EP3615479A1

EP3615479A1 - Artificial wetland sized for removing pollutants

Info

Publication number: EP3615479A1
Application number: EP18717095.6A
Authority: EP
Inventors: Chrystelle Langlais; Ywann PENRU; Ludovic PERRIDY
Original assignee: Suez Groupe SAS
Current assignee: Suez International SAS
Priority date: 2017-04-28
Filing date: 2018-04-19
Publication date: 2020-03-04
Also published as: FR3065720A1; CN110678421A; FR3065720B1; WO2018197329A1

Abstract

The present invention relates to an artificial wetland for removing one or more pollutants from an effluent comprising at least two compartments, wherein the dimensions of the compartments make it possible to promote various reactions. The synergy of the reactions that occur in the various compartments makes it possible to improve the purifying capacity of an artificial wetland according to the invention compared with an artificial wetland of the prior art. The dimensions of the wetlands according to the invention also make it possible to reach a target rate for removing pollutants from the effluent, with the smallest possible site coverage. The present invention also relates to a method for defining such an artificial wetland.

Description

ARTIFICIAL WET ZONE DIMENSIONED FOR ELIMINATION

OF POLLUTANTS

FIELD OF THE INVENTION

The present invention relates to the field of wetlands for the removal of pollutants. More specifically, the present invention relates to the sizing of wet areas to optimize the purifying capabilities thereof.

STATE OF THE ART PREVIOUS

It is known to use raw sewage treatment systems, from urban effluents and / or industrial to limit the impact of effluents of human activities on ecosystems.

Several techniques can intensify the purification capacity of wastewater treatment systems, and thus reduce their footprint for a given purification capacity. For example, certain techniques make it possible to intensify the purifying process in the liquid phase of these structures by a forced supply of oxygen. For example, patent application US2016100083 describes devices for transferring oxygen into the lagoons of a wastewater treatment system. The patent application CN2051 15138 describes an aeration device advantageously using solar energy.

[0004] Certain solutions make it possible to improve the purification performance of wastewater treatment systems in particular contexts. For example, patent application US2016167994 describes the addition of aquatic microorganisms (bio-increase), in particular the addition of microalgae for the aqueous elimination of metals and sulphates from a mining effluent. This solution makes it possible to improve the treatment efficiency in the case of wastewater treatment systems dedicated to the treatment of an industrial effluent (and thus having a low natural biodiversity).

The patent application US2016200608 discloses recirculation of effluents in a wastewater treatment system having at least two compartments, in order to avoid a drop in the purification efficiency of the zone. wet in case of significant changes in temperature during the seasons.

[0006] So-called root ecosystems (or rhizospheres) of plant macro are also known and advantageously exploited to eliminate pollutants of water and effluents in general.

For example, the patent application WO201 1 157406 describes the implementation of several compartments having root ecosystems arranged in series. The patent application WO2011157406 describes the nature of the substrate to maintain a good permeability of said substrate for, in particular, the elimination of organochlorine compounds.

[0008] The patent application WO2006030164 describes a method for managing compartments planted with plant macro and describes in particular the alternation of feed and non-feed phases of the compartments to promote the alternation of aerobic and anoxic phases or anaerobic in the artificial wetland.

The patent application WO2006128994, filed by the applicant of the present application, describes a combination of conventional purification devices for the removal of carbon and nitrogen pollution, with compartments consisting of filter beds planted with reeds.

In general, these devices are intended to promote a particular purifying process. These techniques have important limitations for the treatment of modern effluents. Indeed, if these devices allow a good elimination of macro pollutants, the use of a single treatment process may have limited effectiveness for many organic pollutants or minerals. For example, these wetlands may have limited efficacy for the treatment of micropollutants such as pharmaceuticals.

Thus, these devices, if they have certain improvements, can achieve satisfactory sanitation efficiency at the cost of a significant footprint, of the order of 10 to 20 m ² / equivalent inhabitants depending on the nature of the effluent and the treatment objectives. This footprint remains too large to allow the installation of artificial wetlands in areas where land is expensive and / or not available.

The applicant was interested in the purification capacity of wetlands. Wetlands allow elimination of micropollutants rainwater. Wetlands can also be used to remove micropollutants from urban or industrial effluents after pre-treatment, in order to reduce the impact of the effluent on the receiving environment, for example.

The simplest wetlands consist of one or more lagoons, natural or man-made, through which / transits the effluent. These devices consist preferentially of a large water surface, an average water height of 1 to 1, 5 m, a low flow rate, a long residence time (from several days to several weeks). These wetlands allow the removal of suspended solids that decant, the disinfection of effluents through the penetration into the water column natural UV rays of the sun, and the elimination of organic pollution, nitrogen and phosphorus. These wetlands can generate several degradation mechanisms, including photo-degradation, adsorption (on a substrate, on plants, or suspended solids for example), biodegradation, or assimilation by plants if plants are present in the wetland.

If the effectiveness of these wetlands is recognized, they have the disadvantage of having a significant footprint: in fact, these wet areas are characterized by a high residence time, and therefore, for a given flow, a large volume. The average water height of these devices being limited, the ground surface of these areas is therefore very important. This may limit the possibility of wetland development in areas where land is scarce and / or expensive.

There is therefore a need for an artificial wetland to achieve a target elimination rate of one or more pollutants of an effluent, while having a footprint as low as possible.

SUMMARY OF THE INVENTION

For this purpose, the invention describes an artificial wet zone for the purification of liquid effluents from at least one target pollutant, said artificial wetland comprising at least a first compartment and a second compartment supplied with an effluent of said first compartment. compartment, said artificial wetland being characterized in that: said at least a first compartment has an average water depth of between 5 and 70 cm; said at least one second compartment has a mean water height of between 70 and 150 cm.

The low height, between 5 and 70 cm, of the at least one first compartment promotes plant growth and / or adsorption in the at least a first compartment. The higher height of the at least one second compartment, between 70 and 150 cm, makes it possible to limit the growth of the plants, and to promote photodegradation and / or decantation in the at least one second compartment. Decantation, in the at least a second compartment, of suspended matter and / or plants on which the pollutant has adsorbed in the at least one first compartment, makes it possible to increase the effectiveness of the artificial wetland. The synergy of processes occurring in the at least one first and the at least one second compartment thus achieves high pollutant removal rates, with a low footprint.

Advantageously, the volume of said at least one first compartment is chosen to allow a first residence time of the liquid effluents in said at least one first compartment according to a flow rate entering said first compartment; the volume of the second compartment is selected to allow a second residence time of the liquid effluents in said second compartment, according to an inflow of said second compartment.

This feature ensures that the compartments of the artificial wetland have a sufficient volume to ensure the duration of the reactions taking place in each of the compartments, while limiting the footprint of the artificial wetland.

Advantageously, the first and second residence time are chosen so as to achieve a minimum elimination rate of the at least one target pollutant at the outlet of the second compartment.

This feature ensures the purification performance of the artificial wetland, while limiting its size.

Advantageously, said at least one first compartment has a perimeter in linear meters greater than or equal to one-tenth of its area in square meters, less than or equal to one-sixth of its area in square meters, and preferably equal to 15% its area in square meters; said at least a first compartment has a mean water level of between 10 and 50 cm, and preferably equal to 20 cm.

This feature promotes plant growth and adsorption to plants in the at least a first compartment.

Advantageously, the volume of the first compartment is chosen to allow a residence time of liquid effluents in the said at least a first compartment between 0.5 and 3 days depending on an inflow of said at least a first compartment .

This characteristic allows to adapt the residence time, and therefore the size of the at least a first compartment depending on the importance of adsorption for the removal of the at least one target pollutant: if the adsorption is not important with respect to the at least one target pollutant, a very short residence time (for example of 0.5 days) allows nevertheless to remove a little sludge and suspended matter; if the adsorption is important to eliminate the at least one target pollutant, a longer residence time (up to 3 days) makes it possible to guarantee a desired elimination rate of the target pollutant.

Advantageously, said at least one first compartment has a perimeter in linear meters greater than or equal to 5% of its area in square meters less than or equal to 55% of its area in square meters, and preferably equal to half of its area in square meters; said at least one first compartment has an average water height of between 10 and 70 cm, and preferably equal to 50 cm.

This feature makes it possible to have at least one first compartment stretched in length, or forming meanders, while having a small length. This makes it possible to have an important contact with the substrate, and to promote the adsorption of the pollutant to the substrate or to the suspended matter.

Advantageously, the volume of the at least a first compartment is configured to allow a residence time of the liquid effluents in the said at least one first compartment is between 1 and 2 days, depending on an inflow of said at least one first compartment.

This characteristic allows to adapt the residence time, and therefore the size of the at least a first compartment depending on the importance of the adsorption for the elimination of the at least one target pollutant: if the adsorption is not important with respect to the at least one target pollutant, a time of short stay (eg 1 day) allows to slow the flow between two compartments; if the adsorption is important to eliminate the at least one target pollutant, a longer residence time (up to 2 days) can guarantee a desired rate of elimination of the target pollutant.

[0030] Advantageously, said at least one second compartment has a perimeter in linear meters less than or equal to a quarter of its area in square meters, and preferably equal to 17% of its area in square meters; said at least one second compartment has an average water height greater than or equal to 70 cm and less than or equal to 150 cm.

This feature promotes photodegradation and settling in the at least one second compartment.

Advantageously, the volume of the second compartment is configured to allow a residence time of the liquid effluents in the said at least a second compartment between 1 and 5 days depending on an inflow of said first compartment.

This feature ensures a sufficient level of pollutant removal in the at least a second compartment, while limiting the area occupied by the at least a second compartment.

Advantageously, at least one of said at least a first compartment and second compartment is equipped with valleys over a length greater than or equal to half of its maximum width.

This characteristic makes it possible to improve the distribution of the flow entering the compartment.

[0036] Advantageously, said at least one second compartment comprises at least one shoal area.

This feature helps to promote the emergence of macrophytes in the second compartment.

Advantageously, said at least one shallow zone has a decreasing width of the bank towards the center of said at least one second compartment.

This feature allows to promote a higher concentration of macrophytes near the banks of the at least a second compartment. Advantageously, the artificial wetland is connected at the output to a media filtering device comprising at least two parallel works that can be powered alternately.

This characteristic allows to retain suspended matter, particles and plant debris.

[0042] Advantageously, said filtering device is planted with reeds.

This characteristic makes it possible to maintain the permeability of the banks of the filtering material.

The invention also describes a method for developing an artificial wetland for the purification of liquid effluents from at least one target pollutant, said method comprising: the definition of at least a first compartment, having a average water level between 5 and 70 cm; the definition of at least second compartment fed by an effluent of said first compartment, having an average water height of between 70 and 150 cm.

Advantageously, the management method comprises, for at least one compartment: a definition of a residence time in said at least one compartment, according to at least one type of reaction to take place in the at least one compartment; minus one compartment, and a target elimination rate of the at least one target pollutant; calculating a volume of the at least one compartment according to said residence time, and an inflow of effluent into said at least one compartment; calculating a surface of the at least one compartment according to said volume, and an average height of the at least one compartment selected according to the at least one type of reaction; a calculation of a perimeter of the at least one compartment according to said surface, and a ratio between the perimeter in linear meters of the at least one compartment, and the area of the at least one compartment, said ratio being chosen according to the at least one type of reaction.

This method allows effective design of an artificial wetland, to ensure a rate of elimination of a target pollutant, while limiting the footprint of the artificial wetland, and adapting to the land available.

The invention also describes a method for the purification of liquid effluents from at least one target pollutant by an artificial wetland, said method comprising successively: the treatment of the effluents with at least one first compartment of the artificial wetland, said at least one first compartment having a mean water height of between 5 and 70 cm; the treatment of the effluents by at least a second compartment of the artificial wetland, said at least one second compartment having an average water height of between 70 and 150 cm.

This method allows an effective treatment of an effluent, promoting the treatment of the effluent by compartments favoring reactions having synergies between them.

The invention optimizes purification processes taking place in an artificial wetland.

The invention makes it possible to guarantee an elimination rate of a target pollutant by an artificial wetland.

The invention reduces the footprint of wet areas.

The invention is applicable to many purification processes.

The invention eliminates many types of target pollutants.

The invention improves the biodiversity of wetlands.

The invention is usable with a large number of plants, including plants endemic to the region in which the artificial wetland is installed.

The invention allows different forms of compartments.

The invention is applicable to several arrangements of compartments, which allows to adapt the artificial wetland to land available.

LIST OF FIGURES

Other characteristics will become apparent on reading the detailed description given by way of example and not limiting thereafter with reference to appended drawings which represent:

FIG. 1, a first schematic example of an artificial wetland according to the invention;

FIG. 2, a second schematic example of an artificial wetland according to the invention;

FIG. 3, an example of an aerial view of a simulated artificial wetland according to the invention; FIG. 4, an example of an aerial view of a compartment of a simulated artificial wetland according to the invention;

FIG. 5, a first example of a method for dimensioning an artificial wetland according to the invention;

FIG. 6, a second example of a method for dimensioning an artificial wetland according to the invention.

DETAILED DESCRIPTION [0059] FIG. 1 represents a first schematic example of an artificial wetland according to the invention.

The artificial wetland 100 makes it possible to treat liquids, for example treated wastewater of residential and / or industrial origin. The artificial wetland can also treat polluted rainwater, or any other type of aqueous effluent, for example a mixed effluent composed of urban wastewater and rainwater. The artificial wetland 100 may, for example, treat the effluents of a purification plant, an urban community or an industrial site, or be located downstream of a watercourse and / or a pond rainwater collector.

The artificial wetland 100 more specifically allows the purification of at least one target pollutant of the effluent. The wet zones according to the invention generally make it possible to treat a large number of pollutants. According to the various embodiments of the invention wet areas, the artificial wetland 100 can be sized for the treatment of a single pollutant, or for the simultaneous treatment of several pollutants.

The artificial wetland comprises a first compartment 1 10, and a second compartment 120. The second compartment 120 is located downstream of the first compartment 1 10, and treats the effluents thereof. The effluents are therefore first treated by the first compartment 1 10, then by the second compartment 120.

The compartments of wet areas according to the invention are remarkable for their average heights, which allow to promote different purification mechanisms according to the compartments. The average height of the compartments may, in the context of the present application, be designated either height or water level. The average water level is the average of the water depths of a compartment.

The first compartment 1 10 has an average water height of between 5 and 70 cm. This height of water makes it possible to promote plant growth and / or adsorption in the at least one first compartment.

The second compartment has an average water height of between 70 and 150 cm. The higher height of the at least one second compartment makes it possible to limit the growth of the plants, and to promote photodegradation and / or decantation.

Decanting, in the second compartment, suspended materials and / or plants on which adsorbed the pollutant in the at least a first compartment, increases the efficiency of the artificial wetland. The combination of these processes makes it possible to achieve high pollutant removal rates with a low footprint.

The artificial wetland 100 is characterized by an inflow, depending on the source of the effluent to be treated. The inflow is generally predictable, depending on the source of the effluent to be treated. For example, if the artificial wetland is positioned at the outlet of a wastewater treatment plant of an urban community, it is possible to provide an inflow of the artificial wetland to be sized according to the number of inhabitants of the urban area. the urban community. Similarly, it is possible to provide a target input flow rate for an artificial wetland to treat the effluents of an industrial zone according to the output flow of the industrial zone. According to different embodiments of the invention, the inflow can be a medium flow, or a maximum flow.

In one set of embodiments of the invention, it is desirable to ensure that the effluent remains sufficiently long in the first compartment 1 10 and the second compartment 120, to ensure that the reaction time is sufficient.

For this purpose, the volume of the first compartment 1 10 may be chosen to allow a first residence time liquid effluents in the first compartment 1 10. The volume of the first compartment 1 10 can be defined by multiplying the time of target stay by the inward flow of the first compartment 1 10. Similarly, the volume of the second compartment 120 can be chosen to allow a second residence time of the liquid effluents in the second compartment 120. The volume of the second compartment 120 can thus be defined by multiplying the target residence time by the inflow of the second compartment 120

In one set of embodiments of the invention, the volumes of the first compartment 1 10 and the second compartment 120 and ensure the desired duration of reactions taking place in each of the compartments, while limiting the volume of the compartments , and therefore the footprint of the artificial wetland.

According to various embodiments of the invention, the first and the second residence time are chosen so as to achieve a minimum elimination rate of the at least one target pollutant at the outlet of the second compartment. It is thus possible to ensure the purification performance of the artificial wetland, while limiting its footprint.

According to various embodiments of the invention, the first and second residence times may be chosen in different ways. For example, field data compendia can be used to determine, for a given reaction, a rate of removal of the pollutant by the reaction. The residence times may also have been obtained by studying the kinetics of existing wetland compartments and / or by laboratory studies of the kinetics of reactions occurring in mini-basins.

In one set of embodiments of the invention, the artificial wetland is intended to obtain a target elimination rate of several target pollutants. If the residence times required for the elimination of different pollutants are different, the volumes of the first compartment 1 10 and the second compartment 120 can be defined according to the maximum residence time for each compartment. For example, if a target elimination rate of a first pollutant is reached with a residence time of 2 days in the first compartment 1 10, and a target elimination rate of a second pollutant with a residence time of 3 days in the first compartment 1 10, the volume of the first compartment 1 10 can be defined to ensure a residence time of 3 days to ensure the target elimination rate of the two pollutants. Conversely, if a target elimination rate of a first pollutant is reached with a residence time of 5 days in the second compartment 120, and a target elimination rate of the second pollutant with a residence time of 2 days in the second compartment 120, the volume of the second compartment can be sized to ensure a residence time of 5 days to achieve the target elimination rate of the two pollutants. Thus, the choice of the volume of the two compartments makes it possible to guarantee that the target elimination rate of each of the two pollutants is reached or exceeded by the artificial wetland.

In one set of embodiments of the invention, the dimensions of the first compartment 1 10 can further promote the growth of plants, for example to form a reed bed. This condition is fulfilled, for example, when the first compartment has:

an average water level of between 10 and 50 cm, for example equal to 20 cm;

- a perimeter in linear meters greater than or equal to one-tenth of its area in square meters, less than or equal to one-sixth of its area in square meters, for example equal to 15% of its area in square meters;

These dimensions allow the first compartment 1 10 to have at the same time a low water height, and an elongated shape. The first compartment 1 10 then greatly promotes the growth of plants, and the adsorption of pollutants thereon. In one set of embodiments of the invention, the volume of this first compartment may be selected to guarantee a residence time of the effluents of between 0.5 and 3 days depending on the flow rate entering the compartment. This residence time allows in most cases to ensure a sufficient level of adsorption in a first compartment type reed, while limiting the footprint of the at least a first compartment.

In one set of embodiments of the invention, the dimensions of the first compartment 1 10 are such that the first compartment 1 10 has:

a perimeter in linear meters greater than or equal to 5% of its area in square meters less than or equal to 55% of its area in square meters, preferably said at least one first compartment has a perimeter in linear meters greater than or equal to 16% of its area in square meters, less than or equal to 55% of its area in square meters, for example equal to half of its area in square meters;

- An average water level of between 10 and 70 cm, for example equal to 50 cm.

These dimensions make it possible to have a first compartment 1 stretched in length, or forming meanders, while having a small length. This makes it possible to have an important contact with the substrate, and to promote the adsorption of the pollutant to the substrate or to the suspended matter. This first compartment 1 10 may have a volume allowing a residence time of between 1 and 2 days. This residence time makes it possible, in most cases, to guarantee a sufficient level of adsorption in a first meander-type compartment 1 10, while limiting the footprint of the first compartment 1 10.

In one set of embodiments of the invention, the dimensions of the second compartment 120 are such that:

- The second compartment 120 has a perimeter in linear meters less than or equal to a quarter of its area in square meters, for example equal to 17% of its area in square meters;

- The average water level is greater than or equal to 70 cm and less than or equal to 150 cm.

These dimensions make it possible to define a second compartment 120 of the basin type to promote photodegradation and decantation. In particular, a height of at least 70 cm makes it possible to prevent the growth of helophyte type plants in the compartment in order to promote photodegradation; a height up to 150 cm allows a sufficient amount of photons to reach the bottom of the second compartment 120. Thus, if the second compartment 120 is as deep, the photodegradation will take place throughout the second compartment. This makes it possible to have a second compartment 120 having a given volume, with the smallest possible area, and thus to promote photodegradation with a footprint as low as possible.

In one set of embodiments of the invention, the volume of the second compartment allows a residence time of the liquid effluents in a second compartment 120 between 1 and 5 days depending an inflow of said second compartment 120. This residence time allows, in most cases, to ensure a sufficient level of photodegradation and settling in the second compartment 120 lagoon type, while limiting the footprint of the second compartment 120.

The possible dimensions of the first compartment 1 10 and the second compartment 120 can define a set of compartment shapes. Thus, if these dimensions make it possible to ensure a level of elimination of the target pollutant (s), the shape of the first compartment 1 10 and the shape of the second compartment 120 can be defined to adapt to external constraints, for example for adapt to the land available where the area is to be located.

[0081] Figure 2 shows a second schematic example of artificial wetland according to the invention.

The artificial wetland 200 is intended for use similar to that of the artificial wetland 100 described with reference to Figure 1.

The artificial wetland 200 comprises a reed-like compartment 210 similar to the first compartment 1 10 (with a perimeter in linear meters greater than or equal to one-tenth of its area in square meters, less than or equal to one-sixth of its area in square meters), two basin type compartments 220 and 221 similar to the second compartment 120, a meander type compartment 21 1 similar to the first compartment 1 10 (with a perimeter in linear meters greater than or equal to 5% of its area in meters squares less than or equal to 55% of its area in square meters, for example equal to half of its area in square meters), and a third basin type compartment 222 similar to the second compartment 120.

The artificial wet zone 200 thus allows an alternation of compartments favoring different reactions, with in particular, in the order of flow of the effluent:

- The compartment 210 of the reed type favoring the growth of plants and adsorption to plants;

Basin-type compartments 220 and 221, with the effluent from compartment 210, favoring photodegradation and decantation; The meander-type compartment 21 1, with the effluent from the compartments 220 and 221, promoting contact with the substrate, and the adsorption of the pollutant to the substrate or to the suspended matter;

- The basin-type compartment 222, effluent compartment 21 1, promoting photodegradation and decantation.

Similarly to the artificial wetland 100, it is possible to define the volumes of the compartments of the artificial wetland 200 so as to ensure that the residence time of the liquid effluent is sufficient in the compartments favoring a given reaction. For example, if a residence time of 3 days in one or more compartments promoting adsorption is desired, the volumes of the compartments can be defined for example such that:

the residence time in compartment 210 is 1 day, and that in compartment 21 1 is 2 days;

or the residence time in compartment 210 is 1.5 days, and that in compartment 21 1 is 1.5 days.

Thus, the design of the artificial wetland 200 makes it possible to modulate the residence times, and therefore the volumes and the surfaces, of the different compartments so as to ensure that an overall residence time in compartments allowing a given reaction is respected, while allowing greater flexibility in the choice of volumes and surfaces between the different compartments. This makes it possible to adapt the design of an artificial wetland according to the invention to additional factors, such as the size and layout of the available land, or integration into the landscape.

This provision of the compartments is given by way of example, and the invention is applicable to a large number of possible compartments arrangements, from the moment when one or more compartments 120, 220, 221, 222 having heights Average water averages between 70 and 150 cm are placed downstream of one or more compartments 10, 210, 21 1 having water heights between 5 and 70 cm. The considerations mentioned above concerning the distribution of volumes, surfaces, and residence times among the compartments favoring the same reaction can also be applied to any artificial wetland according to the invention, which allows a even greater flexibility of the dimensions of wet areas according to the invention.

The invention thus promotes synergies between purification processes, while allowing great flexibility in the shape and arrangement of the compartments. This makes it possible to define wetlands with the desired purification capacities, while at the same time optimally adapting the layout of the wetlands to the available land.

FIG. 3 represents an example of an aerial view of a simulated artificial wetland according to the invention.

More particularly, FIG. 3 represents an exemplary simulation of an aerial view of an artificial wetland 200 according to the invention shown diagrammatically in FIG. 2.

In the example of Figure 3, the artificial wetland 200 is located downstream of a purification plant 310. The liquid effluent from the treatment plant 310 passes successively through the compartment 210 of the reedbed type ; compartments 220 and 221 of the basin type; the meander-type compartment 221; the basin type compartment 222.

In this example, the artificial wetland 200 comprises, at the outlet of the compartment 222, a media filtering device 330 comprising at least two parallel works that can be powered alternately. The media filtration device 330 makes it possible to retain suspended matter, particles and plant debris. The media filtration device 330 can also be planted with reeds to maintain the permeability of the filter material. It should however be noted that this device is optional, this example is not limiting and artificial wetlands according to the invention may not include media filtration device.

At the outlet of the media filtration device 330, the effluent is completely treated, and can be discharged into the natural environment, for example in a river 340.

FIG. 3 thus makes it possible to visualize, in a more concrete manner, examples of compartment shapes according to the invention. For example, FIG. 3 shows that the reed-type compartment 210 may have an elongated and / or sinuous appearance, the meander-type compartment 21 1 has a very elongated and / or sinuous, and compartments 220, 221 and 222-type basins a more compact appearance.

In the example of Figure 3, the compartments 220 and 221 are equipped with valleys 31 1. More generally, each compartment of an artificial wetland according to the invention can be equipped with valleys over a length greater than or equal to half of its maximum width. The presence of valleys makes it possible to improve the distribution of the flow entering the compartment. It should however be noted that the presence of valleys is optional, this example is not limiting and artificial wetlands according to the invention may not include valleys.

In this example, the basin-type compartments 220, 221 and 222 each comprise a zone with shoals, respectively the zones 320, 321 and 322. The zones with shallows make it possible to promote the emergence of macrophytes in compartments where they are present, and thus promote settling. Shoal areas can also lengthen the hydraulic path in a basin, and thus increase sedimentation without impacting the water surface. A basin-type compartment may also include several shallow areas.

A shoal area may have a decreasing slope of the bank towards the center of the compartment where it is located, to specifically promote the emergence of macrophytes near the banks of the at least a second compartment. It should be noted, however, that the presence of shallow areas is optional, this example is not limiting and artificial wetlands according to the invention may not include shallow areas.

FIG. 3 represents an example of an artificial wetland according to the invention, and shows the capacity of an artificial wetland according to the invention to be integrated in a given natural setting. Thus, an artificial wetland according to the invention makes it possible, in addition to improving the treatment of wastewater, to promote biodiversity in the environment in which it is located. An artificial wetland according to the invention also allows a harmonious integration into the landscapes surrounding the area where it is located. These points can be favored by the establishment in the artificial wetland of plant species indigenous to the region where the zone is located. [0098] FIG. 4 represents an example of an aerial view of a compartment of a simulated artificial wetland according to the invention.

[0099] Figure 4 shows a more detailed aerial view of the compartment 220 of the artificial wetland 200.

In the example of Figure 4, the valleys 31 1 are arranged at the entrance of the compartment 220, to promote the distribution of the inflow into the compartment 220. The shoal area 320 is located, at the Conversely, towards the center of the compartment 220. [00101] FIG. 5 represents a first example of a method of designing an artificial wetland according to the invention.

[00102] The method 500 allows the design and development of an artificial wetland liquid effluent purification of at least one target pollutant.

The method 500 comprises the definition 510 of at least one first compartment, having an average water height of between 5 and 70 cm. Said at least one compartment may for example be at least one of the compartments 1 10 or 210.

The method 500 also comprises the definition of at least a second compartment, having an average water height of between 70 and 150 cm. Said at least one second compartment may be at least one of the compartments 120, 220 or 221.

[00105] FIG. 6 represents a second example of a method of dimensioning an artificial wetland according to a set of embodiments of the invention.

FIG. 6 represents a method 600 for defining a compartment according to a set of embodiments of the invention, for example corresponding to one of the steps 510 and 520 of the method 500. The method 600 can therefore allow the definition of a first or a second compartment in a set of embodiments of the invention. For example, the method 600 can be used to define one of the compartments 1 10, 120, 210, 220 or 221 previously mentioned.

The method 600 comprises a first step 610 for calculating a target residence time 61 1 in the compartment, depending on a reaction type 601, and a target elimination rate 602. The times stay allowing a rate of elimination of a target molecule by a reaction can thus have been determined for example by studying the kinetics of existing wetland compartments and / or by studying in the laboratory the kinetics of reactions in small experimental basins.

The method 600 can be used to size compartments to eliminate several pollutants. In this case, a target residence time to eliminate a given pollutant can be calculated for each pollutant to be eliminated. The selected target residence time of the compartment will then be the highest target residence time among the target residence times for each pollutant. Thus, the target residence time finally selected is at least equal to the target residence time for each pollutant, and the removal rate obtained for each pollutant is at least equal to the target elimination rate of this pollutant.

According to various embodiments of the invention, the residence time can be defined for a single compartment, or jointly for several compartments. More specifically, if a single compartment makes it possible to favor a given reaction, the target residence time 61 in the compartment can be calculated directly.

If on the contrary, several compartments allow to promote the same reaction, a cumulative residence time in these compartments can first be calculated, corresponding to the cumulative residence time of the effluent in the compartments promoting the reaction. Then this accumulated residence time can be divided among the different compartments. For example, in the case of the artificial wetland 200, a cumulative target residence time in the adsorption promoting compartments can be calculated for all the compartments 210 and 21 1, and this accumulated residence time distributed over a period of time. in the compartment 210, and a residence time in the compartment 21 1.

The method 600 then comprises a step 620 for calculating the volume 621 of the compartment, from the target residence time 61 1, and the inflow. The volume of the compartment 621 can be obtained directly by multiplying the target residence time 61 1 in the compartment by the inflow 612.

In a set of embodiments of the invention, each reaction 601 to be favored is associated with an average water height 622, or a range of heights. For example, if the reaction 601 to favor is adsorption, the average height 622 can be between 5 and 70 cm; if the reaction 601 to be favored is photodegradation, the average height 622 may be between 70 and 150 cm.

The method 600 comprises, after the volume calculation step 620, a step 630 for calculating the area 631 of the compartment. The area 631 can be calculated by dividing the volume 621 of the compartment by the average height 622 of the compartment.

In one set of embodiments of the invention, each reaction 601 to be favored is associated with a perimeter / area ratio 622, or a range of ratios. For example, a compartment intended to promote plant growth and plant adsorption may have a perimeter in linear meters of between one-tenth and one-sixth of its area in square meters; a compartment designed to promote adsorption to the substrate or suspended solids may have a perimeter in linear meters of between 5% and 55% of its area in square meters; a compartment intended to promote photodegradation may have a perimeter in linear meters less than or equal to a quarter of its area in square meters.

The method 600 comprises, after the step 630 for calculating the area, a step 640 for calculating the perimeter 641 of the compartment. The perimeter 641 is calculated by multiplying the area 631 of the compartment by the area perimeter ratio 632 of the compartment.

The method 600 can calculate dimensions of a compartment of an artificial wetland according to the invention to ensure that a given reaction is favored, and a target yield will be obtained. The 600 method, however, offers some latitude to determine the dimensions and shape of the compartment, in order to adapt to other constraints or objectives, such as the available land, or the insertion of the artificial wetland into the landscape.

For example, in one embodiment where a range of average heights 622 is available, step 630 of calculating the area may include a substep of selecting an average height 622 to obtain a larger surface area. or less important, in order to adapt to the land surface available for the compartment. Similarly, step 630 can consist of calculating, from a range of possible average heights, and volume 621 of the compartment, a minimum area of compartment, and a maximum area of the compartment, then select the most suitable surface 631 according to criteria such as the land area available. The average height 622 of the compartment can then be deduced directly from the surface 631 of the compartment and the volume 621 of the compartment. It is also possible to systematically choose the maximum height from a range of possible heights, in order to have the area 631 of the compartment as small as possible, and limit the footprint of the compartment.

In one set of embodiments, the different average heights 622 are associated with different yields of the reaction. These yields can be obtained for different heights, for example by means of relationships determined experimentally between the efficiency of the reaction in function and the average height of the compartment, for example abacuses indicating the effectiveness of the reaction in function the average height of the compartment. These charts, or generally the relationship between average height 622 and reaction yield can be determined from laboratory reaction tests. Step 630 may then consist, in a first step, in selecting the height corresponding to the efficiency of the reaction. Once the area 631 of the compartment is determined, a number of constraints or secondary objectives can be validated. For example, the method 600 may include a check that the surface 631 of the compartment is small enough to adapt to the available land, allows a good landscape integration, etc. Numerous criteria relating to the integration of the compartment in its environment can to be taken into account at this stage. If one or more of these criteria is not fulfilled, the method 600 may include a return to step 630 for calculating the area, with the selection of a new average height 622 making it possible to hold the criterion or criteria relating to the integration of the compartment in its environment, maintaining a return as good as possible. Several iterations can be carried out, making it possible to ensure that the integration criteria of the compartment in its environment are taken into account, while promoting a purification efficiency as high as possible.

Similarly, the perimeter calculation step 640 may include selecting a perimeter / area ratio 632 from a range of possible ratios, in order to have a longer or longer compartment. The shape of the compartment can also be determined, in order to adapt to the available land, and / or to favor the integration in a landscape, and / or to facilitate the maintenance of the artificial wetland. For example, a compartment having a high 632 perimeter ratio (and therefore a very elongated shape) may be arranged in length, but also by meandering to limit the footprint of the compartment. This is the case, for example, of the compartment 21 1 shown in FIG. 3. Once the dimensions of the compartments have been determined, the compartments may also be arranged relative to each other in order to obtain an artificial humid zone as compact as possible, such as represented in FIG.

In one set of embodiments, perimeter / area ratios 632 are associated with different reaction efficiencies. These yields can be obtained for the different perimeter / area ratios, for example by means of relationships determined experimentally between the reaction efficiency and the perimeter / area ratio of the compartment, for example abacuses indicating the efficiency of the reaction. function of the ratio perimeter / area of the compartment. These charts, or generally the relationship between the perimeter / area ratio 632 and the reaction yield can be determined from laboratory reaction tests. Step 640 can then consist, initially, in selecting the perimeter / area ratio corresponding to an optimum yield of the reaction. Once the perimeter 641 of the compartment is determined, a number of constraints or secondary objectives can be validated. For example, the method 600 can include a verification that the perimeter 641 of the compartment makes it possible to adapt to the available land, allows a good landscape integration, etc. Numerous criteria relating to the integration of the compartment in its environment can be taken at this stage. If one or more of these criteria is not fulfilled, the method 600 may include a return to step 640 for calculating the perimeter, with the selection of a new average height 622 making it possible to hold the criterion or criteria relating to the integration of the compartment into its environment. Several iterations can be performed, making it possible to ensure that the integration criteria of the compartment in its environment are taken into account, while favoring a purification efficiency as high as possible. If the surface 631 of the compartment does not make it possible to obtain a satisfactory perimeter, the method 600 may also comprise a return to the step 630 for calculating the area, in order to select an average height 622 that makes it possible to calculate a surface 631, and a 641 perimeter of the compartment adapted to the integration of the compartment in its environment.

The method 600 thus makes it possible to determine the dimensions of compartments of an artificial wetland according to the invention making it possible to favor the desired reactions, and to obtain a target efficiency of the purification. The method 600 also makes it possible to optimize as much as possible the purification efficiency, while validating the integration constraints of the compartments in their environment.

In order to make the sizing process of an artificial wetland according to the invention more concrete, two examples are provided below, respectively for the removal of ciprofloxacin and ibuprofen.

SAMPLE EXAMPLE 1

The first example relates to the design of an artificial wetland for the removal of ciprofloxacin.

Cirprofloxacin can be removed by an artificial wetland according to the invention comprising two compartments, respectively favoring the following reactions:

- In the first compartment:

o adsorption on the substrate;

o Adsorption on suspended solids;

o Optionally, absorption by plants: - In the second compartment:

o Decantation of suspended solids on which the ciprofloxacin molecules adsorbed in the first compartment;

o Photodegradation. On the basis of a combination of tests previously carried out by the applicant, a target rate of elimination of 70% of ciprofloxacin can be reached, if the dimensions of the first and second compartments favor the reactions mentioned above. above, and if the residence time in the compartments are:

- At least 1 day in the first compartment;

- At least 2 days in the second compartment.

The artificial wet area to be dimensioned must be located downstream of a purification station (abbreviated below STEP) of 3200 male equivalent (abbreviated below EH), which corresponds for a given region to an effluent flow rate of 480 m ³ / d. Water consumption can vary significantly by region and country. Thus, the number of inhabitants in an urban community may correspond, according to the regions / countries, to a different effluent flow rate

The first compartment can then be dimensioned as follows:

- Calculation of the volume (step 620):

o The target residence time 621 is 1 day minimum, the inflow 612 480 m ³ / d;

o Volume 621 of the compartment is therefore equal to 480 x 1 = 480 m ³ ;

Calculation of the surface (step 630):

o In order to promote the contact of the micropollut targeted with the soil, and possibly the plants, and thus promote the adsorption of the micropollutant, the first compartment must have a low average height 622, in a range between 0.05 and 0.5 m. An average height 622 of 0.2 m, corresponding to an optimal adsorption efficiency is selected; The surface 631 of the compartment is then obtained by dividing the volume 621 by the average height 622 of the compartment: the area 631 of the compartment is equal to 480 / 0.2 = 2400 m ² . This surface allows integration into the available land; o

Perimeter calculation (step 640): o In order to promote the adsorption and the growth of plants, and to lengthen the hydraulic path, the ratio of banks 632 linear meter / surface of the compartment is selected from a range between 1 / ^10th and 1/6 ^e. A ratio of 0.15 m / m ² (linear meters per square meter) is selected; o The perimeter of the compartment is calculated by multiplying the ratio 632 by the area 631: the perimeter 641 is equal to 2400 x 0.15 = 360 m / (linear meters). This scope allows integration into the available land,

The dimensioning thus makes it possible to define a first compartment having the following dimensions:

- Volume: 480 m ³ ;

- Area: 2400 m ² ;

- Perimeter: 360 m /;

The second compartment can be dimensioned as follows:

- Calculation of the volume (step 620):

o The target residence time 621 is 2 days minimum, the inflow 612 480 m ³ / d;

o Volume 621 of the compartment is therefore equal to 480 x 2 = 960 m ³ ;

Calculation of the surface (step 630):

o In order to promote photodegradation, the second compartment must have a minimum height sufficiently large to prevent the growth of plants that would prevent photons from entering the compartment, and a maximum height sufficiently low for photodegradation to take place on the entire compartment. . The range of average heights 622 is between 0.7 and 1.5 m. An average height 622 of 0.8 m is selected. The height of 0.8 m corresponds, according to the experimental data collected by the applicant, the best compromise between residence time and penetration of light to promote the degradation of photosensitive molecules. In other embodiments of the invention, an iteration loop is performed on the values of the height, and the corresponding values of surface. This makes it possible to select a height associated with a surface adapted to the available land;

o The surface 631 of the compartment is then obtained by dividing the volume 621 by the average height 622 of the compartment: the surface 631 of the compartment is equal to: 960 / 0.8 = 1200 m ² ;

Perimeter calculation (step 640):

o In order to promote sedimentation, the ratio of 632 linear meters of bank / compartment surface is chosen in a range between 0.15 and 0.25. A ratio of 0.2 m // m ² (linear meters per square meter) is selected, this ratio corresponding, according to the experimental data collected by the applicant, to the best compromise between hydraulic pathway and light exposure surface to favor degradation of photosensitive molecules;

o The perimeter of the compartment is calculated by multiplying the ratio 632 by the area 631: the perimeter 641 is equal to 1200 x 0.2 = 240 m / (linear meters).

The dimensioning thus makes it possible to define a second compartment having the following dimensions:

- Volume: 960 m ³ ;

- Area: 1200 m ² ;

- Perimeter: 240 m /;

The method 600 allows, in general, define wet areas having dimensions to promote certain reactions, and obtain target pollutant removal rates. Some dimensions can be chosen from a range. In a set of embodiments of the invention, a set of secondary objectives can be achieved. These objectives can be, for example, integration into a given landscape or adaptation to available land. Method 600 may include, for these purposes, iterations. For example, if the surface 631 is too large for the available land, the method 600 may include a return to the surface calculation step 630, during which a larger height will be selected, in order to reduce the surface area. compartment. In the same way, if the 641 perimeter of the compartment is too small or too long to adapt to the available land, method 600 may include a return to step 640 perimeter calculation, during which a perimeter / area ratio 632 more or less important will be selected, so to get the desired perimeter.

In one set of embodiments of the invention, the method 600 may comprise the selection of the height or the perimeter / surface ratio making it possible to promote the desired reaction as much as possible and then, as long as the surface and / or the perimeter of the compartment do not allow to adapt to the available land, iterations of selection of a surface and / or ratio perimeter surface to better adapt to the available function.

[00131] Other shape parameters can be adjusted. For example, the entry and exit points of the compartments can be positioned to maximize the hydraulic path.

SAMPLE EXAMPLE 2

The second example relates to the design of an artificial wetland for the removal of ibuprofen.

Ibuprofen can be removed by an artificial wetland according to the invention comprising four compartments, favoring respectively the following reactions:

- First and third compartment:

o Biodegradation via microorganisms on the substrate; o Optionally, adsorption on suspended solids;

o Optionally, absorption by plants:

- Second and fourth compartment:

o Biodegradation via free biomass;

o Optionally, decantation of suspended solids on which the ibuprofen molecules adsorbed in the first compartment;

o Photodegradation.

On the basis of a combination of tests previously carried out by the applicant, a target elimination rate of 50% of the ibuprofen may be reached, if the dimensions of the first and second compartments favor the reactions mentioned above, and if the residence time in the compartments are:

- At least 1 day in the first compartment;

- At least 2 days in the second compartment;

- At least 2 days in the third compartment;

- At least 2 days in the fourth compartment;

The artificial wet area to be sized must be located downstream of a treatment STation (abbreviated below STEP) of 3200 male equivalent (abbreviated below EH), which corresponds to a flow rate of effluent of 480 m ³ / d. As mentioned above, the conversion ratio between population and flow can vary from one country to another.

The first compartment can then be dimensioned as follows:

- Calculation of the volume (step 620):

o The target residence time 621 is 1 day minimum, the inflow 612 480 m ³ / d;

o Volume 621 of the compartment is therefore equal to 480 x 1 = 480 m ³ ;

Calculation of the surface (step 630):

o In order to promote the contact of the micropollut targeted with the soil, and possibly the plants, and thus promote biodegradation via microorganisms on the substrate, the first compartment must have a mean low height 622, in a range between 0.05 and 0, 5 m. An average height 622 of 0.2 m is selected, this height corresponding, according to the experimental data collected by the applicant, the best compromise between biodegradation and plant growth;

o The surface 631 of the compartment is then obtained by dividing the volume 621 by the average height 622 of the compartment: the area 631 of the compartment is equal to: 480 / 0.2 = 2400 m ² ;

Perimeter calculation (step 640):

o In order to promote the adsorption and the growth of plants, the ratio of banks 632 linear meter / surface of the compartment is selected from a range between 1 / ^10th and 1/6 ^e. A ratio of 0.1 5 ml / m ² (linear meters per square meters) is selected, this ratio corresponding, according to the experimental data collected by the depositor, to the best compromise between elongation of the hydraulic path and increase of the contact surface between the water , substrate and plants; o The perimeter of the compartment is calculated by multiplying the ratio 632 by the area 631: the perimeter 641 is equal to 2400 x 0.1 5 = 360 ml (linear meters).

- Volume: 480 m ³ ;

- Area: 2400 m ² ;

- Perimeter: 360 ml;

The second compartment can be dimensioned as follows:

- Calculation of the volume (step 620):

o The target residence time 621 is at least 2 days, the inflow 61 2480 m ³ / d;

o Volume 621 of the compartment is therefore equal to 480 x 2 = 960 m ³ ;

Calculation of the surface (step 630):

o In order to promote decantation and degradation on free biomass, the range of average heights 622 possible is between 0.7 and 1.5 m. An average height 622 of 0.8 m is selected, this height corresponding, according to the experimental data collected by the applicant, to the best compromise between the maximum height favoring the biodegradation by oxygenation and penetration of the light, and the minimum height ensuring a time minimum stay; o The surface 631 of the compartment is then obtained by dividing the volume 621 by the average height 622 of the compartment: the surface 631 of the compartment is equal to: 960 / 0.8 = 1200 m ² ;

Perimeter calculation (step 640):

o In order to promote sedimentation, the ratio of 632 linear meters of bank / compartment surface is chosen in a range between 0.15 and 0.25. A ratio of 0.2 m // m ² (linear meters per square meter) is selected, this ratio corresponding, according to the experimental data collected by the applicant, to the best compromise between lengthening of the hydraulic path and guarantee of a residence time. at least equal to the minimum residence time;

o The perimeter of the compartment is calculated by multiplying the ratio 632 by the area 631: the perimeter 641 is equal to 1200 x 0.2 = 240 m / (linear meters),

- Volume: 960 m ³ ;

- Area: 1200 m ² ;

- Perimeter: 240 m /;

The third compartment can then be dimensioned as follows:

- Calculation of the volume (step 620):

o The target residence time 621 is 2 days minimum, the inflow 612 480 m ³ / d;

o Volume 621 of the compartment is therefore equal to 480 x 2 = 960 m ³ ;

Calculation of the surface (step 630):

o In order to promote the contact of the micropollutant with the soil, and possibly the plants, and thus promote biodegradation via microorganisms on a substrate, the third compartment must have a low average height 622, in a range between 0.05 and 0, 5 m. An average height 622 of 0.5 m is selected, this height corresponding, according to the experimental data collected by the depositor, the best compromise between elongation of the hydraulic path and slowing of the speed of the flow;

The surface 631 of the compartment is then obtained by dividing the volume 621 by the average height 622 of the compartment: the surface 631 of the compartment is equal to: 960 / 0.5 = 1920 m ² ; Perimeter calculation (step 640): In order to promote an important contact with the substrate, the ratio 632 linear meters of banks / surface of the compartment is chosen in a range between 0.05 and 0.55. A ratio of 0.5 m // m ² (linear meters per square meters) is selected, this ratio corresponding, according to the experimental data collected by the depositor, to the best compromise between lengthening of the hydraulic path and guarantee of a residence time. minimum;

o The perimeter of the compartment is calculated by multiplying the ratio 632 by the area 631: the perimeter 641 is equal to 1200 x 0.5 = 960 m / (linear meters).

The dimensioning thus makes it possible to define a third compartment having the following dimensions:

- Volume: 960 m ³ ;

- Area: 1920 m ² ;

- Perimeter: 960 m /;

The fourth compartment can be dimensioned as follows:

- Calculation of the volume (step 620):

o The target residence time 621 is 2 days minimum, the inflow 612 480 m ³ / d;

o Volume 621 of the compartment is therefore equal to 480 x 2 = 960 m ³ ;

Calculation of the surface (step 630):

o In order to promote decantation and degradation on free biomass, the range of average heights 622 possible is between 0.7 and 1.5 m. An average height 622 of 0.8 m is selected, this height corresponding, according to the experimental data collected by the applicant, to the best compromise between the maximum height favoring the biodegradation by oxygenation and penetration of the light, and the minimum height ensuring a time minimum stay; o The surface 631 of the compartment is then obtained by dividing the volume 621 by the average height 622 of the compartment: the surface 631 of the compartment is equal to: 960 / 0.8 = 1200 m ² ; Perimeter calculation (step 640):

o In order to promote sedimentation, the ratio of 632 linear meters of bank / compartment surface is chosen in a range between 0.15 and 0.25. A ratio of 0.1 m // m ² (linear meters per square meter) is selected, this ratio corresponding, according to the experimental data collected by the depositor, to the best compromise between lengthening of the hydraulic path and guarantee of a residence time. minimum. It also makes it possible to limit the proliferation of plants throughout the compartment, promote good penetration of light, optimize the storage volume to manage the minimum residence time, and optimize the slope of compartment funds;

o The perimeter of the compartment is calculated by multiplying the ratio 632 by the surface 631: the perimeter 641 is equal to 1200 x 0.17

= 204 m / (linear meters).

The dimensioning thus makes it possible to define a fourth compartment having the following dimensions:

- Volume: 960 m ³ ;

- Area: 1200 m ² ;

- Perimeter: 204 m /;

Once these dimensions have been determined, the shapes of the compartments can be defined according to additional objectives. For example, the entry and exit points of the compartments can be positioned to maximize the hydraulic path.

The above examples demonstrate the ability of wetlands according to the invention to treat pollutants, while having a limited footprint. They are however given only by way of example and in no way limit the scope of the invention, defined in the claims below.

Claims

1. An artificial wetland for purifying liquid effluents from at least one target pollutant, said artificial wetland comprising at least one first compartment stretched in length, or forming meanders (1 10, 21 1) and a second compartment forming a pond (120, 220, 221, 222) fed with an effluent of said first compartment, said artificial wetland being characterized in that:

said at least one first compartment has a perimeter in linear meters greater than or equal to 5% of its area in square meters, and less than or equal to 55% of its area in square meters, preferably said at least one first compartment has a perimeter in linear meters greater than or equal to 16% of its area in square meters, and less than or equal to 55% of its area in square meters, for example equal to half of its area in square meters preferably equal to half of its area in square meters;

said at least one first compartment has an average water height of between 10 and 70 cm, and preferably equal to 50 cm;

said at least one second compartment has a perimeter in linear meters less than or equal to one quarter of its area in square meters, and preferably equal to 17% of its area in square meters;

said at least one second compartment has an average water height of between 70 and 150 cm.

2. Artificial wetland according to claim 1, characterized in that:

the volume of said at least one first compartment is equal to the multiplication of a first residence time of the liquid effluents in said at least one first compartment by a flow rate entering said first compartment;

the volume of said at least one second compartment is equal to the multiplication of a second residence time of the liquid effluents in said at least one second compartment, by an inflow of said at least one second compartment.

3. Artificial wetland according to claim 2, characterized in that the first and second residence times are residence times determined experimentally to achieve a minimum elimination rate of the at least one target pollutant output of said at least a second compartment.

4. Artificial wetland according to one of claims 1 to 2, characterized in that it comprises at least one compartment at least one additional compartment, and:

- said at least one additional compartment has a perimeter in linear meters greater than or equal to one-tenth of its area in square meters, less than or equal to one sixth of its area in square meters, and preferably equal to 15% of its area in square meters ;

said at least one additional compartment has a mean water level of between 10 and 50 cm, and preferably equal to 20 cm.

5. Artificial wetland according to claim 4, dependent on claim 2, characterized in that the volume of the additional compartment is chosen to allow a residence time of the liquid effluents in the said at least a first compartment between 0.5 and 3 days depending on an inflow of said at least one first compartment.

6. artificial wetland according to claim 2, characterized in that the volume of the at least a first compartment is configured to allow a residence time of liquid effluents in the said at least a first compartment is between 1 and 2 days , according to an inflow of said at least one first compartment.

7. artificial wetland according to claim 2, characterized in that the volume of said at least one second compartment is configured to allow a residence time of liquid effluents in said at least a second compartment between 1 and 5 days depending on an inflow of said at least one first compartment.

8. artificial wetland according to one of claims 1 to 7, characterized in that at least one of said at least one first compartment and at least one second compartment is equipped with valleys over a length greater than or equal to half of its maximum width.

9. artificial wetland according to one of claims 1 to 8, characterized in that said at least one second compartment comprises at least one shoal area.

10. Artificial wetland according to claim 9, characterized in that said at least one shallow area has a decreasing width of the bank towards the center of said at least one second compartment.

1 1. Artificial wetland according to one of claims 1 to 10, characterized in that it is connected at the output to a media filtering device (330) comprising at least two parallel works that can be powered alternately.

12. artificial wetland according to claim 1 1, characterized in that said filtering device is planted with reeds.

13. Method (500) for developing an artificial wetland for the purification of liquid effluents from at least one target pollutant, said method comprising:

the definition (510) of at least one first compartment stretched in length, or forming meanders, having:

o a perimeter in linear meters greater than or equal to 5% of its area in square meters, less than or equal to 55% of its area in square meters, preferably equal to half of its area in square meters;

o an average water level of between 5 and 70 cm;

o Average water level between 10 and 70 cm;

the definition (520) of at least second compartment forming a basin fed by an effluent of said first compartment, having:

o a perimeter in linear meters less than or equal to one quarter of its area in square meters, and preferably equal to 17% of its area in square meters;

o average water level between 70 and 150 cm.

14. Management method according to claim 13, comprising, for at least one compartment:

a definition (610) of a residence time (61 1) in said at least one compartment, as a function of at least one type of reaction (601) to take place in the at least one compartment, and a target elimination rate (602) of the at least one target pollutant; calculating (620) a volume (621) of the at least one compartment as a function of said residence time (61 1), and an inflow (612) of effluents in said at least one compartment;

a calculation (620) of a surface of the at least one compartment (631) as a function of said volume (621), and a mean water level (622) of the at least one compartment selected according to at least one type of reaction (601);

a calculation (640) of a perimeter (641) of the at least one compartment as a function of said area (631), and a ratio (632) between the perimeter (641) in linear meters of the minus one compartment, and the surface (631) of the at least one compartment, said ratio (632) being selected according to the at least one type of reaction (601).

15. A method of purifying liquid effluents from at least one target pollutant by an artificial wetland, said method comprising successively:

the treatment of the effluents by at least a first compartment (1 10, 21 1) of the artificial wet zone stretched in length, or forming meanders, said at least one first compartment having:

o an average water level of between 5 and 70 cm;

the treatment of the effluents by at least a second compartment (120, 220, 221, 222) of the artificial wetland forming a basin, said at least one second compartment having:

o a perimeter in linear meters less than or equal to one quarter of its area in square meters, and preferably equal to 17% of its area in square meters

o average water level between 70 and 150 cm.