FR2876047A1 - Procedure for removing pollutants from waste water, air or soil uses planted filter bed which is watered periodically to provide anaerobic and aerobic phases - Google Patents

Abstract

The pollutant removal procedure consists of introducing the pollutants in solid, liquid or gas form into a planted filter bed with vertical (2) and horizontal (3) filters, and watering the bed periodically to provide anaerobic and aerobic phases. The watering allows the filter bed to be saturated during the anaerobic phases and left to dry in the aerobic phases, with the irrigation and drying phases have a relative duration that is preferably between 1 : 1 and 1 : 20. The filter bed has a drainage layer which is connected to an aeration system and another layer with the physical properties of alluvial materials with a high porosity, hydraulic conductivity and which is rich in organic materials. In another stage acidifying products or natural acids such as citric, oxalic or malic acid and preferably totally biodegradable, are added to the filter bed during watering to reduce the pH from 7 - 9 to 4 - 7. The plants used in the filter bed are e.g. varieties of reeds, rushes, sedges and irises, or trees such as willow, alder and wild cherry.

Description

TREATMENT OF POLLUTANTS BY PHYTOLIXIVIATION

  The present invention relates to a method of treating water, polluted soil or air, and more particularly a method of treatment with a plant solution (phytoremediation). The invention relates more particularly to a device implementing said method for the depollution of water, soils or contaminated atmospheres.

  The idea of using plants for environmental rehabilitation is certainly very old: 300 years ago, plants were already used in water treatment.

  Phytoremediation has recently been defined as the use of higher plants to extract, stabilize or degrade substances polluting the environment. This technique has many advantages: it allows to degrade numbers of organic pollutants, it generates residues rich in metals that can be recycled; it is applicable to a large number of toxic metals; it causes only minimal disturbances in the environment; it has a low estimated cost of between $ 60,000 and $ 100,000 per hectare in the case of polluted soil treatment, which is about half of the amount invested for the least expensive traditional procedure.

  The focal point of phytoremediation lies first at the soil / root interface, with the procession of associated microorganisms appearing as the first place of interaction between pollutants and the plant. The volume of soil subjected to the influence of root activity is defined by the term rhizosphere, which varies according to the mobility of the analyzed elements. Thus, the rhizosphere may be limited to the first millimeters of soil around the roots for the least mobile elements.

  The influence of these microorganisms on the plant includes, among others, the following actions: (i) nitrogen supply resulting from nitrogen fixation by rhizosphere bacteria (such as Rhizobium, Frankia, Azospirillum, etc.); (ii) synthesis of phytohormones (auxins, gibberellins, cytokinins, etc.); (iii) solubilization of nutrients via chelating agents; (iv) antagonism towards pathogens. The microorganisms present in this zone will thus play two essential roles by acting on the one hand on the chemical and even physical transformation of the soil and, on the other hand, on the nutrition of the plant, directly or indirectly.

  In the context of the depollution, the chemical transformations operated by these microorganisms will play a preponderant role. Examples of these include the mineralization of organic matter, the immobilization of inorganic compounds by microflora, the oxidation or reduction of pollutants (Pseudomonas fluorescens, etc.), or their assimilation and degradation.

  One of the most important uses of phytoremediation is phytodegradation, which uses plants and the associated microflora to transform toxic substances in the rhizosphere into less toxic substances. The action of rhizo- theric microorganisms plays a central role.

  In the prior art, various depollution processes have thus been envisaged in order to improve the degradation of pollutants by these microorganisms.

  Thus, US Pat. No. 4,415,450 describes a device in which wastewater is produced through a filter composed of granular materials in three layers with an initial passage in the lower layers in anaerobic medium allowing the hydrolysis of organic compounds up to the layer. planted with aquatic plants such as Phragmite communis where oxidation reactions take place in an aerobic environment. Such methods make it possible to potentiate the activity of these microorganisms for the degradation of certain pollutants. In the field of wastewater, the use of filter beds planted with reeds (reeds bed) is now well known.

  However, certain pollutants, such as metals or some very weakly biodegradable inorganic pollutants can not be degraded or eliminated by such processes, and new approaches have had to be developed for the removal of these particular pollutants.

  Phytostabilization uses a plant cover adapted to reduce the mobility of metals present in the soil. The plants used are tolerant species with an exclusion strategy. Thus, the metals are trapped at the root, decreasing the risks of leaching to groundwater or entrainment by wind or water erosion. This technique is often associated with the addition of components capable of immobilizing metals such as Zn, Cu, Pb, Cd, Ni and As in the soils. By way of example of such compounds, mention may be made of slag and phosphates. , Beringa and steel shot.

  Phytoextraction is based on hyperaccumulating species, which extract large quantities of metals from the soil and concentrate them in the aerial parts.

  Some plant species are indeed capable of accumulating large quantities of metal (up to several% by weight), while others are only tolerant and can only accumulate small quantities of metallic elements. The aerial parts concentrating large amounts of soil metals can then be harvested and subjected to thermal, chemical or microbiological treatments. However, the main disadvantage of hyperaccumulative plants is their low biomass and their specialization to treat only one or two types of heavy metals. Therefore, the current phytoextraction strategy is to use high biomass tolerant species (such as Indian mustard, corn, sunflower, etc.), coupled with the addition of chelants, such as EDTA, in the soil to enhance the accumulation of metals by plants. The majority of the work applying this strategy has involved lead extraction. Another avenue of research to increase phytoextraction would be to transfer genes responsible for hyperaccumulation in tolerant, high biomass plants.

  Finally, phytovolatilization uses plants to transform metallic elements (such as Se and Hg) into a gaseous form (such as dimethylselenide) which allows them to volatilize in the atmosphere.

  However, plants only extract a limited amount of metal, at best a few hundred kg per hectare per year. This factor limits the amount of pollutants that can be extracted in a reasonable amount of time. Soils or filter beds planted containing several percent of metals would then require many years to obtain a complete depollution. Indeed, many of these metals tend to concentrate in the soil or in the different layers of the filters, most often in the form of precipitates, which makes their extraction difficult. The processes of the prior art therefore require very significant times of up to nearly 15 years in order to arrive at a suitable depollution. In addition, many of these processes require the use of specific plants adapted to a particular pollutant, which makes them unsuitable for treating multiple pollutants.

  There is therefore still a need today for the development of new phytoremediation processes which make it possible to obtain a good depollution for a wide range of pollutants, and which simultaneously ensure a simplified management of said pollutants and this in combination with acceptable operating costs with short processing times.

  In the case of metals, their ionic fraction is a function of the redox potential changes of the medium. Thus, it is possible to increase the ionic fraction of the metals and therefore their ionic fraction under reducing conditions.

  On the basis of this observation, the Applicant has shown that it is possible to modify the redox potential of a planted filter bed and to improve the depollution as part of a phytoremediation process by watering the planted filter bed. in order to organize aerobic and anaerobic periods. Compared to the prior art, it is therefore to promote the leaching of non-degradable elements present in the soil and their subsequent trapping in a filter downstream of the planted filter bed. This invention thus relates to a novel method of phytoremediation used for the first time in a short treatment of pollutants. Hence the term phytolixiviation which has never been used before in phytoremediation scientific work for this type of treatment.

  The method according to the invention thus makes it possible to improve the degradation of pollutants by microorganisms due to this alternation of aerobic / anaerobic period and to clean up over a short period (between 1 and 2 years) for soils, a very short period of time. for water (from a few hours to a few days) and an almost instantaneous treatment for air. The process according to the invention makes it possible, because of the controlled modification of the redox potential of the medium, to improve the dissolution of the non-degradable and in particular metallic species present in the soil, and thus to promote their bioavailability for the plant species at the level of the plant. of this first compartment, but especially their leaching to a second compartment acting as a filter and their subsequent trapping in the latter.

  The method according to the invention therefore makes it possible to provide a much more complete solution in terms of depollution compared to the methods of the prior art. The treatment principle is assisted phytolixiviation of the elements to be eliminated by means of vegetated bins, pollutants which are subsequently trapped in a filter, preferably a natural filter allowing their sequestration in non-bioavailable forms.

  Consequently, the subject of the present invention is a process for the purification by phytoremediation intended for the treatment of wastewater, air or polluted soils, comprising a first step of introducing pollutants in solid, liquid or gaseous form into a filter bed. planted, and characterized in that it further comprises a step of watering said filter bed planted so as to organize aerobic or anaerobic periods.

  According to a particular embodiment of the method according to the invention, it may comprise, prior to the introduction of pollutants into the planted filter bed, a step of pretreatment of said pollutants which may consist of a passage in a screen, which may be followed by a transfer to an all-water pit or a decanter-digester.

  The alternation of aerobic and anaerobic periods makes it possible, on the one hand, to improve the degradation of the pollutants in the filter bed planted by the plants and the microorganisms of said planted filter bed, but at the same time the dissolution of the non-degradable species present in the soil, in particular the metallic species, so as to allow their leaching, and thus the leaching of the filter bed planted during each cycle. Thus, the process according to the invention makes it possible to depollute, especially by phytoremediation, urban sludge, polluted soils, various industrial or agricultural effluents and cleaning products with a view to obtaining a quality cultivable material, that is to say with traces of trace elements (heavy metals) or any other type of pollutants (hydrocarbons, pesticides, radioactivity, etc.) close to the natural contents of soils and with non-bioavailable physicochemical forms.

  Watering allows saturation of the filter bed planted with water during the anaerobic period and, during the treatment of soil or polluted water, can take the form of a controlled flood.

  The organization of the cyclic watering periods corresponds to a succession of irrigation / drying of the planted filter bed, the periodicity of the cycles being a function of the form of the pollution to be treated. Typically, the method according to the invention will use irrigation / drying cycles from 4 hours to several months in the case of treatment of polluted soil or sludge, preferably from 12 hours to 2 months and particularly preferably from order of one month. In the case of wastewater treatment, the process according to the invention will use cycles of 4 hours to two months, preferably 1 to 15 days and particularly preferably of the order of 1 to 7 days. Finally, and in the case of the polluted air treatment, the method according to the invention will use cycles of 2 minutes to 24 hours, preferably 5 to 200 minutes and particularly preferably of the order of 10 minutes.

  This significant variation in cycles is due to the fact that, in the case of soil pollution, the dissolution of non-degradable species requires a significant washing time, whereas in the case of water pollution, non-degradable species are found in the soil. and already in a more easily soluble form simplifying their leaching in the filter bed planted. Finally, and in the case of treatment of polluted air and compared to wastewater, the introduction of polluted air greatly accelerates the rate of drying of the planted filter bed which implies de facto a significant reduction in the cycle time irrigation / dewatering so as to have a viable and functional planted filter bed.

  In these different cycles, the distribution of the periods of irrigation / dewatering corresponds to a ratio of 2/1 to 1/50, preferably of 1/1 to 1/20, for example of 1/1 to 1/10, and particularly preferably from 1/1 to 1/5.

  The method then makes it possible, by the succession of aerobic and anaerobic phases, to improve the degradation of pollutants in the planted filter bed, but also to increase the variation of the redox potential during a cycle in the planted filter bed and thus to increase the dissolution of the non-degradable species in the filter bed planted and their leaching.

  Planted filter beds, especially filter beds planted with reeds for wastewater are well known to those skilled in the art and consist of different layers of materials. Such planted filter beds are also sometimes referred to as filter beds. For the simplest planted filter beds, their structure breaks down into a draining layer at the base and a layer that supports the vegetation and the development of the riceosphere. In the method according to the invention, the draining layer, which may contain drains, allows the discharge of leachate to a trapping filter during periods of saturation of the filter bed planted in water.

  The vegetation of the planted filter beds corresponds to humid wetland (Alnio-padion type) wetland plants protected by the RAMSAR convention, such as Phragmites (Phragmite communis), Scirpus communis, Sedges (Carex). acutiformis), iris (Iris speudaocorus), willow (Salix viminalis), alder (Aulnus glutinosa) or wild cherry (Prunus padus).

  Advantageously, the planted filter bed operates a vertical type filtration of the draining layer to the support layer or vice versa. In the case of a horizontal type filtration, the pollution is carried out by the simultaneous passage of pollutants in the different layers. However, such a filtration bed planted with vertical type filtration can be positioned horizontally for the depollution of wastewater, soil or polluted air, but also vertically for the depollution of polluted air.

  In the case of soil remediation, the polluted soils correspond to the layer serving as a support for the vegetation and the filtration of the pollutants takes place from the support layer to the draining layer.

  In the case of air pollution control, conversely, the filtration of pollutants takes place from the draining layer to the support layer with an introduction of polluted air at said draining layer.

  Finally, in the case of the depollution of wastewater, it can operate indistinctly from the draining layer to the support layer or vice versa, with introduction of polluted water at the level of the draining layer or at the level of the support layer respectively.

  Advantageously, the draining layer of the planted filter bed is connected to an aeration system. This aeration system connected to the base of the filter bed planted improves the efficiency of drying periods, and by the same aerobic reactions in the entire filter bed planted.

  In the case where the draining layer comprises drains simplifying the discharge of leachates to a filter, the latter can also act as aeration system. It is also possible to connect localized vents to the surface of the filter bed planted to the draining layer, and in a particular embodiment of the drains can be located in the latter.

  Advantageously, the planted filter bed used in the process according to the invention comprises a layer, other than the draining layer, comprising materials that are organic, such as black peat or compost, or alluvial. Preferably, said layer has the physical characteristics of alluvial materials with a high porosity in the range of 20 to 60% with a hydraulic conductivity in the range of 100 to 1000 (m / d) and is also rich in organic materials, including black peat.

  A layer having the desired characteristics can be simply obtained by those skilled in the art, especially by mixing alluvial materials and organic materials. It is also possible, in particular by grinding and / or drying operations, to obtain a layer having the desired properties from organic materials such as peat or composts.

  This layer may, depending on the depollution envisaged, serve as a support layer for the vegetation or may correspond to an intermediate layer located between the draining layer and the support layer for vegetation, especially in the case of polluted soil remediation.

  This layer makes it possible, because of its high organic matter content, to immobilize the non-degradable pollutant elements, and especially the metallic species, and to feed the anaerobic reactions during periods of watering, and also because of its characteristics. alluvial materials to obtain a rapid saturation in water during the watering phases. The rapidity of this saturation in water allows a significant variation of the redox potential in this layer in a short time interval, which facilitates all the transition of the metallic species or stable inorganic pollutants trapped in the latter to a cationic or anionic soluble form . This transition facilitates the leaching of this layer and the subsequent evacuation of these leachate to a trapping filter.

  The amount of organic material in said layer can be determined simply so that the anaerobic reactions have sufficient substrate.

  According to a particular embodiment of the method according to the invention, it further comprises a step of adding acidifying products or natural acids, preferably completely biodegradable, to the filter bed planted during the periods of watering. Preferably, these acidifying products are added directly to the watering water. The addition of these acidifying products makes it possible, by modifying the pH, to increase the difference of redox potential in the filter bed planted between the dry and irrigated period, and thus to increase the dissolution of the non-degradable elements and in particular the metallic species. present, and their leaching during the step of leaching the planted filter bed.

  Such an addition can be carried out simply by means of a metering pump, which are well known to those skilled in the art.

  The amount of acidifying products added to the filter mass is such that the pH value of the filter mass, before being added in a range from 7 to 9 and preferably from 7 to 8, is lowered in the range from 4 to 7, preferably from 5 to 7.

  Advantageously, the acidifying products used and totally biodegradable are chosen from natural acids, preferably from organic acids, such as citric, oxalic or malic acid, preferably the acidifying product is citric acid.

  In the case of these organic acids and in particular citric acid, these, in addition to adjusting the pH in the planted filter bed, further improve the elimination of non-degradable pollutants and in particular metallic species. present in the filter bed planted forming salts with them.

  The efficiency of the leaching step is then improved.

  Advantageously, the method according to the invention further comprises a step of discharging leachates from the draining layer of the planted filter bed to a trapping filter, which advantageously has smaller dimensions.

  This evacuation is effected simply by means of a pipe connecting the draining layer to the base of the filter bed planted with the trapping filter. Preferably, this pipe may take the form of a drain, at least in the portion thereof present at the base of the filter bed planted.

  Advantageously, the discharge of leachates to the trapping filter is controlled by a valve positioned on the pipe connecting the planted filter bed and said trapping filter. The opening and closing of this valve makes it possible to improve, by closing, the rapidity of the transition from the aerobic phases to the anaerobic phases in the planted filter bed, and by its opening the rapidity of the transition from the anaerobic phases to the aerobic phases. .

  The trapping filter allows the concentration of pollutants discharged from the filter bed planted during each dewatering / irrigation cycle and thus considerably accelerates the depollution rate. It is thus possible to simply renew said trap filter without intervening on the planted filter bed.

  The trapping filter may take the form of an enclosure comprising components capable of immobilizing non-degradable pollutants and in particular metals. Examples of such components include phosphate slag, beringa and steel shot.

  The trapping filter may also take the form of a planted filter bed, which then comprises a draining layer and a vegetation support layer composed essentially of organic materials as described above, preferably peat, so that to fix the non-degradable pollutants, and especially the metallic species present in the leachates coming from the first planted filter bed. It is also possible to implement a planted filter bed having no draining layer as a trapping filter.

  According to a particular embodiment of the method according to the invention, especially in the case of wastewater treatment, the method further comprises the evacuation of treated water.

  Said evacuation then takes place simply by means of a pipe connecting the trapping filter, and more precisely the draining layer thereof in the case of a trapping filter in the form of a planted filter bed, to the desired evacuation site.

  Advantageously, said evacuation is controlled by a valve allowing the release of the water present in the trapping filter after the trapping of non-degradable pollutants, and in particular metallic species in the latter.

  Such an evacuation can be done especially towards the natural environment, towards a filtering bed planted as described previously with the repetition of the steps as described above, or towards an infiltration and evaporation area making it possible to minimize or reach the zero discharge into the natural environment, which area may include planting willows, alders, poplars and / or birches or various aquatic plants.

  The invention also relates to a device for the treatment of polluted soils or sludge using the method described above and comprising: - a planted rack comprising a planted filter bed comprising at the base of the rack a draining layer and a second layer serving as a support for vegetation; a feed of the vegetated trays, either for conveying water, or for conveying wastewater or liquid sludge, which feed is advantageously coupled to a valve so as to organize aerobic or anaerobic periods in said planted filter bed; and a trapping filter connected to the draining layer of the planted filter bed.

  The various elements of the device are isolated from the ground by means of sealing means, which are well known to those skilled in the art and include in particular plastic films.

  The vegetation of said planted filter bed corresponds to humid-type wetland vegetation (type Alnio-padion) protected by the RAMSAR convention, such as phragmites (Phragmite communis), scirpus (Scirpus communis), sedges (Carex acutiformis), iris (Iris speudaocorus), willow (Salix viminalis), alder (Aulnus glutinosa) or wild cherry (Prunus padus).

  The structure of the draining layers is well known to those skilled in the art. For example, such a layer is generally made of pebbles or blocks of washed materials.

  The thickness of this draining layer is advantageously from 10 to 100 cm, preferably from 15 to 50 cm and particularly preferably from 20 to 30 cm.

  Advantageously, the draining layer comprises recovery drains.

  The draining layer is connected by a conduit to the trap filter, preferably said conduit serves as draining drains at the draining layer of the planted filter bed.

  Advantageously, said pipe is provided with a valve, which are well known to those skilled in the art, which allows more effective control of the discharge of leachates to the trapping filter and to improve the establishment of aerobic periods or anaerobic in the filter bed.

  According to a preferred embodiment of the device according to the invention, the planted filter bed comprises a layer, other than the draining layer, comprising materials that are organic, such as black peat or compost, or alluvial. Said layer may correspond to the vegetation support layer, ie to an intermediate layer between the draining layer and the support layer for the vegetation.

  Advantageously, said layer has the physical characteristics of alluvial materials with a high porosity in the range 20 to 60% with a hydraulic conductivity in the range of 100 to 1000 (m / d) and is also rich in organic materials, in particular black peat.

  A layer having the desired characteristics can be simply obtained by those skilled in the art as previously described.

  The thickness of this layer is advantageously from 10 to 150 cm, preferably from 15 to 100 cm and particularly preferably from 20 to 50 cm.

  According to a particular embodiment of the device according to the invention, the support layer for vegetation corresponds to polluted soil or sludge to be treated.

  The thickness of this layer is then 50 to 200 cm, preferably 50 to 150 cm and particularly preferably 50 to 100 cm.

  In this case, the layer comprising materials that are organic, such as black peat or compost, or alluvial, corresponds to an intermediate layer between the draining layer and the layer serving as a support for the vegetation.

  According to another particular embodiment of the device according to the invention, the support layer for vegetation corresponds to the layer comprising either organic materials, such as black peat or compost, or alluvial.

  According to a second preferred embodiment of the device according to the invention, the draining layer of the planted filter bed is connected to an aeration system. This aeration system, which can take the form of vents, connected to the base of the filter bed planted by means of ducts or pipes, improves the efficiency of the periods of drying, and by the same aerobic reactions in the entire filter bed planted.

  Said aeration system may in particular be connected to the recovery drains arranged in the draining layer.

  Advantageously, the planted filter bed operates a vertical type filtration of the draining layer to the support layer or vice versa.

  According to a third preferred embodiment of the device according to the invention, the latter further comprises a polluted air supply opening into the draining layer of the planted filter bed. Said supply can in particular take the form of a Controlled Mechanical Ventilation (VMC). Advantageously, said feed is coupled to a valve so that aerobic or anaerobic periods can be organized in said planted filter bed.

  Advantageously, the draining layer of the filter bed is associated with an aeration system. This aeration system may in particular take the form of vents located on the surface of the planted filter bed, which vents are connected to the draining layer and / or drains present therein through the channel.

  According to a fourth preferred embodiment of the device according to the invention, the latter also comprises feeding the vegetated pots with acidifying products or with natural acids, preferably completely biodegradable.

  Preferably, this feed is coupled to the feed of the vegetated pots in water, wastewater or sludge.

  Advantageously, this feed is coupled to a metering pump, which are well known to those skilled in the art, so that the amount of acidifying products added to the filter bed planted is such that the pH value of the filter bed planted, included before their addition in a range from 7 to 9 and preferably from 7 to 8, is lowered in the range from 4 to 7, preferably from 5 to 7.

  Advantageously, the acidifying agents used and totally biodegradable feeding the planted filter bed are chosen from natural acids, preferably from organic acids, such as citric, oxalic or malic acid, preferably the acidifying product is citric acid. .

  The trapping filter of the device according to the invention allows the concentration of pollutants discharged from the filter bed planted during each dewatering / irrigation cycle and thus considerably accelerate the depollution speed.

  The trapping filter may take the form of an enclosure comprising components capable of immobilizing non-degradable pollutants and in particular metals. Examples of such components include phosphate slag, beringa and steel shot.

  According to a fifth preferred embodiment of the device according to the invention, the trapping filter takes the form of a planted filter bed, which then comprises a layer serving as a support for the vegetation composed essentially of organic materials as described previously, of peat preference, so as to be able to fix the non-degradable pollutants, and especially the metal species present in the leachates from the first filter bed. Said planted filter bed may also comprise a draining layer.

  According to a sixth preferred embodiment of the device according to the invention, it further comprises a means for discharging the water present in the trapping filter.

  Advantageously, said evacuation means takes the form of a pipe which, in the case of a trapping filter in the form of a planted filter bed, is connected to the draining layer of the latter.

  Advantageously, said evacuation means is controlled by a valve allowing the release of the water present in the trapping filter after effective trapping non-degradable pollutants, including metal species in the latter.

  Said evacuation means may allow the release of treated effluents to the natural environment.

  According to a particular embodiment of the device according to the invention, devices according to the invention are placed in series in the same installation. The evacuation means connected to the trapping filter of a first device then corresponds to feeding a filter bed planted with a second device arranged downstream.

  According to a second particular embodiment of the device according to the invention, the latter furthermore comprises and downstream of the trapping filter an infiltration and evaporation area, which area may in particular be planted with willows, alders, of poplars and / or birches, and connected to the trapping filter by means of evacuation. This last area makes it possible to minimize releases into the natural environment.

  The accompanying drawings illustrate the invention: FIG. 1 represents a basic section of the entire treatment device for water by phytolixiviation and phytofixation.

  FIG. 2 represents a section of the first type of planted filter bed (or green filter) of the vertical type, a section of the horizontal filter and a water level regulating valve in the two types of filters for the treatment of water. .

  Figure 3 shows a section of the hydraulic control basin. Figure 4 shows the area of infiltration and evapotranspiration in the form of artificial rain forest.

  Figure 5 shows a section of the pollutant trapping filter.

  FIG. 6 represents the general ground plane of the soil or urban sludge depollution device by phytolixiviation and phytofixation.

  Figure 7 shows a section of the treatment bin polluted materials.

  Figure 8 shows the installation of different plants to promote the stimulation of the rhizosphere.

  Figure 9 shows the typical section of a horizontal planted filter bed for air. Figure 10 shows the detailed section of a filtering vegetation wall.

  Figure 11 gives an example of a filter bed planted for vertical air with internal irrigation system.

  Referring to Figure 1, the section of the entire device first of all the principle of the flow of effluents to be treated. The arrival of feedwater is at the top of the system. The water passes through a first series of vertical filters (2) consisting of a draining layer of gravel and a filter layer (mixture of granular peat and pozzolan) planted with reeds, rushes and irises. The water then flows to the second series of horizontal filters (3) having the same two types of layers of material before opening from a control valve (4) on the water control pond (5). ). At the outlet of the basin, the infiltration and evapotranspiration area (6) is planted with willows, alders, poplars and birches. Between the exit of the horizontal planted filter beds and the regulation pond is the trap filter (7) which makes it possible to trap metallic trace elements or certain compounds such as phosphorus for example.

  Figure (2) shows a section of the two types of planted filter beds (vertical and horizontal). The filter bed planted of the two types of vertical and horizontal filter consists of two types of materials arranged in superposed layers. At the base of the two types of pots is the draining layer (1) consisting mainly of pebbles, large gravel or blocks of washed material about 25 centimeters. It is in this layer that takes place the recovery drains (2) treated effluents. The drains in the vertical filter are connected to vents also constitute the aeration of this filter which is aerobic. The second layer (3) of 30/50 cm is composed of filter materials such as granular peat, pozzolan and sand if necessary. These two types of layers are also used for the horizontal filter (4) which is horizontal because of the direction of the circulation of the water. The entire bin is sealed with a sealing compound (5) preferably composed of a geo-membrane.

  With reference to FIG. 3, the ground plane of the device presents the supply system of the vertical filter (1). It has the shape of a closed loop to allow a perfect distribution of the effluents. It is also removable to be cleaned. The drains of the vertical filters are directly connected to the horizontal filters (2). The effluent recovery drains of the horizontal filters are directly connected to the trapping filter (3). Each horizontal filter has a valve (4) to close the flow of water and increase its duration of flooding at will. The horizontal and vertical compartments and the water regulation pond have a mixture of wetland plants that are: Phragmites (Phragmites communis), Bulrush (Scirpus communis), sedge (Carex acutiformis), Iris (Iris speudaocorus) ).

  Figure 3 shows the section of the infiltration and evapotranspiration area. Different types of wetland shrubs are used (1). They are willow (Salix viminalis), alder (Aulnus glutinosa), and wild cherry (Prunus padus).

  It is a type of plant formation of wetlands (Alniopadion type) protected by the RAMSAR convention.

  The entire system is sized according to the volumes of liquid effluents to be treated on the basis of 150 liters per inhabitant equivalent and an average of 2 to 12 M2 per equivalent inhabitant on average in France. This device applies to urban, agricultural and industrial wastewater.

  The design of this filter beds planted treatment allows a perfect management of the artificial environment factors recreated namely the redox and the Ph. The oxidation-reduction is controlled through the filter bed planted which has a good ventilation and by the through the bin feeding system that allows the total loading of the planted bin and its watering so as to organize aerobic and anaerobic periods.

  With reference to FIG. 5, the filter for trapping pollutants (phosphates, non-biodegradable micropollutants, metallic trace elements, etc.) comprises a simple leachate arrival drain (1) a filtering layer (2) composed of organic materials favoring again the installation of wetland plants (3) essential to maintain the permeability of the environment. This filter layer can be between 0.70 to 2 meters deep is a key element of the filter. It is composed of a mixture of granular, organic and silty materials to fix the pollutants and their carrier phase by adsorption and chemical change of the pollutants (mineral forms, non-bioavailable metallic forms ...). These materials also include fertilizers. At the base of the filter takes place a draining layer (4) of blocks of rollers on 0.30. In this last layer takes place the outlet drain of the leachates (5). It is an environment bordering on anorexia. It is a sealed box with a sealing complex (6) made of a geo-membrane generally.

  With reference to FIG. 6, the general plan of the polluted soil treatment device comprises a system for feeding the vegetated pots (1) either for conveying liquid sludge or for conveying water for irrigation. It is in this food system that natural acids are incorporated. Polluted materials, particularly polluted soils, can be deposited in a single batch in several treatment bins (2). A network of underground drains (3) recovers leachates from the bins and loaded with remobilized pollutants. These leachates are sent to the trapping filter (4) pollutants.

  With reference to FIG. 7, the section of a treatment rack shows the thickness of the materials (1) to be treated which will in no case exceed 1.2 meters in thickness. The planted filter bed consists of two types of materials arranged in superposed layers. At the base of the rack takes place the draining layer (2) essentially composed of pebbles or blocks of washed materials about 20 to 30 centimeters. It is in this layer that takes place the recovery drains (3) of leachates which also constitute the first aeration. The second layer (4) of 20 to 30 cm is composed of granular filter materials granular or organic peat pozzolan type (black peat, compost ...). It is in this last layer of the filtering mass that takes place the second aeration system (5) consists of drains directly connected to the vents acting as small air vents. The entire bin is sealed with a sealing complex (6) preferably composed of a geo-membrane. The irrigation water or leachates are then directed to the trapping filter (7).

  With reference to FIG. 8, of the treatment box with plants (1), the device is based on a mixture of wetland plants which are: Phragmites (Phragmites communis), Scirpus (Scirpus communis), sedges (Carex acutiformis), iris (Iris speudaocorus), willow (Salix viminalis), alder (Aulnus glutinosa), wild cherry (Prunus padus) types of wet formations (Alnio-padion type) protected by the RAMSAR convention.

  The entire device is sized according to the volumes of polluted materials to be treated. This device can be applied to urban sludge, cleaning products, contaminated soil and for all types of industrial pollutants (oil, mining, steel, processing, paper mills, etc.) or agricultural (slurry, white water, wine rejects). ...).

  Referring to Figure 9, the filter bed planted for the treatment of air has a polluted air inlet (by the base which allows to pulse the air through the filter bed planted.The gases pass through a bed of grating (2), a draining layer (3) made of pebbles or gravel then a geo grid (4) before reaching the filter layer (5) .The air continues its rise in the filter mass through a bed of fixing organic matter (6) and pozzolan type 5/20 (OmlO) pozzolan acts as a support for the implantation of a bacterial flora that participate in the decomposition of greenhouse gases (NO2, CO, .. This essentially organic filtering layer is planted superficially by fixing plants (7) The vegetation can be either in the open air or protected by a glass part (8) to make a greenhouse. In this case, a sprinkler system attached to the roof (9) is provided. At the base of the filter, a water recovery system is provided for treating the leachates in a trapping filter (10).

  Referring to Figure 10, the establishment of small planted lockers allows for an air filtration system that can be placed on the roofs of buildings or in the form of a vertical filtering wall. The rack (1) consists of either small PVC pans treated anti-corrosion, or small galvanized metal lockers or stainless steel. The vegetation (2) is installed on the filter layer (3). A humidification device integrated through a homogeneous network of micro irrigation drains (4) is installed in the filter layer which is also the planting substrate. The polluted air inlet drains (5) are installed in the draining layer (6). In the base of the rack or PVC tray, a recovery of the leaching water is planned to treat these waters in a trapping filter if necessary.

  With reference to FIG. 11, the installation has a vertical self-supporting vertical filtering wall thanks to a system of rigid gabions welded (1). Inside the gabions, the draining and filtering layer is held by two canvases (2) fixed on the wire mesh of the gabions by simple fasteners. The fabric retaining the filter layer (3) is a simple planting felt and the fabric retaining the draining layer (4) is an impermeable plastic tarpaulin treated anticorrosion. The polluted air inlet drains (5) are in the drainage layer and the irrigation drains (6) in the filter layer. At the bottom of the wall is a tank (7) for water recovery.

  Other advantages and features of the invention will become apparent from the following examples relating to the preparation of dry microspheres containing perfume and compacted powders containing such microspheres.

  Example 1: polluted soil treatment plant: 1) Principle: The operation of a filter garden is based on the principle of ex situ phytoremediation in vegetated bins through two successive treatment stages.

  Step 1: Phytostimulation / Rhizo filtration É Basin operating principles: - alternate irrigation, - downward vertical flow, - aerobic conditions.

  Main functions: - Soil filtration by the planted filter bed coupled with rhizofiltration / rhizodegradation by root tissue of plants (especially macrophyte plants).

  - Biodegradation / mineralization of organic matter by microorganisms associated with plants.

  The bins of the first stage are subjected to alternating cyclic irrigation. The alternation of the hydromorphic and dewatering periods makes it possible to modulate the oxidation-reduction conditions and to control the aerobic / anaerobic reactions. The period of drying sufficiently long allows the reoxygenation of the lockers to control the aerobic reactions, reinforced with artificial aeration by a system of chimneys.

  Second step: Phytofixation / Phytoextraction É Operating principles at the bin level: - upward vertical flow, anaerobic / aerobic conditions, - continuous feeding.

  F Main functions: - Trapping of metal elements on the fixing mass (peat bed) coupled with plant phytosequestration.

  - Evapotranspiration of drainage water.

  2) Organization of the device: The device consists of five experimental lockers. All the bins are dug into the ground and isolated from the rest of the soil by a sealing compound. The compartments A, B, C and D are arranged in terraces with respect to the rack E, allowing gravity to be used for the transfer of the drainage water into the rack E. The four bins of the first treatment stage (A, B , C and D) contain polluted soils at a rate of 3 t per trap. The central rack E continuously ensures the collection of drainage water on a bed of peat.

  The main characteristics of the device were as follows: Number of experimental bins 5 Depth of the bins 1 m Effective area of the bin (4x4 m at the bottom) 4 x 4 m Available volume of the bin 6 m3 Footprint of the 5 bins 80 m2 Polluted soils treated 15 t 3) Protocol: The four treatment bins were subjected to alternating cyclic irrigation which consists of a series of waterings for 5 days, with a water intake of 1600 liters per trap, carried out during the irrigation week, followed by a dewatering period (1 week for bin B and 3 weeks for bin A, C and D). The contribution of the water of irrigation is done thanks to a tank with constant volume which makes it possible to be free from the daily variations. Citric acid is added to traps A, B and C so that the pH value in these trays is between 5 and 7 during the irrigation periods. The soil in the trays is dehydrated during the dewatering period. drainage system (filter bed planted with drains) at the bottom of the lockers. The drainage water from four compartments (loaded with soluble fractions in dissolved form and in fine fractions in suspension) are recovered by a system of drains perforated at the bottom of the bin and sent, thanks to gravity flow, into the bin. E. 4) Results: The results showed that the soils of the various bins having undergone acid treatment and jointly irrigation / drying cycles has a concentration of pollutants, among which metals, very strongly reduced. In the absence of acid treatment, the same decrease in the concentration of pollutants is observed, but by a lesser factor.

  The soil analysis of the trap E corresponding to the trapping filter showed that the pollution was concentrated in the peat layer of it.

  Example 2: polluted water treatment plant: 1) Device A similar device was implemented with a first filter bed planted with vertical reeds and provided with vents connected to its draining layer composed of pebbles, which filtering mass is fed by wastewater pre-treated by screening.

  The feed is coupled to a valve to regulate the watering and dewatering periods. The watering is done for 4 hours a day followed by a period of drying of 18 hours. The feed is also coupled to a metering pump containing citric acid and to obtain a pH value of between 5 and 7 during periods of watering in the filter bed.

  A pipeline connects the draining layer of the planted filter bed to a trap filter. Said pipe is provided with a valve to prevent the passage of liquids from the filter bed planted to the trapping filter during the feeding of the filter bed.

  The trapping filter is a planted filter bed composed of a draining layer and a support layer for peat-based vegetation, which is planted with phragmites and peat.

  Finally, the trapping filter is connected by a pipe, also equipped with a valve that keeps the latter in an anaerobic environment, an evaporation and infiltration area of residual treated water planted with willows, ash trees and alder.

  2) Results The results obtained with the device described previously are the following: Components Inflow Flow from the filtering gardens Suspended matter 11 500 11 (MES, mg / I) COD (mg / I) 11 200 41 Biological application in 8 700 53 Oxygen (BOD, mg / I) Hydrocarbons dissolved 51 0.2 PAHs (mg / I) 0.1 0.002 NTK (mg / I) 2.1 1.4 Pt (mg / I) 1.7 0.9 Copper 360 The results show that the device according to the invention makes it possible to obtain a strong depollution of the wastewater entering the filtering garden, which depollution is effective for all the pollutants tested.

Claims (16)

  1) Phytoremediation depollution process for the treatment of wastewater, air or polluted soils comprising a first step of introducing pollutants in solid, liquid or gaseous form into a planted filter bed, and characterized in that it further comprises a step of watering said filter bed planted so as to organize aerobic or anaerobic periods.   2) Method according to claim 1, characterized in that the watering allows saturation of the filter bed planted in water during the anaerobic period and in that the organization of the cyclic periods of watering corresponds to a succession of irrigation / drying of the filter bed planted.   3) Process according to any one of the preceding claims, characterized in that the distribution of periods irrigation / drying corresponds to a ratio of 2/1 to 1/50, preferably 1/1 to 1/20.   4) Process according to any one of the preceding claims, characterized in that the planted filter bed operates a vertical type filtration.   5) Method according to any one of the preceding claims, characterized in that the draining layer of the planted filter bed is associated with an aeration system.   6) Method according to any one of the preceding claims, characterized in that the planted filter bed comprises a layer, other than the draining layer, having the physical characteristics of alluvial materials with a high porosity in the range 20 to 60% and a hydraulic conductivity in the range of 100 to 1000 (m / d), which layer is also rich in organic materials.   7) Method according to any one of the preceding claims, characterized in that it further comprises a step of adding acidifying products or natural acids, preferably completely biodegradable, filter bed planted during the periods of watering.   8) Process according to any one of the preceding claims, characterized in that the amount of acidifying products added to the planted filter bed is such that the pH value of the filtering bed planted, included before their addition in a range of 7 to 9, is lowered in the range of 4 to 7.   9) Process according to any one of the preceding claims, characterized in that the acidifying products used are chosen from natural acids, preferably from organic acids, such as citric, oxalic or malic acid.   10) Process according to any one of the preceding claims, characterized in that it further comprises a step of discharging leachates from the draining layer of the filter bed planted to a trapping filter.   11) Device for the treatment of soil or polluted sludge using the method described above and comprising: - a vegetated bin comprising a planted filter bed comprising at the base of the bin a draining layer and a second layer serving as a support for the vegetation ; a feed of the vegetated trays, either for conveying water, or for conveying wastewater or liquid sludge, which feed is advantageously coupled to a valve so as to organize aerobic or anaerobic periods in said planted filter bed; and a trapping filter connected to the draining layer of the planted filter bed.   15) Device according to claim 11, characterized in that the planted filter bed comprises a layer, other than the draining layer, having the physical characteristics of alluvial materials with a high porosity in the range 20 to 60% with a hydraulic conductivity in the range of 100 to 1000 (m / d) and is also rich in organic materials, including black peat.   16) Device according to any one of claims 11 or 12, characterized in that the draining layer of the planted filter bed is connected to an aeration system.   14) Device according to any one of claims 11 to 13, characterized in that the planted filter bed operates a vertical type filtration of the draining layer to the support layer or vice versa.   15) Apparatus according to any one of claims 11 to 14, characterized in that it further comprises a supply of vegetated pots acidifying products or natural acids.   16) Device according to any one of claims 11 to 15, characterized in that the trapping filter takes the form of a planted filter bed, which then comprises a draining layer and a layer serving as a support for vegetation consisting essentially of organic materials.