FR3019171A1 - DEVICE AND METHOD FOR SANITIZING WASTEWATER - Google Patents

Abstract

The invention relates to a device for cleaning wastewater by lombrifiltration, said device (10) comprising a sewage tank (12), means (14) for introducing wastewater into said sewage tank (12). and means for evacuating (15) the sanitized water from the sanitation tank (12), the sanitizing tank (12) comprising an upper layer of organic material (18), a lower layer of rot-proof material (22) . The lower layer of rotproof material (22) comprises at least a first filtration sub-layer (22a) and a second filtration sub-layer (22b) disposed under the first filtration sub-layer (22a).

Description

TECHNICAL FIELD The present invention relates to the field of sanitation and more particularly relates to a device and a method for cleaning wastewater by lombrifiltration. STATE OF THE ART Waste water from a residential building comprises in a known manner both liquid materials and organic solids that it is necessary to sanitize. When, for example, the said residential building is not connected to the collective sewage network, an autonomous sewerage system is used in a manner known that makes it possible to obtain, at the outlet, sanitized water which can then be discharged into the natural environment. without pollution. Different types of sanitation systems are known such as VSATs, drainage trenches, sand filters and compact filters.

VSATs use bacteria in anaerobic and / or aerobic media to degrade solids from wastewater. Such microstations, however, produce scum sludge and require a lot of maintenance, which is time consuming and expensive.

Drainage trenches and sand filters require, on the one hand, the use of an inlet settling pit that also produces odorous sludge and, on the other hand, a large area of deployment on the ground, which presents disadvantages. In addition, sand can clog the filter, preventing it from working properly. Compact filters work in an aerobic and / or anaerobic environment and can be zeolite (volcanic rock) filters, coconut chip filters, plant filters or lombrifilers. Zeolite filters, coconut chip filters and some planted filters require an inlet settling tank, which again gives off odors, and their maintenance is expensive and time-consuming. In addition, zeolite filters, coconut filter and plant filters are easily clogged at their upper part, which has a significant disadvantage.

In order to partially overcome these disadvantages, planted filters operating without an inlet settling tank or darkening screens that do not emit an odor are used. However, a planted filter requires, on the one hand, a planting surface of the plants three to four times larger than the area necessary for a lumbar filter and, on the other hand, a frequent plant size, which is time consuming and expensive and therefore has significant disadvantages. In addition, plants needing light to live and grow and therefore being in the open air, the effluents remain visible, which has another drawback.

The document FR2985997A1 describes a lombrifiltration system for the purification of waste water of an individual dwelling comprising an injection pump, a sewage tank and a post-treatment module. The wastewater is first conveyed to the injection pump which reduces the size of the solids so as to homogenize the density of the wastewater and then injects it under pressure into the sewage tank via a plurality of sprinklers. The sanitizing tank comprises an upper layer of organic material and a lower layer of mineral material. The top layer of organic matter is composed of wood chips in which earthworms and bacteria are disseminated. The lower layer of mineral material is composed of pozzolan whose average equivalent diameter is between 5 and 20 mm and river pebbles for the evacuation of filtered water from the sanitation tank to the output of the lombrifiltration system. In operation of the sewage tank, the wastewater from the injection pump is sprayed onto the wood chips which filter them so as to retain the majority of the residues of solids so that earthworms and bacteria degrade them, the earthworms mainly acting as mixers of wood chips in order to increase the number of bacteria present in the upper layer of organic matter. A mesh separator whose mesh opening is of the order of 5 mm is arranged between the top layer of organic material and the lower layer of mineral material in order to separate the wood chips from the pozzolan while allowing the evacuation water filtered by the top layer of organic material to the lower layer of mineral material.

However, in such a device, organic solid residues contained in the wastewater and flours resulting from the digestion of earthworms are not sufficiently degraded in the upper layer of organic material and can pass through the mesh separator, pozzolan and the pebbles. This can cause clogging of the sewage tank, especially at the level of the lower layer of mineral material, and therefore requires the use of a water post-treatment module at the outlet of the sewerage tank in order to decant the water filtered and obtain clear water, which is time consuming and tedious and therefore has major drawbacks.

In addition, the liquid materials located at the level of the mesh separator or the lower layer of mineral material can go back by capillarity into the upper layer of organic material. Such a rise humidifies the wood chips at the lower part of the upper layer of organic matter, which densifies them and slows the progress of the earthworms and the digestion of organic solid residues. This has the effect of significantly reducing the efficiency of the system, which has a significant disadvantage. GENERAL PRESENTATION OF THE INVENTION The aim of the present invention is to at least partly solve these disadvantages by proposing a device for cleaning wastewater by lombrifiltration which is at the same time effective, simple and reliable, in particular by allowing a degradation of the materials contained in the wastewater so that it is not necessary to perform a water post-treatment at the outlet of the device.35 For this purpose, the invention relates first of all to a water purification device used by lombrifiltration, said device comprising a sewage tank, means for introducing the wastewater into said sewage tank and means for evacuation of the water purified by the sewerage tank, the sewerage tank comprising: an upper layer of organic material comprising lignocellulosic compounds, in which earthworms and / or bacteria are disseminated, capable of receiving e to the waste of the introduction means and to filter at least partly said wastewater received so as to retain the majority of solids so that said earthworm and / or said bacteria degrade, - a lower layer of rot-proof material in which are disseminated bacteria and which is configured to filter the wastewater filtered by the top layer of organic material so as to retain the solid residues so that said bacteria degrade and discharge the filtered water to the means of evacuation, - a separator to meshes extending between the upper layer of organic material and the lower layer of rotproof material configured to separate the lignocellulosic compounds from the lower layer of rotproof material and allow the passage of water received from the top layer of organic material to the lower layer of imputrescible material, the device As remarkable in that the lower layer of rot-proof material comprises at least a first sub-filter layer and a second sub-filter layer disposed below the first sub-layer filtration.

A plurality of filtration layers of different characteristics makes it possible to filter in different ways the water received from the top layer of organic material so as to avoid clogging of the sanitation tank and therefore the use of a post-treatment module water leaving the sanitation tank.

Advantageously, the lower layer of rotproof material comprises mineral material, inexpensive and easy to use. Preferably, the lower layer of imputrescible material is made of mineral material. According to one aspect of the invention, the first sub-filtration layer comprises first elements whose equivalent diameter is less than 6 mm, preferably less than 5 mm and preferably less than 4 mm. Such first elements may, for example, be grains of sand or balls made of glass or plastic material. Such a first filtration sub-layer may also include volcanic rock.

Preferably, the second filtering sub-layer advantageously comprises second elements whose average equivalent diameter is smaller than the average equivalent diameter of the first elements of the first filtering sub-layer. Such second elements may, for example, be grains of sand or balls of glass or plastic material. The second filtration sub-layer may also include volcanic rock. The first filtering sub-layer makes it possible, in particular, to absorb the clogging while the second filtering sub-layer makes it possible to filter the last residues of solids originating from the upper layer of organic material. Preferably, the equivalent diameter of the first elements of the first filtering sub-layer is between 2 and 4 mm, so as to allow filtering residues of organic solid material whose diameter is greater than or equal to 2 mm.

More preferably, the equivalent diameter of the second elements of the second filtering sub-layer is between 1 and 2.5 mm so as to allow filtering of residual organic solid material of very small dimensions contained in the water passing therethrough.

The vertical succession, from top to bottom, of the first sub-layer of filtration and the second sub-layer of filtration makes it possible to eliminate in two stages almost all or even all the residues of unfiltered organic solid material. the top layer of organic matter. Such a double-filter advantageously makes it possible to separate the filtration from the last residues contained in the water coming from the top layer of organic material, which is notably more effective than if the first filtering sub-layer and the second filtering sub-layer were mixed.

According to a characteristic of the invention, the device comprises element retention means, preferably in the form of a grid or retention tanks, arranged under the second sub-layer of filtration.

According to one aspect of the invention, the lower layer of rotproof material comprises a lower underlayer of rollers configured to evacuate the purified water. Preferably, the device comprises an aeration layer, disposed between the mesh separator and the bottom layer of rotproof material, configured to separate the organic matter top layer from the rotible material bottom layer. Such an aeration layer thus makes it possible to dry the lower part of the upper layer of organic material, in order to prevent the capillary rise of the liquid materials from the lower layer of rot-proof material to the upper layer of organic material through the mesh separator, and to dry the upper part of the lower layer of rot-proof material, which significantly increases the efficiency of the system and makes it possible to obtain at the outlet of the purified water that it is not necessary to treat later and which can therefore be directly rejected in nature. The wastewater treatment device is thus advantageously devoid of post-treatment module and can therefore operate autonomously.

Preferably, the thickness of the aeration layer is greater than or equal to 1 cm. Advantageously, the aeration layer comprises at least 80%, preferably at least 90%, of air.

According to one characteristic of the invention, the aeration layer comprises a honeycomb structure, preferably of ultra-lightweight honeycomb structure (SAUL) type. According to one aspect of the invention, the sanitation device comprises at least a first aeration means connected to the aeration layer in order to significantly improve the efficiency. Such first aeration means may be in the form of a ventilation duct, for example made of polyvinyl chloride (PVC), connecting the aeration layer to the open air. According to another aspect of the invention, the sanitation device comprises at least a second aeration means connected to the lower layer of rot-proof material and / or to a drainage module of the sanitized water in order to significantly improve it. efficiency. Such a second aeration means may be in the form of a ventilation duct, for example made of polyvinyl chloride (PVC), connecting the lower layer of rot-proof material and / or a drainage module of the purified water to the open air. The mesh separator makes it possible to retain both the lignocellulosic compounds and the residues of organic solid matter, contained in the wastewater or resulting from the digestion of the earthworms, whose diameter is greater than that of the mesh so that these residues do not descend in the lower layer of rotproof material. Preferably, the mesh size of the separator is less than or equal to 2 mm. Such a mesh prevents the passage of organic materials whose diameter is greater than 1 mm, which significantly improves the quality of the water leaving the sanitation tank and thus the effectiveness of the device. It is therefore no longer necessary to use means for post-treatment of water leaving the sanitation tank. In addition, such a mesh prevents the clogging of the sanitation tank at the level of the lower layer of imputrescible material.

More preferably, the separator is in the form of a geo-grid made of an imputrescible material, known to those skilled in the art. According to another characteristic of the invention, the device comprises a drainage module configured to drain the sanitized water received from the lower layer of rot-proof material towards the evacuation means. Such a drainage module is preferably disposed, under the lower layer of rotproof material, at the bottom of the sanitation tank. Advantageously, the drainage module comprises an inclined wall, or even doubly inclined.

Preferably, the drainage module comprises at least one drainage duct, preferably connected to the second aeration means. Such a drainage duct may be a duct made of polyvinyl chloride (PVC) and comprising a plurality of openings, known to those skilled in the art. According to one aspect of the invention, the wastewater inlet means comprise a plurality of sprinklers, preferably configured to discharge the wastewater over a major part of the upper surface of the wastewater tank.

According to one characteristic of the invention, the lignocellulosic compounds, which can be easily degraded by compost by earthworms, include, for example, wood chips, wood chips, wood bark or any other suitable carbonaceous material. .

The invention also relates to a wastewater treatment system by lombrifiltration comprising means for injecting wastewater and at least one device as presented above, the injection means being configured to inject the wastewater, preferably to constant volume, in the sanitation device. The invention also relates to a purification process carried out by a device as presented above, said process being remarkable in that it comprises a first filtration step by a first sub-layer of filtration of the lower layer of material imputrescible and a second filtering step by a second filter sub-layer, disposed under the first filter sub-layer, of the lower layer of rotproof material. Advantageously, the process comprises a step of aeration of the lower part of the upper layer of organic material. Preferably, the method further comprises a step of aeration of the upper part of the lower layer of rotproof material.

More preferably, the method further comprises a step of aeration of the lower portion of the lower layer of rotproof material. Other features and advantages of the invention will become apparent from the following description given with reference to the appended figures given by way of non-limiting examples and in which identical references are given to similar objects. DESCRIPTION OF THE FIGURES FIG. 1 illustrates one embodiment of the purification system according to the invention. FIG. 2 is a partially transparent perspective view of one embodiment of a sanitation tank of a sanitizing device according to the invention. FIG. 3 is a perspective view in partial transparency of a shape. embodiment of a sanitizing device according to the invention. Figure 4 is a perspective view in partial transparency of the sanitation vessel of Figure 2 further showing the aeration means. Figure 5 is a schematic sectional representation of the sanitation vessel of the preceding figures.

FIG. 6 illustrates a mode of implementation of the method according to the invention. DETAILED DESCRIPTION OF THE INVENTION Description of an embodiment of the system according to the invention The purification system according to the invention is particularly suitable for treating the wastewater of a residential building comprising, for the most part, organic elements in liquid and solid phase. It is also suitable for treating agricultural and industrial wastewater, particularly agro-food. I) Sanitation System 1 Figure 1 shows an embodiment of a lombrifiltration wastewater treatment system 1 according to the invention. In this example, the system 1 is connected to an apartment building 2 comprising means 3 for generating wastewater. Such wastewater comprises in a known manner both liquids and organic solids. In this example, these generation means 3 wastewater comprises toilet 3a, a washbasin 3b, a bath 3c, a washing machine 3d and a sink 3. In order to collect the wastewater generated by the generation means 3, the building 2 comprises means for recovering the wastewater in the form of evacuation pipes 4.

In order to sanitize the wastewater from the evacuation pipes 4, the sanitation system 1 comprises means for injecting wastewater, connected to the evacuation pipes 4, and a sewage treatment device 10 for the waste water. vermifiltration. 1) Injection means In the example illustrated in FIG. 1, the injection means are in the form of an injection pump 5 configured to receive the wastewater coming from the evacuation lines 4 and to inject them. under pressure, preferably at constant volume, in the purification device 10 via an injection conduit 6. The injection pump 5 allows, by vortex effect or with the aid of a propeller, to reduce the dimensions solids from wastewater at values between 2 and 10 MM. 2) Sanitizer 10 As illustrated in Figures 2 to 5, the sanitation device 10 comprises a sewage tank 12, input means 14 wastewater in said sewerage tank 12 and means of Disposal 15 of the filtered water by the sewerage tank 12. In this example, the sewerage tank 12 is in the form of a parallelepiped shaped tray whose upper face FS is open and which comprises a support base 13 the sanitation tank 12 closing its lower face. The sanitation tank 12 illustrated in Figure 1 is buried in the ground S, but it goes without saying that it could be above ground in another embodiment of the system according to the invention.

The inlet means 14 for the wastewater in the sewerage tank 12 are configured to receive, from the injection pump 5, via the duct 6, the crushed wastewater and to discharge it into the sewerage tank 12. For this purpose, with reference to FIG. 3, the inlet means 14 for the wastewater are in the form of a plurality of watering pipes 14a and sprinklers 14b arranged in a network above the upper face. FS of the sewage tank 12. Preferably, the sprinklers 14b are arranged to disperse the wastewater on a surface corresponding to that of the open upper face FS of the sewage tank 12. In this example, the device 10 comprises sixteen sprinklers equi-distributed in a space 16 located at the upper part of the sewerage tank 12. In this example, the evacuation means 15 are in the form of a duct. evacuation 15 configured for discharging the filtered water through the sanitation tank 12, for example directly into the soil or into a storage tank. Of course, the shape and dimensions of the input means 14 and the evacuation means 15 may be different in other embodiments of the device 10.

The sewerage tank 12 comprises a plurality of layers of different types of matter distributed vertically over the height of the sewerage tank 12. In this example, with reference to FIGS. 4 and 5, the sewerage tank 12 comprises upside down, a space or layer of air 16, an upper layer of organic material 18, a mesh separator 19, a ventilation layer 20, a bottom layer of rotproof material 22 and a drainage module (described below). after). The wastewater is dispersed by the sprinklers 14b through the air layer 16 on the top layer of organic material 18 to be filtered.

To this end, the top layer of organic material 18 comprises lignocellulosic compounds, preferably of the woodchip type, in which earthworms and bacteria are disseminated and can develop. The lignocellulosic compounds can of course be in other forms or materials, mixed or not. In this example, the wood chips are composed of a mixture of oak (2/3) and poplar (1/3). It goes without saying that any type of chips and / or suitable mixture can be used in the context of the present invention. Most of the bacteria can degrade the solid particles in the crushed wastewater.

Earthworms allow, to a lesser extent, to degrade the solids contained in the wastewater and especially allow to mix and aerate the wood chips so as to increase the number of bacteria present in the top layer of organic matter, improving thus the effectiveness of the sanitation device 10.

Preferably, the thickness of the upper layer of organic material 18 is greater than 40 cm. The lower layer of rotproof material 22 can support the upper layers and evacuate water it filters to the drainage module. To do this, in this example, the lower layer of rotproof material 22 comprises a plurality of sub-layers of mineral materials, in which there are present bacteria for the degradation of organic matter residues of the wastewater, among which: a first sub filter layer 22a consisting of sand grains, a second filter sub-layer 22b disposed under the first filter sub-layer 22a, also constituted by grains of sand, sand-holding means in this example being In a variant, the sand retention means may be in the form of a tray or other suitable means. Preferably, the equivalent diameter of the sand grains of the first filtration sub-layer 22a is greater than the equivalent diameter of the sand grains of the second filtration sub-layer 22b. More preferably, the equivalent diameter of the sand grains of the first filtration sub-layer 22a is between 2 and 4 mm, and the equivalent diameter of the sand grains of the second filtration sub-layer 22b is between 1 and 2.5 mm.

By the terms "equivalent diameter" is meant the size of the grains, that is to say the diameter of the sphere which would behave identically during a grading zero grading operation.

The first filtration sub-layer 22a makes it possible, in particular, to absorb clogging, while the second filtration sub-layer 22b makes it possible to filter almost all, or even all, of the residues of solids contained in the filtered waters coming from the top layer of organic matter.

The sand retention grid 22c is arranged under the second filtration sub-layer 22b makes it possible to retain the sand of the second filtration sub-layer 22b while allowing the filtered water to pass through the said second filtration sub-layer 22b.

Preferably, the thickness of the lower layer of rotproof material 22 is greater than 30 cm. For example, the thickness of each of the first filter sub-layer 22a, the second filter sub-layer 22b and the underlayer of rollers 22d may be greater than 10 cm.

According to the invention, an aeration layer 20 is disposed between the upper layer of organic material 18 and the lower layer of rotproof material 22. In this example, the aeration layer 20 is advantageously in the form of a structure ultralight alveolar (SAUL) whose thickness is between 5 and 40 cm and whose ratio of the volume of air to the total volume of the layer is between 80% and 99%. The structure of the aeration layer 20 is made of a rot-proof material and resistant to the passage of wastewater. In order to improve the efficiency of the aeration of the lower part of the upper layer of organic material 18 and of the upper part of the lower layer of rotproof material 22, and therefore the efficiency of the device 10, the device 10 comprises , as illustrated in FIG. 4, first aeration means in the form of two first ventilation ducts 23, or chimneys, connecting the aeration layer 20 to the open air of the air layer 16 .

A mesh separator 19, for example of geo-grid type, is disposed between the upper layer of organic material 18 and the aeration layer 20 so as to retain the wood chips.

The spacing value of the mesh of the separator 19 is small, of the order of 1 mm. The use of such a mesh separator 19 is made possible by the presence of the aeration layer 20 which improves the efficiency of the degradation of solid matter residues by the top layer of organic material so that the equivalent diameter most of the solid particles reaching the mesh separator 19 is less than 1 mm. The drainage module allows the collection by gravity of the filtered water by the different layers of material disposed in the sewerage tank 12.

The drainage module comprises an inclined wall 26a and drainage ducts 26b for discharging the filtered water towards the discharge duct 15. The drainage ducts 26b may be in the form of tubes, for example made of polyvinyl chloride. vinyl (PVC), in which are drilled openings, known to those skilled in the art, for collecting the purified water.

In order to improve the efficiency of the aeration of the lower part of the lower layer of rotproof material 22, that is to say of the underlayer of rollers 22d, and / or of the drainage module, and therefore the efficiency of the device 10, the device 10 comprises, as illustrated in Figure 4, second aeration means in the form of two second ventilation ducts 24, or chimneys, connecting, in this example, the sub 22d and the drainage module to the outside air of the air layer 16. The sanitation device 10 may further comprise a security module including a sanitation tank which is connected bypass on the wastewater supply circuit charged with organic matter. The sanitizing device 10 may also comprise cooling means (not shown) of the ground waste water sprayed in the sewerage tank 12 which may for example be in the form of a coil heat exchanger. The sanitizer 10 may also include means for controlling the temperature of the top layer of organic material to allow control of the life and development of earthworms.

Moreover, the sewerage system according to the invention may further comprise a tank for retaining the purified water at the outlet of the device 10 and / or a pump for lifting sanitary water, also disposed at the outlet of the device 10, in particular for bring the purified water to the surface when the device 10 is at least partially buried. Il) Implementation In operation of the sanitation device 10, the wastewater generated by the generating means 3 is conveyed via the pipes 4 to the injection pump 5 in a step El. The injection pump 5 the wastewater is then injected into the inlet means 14 in a step E2, which makes it possible to reduce the dimensions of the particles 30 contained in said wastewater, preferably to values of less than 10 mm. The wastewater is guided by the watering pipes 14a to the sprinklers 14b which spray, in a step E3, in the space 16 of the sewerage tank 12, over most of the upper surface of the layer Higher level of organic matter 18.

The wastewater thus dispersed passes through the upper layer of organic material 18 by gravity. The organic solids they contain are then deposited in large part on the wood chips where they will be degraded, in a step E4, by the bacteria present in the upper layer of organic matter 18. The earthworms present in the upper layer of These organic materials 18 also digest these deposited organic solids but also lignocellulosic particles of the top layer of organic matter 18 which they stir simultaneously, thus improving the development of the bacteria in the upper layer of organic matter 18 and thus the overall efficiency of the organic material. Device 1. The wastewater filtered by the upper layer of organic matter 18 reaches then passes through the mesh separator 19, then the aeration layer 20, still by gravity, in a step E5. The aeration layer 20 thus makes it possible, via the first ventilation ducts 23, to carry out a step E6 of aeration of the lower part of the upper layer of organic material 18 and a step E7 of aeration of the upper part of the the lower layer of rotproof material 22, in this case the upper part of the first sub-surface 22a of filtration. Wastewater that has passed through the aeration layer may still contain residual organic matter particles. They are therefore advantageously filtered by the first filtration sub-layer 22a in a step E8 and then by the second filtration sub-layer 22b in a step E9 in order to retain the last residual organic particles that they contain. The thus sanitized waters then reach the retention grid 22c and the layer of rollers 22d which they pass through in a step El ° while a step El 1 allows the aeration, via the second aeration ducts 23b, of the sub -roll of rollers 22d, inclined wall 26a and drainage ducts 26b. The inclined wall 26a and the drainage ducts 26b then drain the purified water 35 in a step E1 2 to the evacuation conduit 15 where they can, in a step E13, be discharged directly into the environment without pollution or collected by a system. or a collection device (not shown) such as, for example, a holding tank.

Note that with the sanitation device according to the invention, it is not necessary to collect the flours from the digestion of earthworms. In addition, the aeration layer 19 significantly increases the effectiveness of the sanitizer 10 since it allows aeration of the top layer of organic material 18 and thus the development of bacteria in the wood chips. Similarly, the air duct or ducts significantly increase the efficiency of the sanitation device 10 since they allow a better flow of the sanitized water. Finally, the device and the system according to the invention can be of small dimensions and therefore compact. They are also easy to install, are made from inexpensive materials and require little maintenance. 20

Claims (10)

REVENDICATIONS1. Apparatus for cleaning wastewater by lombrifiltration, said device (10) comprising a sewage tank (12), means (14) for introducing wastewater into said sewage tank (12) and means for evacuation (15) of the sanitized water by the sewerage tank (12), the sewerage tank (12) comprising: - an upper layer of organic material (18) comprising lignocellulosic compounds, in which earthworms are disseminated and / or bacteria, capable of receiving wastewater from the introduction means (14) and at least partly filtering said wastewater received so as to retain the majority of solids so that said earthworms and / or said bacteria degrade, a lower layer of rotproof material (22) in which bacteria are dispersed and which is configured to filter the wastewater filtered by the top layer of organic material (18) so as to retain removing the solids residues so that said bacteria degrade them and discharge the filtered water to the evacuation means (15); - a mesh separator (19) extending between the upper layer of organic material (18) and the lower layer of rotproof material (22) configured to separate the lignocellulosic compounds from the bottom layer of rotproof material (22) and allow the passage of water received from the top layer of organic material (18) to the bottom layer of rotproof material (22); ), the device being characterized in that the lower layer of rotproof material (22) comprises at least a first filter sub-layer (22a) and a second filter sub-layer (22b) disposed under the first underlayer filtration (22a). 2. Device according to claim 1, characterized in that the lower layer of imputrescible material (22) comprises mineral material. 3. Device according to one of the preceding claims, characterized in that the first sub-filter layer (22a) comprises first elements whose equivalent diameter is less than 6 mm, preferably less than 4 mm. 4. Device according to the preceding claim, characterized in that the equivalent diameter of the first elements of the first filter sub-layer (22a) is between 2 and 4 mm. 5. Device according to one of the preceding claims 3 and 4, characterized in that the second filter sub-layer (22b) advantageously comprises second elements whose average equivalent diameter is smaller than the average equivalent diameter of the first elements of the first filtration sub-layer (22a). 6. Device according to the preceding claim, characterized in that the equivalent diameter of the second elements of the second filter sub-layer (22b) is between 1 and 2.5 mm. 7. Device according to one of claims 3 to 6, characterized in that the first elements and / or the second elements are grains of sand or balls of glass or plastic material. 8. Device according to one of the preceding claims, characterized in that the first filter sub-layer (22a) and / or the second filter sub-layer (22b) comprises volcanic rock. 9. Device according to one of the preceding claims, characterized in that it comprises means for retaining elements, preferably in the form of a grid (22c) or retention tanks, arranged under the second filtration sub-layer (22b). 10. A method of remediation implemented by a device (10) according to one of the preceding claims, said method being characterized in that it comprises a first step (E8) of filtration by a first sub-layer filtration ( 22a) of the lower layer of rotproof material (22) and a second filtration step (E9) by a second filter sub-layer (22b) disposed under the first filter sub-layer (22a) of the lower layer of rotproof material (22).