advantageous characteristic of the invention, the rheofluidifying aqueous fluid comprises nutrients adapted to the proliferation of bacteria present in the soil.

[0027] Indeed, the quantity of nutrients necessary for the proliferation of bacteria may be naturally insufficient in the soil. In this case, it is then preferable to provide additional nutrients in the soil. Thus, as for water or oxygen, the fluid makes it possible to provide nutrients in the soil in a homogeneous manner although the latter is an anisotropic porous medium.

[0028] Remarkably, the fluid alone can therefore provide all the resources that the bacteria need, whether water, oxygen or nutrients.

[0029] Other advantageous and non-limiting characteristics of the method according to the invention, taken individually or in all technically possible combinations, are the following: - air bubbles have a diameter between 1 pm and 5 mm; - air bubbles have a diameter smaller than an average pore size of the soil; - the foam comprises between 70% and 95% air by volume; - an injection rate of the aqueous rheofluidifying fluid into the soil and an injection pressure of the aqueous rheofluidifying fluid into the soil are determined on the basis of the granulometry of the soil; - the injection pressure of the fluid into the soil is less than 10 bar / m; - the method further comprises a step of forming the rheo-thinning aqueous fluid, the rheo-thinning aqueous fluid being injected immediately after its formation; - the soil is polluted by refined petroleum hydrocarbons.

[0030] The invention also relates to an installation for biological decontamination of polluted soil in the form of a mound, the installation comprising: - a generator suitable for producing a rheofluidifying aqueous fluid; - a circuit in fluid communication with the generator and adapted to inject the rheofluidifying aqueous fluid into the soil.

[0031] Other advantageous and non-limiting characteristics of the installation according to the invention, taken individually or in all technically possible combinations, are the following: - the rheo-thinning aqueous fluid is a foam and the generator comprises a compressor, a pump and a porous medium, the compressor being adapted to inject pressurized air into the porous medium and the pump being adapted to inject an aqueous solution comprising a surfactant, and preferably nutrients, into the porous medium so as to produce the foam; - the porous medium comprises an inlet for receiving the air and the solution and an outlet for expelling the foam, the generator comprising two pressure sensors adapted to determine a pressure difference between the outlet and the inlet of the porous medium. Detailed description of the invention

[0032] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0033] In the attached drawings:

[0034] [Fig-1] is a schematic side view of a biological decontamination installation of polluted soil placed in the form of a mound according to the invention.

[0035] [Fig.2] is a block diagram of a sequence of steps allowing the decontamination biological remediation of polluted soil in the form of a mound.

[0036] An installation 1 for biological decontamination of a soil 2 according to the invention is shown in [Fig.l]. The biological decontamination of the soil 2 here means the decontamination, or remediation, of the soil 2. The soil 2, which is intended to be treated by the installation 1, is polluted, in other words contaminated, for example by hydrocarbons refined petroleum products such as diesel, fuel oil, and kerosene. Soil 2 can also be polluted by volatile or semi-volatile organic compounds, pesticides, or oils. For example, soil 2 has a pollutant concentration of less than 30,000 mg / kg.

[0037] The soil 2 here comprises mineral matter and organic matter. The soil 2 is for example composed of earth. The soil 2 notably comprises bacteria capable of degrading the aforementioned pollutants. The decontamination is thus described as biological because it is carried out by the bacteria themselves. The installation 1 makes it possible to treat the soil 2 in such a way as to promote this biological decontamination, that is to say to increase the activity of the bacteria. This makes it possible, for example, to increase or accelerate the efficiency of the decontamination.

[0038] As shown in [Fig.l], the soil 2 is formed into a mound 20. Here, in the context of biological decontamination, the soil 2 therefore forms a biomound. For this, the soil 2 is previously excavated, that is to say extracted, for example by digging, then piled up so as to form the mound 20. The mound 20 has a generally pyramidal shape, rising from a base 21 towards a summit 22 which is narrower than the base 21. The mound 20 has, for example, a trapezoidal shape as shown in [Fig.l].

[0039] The installation 1 here comprises a support 3 on which the ground 2 is placed, more particularly the base 21 of the mound 20. The support 3 is for example a waterproof tarpaulin. In the example illustrated in [Fig.l], the installation 1 also comprises a geomembrane 4, i.e. a waterproof cover, which protects in particular the ground 2 from bad weather. The geomembrane 4 is here connected to the support 3, for example by means of a berm 5, so as to control the exchange of fluids, in particular water and air, between the mound 20 and the outside.

[0040] The installation 1 thus makes it possible to treat the soil 2 ex situ, i.e. outside its natural location, as opposed to an in situ treatment where the soil would be left in place.

[0041] As shown in [Fig.l], the installation 1 comprises a generator 6 adapted to produce a fluid, which is both aqueous and shear-thinning, and a circuit 7 in fluid communication with the generator 6. The circuit 7 is arranged to inject the fluid produced by the generator 6 into the ground 2, i.e. into the mound 20.

[0042] The fluid is aqueous in the sense that it is water-based. The fluid is shear-thinning in the sense that its fluidity increases as its flow rate increases. In other words, the dynamic viscosity of the fluid decreases as the shear rate applied to it increases. The non-Newtonian fluid is thus particularly suitable for reaching areas of low permeability in the soil 2 since its viscosity decreases in these areas.

[0043] The fluid here is more specifically a foam. The foam comprises a gas dispersed in an aqueous solution comprising water and a surfactant. The gas includes oxygen, for example in the form of dioxygen. The gas here is air. The foam thus includes air bubbles suspended in the water and surfactant solution.

[0044] The surfactant is a surfactant that lowers the surface tension of water. The surfactant is, for example: sodium dodecyl sulfate (SDS), sodium dodecyl benzenesulfonate, rhamnolipid. The surfactant advantageously allows both the formation of foam by maintaining the bubbles, and at the same time increases the bioavailability of pollutants by facilitating their passage into the liquid phase.

[0045] As shown in [Fig.l], to produce the foam, the generator 6 comprises a first tank 61, a compressor 62, a pump 63 and a porous medium 64.

[0046] The first reservoir 61 contains the water and surfactant solution. The water and surfactant are therefore pre-mixed here. The first reservoir 61 is fluidically connected to the porous medium 64 via the pump 63 which makes it possible to inject the water and surfactant solution into the porous medium 64.

[0047] The compressor 62 is also connected to the porous medium 64 and allows pressurized air to be injected into it. The injected air is here ambient air. Alternatively, the generator does not comprise a compressor but a bottle containing air already under pressure. The generator can then comprise a pressure reducer adapted to control the pressure of the air injected into the porous medium.

[0048] The porous medium 64 has open pores which communicate with each other. The porous medium 64 comprises, for example, a sintered material. The porous medium 64 is, for example, confined in a sealed enclosure delimiting an inlet of the porous medium 64, to which the compressor 62 and the pump 63 are connected, and an outlet of the porous medium 64, through which the foam is expelled. The porous medium 64 is essentially made up of materials with interstice porosity such as silt, clay, sand or gravel.

[0049] In the porous medium 64, the pressurized air mixes with the water and surfactant solution to produce the foam. The size of the pores of the porous medium 64 makes it possible to control the size of the air bubbles suspended in the foam. The air bubbles have, for example, a diameter of between 1 μm and 5 mm. The size of the air bubbles here depends on the size of the pores of the porous medium 64.

[0050] In the example illustrated in [Fig.l], the generator 6 also comprises a second reservoir 65 containing nutrients. The nutrients are here dissolved in an aqueous solution, for example at a concentration of between 100 mg / L and 1000 mg / L. The nutrients are for example selected from the group comprising: carbon, nitrogen, phosphorus, potassium. These nutrients promote the development of bacteria responsible for the biodegradation of the soil 2. In order to include them in the moss, the second reservoir 65 is also connected to the pump 63, such as re shown in [Fig. 1]. Alternatively, the second reservoir can be connected to an independent pump connected to the inlet of the porous medium.

[0051] The pump 63 thus brings to the inlet of the porous medium 64 a mixture solution comprising water, the surfactant and the nutrients.

[0052] The generator 6 comprises two pressure sensors adapted to measure a pressure difference between the outlet and the inlet of the porous medium 64. As shown in [Fig.l], the two pressure sensors thus form a differential pressure sensor 66. The pressure is thus controlled at the inlet and outlet of the porous medium 64. The generator 6 also comprises valves, in particular a first valve 67 at the inlet and a second valve 68 at the outlet of the porous medium 64.

[0053] The first valve 67 at the inlet of the porous medium 64 here makes it possible to control the flow of air, and the pressure of the air, which is injected into the porous medium 64. The flow of the mixing solution is regulated by the pump 63. The first valve 67 is thus adapted to control the pressure of the air. The air pressure at the inlet of the porous medium 64 is for example between 1 bar and 20 bars. Generally speaking, the lower the liquid / gas ratios, the stronger the foam is said to be and the smaller the size of the bubbles.

[0054] The injection pressures and flow rates in the porous medium 64 are for example controlled so that the foam comprises a gaseous fraction accounting for 70% to 95% of the total volume of the foam. In other words, the foam comprises, by volume, between 70% and 95% air. In a complementary manner, the foam comprises a liquid fraction accounting for 5% to 30% of the total volume of the foam. In other words, the foam comprises, by volume, between 5% and 30% of the mixing solution.

[0055] The amount of surfactant in the liquid fraction of the foam is for example between 0.5 mg / L and 200 mg / L.

[0056] The quantity of nutrients in the liquid fraction of the foam is for example between 0.1 g / L and 250 g / L. The ratio between the quantities of carbon, nitrogen, phosphorus and potassium (C / N / P / K) is for example 100 / 10 / 1 / 1.

[0057] The second valve 68 at the outlet of the porous medium 64 makes it possible to control the pressure of the foam at the outlet of the generator 6. As shown in [Fig.l], the generator 6 is connected to the circuit 7 downstream, i.e. at the outlet, of the porous medium 64. The second valve 68 at the outlet of the porous medium 64 thus makes it possible to control the pressure and the flow rate of the foam in the circuit 7.

[0058] The circuit 7 here comprises a plurality of pipes or conduits making it possible to convey the foam produced by the generator 6 into the ground 2.

[0059] In the example illustrated in [Fig.l], the circuit 7 comprises in particular a main pipe 71 fluidly connected to the generator 6 and a plurality of pipes injection pipe 72 each connected to the main pipe 71. The main pipe 71 is for example horizontal. The main pipe 71 comprises an inlet, connected to the generator 6 to receive the foam, and a plurality of outlets, an injection pipe 72 being connected to each outlet.

[0060] As shown in [Fig. 1], the injection pipes 72 extend for example in the vertical direction DI and penetrate into the mound 20 via its top 22. The injection pipes 72 are preferably distributed homogeneously in the mound 20. The injection pipes 72 extend for example over 30% to 70% of the height of the mound 20, the height of the mound 20 being defined here as the distance between the base 21 and the top 22 of the mound 20 in the vertical direction DI. The mound 20 preferably has a height of less than 3 m.

[0061] The injection pipes 72 are for example tubes having on their cylindrical wall small orifices, for example smaller than a radius of the tube. The orifices allow the foam to penetrate into the soil 2 from inside the injection pipes 72. The lower end 73, opposite the main pipe 71, of each injection pipe 72 is here open. Alternatively, the lower end could be closed to increase the pressure at the orifices. Once injected into the mound 20, the foam is initially distributed laterally in the soil 2 (mostly horizontally) and concentrically from each injection pipe 72 due to a pressure gradient and capillary forces. In a second stage, after the foam has collapsed, the water, surfactants and nutrients flow vertically by gravity.

[0062] Of course, various shapes of the circuit for conveying the foam into the mound are conceivable. For example, the circuit may comprise a single injection pipe which extends in different directions into the mound. The injection pipe(s) may be curved or have angles. The injection pipe(s) may have a variable number of orifices of variable size and shape. The installation may also be used to decontaminate several mounds simultaneously. Several main pipes may then be connected to the generator outlet, for example one main pipe per mound.

[0063] The installation 1 also comprises a drain 8 at the base 22 of the mound 20. The drain 8 is arranged to recover residues in liquid form resulting from the flow of the foam in the mound 20 (after the foam has collapsed) and bring them into a tank 9 for subsequent treatment. These residues may in particular contain pollutants in liquid phase, desorbed from the soil 2 by the action of the surfactant.

[0064] [Fig.2] illustrates a process for biological decontamination of soil 2. The process is implemented here by means of installation 1.

[0065] The decontamination process comprises a main step of injecting the foam, that is to say of a rheofluidifying aqueous fluid, in the soil 2.

[0066] As shown in [Fig.l], the method begins more particularly with a first step E1 of forming a mound of the soil 2. The first step E1 may for example comprise an excavation of the soil 2 and the supply of the soil 2 to the decontamination site where the installation 1 is located.

[0067] Before forming a mound, the soil 2 can be mixed with a structuring agent such as wood chips.

[0068] The formation of the mound 20 from the soil 2 is here carried out by stacking the soil 2 on the support 3. Preferably, the drain 8 is prepositioned on the support 3 when the soil 2 is formed into a mound.

[0069] The method continues with a second step E2 of installing the circuit 7 and in particular installing the injection pipes 72 in the mound 20. Once the injection pipes 72 are in place, the mound 20 is covered by the geomembrane 4.

[0070] The method then comprises a third step E3 of forming the foam. The foam is here formed by the generator 6.

[0071] During the third step E3, the conditions for manufacturing the foam, in particular the pressure for injecting the air into the porous medium 64, are controlled so that the air bubbles have a diameter smaller than an average pore size of the sol 2. The average pore size of the sol 2 depends on the granulometry of the sol 2.

[0072] During the third step E3, the surfactant and / or nutrients to be incorporated into the foam can also be selected according to at least one of the following parameters: average pore size of the soil 2, nature of the soil 2 (e.g. organic matter content, permeability, soil surface), harmlessness with respect to the bacteria present in the soil 2, type of pollution (e.g. concentrations and type of pollutants, bioavailability and biodegradability).

[0073] Generally speaking, the size of the foam bubbles, the proportions of air, water and surfactant in the foam, the flow rates and injection pressures of the air and the mixing solution into the porous medium 64, are adapted as a function of at least one of the following parameters: a viscosity to be achieved, a radius of action of the injection pipes 72 (corresponding to a volume of soil 2 located around an injection pipe 72 and which the latter is intended to treat), the average pore size of the soil 2.

[0074] Once the foam has been formed, it is injected into the soil 2 during a fourth step E4 of the process. The foam is therefore injected when the soil 2 is in the form of a mound.

[0075] The foam advantageously makes it possible to supply the soil 2, via a single fluid, with water, nutrients and oxygen useful for the proliferation of bacteria (and therefore for their decontamination work) as well as the surfactant making it possible to make the pollutant more bioavailable. In addition, since the moss is rheofluidifying, these contributions useful for the proliferation of bacteria are made homogeneously in mound 20, despite potential differences in permeability of soil 2.

[0076] In the method, the oxygen is thus injected into the soil 2 solely by means of the foam, i.e. the rheofluidifying aqueous fluid. Indeed, by collapsing in the mound 20 after injection, the bubbles release the air, and therefore oxygen, directly into the soil 2. This makes it possible to simplify the installation 1, for example by dispensing with mound ventilation pipes.

[0077] Remarkably, the foam is injected directly after its formation by the generator 6. In other words, the foam is produced and injected continuously. Thus, the pressure used to generate the foam in the porous medium 64 also allows the injection of the foam into the soil 2. This makes it possible, for example, to do without a specific pump.

[0078] The injection flow rate and the injection pressure of the foam into the soil 2 are determined on the basis of the nature of the soil, and in particular its granulometry. The injection flow rate and the injection pressure are here defined, that is to say measurable, as the flow rate and the pressure of the foam at the outlet of the generator 6. In other words, the injection flow rate and the injection pressure are here defined at the inlet of the main pipe 71, and therefore at the valves 67, 68 and more particularly at the second valve 68.

[0079] The injection rate is for example between 0.2 and 25 m3 / h. The injection rate is here determined as a function of the size of the mound 20 and the permeability of the soil 2.

[0080] The injection pressure of the fluid into the soil 2 is preferably less than 10 bar / m. This reduces the risk of the soil 2 lifting from the support 3.

[0081] The foam may be injected continuously for a predetermined period or periodically, for example at regular time intervals. The foam is for example injected in successive periods of a few tens of minutes of injection interspersed with a few tens of minutes of rest.

[0082] The quantity of foam injected depends in particular on the volume of the soil 2.

[0083] The method then comprises a fifth step E5 of remediation of the soil 2 including a waiting period allowing the action of degradation of pollutants by bacteria. This fifth remediation step E5 lasts for example several days. The fifth step E5 also includes the recovery by drain 8 of liquid residues which are then treated.

[0084] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variant in accordance with the invention. For example, the method can be implemented by any suitable system. The foam could be prefabricated and contained under pressure in a tank. The shear-thinning aqueous fluid could also be a non-oxygenated gel. Such a gel finds particular application in anaerobic biodegradation, i.e., when soil bacteria do not require oxygen.

Claims

Claims

1. Method for biological decontamination of polluted soil (2) in the form of a mound, characterized in that the method comprises a step of injecting a rheofluidifying aqueous fluid into the soil (2).

2. The method of claim 1, wherein the aqueous shear-thinning fluid comprises oxygen.

3. A method according to claim 2, wherein oxygen is injected into the soil (2) solely by means of the shear-thinning aqueous fluid.

4. Method according to one of claims 1 to 3, in which the rheofluidifying aqueous fluid comprises a surfactant.

5. A method according to one of claims 1 to 4, wherein the rheofluidifying aqueous fluid is a foam comprising air bubbles and an aqueous solution which comprises a surfactant, the air bubbles being dispersed in the aqueous solution.

6. The method of claim 5, wherein the air bubbles have a diameter of between 1 pm and 5 mm.

7. A method according to claim 5 or 6, wherein the air bubbles have a diameter smaller than an average pore size of the sol (2).

8. Method according to one of claims 5 to 7, in which the foam comprises by volume between 70% and 95% air.

9. Method according to one of claims 1 to 8, in which the rheofluidifying aqueous fluid comprises nutrients suitable for the proliferation of bacteria present in the soil (2).

10. Method according to one of claims 1 to 9, in which an injection rate of the aqueous rheofluidifying fluid into the soil (2) and an injection pressure of the aqueous rheofluidifying fluid into the soil (2) are determined on the basis of the granulometry of the soil (2), the injection pressure of the fluid into the soil (2) preferably being less than 10 bar / m.

11. Method according to one of claims 1 to 10, further comprising a step of forming the rheofluidifying aqueous fluid, the rheofluidifying aqueous fluid being injected immediately after its formation.

12. Method according to one of claims 1 to 11, in which the soil (2) is polluted by refined petroleum hydrocarbons.

13. Installation (1) for biological decontamination of polluted soil (2) in the form of a mound, the installation comprising: - a generator (6) adapted to produce a rheofluidifying aqueous fluid; - a circuit (7) in fluid communication with the generator (6) and adapted to inject the rheofluidifying aqueous fluid into the soil (2).

14. Installation (1) according to claim 13, in which the rheofluidifying aqueous fluid is a foam and in which the generator (6) comprises a compressor (62), a pump (63) and a porous medium (64), the compressor (62) being adapted to inject pressurized air into the porous medium (64) and the pump (63) being adapted to inject an aqueous solution comprising a surfactant, and preferably nutrients, into the porous medium (64) so ​​as to produce the foam.

15. Installation (1) according to claim 14, in which the porous medium (64) comprises an inlet for receiving the air and the solution and an outlet for expelling the foam, the generator (6) comprising two pressure sensors adapted to determine a pressure difference between the outlet and the inlet of the porous medium (64).

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