FR3115033A1 - Pontoon for effluent treatment basin - Google Patents

Abstract

Pontoon for effluent treatment basin Pontoon (32) for an effluent treatment pond (24), comprising: - a floating structure (34) defining at least one through opening in a vertical direction (V), and - at least one basket (78) fixed to the floating structure and extending vertically, at least part of the basket being intended to be immersed in the effluents, this part of the basket being at least partially delimited by an envelope allowing the effluents to to penetrate into and to leave an interior volume of the basket by convection movements, this part being further intended to contain a fixing substrate for micro-organisms suitable for carrying out a treatment of effluents, the envelope being intended to retain the fixing substrate in the interior volume, the through opening being adapted to allow access to the basket, and a visual inspection of all or part of the interior volume by the operator. Figure for the abstract: Figure 3

Description

Pontoon for effluent treatment basin

The present invention relates to a pontoon for an effluent treatment basin, The invention also relates to an effluent treatment unit incorporating at least one such pontoon, and a method corresponding to such a treatment unit

For example, it is known to treat a uranium ore by leaching in a sulfuric medium, sulfuric acid being relatively inexpensive.

However, most uranium ores contain uranium in the tetravalent state, or uranium(IV). This is the case, for example, of uraninite UO ₂ and coffinite USiO ₄ . In this tetravalent oxidation state, uranium is poorly soluble in sulfuric medium. Also, an oxidizing agent is added to the sulfuric solution used to carry out the leaching, in order to transform the uranium(IV) into hexavalent uranium, or uranium(VI), which is more soluble in a sulfuric medium. Then, the uranium is removed from the leaching effluents, and these are then recycled in the leaching process.

Currently, the most widely used oxidizing agent is ferric iron Fe(III), which may already be present in uranium ores or may be provided voluntarily by the operator. However, iron is more present in ores in the ferrous Fe(II) state than in the ferric Fe(III) state. In addition, the oxidation of uranium(IV) to uranium(VI) correlatively reduces iron from the ferric Fe(III) state to the ferrous Fe(II) state in the effluents. If these effluents were recycled as such, the kinetics of uranium extraction by leaching would be slow.

To solve this problem, the effluents are treated before recycling to oxidize the ferrous iron into ferric iron. To do this, it is known to add hydrogen peroxide (H ₂ O ₂ ) to the effluents, alone or mixed with sulfuric acid to form peroxymonosulfuric acid. However, the re-oxidation of ferrous iron to ferric iron by hydrogen peroxide or peroxymonosulphuric acid requires, for each mole of these compounds consumed, also the consumption of one mole of sulfuric acid. It is therefore costly in reagents.

Another method known per se consists in placing the effluents to be treated in the presence of microorganisms capable of bio-oxidizing the iron. These are in particular bacteria, for example chosen from the species Leptospirilium ferrooxidans, Leptospirillum thermoferrooxidans, Acidithiobacillus ferrooxidans, Ferrimicrobium acidiphilum, Ferroplasma spp., Acidimicrobium ferrooxidans . However, the implementation of these bacteria is delicate. Indeed, it leads to the development of a biomass in the form of more or less thick films, or of aggregates, tending to clog the substrates, the pipes or even the reactors in which the oxidation reaction takes place. This poses major maintenance or operating problems which are also reflected in high costs.

Thus, an object of the invention is therefore to allow less costly treatment of effluents.

To this end, the subject of the invention is a pontoon for an effluent treatment basin, the pontoon comprising:

- a floating structure adapted to float on the effluents, and defining at least one through opening in a vertical direction, the floating structure being adapted to allow movement of at least one operator on the pontoon in the vicinity of the through opening, and

- at least one basket fixed to the floating structure, the basket extending vertically from one side of the through opening, at least part of the basket being intended to be immersed in the effluents, this part of the basket being at least partially delimited by an envelope capable of allowing the effluents to enter and leave an interior volume of the basket by convection movements, this part being further intended to contain a fixing substrate for micro-organisms suitable for carrying out a treatment effluents, the envelope being intended to retain the fixing substrate in the interior volume, the through opening being adapted to allow access to the basket, and a visual inspection of all or part of the interior volume by the operator from the other side of the through opening in the vertical direction.

Such a pontoon makes it possible to implement a fixing support for micro-organisms, the possible fouling of which can be easily monitored by an operator through the through opening of the floating structure. In addition, if necessary, the through opening allows easy access to the interior volume of the basket, and therefore to unclog the fixing support by means known in themselves, or to replace it.

According to particular embodiments, the pontoon comprises one or more of the following characteristics, taken separately or in all technically possible combinations:

- the pontoon includes a guardrail arranged around the through opening;

- The basket comprises at least one gabion defining all or part of the interior volume; And

- the floating structure is adapted to form an island on the effluent treatment basin, the pontoon comprising an access bridge connected to the floating structure and intended to be connected to a perimeter of the effluent treatment basin.

The invention also relates to an effluent treatment unit comprising:

- at least a first treatment basin receiving the effluents,

- at least one pontoon as described above, the floating structure floating on the effluents, at least part of the basket being immersed in the effluents, the envelope allowing the effluents to enter and leave the interior volume of the basket by convective movements; And

- at least one fixing substrate for a plurality of micro-organisms, the fixing substrate being contained in the part of the basket immersed in the effluents, the envelope retaining the fixing substrate in the interior volume of the basket.

According to particular embodiments, the processing unit comprises one or more of the following characteristics, taken separately or in all technically possible combinations:

- the fixing substrate comprises at least one geotextile fabric;

- the geotextile fabric is essentially made of a material resistant to a solution having a pH between 1 and 2, for example polyethylene or polyamide;

- the fixing substrate has, flat, a surface greater than 200 m² ;

- the treatment unit comprises at least one aeration device placed at the bottom of the effluent treatment basin and suitable for injecting a gaseous mixture containing oxygen into the basin;

- the treatment unit further comprises at least one second basin, and at least one overflow system configured to lead the effluents from the basin into the second basin.

The invention also relates to a method implementing the processing unit.

The invention will be better understood on reading the following description, given solely by way of example and made with reference to the appended drawings, in which:

FIG. 1 is a schematic view, in perspective, of a processing unit integrating a pontoon according to the invention,

Figure 2 is a schematic top view of a first effluent treatment tank of the treatment unit shown in Figure 1,

Figure 3 is a schematic perspective view, substantially from the side and from above, of the first basin shown in Figures 1 and 2,

Figure 4 is a schematic perspective view, substantially from the side and from below, of the first basin shown in Figures 1 to 3, the walls of the first basin being transparent, and

Figure 5 is a schematic view, in perspective, of a basket and a railing shown in Figures 1 to 4, the floating support being omitted.

With reference to FIGS. 1 to 5, a processing unit 10 according to the invention is described.

As visible in Figure 1, the treatment unit 10 is adapted to treat effluents 12 and produce treated effluents 14. The treatment unit 10 is for example connected by a pipe 16 to a source of effluents 18.

The source of effluents 18 is for example a unit for leaching uranium ore in a sulfuric medium. This treatment unit is also suitable for recovering uranium dissolved in leachate. The effluents 12 to be treated are for example a desuranied acid solution, rich in ferrous iron. The ferrous iron concentration is for example greater than 12 g/litre.

The treatment unit 10 is suitable for oxidizing at least part of the ferrous iron present in the effluents 12 to ferric iron in the treated effluents 14.

The treatment unit 10 is for example connected by a pipe 20 to a storage 22 suitable for storing the treated effluents 14, for example for use in a uranium ore leaching unit.

Alternatively, line 20 leads treated effluent 14 directly to the leaching unit.

The treatment unit 10 comprises a first basin 24 for treating effluents provided to contain an expanse 26 of the effluents 12. The treatment unit 10 advantageously comprises a second basin 28, for example connected to the first basin 24 by a system of overflow 30 configured to lead the effluents 12 from the first basin 24 into the second basin 28.

The treatment unit 10 comprises a pontoon 32 comprising a floating structure 34 adapted to float on the expanse 26 of the effluents 12 to be treated.

The treatment unit 10 optionally comprises a coal silo 36 connected upstream to the pipe 16, and adapted to remove organic matter contained in the effluents 12.

The treatment unit 10 advantageously comprises a reactor 38, for example connected to the silo 36 to receive the effluents 12, and for example adapted to seed the effluents 12 with one or more species of bacteria 40 visible in Figure 5.

The processing unit 10 comprises for example a source of carbonate 42 connected to the first basin 24 by a pipe 44.

The treatment unit 10 advantageously comprises a system 46 for controlling the pH of the effluents 12 in the first basin 24, and advantageously in the second basin 28.

The processing unit 10 advantageously comprises an aeration device 48 suitable for injecting a gaseous mixture 50 (FIG. 4) into the first basin 24 and optionally into the second basin 28.

The first basin 24 and the second basin 28 are for example connected in series thanks to the overflow system 30. The treatment unit 10 is for example configured so that the residence time of the effluents 12 to be treated is from a few hours to a few days in each of the basins, for example approximately 24 h. For example, the feed rate of the effluents 12 in the first basin 24 is approximately 15 m³per hour, the first basin 24 being for example adapted to contain approximately 360 m³effluents 12 forming the expanse 26.

The first basin 24 has for example an inverted and truncated pyramidal shape, forming a bottom 52 (FIG. 3) which is advantageously flat, and four inclined sides 54A, 54B, 54C and 54D. The first basin 24 defines a perimeter 56, for example rectangular or square.

According to variants not shown, the first basin 24 has other shapes. For example, the first basin 24 has the shape of a conventional swimming pool, or else the perimeter 56 is circular or elliptical.

Advantageously, the second basin 28 is structurally similar to the first basin 24. The second basin 28 is for example configured to serve as a secondary basin, in which the oxidation reaction of the effluents 12 ends. In the event of maintenance of the first basin 24, the second basin 28 can serve as the main effluent treatment basin 12, the pontoon 32, or else another, being installed floating above this basin.

The coal silo 36, the reactor 38 and the carbonate source 42 are for example located in a maintenance area 58 (FIG. 1) adapted to allow the circulation of one or more operators around these devices. The maintenance area 58 is for example connected by access paths 60, 62 respectively to the first basin 24 and to the second basin 28 to allow these operators to move between the maintenance area and these basins.

The coal silo 36 contains for example between a few m ³ and a few tens of m ³ of activated carbon, for example about 10 m ³ of activated carbon.

The reactor 38 has for example a capacity of approximately 30 m ³ of acid effluents 12. The reactor 38 is connected to the first basin 24 by a pipe 64 supplying the first basin.

The pH regulation system 46 comprises for example a source 66 of sulfuric acid, and a network of pipes 68 suitable for transporting the sulfuric acid from the source to the first basin 24, and advantageously to the second basin 28.

The carbonate source 42 is adapted to inject carbonates into the first basin 24 via the pipe 44, the carbonates being intended to generate gaseous carbon dioxide in contact with the acidic effluents 12 in the first basin.

The aeration system 48 comprises a source of compressed air 70, advantageously a plurality of injection devices 72 located in the basin 24, and a network of pipes 74 connecting the injection devices 72 to the source of compressed air . Advantageously, the aeration system 48 also includes injection devices (not shown) located in the second basin 28 and connected to the compressed air source 70 by the pipe network 74. The aeration system 48 is advantageously configured to create convection movements 76 (FIGS. 4 and 5) in the expanse 26 of effluents 12.

The injection devices 72 are known per se. They are, for example, of the OCTOAIR™ brand. The injection devices 72 are for example distributed over the bottom 52 of the first basin 24. The injection devices 72 are advantageously six in number, four of them being located respectively in corners defined by the bottom 52, and the other two being near the middle of the bottom, in top view.

In addition to the floating structure 34, the pontoon 32 comprises a plurality of baskets 78 (FIGS. 3 to 5) adapted to contain a fixing substrate 80 for the microorganisms 40, and optionally an access bridge 82 (FIGS. 2 to 4) connecting the floating structure 34 to the periphery 56 of the first basin 24. The pontoon 32 advantageously forms a modular structure that can be easily assembled and disassembled.

The pontoon 32 is advantageously essentially made of plastic material.

In this document, by “essentially made up of…”, we mean, for example, that the element concerned is made up, at least 95% by weight, preferably substantially 100% by weight, of the material(s) mentioned.

In top view (FIG. 2), the floating structure 34 has for example a generally rectangular or square shape. The floating structure 34 defines a plurality of through openings 84 in a vertical direction V. The floating structure 34 comprises a floor 86 advantageously formed by a plurality of floats 88 mechanically connected to each other horizontally.

The floating structure 34 advantageously comprises a plurality of guardrails 90 arranged around the through openings 84. The floating structure 34 advantageously comprises an outer guardrail 92 extending around the periphery of the floor 86 and extending by two side guardrails 94, 87 arranged on either side of the access bridge 82.

The floor 86 is advantageously formed by a single layer of floats 88. The floor 86 and the railings 90 define circulation corridors 98 (FIG. 2) adapted to allow one or more operators (not shown) to circulate between the openings crossings 84.

The floats 88 have, for example, a generally square shape when viewed from above.

The through openings 84 have, for example, a generally square shape when viewed from above. The through openings 84 are advantageously defined by the absence of one or more floats in the floor 86.

In the example shown, each of the through-openings 84 occupies a surface corresponding to nine floats 88. The through-openings 84 have, for example, an extension E1 in a direction X perpendicular to the vertical direction V corresponding to three floats 88, and an extension E2 in a direction Y perpendicular to the vertical direction V and to the direction X corresponding to three floats 88. The through openings 84 are for example twelve in number, and are for example aligned three by three in the direction X, and four by four in the Y direction.

The access bridge 82 advantageously comprises a plurality of floats 100 connected together in the same way as the floats 88 and forming a floor 102 in the continuity of the floor 86. The access bridge 82 extends for example in the direction Y, and has a width E3 in the direction X corresponding to three floats 100. The access bridge 82 is located in the extension of the access path 60.

Each of the baskets 78 extends vertically from one side (below) of one of the through openings 84. Each of the baskets 78 includes a portion 104 immersed in the expanse 26 of the effluents 12, and containing the fixing substrate 80 In the example shown, each of the baskets 78 is formed by a gabion 106, for example of parallelepipedal shape.

Each of the baskets 78 has for example an extension E4 along the vertical direction V of about two meters, the depth of the first basin 24 being for example about three meters.

Each of the baskets 78 has, for example, a substantially square horizontal section having an extension E5 of approximately 1.4 meters.

The gabion 106 is for example made up of a plurality of rods 108 defining an envelope 110 of the part 104 capable of allowing the effluents 12 to enter and leave an interior volume 112 of each of the baskets 78.

By “gabion”, we mean an aerated structure forming a cage for a content which is here the substrate for fixing 80 microorganisms 40.

Each of the through openings 84 is adapted to allow access to one of the baskets 78, and a visual inspection of the interior volume 112 by an operator in the vertical direction V, on the side opposite that of the baskets 78 with respect to the opening crossing 84 concerned, that is to say above the floor 86.

The fixing substrate 80 is for example formed by a plurality of tapes 114 of geotextile fabric.

In each of the baskets 78, the fixing substrate 80 has, when flat, a surface greater than 200 m ² , for example approximately 370 m ² .

The geotextile fabric is essentially made of a material that is chemically resistant to an acid medium whose pH is between 1 and 2, for example polyethylene or polyamide.

The microorganisms 40 are suitable for attaching to the attachment substrate 80. These include one or more species of bacteria, for example Leptospirilium ferrooxidans, Leptospirillum thermoferrooxidans, Acidithiobacillus ferrooxidans, Ferrimicrobium acidiphilum, Ferroplasma spp., or Acidimicrobium ferrooxidans .

The operation of the processing unit 10 will now be described. It illustrates a method according to the invention, implementing the processing unit.

The effluents 12 to be treated are injected into the first basin 24, in the example through line 64.

Advantageously, these effluents 12 to be treated have undergone a pretreatment, first in the coal silo 36, then in the reactor 38. According to a variant not shown, the reactor 38 does not intervene as a pretreatment, but for example punctually to reseed the area 26 of effluents 12 with micro-organisms.

Typically, the effluents 12 to be treated contain ferrous iron at a concentration of approximately 12 g/litre.

The pH control system 46 controls the pH of the expanse 26 of effluents 12 to, for example, approximately 1.2 in the first basin 24, and if necessary, also in the second basin 28. to do, sulfuric acid is distributed from the source 66 to the first basin 24, and possibly the second basin 28, via the network of pipes 68.

Carbonates from the source 42 are introduced into the first basin 24 via the pipe 44. These carbonates react in an acid medium and form gaseous carbon dioxide, which is used as a source of carbon by the microorganisms 40 for their development. and allow the oxidation of ferrous iron to ferric iron in the effluents 12 from the first basin 24, optionally from the second basin 28. The pipe 44 can advantageously be a flexible part having perforations allowing escape of the carbonate solution so as to promote the formation of a plume of CO ₂ bubbles at the pipe/acid effluent to be treated interface.

The aeration system 48 injects the gaseous mixture 50 containing oxygen into the first basin 24, and if necessary into the second basin 28. The compressed air supplied by the source 70 circulates in the pipe system 74 to be distributed in the injection devices 72. The injection of the gaseous mixture 50 into the effluents 12 aerates these effluents and causes the convection movements 76 in the expanse 26.

The pontoon 32 floats on the expanse 26. The floating structure 34 forms an island on the first basin, the access bridge 82 allowing an operator to access the floating structure from the perimeter 56 of the first basin, in particular by borrowing path 60 from maintenance area 58.

The envelope 110 delimiting the submerged part 104 of the baskets 78 retains the fixing substrate 80 in the interior volume 112 of the baskets, while allowing the effluents 12 to enter and leave the interior volume due to convection movements 76. Said otherwise, the envelope 110 of the baskets 78 is permeable to the effluents 12 to be treated under the effect of the convection movements 76, but does not allow the fixing substrate 80 to pass through it.

In contact with the micro-organisms 40 fixed on the fixing support 80, the ferrous iron of the effluents 12 is gradually oxidized to ferric iron in the first basin 24. The reaction, if necessary, is continued in the second basin 28.

The first basin 24, and advantageously the second basin 28 are for example maintained, by means known per se, at a temperature above 30°C.

After having stayed for a certain time in the first basin 24, the effluents 12 pass into the second basin 28 thanks to the overflow system 30. Then, after a stay in the second basin 28, the treated effluents 14 leave the unit processing unit 10 through line 20 and are for example stored in storage 22.

The operator or operators can move on the floor 86 of the floating structure 34 in the vicinity of the through openings 84. The through openings 84 allow physical access to each of the baskets 78 from above, which makes it possible to install, manipulate or to remove all or part of the fixing substrate 80 located in the baskets. The through openings 84 also allow a visual inspection of the interior volume 112, that is to say in particular of the fixing substrate 80, by the operator or operators from the upper side of each of the through openings 84.

Thanks to the characteristics described above, the pontoon 32 makes it possible to avoid clogging by micro-organisms 40, which makes the treatment of the effluents 12 less expensive, all other things being equal.

Claims (10)

Pontoon (32) for a basin (24) for treating effluents (12), the pontoon (32) comprising:
- a floating structure (34) adapted to float on the effluents (12), and defining at least one through opening (84) in a vertical direction (V), the floating structure (34) being adapted to allow circulation of at least at least one operator on the pontoon (32) in the vicinity of the through opening (84), and
- at least one basket (78) fixed to the floating structure (34), the basket (78) extending vertically from one side of the through opening (84), at least a part (104) of the basket (78 ) being intended to be immersed in the effluents (12), this part (104) of the basket (78) being at least partially delimited by an envelope (110) capable of allowing the effluents (12) to enter and leave an interior volume (112) of the basket (78) by convection movements (76), this part (104) also being intended to contain a fixing substrate (80) for micro-organisms (40) suitable for carrying out a treatment of effluents (12), the envelope (110) being intended to retain the fixing substrate (80) in the interior volume (112), the through opening (84) being adapted to allow access to the basket (78) , and a visual inspection of all or part (104) of the interior volume (112) by the operator from the other side of the through opening (84) according to the vertical direction (V). A pontoon (32) according to claim 1, further comprising a guardrail disposed around the through opening (84). Pontoon (32) according to claim 1 or 2, in which the basket (78) comprises at least one gabion (106) defining all or part (104) of the interior volume (112). Pontoon (32) according to any one of claims 1 to 3, in which the floating structure (34) is adapted to form an island on the basin (24) for treating the effluents (12), the pontoon (32) comprising a access bridge (82) connected to the floating structure (34) and intended to be connected to a perimeter (56) of the basin (24) for treating the effluents (12). Effluent (12) treatment unit (10) comprising:
- at least a first treatment basin (24) receiving the effluents (12),
- at least one pontoon (32) according to any one of claims 1 to 4, the floating structure (34) floating on the effluents (12), at least a part (104) of the basket (78) being immersed in the effluents (12), the envelope (110) allowing the effluents (12) to enter and leave the interior volume (112) of the basket (78) by convection movements (76), and
- at least one fixing substrate (80) for a plurality of microorganisms (40), the fixing substrate (80) being contained in the part (104) of the basket (78) immersed in the effluents (12), the envelope (110) retaining the fixing substrate (80) in the interior volume (112) of the basket (78). A processing unit (10) according to claim 5, wherein the attachment substrate (80) comprises at least one geotextile fabric. Treatment unit (10) according to Claim 6, in which the geotextile fabric consists essentially of a material resistant to a solution having a pH of between 1 and 2, for example polyethylene or polyamide. Processing unit (10) according to any one of Claims 5 to 7, in which the fixing substrate (80) has, when flat, a surface greater than 200 m ² . Treatment unit (10) according to any one of Claims 5 to 8, further comprising at least one aeration device (48) placed at the bottom of the basin (24) for treating the effluents (12) and adapted to inject a gas mixture (50) containing oxygen in the basin (24). Processing unit (10) according to any one of claims 5 to 9, further comprising:
- at least a second basin (28), and
- at least one overflow system (30) configured to lead the effluents (12) from the basin into the second basin (28).