Waterway equipped with a bubble screen, and a bubble screen therefor

Abstract

A waterway is provided through which water flows in a flow direction, the waterway having a bubble screen arranged at an angle to the water flow direction, the bubble screen extending substantially from one water guide element to another water guide element, a collection area is provided in a downstream portion of the bubble screen, and the bubble intensity in the downstream portion of the bubble screen is smaller than the bubble intensity elsewhere within the bubble screen.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates generally to bubble screens for allowing air to pass through liquids, particularly water. [Background technology]

[0002] Bubble screens for distributing and / or dispersing a fluid in a liquid are commonly known. Often the fluid is air and the liquid is a body of water, particularly a waterway such as a pond, lake, river, canal, stream, or part of a sea and / or ocean such as a bay, fjord, or inlet. Such bubble screens are utilized for a variety of purposes. For example, bubble screens are typically utilized to aerate water for aquaculture, bacterial and / or waste treatment, ice melting, or the like.

[0003] It has previously been proposed to use such bubble screens to recover plastic waste, i.e. plastics, from waterways. Although the upward thrust force provided by known bubble screens can help to bring the plastics to the surface, it has proven difficult in practice to effectively intercept the plastics before they reach, for example, the sea and / or ocean, in particular in a way that allows for efficient recovery of the plastics for further processing. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to mitigate one or more of the above-mentioned disadvantages while maintaining the above-mentioned advantages, in particular to provide an improved bubble screen flume configuration which is more efficient and allows for improved recovery of plastic waste from the flume. [Means for solving the problem]

[0005] To that end, the invention provides a waterway through which water flows in a flow direction, the waterway comprising a bubble screen arranged at an angle to the water flow direction, the bubble screen extending substantially from one water guiding element to another water guiding element, a downstream portion of the bubble screen being provided with a collection area, and the bubble intensity in the downstream portion of the bubble screen being less than the bubble intensity elsewhere within the bubble screen.

[0006] Generally, plastics move in the direction of the water flow and / or are transported in line with the water flow, particularly downstream, e.g., to a further waterway, sea or ocean. In some cases, at least a portion of the water, and therefore the plastics, may move in a substantially opposite flow direction, e.g., due to tidal influence or relatively strong winds. In such cases, a further collection area may be provided on the opposite part of the bubble screen with respect to the part where the collection area is provided. In this way, collection areas may be provided on both sides of the bubble screen, thereby allowing for improved recovery of plastics.

[0007] By providing the bubble screen at an angle to the water flow direction, the plastics caught by the bubble screen can be advantageously guided downstream and guided towards the collection area. When the bubble intensity in the downstream part of the bubble screen is lower than the bubble intensity elsewhere in the bubble screen, the plastics can be guided with less force towards the collector. In addition, the formation of vortices in the water in the vicinity of the collection area can be counteracted. Vortices are circular flows of water. By providing a lower bubble intensity in the downstream part of the bubble screen, the formation of vortices in the water, so-called whirlpool motion, can be at least partially reduced. Thereby, the accumulation and / or deposition of plastics in the vicinity of the collection area, in particular upstream, can be counteracted. In particular, this can facilitate the flow-through of plastics into the collection area.

[0008] Within the context of this patent specification, the term "water-guiding element" is to be interpreted as an element that at least partially bounds the water. For example, a water-guiding element may thus refer to ground that bounds the water, such as a bank, a river bank or a coast, but also to artificial or so-called man-made structures that bound the water, such as causeways, quays, wharves, banks, embankments, and in particular additionally to further bubble screens. These expressions in this context are understood to fall within the definition of the term "water-guiding element".

[0009] When the downstream end of the bubble screen is curved toward the collector, particularly convexly, the plastics can be gradually urged toward the collection area, thereby achieving a freer flow of the plastics toward the collection area. In this way, the recovery rate of the plastics from the waterway can be further improved.

[0010] The collection area may be a waterfront, for example a river bank, a seashore or a beach. Advantageously, the collection area may be equipped with a collector, in particular a water collection system, to further improve the recovery rate of the plastics. Furthermore, by providing the collection area with a collector, in particular a water collection system, the plastics may be recovered in a more controlled and convenient manner.

[0011] When the bubble screen is provided with at least one partial overlap, the presence and / or formation of gaps in the bubble screen can be counteracted, whereby losses of plastics that have slipped through the bubble screen can be reduced. In particular, when the at least one partial overlap forms a cascade in the bubble screen, the guidance of the plastics along the bubble screen towards the collection area and / or collector can be advantageously promoted.

[0012] By providing the bubble screen with a pressure source configured to supply compressed gas to the bubble screen, a relatively simple and cost-effective construction can be provided. Advantageously, the pressure source can be coupled to the upstream end of the bubble screen, allowing the pressure drop along the bubble screen in the downstream portion, particularly due to frictional forces, to be greater than elsewhere in the bubble screen. In this way, the bubble strength in the downstream portion of the bubble screen can be advantageously smaller than elsewhere in the bubble screen.

[0013] The present invention further provides a bubble screen device for ventilating liquids, in particular for use in waterways, having the features as described above, comprising a first part provided with a conduit arrangement with a plurality of openings along at least a part of the conduit arrangement, substantially each opening of the plurality of openings being configured to allow the passage of gas, a second part provided with a ballast module extending along at least a part of the first part and configured to submerge the bubble screen device in liquid, in particular underwater, and a ventilation module configured to adjust the ventilation capacity of a part of the conduit arrangement with the opening so that it is lower than the ventilation capacity elsewhere in the conduit arrangement with the opening.

[0014] The bubble screen device may be used to ventilate a waterway when the bubble screen device comprises a first portion provided with a conduit arrangement with a plurality of openings along at least a portion of the conduit arrangement, with substantially each of the plurality of openings configured to permit the passage of gas. In particular, substantially each of the plurality of openings may be configured to permit the passage of gas while acting to oppose the inflow of water therethrough into the conduit arrangement. The conduit arrangement may be substantially formed from a plastic material, such as, for example, polyvinyl chloride (PVC), low density polyethylene (LDPE), high density polyethylene (HDPE), or the like.

[0015] The bubble screen device may be conveniently placed in the waterway when the bubble screen device comprises a second portion provided with a ballast module configured to submerge the bubble screen in the liquid. The ballast module may comprise, for example, a ballast reservoir, a substantially solid member, and / or a fixed arrangement including at least one anchor. The ballast module may be formed from a material similar to and / or compatible with the material of the conduit arrangement. Additionally or alternatively, the ballast module may comprise one or more weights, such as metal weights, contained therein and / or connected thereto.

[0016] By providing an aeration module arranged to adjust the aeration capacity of a portion of the conduit arrangement with openings to be less than the aeration capacity of other portions of the conduit arrangement with openings, the bubble intensity induced by the portion of the bubble screen device during use can be less than the bubble intensity induced by the bubble screen device elsewhere. Thus, in particular, the bubble screen device can be provided in a waterway having a water flow direction such that the portion of the conduit arrangement with openings having a smaller aeration capacity corresponds to the downstream portion of the bubble screen device. In this way, during use, the plastic can be conveniently guided with less force towards a collection area such as a waterside, a collector and / or a water collection system. Additionally or alternatively, during use, the formation of vortices in the water at least in the vicinity of the collection area can be counteracted.

[0017] The venting module may comprise a constriction provided on the conduit arrangement arranged to restrict fluid flow through a portion of the conduit arrangement. In this way, the pressure in the portion of the conduit arrangement may be reduced, thereby reducing the venting capacity of that portion. Thus, during use, the bubble intensity in the corresponding portion of the bubble screen induced by the bubble screen device may advantageously be less than elsewhere in the bubble screen. In particular, the constriction may be provided as a valve, allowing control over the amount of constriction in the conduit arrangement. Additionally or alternatively, the constriction may be, for example, a porous membrane / material, a flange or a de laval nozzle (i.e., a converging-diverging nozzle).

[0018] The constriction may be provided on the inner circumference of the mantle surface of the conduit arrangement, such as a flange extending radially inward from the mantle surface along at least a portion of the circumference of the inner circumference. Additionally or alternatively, the constriction may be provided on the outer circumference of the mantle surface of the conduit arrangement, for example as a collar or clamping device. This may work particularly well when the conduit arrangement is made from a substantially flexible plastic material.

[0019] When the ventilation module comprises a diverging conduit section forming and / or fluidly connected to said portion of the conduit arrangement, the pressure in that portion of the conduit arrangement may be effectively reduced with respect to the pressure elsewhere in the conduit arrangement, such that the ventilation capacity of that portion is lower than elsewhere in the conduit arrangement comprising the opening, and in use the corresponding portion of the bubble screen may have a lower bubble strength than elsewhere in the bubble screen.

[0020] The ventilation module may comprise at least one textured surface extending at least partially along and on an inner periphery of a mantle surface of said portion of the conduit arrangement, the at least one textured surface being rough compared to an adjacent portion of the inner periphery of the mantle surface of the conduit arrangement.

[0021] Within the context of this patent specification, the term "textured surface" shall be interpreted as a surface portion that is rough compared to an adjacent surface portion of the inner circumference of the mantle surface of the conduit arrangement. Such an adjacent surface portion may in particular have a surface finish that is smooth compared to the textured surface. Such an adjacent surface portion may then be considered in the context of this application as a non-textured surface in particular. Such a smooth surface may, for reference, be as smooth as the normal (inner) mantle surface of a typical conduit arrangement. Thus, the textured surface may be rough compared to a surface having a normal surface finish of the mantle surface of a conventional conduit arrangement for aeration of waterways.

[0022] Advantageously, the ventilation module may comprise a temperature device configured to regulate at least the temperature inside the conduit arrangement. For example, the temperature device may comprise at least one insulating element and / or at least one heating element. In this way, by heating or insulating other places in the conduit arrangement, the pressure there may be higher compared to said part of the conduit arrangement. Thus, during use, the bubble strength of the corresponding part of the bubble screen may be increased with respect to said part of the conduit arrangement. Additionally or alternatively, at least one cooling element may be provided as a temperature device in said part of the conduit arrangement, for example.

[0023] Where the ventilation module comprises at least one further conduit segment as part of a conduit arrangement with a further plurality of openings along at least a portion of its length, substantially each opening of the further plurality of openings is configured to allow the passage of gas, and a portion of the at least one further conduit segment extends along a portion of the conduit arrangement with openings, whereby a portion of the further plurality of openings overlaps a portion of the plurality of openings, forming a relatively simple structure whilst acting against the possibility of gaps being formed in the bubble screen during use at the transition between the portion of the conduit arrangement and the further conduit segment. In this way, during use, plastics may be mitigated from slipping through the bubble screen and continuing downstream, for example towards a further waterway, sea and / or ocean.

[0024] When at least a portion of the conduit arrangement comprising an opening and at least a portion of at least one further conduit segment comprising an opening are arranged adjacent to one another, during use blocking of a portion of the bubble screen at and / or near the overlapping portion may be counteracted.

[0025] When the conduit arrangement includes a loop and a portion of the conduit arrangement is folded back on itself, a tortuous flow path through the conduit arrangement may be provided. In this way, a pressure drop may be advantageously achieved in said portion of the conduit arrangement during use. Additionally or alternatively, the portion of the conduit arrangement that is folded back on itself may provide additional aeration elsewhere in the bubble screen, as desired. For example, the bubble strength may be increased in a portion of the bubble screen that is in a deeper portion of the waterway during use.

[0026] The present invention further relates to a method for recovering plastic waste from a waterway, the method comprising the steps of: - providing a bubble screen between the water guiding element of the flow channel and another water guiding element, the bubble screen extending at an angle to the water flow direction of the flow channel; - capturing the plastic waste on the bubble screen and guiding it along the bubble screen towards a collection area in a downstream part of the bubble screen near the guiding element; - providing a bubble intensity in a downstream portion of the bubble screen that is less than the bubble intensity elsewhere within the bubble screen to mitigate the formation of vortices near the collection area and to prevent the accumulation and / or deposition of plastic near the collection area.

[0027] The invention will be explained more clearly on the basis of the exemplary embodiments represented in the drawings, which are merely schematic representations of embodiments of the invention given by way of non-limiting exemplary embodiments. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic perspective view showing a waterway provided with a bubble screen according to the present invention. [Diagram 2] FIG. 2 is a schematic top view of another flume provided with a bubble screen according to another aspect of the present invention. [Diagram 3] FIG. 2 is a schematic top view of a flume with a bridge provided with a bubble screen and a further bubble screen that intersect at a bridge piling according to an embodiment of the present invention; [Figure 4] FIG. 1 is a schematic perspective view showing a portion of a bubble screen device with a conduit arrangement and a ballast module according to one aspect of the present invention. [Diagram 5] FIG. 13 is a schematic perspective view of a portion of a bubble screen device provided with a diverging conduit section as a ventilation module according to a further aspect of the invention. [Figure 6] FIG. 13 is a schematic perspective view of a portion of a bubble screen device including an additional conduit segment as part of a conduit arrangement according to a still further aspect of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] In the drawings, the same or corresponding parts are designated with the same reference numbers.

[0030] FIG. 1 shows a waterway 1. The waterway 1 comprises water flowing in a flow direction F and has a width w extending substantially transversely to the water flow direction F. The waterway 1 comprises a bubble screen 2 arranged at an angle α with respect to the water flow direction F. The angle α shown here is about 45°, but any angle within the range of about 1° to 90° may be selected, such as between about 5° to 75° or between about 10° to 60°. Here, the bubble screen 2 extends from a dike as a water guiding element 3 to another dike as another water guiding element 3′. The downstream part 4 of the bubble screen 2 is provided with a collection area 5 with a water collection system 6 as a collector. Additionally or alternatively, the collection area 5 may be arranged as a waterside, such as a river bank, a coast or a seaside, where plastics for example wash ashore. The bubble intensity I of the downstream part 4 of the bubble screen 2 is smaller than the bubble intensity I of other parts of the bubble screen 2.

[0031] In use, plastic waste may be collected from the waterway by capturing the plastic waste on the bubble screen and guiding it along the bubble screen towards a collection area in a downstream portion of the bubble screen near the guide element, where a bubble strength in the downstream portion of the bubble screen that is less than the bubble strength elsewhere in the bubble screen may be provided to mitigate the formation of vortices near the collection area and prevent the accumulation and / or deposition of plastic near the collection area.

[0032] The particles, in particular the plastics P, move in the water flow direction F, in particular downstream, for example towards a further waterway, sea or ocean (not shown). The plastics P are intercepted by the bubble screen 2 and are gradually moved downstream towards the water collection system 6 at the collection area 5. In some cases, at least a part of the water, and thus the plastics P, may move in a substantially opposite flow direction, for example due to tidal influence or a relatively strong wind (not shown). In such cases, a further collection area, optionally together with a collector, may be provided at the opposite part of the bubble screen 2 to the downstream part 4 of the bubble screen 2, where the water collection system 6 at the collection area 5 is provided.

[0033] The downstream portion 4 of the bubble screen 2 is particularly convexly curved towards the collection area 5. However, any change, such as a step change or an abrupt change in the slope between the downstream portion 4 of the bubble screen with respect to the remaining portion of the bubble screen 2, may be contemplated.

[0034] At least one side 7 of the water collecting system 6, provided as a collector, comprises a mesh-like wall. The mesh-like wall is configured to sieve out particles, in particular plastics P, while allowing water to pass through. The mesh-like wall may have a sieve or so-called mesh size, for example, in the range between about 0.1 and 50 mm, for example between about 0.3 and 25 mm, or between about 0.5 and 20 mm. Additionally or alternatively, the mesh-like wall is configured to sieve out particles having a sieve or so-called screen size in the range between 0.1 and 1000 mm, such as having a screen size larger than about 0.3 mm or larger than about 0.5 mm. A screen size is to be interpreted as sieving out at least about 90% of particles having a particular particle size.

[0035] In an exemplary embodiment, gas, in particular compressed gas, is supplied to the bubble screen 2 from a pressure source 8 arranged in the downstream part 4 of the bubble screen 2. Advantageously, the pressure source 8 can be arranged at the upstream part of the bubble screen 2, i.e. on the side opposite to that shown here.

[0036] 2 shows a channel with a width W substantially transverse to the water flow direction F that is greater than the width w of the channel in FIG. 1. In this exemplary embodiment, the bubble screen 2 is provided with an overlap 9. In particular, the overlap 9 forms a cascade 10 at the transition T of the bubble screen 2. In this way, the gaps forming at the transition T of the bubble screen may be counteracted, thus mitigating the risk of particles, in particular plastics P, slipping through the bubble screen 2. In addition, downstream guidance of the plastics P along the bubble screen 2 may be promoted as the cascade 10 transitions downstream in the flow direction F.

[0037] FIG. 3 shows a waterway 1 in which a bridge B with a support pillar S is provided. In this exemplary embodiment, both the water guiding element 3′ and the further water guiding element 3″ are each formed by a different bubble screen 2. Here, the bubble screen 2 shown on the right hand side of FIG. 3 as seen in the water flow direction F extends substantially from the embankment 3 to the other bubble screen 2 shown on the left hand side of FIG. 3, which in turn extends substantially from the embankment 3 to the bubble screen 2. A collection area 5 is provided on the right hand side of the support pillar S, but could also be provided on the left hand side or at the end of the support pillar S. Particles, in particular plastics P, are intercepted by the bubble screen and are guided downstream towards the collection area 5, in which a water collection system 6 is provided.

[0038] 4 shows a bubble screen device 12 for venting liquids. The bubble screen device 12 comprises a first portion 13 provided with a conduit arrangement 14. In this exemplary embodiment, the conduit arrangement 14 is substantially formed from a plastic material, such as PVC, LDPE, HDPE, and the like. The conduit arrangement 14 comprises a plurality of openings 15 along at least a portion of the conduit arrangement 14. Each opening of the plurality of openings 15 is configured to allow the passage of gas, particularly while acting against the inflow of water.

[0039] The bubble device 12 further comprises a second portion 16 extending along the first portion 13, in particular substantially over the entire first portion 13. The second portion 16 is provided with a substantially solid ballast 17 as a ballast module. The ballast 17 is arranged to submerge the bubble screen device 12 in a liquid, in particular in water. Additionally or alternatively, the ballast module may comprise one or more anchor elements, for example arranged at a fixed or variable clearance along at least a portion of the first portion 13.

[0040] The bubble screen device 12 comprises an aeration module 18 arranged to adjust the aeration capacity of a portion 19 of the conduit arrangement 14 comprising the opening to be lower than the aeration capacity of other locations within the conduit arrangement 14 comprising the opening. In this exemplary embodiment, the aeration module 18 comprises a constriction 20. The constriction 20 is provided on the conduit arrangement 14 and arranged to restrict the fluid flow through the portion of the conduit arrangement 14. In particular, the constriction 20 is provided as a clamping device on the outer periphery 21 of the mantle surface 22 of the conduit arrangement 14. The aeration module 18 in this exemplary embodiment further comprises an increase in aperture size between two subsequent rows of the plurality of apertures 15. A first row of subsequent apertures 23 comprises apertures of a first size, and a second row of subsequent apertures 24 comprises apertures of a second size, which is larger than the first size. Of course, the aeration module 18 may be provided as either a constriction 20 or an increase in aperture size between the two rows.

[0041] The conduit arrangement 14 and the ballast 17 are fixed together, in particular they are fixed together by welding, additionally or alternatively other fixing means may be utilized, such as adhesives or snap connections.

[0042] Additionally or alternatively, a constriction 20 as a vent module 18 may be provided on the inner periphery 25 of the mantle surface 22 of the conduit arrangement 14 (not shown). For example, the constriction 20 may be an adjustable valve, or a flange or the like extending radially inward from the inner periphery 25 of the mantle surface 22.

[0043] FIG. 5 shows a bubble screen device 12 with a first part 13 provided with a conduit arrangement 14 with a plurality of openings 15 along it. Each opening is configured to allow the passage of gas, in particular while acting against the inflow of water. The bubble screen device 12 is further provided with a second part 16 including a ballast module 17 for submerging the bubble screen device in liquid. The bubble screen device 12 also comprises an aeration module 18. The aeration module 18 comprises a divergent conduit section 26 forming a part 19 of the conduit arrangement 14 having a lower aeration capacity than the rest of the conduit arrangement (not shown). Alternatively, the divergent conduit section 26 may be in fluid connection with said part 19 of the conduit arrangement 14.

[0044] In addition, the ventilation module 18 of FIG. 5 includes increased gaps between subsequent openings of the plurality of openings 15 such that the ventilation capacity of said portion 19 of the conduit arrangement 14 is lower than the ventilation capacity of other locations within the conduit arrangement that include openings (not shown).

[0045] FIG. 6 shows a bubble screen device 12 according to another aspect of the invention. In this exemplary embodiment, the ventilation module 18 comprises a further conduit segment 27 as part of the conduit arrangement 14. Also, more than one further conduit segment may be provided, for example, two, three, four or more (not shown). The further conduit segment 27 comprises a further plurality of openings 28 along at least a portion of its length. Similar to the plurality of openings 15 described above, each opening of the further plurality of openings 28 is configured to allow the passage of gas, in particular while acting against the inflow of water. A portion 29 of at least one further conduit segment 27 extends along a portion 30 of the conduit arrangement 14 comprising openings, such that a portion of the further plurality of openings 28 overlaps a portion of the plurality of openings 15. In this exemplary embodiment, an end of the conduit arrangement 14 is provided with a plug and gas is supplied from the opposite end. Also, the further end of the further conduit arrangement 27 is provided with a plug and gas is supplied from the upper right hand side of the schematic diagram. However, it may also be envisaged that the structures from which both the conduit arrangement 14 and the further conduit arrangement 27 extend are both provided with gas from the same end, for example from the lower left hand side of the schematic illustration, with the further conduit arrangement 27 extending beyond portion 30 of the conduit arrangement 14.

[0046] The portion 30 of the conduit arrangement 14 that comprises the opening and the portion 29 of the further conduit segment 27 are arranged adjacent to each other.

[0047] The bubble screen device 12 comprises an orienting module 31 arranged to orient at least a portion 30 of the conduit arrangement 14 comprising the openings and further orient at least a portion 29 of a further conduit segment 27 comprising a further plurality of openings 28. In this exemplary embodiment, the openings are particularly oriented by the orienting module 31 towards a side of the bubble screen device 12 such that, in use, the openings face upstream in the water flow direction. Additionally or alternatively, two or more orienting modules may be provided, for example, for each at least a portion of each further conduit segment. The orienting module may comprise a fixing element (not shown).

[0048] Preferably, any one or all of the exemplary embodiments described above may further comprise at least one pressure source in fluid connection with the conduit arrangement (not shown). In particular, the at least one pressure source is configured to supply compressed gas. Additionally or alternatively, the bubble screen device may be provided with a manifold configured to distribute gas supplied from the at least one pressure source to the conduit arrangement (not shown). In particular, when further conduit segments are provided as part of the conduit arrangement, the manifold may distribute gas supplied from the pressure source to the conduit arrangement and the further conduit segments.

[0049] It will be clear to those skilled in the art that the present invention is not limited to the exemplary embodiments depicted herein. Many variations are possible. For example, different aspects of the described venting module can be implemented separately or combined. Further conduit segments as part of the conduit arrangement may for example be in fluid connection with further pressure sources and / or be provided with openings having increased opening sizes with respect to the opening sizes of the plurality of openings. For example, substantially each or at least one opening of the (further) plurality of openings may comprise a nozzle, in particular as a venting module.

[0050] Such variations will be apparent to those skilled in the art and are considered to be within the scope of the invention as defined in the appended claims. [Explanation of symbols]

[0051] 1 Waterways 2. Bubble Screen 3, 3´ Water guide elements 4 Downstream section 5 Collection area 6 Collector 7 At least one side 8 Pressure Supply Source 9. Overlap 10. Cascade 11 Upstream end 12. Bubble Screen Device 13 First Part 14 Conduit arrangement configuration 15 Multiple openings 16 Second Part 17 Ballast Module 18 Ventilation Module 19 Part of the duct arrangement configuration 20 Stenosis 21 Outer circumference 22 Mantle surface 23 First row of subsequent openings 24 Second row of subsequent openings 25 Inner Circumference 26 Suehiro Pipe Section 27 Further Conduit Segments 28 More Multiple Openings 29 Part of at least one further conduit segment 30 Part of the conduit arrangement having an opening 31 Orientation Module F Flow direction P particles, especially plastic w width W is a wider width than width w T Change I Bubble Strength

Claims

1. 1. A waterway through which water flows in a flow direction, the waterway comprising a bubble screen disposed at an angle to the water flow direction, the bubble screen extending substantially from one water guiding element to another water guiding element, a collection area being provided in a downstream portion of the bubble screen, and the bubble intensity in the downstream portion of the bubble screen being less than the bubble intensity elsewhere within the bubble screen.

2. 2. The flume of claim 1, wherein the downstream portion of the bubble screen is convexly curved toward the collection area.

3. A waterway according to claim 1 or 2, characterised in that the collection area comprises a water collection system.

4. A waterway as described in claim 3, characterized in that at least one side of the water collection system has a mesh wall configured to sieve out particles and allow water to pass through.

5. 5. A waterway according to any one of claims 1 to 4, characterised in that the bubble screen is provided with at least one overlap.

6. 6. A waterway according to any one of claims 1 to 5, characterised in that the bubble screen comprises a pressure source arranged to supply compressed gas to the bubble screen.

7. A bubble screen device for passing air through a liquid (hereinafter referred to as "aeration") for use in a waterway according to any one of claims 1 to 6, comprising: a first part provided with a conduit arrangement comprising a plurality of openings along at least a portion of the conduit arrangement, substantially each opening of said plurality of openings being configured to allow the passage of gas; a second section extending along at least a portion of the first section, the second section being provided with a ballast module arranged to submerge the bubble screen device in a liquid; a ventilation module arranged to adjust the ventilation capacity of a part of the apertured conduit arrangement so that it is lower than the ventilation capacity of other parts of said apertured conduit arrangement; A bubble screen device comprising:

8. 8. The bubble screen device of claim 7, wherein the vent module comprises a constriction on the conduit arrangement configured to restrict fluid flow through a portion of the conduit arrangement.

9. 9. The bubble screen device of claim 8, wherein the constriction is provided on an inner periphery of a mantle surface of the conduit arrangement.

10. 9. The bubble screen device according to claim 7 or 8, characterized in that a constriction is provided on the outer periphery of the mantle surface of the conduit arrangement.

11. 11. The bubble screen device according to any one of claims 7 to 10, characterized in that the ventilation module comprises a diverging conduit section forming part of and / or fluidly connecting with the conduit arrangement.

12. 12. The bubble screen device according to claim 7, wherein the ventilation module comprises at least one friction element arranged within a portion of the conduit arrangement.

13. 13. The bubble screen device of claim 7, wherein the ventilation module comprises at least one textured surface extending at least partially along and on an inner periphery of a mantle surface of the portion of the conduit arrangement, the at least one textured surface being rougher than an adjacent portion of the inner periphery of the mantle surface of the conduit arrangement.

14. 14. The bubble screen device according to claim 7, wherein the ventilation module is provided as or comprises an increase in the gap between subsequent openings of a plurality of openings and / or a row of subsequent openings along the conduit arrangement.

15. 15. The bubble screen device of claim 7, wherein the ventilation module is provided as or comprises an increase in opening size between subsequent openings of a plurality of openings and / or a sequence of subsequent openings along the conduit arrangement.

16. 16. The bubble screen device according to any one of claims 7 to 15, characterized in that the ventilation module comprises a temperature device configured to regulate at least the temperature inside the conduit arrangement.

17. the ventilation module comprising at least one further conduit segment as part of the conduit arrangement comprising a further plurality of openings along at least a portion of its length; - substantially each opening of said further plurality of openings is configured to allow the passage of gas; A bubble screen device according to any one of claims 7 to 16, characterized in that a portion of the at least one further conduit segment extends along a portion of the conduit arrangement with the apertures such that a portion of the further plurality of apertures overlaps a portion of the plurality of apertures.

18. 20. The bubble screen device of claim 17, wherein at least a portion of the conduit arrangement with the opening and at least a portion of the at least one further conduit segment with an opening are disposed adjacent to one another.

19. 19. The bubble screen device of claim 7, wherein the conduit arrangement comprises a loop, and a portion of the conduit arrangement is folded back on itself.

20. 20. The bubble screen device of claim 7, further comprising an orienting module configured to orient at least a portion of the conduit arrangement with an opening, the orienting module configured to further orient at least a portion of a further conduit segment with a further plurality of openings.

21. 21. The bubble screen device of claim 20, wherein the orienting module comprises a fixing element.

22. 22. The bubble screen device of any one of claims 7 to 21, further comprising at least one pressure source in fluid communication with the conduit arrangement.

23. 23. The bubble screen device according to any one of claims 7 to 22, characterized in that a manifold is provided which is arranged to distribute gas supplied from at least one pressure source to the conduit arrangement.

24. 24. A method for recovering plastic waste from a waterway using a waterway or a bubble screen according to any one of claims 1 to 23, comprising the steps of: - providing a bubble screen between the water guiding element of the flow channel and another water guiding element, the bubble screen extending at an angle to the water flow direction of the flow channel; - capturing the plastic waste on the bubble screen and guiding it along the bubble screen towards a collection area in the downstream part of the bubble screen near the water guiding element; - providing a bubble intensity in a downstream portion of the bubble screen that is less than the bubble intensity elsewhere in the bubble screen to mitigate the formation of vortices near the collection area and to prevent the accumulation and / or deposition of plastics near the collection area; The method of claim 1, comprising:

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