IL202937A - Autonomous sea water purification device having alternating submerged filtration modules with multipiston low - pressure chambers - Google Patents

Abstract

The device for purifying sea water, comprises a pair of modules for filtration of seawater immersed in the marine medium, and a low pressure cylinder block comprising pressurizing valves with multiple sides and low pressure chambers. The filtration modules (10a, 10b) are connected to each other by a motorized transmission to move the modules according to alternative movements of plunging and rising in the marine medium in phase opposition. Each filtration module comprises a high pressure chamber equipped with an inlet for selective admission of sea water to be filtered inside the chamber. The device for purifying sea water, comprises a pair of modules for filtration of seawater immersed in the marine medium, and a low pressure cylinder block comprising pressurizing valves with multiple sides and low pressure chambers. The filtration modules (10a, 10b) are connected to each other by a motorized transmission to move the modules according to alternative movements of plunging and rising in the marine medium in phase opposition. Each filtration module comprises a high pressure chamber equipped with an inlet for selective admission of sea water to be filtered inside the chamber, a semi-permeable membrane for filtering sea water by reverse osmosis, an outlet for recollecting filtered water produced by each membrane contained in the chamber, an outlet for evacuation of salt concentrated seawater and pressurizing valves optionally moved in the chamber rotating along a longitudinal axis for determining a pressure of seawater at the inlet of each membrane. The multiple sides of the valves comprise receiving sides linked to pressurizing sides of the valves to move longitudinally. The receiving sides of the valves are arranged to be subjected to a hydrostatic pressure of the marine medium, and are associated with atmospheric gas tight chamber. The total usage area combined of different receiving sides of the valves has a value greater than the usage area of the pressurizing sides with which receiving sides are linked. A volume of each low-pressure chamber varies along the same direction as the high pressure chamber movement of the receiving and pressurizing sides of the valves. The low pressure cylinder block has an overall transversal dimension less than or equal to the overall transversal dimension of the filtration module with respect to the longitudinal axis. The filtration module delimits the high pressure chamber comprising the pressurizing sides. The different receiving sides of the valves connected to the pressurizing sides of the valves are horizontally directed parallel to the longitudinal axis of the high pressure chamber, are parallel to each other and to the pressurizing sides of the valves, and are orthogonal to the longitudinal axis of the high pressure chamber. The different receiving sides of the valves are fixed to each other to have a total transversal dimension less than the sum of transversal dimension of each receiving side of the valve. The different receiving sides connected to the same pressurizing sides of the valves are superimposed on each other in the longitudinal direction of axis of the high pressure chamber so that the transversal dimension of all receiving sides is equivalent to one of receiving sides. The receiving side and low-pressure side of the pressurizing valves are two opposite parallel sides of the same valves, which are directed horizontally for forming sealing in a cylinder to define the low pressure chamber. The low pressure chambers of filtration modules are connected to each other by a pipe, which balances pressure between the low pressure chambers without pressure drop. Each filtration module is suspended in the marine medium by a suspension cable from the motorized transmission. The longitudinal axis of each pressurizing side and corresponding receiving sides are vertical. The suspension cable is coupled to the valve, which delimits the low pressure chamber. Each low pressure chamber extends over the high pressure chamber. The motorized transmission is suitable for movement of each filtration module between the surface of the marine medium and a maximum depth of 10-30 m, and comprises a renewable energy source chosen from a wind pump and a panel of photovoltaic light sensor. A ratio of usage area of each receiving side on usage area of the pressurizing side is 20-60.

Description

" tti ^nitt imaia-^ai o>N_n oy ofi>nji» tryipv i>t> ^ »» ¾*a ιιηο^ watt Autonomous sea water purification device having alternating submerged filtration modules with multipiston low-pressure chambers Lopez (Societe par Actions Simplifiee) C.197822 AUTONOMOUS SEA- WATER PURIFICATION DEVICE HAVING ALTERNATING IMMERSED FILTRATION MODULES WITH MULTIPISTON LOW-PRESSURE CHAMBERS The invention relates to a sea-water purification device comprising at least one pair of sea-water filtration modules, especially for filtration by reverse osmosis, which are immersed in the marine environment and are connected to one another by a motorized transmission suitable for moving the filtration modules of each pair in alternating submerging and raising movements in the marine environment in phase opposition, each filtration module comprising: - a chamber, called the high-pressure chamber, equipped with: - at least one inlet for selectively (in certain operating phases) admitting sea- water for filtration into the high-pressure chamber, - at least one semi-permeable membrane for filtering sea-water by reverse osmosis, - at least one outlet for collecting the filtered water produced by each membrane contained in the high-pressure chamber, - at least one outlet for sea-water of greater salinity, - a piston face, called the pressurization face, which is arranged to have an effective surface area s and is able to move in the high-pressure chamber so as to determine the pressure of the sea-water at the inlet of each membrane, - a piston face, called the receiving face, which is arranged to be subjected to the hydrostatic pressure of the marine environment, said receiving face being integral in translation with said pressurization face and being associated with a tight chamber under a gaseous atmosphere, called the low-pressure chamber, so that the volume of the low-pressure chamber varies in the same direction as that of the high-pressure chamber under the effect of the movements of the pressurization face.

Many devices have been proposed for purifying sea-water by reverse osmosis, allowing fresh water to be produced by the desalination of sea- water. FR 2503129 describes the principle of a sea-water purification device as mentioned above which comprises reverse osmosis filtration modules equipped with a hydrostatic pressure amplification system. When a filtration module has descended to a sufficient depth, the receiving face, which is subject to the hydrostatic pressure, causes a reduction in the volume of the low-pressure chamber and a movement of the pressurization face in the high-pressure chamber so as to reduce the volume thereof, thus applying a high inlet pressure which allows the filtration membranes to work by reverse osmosis. Such a device makes it possible to obtain a pressure that is sufficient (the pressure must be at least 50 hPa, ideally 60 hPa) to supply the membranes with sea-water, for a maximum depth of submersion of the modules that is limited to a reasonable value, theoretically of the order of from 10 to 30 m.

Nevertheless, the practical operation of such a device has hitherto encountered a number of difficulties. Firstly, the flow rate of filtered fresh water that is delivered has been found to be insufficient to permit acceptable cost effectiveness of the device, given its initial installation cost. The flow rate of fresh water produced should in fact be sufficient to pay for the investment cost within a sufficiently short period of time.

However, the flow rate is limited firstly by the duration of the phases of submerging and raising each filtration module, which are carried out substantially under the effect of gravity and are hindered by hydrodynamic friction. The latter factor is proportional to the characteristic surface area (that is to say the overall area of its horizontal cross-section) of the submerged filtration module. However, the use of a hydrostatic pressure amplification system, which allows the maximum depth of submersion to be limited, also has the effect of inducing a cross-section of the receiving face that is as large as possible and therefore of increasing the horizontal cross-section of the filtration module accordingly. Consequently, if the maximum depth of submersion is to be limited (for reasons of practical feasibility and in order to reduce the duration of the phases of submerging and raising), it is necessary to have a high pressure amplification ratio, and therefore a large cross-section of the filtration module, which in reality prevents a sufficient speed from being achieved during the phases of submerging and raising. Conversely, if the value of the horizontal cross-section of the filtration module is limited, the speeds of movement in the marine environment may be sufficient but, on the one hand, the duration of the phases of submerging and raising remains considerable owing to the distance that is to be covered and, on the other hand, the flow rate supplied at each filtration step is insufficient.

In addition, the flow rate of filtered water that is produced is also linked to the filtration speed in each filtration step, once the minimum pressure for filtration by reverse osmosis has been reached in the high-pressure chamber. However, with the devices known hitherto, that speed is not optimal and is limited in particular at the end of travel by the return members which must be provided for returning the low-pressure chamber to the maximum volume position when the filtration module returns to the surface.

Accordingly, the inventor has found that the total flow rate (over one complete operating cycle of the device) of filtered water that is produced by the devices known hitherto is not sufficient to enable them to be used on an industrial scale with acceptable cost effectiveness.

The invention therefore aims to remedy those disadvantages by proposing an improved sea-water purification device, especially using the phenomenon of reverse osmosis, for the desalination of sea-water, which device produces an improved total flow rate of filtered water for an equivalent investment cost.

More particularly, the invention aims to propose such a sea-water purification device with which, for a given flow rate of filtered water, the duration of the steps of submerging/raising the filtration modules is reduced. Yet more particularly, the invention aims to propose such a sea-water purification device with which, for a given flow rate of filtered water, the duration of the reverse osmosis filtration step at the maximum depth of submersion is reduced. In other words, the invention aims to propose a sea-water purification device with which, for a given duration of an operating cycle (step of submerging/raising and step of reverse osmosis filtration), the flow rate of fresh water that is produced is increased.

The invention aims more particularly to propose such a sea-water purification device with which the maximum depth of immersion of the filtration modules can be limited in real terms to a value of from 10 m to 30 m.

The invention aims more particularly to propose such a device which does not have a mechanical return member or any return member.

The invention aims also to propose such a sea-water purification device which is simple and inexpensive to manufacture and maintain. The invention aims also to propose such a device which is very reliable and which operates totally autonomously (allowing it to be used especially in developing countries). In particular, the invention aims to propose such a device which is able to operate with a motorized transmission supplied with power by at least one renewable energy source (wind, sun, etc.). (Throughout this text, the term "motorized" refers generally to any device that delivers mechanical energy).

To that end, the invention relates to a sea-water purification device comprising at least one pair of sea-water filtration modules, especially for filtration by reverse osmosis, which are immersed in the marine environment and are connected to one another by a motorized transmission suitable for moving the filtration modules of each pair in alternating submerging and raising movements in the marine environment in phase opposition, each filtration module comprising: - at least one chamber, called the high-pressure chamber, equipped with: - at least one inlet for selectively admitting sea-water for filtration into the high- pressure chamber, - at least one semi-permeable membrane for filtering sea-water by reverse osmosis, - at least one outlet for collecting the filtered water produced by each membrane contained in the high-pressure chamber, - at least one outlet for sea- water of greater salinity, - at least one piston face, called the pressurization face, which is arranged to have an effective surface area s and is able to move in the high-pressure chamber in translation according to an axis, called the longitudinal axis, so as to determine the pressure of the sea-water at the inlet of each membrane, characterised in that the device comprises at least one low-pressure cylinder block having a plurality of piston faces, called receiving faces, which are connected to at least one pressurization face so as to be able to move it in longitudinal translation, the various receiving faces being so arranged that they are all subjected to the hydrostatic pressure of the marine environment, the cumulative total effective surface area S of the various receiving faces having a value greater than the effective surface area s of said pressurization face to which they are connected, each receiving face being associated with at least one tight chamber under a gaseous atmosphere, called the low-pressure chamber, of the low-pressure cylinder block so that the volume of each low-pressure chamber varies in the same direction as that of the high-pressure chamber under the effect of the simultaneous translational movements of the receiving faces and of said pressurization face.

Consequently, each filtration module can comprise a number of receiving faces all connected to the same pressurization face, which is suitable for obtaining an appropriate pressure amplification ratio permitting filtration by reverse osmosis at a given maximum depth, and the various receiving faces can be so arranged relative to one another that the transverse cross-section of the filtration module in the horizontal direction remains limited to an admissible value which does not substantially impair the movement of the filtration module during its alternating submerging and raising movements in the marine environment. Furthermore, said maximum depth remains at a sufficiently low value. The invention accordingly makes it possible, in combination, on the one hand to increase the value of the fresh water flow rate produced by each filtration module in each reverse osmosis filtration step (when the filtration module is submerged) and on the other hand to reduce considerably the duration of the phases of submerging and raising, so that the duration no longer represents a limitation to the value of the total flow rate of fresh water that is produced.

Advantageously and according to the invention, the various receiving faces connected to the same pressurization face are so arranged relative to one another that the low-pressure cylinder block has a total overall transverse space requirement, relative to the longitudinal axis, that is less than or equal to the overall transverse space requirement of the portion of the filtration module that delimits the high-pressure chamber comprising said pressurization face. Accordingly, the overall horizontal transverse space requirement of a filtration module is determined by that of the portion containing the high-pressure chamber, the latter being minimized so that it is just able to contain at least one reverse osmosis membrane and at least one pressurization face.

Accordingly, in a device according to the invention, for the same overall transverse space requirement of the high-pressure chamber relative to the longitudinal axis, the cumulative total effective surface area S of the various receiving faces associated with the same pressurization face can be increased, and therefore the flow rate delivered by that pressurization face can be increased and/or the depth at which reverse osmosis filtration takes place can be reduced. In particular, advantageously and according to the invention, the cumulative total effective surface area S of the various receiving faces is greater than the overall horizontal space requirement of the filtration module.

The relative configurations of the various receiving faces and of the associated pressurization face can vary, as can the means by which the mechanical connection between each receiving face and the corresponding pressurization face is produced. Advantageously and according to the invention, the various receiving faces connected to the same pressurization face are guided in translation parallel to the longitudinal axis.

More particularly, in a device according to the invention, the various receiving faces connected to the same pressurization face are advantageously parallel to one another and to the pressurization face and are orthogonal with respect to the longitudinal axis, and the various receiving faces are so arranged relative to one another that they have, relative to the longitudinal axis, a total transverse space requirement that is less than the sum of the transverse space requirements of each of the receiving faces. Advantageously and according to the invention, the various receiving faces connected to the same pressurization face are superposed on one another in the longitudinal direction of the longitudinal axis so that the transverse space requirement of the totality of said receiving faces is equivalent to that of a single one of those receiving faces. Accordingly, it is possible to multiply the receiving faces stacked along the longitudinal axis without increasing the transverse space requirement of the filtration module.

In addition, advantageously and according to the invention, each receiving face is integral in translation with a piston face, called the low-pressure face, which extends in the low-pressure chamber. Here too, the relative configurations of each receiving face and of the corresponding low-pressure face can vary.

Advantageously and according to the invention, the receiving face and the low-pressure face are two opposing parallel faces of the same piston which is guided tightly in translation in a cylinder so as to delimit therewith said low-pressure chamber. Furthermore, advantageously and according to the invention, the pressurization face has at least substantially the same orientation as each low-pressure face relative to the corresponding piston. In particular, advantageously and according to the invention, at least one pressurization face is connected to a low-pressure face by a rod which passes tightly through the corresponding low-pressure chamber. In this advantageous embodiment, said pressurization face, the receiving face and the low-pressure face are faces of the same movable piston formed in one piece or of an assembly of a plurality of pieces integral with one another.

In a preferred embodiment, advantageously and according to the invention, each receiving face of the device is a face of a piston delimiting the low-pressure chamber, the device comprises a piston and a low-pressure chamber for each receiving face, and the various pistons having the various receiving faces are connected in translation to one another and to said pressurization face. Consequently, when the filtration module is in the phase of submersion, each receiving face transmits the effect of the hydrostatic pressure to the corresponding piston, which is moved in translation and moves each corresponding pressurization face to which it is connected in translation in the high-pressure chamber, thus supplying each filtration membrane with sea-water for filtration under high pressure.

In addition, advantageously and according to the invention, the low-pressure chambers of the two filtration modules are connected to one another by at least one pressure equalizing pipe, each pressure equalizing pipe being suitable for allowing the pressures between the low-pressure chambers to be equalized substantially without energy loss. The pressure equalizing pipe on the one hand allows the expansion of each low-pressure chamber at the end of the phase of raising a filtration module to be facilitated, without requiring mechanical return means; conversely, however, it allows any harmful phenomenon of counterpressure at the end of the translational movement of the pressurization face of the submerged filtration module to be avoided. Each low-pressure chamber of the filtration module situated close to the surface in the process of expanding even creates a certain suction in the low-pressure chambers of the submerged filtration module, which facilitates movement of the pressurization face.

In addition, advantageously and according to the invention, each filtration module is suspended in the marine environment by at least one suspension cable of the motorized transmission, the longitudinal axis of each pressurization face and of the corresponding receiving faces being vertical. Each filtration module therefore has the general shape of an elongate cylinder having a vertical axis and hydrodynamic shapes, the submerging and raising movements of which in the marine environment are thus facilitated.

Advantageously and according to the invention, the suspension cable is coupled to a piston delimiting a low-pressure chamber. In that manner, the weight of the filtration module tends to bring about expansion of the low-pressure chambers. Accordingly, during raising of the filtration module, the weight thereof tends spontaneously to spread each low-pressure chamber in the sense of an increase of its volume, which generates a suction in the low-pressure chamber of the other filtration module which is in the process of descending, via the pressure equalizing pipe(s). That suction contributes to the movement of the pressurization face and of each receiving face of the filtration module that is in the process of descending.

Preferably, advantageously and according to the invention, each low-pressure chamber extends above the high-pressure chamber. Likewise, advantageously and according to the invention, each filtration module comprises a single low-pressure cylinder block located above a single high-pressure chamber which includes a single pressurization face having a vertical longitudinal axis. Other embodiments are possible, however, for example with a high-pressure chamber situated above low-pressure chambers, or with a high-pressure chamber interposed between two low-pressure cylinder blocks, or alternatively with a low-pressure cylinder block interposed between two high-pressure chambers.

Advantageously, in a device according to the invention, said motorized transmission is suitable for permitting movement of each filtration module between the surface of the marine environment and a maximum depth of immersion of from 10 m to 30 m, for example of the order of 20 m, and the ratio of the effective surface areas S/s (for a low-pressure chamber having 3 pistons) is from 6.6 to 20, but the ratio Si/s of the effective surface area Si of each receiving face to the effective surface area s of the pressurization face is from 20 to 60.

In addition, advantageously and according to the invention, said motorized transmission comprises at least one renewable energy source selected from a wind turbine and a solar panel.

A wind turbine can be used to drive directly at least one member such as a pulley of a mechanism for driving and/or suspending the two filtration modules of the same pair, with a mechanism for stopping the movement and reversing the direction of movement of each module at the end of the vertical travel (see, for example, FR 2503129). In that case, the device according to the invention is particularly simple, reliable and totally autonomous in its operation. In a variant, a wind turbine associated with a current generator and/or at least one solar panel supplies at least one battery suitable for permitting operation of an electric drive motor of at least one member such as a pulley of a mechanism for driving and/or suspending two filtration modules of the same pair. In that case, the movement of each module can be stopped, and its direction of movement reversed, by an automatic electric control device which changes the direction of rotation of the motor.

It is to be noted that, when the two filtration modules of the same pair are suspended from the same suspension cable, the two modules being identical and of the same weight, the energy required for moving the two filtration modules in their alternating submerging and raising movements in the marine environment in phase opposition is therefore very small.

The invention is applicable to all conceivable embodiments in terms of the hydrostatic pressure amplification means and the reverse osmosis filtration means of each filtration module. It is applicable especially to the embodiments described in FR 2503129. That being said, it is possible in particular to vary the number and the relative arrangements of the high-pressure and low-pressure chambers and of the pressurization and receiving faces.

A device according to the invention can, for example, be in the form of a fixed platform installed at sea or in the form of a tower or well which is installed on the shore and is to be filled with sea-water.

The invention relates also to a sea-water purification device having, in combination, all or some of the features mentioned hereinabove or hereinbelow.

Other objects, features and advantages of the invention will become apparent from reading the following description, which makes reference to the accompanying figures which show, by way of non-limiting examples, embodiments of the invention and in which: - Figure 1 is a general schematic diagram of a first embodiment of a device according to the invention in the form of a maritime platform, - Figure 2 is a general schematic diagram of a second embodiment of a device according to the invention in the form of a tower on the shore, - Figure 3a is a diagram in vertical section of an example of a filtration module of a device according to the invention, Figures 3b and 3c being diagrams similar to Figure 3a showing that module at the end of the submerging movement and of the raising movement, respectively, - Figure 4 is a diagram in vertical section of a second embodiment of a filtration module of a device according to the invention.

The device according to the invention shown in Figure 1 comprises a pair of sea-water filtration modules 10a, 10b, especially for filtration by reverse osmosis, which are immersed in the marine environment 11 and are connected to one another by a suspension cable 12 which comes out of the water and passes around an emerged pulley 13 which is mounted for rotation about a horizontal axis 14 on a platform 15 arranged above the surface 16 of the water. The two filtration modules 10a, 10b of a pair are identical.

The platform 15 is anchored so that it remains at least substantially immobile, as do the filtration modules 10a, 10b, relative to the seabed 17, for example by means of a post 18 which is set into the seabed 17 or by means of any other suitable anchoring system (for example an assembly of mooring bodies which are connected to the platform 15 by cables or chains, etc.).

The pulley 13 is coupled to an electric motor 19 which drives it in rotation alternately in one direction and then in the other, under the control of an automatic control device 35 with phases of stopping at the end of travel for a given period in order to allow filtration by reverse osmosis to take place in the filtration module 10a, 10b that is immersed to the maximum depth. The automatic control device 35 comprises a man-machine interface (screen, keyboard, etc.) and is programmable. It can be produced from a standard microcomputer.

The two filtration modules 10a, 10b are connected to one another by the suspension cable 12 and move in phase opposition during rotation of the pulley 13, one of the filtration modules 10a, 10b rising to the surface while the other filtration module 10a, 10b of the same pair is being submerged.

The electric motor 19 is supplied by a power source, for example a battery 20 which is recharged by a wind turbine 21 coupled to a generator 22 and/or by at least one solar panel 23. The electric motor 19 can include a reducer or any other suitable mechanical transmission allowing the pulley 13 to be driven at a speed that is sufficient for the phases of submerging and raising to be as rapid as possible, but not too great, in order to avoid any reduction of tension in the cable 12 (the speed at which the suspension cable 12 is driven remaining less than the maximum speed of submersion of each module 10a, 10b by gravity).

The platform 15 also carries a reservoir 24 for collecting the fresh water produced by each of the modules 10a, 10b, it being possible for all the various components carried by the platform 15, with the exception of the wind turbine 21 and the solar collectors 23, to be protected by a cowling or a building 36. In a variant, the reservoir 24 can be situated on land, especially if the platform 15 is close to the coastline.

Figure 2 shows a variant of such a device according to the invention in which the modules 10a, 10b are immersed in a column of sea-water 25 situated in a tower 26 arranged close to the shore. The top 27 of the tower forms a platform similar to the platform 15 of the first embodiment, which platform receives the same elements 13 to 23 described above. In another variant (not shown), the column of water can be situated in a well dug into the ground of the shore.

The value of these two variants as compared with the embodiment of Figure 1 is that the filtration modules 10a, 10b are no longer exposed to the natural environment, and in particular to sea currents, so that operation of the device can be more stable. The advantage of the first embodiment of Figure 1, however, is that it has a lower investment cost and that it is not necessary to provide means for drawing in the sea-water to be treated or means for draining the concentrated sea-water (of greater salinity).

Furthermore, in the variant of Figure 2, the collection reservoir 24 is situated at the bottom of the column of water 25, so that the recovery of the filtered fresh water is carried out by gravity. That being said, it must be noted that, in the first embodiment shown in Figure 1, the reverse osmosis filtration modules 10a, 10b provide the fresh water with a pressure that is largely sufficient to enable it to rise to the surface. Accordingly, in a variant not shown, the collection reservoir 24 can be formed by a column which extends vertically parallel to the tower 26.

The column of water 25 is supplied with sea-water from a pipe 28 and a pump 29, which can be coupled to the electric motor 19. Preferably, in the embodiment shown in Figure 2, the pipe 28 takes the sea-water from an intermediate sea-water storage tank 30 in the bottom portion of the tower 26, the tank 30 itself being supplied with sea-water by the tide and/or by a pipe 31 connected to a pump 34. In addition, there is advantageously provided an emptying pipe 32 which opens at the bottom of the column 25 and is equipped with an emptying valve 33. The emptying pipe 32 opens into the marine environment. When the valve 33 is open, the column 25 can be emptied, for example for cleaning purposes or in order to remove and renew the sea-water at the bottom of the column 25, the salinity of which tends to increase as fresh water is produced.

In addition, in a variant not shown, the pump 29 for supplying the column 25 can be replaced by a continuously running noria which is driven directly by the wind turbine 21, and the pump 34 for supplying the intermediate tank 30 can be omitted if the intermediate tank 30 is situated below the level of the sea and is supplied by a sloping pipe. This embodiment is particularly simple and allows the invention to be implemented using rudimentary mechanical technology, in the most remote regions of the planet. Such a device is extremely easy to repair with basic means.

Figures 3a, 3b, 3c show an embodiment of a filtration module 10a, 10b.

The filtration module has a generally oblong, hydrodynamic shape, which facilitates the submerging and raising movements thereof in the water. It therefore comprises a generally cylindrical, elongate body 40 made of metal or synthetic material and having a rounded bottom end 41 which can be ballasted in order to increase the tension on the suspension cable 12.

In the bottom portion, above the bottom end 41, the body 40 defines a high-pressure chamber 42 containing at least one reverse osmosis filtration membrane 43. In the example shown, the high-pressure chamber 42 contains two membranes 43. Each high-pressure membrane 43 has a bottom end 44 through which the fresh water filtered by said membrane 43 flows, the end 44 being connected to an outlet pipe 45 which passes through the body 40. The outlet pipe 45 is connected outside the body 40 to a flexible tube 46 for collecting the filtered water, the tube 46 itself being connected to the water collection reservoir 24.

Above the high-pressure chamber 42 there is mounted a low-pressure cylinder block 47 comprising a plurality of low-pressure chambers 48 arranged in series. The cylinder block 47 is formed of a plurality of hollow cylinder sections 49 of vertical axis which are stacked on top of one another axially and are separated into pairs by a separating plate 50. Each plate 50 is formed of a disk provided with a double thread, allowing a cylinder section 49 to be fixed on each side, the axial end of which cylinder section 49 is equipped with a corresponding internal thread, so as to enable the sections 49 to be stacked to form a cylinder of vertical axis. Each cylinder section 49 contains a piston 51 which is guided in vertical axial translation in that cylinder section 49.

Each low-pressure chamber 48 is delimited between one of the fixed plates 50 and the piston 1 guided tightly in vertical axial translation in one of the cylinder sections 49.

Each piston 51 is generally disk-shaped and has a first main face, called the low-pressure face 52, which delimits the low-pressure chamber 48, and a second, opposing main face, called the receiver face 53, which, together with the cylinder section 49 extending above that receiver face 53 and, where appropriate, together with the separating plate 50 situated immediately above, forms a chamber, called the receiving chamber 54, which is subjected to the hydrostatic pressure of the marine environment.

Each cylinder section 49 is equipped, at its top end, with orifices 55 which pass through the wall of the cylinder section 49 in order to allow the free passage of sea-water, substantially without energy loss, from the outside (surrounding marine environment) into the receiving chamber 54, so that the receiving chamber 54 and the receiving face 53 are subjected to the hydrostatic pressure of the surrounding marine environment.

The various pistons 51 are connected integrally in vertical axial translation on the one hand to one another by linking rods 57 and on the other hand to a pressurization piston 56 which enters the high-pressure chamber 42.

Each linking rod 57 connects two adjacent pistons 51 together by passing axially, in a tight manner, through the plate 50 separating the two pistons 51. To that end, each separating plate 50 is equipped with a central axial through-bore. Each piston 51 can be provided with a double internal thread, that is to say with an internal thread on each of its faces 52, 53, for receiving the threaded end of such a rod 57.

Tightness between each piston 51 and the inside wall of the corresponding cylinder section 49 is provided by a gasket 58 arranged in a median peripheral groove of the piston 51. Tightness between each linking rod 57 and the plate 50 through which it passes is also provided by a gasket 60 arranged in a median groove which opens into the axial through-bore provided through the plate 50 for the passage of the linking rod 57.

The first, lowermost cylinder section 49 extends from a plate 63 of the body 40 delimiting at the top the high-pressure chamber 42. The first, lowermost low-pressure chamber 48 is therefore delimited between the portion of the top face 64 of the plate 63 that extends opposite the inside of the first cylinder section 49, and the lowermost low-pressure face 52 of the first piston 51.

The pressurization piston 56 is formed by a rod which passes axially through the top plate 63 of the high-pressure chamber 42 in a tight manner via a central bore provided in the plate 63. The pressurization piston 56 is connected to said first piston 51 on the side of its low-pressure face 52, so as to be integral in axial translation therewith and with the various pistons 51. To that end, the top end of the pressurization piston 56 is threaded so that it can be screwed into the internal thread of the low-pressure face 52, in the manner of a linking rod 57.The opposite free end 78 of the rod forming the pressurization piston 56 constitutes a pressurization face 80 which moves in the high-pressure chamber 42. Accordingly, the pressurization piston 56 is connected to each piston 51 in such a manner that the pressurization face 80 of the pressurization piston 56 is oriented on the same side as the low-pressure face 52 of each piston 51, namely horizontally downwards in the embodiment shown.

The pressurization piston 56 passes tightly through the plate 63 by virtue of a gasket 66 arranged in a peripheral groove which opens into the central bore formed through the plate 63.

The last piston 51 arranged at the top end of the cylinder block 47 is suspended from the suspension cable 12. The filtration module 10a, 10b is therefore thus suspended from the suspension cable 12 in the marine environment, with the longitudinal axis of translation of the pressurization piston 56 which extends vertically.

Each low-pressure chamber 48 is filled with a gas mixture, for example atmospheric air. The wall of each cylinder section 49 is equipped in its bottom portion, immediately above the separating plate 50 to which said cylinder section 49 is fitted, with at least one through-orifice 68 which communicates with a pressure equalizing pipe 69 extending outside the cylinder block 47. The orifice 68 therefore allows the gas contained in the low-pressure chamber 48 to circulate freely inside the pressure equalizing pipe 69. All the orifices 68 communicating with the various low-pressure chambers 48 are connected to the same pressure equalizing pipe 69. In addition, each orifice 68 is arranged in the corresponding low-pressure chamber 48 so as to be in communication with the chamber 48 whatever the position of the piston 51 in the cylinder section 49. In the example shown, the orifice 68 is arranged immediately above the separating plate 50, that is to say at the bottom end of the cylinder section 49.

The pressure equalizing pipe 69 is a flexible tube which can be passed along the suspension cable 12 and which connects the two filtration modules 10a, 10b so that the various low-pressure chambers 48 of the two filtration modules 10a, 10b are in communication with one another, at least substantially at the same gas pressure prevailing inside the various low-pressure chambers 48. The number and the diameter of the orifices 68, and the inside diameter of the pressure equalizing pipe 69, are suitable for allowing the pressures to be equalized between the various low-pressure chambers 48, substantially without energy loss. In the variants shown in Figures 1 and 2, the pressure equalizing pipe 69 extends along the suspension cable 12 and passes therewith around the pulley 13. To that end, the pulley 13 comprises a first, inner groove which receives the cable 12 and a second, outer groove having a larger width, which receives the pipe 69.

The outside diameter Dl of the body 40 in its part delimiting the high-pressure chamber 42 corresponds to the overall diameter of the filtration module and is greater than the outside diameter D2 of the low-pressure cylinder block 47. In that manner, the top plate 63 has, outside the cylinder block 47, sea-water inlets 70 which communicate with the inside of the high-pressure chamber 42. Each sea-water inlet 70 therefore enables the surrounding marine environment to be connected to the inside of the high-pressure chamber 42 and is closed off tightly by a top flap 71. Likewise, the bottom end 41 of the body 40 is equipped with outlets 72 for sea-water of greater salinity, which outlets likewise communicate with the inside of the high-pressure chamber 42. Each sea-water outlet 72 therefore enables the inside of the high-pressure chamber 42 to be connected to the surrounding marine environment and is closed off in a tight manner by a bottom flap 73.

The various flaps 71, 73 are integral with one another and are carried by a movable element 74 which extends inside the high-pressure chamber 42 and has a bottom horizontal plate 75 and a top horizontal plate 76, the latter having a central bore 77 through which the pressunzation piston 56 passes.

The movable element 74 is adapted so that the bottom free end 78 of the pressurization piston 56 comes into contact with the bottom plate 75 at the end of its downward movement path inside the high-pressure chamber 42, so as to push the plate 75 downwards and move the various flaps 71, 73 downwards, whereby the sea-water inlets 70 and the sea-water outlets 72 are opened (Figure 3b).

The movable element 74 is also adapted so that a collar 79 integral with the pressurization piston 56 comes into contact with the top plate 76 at the end of the upwards movement path inside the high-pressure chamber 42, so as to push the plate 76 upwards and move the various flaps 71, 73 upwards, whereby the sea-water inlets 70 and the sea-water outlets 72 are closed off (Figure 3c).

Consequently, the pressurization piston 56 controls the opening and closing of the sea-water inlets 70 and outlets 72.

The various receiving faces 53 of the various pistons 51 have a total effective surface area S subjected to the hydrostatic pressure of the surrounding marine environment. The total effective surface area S is equal to the sum of the effective surface areas SI, S2, ..., Sn of each receiving face 53.

The pressurization face 80 of the pressurization piston 56 has an effective surface area s corresponding to the surface area of the cross-section of the rod forming the pressurization piston 56.

The total effective surface area S of the various receiving faces 53 (that is to say the sum of the surface areas Si of each receiving face 53 receiving the hydrostatic pressure of the surrounding marine environment) is greater than the effective surface area s of the pressurization piston 56, and the ratio of the effective surface areas S/s is advantageously from 15 to 40, especially of the order of 30, and Si/s is advantageously from 5 to 15, especially of the order of 10.

The hydrostatic pressure to which the various receiving faces 53 are subjected is transmitted, with an amplification ratio corresponding to the ratio of the effective surface areas S/s, to the high-pressure chamber 42. When the filtration module 10a, 10b is being submerged and is descending into the marine environment, the hydrostatic pressure increases, as does the pressure in the high-pressure chamber 42.

When the filtration module 10a, 10b is immersed to a sufficient depth, the pressurization piston 56 therefore applies in the high-pressure chamber 42 a pressure having a value (typically greater than or equal to 60 hPa) sufficient to permit filtration by reverse osmosis through the membranes 43. The volume of each low-pressure chamber 48 varies in the same direction as that of the high-pressure chamber 42 under the effect of the movements of the pressurization piston 56. Accordingly, when the pressurization piston 56 of one filtration module 10a, 10b immersed to the maximum depth moves downwards and enters the high-pressure chamber 42, the volume of the various low-pressure chambers 48 decreases. In so doing, the pressure equalizing pipe 69 transmits a corresponding pressure increase to the low-pressure chambers 48 of the other filtration module 10b, 10a, which is then close to the surface (at the end of the raising movement). In that manner, the low-pressure chambers 48 of the other filtration module 10b, 10a increase in volume under the effect of the pressurization via the pressure equalizing pipe 69, which automatically returns the pressurization piston 56 to the top position.

Figure 3a shows the filtration module 10a, 10b when it is at the maximum depth of submersion, during the downward movement of the pressurization piston 56, filtered fresh water being produced at the outlet of the membranes 43.

Figure 3b shows the filtration module 3a, 3b at the start of its raising movement. In that position, the pressurization piston 56 has reached the end of its downward movement inside the high-pressure chamber 42, to come into contact with the bottom plate 75 while moving the movable element 74 downwards in order to open the inlets 70 and the outlets 72. In that manner, during the raising phase, sea-water passes through the high-pressure chamber 42 and sweeps the membranes 43. This sweeping effect is favourable to the operation of the reverse osmosis membranes 43. In addition, as it is raised, the filtration module 10a, 10b being suspended by the last piston 51, the entire weight of the filtration module 10a, 10b tends to cause an increase in the volume of the low-pressure chambers 48. Furthermore, as indicated above, that increase in volume is also caused by the pressure increase in the low-pressure chambers 48 resulting from the submersion of the complementary filtration module 10a, 10b of the same pair that is connected to the other end of the cable 12 and to the other end of the pressure equalizing pipe 69.

Figure 3c shows the filtration module 10a, 10b at the end of its raising movement (in the vicinity of the surface of the marine environment), the pressurization piston 56 being at the end of its upward movement and having pushed the top plate 76, and therefore the movable element 74, upwards until the flaps 71, 73 close off the sea-water inlets 70 and outlets 72, respectively. The low-pressure chambers 48 have their maximum volume. The high-pressure chamber 42 is filled with sea- ater ready to be filtered by the membranes 43. The filtration module 10a, 10b is therefore ready for submersion again.

Figure 4 shows a variant of a filtration module 10a, 10b in which the pressure equalizing pipe 69 serves as the suspension cable for each filtration module 10a, 10b. In addition, the pipe 69 is connected directly to the first piston 51 by a tight connection 85. Each of the linking rods 57 is formed by a hollow tube, and each piston 51 is equipped with a central through-passage 86, so that the air pressure is able to circulate from the connection 85 through the various linking rods 57 and through the various pistons 51. Each linking rod 57 additionally has at least one orifice 87 which opens at the top part of the linking rod 57 into the low-pressure chamber 48. The pressurization piston 56 is also hollow and is in communication with the passages formed in the pistons 51 and in the linking rods 57. Likewise, an orifice 88 opens at the top part of the pressunzation piston 56 into the first low-pressure chamber 48 arranged immediately above the plate 63 and the high-pressure chamber 42. In that manner, communication between the various low-pressure chambers 48 is established via the different orifices 87, 88, the hollow pressunzation piston 56, the various hollow linking rods 57 and the axial passages 86 in the pistons 1, as far as the pressure equalizing pipe 69. This embodiment is more compact and additionally makes it possible to minimize the risks of leakage through the portions of the pipe 69 that extend, in the first embodiment described above, along and on the outside of the cylinder block 47.

It is to be noted that in the embodiment shown in Figure 4, the pressunzation piston 56 is hollow over its entire length, that is to say it is formed by a hollow tube which is closed at its bottom end 78 by a tight welded stopper 89 forming the pressunzation face 80. In a variant not shown, it is possible to use a solid cylinder forming the pressurization piston 56, only an air communication passage in the top part being provided for connecting the pressure equalizing pipe 69 to the inside of the low-pressure chamber 48 via the orifice 88 and the central passage of the piston 51 to which the pressurization piston 56 is connected.

In addition, this second variant differs from the first in that the length of the pressurization piston 56 is limited to the length that is strictly necessary, which corresponds to the travel of the pistons 51 of the low-pressure cylinder block 47. Accordingly, the collar 79 is formed at the end 78 of the piston 56 by the stopper 89.

For a given maximum depth of submersion, the low-pressure cylinder block 47 comprising a plurality of pistons 51 and a plurality of low-pressure chambers 48 permits a corresponding increase in the flow rate of filtered water produced at each filtration step (that is to say at each submersion step) for a given travel of the pressurization piston 56 in the high-pressure chamber 42. The effective surface area s of the pressurization piston 56 can in fact be increased proportionally to the increase in the total effective surface area S receiving the hydrostatic pressure so obtained, while retaining the same pressure amplification ratio. Accordingly, in a device according to the invention, the amount of filtered water supplied at each submersion is optimised.

Alternatively, for a given effective surface area s and a given travel in translation of the pressurization piston 56, multiplication of the pistons 51 and of the low-pressure chambers 48 permits a corresponding reduction in the maximum depth of submersion at which the filtration modules 10a, 10b must be placed in order to carry out filtration by reverse osmosis. In practice, the maximum depth of immersion is advantageously from 10 m to 30 m, for example of the order of 20 m. It is to be noted that this depth is determined, as a function of the pressure amplification ratio produced by the surface area ratio S/s, relative to the median receiving face 53, or to the zone located at mid-height of the low-pressure block 47.

In addition, it is to be noted that this improvement in the production of fresh water is obtained without modification of the overall cross-section of the filtration module 10a, 10b, that is to say without modification of its hydrodynamic characteristics. On the contrary, the overall transverse space requirement of the filtration module is reduced. In particular, it is to be noted that each receiving face 53 has a diameter less than the diameter of the high-pressure chamber 42.

In practice, in a variant not shown, the overall transverse space requirement of the filtration module 10a, 10b can be limited to that which is just necessary for containing a reverse osmosis filtration membrane 43 and the various flaps 71, 73 and the movable element 74 for controlling the flaps. The membrane 43 can in fact be arranged at the bottom end of the body 40, and the piston 56 can move in a top axial end portion of the high-pressure chamber. The membranes 43 can then be replaced by a single equivalent membrane, of large diameter, which occupies the bottom axial end portion of the high-pressure chamber. Furthermore, in this variant not shown, the surface area s of the pressurization piston 56 can be maximum and occupy virtually the entire transverse cross-section of the high-pressure chamber 42.

The number of receiving faces 53, of low-pressure chambers 48 and of cylinder sections 49 stacked on one another is determined as a function of the value of the surface area S that is to be obtained. The number can be from 2 to 60, typically from 3 to 30. For example, if it is chosen to produce the filtration module 10a, 10b substantially in the form of a tube of minimum transverse cross-section for containing a filtration membrane 43 with a piston 56 of maximum diameter and receiving faces 53 whose diameter also corresponds substantially to that of the piston 56, Si/s = 1, and in order to obtain a ratio S/s of the order of Si/s = 1, thirty receiving faces 53 must be stacked (for a depth of 20 m).

The filtration module 10a, 10b can be integrated into a cartridge of generally oblong hydrodynamic shape. For example, in a variant not shown, a filter can be provided around the low-pressure cylinder block, in the prolongation of the cartridge delimiting the high-pressure chamber. Furthermore, each filtration module can also be guided in its submerging and raising movements by one or more vertical rails which extend in the marine environment. Inside the rails there can be arranged rings of combs/brushes which are stacked at a certain distance from one another and are intended to remove elements (which may cause blockages if allowed to accumulate) from the filter along the submerging and raising paths so as to form a self-cleaning system. It is additionally possible to provide a mechanism (not shown) for locking the movement of each pressurization piston 56 until a minimum hydrostatic pressure is reached. That mechanism can be of the type with hydrostatic control. In a variant, it can be controlled by the automatic control device 35 which controls the operation of the device. However, it is possible for such a mechanism to be omitted in the the invention, given that the filtration modules 10a, 10b have particularly efficient hydrodynamic shapes, increasing their speed of movement in the marine environment and therefore reducing the duration of the phases of submerging and raising accordingly.

In a variant also not shown, a device for controlling the pressure that prevails in the low-pressure chambers 48 can be provided, optionally with means allowing gas to be reintroduced into the low-pressure chambers 48 from the surface. For example, the pressure equalizing pipe 69 can be connected to a pipe that opens at the surface and is provided with a valve which can be opened in order to inject air into the pipe 69, at least one low-pressure chamber 48, and preferably each of the low-pressure chambers 48, being equipped with a calibrated valve allowing any water that has entered the low-pressure chamber 48 during the injection of compressed air into the low-pressure chamber 48 to be emptied out.

The device according to the invention can be the subject of many other variants of the embodiments shown in the figures and described above.

In particular, the device according to the invention can comprise a plurality of pairs of filtration modules 10a, 10b, which are connected together or independently of one another. Likewise, the invention is applicable to all the embodiments provided in FR 2503129. Each filtration module 10a, 10b can comprise a plurality of high-pressure chambers, and a plurality of pressurization pistons can be provided for each high-pressure chamber. One low-pressure chamber can receive a plurality of low-pressure pistons, that is to say can be associated with a plurality of receiving faces, provided the latter move in the same direction of variation of the volume of said low-pressure chamber. Conversely, at least one receiving face can be associated with a plurality of low-pressure chambers. Furthermore, each high-pressure chamber can be associated with a plurality of low-pressure cylinder blocks 47.

Likewise, the orientation of the various pistons 51, 56 can be different. For example, the various low-pressure pistons are not necessarily parallel to the longitudinal axis of the pressurization face. It is possible, for example, to provide low-pressure pistons that are movable radially. However, in that case, it is necessary to provide an angled mechanical transmission for moving the pressurization face on the basis of the movement of each piston. The number of receiving faces, the number of low-pressure chambers, the number of low-pressure cylinder block(s), the number of pressurization faces and the number of high-pressure chamber(s) of each filtration module can vary.

The motorized transmission formed by the suspension cable 12, the pulley 13 and the motor 19 can be replaced by any other form of motorized transmission which allows the filtration modules 10a, 10b to be moved in pairs in phase opposition.

In particular, in an advantageous variant, the motorization is formed only by a wind turbine which serves as a motor driven by a renewable energy source. The device is in that case a desalination device that operates totally autonomously, without means that may limit its lifetime (electric motor, pump, solenoid valve, electronics, etc.) and therefore having considerable reliability and a long working life.

In addition, it is possible to arrange a high-pressure chamber above a low-pressure cylinder block, or even interposed between two low-pressure cylinder blocks. The suspension cable 12 can be fixed not to one of the pistons 51 but directly to the body 40 of the filtration module 10a, 10b. Likewise, the pressure equalizing pipe 69 can be formed by a specific tube which extents wholly beneath the water and connects the low-pressure chambers. The automatic control device 35 can be replaced by a mechanism for automatically reversing the movements, with a mechanical device for controlling the stopping phases of the filtration modules 10a, 10b on the basis of transmission of the movement of the pistons and/or flaps to the reversal mechanism situated at the surface.

Claims (16)

1. A sea-water purification device comprising at least one pair of sea-water filtration modules (i#a", Vdtif which are immersed in the marine environment and are connected to one another by a motorized transmission 02 3, ^suitable for moving the filtration modules (J s, 1Gb† of each pair in alternating submerging and raising movements in the marine environment in phase opposition, each filtration module (1#2, \&bj comprising: - at least one chamber, called the high-pressure chamber j£42 , equipped with: - at least one inlet ( θ) for selectively admitting sea-water for filtration into the high-pressure chamber (42), - at least one semi-permeable membrane ( 3j or filtering sea-water by reverse osmosis, - at least one outlet (45) for collecting the filtered water produced by each membrane (43} contained in the high-pressure chamber (42)", - at least one outlet ¾ for discharging sea-water that is concentrated in terms of salinity, - at least one piston face, called the pressurization face ( Γ), which is arranged to have an effective surface area s and is able to move in the high-pressure chamber (Ai) in translation according to an axis, called the longitudinal axis, so as to determine the pressure of the sea-water at the inlet of each membrane { ), wherein the device comprises at least one low-pressure cylinder block (47) having a plurality of piston faces, called receiving faces (53^ which are connected to at least one pressurization face (^Tso as to be able to move it in longitudinal translation, the various receiving arranged that they are all subjected to the hydrostatic pressure of the marine environment, the cumulative total effective surface area S of the various receiving faces £H) having a value greater than the effective surface area s of said pressurization face (8ft) to which they are connected, each receiving face being associated with at least one tight chamber under a gaseous atmosphere, called the low-pressure chamber of the low-pressure cylinder block so that the volume of each low-pressure chamber varies in the same direction as that of the high-pressure chamber ( 2^under the effect of the simultaneous translational movement of the receiving faces j^3) and of said pressurization face (86).

2. The device as claimed in claim 1, wherein the various receiving faces (53^T connected to the same pressurization face are so arranged relative to one another that the low-pressure cylinder block (47) has a total overall transverse space requirement, relative to the longitudinal axis, that is less than or equal to the overall transverse space requirement of the portion of the filtration module (KTa, 10tf that delimits the high-pressure chamber (42^comprising said pressurization face £&Θ)Τ

3. The device as claimed in either claim 1 or claim 2, wherein the various receiving faces (S3 connected to the same pressurization face are guided in translation parallel to the longitudinal axis.

4. The device as claimed in any one of claims 1 to 3, wherein the various receiving faces (Sf) connected to the same pressurization face (80) are parallel to one another and to the pressurization face (8< and are orthogonal with respect to the longitudinal axis, and wherein the various receiving faces (Si are so arranged relative to one another that they have, relative to the longitudinal axis, a total transverse space requirement that is less than the sum of the transverse space requirements of each of the receiving faces (55).

5. The device as claimed in claim 4, wherein the various receivmg faces 5 ) connected to the same pressurization face (§d are superposed on one another in the longitudinal direction of the longitudinal axis so that the transverse space requirement of the totality of said receiving faces ^53) is equivalent to that of a single one of those receiving faces (55).

6. The device as claimed in any one of claims 1 to 5, wherein each receiving face ( γ is integral in translation with a piston face, called the low-pressure face ( 2), which extends in the low-pressure chamber ( 8).

7. The device as claimed in claim 6, wherein the receiving face (£3^ and the low-pressure face ( 2) are two opposing parallel faces of the same piston (^Twhich is guided tightly in translation in a cylinder (45) so as to delimit therewith said low-pressure chamber ( 8 .

8. The device as claimed in claim 7, wherein the pressurization face (80? has at least substantially the same orientation as each low-pressure face (52) relative to the corresponding piston

9. The device as claimed in any one of claims 1 to 8, wherein each receiving face (53) is a face of a piston (5^7 delimiting the low-pressure chamber ( ' wherein the device comprises a piston (^Tand a low-pressure chamber & Ίοτ each receiving face (53), and wherein the various pistons (JJ^Tnaving the various receiving faces ( }J are connected in translation to one another and to said pressurization face 0)^

10. The device as claimed in any one of claims 1 to 9, wherein the low-pressure chambers f of the two filtration modules (l#a. Wo) are connected to one another by at least one pressure equalizing pipe ( ), each pressure equalizing pipe (£9 being suitable for allowing the pressures (4% between the low-pressure chambers to be equalized substantially without energy loss.

11. The device as claimed in any one of claims 1 to 10, wherein each filtration module (1#ίζ lOkr) is suspended in the marine environment by at least one suspension cable {] of the motorized transmission, the longitudinal axis of each pressurization face QKJ) and of the corresponding receiving faces ξ) being vertical.

12. The device as claimed in claim 11, wherein the suspension cable 12^ is coupled to a piston (S^Tdelimiting a low-pressure chamber.

13. The device as claimed in any one of claims 1 to 12, wherein each low- pressure chamber (4# extends above the high-pressure chamber

14. The device as claimed in any one of claims 1 to 13, wherein each filtration module (ΐ ^Γ 10» comprises a single low-pressure cylinder block (4f) located above a single high-pressure chamber {∑f which includes a single pressurization face (,SOyhavi g a vertical longitudinal axis.

15. The device as claimed in any one of claims 1 to 14, wherein the cumulative total effective surface area S of the various receiving faces (53 ls greater than the overall horizontal space requirement of the filtration module (JjQ

16. The device as claimed in any one of claims 1 to 15, wherein said motorized transmission J^f l^T is suitable for permitting movement of each filtration module (Wa, 1Θ15) between the surface of the marine environment and a maximum depth of immersion of from 10 m to 30 m. The device as claimed in any one of claims 1 to 16, wherein the ratio Si/s of the effective surface area Si of each receiving face ζ53^το the effective surface area s of the pressurization face (ββ is from 20 to 60. The device as claimed in any one of claims 1 to 17, wherein said motorized transmission (J 1 ^comprises at least one renewable energy source selected from a wind turbine 2J^ and a solar panel (23^. For the Apptioonte REINHOLD COHN AND PARTNERS By i