Filtration system for a tank, and associated tank and filtration method

Abstract

The invention relates to a filtration system (12) for a tank (10) containing a liquid (20) emitting a polluted gaseous effluent (24) comprising at least one gaseous compound (26), said filtration system (12) comprising a covering device (28) intended to cover the tank (10). The covering device (28) comprises at least one first filtering portion (34) comprising a material having catalytic properties. The first filtering portion (34) is suitable for degrading and converting the gaseous compound (26) from the polluted gaseous effluent (24) so as to obtain a purified gaseous effluent (47), the filtration system (12) further comprising means (30) for mounting the covering device (28) which are suitable for mounting the covering device (28) on the tank (10) so as to position the first filtering portion (34) at a distance from the liquid (20).

Description

[0001] Filtration system for a pond, associated pond and filtration method

[0002] The present invention relates, according to a first aspect, to a filtration system for a basin containing a liquid emitting a polluted gaseous effluent comprising at least one gaseous compound, said filtration system comprising a cover device intended to cover the basin.

[0003] In particular, the basin is, for example, a treatment or retention basin of a treatment plant. The liquid is, for example, domestic, municipal, agricultural or industrial wastewater.

[0004] Among the gaseous compounds emitted by this type of pool, we find in particular odorous compounds or compounds harmful to humans beyond a certain threshold such as ammonia, hydrogen sulfide, or one or more volatile organic compounds. We also find greenhouse gases, such as nitrous oxide N2O, which contribute to degrading the environment, and in particular the atmospheric air.

[0005] Filtration systems are known in which the cover device comprises a rigid or semi-rigid cover resting on the peripheral contour of the basin. The gaseous effluents emitted by the liquid in the basin accumulate and are confined in the head space, also called the gaseous sky, delimited between the surface of the liquid and the cover to prevent them from spreading into the atmosphere.

[0006] However, some of these gaseous effluents are explosive under certain temperature and pressure conditions, which can raise safety concerns. In addition, the accumulation of these effluents in the headspace is likely to disrupt the biochemical reactions taking place in the basin.

[0007] Generally, devices are then implemented to extract effluent from the headspace to treat it in dedicated equipment external to the basin, the implementation of which is tedious and expensive.

[0008] An object of the invention is to propose a filtration system for a pool which makes it possible to effectively and easily treat the polluted gaseous effluent emitted by the liquid present in the pool.

[0009] To this end, the subject of the invention relates to a filtration system of the aforementioned type, in which the cover device comprises at least a first filtering portion comprising a material having catalytic properties, said first filtering portion defining a lower surface intended to be oriented towards the liquid of the basin and an upper surface, located opposite the lower surface, intended to be exposed to light radiation from at least one light source, said first filtering portion being adapted to degrade and transform the gaseous compound of the polluted gaseous effluent so as to obtain a purified gaseous effluent, the filtration system further comprising means for mounting the cover device adapted to mounting the cover device on the basin so as to arrange the first filtering portion at a distance from the liquid.

[0010] Thus, thanks to its photocatalytic properties, the first filtering portion allows the gaseous effluent to be treated by degrading and transforming the gaseous compound of the polluted effluent. The first filtering portion is arranged at a distance from the liquid to increase the efficiency of the photocatalytic reaction. The filtration system is particularly advantageous because it is passive and operates in particular thanks to natural light radiation which activates photocatalysis and the degradation of the adsorbed gaseous compound.

[0011] According to different embodiments, the filtration system further comprises one or more of the following features, taken individually or in all technically possible combinations:

[0012] - the covering device comprises at least one airtight and watertight portion delimiting at least one first through opening, the first filtering portion closing the first through opening;

[0013] - the cover device comprises at least one removable fixing member for removably fixing the first filtering portion to the waterproof portion;

[0014] - the mounting means are suitable for mounting the cover device on the pool in an airtight manner;

[0015] - the filtration system further comprises a lighting device comprising at least one upper light source adapted to emit light radiation directed towards the upper surface of the first filtering portion;

[0016] - the light radiation from the upper light source has a wavelength at least between 320 nm and 400 nm;

[0017] - the lighting device comprises at least one lower light source adapted to emit light radiation directed towards the lower surface of the first filtering portion, the light radiation from the lower light source preferably having a wavelength at least between 320 nm and 400 nm; - the lighting device comprises a control unit configured to control switching on or off of the upper light source, and preferably of the lower light source, as a function of a time and / or a date, or as a function of a concentration of gaseous compound;

[0018] - the filtration system further comprises a weather protection device comprising a waterproof, air-permeable and translucent membrane arranged on the upper surface of the first filtering portion, or comprising a translucent material arranged at a distance from the upper surface of the first filtering portion;

[0019] - the material having catalytic properties comprises an adsorbent layer adapted to adsorb the gaseous compound, and a photocatalytic layer comprising at least one photocatalytic element adapted to degrade and transform the gaseous compound adsorbed on the adsorbent layer; and

[0020] - the photocatalytic element is titanium oxide in rutile form.

[0021] The invention also relates, according to a second aspect, to a basin containing a liquid emitting a polluted gaseous effluent, the polluted gaseous effluent comprising at least one gaseous compound, said basin comprising a filtration system as described above, the cover device being mounted on the basin, the lower surface of the first filtering portion being oriented towards the liquid of the basin, the cover device, the surface of the liquid and at least part of a wall of the basin delimiting between them a head space containing the polluted gaseous effluent.

[0022] According to a particular embodiment, at least part of the first filtering portion extends in a plane forming a non-zero angle with the surface of the liquid.

[0023] According to a third aspect, the invention relates to a method for filtering a polluted gaseous effluent emitted by a liquid contained in a basin as described above, said method comprising the following steps: mounting the cover device on the basin with the mounting means so as to arrange the first filtering portion at a distance from the liquid, filtering the polluted gaseous effluent by passing said effluent through the first filtering portion so as to obtain a purified gaseous effluent.

[0024] According to a particular embodiment, the method further comprises a step of controlling a filtration efficiency of the first filtering portion, said step comprising the following sub-steps: measurement of a first concentration of gaseous compound of the polluted gaseous effluent in the head space, measurement of a second concentration of gaseous compound in the purified gaseous effluent, calculation of a parameter representative of the filtration efficiency as a function of the first concentration and the second concentration, replacement or cleaning of the first filtering portion as a function of the parameter representative of the filtration efficiency.

[0025] Other aspects and advantages of the invention will appear on reading the following description, given by way of example and with reference to the appended drawings, among which:

[0026] - figure 1 is a schematic section of a basin comprising a filtration system according to a first embodiment of the invention,

[0027] - figure 2 is a top view of the basin of figure 1,

[0028] - Figure 3 is a sectional representation of the material of the first filtering portion of the cover device of the filtration system of the pond of Figure 1,

[0029] - figures 4 to 5 are schematic representations, respectively in section, top view and in perspective of a filtration system according to a second embodiment of the invention,

[0030] - figure 6 is a schematic representation of a filtration system according to a third embodiment of the invention.

[0031] In Figures 1 and 2, a basin 10 according to a first embodiment is shown schematically, respectively in section and in top view.

[0032] The basin 10 comprises a filtration system 12 according to a first embodiment of the invention.

[0033] The basin 10 is intended to be placed on a floor. The basin 10 comprises a bottom wall 14 and a side wall 16 connected to the bottom wall 14. The side wall 16 and the bottom wall 14 delimit between them an interior volume 18 receiving a liquid 20. For example, as shown in FIG. 2, the bottom wall 14 has a rectangular shape and the side wall 16 comprises four rectangular walls 22 connected to each other and to the bottom wall 14. Alternatively, the bottom wall 14 is circular and the side wall 16 is a cylindrical wall of revolution with a circular base. It is understood that the bottom wall 14 and the side wall 16 of the basin 10 can have any shape.

[0034] Basin 10 is, for example, a treatment or retention basin for a treatment plant.

[0035] The liquid 20 is a liquid emitting a polluted gaseous effluent 24. By “polluted”, it is meant that the gaseous effluent 24 comprises at least one gaseous compound 26 that is unpleasant, odorous or harmful to humans beyond a certain threshold, such as ammonia, hydrogen sulfide, or one or more volatile organic compounds. Alternatively, the gaseous compound is a greenhouse gas, such as nitrous oxide N2O, which contributes to degrading the environment, and in particular atmospheric air. The concentration of gaseous compound 26 is, for example, between 0.001 pm and 100 ppm in the polluted gaseous effluent 24.

[0036] Liquid 20 is, for example, domestic, municipal, agricultural and / or industrial wastewater.

[0037] The basin 10 comprises, for example, one or more supply lines (not shown) intended to bring the liquid 20 into the interior volume 18 of the basin 10. The basin 10 further comprises, preferably, one or more extraction lines (not shown) intended to extract the liquid 20 from the basin 10.

[0038] According to the invention, the filtration system 12 comprises a cover device 28 and mounting means 30 for the cover device 28 adapted to mounting the cover device 28 on the basin 10, in particular on the perimeter of the basin 10.

[0039] The cover device 28, the surface of the liquid 20 contained in the basin 10 and a wall 16 of the basin 10, in particular the side wall 16, delimit between them a head space 32 containing the polluted gaseous effluent 24.

[0040] The cover device 28 comprises at least a first filtering portion 34 comprising a material 35 having photocatalytic properties.

[0041] In the example of Figures 1 and 2, the cover device 28 further comprises a second filtering portion 36 comprising a material 35 having catalytic properties. Preferably, the first filtering portion 34 and the second filtering portion 36 are made of the same material 35 having photocatalytic properties. Each first and second filtering portion 34, 36 comprises a lower surface 38 oriented towards the surface of the liquid 20 and an upper surface 40, opposite the lower surface 38 in an elevation direction Z.

[0042] Each of the upper surfaces 40 is intended to be exposed to light radiation from at least one light source.

[0043] In the first embodiment, the light source is the sun.

[0044] It is understood that, according to the invention, the covering device 28 may comprise any number of filtering portions 34, 36.

[0045] Advantageously, as shown in Figure 3, the material 35 having photocatalytic properties comprises an adsorbent layer 42 adapted to adsorb the gaseous compound 26 and a photocatalytic layer 44 comprising at least one photocatalytic element 46 adapted to degrade and transform the gaseous compound 26 adsorbed on the adsorbent layer 42, so as to obtain a purified gaseous effluent 47 downstream of the first filtering portion 34 and / or the second filtering portion 36.

[0046] By "purified gaseous effluent" is meant that the concentration of gaseous compound in said purified gaseous effluent 47 is lower than the concentration of gaseous compound 26 in the polluted gaseous effluent located in the head space 32 upstream of the first filtering portion 34.

[0047] The adsorbent layer 42 is oriented towards the liquid 20. The photocatalytic layer 44 is oriented opposite the adsorbent layer 42.

[0048] The photocatalytic layer 44 is intended to be exposed to light radiation from a light source. The light source is natural, in particular the sun, or artificial. The photocatalytic layer is intended to be oriented towards the light source.

[0049] In the first embodiment, the photocatalytic layer 44 is oriented directly towards the light source, in particular the sun, that is to say that there is no opaque obstacle between the photocatalytic layer 44 and the light source.

[0050] Preferably, the material 35 further comprises a first air-permeable support layer 48 attached to a lower surface of the adsorbent layer 42, and a second air-permeable support layer 50 attached to the upper surface of the adsorbent layer 42, between the adsorbent layer 42 and the photocatalytic layer 44.

[0051] The adsorbent layer 42 is for example a layer based on activated carbon. Alternatively, the adsorbent layer 42 is a layer based on non-woven coconut or wood fibers. The nature of the material of the adsorbent layer 42 is advantageously chosen according to its adsorption qualities and according to the load of polluted gaseous effluent 24 emitted by the liquid 20 of the basin 10.

[0052] The first support layer 48 and the second support layer 50 are preferably of the same nature and are, for example, non-wovens based on natural fibers and / or organic chemical fibers.

[0053] The photocatalytic element 46, also called a photocatalyst agent, is preferably a semiconductor solid, for example titanium dioxide (TiO2). Alternatively, the photocatalytic element 46 is an alkaline earth oxide, an actinide oxide or a rare earth oxide.

[0054] Photocatalysis is initiated by activating the photocatalytic element 46 by ultraviolet radiation causing electronic changes within the photocatalytic element 46 and leading, in the presence of the gaseous compound 26, to the creation of oxygenated or hydroxyl radicals on the surface of the photocatalytic element 46. These radicals attack the adsorbed gaseous compound 26 and, by a succession of electrochemical reactions, degrade the gaseous compound 26 until the final stage of oxidation.

[0055] Advantageously, the photocatalytic element 46 is titanium dioxide in rutile form. This is particularly advantageous because it gives the filtering portion 34, 36 hydrophobic properties which make it possible to avoid water saturation of the filtering portion 34, 36 due to bad weather, and thus to increase the efficiency of the photocatalytic reaction.

[0056] For example, the first filter portion 34 and the second filter portion 36 are made of a material such as those described in WO 0213950 A1.

[0057] Advantageously, the density and the thickness of the first filtering portion 34 and of the second filtering portion 36 are chosen by a person skilled in the art so that the cover device 28 induces a low pressure drop, for example between 10 Pa and 500 Pa. This makes it possible not to disturb the biochemical reactions which take place inside the basin 10.

[0058] For example, the densities of the first filtering portion 34 and of the second filtering portion 36 are between 100 g / m 2 and 1000 g / m 2

[0059] For example, the thicknesses of the first filtering portion 34 and the second filtering portion 36 are between 1 mm and 50 mm.

[0060] Preferably, as illustrated in Figures 1 and 2, the covering device 28 comprises at least one portion 52 impermeable to air and water. The impermeable portion 52 delimits at least one first through opening 54. The first filtering portion 34 closes the first through opening 54. By “close”, it is meant that the first filtering portion 34 completely closes the first through opening 54 forcing the polluted gaseous effluent 24 to pass through the first filtering portion 34.

[0061] In the example of Figures 1 and 2, the impermeable portion 52 further delimits a second through opening 56. The second filtering portion 36 closes the second through opening 56.

[0062] Preferably, the first filtering portion 34 and the second filtering portion 36 are kept taut respectively inside the first through opening 54 and the second through opening 56.

[0063] Preferably, the ratio between the surface area of ​​the filtering portion 34 or the filtering portions 34, 36 and the surface area of ​​the impermeable portion 52 is between 5% and 80%, typically between 15% and 60%, for example 50%. The ratio is chosen by a person skilled in the art depending on the pollutant load, the type of liquid 20 present in the basin 10, etc. to limit the pressure drop.

[0064] Advantageously, at least a portion of the first filtering portion 34 extends locally in a plane forming a non-zero angle with the surface of the liquid. This prevents the accumulation of debris on the first filtering portion 34 and facilitates the runoff of rainwater over the first filtering portion 34.

[0065] Preferably, the angle is between 30° and 60°, for example 45°. The angle is for example chosen according to the latitude of the location in which the basin 10 and the filtration system 12 are installed. More preferably, the first filtering portion 34 and / or the second filtering portion 36 are oriented towards the south. This makes it possible to favorably expose the filtering portions 34, 36 to solar radiation.

[0066] In the example shown in Figure 1, the cover device 28 has an outer surface 58 in contact with the ambient air of convex shape. This also facilitates the runoff of rainwater. Each filtering portion 34, 36 then has a curved outer surface forming a portion of the convex outer surface 58 of the cover device 28.

[0067] The waterproof portion 52 is for example rigid, that is to say that the waterproof portion 52 does not deform macroscopically for example during its installation on the basin. Alternatively, the waterproof portion 52 is flexible.

[0068] For example, the waterproof portion 52 is made of aluminum sheet or polyvinyl chloride. The polyvinyl chloride is preferably resistant to ultraviolet radiation.

[0069] Advantageously, the covering device 28 comprises at least one removable fixing member 60 for removably fixing each filtering portion 34, 36 on the impermeable portion 52.

[0070] By "removably attach" is meant that the filter portion 34, 36 can be secured to the impermeable portion 52 and detached from the impermeable portion 52 without the physical integrity of the filter portion 34, 36 and the physical integrity of the impermeable portion 52 being affected.

[0071] For example, the removable fastening member 60 is a hook-and-loop strip.

[0072] Alternatively (not shown), the removable fixing member 60 comprises an upper frame and a lower frame enclosing each of the filtering portions 34, 36. One of the upper frame and the lower frame is fixed to the impermeable portion 52. Advantageously, the first filtering portion 34 and the second filtering portion 36 are fixed in a sealed manner to the impermeable portion 52, that is to say that the removable fixing member 60 prevents the passage of the polluted gaseous effluent 24 at the junction between the first filtering portion 34 and the impermeable portion 52, and at the junction between the second filtering portion 36 and the impermeable portion 52.

[0073] Thus, to leave the headspace 32, the polluted gaseous effluent 24 passes only through the first filtering portion 34 and the second filtering portion 36.

[0074] The mounting means 30 of the cover device 28 are adapted to the mounting of the cover device 28 on the basin 10 so as to arrange the first filtering portion 34, and where appropriate the second filtering portion 36 in the example of FIG. 1, at a distance from the liquid 10 contained in the basin 10. In other words, the first filtering portion 34, and where appropriate the second filtering portion 36, are located away from the surface of the liquid 20, outside the liquid 20.

[0075] The mounting means 30 comprise, for example, rivets or bolts, one or more elastic or non-elastic straps. The mounting means 30 are known to those skilled in the art.

[0076] Preferably, the mounting means 30 make it possible to mount the cover device 28 in a sealed manner on the basin 10 so that the polluted gaseous effluent 24 cannot escape to the outside of the interior volume 18 at the junction between the basin 10 and the cover device 28.

[0077] Advantageously, the filtration system 12 comprises at least one pressure regulating member (not shown) of the polluted gaseous effluent 24 inside the head space 32. The regulating member is for example a pressure relief member, for example a valve, adapted to put the interior of the head space 32 into fluid communication with the exterior of the interior volume 18 when the pressure inside the head space 32 is greater than a predetermined threshold, for example between 10 and 100 Pa. This regulating member makes it possible not to modify the balance of the partial pressures of the basin process.

[0078] Alternatively or additionally, the filtration system 12 comprises at least one blowing fan (not shown) intended to blow outside air inside the head space 32 in order to dilute the concentration of gaseous compound 26 inside the head space 32 and optimize the concentration of gaseous compound 26, the flow rate of the polluted gaseous effluent 24 through the cover device 28, and / or the humidity level of the polluted gaseous effluent 24 to promote filtration. The filtration system 12 may further optionally comprise one or more members for homogenizing the polluted gaseous effluent 24. The homogenizing member is for example a fan located between the cover device 28 and the surface of the liquid present in the basin 10.

[0079] According to a particular embodiment, the filtration system 12 comprises at least one first sensor 62 configured to measure a first concentration of gaseous compound 26 in the headspace 32, i.e. in the polluted gaseous effluent 24, and at least one second sensor 64 configured to measure a second concentration of gaseous compound 26 in the purified gaseous effluent 47.

[0080] The filtration system 12 advantageously comprises a unit 66 for determining the filtration efficiency of the filtration system 12 connected to the first sensor 62 and to the second sensor 64. The determination unit 66 is configured to determine a filtration efficiency (E) as a function of the first concentration (Cl) and the second concentration (C2) measured.

[0081] For example, filtration efficiency (E) is calculated using the equation:

[0082] The determination of the efficiency is for example used to decide on the replacement or cleaning of the first filtering portion 34 and / or the second filtering portion 36, in particular when the efficiency is lower than a predetermined threshold, for example 50%.

[0083] Preferably, the filtration system 12 comprises at least one access walkway (not shown) allowing an operator to access at least the first filtering portion 34 for replacement and / or cleaning operations.

[0084] A method of filtering a polluted gaseous effluent 24 according to the invention will now be described.

[0085] The method firstly comprises filling the interior volume 18 of the basin 10 with a liquid 20 emitting a polluted gaseous effluent 24.

[0086] The cover device 28 is then mounted on the basin 10 with the mounting means 30 so as to arrange each filtering portion 34, 36 at a distance from the liquid 20.

[0087] The polluted gaseous effluent 24 emitted by the liquid 20 is then filtered by passing through the first filtering portion 34 and through the second filtering portion 36 so as to obtain on the other side of the cover device 28, that is to say in the atmosphere surrounding the basin 10, a purified gaseous effluent 47. Advantageously, the method further comprises a step of controlling the filtration efficiency of the first filtering portion 34 and / or of the second filtering portion 36.

[0088] This step comprises a first sub-step of measuring the first concentration of gaseous compound 26 of the polluted gaseous effluent 24 in the headspace 32 using the first sensor 62 of concentration of gaseous compound 26 and a second sub-step of measuring the second concentration of gaseous compound 26 in the purified gaseous effluent 47, downstream of the cover device 28 using the second sensor 64 of concentration of gaseous compound 26.

[0089] The method then comprises a step of calculating a parameter representative of the filtration efficiency of the cover device 28 as a function of the first concentration and the second concentration. For example, the representative parameter is calculated as described above.

[0090] The operator can then proceed to replace or clean the first filtering portion 34 and / or the second filtering portion 36 depending on the parameter representative of the filtration efficiency, for example if the efficiency E calculated previously is lower than a predetermined threshold.

[0091] Cleaning is carried out, for example, with steam and can be followed by drying.

[0092] Figures 4 to 5 represent a filtration system 12 according to a second embodiment of the invention.

[0093] In this embodiment, the filtration system 12 further comprises a light device 68 comprising at least one upper light source 70 adapted to emit light radiation oriented towards the upper surface of the first filtering portion 34.

[0094] Preferably, as illustrated, the light device 68 comprises an upper support structure 72 holding the upper light source(s) 70. The upper support structure 72 is located above the upper surface of the first filtering portion 34 in the elevation direction Z.

[0095] The light device 68 is particularly advantageous because it allows the activation by photocatalysis of the material 35 having photocatalytic properties and in particular of the photocatalytic layer 44. In the example illustrated, the light device 68 comprises two upper light sources 70 adapted to each emit light radiation oriented towards the upper surface of the first filtering portion 34.

[0096] Advantageously, the light device 68 comprises at least one lower light source 74 adapted to emit light radiation oriented towards the lower surface of the first filtering portion 34.

[0097] To do this, preferably, the lighting device 68 comprises a lower support structure 76 holding the lower light source(s) 74. The lower support structure 76 is located below the lower surface of the first filtering portion 34 in the elevation direction Z.

[0098] The light radiation from the upper light source(s) 70 and / or the lower light source(s) 74 has a wavelength at least between 320 nm and 400 nm, i.e. a wavelength included in the ultraviolet A radiation to activate photocatalysis (UVA). Each of the upper light sources 70 and / or lower light sources 74 may of course have a broader wavelength spectrum, for example a spectrum similar to that of natural light, i.e. between 200 nm and 2000 nm.

[0099] Advantageously, the upper light source 70 and / or the lower light source 74 is an electroluminescent light source (LED), or a fluorescent tube, or a xenon / mercury light source.

[0100] According to an advantageous embodiment, the light device 68 comprises a plurality of upper light sources 70 and / or a plurality of lower light sources 74. Preferably, the plurality of upper light sources 70 and / or the plurality of lower light sources 74 each comprise at least two light sources having distinct wavelength spectra. For example, the plurality of upper light sources 70 and / or the plurality of lower light sources 74 each comprise an electroluminescent (LED) light source, a fluorescent tube, and a xenon / mercury light source.

[0101] Preferably, the light power of each of the upper 70 and / or lower 74 light sources is chosen as a function of the pollutant load to be treated, i.e. as a function of the concentration of gaseous compound 26 in the polluted gaseous effluent 24. The light power, expressed in irradiance, is preferably between 1 and 1000 pW / cm 2 / nm. Advantageously, the light device 68 comprises a control unit 78 configured to control a switching on or off of the upper light source 70, and preferably of the lower light source 74, as a function of a time and / or a date, or as a function of a concentration of gaseous compound 26.

[0102] For example, the control unit 78 is configured to turn on the upper light source 70 and / or the lower light source 74 during the night and turn off the upper light source 70 and / or the lower light source 74 during the day. The control is carried out for example on the basis of predetermined times (for example sunrise and sunset) or on the basis of a brightness measured by a brightness sensor (not shown).

[0103] Alternatively or additionally, the switching on or off of the upper light source 70 and / or the lower light source 74 are controlled as a function of the first concentration of gaseous compound 26 measured in the headspace 32, preferably using the first concentration sensor 62. The control unit 78 is then configured to switch on the upper light source 70 and / or the lower light source 74 when the first concentration exceeds a predetermined threshold.

[0104] Preferably, the method comprises a step of controlling the switching on or off of the upper light source 70, and preferably of the lower light source 74, as a function of a time and / or a date, or as a function of a concentration of gaseous compound 26.

[0105] Figure 6 shows a filtration system 12 according to a third embodiment. This embodiment will be described by differences compared to the second embodiment.

[0106] In this embodiment, the filtration system 12 comprises a weather protection device 80 intended to protect the first filtering portion 34 and, preferably, the second filtering portion 36 from the weather.

[0107] In the illustrated example, the weather protection device 80 comprises a translucent material 82 arranged at a distance from the upper surface of the first filtering portion 34 and preferably at a distance from the second filtering portion 36. The material 82 covers and protects at least the first filtering portion 34 and / or the second filtering portion 36. Alternatively, the material 82 further covers at least a portion of the impermeable portion 52. The weather protection device 80 is for example a plate. By "translucent" is meant a material 82 with a light transmission rate of between 5% and 100%. The light comprises at least electromagnetic waves whose wavelength is between 320 nm and 400 nm. In other words, the material 82 allows at least a portion of the light spectrum in the UVA range to pass through so as to allow the photocatalysis reaction.In particular, the material 82 allows at least part of the spectrum of the light radiation from the light source to pass through.

[0108] The material 82 is, for example, polymethyl methacrylate acrylic, also called plexiglass. Alternatively, the material 82 is quartz glass.

[0109] The weather protection device 80 and the upper surface of the cover device 28, and in particular the upper surface of the first filtering portion 34 and / or the second filtering portion 36, delimit between them an air circulation channel 84 which allows the purified gaseous effluent 47 to circulate and escape into the atmosphere which surrounds the filtration system 12.

[0110] Alternatively (not shown), the weather protection device 80 comprises a waterproof and air-permeable membrane to allow the passage of the purified gaseous effluent 47, and translucent. The membrane is then arranged on the upper surface of at least the first filtering portion 34 in contact with the first filtering portion 34.

[0111] The weather protection device 80 makes it possible to prevent the first filter portion 34 from being saturated with water preventing the photocatalysis reaction.

[0112] Of course, according to a particular embodiment, the weather protection device 80 can form the upper support structure 72 of the lighting device 68.

[0113] Thus, the filtration system 12 according to the invention is particularly advantageous because the first filtering portion 34, thanks to its photocatalytic properties, makes it possible to treat the polluted gaseous effluent 24 by degrading and transforming the gaseous compound 26 of the polluted gaseous effluent 24. The first filtering portion 34 is arranged at a distance from the liquid 20 to increase the efficiency of the photocatalytic reaction. The filtration system 12 is particularly advantageous because it is passive and operates in particular thanks to natural light radiation which activates the photocatalysis and the degradation of the adsorbed gaseous compound 26.

Claims

Claims 1.- Filtration system (12) for a basin (10) containing a liquid (20) emitting a polluted gaseous effluent (24) comprising at least one gaseous compound (26) such as nitrous oxide, ammonia, hydrogen sulfide or a volatile organic compound, said filtration system (12) comprising a cover device (28) intended to cover the basin (10), characterized in that said cover device (28) comprises at least a first filtering portion (34) comprising a material (35) having catalytic properties, said first filtering portion (34) defining a lower surface (38) intended to be oriented towards the liquid (20) of the basin (10) and an upper surface (40), located opposite the lower surface (38), intended to be exposed to light radiation from at least one light source,said first filtering portion (34) being adapted to degrade and transform the gaseous compound (26) of the polluted gaseous effluent (24) so as to obtain a purified gaseous effluent (47), the filtration system (12) further comprising mounting means (30) of the cover device (28) adapted to mounting the cover device (38) on the basin (10) so as to arrange the first filtering portion (34) at a distance from the liquid (20)., 2.- Filtration system (12) according to claim 1, in which the covering device (28) comprises at least one portion (52) impermeable to air and water delimiting at least one first through opening (54), the first filtering portion (34) closing the first through opening (54). 3.- Filtration system (12) according to claim 2, wherein the cover device (28) comprises at least one removable fixing member (60) for removably fixing the first filtering portion (34) on the impermeable portion (52). 4.- Filtration system (12) according to any one of claims 1 to 3, in which the mounting means (30) are adapted to mount the cover device (38) on the basin (10) in an airtight manner. 5.- Filtration system (12) according to any one of claims 1 to 4, in which the filtration system (12) further comprises a light device (68) comprising at least one upper light source (70) adapted to emit light radiation directed towards the upper surface (40) of the first filtering portion (34). 6.- Filtration system (12) according to claim 5, in which the light radiation from the upper light source (70) has a wavelength at least between 320 nm and 400 nm. 7.- Filtration system (12) according to claim 5 or 6, wherein the light device (68) comprises at least one lower light source (74) adapted to emit light radiation oriented towards the lower surface (38) of the first filtering portion (34), the light radiation from the lower light source (74) preferably having a wavelength at least between 320 nm and 400 nm. 8.- Filtration system (12) according to any one of claims 5 to 7, in which the light device (68) comprises a control unit (78) configured to control a switching on or off of the upper light source (70), and preferably of the lower light source (74), as a function of a time and / or a date, or as a function of a concentration of gaseous compound (26). 9.- A filtration system (12) according to any one of claims 1 to 8, further comprising a weather protection device (80) comprising a waterproof, air-permeable and translucent membrane disposed on the upper surface (40) of the first filtering portion (34), or comprising a translucent material (82) disposed at a distance from the upper surface (40) of the first filtering portion (34). 10.- Filtration system (12) according to any one of claims 1 to 9, in which the material (35) having catalytic properties comprises an adsorbent layer (42) adapted to adsorb the gaseous compound (26), and a photocatalytic layer (44) comprising at least one photocatalytic element (46) adapted to degrade and transform the gaseous compound (26) adsorbed on the adsorbent layer (42). 11.- Filtration system (12) according to claim 10, in which the photocatalytic element (46) is titanium oxide in rutile form. 12.- Basin (10) containing a liquid (20) emitting a polluted gaseous effluent (24), the polluted gaseous effluent (24) comprising at least one gaseous compound (26), said basin (10) comprising a filtration system (12) according to any one of claims 1 to 11, the cover device (28) being mounted on the basin (10), the lower surface (38) of the first filtering portion (34) being oriented towards the liquid (20) of the basin (10), the cover device (28), the surface of the liquid (20) and at least part of a wall (16) of the basin (10) delimiting between them a head space (32) containing the polluted gaseous effluent (24). 13.- Basin (10) according to claim 12, in which at least a part of the first filtering portion (34) extends in a plane forming a non-zero angle with the surface of the liquid (20). 14.- Method for filtering a polluted gaseous effluent (24) emitted by a liquid (20) contained in a basin (10) according to claim 12 or 13, said method comprising the following steps: ° mounting the cover device (28) on the basin (10) with the mounting means (30) so as to arrange the first filtering portion (34) at a distance from the liquid (20), ° filtration of the polluted gaseous effluent (24) by passing said effluent (24) through the first filtering portion (34) so as to obtain a purified gaseous effluent (47). 15.- Filtration method according to claim 14, further comprising a step of controlling a filtration efficiency of the first filtering portion (34), said step comprising the following sub-steps: ■ measurement of a first concentration of gaseous compound (26) of the polluted gaseous effluent (24) in the head space (32), ■ measurement of a second concentration of gaseous compound (26) in the purified gaseous effluent (47), ■ calculation of a parameter representative of the filtration efficiency as a function of the first concentration and the second concentration, ■ replacement or cleaning of the first filtering portion (34) depending on the parameter representing the filtration efficiency.

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