Biofouling from Vessels

Technical Field [0001 ] The present invention relates to an apparatus and method for using the apparatus for the in-water capture, containment, and removal of biofouling effluent removed from the hulls and running gear of water craft.

Background Art

[0002] Biofouling of water craft and other movable and non-movable submerged structures from the growth and accumulation of aquatic organisms has been an ever-present issue.

[0003] While most marine vessels today have anti-fouling paint applied to their hulls, stringent environmental restrictions in many jurisdictions including Australia and New Zealand limit the use of biocides in the paint which severely reduces its effectiveness at preventing biofouling.

[0004] Biofouling on vessels increases drag which directly affects the performance of the vessels resulting in increased costs and greater environmental harm through increased fuel consumption and the resulting emissions. Another concern is that species attached to a biofouled hull can reach reproductive maturity and spawn in ports of call leading to the spread of invasive aquatic species. As a result, economic pressures and adherence to local environmental laws mean that owners and operators of commercial vessels and shipping fleets will generally follow an appropriate cleaning strategy for regular removal of biofouling from their vessels. [0005] Aside from dry docking, boat owners have no other safe options for biofouling removal, and often resort to cleaning the vessel's hull in the water. Either unaware or ignoring current state guideline they consequently contaminate the surrounding water with aquatic pests and residual anti-foul coating.

[0006] Biofouling that is deemed safe (i.e. native) to the surrounding aquatic environment along with vessels that have no anti foul coating, can be shed from the vessel or marine structure and accumulate at the bottom of the seabed. However, the accumulation of this organic material will decay/decompose with the growth of bacteria. This bacterial growth reduces the levels of oxygen in the water, wherein reduced oxygen availability in the water directly contributes to the death of fish and other aquatic species in the vicinity.

[0007] Most private owners of smaller pleasure craft including sailboats and motorboats do not cover the distances of commercial ships and rarely enter foreign ports lessening the economic and environmental pressures to remove biofouling from the hulls of their vessels. Rather, the regularity and type of hull cleaning will depend on whether these private vessels generally remain in the water, are kept on boat lifters or some other platform, or removed from the water after each use and kept on land. Other influencing factors will include the availability and location of hull cleaning services, cost, and the time and effort that the boat owner will expend in having biofouling removed from their boat. [0008] The most effective way of removing biofouling from the hull of a vessel is when the vessel has been dry-docked. However, this is usually a costly exercise as a crane driver is required to lift smaller vessels out of the water in a sling, and requires the boat owner or operator on site to drive the boat to the sling. It is also not always feasible depending on whether there are facilities available near where the vessel is docked. When in dry-dock, the hulls and running gear of these vessels are manually cleaned with high pressure water cleaners. However, the high- pressure cleaners can lift the clear coat of the anti-foul coating on the hull of a vessel causing the anti-foul seal to be broken. The waste water containing anti-foul chemicals and biofouling usually ends up in the drains where it may enter the local river or ocean. In addition, slings place stress on the hull when lifted from the water, eventually causing stress fractures in the hull.

[0009] ln-water cleaning is a more-cost effective means for removing biofouling from vessel hulls but during the past couple of decades, local laws in a number of jurisdictions have significantly limited in-water cleaning operations. In-water cleaning traditionally involves divers using tools and brushes to manually remove biofouling from the hulls of vessels. More recently, divers are also utilising automated brushes or brushing machines. In addition, some remotely operated systems are now using, for example, seawater under high pressure as the cleaning medium instead of brushes or abrasives, and the biofouling effluent is vacuumed from the ocean to be collected and disposed of in an environmentally friendly manner. However, while these remotely operated systems are fast and cost- effective for large ships, the cost is usually prohibitive for owners and operators of small vessels.

[0010] In Australia and New Zealand, the in-water cleaning of boat hulls was effectively banned after the introduction of the Australian and New Zealand Environment and Conservation Council (ANZECC) Code of Practice for 'Antifouling and In-water Hull Cleaning and Maintenance' in 1997 ('the ANZECC Code'). The intent of the introduction of the ANZECC Code was to protect the marine environment. However, the regulations were so limiting that there was a reduction in the removal of biofouling from vessels to the extent that there were concerns that greater environmental harm was being caused from increased fuel consumption and associated emissions, and the increased spread of invasive aquatic species. The ANZECC Code is currently under review and new draft guidelines were issued in 201 1 which allow in-water hull cleaning under tightly regulated conditions. It requires that in-water cleaning should only be undertaken when removal of biofouling does not harm the coating and presents an acceptable biosecurity or contaminant risk. [001 1 ] A majority of Australian marinas will not allow in-water cleaning of boat hulls within the marina in accordance with the ANZECC code, other local laws, but just as importantly, to prevent contamination of their waterways with biofouling effluent. This is because most of these marinas are situated along open coast lines and are protected by large rock walls which block ocean currents from regularly flushing out water from the marinas. As a result, owners of boats kept in marina pens will dry-dock their vessels at considerable cost and effort for hull cleaning, or more often the case, ignore the biofouling on their boat hull for as long as possible increasing fuel usage and cost and subsequent emissions.

[0012] The present invention attempts to overcome, at least in part, the above described disadvantages with previous boat-hull cleaning regimes.

[0013] The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge as at the priority date of the application.

Summary of Invention

[0014] First Aspect of the Invention [0015] In accordance with a first aspect of the invention, there is provided a method for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning, the method comprising the steps: surrounding an in-water hull of a vessel with an apparatus, the apparatus comprising an underwater enclosure having a border at the water's surface, wherein water can pass through at least a portion of the enclosure but biofouling is substantially prevented from passing through the enclosure; removal of biofouling from the hull; containment of the biofouling removed from the hull within the enclosure; and removal of the enclosure from the water for disposal of the biofouling.

[0016] At least a portion of the border is preferably buoyant which maintains the border at or adjacent the surface of the water. The border may be constructed from a variety of materials. Preferably the border is constructed from a marine grade nylon material, plastic or coated stainless steel cable. Throughout the border are steel eyelets to which buoyant devices can be attached and removed.

[0017] Reference herein to removal of biofouling from the 'hull' of a vessel also includes removal of biofouling from the running gear and/or other aspects of the vessel. For the purpose of describing the invention, reference herein to 'running gea refers to the propellers, shafts, anodes and other parts of the vessel aside from the hull which are exposed to the water the vessel resides in.

[0018] The border is preferably maintained adjacent to the surface of the water by one or more buoyant devices. Preferably the buoyant devices are attached to or comprise part or the entire border. More preferably, the buoyant devices are removably clipped onto the border. The buoyant devices may be made from a variety of materials which includes, in some non-limiting examples, plastic or foam. The buoyant device may comprise, for example, an inflatable bladder which can be filled with air and also deflated after use, or a sock that is comprised of a buoyant material, for example, foam.

[0019] In the method of the invention, the step of surrounding the in-water hull with the apparatus preferably comprises moving a portion of the apparatus under the hull from one side of the vessel to the other until the border encircles the in- water hull adjacent to the surface of the water. In a preferred embodiment, one or more divers pull and guide the apparatus under the vessel spreading the enclosure until it surrounds the hull and the border encircles the hull adjacent to the surface of the water. In another embodiment, cables attached to the apparatus are used to pull the apparatus under the vessel spreading the enclosure until it surrounds the hull and the border encircles the hull adjacent to the surface of the water. In a further embodiment, the step of surrounding the in-water hull with the apparatus comprises moving the vessel into a position above the enclosure.

[0020] The apparatus used in the method of the invention preferably comprises at least a portion of the enclosure that water can pass through but substantially prevents biofouling from passing through. Preferably, the portion comprises most or all of the enclosure. This portion of the enclosure preferably comprises netting, mesh or a filter which may be made from a variety of materials. Preferably, the breaking force of the netting or mesh in the WARP direction is at least 1000 N/50 mm. The breaking force of the netting or mesh in the WEFT direction is preferably at least 1800 N/50 mm. The tear resistance of the netting or mesh in the WARP direction is preferably at least 300 N. The tear resistance of the netting or mesh in the WEFT direction is preferably at least 300 N. The micron rating for the material to filter biofouling may be a variety of sizes, and is preferably between 50 micron and 600 micron. Preferably, the enclosure comprises marine grade, monofilament nylon mesh which allows the transfer of water but contains the biofouling shed from vessels or marine structures.

[0021 ] In a preferred embodiment of the method of the invention, the enclosure further comprises an additional inner lining of, for example, nylon, amongst other materials. The inner lining lines the inner surface of the enclosure (between the net and the hull) to provide an additional filtration layer for the purpose of filtering microscopic bio-fouling or contaminants (pending scientific testing) and anti-foul coating. The inner lining preferably comprises pore sizes of up to 50 microns.

[0022] The apparatus surrounding the in-water hull is preferably maintained at a distance from the in-water hull creating a water-filled space or gap. In one embodiment, extension bars are used to maintain the distance between the apparatus and the in-water hull. An extension bar preferably comprises a first and second end, and wherein the first end is attached to the apparatus, and a suction cup at the second end of the extension bar attaches the extension bar to the in- water hull which is maintained in place by vacuum forces. The first end of the extension bar preferably attaches to the apparatus by a clip. The extension bar may be extendible. The extension bar may be made of a variety of materials. Preferably the material the extension bar is made from is rust or corrosion proof. In one non- limiting example, the extension bar comprises plastic. In another embodiment, sand bags are placed in the enclosure to form and maintain the shape of the enclosure to maintain the distance between the apparatus and the in-water hull.

[0023] Once the apparatus is surrounding the hull in the method of the invention, the apparatus is preferably removably tethered to anchors or the sea floor at one or more positions on the apparatus. Preferably anchor lines are attached to the apparatus which are tethered to anchors. More preferably, the anchor lines can be attached to the apparatus and anchors with clips that can be attached and removed by divers. In some non-limiting examples, the anchor lines are constructed from stainless steel cables, plastic, nylon or rope. The anchor lines are preferably adjustable and may comprise adjustable straps. [0024] Divers enter the space between the enclosure and vessel to access the hull. The step of removal of biofouling from the hull in the method of the invention is preferably carried out by one or more divers operating within the gap between the enclosure and hull. In-water removal of biofouling from the hull (and running gear) may be carried out using known or available in-water hull-cleaning techniques. In a preferred embodiment of the invention, biofouling is removed using mechanical means (with no chemicals) from the hull of the vessel using ribbed mitts or gloves, and/or a soft brush. In another embodiment, automated hull-cleaning apparatus is used to remove biofouling from the hull of the vessel. Biofouling removed from the hull settles in the enclosure and is substantially prevented from escaping the apparatus. The time that the removed biofouling takes to settle in the enclosure will vary depending on a variety of factors including weight and density of the biofouling, water currents, etc., and is preferably monitored by divers by observing water visibility, and/or water sampling monitoring systems may be employed. The position of the border adjacent to the surface of the water, and preferably above the level of the water substantially prevents biofouling contaminated water from escaping over the top of the border (due to current, wakes, winds, etc.) so it remains captured in the apparatus and the enclosure. [0025] In one embodiment, the method of the invention comprises the removal of biofouling from the enclosure using a vacuum system, which removes and filters biofouling out of the water. Biofouling collected by the vacuum is preferably removed onto land and the water returned to the water body from which it was removed. [0026] In the method of the invention, the step of removing of the apparatus and the collected biofouling from the water comprises: moving a portion of the apparatus under the hull from one side of the vessel to the other side until all of the apparatus is on one side of the vessel while substantially containing the biofouling within the apparatus; and raising the apparatus out of the water; wherein water can pass through the enclosure but the biofouling is substantially collected in the enclosure. Preferably, one or more divers move the portion of the apparatus under the hull from one side of the vessel to the other side. This will comprise submerging a border on one side of the vessel and any buoyant devices on at least that side will require removal or deflation.

[0027] The border must preferably remain above the water line for as long as possible. Therefore, the border is brought to a side of the vessel above the water level. The one or more buoyant devices are removed along the same side of the vessel, the border is submerged along the side of the vessel, brought under the bottom of the hull of the vessel and up on the other side of the vessel. Preferably this border is submerged along one side of vessel from bow to stern which serves to substantially prevent biofouling escaping from the enclosure.

[0028] If the apparatus has been removably tethered to one or more anchor lines attached to anchors or the sea floor, the portion of the apparatus being moved under the hull from one side of the vessel to the other side is first untethered from those anchor lines. Further, when all of the apparatus is located on one side of the vessel, the apparatus is untethered from any remaining anchor lines before raising the apparatus out of the water. Preferably, the border is maintained above the enclosure as the apparatus is raised thereby substantially preventing biofouling from escaping the apparatus.

[0029] In a preferred embodiment, the apparatus is raised out of the water using a crane or winch. In a preferred embodiment, a trolley winch is used which is positioned on the dock, wharf, pier, jetty or some other grounded platform next to the vessel. Preferably, the apparatus is held above the water for sufficient time that a majority of water collected in the enclosure of the apparatus can drain out and back into the body of water from which it has been removed, for example, the ocean or river.

[0030] Once substantially drained from water, the apparatus is preferably repositioned over the grounded platform where biofouling is removed from the apparatus and the apparatus cleaned for storage. In one non-limiting example, biofouling is manually collected from the enclosure after releasing the border from the winch making the enclosure accessible. The apparatus is preferably cleaned using a heavy duty vacuum system or using water, for example, high pressure hoses. The apparatus may be stored, for example, in a trailer, or van or another customised movable storage facility.

[0031 ] Disposal of biofouling is preferably as general waste as approved by local governing body or organisation. Alternatively, the biofouling may be recycled or used in the production of compost of other garden or agricultural products according to government approvals and relationships with local business. [0032] The invention further provides an apparatus as described herein for use in the method according to the first aspect of the invention for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning. [0033] The invention further provides the use of an apparatus as described herein for carrying out the method according to the first aspect of the invention, for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning. [0034] Second Aspect of the Invention

[0035] In a second aspect, the invention provides a method for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning, the method comprising the steps: manoeuvring an in-water vessel to be cleaned into an enclosure through an access portion in the enclosure, the enclosure comprising a border at the water's surface and an underwater barrier that surrounds the in-water hull of the vessel; removal of biofouling from the hull; manoeuvring the vessel through the access portion to exit the enclosure; wherein a plurality of streams of gas bubbles are released within the water of the enclosure adjacent to the access portion forming a bubble curtain through which the vessel hull must pass when at least exiting the enclosure, the bubble curtain substantially preventing biofouling contaminating the water within the enclosure from exiting the enclosure through the access portion. [0036] Biofouling may be removed from the hull using a variety of known methods including any of those described herein or any other methods.

[0037] The plurality of streams of gas bubbles are preferably released within the water of the enclosure adjacent to the access portion forming a bubble curtain through which the vessel hull must pass when at least entering and exiting the enclosure.

[0038] The streams of gas bubbles preferably emanate from a plurality of holes along a portion of tubing located within the enclosure below the access portion, the tubing fed with compressed air from an air compressor, or another gas. The pressure of the gas fed into the tubing provides steady streams of bubbles through the holes in the tubing to minimise gaps between bubbles through which biofouling- contaminated water may escape.

[0039] The bubble tubing is preferably in one to ten rows, more preferably in two or three rows (thereby creating two or three lines of bubbles to create the bubble curtain). The bubble tubing is preferably mounted to the enclosure, the barrier of the enclosure, and/or a subsea frame, amongst other means that keeps the bubble curtain area fixed and in position to carry out its function.

[0040] The holes in the tubing are sized and distanced apart to minimise gaps between streams of bubbles through which biofouling-contaminated water may escape. The distance between holes in the tubing to create the bubble curtain are preferably approximately 2 mm to 50 mm, more preferably between 10 mm and 30 mm. Though the distance between holes will also be dependent on the size of the holes and the size of the bubbles released through the holes. In this respect, larger bubbles released through larger holes can be spaced further apart from adjacent holes and vice versa.

[0041 ] Rows of bubble tubing may also be layered above other layers of bubble tubing to increase the density of a bubble curtain. In addition, sets of one or more rows may create a bubble curtain and the vessel hull may have to pass through two, three or even four sets of bubble curtains when entering and/or exiting the enclosure to further minimise the escape of water contaminated with biofouling from within the enclosure. For example, if some water contaminated with biofouling passes through a first set of bubble tubing, for example, assisted by vortices created adjacent the vessel hull as it passes through the bubble curtain, it is further prevented from passing through a second set of bubble tubing. Thus, the more sets of bubble tubing, the less possibility for contamination of water outside the enclosure with biofouling from inside the enclosure.

[0042] The 'access portion' includes reference to a re-closable opening, closable gate or similar. The border at the access portion preferably comprises at least one inflated border segment over which the vessel is manoeuvred when entering into or exiting the enclosure.

[0043] The access portion preferably comprises a re-sealable fastener that can be unfastened to provide an opening through which the vessel can pass through to enter into or exit the enclosure, and refastened after the vessel has passed through the access portion.

[0044] The access portion preferably comprises an inflated border segment either side of the re-sealable fastener, and when the fastener has been unfastened and a vessel is passing through the access portion, the inflated border segments are forced down below the surface of the water by either side of the hull.

[0045] The sides of the hull preferably force the inflated border segments down below the surface of the water as the vessel passes through the access portion substantially preventing water contaminated with biofouling from exiting the enclosure through the access portion.

[0046] The re-sealable fastener may be selected from a variety of different fasteners. Preferably, the re-sealable fastener is a marine grade zip. The zip is preferably only partially unzipped to provide an opening just large enough to accommodate the draft and beam of the hull of the vessel. That is, the zip will be unzipped according to the size of the hull which must pass through the access portion in order to (i) enable a large enough opening for the hull to pass through, and (ii) minimise the gap between opened zip and hull.

[0047] At least a portion of the underwater barrier is preferably permeable to water but not substantially to biofouling. In this regard, at least a portion of the underwater barrier comprises netting, mesh or a filter or another type of material through which water can pass but biofouling particulate cannot. More preferably, the underwater barrier comprises an inner net layer and an outer net layer. The inner net layer preferably comprises pore sizes having a diameter of between 25 μηι - 150 μηι, and more preferably, pore sizes having a diameter of between 50 μηι - 100 μηι. The outer net layer comprises pore sizes having a diameter of between 500 μηι - 700 μιτι and more preferably pore sizes having a diameter of approximately 600 μηι. The outer net layer preferably comprises monofilament yarn and provides structural integrity for the net to minimise the potential for the net to tear.

[0048] The underwater barrier is preferably releasably tethered to one or more sea anchors, weights, or the sea floor. Further, the inner net layer is preferably releasably attached to the outer net layer by one or more attachment means. [0049] The border preferably comprises a fixed substantially rectangular structure having two long sides and two ends, with a first end comprising the access portion and a second end that is inaccessible to vessels, and the inner net layer and outer net layer can be retracted to the second end. More preferably, both the inner net layer and outer net layer comprise a perimeter edge along the boundary of the opening of each net layers which attach to the border, and wherein the perimeter edge of the net layers are attached along each long side to a pulley system, the pulley system used to retract the net layers to the second end, or extend and deploy retracted net layers from the second end to form the enclosure. [0050] The inner net layer and outer net layer are preferably retracted to the second end for storage during non-use of the enclosure, or for removal of the inner net layer or both net layers from the water for collection and disposal of biofouling and/or net repair or replacement.

[0051 ] Removal of the inner net layer from the water preferably comprises mechanically lifting the inner net layer at points along the perimeter edge to raise the inner net layer above the water (after detaching any attachment means between the inner net layer and outer net layer), allowing the water in the inner net layer to drain out of the inner net layer, and removal of the inner net layer, for example, on to land, for disposal of biofouling collected in the inner net layer and/or repair of the inner net layer.

[0052] Biofouling may also be removed from the enclosure by the process comprising the step of drawing up water contaminated with biofouling from within the enclosure and passing the water through at least one filter to remove the biofouling from the water. Filtered water may be returned to the enclosure or to the water outside the enclosure.

[0053] Divers preferably operate in the water of the enclosure between the hull and the underwater barrier to remove biofouling from the hull of the vessel using manual means. Manual means includes those described herein, and preferably comprises wiping and scrubbing biofouling from the hull using cleaning mitts and brushes. [0054] The invention further comprises an apparatus for carrying out the method according to the second aspect of the invention. [0055] In addition, the invention provides the use of an apparatus for carrying out the method according to the second aspect for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning.

[0056] Third Aspect of the Invention [0057] The invention according to a third aspect comprises a method for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning, the method comprising the steps: manoeuvring a mobile apparatus to surround the underwater hull of an in- water vessel to be cleaned, the mobile apparatus comprising an underwater barrier having a border at the water's surface; removal of biofouling from the hull into the water between the hull and the underwater barrier; manoeuvring the mobile apparatus away from the vessel; wherein biofouling removed from the hull of the vessel is substantially contained within the underwater barrier.

[0058] At least a portion of the underwater barrier is preferably permeable to water but not substantially to biofouling. At least a portion of the underwater barrier preferably comprises netting, mesh or a filter or another substrate that is permeable to water but not biofouling particulates. More preferably the underwater barrier comprises a net. The net preferably comprises an inner net layer and an outer net layer. Preferably, the inner net layer comprises pore sizes having a diameter of between 25 μηι - 150 μηι, and more preferably, pore sizes having a diameter of between 50 μιη - 100 μιη. The outer net layer preferably comprises pore sizes having a diameter of between 500 μηι - 700 μηι, and more preferably pore sizes having a diameter of approximately 600 μηι. The outer net layer preferably comprises monofilament yarn.

[0059] To assist to maintain the underwater barrier at its maximum depth underwater and to maintain its shape when fully extended to provide space between the underwater barrier and the hull for the hull to be cleaned in, the underwater barrier is releasably tethered to one or more weights. Further, the inner net layer is preferably releasably attached to the outer net layer by one or more attachment means.

[0060] The mobile apparatus preferably comprises a floating U-shaped barge and the net is suspended below the barge wherein the barge forms a portion of the border at the water's surface. The net preferably comprises a boundary along the open perimeter of the net, and the net is attached at a plurality of points along the boundary to the U-shaped barge.

[0061 ] The net is preferably attached to a pulley system along each long side of the U-shaped barge, and the pulley system is used to retract the net from the open end to the closed end of the U-shaped barge, or extend and deploy retracted net layers from the closed end to the open end of the U-shaped barge. The net is preferably retracted to the closed end when the U-shaped barge is manoeuvred to surround the underwater hull of an in-water vessel within the sides of the U-shaped barge or when it is travelling to other destinations in order to minimise damage to the net.

[0062] Once the in-water vessel to be cleaned is within the sides of the U-shaped barge, the net is extended and preferably passes under the hull and past the vessel until the net surrounds the underwater hull of the vessel. The net preferably comprises an access portion and the hull of the vessel passes through the access portion when the net is extended under the hull of the vessel.

[0063] The access portion preferably comprises a re-sealable fastener that can be unfastened to provide an opening through which the underwater hull of the vessel passes through, and refastened after the net has been extended past the vessel. [0064] The boundary at the access portion preferably comprises an inflated border segment either side of the re-sealable fastener, and when the fastener has been unfastened and the net is extended under the hull of the vessel, the inflated border segments are forced down below the surface of the water by either side of the hull. The sides of the hull preferably force the inflated border segments down below the surface of the water as the net is extended under the hull of the vessel which substantially prevents water contaminated with biofouling from exiting the underwater barrier through the access portion as it minimises any gap between hull and inflated border segments. The inflated border segments may comprise one or more air filled bladders.

[0065] The re-sealable fastener may be selected from a variety of different fasteners as described herein. Preferably, the re-sealable fastener is a marine grade zip. The zip is preferably only partially unzipped to provide an opening just large enough to accommodate the draft and beam of the hull of the vessel. That is, the zip will be unzipped according to the size of the hull which must pass through the access portion in order to (i) enable the hull to pass through, and (ii) minimise the gap between opened zip and hull. After the hull of the vessel has been cleaned, the zip is preferably partially unzipped and the net is retracted under the hull and past the vessel to the closed end with the net containing biofouled contaminated water.

[0066] After the net has been retracted to the closed end of the U-shaped barge, the mobile apparatus preferably manoeuvres away from the vessel. [0067] As an additional means of containing the biofouling within the net, a plurality of streams of gas bubbles may be released within the water of the underwater barrier adjacent to the access portion forming a bubble curtain through which the vessel hull passes when the net is retracted past or extended past the vessel hull, the bubble curtain substantially preventing biofouling from exiting the underwater barrier through the access portion. The streams of gas bubbles preferably emanate from a plurality of holes along a portion of tubing located within the underwater barrier, the tubing fed with compressed air from an air compressor located on the barge.

[0068] A removable walkway can be releasably attached to the sides at the open end of the U-shaped barge for ease of access and stability of the barge when moving distances, and wherein the walkway is removed when manoeuvring the U- shaped barge to surround a vessel or move away from a vessel.

[0069] As described herein, divers preferably operate in the water between the hull and the underwater barrier removing biofouling from the hull of the vessel using manual means. The manual means preferably comprises wiping and scrubbing biofouling from the hull using cleaning mitts and brushes. [0070] Biofouling may be removed from the net by detaching the net or the inner net layer from the mobile apparatus, mechanically lifting the net or the inner net layer above the water, allowing the water in the net or inner net layer to only drain out through the netting, and removal of the net or inner net layer for disposal of biofouling collected in the inner net layer.

[0071 ] Biofouling may also be removed from within the underwater barrier by the process comprising the step of drawing up water contaminated with biofouling from within the underwater barrier, and passing the water through at least one filter to remove the biofouling from the water. Such a filter may be part of a water treatment plant located on the barge. Filtered water may be returned to within the underwater barrier or the water outside the underwater barrier.

[0072] The invention further provides a mobile apparatus for carrying out the method according to the third aspect of the invention.

[0073] In addition, the invention provides the use of a mobile apparatus for carrying out the method according to the third aspect of the invention, for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning.

[0074] Fourth Aspect of the Invention

[0075] In a fourth aspect, the invention provides a method for the containment and collection of biofouling removed from the hull of a vessel during in-water cleaning, the method comprising the steps: manoeuvring an in-water vessel to be cleaned into an enclosure through an access portion in the enclosure, the enclosure comprising a border at the water's surface and an underwater barrier that surrounds the in-water hull of the vessel; removal of biofouling from the hull; manoeuvring the vessel through the access portion to exit the enclosure; wherein a plurality of streams of gas bubbles are released within the water of the enclosure adjacent to the access portion forming a bubble curtain through which the vessel hull must pass when at least exiting the enclosure, the bubble curtain substantially preventing biofouling contaminating the water within the enclosure from exiting the enclosure through the access portion.

[0076] Biofouling may be removed from the hull using a variety of known methods including any of those described herein or any other methods. [0077] The plurality of streams of gas bubbles are preferably released within the water of the enclosure adjacent to the access portion forming a bubble curtain through which the vessel hull must pass when at least entering and exiting the enclosure.

[0078] The streams of gas bubbles preferably emanate from a plurality of holes along a portion of tubing located within the enclosure below the access portion, the tubing fed with compressed air from an air compressor.

[0079] The invention according to the fourth aspect works in a similar fashion to the second aspect except, among other differences, the fourth aspect includes a net that is impervious to water, or more preferably, the enclosure comprises a fixed rigid basin structure impervious to water transfer through the structure which is submerged below the surface of the water. Preferably, the rigid basin enclosure is constructed from fibreglass similar to a that used in swimming pool construction. More preferably, the rigid basin enclosure can hold between approximately 300 to 500 thousand litres of water. [0080] The rigid basin enclosure is preferably cleaned with an automatic water suction cleaner similar to the types of products developed for, and used to clean swimming pools. Using an automatic (or manual) water suction cleaner, biofouling debris that settles on the inner surface of the rigid basin enclosure during and after vessel hull cleaning is sucked up by the water suction cleaner and filtered before the cleaned water is returned to the basin or the water body it sits within. Alternatively, the water sucked through the water suction cleaner empties into a holding tank for settling, filtration, and cleaning of the water before it is discharged from the holding tank. A manual water suction cleaner is preferably used by divers to clean the hull of a vessel within the rigid basin enclosure. In another embodiment, automatic water suction cleaners attach to, and move about the surface of the vessel hull removing biofouling debris and materials from the hull. [0081 ] A deck attached to the rigid basin enclosure adjacent the upper rim of the basin can preferably be also submerged below the water or raised above the water. The vessel that enters the enclosure by the access portion into the rigid basin enclosure is then releasably attached to the deck. Preferably, by raising the deck using, for example, hydraulic means, or compressed air struts or winched cables, amongst other means, the vessel may also be raised out of the water to enable 'drydocking' work, or lowered back into the water. The 'drydocking' work when the vessel hull is out of the water may include hull inspection, annual surveys, shaft inspection and measurements, running gear inspections, anode replacement, propeller and running gear replacement or service, anti-foul removal, anti-foul application, and any other dry associated type work. An impervious barrier, for example, a curtain-like structure may surround the perimeter of the rigid basin enclosure and deck of the apparatus according to the fourth aspect. This barrier may be up to 1 .8 m high above water level and the purpose of which, is to assist to contain any dust or debris released from working on the hull when raised above the water.

[0082] Vessel Assessment

[0083] In accordance with any of the four aspects described herein, the method comprises the additional prior step of assessing the vessel to determine if biofouling can be removed and collected from the hull of the vessel. The vessel may be assessed according to any one or more of the following criteria before being considered eligible for the method of the invention to be used to remove and collect biofouling from the vessel:

The Anti-Fouling Coating (AFC) name, type of biofouling (biocidal or non- biocidal), last application date and location, and expected life span of AFC;

The travel history of the vessel - local, regional or international since most recent dry dock or biofouling collection regime;

Level of biofouling - rated by stages 1 - 4 (slime to reproductive). If biofouling is at stage 4 then vessel would need to be removed from the water; and/or Consultation with biofouling expert(s) and/or relevant organisations (e.g. Australian Department of Fisheries.

All vessels subject to through initial assessment and those that meet the criteria proceed to in water cleaning within the apparatus.

[0084] The invention according to any one of the four aspects may also incorporate one or more features of another aspect(s) described herein.

[0085] Thus, the method according to the four aspects of the invention can be considered both protective of the environment and beneficial to boat owners and protective of their vessels. This is because environmentally damaging chemicals can be avoided using the method of the invention, the biofouling waste product can be reused in gardening products rather than contaminating marinas and waterways, vessels are not removed from the water avoiding stress on the vessel hull, and the vessel owner does not need to be present when cleaning takes place as the vessel does not need to be moved from its mooring. Since the marinas and other waterways in which vessels are kept in-water are not contaminated with biofouling using the method of the invention, the strict requirements of the ANZECC code and other laws and regulations may be met. As a result, it is more convenient, and cost effective for vessel owners to regularly remove biofouling from their vessels thereby reducing additional fuel use (and the associated emissions) required to overcome the additional drag caused by the presence of biofouling on hulls.

[0086] Modifications and variations such as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Brief Description of Drawings

[0087] The present invention will now be described, by way of example only, with reference to embodiments thereof, and the accompanying drawings, in which:

Figure 1 illustrates a top cross-sectional view of a vessel hull within an enclosure of a preferred embodiment according to the first aspect of the invention; Figure 2 illustrates a perspective view of (A) an inner net, and (B) an outer net for use in an enclosure of a preferred embodiment according to the first aspect of the invention;

Figure 3 illustrates (A) a perspective view, and (B) a top view of an inner net layer and outer net layer for use in an enclosure of a preferred embodiment according to the first aspect of the invention ;

Figure 4 illustrates (A) a partial top view, and (B) a cross sectional side view, of the border of the enclosure of a preferred embodiment according to the first aspect of the invention; Figure 5 illustrates a partial side view of a portion of the border and inner net of the enclosure of a preferred embodiment according to the first aspect of the invention;

Figure 6 illustrates (A) a top view of the border of the enclosure according to a first preferred embodiment of the invention; (B) a partial side view, and (C) a partial top view, showing an air hose joining portions of two inflatable cells of a preferred embodiment according to the first aspect of the invention;

Figure 7 illustrations showing a cross section of a side view of an access barrier of the enclosure of a preferred embodiment according to the first aspect of the invention (A) before lowering; and (B) after lowering;

Figure 8 illustration showing a partial top cross-sectional view of a vessel hull within an enclosure including the access barrier and bubble tubing of a preferred embodiment according to the first aspect of the invention;

Figure 9 illustration showing a top view of the enclosure including zips between portions of the inner net of a preferred embodiment according to the first aspect of the invention;

Figure 10 illustration showing a top view of the enclosure including the position of locator tags used to assist zipping portions of the net together of a preferred embodiment according to the first aspect of the invention; Figure 1 1 illustration showing a partial top view of the enclosure including inflatable cells being inserted and already inserted in sleeve pockets in the border of the enclosure of a preferred embodiment according to the first aspect of the invention; Figure 12 illustration showing a partial top cross-sectional view of a hull in the enclosure including mooring lines used to secure a vessel in position over the enclosure of a preferred embodiment according to the first aspect of the invention;

Figure 13 illustrations showing (A) a side view of a vessel within the enclosure;

and (B) a side view, and (C) a magnified portion of a partial side view of the net retrieval system for retracting or deploying the net, of a preferred embodiment according to the second aspect of the invention ;

Figure 14 illustrations showing (A) a top view of an enclosure with a retracted net ready for deployment, of a preferred embodiment according to the second aspect of the invention ; and (B) the enclosure of a preferred embodiment according to the second aspect of the invention located for use in a boat pen of a marina;

Figure 15 illustrations showing (A) a front view of an enclosure of a preferred embodiment according to the second aspect of the invention located within a boat pen and with a vessel within the enclosure; and (B) a top cross-sectional view showing the location of the bubble tubing within the enclosure of a preferred embodiment according to the second aspect of the invention;

Figure 16 illustrations showing (A) a side view of a vessel within the enclosure with the bubble curtain operating; (B) a partial front view of the bubble tubing apparatus releasing a bubble curtain; and (C) a top view of the lines of bubble tubing and ballast tanks, of a preferred embodiment according to the second aspect of the invention ;

Figure 17 illustrations showing (A) a side view, and (B) a top view, of a mobile apparatus of a preferred embodiment according to the third aspect of the invention; Figure 18 illustrations showing a first part of the process of use of a mobile apparatus of a preferred embodiment according to the third aspect of the invention wherein (A) is a cross-sectional top view of a secured vessel to be cleaned; (B) shows a top view and (C) shows a side view, of the vessel being approached by the mobile apparatus with a retracted net;

Figure 19 illustrations showing a second part of the process of use of a mobile apparatus of a preferred embodiment according to the third aspect of the invention wherein (A) shows a top view and (B) a side view, of the secured vessel surrounded by the mobile apparatus and the net being deployed under the vessel hull;

Figure 20 illustrations showing a third part of the process of use of a mobile apparatus of a preferred embodiment according to the third aspect of the invention wherein (A) shows a top view and (B) shows a side view, of the secured vessel surrounded by the mobile apparatus with the net deployed to form the enclosure and divers cleaning the vessel hull; and (C) shows a top view of the mobile apparatus moving away from the secured vessel, with the net retracted after completion of the vessel cleaning; Figure 21 illustration showing a side view of an inner net layer separated from the outer net layer and being gathered up for removal and disposal of the collected biofouling within the inner net layer;

Figure 22 illustrations showing (A) a top view, and (B) a side view, of the water treatment plant employed in the enclosure of a preferred embodiment according to the second aspect of the invention ;

Figure 23 illustrations showing (A) a top view of a portion of the water treatment plant employed in the enclosure of a preferred embodiment according to the second aspect of the invention with the discharge conduit releasing treated water into the enclosure; and (B) a top and side view of the filtration chambers of the water treatment plant; Description of Embodiments

[0088] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. The invention includes all such variation and modifications. The present invention is also not to be limited in scope by any of the specific embodiments described herein. These embodiments are intended for the purpose of exemplification and illustration only. Functionally equivalent apparatus and methods are clearly within the scope of the invention as described herein. The invention also includes all of the features and/or steps referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the features and/or steps.

[0089] Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference, which means that it should be read and considered by the reader as part of this text. That the document, reference, patent application or patent cited in this text is not repeated in this text is merely for reasons of conciseness. None of the cited material or the information contained in that material should, however be understood to be common general knowledge.

[0090] Manufacturer's instructions, descriptions, product specifications, and product sheets for any products mentioned herein or in any document incorporated by reference herein, are hereby incorporated herein by reference, and may be employed in the practice of the invention.

[0091 ] The invention described herein may include one or more range of values (e.g. size, length, weight, etc.). A range of values will be understood to include all values within the range, including the values defining the range, and values adjacent to the range which lead to the same or substantially the same outcome as the values immediately adjacent to that value which defines the boundary to the range. The invention described herein may include one or more values (e.g. size, length, weight, etc.). A value will also be understood to include (and not exclude) that value as an 'approximate' and not just an 'exact' value.

[0092] Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0093] Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all other technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

[0094] Reference numbers and letters appearing between parentheses in the claims, identifying features described in the embodiment(s) and/or example(s) and/or illustrated in the accompanying drawings, are provided as an aid to the reader as an exemplification of the matter claimed. The inclusion of such reference numbers and letters is not to be interpreted as placing any limitations on the scope of the claims.

[0095] The following embodiments serve to more fully describe the manner of using the above-described invention, as well as to set forth the best modes contemplated for carrying out various aspects of the invention. It is understood that these embodiments in no way serve to limit the true scope of this invention, but rather are presented for illustrative purposes.

[0096] The invention provides an apparatus and method for using the apparatus in the collection of biofouling removed from the hull during in-water cleaning of a vessel.

[0097] Preferred Embodiment - First Aspect

[0098] A preferred embodiment according to the first aspect of the invention is shown in Figure 1 , wherein Figure 1 shows an apparatus comprising an enclosure 20 for surrounding the in-water portion of a hull of the vessel 10. At the surface of the water, the enclosure 20 comprises a border 22 that encircles the hull of the vessel 10.

[0099] Water can pass through at least a portion of the enclosure 20, but biofouling and other matter removed from the hull of the vessel 10 is substantially prevented from passing through and exiting the enclosure 20. [00100] The enclosure 20 is preferably semi-permanently assembled for use within a boat pen (also referred to as a boat slip), for example, in a marina; though it may also be positioned for use, for example, alongside a dock, wharf or pier.

[00101] The enclosure 20 comprises an inner net layer 30 (Figure 2A) and an outer net layer 32 (Figure 2B). The outer net layer 32 forms a substantial portion of the outer boundary of the enclosure 20 (of Figure 1 ). The inner net layer 30 forms a substantial portion of the inner boundary of the enclosure 20 and faces the hull of the vessel 10 to be cleaned.

[00102] The inner net layer 30 and the outer net layer 32 substantially form the shapes of open-topped rectangular prisms, wherein the inner net layer 30 is placed within the outer net layer 32 for use in a close or tight fit where each side of the inner net layer 30 closely aligns with a side of the outer net layer 32.

[00103] The inner net layer 30 is releasably attached to the outer net layer 32 by a number of Velcro ^® tabs 34 on each outer surface of the inner net layer 30 which correspond to matching Velcro ^® tabs 36 on the inner surfaces of the outer net layer 32. Along the perimeter of the open top of both the inner net layer 30 and the outer net layer 32 is a Velcro ^® strip 38 which can be attached to matching Velcro ^® on inflatable cells (described below).

[00104] The inner net layer 30 is constructed from Geo-fabrics® (50 - 100 μηι pore size - filtration). The outer net layer 32 is constructed from Architec 400 ^® (marine grade 600 μηι pore size monofilament yarn).

[00105] Figure 3 shows anchor lines 40 attached to anchor tags 42 along the edges of the bottom of the inner net layer 30 which pass through eyelets 44 along the edges of the bottom of the outer net layer 32 and are secured to anchors or anchor points below the enclosure 20, for example, on the sea bed floor.

[00106] Figure 4 shows the border 22 of the enclosure 20 which comprises: an inner net layer attachment pipe 50 to which the top of the inner net layer 30 attaches; an outer net layer attachment pipe 52 to which the top of the outer net layer 32 attaches; and inflatable cells 54 which float on top of the surface of the water for maintaining the border 22 at the water's surface.

[00107] The inner net layer attachment pipe 50 comprises an empty polyvinyl chloride (PVC) pipe having an approximately 25 mm diameter. The outer net layer attachment pipe 52 comprises an empty PVC pipe having an approximately 100 mm diameter. The diameter of the inflatable cells 54 is approximately 125 mm.

[00108] Cable ties 56 around the inner net layer attachment pipe 50 thread (4 mm paracord) through eyelets 58 positioned approximately every 300 mm or 500 mm adjacent the top edge of the inner net layer 30 to attach the inner net layer attachment pipe 50 to the inner net layer 30 (Figure 4A, Figure 5).

[00109] Components of the border 22 (shown in Figure 1 ) are shown in Figure 6 and comprise a number of inflatable cells 54 and each inflatable cell 54 is joined to another inflatable cell 54 with a hose 58 to form a network of inflatable cells 54 in the border. Each hose 58 comprises elbow joints and is approximately 450 mm long, having a diameter of approximately 12.5 mm and is hollow allowing air to pass through the hose 58 to an inflatable cell 54 it is attached to. A distance of approximately 200 mm is maintained between inflatable cells 54 by a hose 58.

[001 10] Air can be pumped into the network of inflatable cells 54 through an inflation valve 62 to inflate each inflatable cell 54 in the network. Similarly, if the network of inflatable cells 54 in the border 22 need to be deflated, for example, to disassemble the apparatus, air can be let out, or vacuumed out of the inflation valve 62.

[001 1 1] In Figure 6A, the side of the enclosure 20 through which vessels can enter and exit the enclosure 20 is referred to as the access barrier 64. The access barrier 64 comprises two inflatable cells which are not connected to the network of other inflatable cells 54 by a hose 58. Instead, the inflatable cells of the access barrier 64 comprise an inflation valve 62 and can be inflated or deflated independently of the network of inflatable cells 54 in the rest of the border 22 of the enclosure 20.

[001 12] As shown in Figure 7, the access barrier 64 comprises two inflatable cells 55 of equivalent lengths which are attached in the middle. The access barrier 64 also comprises bubble tubing 66 which is located along the length of the top of the inflatable cells 55 and releasably attached at regular intervals with Velcro ^® tabs 68. The Velcro® tabs 68 are placed approximately every 200 mm along the length of the inflatable cells 55 and the bubble tubing 66. One end of the bubble tubing 66 ends at the end of the access barrier 64, while the other end extends beyond the other end of the access barrier 64 and is attached to an air compressor on the dock adjacent the enclosure 20. The bubble tubing 66 comprises a flexible rubber, plastic polymer, or plastic hose with a plurality of holes along its length. Air pumped through the bubble tubing 66 exits through all of the holes as small bubbles forming a 'bubble curtain' 70. [001 13] When a vessel is entering or exiting the enclosure 20, the centre of the access barrier 64 is lowered forming a V-like shape to allow the, often, substantially V-shaped hull of the vessel 10 to pass over the access barrier 64 but with the minimum of space between the outer surface of the hull and the top surface of the access barrier 64. That is, without the hull contacting the access barrier 64 and potentially damaging the access barrier 64 or scraping biological material onto the bubble tubing 66.

[001 14] Importantly, the bubble curtain 70 significantly prevents biofouling and other particulate matter from exiting the enclosure 20 with the normal water currents and those currents created from the moving vessel when the access barrier 64 has been lowered.

[001 15] As shown in Figure 8, inner bubble tubing 72 is attached with Velcro® tabs 68 to the inner net layer 30 between the vessel 10 to be cleaned and the access barrier 64. This provides a second physical barrier through which biofouling must pass to escape the enclosure 20 when a vessel is entering or exiting the enclosure 20. Significant water testing has been carried out during use of the apparatus of the invention with the results of some of these tests shown below. While water inside the enclosure 20 after cleaning one or more vessel hulls was found to contain heavy contamination with biofouling, up to approximately 1 tenth of that contamination was found between the inner bubble tubing 72 and the access barrier 64, and biofouling originating from the enclosure 20 was not found to have contaminated the water outside of the enclosure 20.

[001 16] Both the inner net layer 30 and outer net layer 32 of the enclosure 20 do not have to comprise a single piece or section of netting. In this respect, a single inner net layer 30 for a large boat pen would be extremely large and difficult to set up, store, transport and clean out of the water. Therefore, as shown in Figure 9, the inner net layer 30 and outer net layer 32 may comprise different sections that are connected together when forming the enclosure 20 with large, suitable, marine grade zips 74. These sections may be zipped together on the dock to form the inner net layer 30 and outer net layer 32 or zipped together in the water by divers. The sections of net are approximately 6 m long (and 2 m wide) which corresponds to the distance from the end of one inflatable cell 54 to the middle of the hose between the other end of the inflatable cell 54 and the next inflatable cell 54. [001 17] As shown in Figure 10, colour coded locator tags 75 on the inner net layer 30 and outer net layer 32 at the border 22 assist to match net sections to be zipped together by the zips 74.

[001 18] The inflatable cell 54 is preferably contained within a sleeve pocket 76 which forms part of the border 22 of the enclosure 20 as shown in Figure 1 1 . The key benefit of having a number of removable inflatable cells in the form of inflatable bladders is that if a single bladder is damaged or punctured, it is considerably easier to replace a single bladder in a sleeve pocket 76 of the border 22 when the enclosure 20 is set up and in use in the water, than to replace an inflatable cell that is permanently attached to the border 22 therein requiring the entire border 22 to be separated from the enclosure, moved to the dock and repaired or replaced. Each inflatable cell 54 can be inserted into an end of the sleeve pocket 76.

[001 19] A vessel 10 to be cleaned is reversed into the enclosure 20 according to the invention over the access barrier 64. To secure the vessel 10 in position within the enclosure 20 for the duration of the cleaning process, mooring lines 80 fixed to a roller 82 at the border 22 of the enclosure 20 are hooked onto cleats 84 on the vessel as shown in Figure 12. After the vessel 10 has been cleaned, the air compressor Is turned on to create the bubble curtain, the vessel is unsecured from the cleats 84 and driven slowly over the access barrier 64 such that a minimum of biofouled water exits the enclosure 20. [00120] Preferred Embodiment - Second Aspect

[00121] A preferred embodiment according to the second aspect of the invention is shown in Figure 13, wherein the apparatus comprises a rectangular enclosure 100, the enclosure 100 comprising a border 102 along three sides of hard black poly pipe 104 with a diameter of approximately 500 mm. Two 25 m lengths of poly pipe 104 which form the long sides of the rectangle are joined at a first ('stem') end with a 10 m length of poly pipe 104. An aluminium grid mesh decking platform 106 above the poly pipe measuring 400 mm wide by 25 m serves as a catwalk along each 25 m side length, with a decking platform 106 measuring 1 .6 m x 10 m of aluminium grid mesh above the 10 m poly pipe stern end. Two 2000 kg electric winches for transferring the inner and outer net into position and back for retrieval are located adjacent the two corners where the 25 m catwalks meet the 10 m grid mesh platform 106. A removable catwalk 108 on poly pipe at the second entry end of the enclosure can be manoeuvred out of the way when a vessel is to enter or exit the enclosure.

[00122] A net comprising an outer net layer 1 10 and inner net layer 1 12 with dimensions of 25m L x 10m W x 5.5m D is attached to the border 102. The net consists of four separate segments that are attached together on site when the apparatus is being prepared for use. Figure 13A shows a fully deployed (extended) net within the enclosure 100. The outer net layer 1 10 serves to form the shape and anchor the net in place using anchor lines 1 14, and the inner net layer 1 12 is a fine micron insert that serves to contain all harmful bio-fouling, heavy metals, and other materials. Net attachment lines 1 16 approximately 500 mm long attach the inner net layer 1 12 to the outer net layer 1 10 to maintain the shape of the inner net layer 1 12.

[00123] The two net layers are attached to 3mm stainless steel braided wire cables 1 18 of a net retrieval system which runs along each long side of the border between a 2000 kg electric winch 121 at the stern end and a pulley at the entry end (Figure 13B and Figure 13C). Attachment is by sliding hooks on the metal wire cables 1 18 connected to reinforced stainless steel eyelets 120 every 500 mm along the upper perimeter (edge) of the inner net layer 1 12 and outer net layer 1 10. This enables the nets to be retracted towards the stern end, wherein the net layers concertina together, or deploy and are extended into place using the 2000 kg electric winches 121 to create the rectangular enclosure 100 within the border. A vessel 10 within the enclosure 100 is secured by lines to cleats 122. [00124] Prior to a vessel 10 to be cleaned entering the enclosure 100, if they have not already been set up, the two layers of net in a retracted position are extended along the length of the sides of the border 102 to form the rectangular enclosure 100 (Figure 14A). Stores 124 and operation controls 126 shown in Figure 14A are located on the decking platform 106 at the first end of the enclosure 100. Figure 14B shows the enclosure 100 set up within a boat pen alongside other boat pens, for example within a marina.

[00125] The apparatus of the invention is concerned with the prevention of biofouling and other materials such as heavy metals polluting surrounding waters when removed from the hull of a vessel during in-water cleaning. The importance then in the (i) collection, and (ii) disposal of the biofouling using the apparatus of the invention is the prevention of such materials escaping from the enclosure 100.

[00126] Of most importance is the particular type, quality, strength, and selection of hole or 'pore' sizes of the inner net layer 1 12 to allow water to pass through while retaining the biofouling and other materials within the net enclosure 100.

[00127] Almost of equal importance is the means provided by the apparatus of the invention to prevent biofouling and other materials to escape the enclosure 100 when a vessel 10 enters the enclosure 100 to be cleaned, or to exit the enclosure after the hull has been cleaned. After biofouling has been removed from the hull of a vessel it can take considerable time to settle in the bottom of the net, with some materials not settling but remaining suspended in the water within the enclosure 100.

[00128] A key element of the preferred embodiment according to the second aspect of the invention, therefore, is two means which significantly prevent transfer of biofouling out of the enclosure 100 as a cleaned vessel exits the enclosure 100. The first means is the use of two inflated entry cells 130 shown in Figure 15 which float on the surface of the water and attach to the net along the entry side of the enclosure 100. The inflated entry cells 130 meet at the middle of the entry side of the enclosure 100 and the net comprises a vertical zip 132 which begins where the inflated entry cells 130 meet and both layers of net can be partially unzipped by a diver to create an open triangular portion. When entering or exiting the enclosure 100, a vessel 10 passes across the open triangular portion pushing the inflated entry cells down with the sides of the hull, while the inflated entry cells 130 constantly keep upward pressure on the hull, to minimise any gap between vessel hull 10 and inflated entry cells 130 through which water contaminated with biofouling may pass and escape the enclosure 100.

[00129] The second means acting as a barrier to minimise escape of biofouled water from the enclosure as a vessel 10 exits the enclosure, comprises the creation of a bubble curtain in front of the inflated entry cells 130 and vertical zip 132 just within the entry to the enclosure 100. To create the bubble curtain, bubble tubing 134 is positioned within the enclosure 100 along the net and adjacent to the entry end 101 . An (100 psi) air compressor 136, positioned on the dock 1 1 in Figure 15 feeds air into the bubble tubing 134 to create the bubbles from air exiting the plurality of holes in the tubing. The bubble curtain, as previously described herein, also prevents biofouling from escaping the enclosure 100 when the vertical zip 132 is open and a vessel is entering or exiting the enclosure 100.

[00130] Figure 16 provides more detailed illustrations of the bubble curtain emanating from the bubble tubing 134 during operation within the enclosure 100. Figure 16A shows the biofouling material 5 being forced away from the bubble curtain. In this embodiment, the layout of the bubble tubing 134 creates seven 'curtains' of bubbles adjacent the entry end 101 of the enclosure 100.

[00131] As shown in Figure 16 B and C, ballast tanks 136 attached to the bubble tubing 134 maintains the bubble tubing 134 in position and prevents it from floating to the water's surface during use due to it being filled with air. In this preferred embodiment, the width of the enclosure 100 and bubble tubing 134 is 6 m. Figure 16C shows a preferred number and spacing of bubble holes 138 in the bubble tubing 134 with three lines of holes in the bubble tubing 134 and bubble holes 138 20 mm apart.

[00132] The enclosure according to the preferred embodiment according to the second aspect of the invention is preferably situated in a boat pen or adjacent a dock in a marina. Vessels docked within the marina may then be driven into the enclosure for cleaning before leaving the enclosure to be re-penned or taken elsewhere. Thus, the enclosure and remainder of the apparatus may be set up within the, for example, boat pen for use and then disassembled to be used elsewhere. [00133] Use of the enclosure of the preferred embodiment according to the second aspect of the invention comprises the following steps:

[00134] A vessel requiring cleaning is assessed including use of a qualified dive technician to take photos and video record to determine whether an in-water clean of the vessel is suitable due to: the extent of clean required, anti-foul coating type and state, recent travel history of the vessel, amongst other factors.

[00135] If the thorough assessment shows the vessel is suitable for in-water cleaning using the apparatus, pre-operations checks are conducted to ensure the water depth, dimensions of the vessel, water access, tides and currents, and other factors show the apparatus can be used to in-water clean the vessel and others at that location and time.

[00136] The net used to form the enclosure of the apparatus is set up by joining sections of net together by zips and attaching the inner net layer to the outer net layer. The metal wire cables along the sides of the border are attached by wire hooks to the stainless steel eyelets along the edge of the net to form the net retrieval system described above. After attachment, the net is in a retracted state at the stern end. The winches move the steel cables along the borders of the two long sides of the U-shaped apparatus to deploy the net.

[00137] A vessel to be cleaned is driven to the entry of the enclosure. The air compressor is turned on to fill the bubble tubing and create the bubble curtain emanating from the plurality of holes in the bubble tubing which directs water inside the enclosure to recirculate and remain within the enclosure.

[00138] A diver partially unzips the vertical zip in both the inner net layer and outer net layer in the middle of the entry to the enclosure to form a V-shaped opening in the net layers. The vessel is driven through the entry way through the V-shaped opening in the net layers with the inflated entry cells at the top of the net on either side of the V-shaped opening pushing against the sides of the hull of the vessel. The vertical zip in the inner and outer net layers is closed by a diver after the vessel has passed through into the enclosure and been secured to cleats on the enclosure or the dock adjacent the boat pen. The air compressor is shut off stopping the bubble curtain. [00139] The vessel, now within the enclosure can be cleaned. Preferably, cleaning of the hull is conducted by divers in the water in the enclosure scrubbing the hull using soft ribbed cleaning mitts and soft bristle brushes (chemical-free) with the biofouling debris that has been removed falling into the net below the hull. Cameras attached to the divers provide a video record of the hull clean for evidence of the quality of the clean for the vessel owner and against allegation of damage.

[00140] After the vessel has been cleaned, the bubble curtain is again turned on by starting the air compressor which forces biofouling debris in the enclosure away from the entry. A diver partially unzips the vertical zips in the middle of the inner and outer net layers at the entry enough to accommodate the vessels draft (also referred to as "draught" i.e. depth from waterline to lowest point of the hull) and beam (width measured at the waterline). The vessel is unsecured from the enclosure and/or dock adjacent the boat pen and reversed out of the enclosure over the bubble curtain and through the V-shaped opening at the entry, with the inflated entry cells at the top of the net on either side of the V-shaped opening pushing against the sides of the hull of the vessel as it passes through to minimise water escaping the enclosure with the vessel. Divers in the water of the enclosure ensure that the running gear of the vessel does not snag on the net. The divers then close the vertical zips of the net layers once the vessel has exited the enclosure and the air compressor for the bubble curtain is turned off.

[00141] Preferred Embodiment - Third Aspect

[00142] Moving the apparatus of the invention can be a complex and time- consuming process so in a preferred embodiment according to the third aspect of the invention, the invention comprises a mobile apparatus that may be driven to surround a boat to be cleaned. It may also be driven from one boat pen to another, from storage to boat pen or dock and back again, or from one marina or cleaning location to another, amongst other options.

[00143] The mobile apparatus 200 shown in Figure 17 comprises a U-shaped vessel creating a rectangular enclosure 15 m long by 8 m wide. An operator 202 can drive the mobile apparatus 200 from a console 204 steering two props 206. The net 208 comprising the inner net layer 210 and outer net layer 212 hangs below the mobile apparatus 200. Bow thrusters 214 on the outer sides and near the opposite end of the mobile apparatus 200 to the props 206 enable the operator 202 more accurate manoeuvring of the mobile apparatus 200. The 500 mm wide removable catwalk 216 completes the enclosure within the mobile apparatus 200 at the open end of the U-shape.

[00144] Using the mobile apparatus 200, Figure 18A shows a vessel 10 to be cleaned secured in a pen 218 by guide lines 220.

[00145] In Figures 18B and 18C, the mobile apparatus 200 approaches the vessel 10 to be cleaned with the net 208 retracted at the stern 222. The removable catwalk 216 is removed and temporarily stowed on one side of the mobile apparatus 200. The mobile apparatus 200 manoeuvres towards the vessel 10 until the sides of the U-shape pass outside the sides of the vessel 10 so that the vessel 10 is located within the U-shaped enclosure. Then the removable catwalk 216 is put back into place so that the mobile apparatus 200 fully surrounds the vessel 10.

[00146] The retracted net 208 is prepared by partially unzipping the zips in the inner and outer net layers at the entry end between inflated entry cells according to the vessel's beam and draft V-shape. The retracted net 208 is then deployed along guide wires 224 and extended towards the end of the enclosure with the inflated entry cells pressing against the V-shape of the hull of the vessel as the vessel hull passes through the partially unzipped entry end of the net layers. Once the net 208 has passed beyond the vessel and is fully extended to the end of the mobile apparatus 200 sides, the vertical zips in the net layers at the entry end are re-zipped and the in-water enclosure around the hull of the vessel 10 is complete (Figure 19).

[00147] Working within the enclosure of the mobile apparatus 200, divers 226 clean biofouling 228 from the hull of the vessel 10 using methods described herein. The biofouling 228 collects in the net below or remains suspended in the water as shown in Figure 20A and Figure 20B.

[00148] Once the hull of the vessel 10 has been cleaned, as shown in Figure 20C, the net 208 is retracted to the stern of the mobile apparatus 200 collecting the biofouling 228 in the net 208. This involves the steps of: partially unzipping the vertical zips in the entry end of the inner net layer and outer net layer; slowly retracting the net 208 to the stern end of the mobile apparatus 200 using the wire cable net retrieval system attached to winches, with the inflated entry cells pressing against the V-shape of the hull of the vessel as the vessel hull passes through the partially unzipped entry end of the net layers; re-zipping the vertical zips in the inner net layer and outer net layer of the now retracted net; removing the removable catwalk 216; reversing the mobile apparatus 200 to manoeuvre it away from the vessel 10; replacing the removable catwalk 216; and driving the mobile apparatus 200 to the dock for disposal of the biofouling 228, or to the next vessel to be cleaned.

[00149] During the retraction of the net 208, a bubble curtain may also be created in front of the inflated entry cells and vertical zip just within the net 208. To create the bubble curtain, bubble tubing may be attached to the net 208 which is fed by compressed air from an (100 psi) air compressor positioned on the mobile apparatus 200. The bubble curtain also assists to prevents water contaminated with biofouling from escaping the enclosure 100 when the vertical zip is open and the net 208 is being retracted beneath the hull of a vessel 10 that has just been cleaned within the mobile apparatus 200. [00150] The removable catwalk 216 provides stability for the mobile apparatus 200 when moving between locations and access for when cleaning and deploying the net 208 to form the enclosure.

[00151] Removal of Biofouling - Inner Net Removal

[00152] In a first biofouling removal method, after some 50 - 75 vessel hull cleans or when the biofouling load exceeds 750 kg (net weight wet with net approximately 1000 kg), the inner net layer (according to any of the first, second, or third embodiments) is preferably removed for cleaning. It will also be replaced if the pores appear too clogged which reduces the efficiency by which water can exit the net when it is retracted or removed from the water, or there is damage to the inner net layer. This inner net layer removal method for disposing of biofouling can be used with any of the three preferred embodiments according to the first, second, or third aspects of the invention.

[00153] Figure 21 shows one non-limiting example of a means of disposing of the biofouling 128 collected within an inner net layer 210. The inner net layer 210 is separated from the outer net layer 212 and gathered up by tightening the guide wires or paracord threaded through the eyelets along the opening of the inner net layer 210. [00154] A preferred method for removing the biofouling containing inner net layer from an enclosure according to the preferred embodiment of the second or third aspect (when the mobile apparatus has been driven to a dock) of the invention comprises the steps: retracting the net layers to the stern of the enclosure (for the preferred embodiments according to the second and third aspects of the invention). A 12-point lifting harness is set up attached to a crane on the adjacent dock. Each of the 12 points is matched up with a correct eyelet on the edge of the inner net layer (colour coded) and attached by snap clips. The crane lifts the gathered inner net layer by the harness out of the water and away from the outer net layer and allows the water in the net to drain out. The crane then moves the gathered inner net layer over to a waiting vehicle on the dock where it is deposited and unharnessed, to be taken away for biofouling disposal at appropriate locations, and cleaning or replacement of the inner net layer.

[00155] A similar method can be used for net retrieval from an enclosure according to the preferred embodiment according to the first aspect of the invention except personal and divers have to manually drag the edges of the net towards the stern end for attachment to the harness and crane.

[00156] Removal of Biofouling - Water Treatment

[00157] In a second biofouling removal method, preferably employed in the preferred embodiment according to the second aspect (but could be used with the embodiments according to the first or third aspects) of the invention, is a water treatment plant 300 which is located on the decking platform 106 of the first or stern end of the U-shape enclosure 100 (Figure 22).

[00158] The water treatment plant 300 comprises an intake conduit 302 which draws water near the bottom of the net where the highest concentrations of biofouling and other materials are present following vessel hull cleaning.

[00159] Biofouled water is drawn into and through the conduit until it reaches the filtration unit 304 which comprises four filtration chambers 306 comprising different filter substrates. These filter substrates range in pore size to ensure different sized particles are filtered out by at least one filter substrate. The first filter substrate is a 200 m marine grade mesh; the second filter substrate is a 150 μηι fibre and block filter arrangement; the third filter substrate is a 100 μηι fibre and block filter arrangement the fourth filter substrate is a 50 μηι block of perforated fibre blocks. The contents of each filtration chamber 306 is enclosed within a stainless steel cartridge and each of the filter substrates may be removed individually for repair, replacement, or cleaning. The water is filtered and cleaned as it passes through the filter substrates in the filtration chambers 306 and exits back into the enclosure via the discharge conduit 308 which releases water at different intervals by incorporating discharge holes 310 at various intervals in the discharge conduit 308 near the surface of the water (Figure 23A). The intake conduit and discharge conduit 308 comprise 4 inch diameter pipes. [00160] Figure 23B shows the top and side view of the filtration unit 304 comprising the four filtration chambers 306 separated by three filtration screens 310. The filtration screens 310 may be removed for cleaning or replacement. Inspection windows 312 enable viewing into each filtration chamber 306.

[00161] The filter substrates are replaced or cleaned periodically to ensure functioning of the water treatment plant 300 and removal of the biofouling from the enclosure water. The water treatment plant 300 comprises a pump for drawing the biofouled water up through the intake conduit 302 and through the filtration chambers 306.

Water Quality Trial [00162] Scope

[00163] An independent contractor provided water testing services for a field trial of the vessel hull cleaning system using the apparatus according to the preferred embodiment according to the first aspect of the invention described herein. The field trial was conducted in the marina of the Fremantle Sailing Club in Fremantle, Western Australia. The trial was aimed at evaluating the effectiveness of the net system in containing potential pollutants (Copper and Zinc - a previous trial in this area showed Cu and Zn as the only metals showing significant elevation above background) generated during the parts of the process covering the cleaning of a vessel. A field sampling plan was developed and the independent contractor attended the field trial to observe the collection of water samples for analysis. The independent contractor was responsible for managing the laboratory which conducted the chemical analyses and for describing the results from the analysed field samples.

[00164] To evaluate the metal concentrations in the marine environment during the use of the system of the invention, water samples were collected during a trial cleaning conducted on a vessel which was moored and enclosed within the double net layer of the apparatus according to the invention. Once the vessel was fully enclosed in the nets, the hull was cleaned. To remove the vessel from the pen, one side of the wall was lowered and the vessel pulled forward while divers held the pen walls close to the vessel's hull. The pen was then re-sealed and the inner net layer was lifted out of the water. The fate of the net or materials trapped inside the net after cleaning were outside the scope of this study and not considered herein.

[00165] Sampling Design

[00166] Water samples were collected by the divers from both reference and test sites at a constant depth of 1.5 m. Reference sites were sampled prior to the cleaning of the vessel while test sites were sampled mid-way through the cleaning of the vessel and during the net extraction. Samples were taken at five sites each for: (i) inside the net during cleaning, (ii) outside the net during cleaning; (iii) outside the inner net during removal; and (iv) residue from within inner net. Divers wore nitrile gloves during all sampling. At each of the sites, two types of water sample were collected. Samples collected to test for dissolved metals were filtered through a Pall Acrodisc ^® Ion Chromatography 0.45 pm filter before being placed in laboratory-supplied sample jars prepared for metals analysis. Samples tested for the total metal concentration were collected in acid washed 100 ml sample jars. Samples were collected from water in front of divers by syringe or by opening and inverting sample jars.

[00167] Reference sites were located at various locations within the Fremantle Sailing Club marina and were within 100 m of the site where the vessel was cleaned. Additional baseline samples collected earlier in the year from within the marina as part of a separate study were taken from within 250 m of the site where the vessel was cleaned. Test samples collected during the cleaning process were obtained from within the net of the apparatus according to the invention and from immediately outside the net. After the cleaning was completed, the vessel was removed and the water inside the net was allowed to settle for approximately 10 mins. The inner net layer was then attached to a crane and lifted until the inner net occupied approximately half of the total net pen area. At this point, water samples were collected from the water outside the inner, partially lifted, net but still within the outer net layer. No samples were collected from the water contained within the outer net layer once the inner net had been fully removed or from the waters surrounding the outer net during or after removal of the inner net. Samples of solid material were collected from the residual material which was captured by the inner net layer following its removal from the water. Residue was collected using a Teflon ^® scoop and placed directly into acid washed sample jars. [00168] Following collection, all samples were recorded on a standard chain of custody form and stored in a dark chilled cooler for transfer to the assay laboratory. Samples were submitted to the ChemCentre of Western Australia (ChemCentre) on the same day as collection for subsequent chemical analysis. The analytes, assay methods and levels of detection used by the ChemCentre to assay the samples are detailed in Table 1 .

[00169] Table 1 : Analytes, Detection Limits and Assay Methods

[00170] Data Analysis

[00171] To compare metal concentrations during vessel cleaning and net extraction to reference data, mean concentrations of analytes in samples collected within the net during cleaning were compared to the mean of samples collected outside the net during cleaning and those collected between the net layers during net extraction using a series of t-tests. Baseline samples collected in the marina prior to cleaning were also compared to those collected outside the nets during vessel cleaning and to samples collected between the net layers during net extraction using t-tests (only baseline samples collected on the same day as test samples were included in the aforementioned analyses). Median values of sample sets from inside and outside the net, as well as those from between the net layers during net extraction were then compared against the 80 ^th percentile of data from samples within the marina to align with ANZECC-ARMCANZ criteria (ANZECC & ARMCANZ 2000). As ANZECC-ARMCANZ standards suggest sampling over an extended baseline is required to derive a representative 80th percentile background parameter estimation, baseline samples collected from a month earlier were included in the 80 ^th percentile calculation for the present study. The same tests were done for both dissolved and total metals in seawater.

[00172] Due to the number of t-tests which were used to analyse the data, a Bonferroni Adjustment was applied to the a value of 0.05 (0.05 / 5 t-tests) resulting in an adjusted significant threshold of 0.01.

[00173] The raw data samples were also assessed for the presence of outliers, using the criteria set out by ANZEC-ARMCANZ, in which any value greater than three standard deviations from the mean value can be reasonably excluded from analyses (ANZECC & ARMCANZ 2000). Any value which met the aforementioned exclusion criteria was individually assessed to further evaluate whether or not it could be reasonably removed from the analysis dataset. [00174] Results and Discussion: Water Samples

[00175] The statistical basis of the following results is set out in Tables 2 to 8. In interpreting these results, it should be noted that a net will not contain dissolved metals unless it stops water movement. Total metal levels, which include metals in suspended particulates will be subject to some degree of retention by nets. · Copper and Zinc levels in the marina were lower than those detected in the same area during an earlier trial; • Mean concentrations of dissolved Copper were low (compared to background levels in the marina) and not significantly different between any of the sample types;

Concentrations of total Copper were similar in the marina and outside the net during cleaning, but below levels found inside the inner net when cleaning and between nets during removal: however, the only statistically significant difference was between the marina sample and the between nets sample means;

Mean concentrations of dissolved Zinc were not significantly different between any of the sample types: although the means of the samples taken inside or between the nets were above those of the marina and outside net samples, high levels of variation within these samples prevented that difference being statistically significant;

Concentrations of total Zinc showed a similar pattern to that of dissolved Zinc, although in this case the mean of total Zinc inside the inner net during cleaning was statistically greater than the mean concentration found outside the nets during cleaning;

• The concentration of both dissolved and total metals from inside the net during cleaning, during net extraction and outside the net during cleaning were within ANZECC guidelines. 176] Table 2: Summary of Mean Detectable Metal Concentrations

n.v.— no variation between samples [00177] Table 3: Results of t-test analyses comparing baseline marina samples to those collected outside the net during vessel cleaning: i.e. [outside] - [marina]. Bold values are significant.

[00178] Table 4: Results of t-test analyses comparing baseline marina samples to those collected inside the net during cleaning: i.e. [marina] - [inside]. Bold values are significant.

[00179] Table 5: Results of t-test analyses comparing samples collected outside the net during vessel cleaning to samples from inside the net during vessel cleaning: i.e. [outside] - [inside]. Bold values are significant.

[00180] Table 6: Results of t-test analyses comparing baseline marina samples to those collected between the net layers during net extraction. Bold values are significant.

[00181] Table 7: Results of t-test analyses comparing water samples collected from within the net during vessel cleaning to those collected between the net layers during net extraction. Bold values are significant.

[00182] Table 8: Comparison of median metal concentrations inside and outside the net during cleaning with the 80th percentile of background data (values rounded to 2 places). Bold values exceed reference site 80th percentile triggers (ANZECC & ARMCANZ 2000).

[00183] Overall, during the cleaning operation, neither Copper or Zinc, either total or dissolved, were greatly elevated (that is they were not an order of magnitude above background) within the containment structure. During the cleaning process, most Copper or Zinc elevation resulted from liberation of particulates rather than dissolved metals. The higher levels of total Copper and Zinc found inside the inner net during cleaning when compared to levels recorded outside the net at the same time show it is retaining particulates during the cleaning operation.

[00184] Results and Discussion: Residue Samples [00185] Residue collected from the inner net layer after removal from the water revealed significant concentrations of Copper and Zinc (Table 9). [00186] Note: As the net layers had been in place for several days prior to the present study, this material had accumulated from cleaning of several vessels.

[00187] Table 9: Summary of results (highlighted values are those which exceeded the 80 ^th percentile metal concentrations for reference sites)