Patent Description:
Bubble screens for distributing and/or dispersing fluids into a liquid are generally known. Often, the fluid is air and the liquid is a body of water, in particular a watercourse, such as a pond, lake, river, canal, stream, part of a sea and/or ocean like a bay, fjord or arm of the sea. Such bubble screens are applied for various purposes. For instance, bubble screens are typically applied to aerate water for aquaculture, bacterial and/or waste treatment, ice-melting, or the like.

It has previously been proposed to use such bubble screens to recover plastic waste, i.e. plastics, from watercourses. Examples of such bubble screens can be found in publications <CIT>, <CIT> and <CIT>, the first of which discloses a bubble screen according to the preamble of claim <NUM>. Although an upward thrust provided by known bubble screens may beneficially bring plastics to the water surface, it has proven difficult in practice to effectively intercept plastics before they reach e.g. seas and/or oceans, in particular in such a way that allows efficient recovery of the plastics for further treatment.

The invention aims to alleviate one or more of the aforementioned drawbacks, while maintaining the above-mentioned advantage. In particular, the invention aims to provide an improved bubble screen watercourse configuration that is more efficient and allows an improved recovery yield of plastic waste from a watercourse.

To that end, the invention provides for a watercourse with water flowing in a flow direction, wherein the watercourse comprises a bubble screen provided at an angle relative to the water flow direction, wherein the bubble screen substantially extends from a water guide element to another water guide element, wherein a downstream part of the bubble screen is provided with a collection area, and wherein a bubble intensity of the downstream part of the bubble screen is less than the bubble intensity elsewhere in the bubble screen, such that the formation of eddies in the water in the vicinity of the collection area is counteracted.

In general, plastics move in the water flow direction and/or are taken along with the water flow direction, in particular downstream e.g. to a further watercourse, sea or ocean. In certain cases, at least part of the water and thus the plastics may move in a substantially opposite flow direction, for instance due to tidal influences or relatively strong winds. In such cases a further collection area may be provided at an opposite part of the bubble screen relative to the part that is provided with the collection area. This way, a collection area may be provided on both sides of the bubble screen and may hence allow improved recovery of plastics.

By providing the bubble screen at an angle relative to the water flow direction, plastic intercepted by the bubble screen may conveniently be guided downstream and towards the collection area. When a bubble intensity of the downstream part of the bubble screen is less than the bubble intensity elsewhere in the bubble screen, plastic may be guided less forcefully towards the collector. In addition, formation of eddies in the water in the vicinity of the collection area is counteracted. An eddy is a circular current of water. By providing a lower bubble intensity at the downstream part of the bubble screen, formation of a so-called swirling motion of eddies in the water may at least partially be mitigated. Thereby, accumulation and/or build-up of plastics in the vicinity, in particular upstream, of the collection area may be counteracted. In particular, this may promote the run through of plastic towards the collection area.

Within the context of this patent specification, the term 'water guide element' is to be construed as an element that at least partially bounds water. For instance, a water guide element may thus refer to ground bounding water, such as an embankment, riverside or shore, but may also refer to artificial or so-called manmade constructs that bound water, such as a causeway, quay, wharf, levee, dyke, and in particular may additionally refer to a further bubble screen. These expressions in this context are understood to be comprised within the definition of the term 'water guide element'.

When the downstream end of the bubble screen curves, in particular convexly, towards the collector, plastic may be gradually urged towards the collection area thereby achieving a freer flow of plastic towards the collection area. This way, the recovery yield of plastics from watercourses may be further improved.

The collection area may for instance be a waterside, such as a riverbank, shore or beach. Advantageously, the collection area may comprise a collector, in particular a catchment system to further improve the recovery yield of plastics. In addition, by providing the collection area with a collector, in particular a catchment system, plastics may conveniently be recovered in a more controlled manner.

When the bubble screen is provided with at least one partial overlap, presence and/or formation of a gap in the bubble screen may be counteracted. Thereby, loss of plastics slipping through the bubble screen may be mitigated. In particular, when the at least one partial overlap forms a cascade in the bubble screen, guidance of the plastic along the bubble screen and towards the collection area and/or collector may beneficially be promoted.

By providing the bubble screen with a pressure supply that is configured to supply compressed gas to the bubble screen, a relatively simple and cost-effective construction may be provided. Advantageously, the pressure supply may be coupled to an upstream end of the bubble screen, allowing a pressure drop along the bubble screen, in particular due to frictional forces, at the downstream part to be greater than elsewhere in the bubble screen. This way, the bubble intensity of the downstream part of the bubble screen may conveniently be less than elsewhere in the bubble screen.

The invention further provides for a bubble screen device for aerating liquid, in particular for use in a watercourse including features as described above, comprising a first portion provided with a conduit arrangement presenting a plurality of apertures along at least part of the conduit arrangement, wherein substantially each aperture of the plurality of apertures is configured to allow passage of a gas, a second portion extending along at least a part of the first portion and provided with a ballast module that is arranged to submerge the bubble screen device in a liquid, in particular water, and an aeration module arranged to regulate an aeration capability of a part of the conduit arrangement presenting apertures to be less than the aeration capability elsewhere in the conduit arrangement presenting apertures.

When the bubble screen device comprises a first portion provided with a conduit arrangement presenting a plurality of apertures along at least part of the conduit arrangement, wherein substantially each aperture of the plurality of apertures is configured to allow passage of a gas, the bubble screen device may be used to aerate a watercourse. In particular, substantially each aperture of the plurality of apertures may be configured to allow passage of a gas whilst counteracting ingress of water therethrough and into the conduit arrangement. The conduit arrangement may e.g. be substantially formed of a plastic material, such as polyvinylchloride (PVC), low-density polyethylene (LDPE), high-density polyethylene (HDPE), or the like.

When the bubble screen device comprises a second portion provided with a ballast module that is arranged to submerge the bubble screen in a liquid, the bubble screen device may conveniently be placed in a watercourse. The ballast module may e.g. comprise a ballast reservoir, a substantially solid member, and/or an anchoring arrangement comprising at least one anchor. The ballast module may be formed of a material similar to and/or compatible with that of the conduit arrangement. Additionally or alternatively, the ballast module may comprise one or more weights such as metal weights included therein and/or connected thereto.

By providing an aeration module that is arranged to regulate an aeration capability of a part of the conduit arrangement presenting apertures to be less than the aeration capability elsewhere in the conduit arrangement presenting apertures, a bubble intensity induced by part of the bubble screen device during use may be less than the bubble intensity induced elsewhere by the bubble screen device. In particular, the bubble screen device may thus be provided in a watercourse with a water flow direction such that the part of the conduit arrangement presenting apertures having less aeration capability corresponds to a downstream part of the bubble screen device. This way, during use, plastics may conveniently be guided less forcefully towards a collection area, such as a waterside, collector and/or catchment system. Additionally, during use, formation of eddies in the water at least in the vicinity of a collection area is counteracted.

The aeration module may comprise a constriction provided on the conduit arrangement that is arranged to constrict fluid flow through part of the conduit arrangement. This way, a pressure in part of the conduit arrangement may be reduced which in turn diminishes the aeration capability of that part. Hence, during use, a bubble intensity of a corresponding part of a bubble screen induced by the bubble screen device may conveniently be less than elsewhere in the bubble screen. In particular, the constriction may be provided as a valve to allow control over the amount of constriction within the conduit arrangement. Additionally or alternatively, the constriction may e.g. be porous membrane/material, a flange or a de Laval nozzle (i.e. convergent -divergent nozzle).

The constriction may be provided on an inner periphery of a mantle surface of the conduit arrangement, such as a flange extending radially inwardly from the mantle surface along at least part of the circumference of the inner periphery. Additionally or alternatively, the constriction may be provided on an outer periphery of a mantle surface of the conduit arrangement, e.g. as a collar or clamp device. This may work particularly well when the conduit arrangement is substantially made of a flexible plastic material.

When the aeration module comprises a divergent conduit section forming and/or in fluid connection with said part of the conduit arrangement, a pressure in that part of the conduit arrangement may effectively be lowered with respect to the pressure elsewhere in the conduit arrangement. This way, the aeration capability of that part is less than elsewhere in the conduit arrangement presenting apertures and during use the corresponding part of the bubble screen may have less bubble intensity than elsewhere in the bubble screen.

The aeration module may comprise at least one textured surface on and/or extending at least partially along an inner periphery of a mantle surface of said part 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.

Within the context of this patent specification, the term 'textured surface' is to be construed as a surface portion that is rough compared to an adjacent surface portion of the inner periphery of the mantle surface of the conduit arrangement. Such adjacent surface portion may in particular have a surface finish that is smooth compared to the textured surface. Such adjacent surface portion may in the context of this application then in particular be considered a non-textured surface. Such a smooth surface may, as a matter of reference, be as smooth as a regular (inner) mantle surface of a typical conduit arrangement. The textured surface may thus be rough compared to a surface having the normal surface finish of the mantle surface of conventional conduit arrangement for aeration of watercourses.

Advantageously, the aeration module may comprise a temperature device that is configured to regulate at least a temperature inside the conduit arrangement. For instance, the temperature device may comprise at least one insulation element and/or at least one heating element. This way, by heating or insulating elsewhere in the conduit arrangement, the pressure there may be higher relative to said part of the conduit arrangement. Hence, during use the bubble intensity of a corresponding part of the bubble screen may be increased relative to said part of the conduit arrangement. Additionally or alternatively, in said part of the conduit arrangement e.g. at least one cooling element may be provided as a temperature device.

When the aeration module comprises at least one further conduit segment as part of the conduit arrangement presenting a further plurality of apertures along at least part of its length, wherein substantially each aperture of the further plurality of apertures is configured to allow passage of a gas, and wherein part of the at least one further conduit segment extends along part of the conduit arrangement presenting apertures, such that a part of the further plurality of apertures overlaps with a part of the plurality of apertures, a relatively simple construction may be achieved whilst counteracting a possibility of a gap forming in the bubble screen during use at a transition between the part of the conduit arrangement and the further conduit segment. This way, during use, it may be mitigated that plastics slip through the bubble screen and continue downstream e.g. towards a further watercourse, sea and/or ocean.

When at least the part of the conduit arrangement presenting apertures and at least the part of the at least one further conduit segment presenting apertures are disposed adjacent to each other, it may be counteracted that during use part of the bubble screen at and/or near the overlap is blocked.

When the conduit arrangement comprises a loop and a portion of the conduit arrangement is looped back onto itself, a meandering flow path through the conduit arrangement may be provided. This way, a pressure drop may conveniently be realized in said part of the conduit arrangement during use. Additionally or alternatively, the portion of the conduit arrangement that is looped back onto itself may provide additional aeration elsewhere in the bubble screen as desired. For instance, during use a bubble intensity of a part of the bubble screen in a relatively deep part of the watercourse may be increased.

The invention further relates to a method for recovering plastic waste from a watercourse, the method comprising:.

The invention will further be elucidated on the basis of exemplary embodiments which are represented in the drawings. The drawings are only schematic representations of embodiments of the invention, which are given by manner of non-limiting exemplary embodiments.

In the drawings, the same or corresponding parts are designated with the same reference numerals.

<FIG> shows a watercourse <NUM>. The watercourse <NUM> comprises water flowing in a flow direction F and has a width w extending substantially transverse to the water flow direction F. The watercourse <NUM> comprises a bubble screen <NUM> provide at an angle a relative to the water flow direction F. The angle a shown here is approximately <NUM>°, however any angle in the range between circa <NUM>°-<NUM>° may be chosen, such as between circa <NUM>°-<NUM>° or between circa <NUM>°-<NUM>°. Here, the bubble screen <NUM> extends from an embankment as water guide element <NUM> to another embankment as another water guide element <NUM>'. A downstream part <NUM> of the bubble screen <NUM> is provided with a collection area <NUM> that comprises a catchment system <NUM> as a collector. Additionally or alternatively, the collection area <NUM> may be provided as a waterside, such as a riverbank, shore or beach, where plastics e.g. wash ashore. A bubble intensity I of the downstream part <NUM> of the bubble screen <NUM> is less than the bubble intensity I elsewhere in the bubble screen <NUM>.

In use, plastic waste may be recovered from the watercourse by intercepting plastic waste on the bubble screen and guiding it along the bubble screen towards a collection area at a downstream part of the bubble screen near the guide element. A bubble intensity of the downstream part of the bubble screen that is less than the bubble intensity elsewhere in the bubble screen may be provided to mitigate the formation of eddies near the collection area so as to prevent accumulation and/or build-up of plastics in the collection area's vicinity.

Particles, in particular plastics P, move in the water flow direction F, in particular downstream towards e.g. a further watercourse, sea or ocean (not shown). The plastics P are intercepted by the bubble screen <NUM> and are gradually moved downstream towards the catchment system <NUM> at the collection area <NUM>. In certain cases, at least part of the water and thus the plastics P may move in a substantially opposite flow direction, for instance due to tidal influences or relatively strong winds (not shown). In such cases a further collection area may be provided, optionally with a collector, at an opposite part of the bubble screen <NUM> relative to the downstream part <NUM> of the bubble screen <NUM> that is provided with the catchment system <NUM> at the collection area <NUM>.

The downstream part <NUM> of the bubble screen <NUM> curves, in particular convexly, towards the collection area <NUM>. However, any change in gradient between the downstream part <NUM> of the bubble screen relative to the rest of the bubble screen <NUM> may be conceived, such as a stepped or abrupt change.

At least one side <NUM> of the catchment system <NUM> that is provided as the collector, presents a meshed wall. The meshed wall is configured to sieve out particles, in particular plastics P, whilst allowing water to pass through. The meshed wall may e.g. have a sieve or so-called mesh size in the range between circa <NUM>-<NUM>, such as between circa <NUM>-<NUM> or between circa <NUM>-<NUM>. Additionally or alternatively, the meshed wall is configured to sieve out particles with a particle or so-called screen size in the range between <NUM>-<NUM>, such as having a screen size greater than circa0. <NUM> or greater than circa <NUM>. The screen size is to be construed as sieving out at least circa <NUM>% of particles with a certain particle size.

In the exemplary embodiment, a gas, in particular compressed gas, is supplied to the bubble screen <NUM> from a pressure supply <NUM> provided at the downstream part <NUM> of the bubble screen <NUM>. Advantageously, the pressure supply <NUM> may be provided at an upstream part of the bubble screen <NUM>, that is to say on a side opposite to the one shown here.

<FIG> shows a watercourse having a width W that is wider in a direction substantially transverse to the water flow direction F than the width w of the watercourse of <FIG>. In this exemplary embodiment, the bubble screen <NUM> is provided with a partial overlap <NUM>. In particular, the partial overlap <NUM> forms a cascade <NUM> at a transition T of the bubble screen <NUM>. This way, a gap forming in the bubble screen at the transition T may be counteracted and hence the risk of particles, in particular plastics P, slipping through the bubble screen <NUM> is mitigated. In addition, as the cascade <NUM> transitions downstream in the flow direction F, guidance of the plastics P downstream along the bubble screen <NUM> may be promoted.

<FIG> shows a watercourse <NUM> provided with a bridge B having a support pillar S within the watercourse <NUM>. In this exemplary embodiment, both the water guide element <NUM>' and another water guide element <NUM>" are each formed by a distinct bubble screen <NUM>. Here, the bubble screen <NUM> shown on the right hand side of <FIG> as seen in a water flow direction F extends substantially from an embankment <NUM> to the other bubble screen <NUM> shown on the left hand side of <FIG>. The other bubble screen <NUM> in turn extends substantially from an embankment <NUM> to the bubble screen <NUM>. A collection area <NUM> is provided on the right hand side of the support pillar S, but could also have been provided on the left hand side or an end of the support pillar S. Particles, in particular plastics P, are intercepted by the bubble screens and are guided downstream towards the collection area <NUM> which is provided with a catchment system <NUM>.

<FIG> shows a bubble screen device <NUM> for aerating a liquid. The bubble screen device <NUM> comprises a first portion <NUM> that is provided with a conduit arrangement <NUM>. In this exemplary embodiment, the conduit arrangement <NUM> is substantially formed of a plastic material, such as PVC, LDPE, HDPE and the like. The conduit arrangement <NUM> presents a plurality of apertures <NUM> along at least part of the conduit arrangement <NUM>. Substantially each aperture of the plurality of apertures <NUM> is configured to allow passage of a gas, in particular whilst counteracting ingress of water.

The bubble device <NUM> further comprises a second portion <NUM> extending along the first portion <NUM>, in particular substantially the entire first portion <NUM>. The second potion <NUM> is provided with a substantially solid ballast <NUM> as a ballast module. The ballast <NUM> is arranged to submerge the bubble screen device <NUM> in a liquid, in particular water. Additionally or alternatively, the ballast module may include one or more anchor elements e.g. disposed with fixed or variable interspace along at least a part of the first portion <NUM>.

The bubble screen device <NUM> comprises an aeration module <NUM> arranged to regulate an aeration capability of a part <NUM> of the conduit arrangement <NUM> presenting apertures to be less than the aeration capability elsewhere in the conduit arrangement <NUM> presenting apertures. In this exemplary embodiment, the aeration module <NUM> comprises a constriction <NUM>. The constriction <NUM> is provided on the conduit arrangement <NUM> and is arranged to constrict fluid flow through part of the conduit arrangement <NUM>. In particular, the constriction <NUM> is provided as a clamp device on an outer periphery <NUM> of a mantle surface <NUM> of the conduit arrangement <NUM>. The aeration module <NUM> in this exemplary embodiment further comprises an increase in aperture size between two sequences of subsequent apertures of the plurality of apertures <NUM>. A first sequence of subsequent apertures <NUM> comprises apertures of a first size and a second sequence of subsequent apertures <NUM> comprises apertures of a second size that is larger than the first size. Of course the aeration module <NUM>, may be provided as either the constriction <NUM> or the increase in aperture size between the two sequences.

The conduit arrangement <NUM> and the ballast <NUM> are secured together, in particular they are secured together by welding. Additionally or alternatively, other means of securing such as adhesive or snap connection may be utilized.

Additionally or alternatively, a constriction <NUM> as an aeration module <NUM> may be provided on an inner periphery <NUM> of a mantle surface <NUM> of a conduit arrangement <NUM> (not shown). For instance, the constriction <NUM> may be an adjustable valve or a flange extending radially inwardly from the inner periphery <NUM> of the mantle surface <NUM> or the like.

<FIG> shows a bubble screen device <NUM> with a first portion <NUM> provided with a conduit arrangement <NUM> presenting a plurality of apertures <NUM> there along. Substantially each aperture is configured to allow passage of gas, in particular whilst counteracting ingress of water. The bubble screen device <NUM> is further provided with a second portion <NUM> comprising a ballast module <NUM> for submerging the bubble screen device in a liquid. The bubble screen device <NUM> also comprises an aeration module <NUM>. The aeration module <NUM> comprises a divergent conduit section <NUM> forming part <NUM> of the conduit arrangement <NUM> having less aeration capability than the aeration capability elsewhere in the conduit arrangement (not shown). Alternatively, the divergent conduit section <NUM> may be in fluid connection with said part <NUM> of the conduit arrangement <NUM>.

In addition, the aeration module <NUM> of <FIG> comprises an increase in interspace between subsequent apertures of the plurality of apertures <NUM> such that the aeration capability of said part <NUM> of the conduit arrangement <NUM> is less than the aeration capability elsewhere in the conduit arrangement presenting apertures (not shown).

<FIG> shows a bubble screen device <NUM> according to another aspect of the invention. In this exemplary embodiment, the aeration module <NUM> comprises a further conduit segment <NUM> as part of the conduit arrangement <NUM>. Also, more than one further conduit segment may be provided, e.g. two, three, four, or more (not shown). The further conduit segment <NUM> presents a further plurality of apertures <NUM> along at least part of its length. Similarly as the plurality of apertures <NUM> described above, substantially each aperture of the further plurality of apertures <NUM> is configured to allow passage of gas, in particular whilst counteracting ingress of water. Part <NUM> of the at least one further conduit segment <NUM> extends along part <NUM> of the conduit arrangement <NUM> presenting apertures, such that a part of the further plurality of apertures <NUM> overlaps with a part of the plurality of apertures <NUM>. In this exemplary embodiment, an end of the conduit arrangement <NUM> is provided with a plug and gas is provided from an opposite end. Also, a further end of the further conduit arrangement <NUM> is provided with a plug and gas is provided from the top right hand side of the schematic drawing. However, a construction wherein both the conduit arrangement <NUM> and the further conduit arrangement <NUM> extend are both provided with gas from the same end, e.g. from the bottom left hand side of the schematic drawing, and wherein the further conduit arrangement <NUM> extends beyond the part <NUM> of the conduit arrangement <NUM> may also be contemplated.

Part <NUM> of the conduit arrangement <NUM> presenting apertures and part <NUM> of the further conduit segment <NUM> are disposed adjacent to each other.

The bubble screen device <NUM> comprises an orientation module <NUM> arranged to orientate at least part <NUM> of the conduit arrangement <NUM> presenting apertures and to further orientate at least part <NUM> of the further conduit segment <NUM> presenting the further plurality of apertures <NUM>. In this exemplary embodiment, the apertures are orientated by the orientation module <NUM> towards a side of the bubble screen device <NUM>, in particular such that in use, the apertures are facing upstream in the water flow direction. Additionally or alternatively, more than one orientation module may be provided e.g. for each at least part of each further conduit segment. The orientation module may comprise an anchoring element (not shown).

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

Different aspects of the described aeration module may be implemented in isolation or may be combined. A further conduit segment as part of the conduit arrangement may e.g. be in fluid connection with a further pressure supply and/or be provided with apertures having an increased aperture size with respect to aperture size of the plurality of apertures. For instance, substantially each or at least one aperture of the (further) plurality of apertures may comprise a nozzle, in particular as aeration module.

Claim 1:
Watercourse (<NUM>) with water flowing in a flow direction, wherein the watercourse (<NUM>) comprises a bubble screen (<NUM>) provided at an angle relative to the water flow direction, wherein the bubble screen (<NUM>) substantially extends from a water guide element (<NUM>) to another water guide element (<NUM>'), wherein a downstream part (<NUM>) of the bubble screen (<NUM>) is provided with a collection area (<NUM>), characterized in that a bubble intensity (I) of the downstream part (<NUM>) of the bubble screen (<NUM>) is less than the bubble intensity (I) elsewhere in the bubble screen (<NUM>) such that the formation of eddies in the water in the vicinity of the collection area (<NUM>) is counteracted.