EP1584751A1 - Soil treatment process using at least one monopolar coaxial electrode system and apparatus for performance of the process - Google Patents

Abstract

The method involves vertically sinking a rectilinear coaxial monopolar electrode system (12) in soil, where the system has a rod having a polarity zone and an insulating zone, and a hollow tube surrounding the rod and constituting another polarity zone. The latter polarity zone is placed in order to uncover the former polarity zone of the system. The system is polarized under the action of an electric field. Independent claims are also included for the following: (A) a method of dehydration of soil and/or pollution control of the soil (B) a device for soil treatment (C) an utilization of the soil treatment device for dehydration and/or pollution control of the soil.

Description

The invention relates to a soil treatment method including the use of at least one system coaxial monopolar electrodes depressed at least part in the ground. The invention also relates to a device intended more particularly for the implementation of such a process. The invention finally relates to the use of such a method or device for dewatering and / or decontamination of sludge quarrying and / or mining products and / or by-products of mining.

Lagooning quarry sludge is a practice common. We also find this practice in the mining sector, whether for residues of coal mining or for mining sludge various metals. Indeed, sands, gravels, minerals or other materials, extracts from the soil, are generally required be washed with water during or after extraction. So we end up with the presence of lagoons. These lagoons are spaces with a mixture liquid-solid that is to say mud, with generally a majority proportion of liquid that is the most often at least partly supernatant. These lagoons pose problems in terms of environment and security (ground more or less moving). Natural consolidation of these lagoons is even longer than the climate regional is wet. For example, in Normandy, in France, it takes more than ten years for earthworks can maneuver on the surface of lagoons careers.

The principle of dehydration of such lagoons by electro-osmosis is known. Thus, in the publication "Stabilization Consolidation Treatments for Soft Clayey Soil", Fernando Veniale, Bul. Stiint. The Institute of Constructii Bucurestii, T.30, Nr.1, 1984, p.59-67 describes the application of electro-osmosis to the treatment of clay consolidation of quarries using electrodes. based on aluminum. Monopolar electrodes are thus alternated and driven regularly into the treated ground in order to dehydrate the quarry. Each electrode is of one polarity. The two polarities are represented and alternated within the system thus constituted.

Such methods described in the prior art pose a lot of technical problems such as the loss of contact between the electrodes arranged on the surface and the mud during treatment, which leads to excessive energy consumption, or the cracking of the mud before it is sufficiently dehydrated. In particular, the cracks thus created pose problems of parts of water that go down in the soil whereas they have been more or less back up by the treatment, as well as problems insulation (the electric field no longer works) because these cracks extend parallel to rows of electrodes and interspersed between the rows electrodes of opposite sign or polarity or opposite.

Another problem that is encountered is crusting on the lagoons (i.e. dehydration or even desiccation of the surface while the bottom is only slightly affected by the treatment).

The method and the device according to the invention solve the problems of the prior art, in that they allow, by the use of at least one coaxial monopolar electrodes system, preferably a plurality of electrode systems monopolar coaxial, to process, mainly from dehydrate and / or depollute, the interior of a soil (eg a quarry lagoon) through the use said one or more electrode systems planted vertically in said soil, usually from the area. The depollution according to the invention comprises the possible treatment of pollutants, mainly ionic and / or ionizable species, organic and / or mineral. The dehydration according to the invention is usually associated with a pumping system generally on the surface of the quarry, which allows to extract the water.

a) Au moins un enfoncement sensiblement vertical au moins partiel dans le sol d'au moins un système d'électrodes monopolaires coaxiales sensiblement rectiligne, ledit système d'électrodes comprenant au moins une tige comportant au moins une zone de première polarité et au moins une zone isolante, et au moins un tube creux entourant au moins partiellement ladite tige et constituant au moins partiellement une zone de seconde polarité apte à coulisser au moins partiellement autour de ladite tige, ladite zone de seconde polarité étant placée de façon à découvrir au moins une zone de première polarité dudit système d'électrodes, de préférence la zone de première polarité située le plus près de l'extrémité inférieure de ladite tige,

b) Une mise sous champ électrique du système d'électrodes.

Thus, the method according to the invention is a soil treatment method comprising the following successive steps:

a) At least one substantially vertical at least partial depression in the ground of at least one substantially straight coaxial monopolar electrode system, said electrode system comprising at least one rod comprising at least one zone of first polarity and at least one insulating zone, and at least one hollow tube at least partially surrounding said rod and at least partially constituting an area of second polarity capable of sliding at least partially around said rod, said second polarity zone being placed so as to discover at least one first polarity region of said electrode system, preferably the first polarity zone closest to the lower end of said rod,

b) An electric field of the electrode system.

Typically, step a) is generally such that the placement of said second polarity zone is such that said zone of second polarity also discovers at less partially an insulating zone, located generally at least partly between the said zone of first polarity and said second polarity zone.

Preferably, said stem comprises an alternation areas of first polarity and insulating areas. According to the invention, "an alternation of zones of first polarity and insulating areas "means at least two successions of a zone of first polarity and a zone insulation, an estate consisting of a zone of first polarity followed by an insulating zone, the zones first polarity usually adjacent to each one or two insulating zones, the insulating zones adjoining usually each one or two prime areas polarity.

In step a), said electrode system once embedded in the soil preferably has one end superior off the ground, that is, above the soil surface as it will be explained later, at least one zone of second polarity in the ground, and a lower end having at least one zone of first polarity in the ground. So, in step b), the current flows and there is a difference of potential between the zone of first polarity discovered by the second polarity zone and said zone of second polarity, usually separated from the second polarity at least partially by at least one insulating area.

By "soil" is meant according to the invention any surface on which one could walk, including essentially a more or less hydrated material the constituents are essentially original geological and / or pedological, whether in place naturally and / or following at least one human intervention. Sludge basically of mineral origin, including quarry slurries, are included in this definition, even if it can not be walk safely (ground more or less moving).

By "sludge" is meant according to the invention a mixture solid-liquid, with usually more liquid than solid. Typically, in the case of quarry sludge, the liquid is water and the solid is a clay or any other finely divided material. In order of magnitude, it can be indicated that a sludge contains a amount of solid of at least 50 g / l in the liquid. AT As an example, a career mud can understand about 800g / l of clay in water, ie 50 to 60% by weight of dry matter, for a density of about 1.8.

By "coaxial monopolar electrode system", according to the invention is meant an electrode system, comprising at least one zone of first polarity, for anode example, and at least one second zone polarity, contrary, for example cathodic, that is to say generally comprising at least one anode and at least less a cathode. Unlike the prior art, this system includes within it the two polarities, and not one polarity. This electrode system is polarized under the action of an electric field, by example by closing a circuit comprising at minus one generator across polarity zones opposite. It therefore works most often to voltage constant. By "electrode" is meant according to the invention cathode or anode. According to the invention, a zone of first polarity is usually either cathodic or anodic, and a zone of second polarity, polarity contrary to that of the zone of first polarity, is either anodic or cathodic.

Activation step b) allows the treatment, mainly by electro-osmosis and / or electromigration, water and ionized species present in the soil near said system of electrodes, that is to say in an area of influence around the system. Consequently, according to the invention, thanks choice wise and adapted polarity zones contrary, water and ionized species (ie from ionic and / or ionizable species) are able to migrate to the second polarity zone.

Such a zone of influence is necessarily limited in size, and depends on many parameters such as the nature of the soil, its water content and / or its pollution, the geometry, nature and number of systems electrodes etc. Such an area of influence is easily known to those skilled in each case he approaches, at least after a few tests on the soil undergoing treatment according to the invention. he it is not possible to define it precisely in advance, even if the person skilled in the art usually practicing such treatment can know its order of magnitude.

Advantageously, the coaxial form of the systems of electrodes allows that possible cracks, which can be generated during the treatment process according to the invention, appear radially so as not to hinder the passage of the electric field.

c) Une désactivation du système d'électrodes par arrêt au moins partiel du champ électrique,

d) Une remontée partielle de la zone de seconde polarité permettant de découvrir au moins une nouvelle zone de première polarité et/ou au moins une zone isolante, et

e) Eventuellement une remise sous champ électrique du système d'électrodes.

In a preferred embodiment, the method according to the invention further comprises at least one succession of the following successive steps:

c) A deactivation of the electrode system by at least partial stopping of the electric field,

d) a partial rise of the second polarity zone making it possible to discover at least one new zone of first polarity and / or at least one insulating zone, and

e) Possibly a refitting in electric field of the electrode system.

Typically, step d) is such that the ascent partial of the second polarity zone allows for discover at least partially a new area of first polarity and at least partially a new insulating zone, that is to say a succession of zones of first polarity and insulating area. The new zone insulation is usually located at least in part between said new zone of first polarity and said second polarity zone.

In one embodiment of the method according to the invention, said method comprises the dismantling of any zone of second polarity superfluous. For example, when the realization of step d), it is brought to the surface an area of second polarity that is no longer useful, and which is superfluous. It is possible to predict that this second polarity zone is completely dismountable or in part. Thus the method according to the invention can understand the disassembly of said second zone superfluous polarity.

Advantageously, when used in dehydration, the process according to the invention comprises at least less partially, preferably substantially totally, a pumping of liquid, usually comprising water, on the surface of the soil.

The hollow tube constituting at least partially the second polarity zone usually includes at least an insulating inner zone, usually on practically all its length.

Thus, by a method implementing the use of coaxial electrode systems and phenomena physics of electro-osmosis, that is to say of movement of the water molecules contained in a matrix more or less solid by the action of an electric field continuous, and / or electromigration, that is to say in motion of ionized (ie ionic) species and / or ionizable that have ionized) by this same field the method according to the invention makes it possible dehydrate or even consolidate soils, especially Quarry mud lagoons. As it will be explained below, the consolidation of these soils is advantageously from the bottom of the humidified space even drowned, that is to say from the bottom of the lagoon to the area. In a particularly advantageous way, such a consolidation is possible under water, ie if the surface is submerged under a certain thickness of water, by example at least 1.5 meters (inclusive).

"Out of the ground" therefore means according to the invention usually in atmospheric air and / or in water.

The invention therefore advantageously compared in the state of the art, thanks to the use clever and combined of at least one electrode system geometry and an implementation of a second polarity zone movement to the surface, discovering at least one zone of first polarity, one progressive dehydration from the bottom of the lagoon even a consolidation, even under water.

Another advantage of the method according to the invention is a low energy consumption, because the space between the first polarity zone and the second polarity zone is generally minimum, ie relatively low. Such a space is generally dimensioned according to various parameters such as for example the number of electrode systems; the geometry of each electrode system; the quantity a priori of water to be eliminated; the ionic or ionizable species pollution that can be treated according to the method of the invention.

Another advantage of the process according to the invention is the relative ease of implementation of the system or systems electrode.

In a particular embodiment according to the invention, the electrode system being mainly consisting of assemblable parts called sections, Depressing the electrode system into the ground through a progressive process of embedding and successive assembling sections to each other, said process comprising at least one step at least partial depression of at least one section, creating a set of sections at least in part depressed, followed by at least one assembly step at least partial of at least one other stretch to the set of at least partially embedded section (s). A such embodiment advantageously allows to facilitate the insertion of the electrode system into the ground. Preferably, such an assembly comprises at least screwing.

Advantageously, such a particular mode of realization allows the implementation relatively simple of the method according to the invention, since it is a question of vertically short sections of system of electrodes, to screw one or more new sections short on these, to push in again and start again until you reach the bottom of the "pond" (where most of the soil is humidified drowned).

The electrode systems used are or are not two with two similar ones, both in dimensions and in geometry and / or in polarity.

In an advantageous embodiment of the invention, the method according to the invention is such that a plurality of electrode systems are used, said electrode systems being preferably practically all, preferably all, of polarities identical (that is, areas of the same polarity have the same sign), and proceed to the different steps, preferably substantially simultaneously, for each of said electrode systems. So the treatment of a soil, for example a lagoon of several hectares is done simply by implanting as many systems electrodes as needed. The number of systems of electrodes varies according to different parameters such as the surface of the soil to be treated. As explained previously, the geometry of the electrode systems determines at least partly the zone of influence of these systems electrode. Preferably all systems of electrodes are of virtually identical geometry but it is also possible according to the invention that they are at least partially geometrically different, ie at least two, or more two of them are of substantially different.

In the case of use for dehydration quarries, dehydrated lagoons even consolidated thus obtained are the first to be obtained effectively and for a reasonable period of time by a method of using electrode systems monopolar coaxial, which shows a progress considerable extent of the invention in relation to the state of the technical.

By "activation" of the electrode system according to the invention is understood to mean placing in an electric field. Such placing in the electric field allows the treatment water or even ionic and ionizable species in the soil, as previously explained. Voltage imposed is generally substantially constant, and the intensity varies according to the parameters such as nature of the ground...

The invention also relates to a method of soil dehydration and / or soil remediation comprising at least one soil treatment method, particular career, according to the invention.

The invention also relates to a device for soil treatment comprising at least one system coaxial monopolar electrodes substantially rectilinear, said electrode system comprising at least least one rod comprising at least one zone of first polarity and at least one insulating zone, and at least one hollow tube at least partially surrounding said rod and at least partially constituting a second zone polarity able to slide at least partially around said rod, said electrode system being adapted to be put under an electric field.

The electrode system is usually preferably able to be depressed at least partially in the ground, most often so, once depressed in the soil, to have a top end out of floor and a lower end with a zone of first polarity in the ground. A means of depression in the soil is for example a sharp form and beveled of the lower end to be depressed in the ground.

Said rod preferably comprises an alternation of areas of first polarity and insulating areas.

In a preferred embodiment of the device according to the invention, said second polarity zone is in in addition able to be reassembled at least partially towards the up so that you can discover at least one new zone of first polarity, preferably a new alternation of zone of first polarity and zone insulation, and if possible as often as necessary.

Preferably, the second polarity zone is suitable to be disassembled at least partially, preferably almost totally.

According to the invention, the device comprises at least means for activating the electrode system, that is to say at least one means for placing the electrode system.

Preferably, the electrode system is mainly consisting of assemblable parts called sections, and even more preferably such a assembly comprises at least one screwing.

The zone of first polarity or second polarity, when it is cathodic, generally includes preference is mainly made of steel stainless steel (or stainless steel) or non-stainless steel, preferably stainless steel. In case she mainly consists of non-stainless steel, this is a consumable electrode.

The zone of second polarity or first polarity, when it is anodic, generally includes preferably consists mainly of (of) titanium, preferably entirely of titanium, covered with less a metal compound, precious or not, said compound of metal, precious or not, being chosen preferably in the group consisting of ruthenium, iridium, tantalum, tin, and antimony, in less partially oxidized or not, and mixtures thereof.

Preferably, the insulating zone of said rod mainly includes plastic such as at least one polymeric compound selected from the group consisting of polyvinyl chloride, polyethylenes (all densities), polypropylenes (all densities), and their mixtures.

In the case where the rod has anodic zones and insulating areas, the rod can for example in a first version be entirely a bar made up of titanium coated with precious metal and comprising regular intervals, over said titanium, a sheath for example heat shrinkable typically HDPE (Poly High Density Ethylene) forming insulating areas. A second version, less expensive, of this example is a stem made of alternating parts, one of the parts with titanium uncoated with precious metal and covered with such HDPE sheath, and the others parts consisting of titanium coated with metal precious.

In a preferred embodiment of the device according to the invention, the hollow tube constituting at least partially the second polarity zone comprises at less an inner insulating zone usually on practically all its length. In such a case, that internal insulation zone usually includes plastic such as at least one selected polymeric compound in the group formed by polyvinyl chloride, the polyethylenes (all densities), polypropylenes (all densities), and their mixtures.

Preferably the device according to the invention further comprises at least one placement means (i.e. setting up by depressing at least partially in the ground), mechanical or manual, of at least one system electrode. Such a means of investment is generally Manual for low thicknesses and weak floor resistors, for example at least one cattail or a hammer. Otherwise, such a means is mechanical; he for example includes at least one drill.

The electrode systems used are or are not two with two similar ones, both in dimensions and in geometry and / or in polarity.

According to a preferred embodiment, the device of the invention comprises a plurality of systems electrodes, said electrode systems being of preferably all, preferably all, of identical polarities, that is to say that the zones of first polarity are the same polarity and that the zones of second polarity are of the same polarity. The number of electrode systems varies according to different parameters such as the lagoon surface to be treated as explicit previously.

The device according to the invention is particularly adapted for implementing the method according to the invention as previously described.

Similarly, the invention relates to the use of a device as described above, for the soil dehydration and / or soil remediation, especially quarry sludge (quarry lagoon) and / or mining products and / or by-products mining.

In the case of dehydration use even consolidation of quarry sludge lagoons, a zone of second polarity is cathodic and zones of first polarity are anodic. The phenomenon of electro-osmosis gradually leads to at least partially, preferably practically total, water to the cathode zone. So, as and when measurement of the treatment of the lagoon, we slide the second polarity zone upwards along the zones insulating and first polarity which are kept fixed. So we force the water to go up along the system of electrodes to the cathode and thus gradually to the surface. The water thus gradually returned to surface is particularly easy to pump, and possibly to recycle. This treatment is accompanied of a depollution when there is presence in the soil of cations for example of metals. These cations go back towards the surface with the water in which they are dissolved. This is particularly effective in the case recent pollution, that is to say typically some months.

The invention also allows an inorganic depollution, mainly in the case where a zone of second polarity is anodic and zones of first polarity are cathodic. As the treatment progresses, the second polarity zone is slid upwards along the insulating and first polarity zones which are kept fixed. The phenomenon of electromigration gradually leads at least partially, preferably almost completely, the polluting anions that are for example nitrate ions NO ₃ ^- and / or cyanide CN ^- , to the anode and therefore to the surface. On the other hand, the water and the cations possibly present in the water, such as calcium Ca ²⁺ , are driven by electro-osmosis phenomenon and gravity towards the cathode zone, and therefore towards the bottom; it is therefore generally necessary to provide at least one water supply system to the electrode system from the inside and / or the outside of the tube, to avoid excessive dehydration that would significantly disturb the phenomenon of electromigration. Such use is very significant in the case of accidental pollution, for example nitrates from a soil above a water table. It makes it possible to sustainably protect said layer of pollution by treating said soil.

The invention also allows an injection of water to the bottom of a soil such as a sump. In this case, the treatment according to the invention makes it possible to circulate the water towards the bottom of the soil, without the risk of abrupt rise of the sheet and without the need to manufacture a well. In this case, a zone of second polarity is anodic and a zone of first polarity is cathodic, and located at the end of the rod which otherwise consists of an insulating zone. The electrode system thus formed can advantageously pass through more or less impermeable clay layers without significantly altering their impermeability. The cathode is located below said layers in a permeable zone. Advantageously, the clay also makes it possible to filter the water passing through it. Out of the ground, said system emerges in the water that we want to transfer in depth. The water (and the cations possibly present in the water, such as Ca ²⁺ calcium), is gradually driven at least partially, preferably substantially completely, to the cathode zone, and thus to the bottom. The water can thus pass through said clay layer.

The invention will be better described and others features and benefits will appear on reading description which will follow, given as a non limiting, with reference to FIGS. 1 to 10.

Figure 1 represents, schematically, a system 12 coaxial monopolar electrodes with movable sliding cathode 1 according to the invention.

Figures 2 to 9 show, so schematic, a three-phase treatment for dehydrate a lagoon 14 of quarry sludge according to the invention, by a device comprising the system 12 of electrodes in FIG. 1. Thus FIG. beginning of treatment, Figures 3 and 4 represent a partial rise of the cathodes (a moving cathode electrode), Figure 5 shows a disassembly of superfluous cathode parts, FIG. a reset under electric field, FIG. a partial rise of the cathodes, figure 8 represents a disassembly of cathodic parts superfluous, and Figure 9 represents a setting in the field electrical end of treatment.

Figure 10 is a schematic representation of a other system 13 concentric monopolar electrodes with sliding anode 9 mobile according to the invention.

Figure 1 represents, schematically, a system 12 coaxial monopolar electrodes with movable sliding cathode 1 according to the invention. She comprises a sliding mobile cathode 1 having a interior insulation (not shown), a set 2 of insulating zones fixed on a set 3 of anode zones fixed. The cathode 1 may consist of parts 1a, 1b, 1c, 1d, 1e, 1f, 1g and 1h (not shown on the figure 1). We see that the set 2 of insulating areas consists of parts 2a, 2b, 2c and 2d, and that the whole 3 of anode zones consists of the zones anodic 3a, 3b, 3c, 3d and 3e. Only insulating areas 2a and anode 3a are discovered by the cathode 1.

Figures 2 to 9 show, so schematic, a three-phase treatment for dehydrate a lagoon 14 of quarry mud according to the invention. They correspond, as it will be explained hereinafter, to a first system 12 of electrodes according to the invention, as represented for example on the figure 1. This treatment will serve us, after description FIGS. 2 to 9, to illustrate the advantages of the invention.

FIG. 2 according to the invention represents the beginning of treatment of lagoon 14, bottom 15 and surface 16, of quarry sludge, in which were set up at least eleven systems 12 of electrodes such as shown in Figure 1. Water 4 rises above of the surface 16, a part 14a already dried out of the lagoon 14 is located above the bottom 15 thereof, and part 14b not yet dried or wet (or drowned) of Lagoon 14 is located above part 14a. We see that for this first phase of 8 dewatering zones are formed, that come together through zones 7 intermediaries which are also gradually dried up. The set of zones 8 and zones 7 corresponds to the Part 14a dried up. Arrows 6 illustrate the upward movement of water to cathode 1, which causes a capillary rise towards the surface 16. The water 4 that appeared above the surface 16 of the lagoon 14 is pumped by at least one pipe 5, the pumping being symbolically represented by an arrow. In the case where water 4 was present above the surface 16 before the start of treatment it is possible but not obligatory according to the invention to proceed to a pumping before the beginning of said treatment.

Figure 3 symbolizes the beginning of the recovery of cathodes 1. It shows that in addition to the anode zone 3a departure and the insulating zone 2a of departure, it was discovered a new anodic zone 3b on each 12 system of electrodes.

Figure 4 shows the end of the recovery of cathodes 1. In addition to the anodic zone 3b discovered previously (see Figure 3), it appears a new insulating area 2b. For the 12 electrode systems of periphery of lagoon 14 which were sunk less deeply because of the shallower depth of the lagoon 14 in this place, these are the anodic zones 3a and insulator 2a which are now discovered.

Figure 5 shows the dismantling of the parts unnecessary cathodic 1a, and possibly 1b, 1c, 1d and 1e cathodes 1, according to the length of each system 12 of starting electrodes and therefore of each cathode 1.

Figure 6 shows the reinstatement under the electric field of lagoon 14. We see new arrows appear 6a upwelling to the surface 16, new 8a dewatering zones around the systems 12 of electrodes, and new zones 7a intermediate between zones 8a. So in this second phase, we distinguishes a wet part 14c from the lagoon 14, which is smaller than the wet part 14b of the first phase, and a dried part 14d, which corresponds to all zones 8a and 7a, and which is more important that zone 14a dried out from the first phase. The pumping is always illustrated by the pipe 5 of pumping.

In Figure 7, we see the rise of the cathodes 1 following the second phase of treatment, discovering anodic zones 3c and insulating zones 2c.

Figure 8 shows the dismantling of the parts superfluous 1f, and possibly 1g and 1h cathodes 1.

Figure 9 shows a third phase of dewatering by repositioning in an electric field including again dewatering zones 8b with the systems 12 of electrodes, the upwelling 4 to the surface 16 being indicated by the arrows 6b, and zones intermediate 7b of junction between zones dewatering 8b. So in this second phase, we distinguishes a 14th wet part of the lagoon 14, which is smaller than the wet part 14c of the second phase, and a dry portion 14f, which corresponds to zones 8b and 7b, and which is more important than the 14d dry zone of the second phase. The pumping is always illustrated by the pipe 5 of pumping.

For the end of the treatment it does not stay on the surface 16 of Lagoon 14 than a thin 14th layer of mud relatively soft. This one, no longer being fed (by ascent capillary) by the large body of water that was departure between the bottom 15 and the surface 16 of the lagoon 14, dries naturally with the wind and the sun very little time. Possibly a series of measurements at PANDA® light penetrometer can be used to determine mechanical resistance of dehydrated materials, and therefore the end of the project. At the end, the systems 12 electrodes are extracted from lagoon 14 to be possibly reconditioned for reuse on another yard or on that same lagoon 14 when she will be full again. Such repackaging includes generally at least one cleaning and / or at least one restoring deposit on at least one electrode. he there is then only to empty the lagoon 14 to the tracto-shovel if necessary, lagoon 14 dehydrated and consolidated now being accessible to construction machinery.

Figure 10 is a schematic representation of a other system 13 coaxial monopolar electrodes with movable sliding anode 9 according to the invention. The system 13 electrode comprises a sliding anode 9 isolated to inside (insulation not shown) and lubricated to outside such as water or bentonite, and a set of 10 isolated insulating areas fixed on a set 11 fixed cathode zones. The anode 9 can be consisting of parts 9a, 9b, etc. (not shown) We sees that the set of 10 insulating zones is constituted insulating areas 10a, 10b, 10c and 10d, and that the set 11 of cathode zones consists of zones 11a, 11b, 11c, 11d and 11e. Only insulating area 10a and cathode zone 11a are discovered by the anode 9.

Thus, FIG. 10 represents a system 13 of electrode for progressive destruction of pollutants organic matter and / or to return to the surface of a soil of anionic pollutants (such as nitrates and / or cyanides). The electrode system 13 of FIG. remediation of soil 14 and / or water table polluted by at least one anionic species for example selected from the group consisting of nitrates and cyanides. Said anionic species can be traced back to surface 16 to facilitate his treatment that can be biological and / electrochemical in the case of cyanides, and / or physico-chemical and / or phytoremediation (or treatment with at least one plant). In the case of treatment of a soil, the device comprising this system 13 electrodes can help prevent contamination of a water table that is not yet affected by the pollution of said anionic species.

The rise of pollutants through a device comprising the electrode system 13 of FIG. does exactly the same way that that of the electrode system 12 described in the figures 2 to 9.

According to the invention, it is possible to have additional means to change the influence of electrode systems. For example it is possible to extend the insulating zone (s) to widen the areas of electric field influences and so decrease the number of electrode systems needed to cover an area of several hectares.

According to another embodiment, independent or non of the previous embodiment, it is possible to increase the length of an electrode system, by example and preferably by increasing the number of sections of which the system is preferably of electrodes, to go deeper within the lagoon.

According to a third embodiment, independent or not of each of the two embodiments precedents, it is possible to increase the number of electrode systems to speed up the work.

It is interesting to note that, according to the method of the invention, it is very advantageous to dehydrate the lagoon starting from the bottom. On the one hand, cracks that eventually appear during treatment are radial and do not interfere with the process of dehydration. On the other hand, it is important to note that the system can work under water, that is to say that it can "pack" sedimentary sludge under surface of a water reservoir and thus allow at least to space out the usual cleaning operations.

According to the invention, in the case of the system 12 described in FIGS. 1 to 9, the zones of first polarity, here anodic zones, are activated in discovering them. The water around the cathode serving as lubricant, the mechanical forces are thus advantageously limited. When the area around the first zone of first polarity discovered becomes too resistant, we go up the second polarity zone what is the cathode, the distance between the cathode and the nearest anode is always the same, with a water content always favorable to the passage of the current.

Depending on the intended application, one or the other possible physical phenomena will be favored. Without wanting to be bound by a given explanation, one can try to give the following explanation. In particular the phenomena of electro-osmosis concern at least in part the lagoon dehydration applications of sludge or settlement of sediment in a reservoir of water. The phenomenon of electromigration, which allows generally to go back at least in part to the surface of mineral pollution and / or which favors the in-situ destruction of organic pollution, concerns mainly the depollution applications. By against, all electrokinetic phenomena taking place almost at the same time, in some cases electro-osmosis will help to clean up at least partially while electromigration will not dehydrate. In this case we arranges to avoid drying out the anode or even lubricates the outside of the sliding anode with example of the bentonite sludge conventionally used during drilling.

To favor one or the other of the phenomena, it is possible to act on the electrode materials in particular deposits on one or other of the electrodes, on the connection of the electrodes, that is to say to choose a device with sliding anode or sliding cathode, on the adaptation of the material draining possibly present on the cathode and on injection of water, dissolved products or suspensions, at different levels of each electrode system. By example, the injection of suspensions, at different levels of the electrode system, can be used to lubricate a sliding anode.

The invention has been successfully tested on the dehydration of quarry lagoons and sludge unpolluted dredging.

It is also possible to use the invention for the dehydration of phosphate slime, slime coal, sludge, and / or drilling muds waste.

It is still possible to use the invention for the depollution by in-situ degradation of pollutants organic, for the depollution of water tables (nitrates, cyanides, metals, arsenic ... etc.) by ascent pollutants on the soil surface for disposal for the remediation of even clay soils by recovery of surface pollutants for disposal, or good for pumping deep water in areas arid.

Example

The following example serves to illustrate the invention without however, to limit its scope.

A test was carried out on site, with a system of given electrodes described hereinafter.

This is one of the essays of a ten-year campaign days that took place in July 2003 on a site, lagoon to clay mud base containing a majority of smectite. The goal was simply to show the feasibility of the invention. The tests were relatively short (2 hours). It was a question of comparing the effects of three factors: tension, length of the anode and the length of the isolated area. The effectiveness was evaluated by measuring the amount of water that was surfacing during the two hours with a single Electrode system in operation.

The maximum working depth for the tip of the anode was systematically 2 meters deep.

The activated part of the anode was 30 cm long and of diameter 20 mm with a point forming an angle of 15 ° with respect to the axis of the anode. Sections of 50 cm about were assembled by screwing. The material of the anode was titanium coated with metal oxides of which mostly iridium (type DSA).

The length of insulation was 97 cm, made of Poly material High Density Ethylene (HDPE) as a material heat shrinkable placed directly on the anode.

The cathode was about 150 cm long for a outer diameter of 48.5 mm, an inner diameter of 27 mm (insulation included), and stainless steel outer material food and PVC interior material (Poly Chloride Vinyl). The length of each cathode section was about 560 mm. This particular piece was complemented by additional parts internal cathode sealing and subjection from the cathode to the anode. The tight junction between cathode sections was provided by a flat seal in nitrile rubber.

The total length of the electrode system was about 350 cm.

The system was set up by hand and supported by a support that distributed its weight (about 15 kg) over 1 m ² .

The upper layer of lagoon (20 cm high) being relatively solid (following several months of drought), wide planks placed on the surface were enough to effectively support the operators. For do not have interaction with the dry layer of the lagoon a 30 cm hole was made and cased for collect the water as the electrode system went back up.

The initial concentration of the sludge is of the order of 40% after 6 years without addition of aggregate washing water in this one. No upwelling is observed after several hours in an identical hole without system electrode.

The volume of water raised is about 500 ml in two hours.

The amount of water recovered in two hours is characteristic of the zone of influence of the system of electrodes for a given configuration. On the other hand it is not representative of the amount of water that would be increased over a longer period, per unit of time. Within two hours, the process has everything just the time to initiate the rise of water (which comes about two meters deep), the nominal flow not yet reached. It would probably take several days for it to be reached.

The dimensions of the prototype will be pretty much those of the industrial version of the system electrode.

Claims (24)

A soil treatment method comprising the following successive steps: a) At least one substantially vertical at least partial depression in the ground (14) of at least one substantially straight coaxial monopolar electrode system (12; 13), said electrode system (12; 13) comprising at least one rod (2,3; 10,11) having at least one zone of first polarity (3a, 3b, 3c, 3d, 3e; 11a, 11b, 11c, 11d, 11e) and at least one insulating zone (2a, 2b, 2c, 2d; 10a, 10b, 10c, 10d), and at least one hollow tube (1,9) coaxial with said rod (2,3; 10,11), at least partially surrounding said rod (2,3; 11) and at least partially constituting a zone of second polarity (1; 9) capable of sliding at least partially around said rod (2,3; 10,11), said second polarity zone (1; 9) being placed in order to discover at least one zone of first polarity (3; 11) of said electrode system (12; 13), b) An electric field of the system (12; 13) of electrodes. The method of claim 1 further comprising at least one succession of the following successive steps: c) A deactivation of the electrode system (12; 13) by at least partial stopping of the electric field, d) a partial rise of the second polarity zone (1; 9) making it possible to discover at least one new zone of first polarity (3a, 3b, 3c, 3d, 3e) and / or at least one insulating zone (2a, 2b , 2c, 2d) e) An electric field reset of the electrode system (12; 13). Method according to one of the claims as said rod (2,3; 10,11) comprises a alternation of first polarity zones (3a, 3b, 3c, 3d, 3e, 11a, 11b, 11c, 11d, 11e) and zones insulators (2a, 2b, 2c, 2d, 10a, 10b, 10c, 10d), Method according to one of the claims preceding such as said electrode system (12; 13) once pushed into the ground (14) has one end above the surface (16) of the soil (14), at the minus one zone of second polarity (1; 9) in the ground (14), and a lower end having at least one zone of first polarity (3; 11) in the ground (14). Method according to one of the claims previous such as said second polarity zone (1; 9) is placed so as to discover the area of first polarity (3a; 11a) located closest to the end lower of said rod (2,3; 10,11). Method according to one of the claims with the dismantling of any area or part of second polarity zone (1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h) superfluous. Method according to one of the claims previous ones comprising at least partially pumping (5) liquid on the surface (16) of the soil (14). Method according to one of the claims in which the electrode system (12; 13) mainly consisting of assemblable parts called sections, the sinking of the system (12; 13) of electrodes in the soil (14) is carried out by a process progressive penetration and assembly of sections to each other, said process comprising at least one at least partial depressing step of at least minus one section, creating a set of section (s) at less partially depressed, followed by at least one step at least partial assembly of at least one other section at the set of stub (s) at least partially depressed already constituted. Method according to the preceding claim in which assembly comprises at least one screwing. Method according to one of the claims in which a plurality of systems (12; 13) of electrodes, said systems (12; 13) electrodes being practically all polarities identical, and we proceed to the different steps to each of said electrode systems (12; 13). Method of dehydrating soil and / or soil remediation comprising at least one method of soil treatment according to one of the claims preceding. Soil treatment device comprising at least minus one system (12; 13) of monopolar electrodes coaxial substantially rectilinear, said system (12; 13) of electrodes comprising at least one rod (2,3; 10,11) comprising at least one zone of first polarity (3a, 3b, 3c, 3d, 3e, 11a, 11b, 11c, 11d, 11e) and at least one zone insulation (2a, 2b, 2c, 2d, 10a, 10b, 10c, 10d), and at least one hollow tube (1; 9) coaxial with said rod (2,3; 10,11), at least partially surrounding said rod (2,3; 10,11) and at least partially constituting a second zone polarity (1; 9) able to slide at least partially around said shank (2,3; 10,11), said system (12; 13) of electrodes being more adapted to be activated. Device according to the preceding claim wherein said electrode system (12) is furthermore able to be sunk at least partially into the ground (14). Device according to one of claims 12 or 13 in which the second polarity zone (1) is adapted to be disassembled (1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h) at least partially. Device according to one of claims 12 to 14 comprising at least one system activation means (12; 13) electrodes. Device according to one of claims 12 to Wherein the electrode system (12; 13) is mainly consisting of assemblable parts. Device according to one of claims 12 to 16 where, when cathodic, the zone of first polarity (3a, 3b, 3c, 3d, 3e; 11a, 11b, 11c, 11d, 11e) or of second polarity (1; 9) includes stainless steel or non-stainless steel. Device according to one of claims 12 to 17 where, when it is anodic, the zone of second polarity (1; 9) or first polarity (3a, 3b, 3c, 3d, 3e; 11a, 11b, 11c, 11d, 11e) comprises titanium covered with at least one metal compound, precious or no. Device according to the preceding claim wherein said metal compound, precious or not, is selected from the group consisting of ruthenium, iridium, tantalum, tin, and antimony, in less partially oxidized or not, and mixtures thereof. Device according to one of claims 12 to 19 in which the hollow tube (1; 9) constituting at least partially the second polarity zone (1; 9) comprises at least one inner insulating zone on practically all its length. Device according to one of claims 12 to Further comprising at least one placement means, mechanical or manual, of at least one system (12; 13) electrode. Device according to one of claims 12 to 19 comprising a plurality of systems (12; 13) electrodes, said electrode systems (12; 13) being almost all of identical polarities. Device according to one of claims 12 to 22 for the implementation of a method according to one Claims 1 to 9. Use of a device according to one of claims 12 to 21 for soil dehydration and / or for soil remediation.

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