EP2288755A1

EP2288755A1 - Contaminant recovery device for contaminants on watersurface

Info

Publication number: EP2288755A1
Application number: EP08719086A
Authority: EP
Inventors: William Lloyd
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-04-03
Filing date: 2008-04-03
Publication date: 2011-03-02
Also published as: WO2009122117A1

Abstract

A contaminant recovery device (10) for recovery of contaminants in water, the device comprising a housing (12), a passageway (14) extending through the housing and having an inlet (16) at one end and an outlet (18) at an opposite end, a liquid guide surface (28) at the inlet end of the passageway (14) and means for positioning the liquid guide surface (28) in or under the layer of contaminant, whereby forward motion of the device (10) in the water causes said contaminant to flow or pass over the liquid guide surface (28) into the passageway (14).

Description

CONTAMINANT RECOVERY DEVICE FOR CONTAMINANTS ON WATERSURFACE

The present invention relates to a contaminant recovery device, more specifically a device for removing contaminants which, when spilled onto, or when produced in, water float on or near its surface, for example oil, other organic material or rubbish.

The present invention will be described mainly with regard to oil recovery, although it is not limited to the recovery of this specific contaminant. Oil spillage into the sea or rivers, whether it is the result of a fractured pipeline, the ruptured tank of an oil tanker or unauthorised or accidental discharge, can result in widespread and long term ecological damage to marine life, either as a result of direct contamination or due to the disruption of the food chain resulting from this contamination. Many types of oil recovery devices and systems have been devised to cope with oil spillages when they occur.

One of the more recent systems, commercially known as the "MOP" system, comprises in one embodiment a catamaran type boat having a central longitudinal passageway formed by the underside of the hull. Disposed in this passageway are a plurality of looped rope mops which circulate onto the water at the bow of the vessel, are pulled through the oil and are then returned to the bow via an under-deck roller near the stern. At the bow, the oil saturated rope mops pass through deck mounted wringers which press the oil from the rope mop into a collection sump. Another embodiment of this type of device comprises an independent looped rope mop unit which is secured to the deck of a boat. The mops are deployed from the boat into the water and are pulled behind it. The mops are circulated back to the boat where wringers separate the absorbed oil from the mop.

Another oil recovery system employs disk skimmers. These devices comprise a set of vertically disposed rotating discs. As the discs rotate, the oil, being of greater viscosity that the water with which it is mixed, adheres to the plates. Once the oil has been removed from the water, the oil is scraped from the disc surface and passes into a collection tank. Other related devices comprise rotating rollers or belts to which the oil adheres.

Another "skimmer" type device comprises a main body having a horizontally disposed inlet aperture and optionally a set of smaller, vertically disposed apertures, adjacent and below the main aperture, which lead into the main aperture. The body is supported in the oil by one or more buoyancy tanks such that either all the apertures (in the case of heavy crude oil recovery) or just the smaller apertures (in the case of lighter contaminant recovery) are under the oil surface. A pump sucks the oil through the apertures and into the device from the surrounding area. Any of the above mentioned devices can be used in combination with an oil boom which floats on the water surface. The boom provides a physical barrier to the spread of oil and may be used either to partition a particular area of water to prevent further spread or may be drawn through the water by a boat to collect and concentrate the oil before it is removed by one or other of the aforementioned devices.

The oil recovery systems of the prior art share common problems. Such devices are complex and have many moving parts which results in them being expensive both to buy and maintain. They are also inefficient in the manner in which they remove oil from the water.

More specifically, recovery systems of the "MOP" type require expensive drive rollers and mechanical wringers and once the mops have been circulated through the oil a number of times, their efficiency is lost and they must be replaced.

Skimmers and roller devices require electricity generators to power them and a pump to remove the collected oil to tanks. Furthermore, as the skimmer works on the principle of being positioned on the water and then drawing oil into it from the surrounding area, efficient working of the system requires the skimmer to be at least partially enclosed by an oil boom which is used to stop the oil spreading and to concentrate it near the skimmer.

There is therefore a need for a more efficient and economic device for recovery of various types of water contaminant including oil, other chemical pollutants and algae and its by-products. In accordance with the present invention, there is provided a contaminant recovery device (CRD) for recovery of contaminants in water, the device comprising a housing, a passageway extending through the housing and having an inlet at one end and an outlet at an opposite end, a liquid guide surface at the inlet end of the passageway and means for positioning the liquid guide surface in or under the layer of contaminant, whereby forward motion of the device in the water causes said contaminant to flow or pass over the liquid guide surface into the passageway. In one embodiment the contaminant/water mixture will flow directly into floating storage containers attached to the outlet of the device.

Alternatively the device may contain a contaminant separation unit or the contaminant may pass from the device into a separate separation unit.

The advantage of the present invention over the prior art is that it allows the operator to "attack" the contaminant spill. This in turn reduces the need to contain a spill with booms. Furthermore the device comprises, in its simplest form, no complex and expensive moving mechanical parts, nor does it rely on pumps to remove oil from the recovery site or require an electricity generator for power. Other contaminants such as algae, especially blue-green algae, may also be removed from water using the present device.

If water is enriched with nitrogen and phosphorus, then blue-green algae may form blooms in ponds, lakes, reservoirs and the sea. Blooms can adversely affect the appearance, quality and use of the water. In calm water blue-green algae can rise to the water surface to form a scum. In less settled conditions, foaming can occur.

When the blue-green algae blooms die and decay, they use up oxygen in water which can cause problems for aquatic life including fish. The algae are also capable of producing toxins, which have caused the death of wild animals, farm livestock and domestic pets.

In one embodiment the liquid guide surface is formed by the inlet of the device. Preferably, the depth of the liquid guide surface device, in the contaminated water, is adjustable so as to optimise the ratio of contaminant to water recovered. This may be done for example by filling and emptying ballast or buoyancy tanks on the device.

In another embodiment the liquid guide surface may be movable relative to the housing and may be raised and lowered into the water.

More preferably, the angle of the liquid guide surface relative to the water surface may be adjustable and more preferably still may be movable forwards and backwards on the device.

The first edge of the liquid guide surface can be manually adjusted before the CRD is placed in the water, or it can be manually adjusted when the CRD is in the water.

The liquid guide surface can be raised/lowered using an electric pulley system, which can be powered using an on-board battery or a remote battery. The depth of the liquid guide surface can be infinitely variable or variable between discrete pre-set positions. A multi-position switch or a remote control unit may be provided for adjusting the depth of the liquid guide surface. The liquid guide surface may be formed by an adjustable plate. Optionally the plate may comprise upright blades to guide the contaminant into the channel.

Preferably, at least part of the device below the inlet is streamlined to facilitate movement of the device through the water.

The device may be made of any light, resilient material such as glass- reinforced plastics or carbon fibre or alternatively could be inflatable and be reinforced with rods of resilient material.

The device may be propelled through the water by any means. In one embodiment it may be pulled through the water by one or more watercraft, or attached between, or to the side of, one or more craft. Alternatively the device may be self-propelled and be provided either with a cockpit for a pilot or a control unit to allow remote operation.

A second aspect of the invention provides a contaminant recovery system for recovery of contaminants in water, comprising a movable contaminant recovery device adapted recover the contaminants by skimming the surface of the water as it moves across it, the contaminant recovery device comprising a passageway for directing the collected contaminants and water towards an outlet, a separator connected to and arranged to receive the contaminants from the outlet, the separator being further arranged to separate the at least some of the water from the contaminants, and a storage unit into which the contaminants and/or water are dischargeable. The CRD is preferably connected to a collector unit. The collector unit preferably comprises a separator and a storage unit, which can be combined in a single unit, or which can be separate units.

The collector unit preferably comprises a floating platform that can be towed behind the CRD. A connector pipe is preferably provided for connecting an outlet of the CRD to an inlet of the collector unit. Thus, contaminants can be skimmed off the water surface by the CRD and discharged into the collector unit.

In a preferred embodiment of the invention, the collector unit comprises separate separator and storage units.

The main purpose of the separator unit, where provided, is to separate, as far as practicably possible, the contaminants from the water. Whilst attaining 100 % separation of contaminants from the water would be ideal, practical constraints generally make this goal unachievable. A separator unit can be chosen depending on the specific circumstances of the clean up operation being undertaken.

For example, if the clean up operation is intended to clean up relatively large objects from the water (e.g. flotsam), the separator might simply need to be a sieve that allows water to flow through, but not objects such as flotsam. The grid spacing of the sieve can be selected to optimise the collection process whilst minimising adverse effects.

In another possible scenario, say where it is intended to clean up algae or bacteria from the water, a micro-filter system, a chemical separator or a biological separator may be more appropriate. In cases where very small particles are to be separated from the water, a cyclonic separator may be used.

In the case of an oil spill, the separator may need only comprise a holding/settling tank because oil and water are immiscible and therefore separate by themselves. In this case, a holding tank may be provided which is filled with the oil-water mix collected by the CRD. Once filled, the oil-water mix in the tank can be left to stand, whilst another tank is filled using the CRD. After a period of time, the oil and water will have separated, to a greater or lesser extent (depending on the properties of the oil and water), such that a layer of oil floats on top of the water. By carefully draining the holding tank from a point below the oil-water interface, un-oiled water can be removed from the holding tank. The tank can then be re-filled and the process repeated. In this way, a greater proportion of oil and a lesser proportion of water can be collected.

A multi-stage separator may be used. For example, the separator may comprise a sieve for removing flotsam from the water, followed by an oil separation tank for removing oil from the water. The water could then be micro-filtered before being discharged back into the waterway. Once a desired quantity of contaminant has been removed from the water by the collector, it can be transferred to a storage unit. This may occur by emptying the separator unit into a separate storage tank, or by sealing and moving the separator to a different position and replacing it with another one. In a most preferred embodiment of the invention, separation can take place continuously by multiplexing the separator unit such that when one separator is being used, another is being moved to or discharged into the storage unit. In this preferred embodiment, continuous operation of the CRD is thereby only interrupted by discontinuities in the supply of separator or storage equipment.

The separator unit is preferably towed behind the CRD. The storage unit or units can either be towed behind the CRD or, where they have positive buoyancy, jettisoned for later collection. Where the storage unit or units are jettisoned, the risk of secondary contamination can reduced by providing double-walled tank skins and/or multiple seals/valves to reduce the likelihood of egress of contaminants from the storage unit.

Of course, the separator unit is optional because the raw contaminant- water mix could simply be collected in storage tanks to be taken to another site to be separated, decontaminated or otherwise processed.

In an alternative embodiment of the invention, multiple CRDs can be connected via connecting tube links to a central separator/storage unit. Such a setup might be useful in places where relatively small-scale contamination leaks are commonplace, such as near oil refineries or in harbours. The outlet of the or each CRD can thus be connected to the central separator unit and used in the normal way, except that the contaminants are discharged into the connecting tube rather than directly into the separator/storage unit. The contaminant-water mix can be pumped along the connecting tube to the central storage unit for subsequent processing. Conveniently, a separator unit can be provided near to the storage unit such that the water component of the contaminant-water mix can be discharged back into the waterway prior to transporting the contaminant. Such an arrangement is likely to save on transport costs and reduce any negative environmental impact.

Where multiple CRDs are connected via connecting tubes to a central separator/storage unit, it may be convenient to provide a floating pontoon or distributor to which multiple CRD connecting tubes can connect. Using such a system, a clean-up operation can be concentrated in a particular area (i.e. by having multiple CRDs working together) whilst only having one take-off pipe leading back to shore. This may reduce the likelihood of the CRD connecting tubes becoming tangled and reduces any obstruction presented to other vessels.

The contaminant recovery device may further comprise a raising means for raising submerged contaminants to or towards the surface of the water.

Preferably, the raising means comprises one or more jets, connectable to a gas supply, positioned in front of and below the liquid guide surface.

By supplying a flow of gas to the jet or jets, gas bubbles can be created in front of and below the liquid guide surface. Thus, as the bubbles rise to the surface, they create an upward current such that the submerged contaminants are raised to or towards the water surface. Once at or near the water surface, the contaminants can be collected using the liquid guide surface of the contaminant recovery device.

Conveniently, the gas can be air supplied using an air compressor. The air compressor may be located on board the contaminant recovery device and conveyed to the jet or jets using one or more hoses.

Compressed gas may be provided in cylinders that can be removably mountable on the contaminant recovery device.

Additionally or alternatively, the gas may be mixed with a reagent. For example, if the water has been turned acidic by the presence of the contaminant, then by mixing the air supply with a basic (alkali) gas, liquid or powder, the water can be neutralised simultaneously with the clean-up operation. Conversely, alkali water can be neutralised by mixing an acidic gas, liquid or powder with the air supply.

In one embodiment, the jets comprise small holes drilled in a tube having sealed ends. The gas supply is fed into the tube via a hose and gas escapes as bubble jets through the holes. The tube can be positioned in front of and below the liquid guide surface by mounting it on arms. The arms can be positioned using actuators and the gas supply controlled to achieve an optimum bubble distribution in the water. In a preferred embodiment of the invention, a module is provided that is attachable to the underside of the of the contaminant recovery unit. In the preferred embodiment, the module comprises a housing for housing a plurality of telescopically extendible pipes. One end of each pipe (the onboard end) is connected to a gas supply and the other end is sealed. The pipes have holes at various locations such that when gas is supplied to one end of the pipe, it emerges, in use, as bubbles through the holes. Because the pipes are telescopically extendible, the position of the bubbles in the water relative to the contaminant recovery device (CRD) can be optimised.

Fish farms are normally found close to shore and in shallow waters. In most cases the fish are held in nets/cages, and many thousands of fish may be in a cage at any one time. Fish farms cause an acute and highly localised problem of pollution from faeces and food pellets. They pass through the nets/cages and accumulate beneath the cages, causing de-oxygenation of the water, which can change the whole balance of wildlife communities. Solid matter also causes enrichment of the water (Eutrophication) and may encourage population blooms of phytoplankton, some of which cause highly toxic substances. These problems can cause mass mortalities of fish and other wildlife and would be associated with paralytic shellfish poisoning in humans.

A U.S.A. study has shown that a 20-acre salmon farm produces as much organic waste as a town of 10, 000 people. Fish die from toxic algae blooms in hot weather. At feeding times as much as 25% of food pellets is lost through the nets/cages. The fish are swimming in their own faeces, this can encourage lice, which can eat away at the fishes sensory system. Many fish die this way. To address the problems, the CRDs contaminant units can be brought in close proximity of the net/cages. At feeding times the pipe system under the CRD can be expanded under the net/cages. The air released from the high powered jets blows any escaping food pellets back into the nets/cages, thereby reducing feed cost and build up of organic waste under the nets/cages.

With suction pipes also fitted to the CRD, the organic waste under the nets/cages can be sucked directly onboard the decks of the CRD units and exit quickly into containers or into pipeline which runs from our unit to shore, were it is gathered into skips for use as fertiliser.

If the high pressure jets are trained under the nets/cages, and come into contact a fish body, this may release the lice which will be blown upwards onto the water surface, were they will be brought onboard using rotating paddles. Additionally, it is believed that the high pressure jets, when trained on the fishes body may cause stimuli which will be of benefit to the fish's health and growth.

The CRD may preferably further comprise a sweeping means associated with the liquid guide surface for sweeping the contaminants into the CRD. Such an arrangement may be useful where the contaminant comprises flotsam or viscous material that could not easily be collected using the skimmer alone. The sweeping means preferably comprises a rotatable drum having blades and/or bristles thereon mounted above and/or in front of the liquid guide surface. Rotation of the drum in an appropriate direction at an appropriate speed could be used to sweep the contaminant up the liquid guide surface into the CRD. The drum, where provided, is preferably motor- driven. The blades and/or bristles can be manufactured of an easily cleanable material (e.g. so that oil etc can be removed from the surface thereof relatively easily) and/or may be disposable or removable.

Preferred embodiments of the invention shall now be described, by way of example only, with reference to the accompanying drawings in which;

Fig. 1 is a perspective view of an embodiment of a CRD in accordance with the invention;

Figs. 2 to 5 are respectively plan, underside plan, side elevation and front views of the CRD of Fig. 1 ;

Fig. 6 is a schematic longitudinal cross section through the CRD of Fig.

1 ; Fig. 7 is a schematic perspective view of an assembly of the CRD of

Fig. 1 connected to a separator unit and a storage unit;

Fig. 8 is a schematic plan view of the assembly of Fig. 7;

Fig. 9 is a schematic perspective view, in more detail, of the separator unit shown in Fig. 7; Figs. 10 and 11 are perspective schematic views of the separator unit shown in Fig. 7, with tanks removed;

Figs. 12 and 13 are diagrams showing possible modes of operation of the separator unit; Fig. 14 is a schematic plan view of telescopically extendible tubes used to create a bubble jet ahead of the CRD;

Fig. 15 is a schematic transverse cross-section through a bed scarifier connectable to a CRD; Fig. 16 is a plan view of a distributor unit;

Fig. 17 is a schematic showing how the distributor unit can be put to use; Fig. 18 is a schematic side view of a sweeper unit for a CRD;

Fig. 19 is a perspective view from above and in front of an catamaran version of CRD in accordance with the invention; and Fig 20 is a perspective view from above and behind of the CRD of Fig

19.

Referring to Figs. 1 to 5, the contaminant recovery device (CRD) 10 comprises an elongate housing 12 having a central raised bulbous portion 13 through which a longitudinal passageway 14 extends, linking an inlet aperture 16 and an outlet aperture 18 located at opposite ends of the passageway. Attached to the outlet aperture 18 is a flexible outlet pipe 20.

The front of the bulbous portion 13 of the housing 12 is formed into an overhanging lip to protect the inlet aperture 16. The housing 12 is tapered towards the rear to channel / concentrate the water-contaminant mix as it flows through the passageway and also for aerodynamic effect.

A rearwardly inclined plate 26, preferably made of metal or other sturdy material, sits on the passageway floor 22 adjacent the inlet aperture 16 such that its leading edge 28 protrudes forward out of the aperture 14. The plate 26 is substantially flat apart from upright blades 30 on its opposite side edges. The plate 26 is adjustably attached to the housing 12.

Four elongate, parallel buoyancy tanks 34 are disposed on the undersurface 32 of the housing 12 extending parallel to the longitudinal axis of the passageway 14, which help support the housing 12 in the water and may be filled or emptied to alter the height of the device 10 relative to the water.

The device 10 is further supported, and propelled through the water, by two "Avon" ^R™ type inflatable watercraft 36 to which it is secured by two sets of hooks 38 fixedly located one along each side of the housing 12, which hook over an inflatable elongate pontoon side member 39 of each of the two craft 36.

In operation, the device, propelled by the inflatable watercraft 36, moves forward through the contaminated water and the plate 26 is adjusted such that its leading edge 28 is angled downwards into the contaminant mixture so that it is preferably level with the bottom of the floating contaminant layer. The forward movement of the device 10 causes the floating contaminant to flow up the plate into the passageway 14 and from there into a floating separator/collector unit (not shown) attached to CRD unit by flexible outlet pipe 20. The cross-sectional area of the passageway 14 is greater towards the inlet end thereof than towards the outlet end thereof.

This causes the water-contaminant mix to accelerate as it flows through the passageway, which helps to compensate for frictional/viscosity etc. losses. In this embodiment, the plate 26 may be adjustable by means of a slidable pivot arrangement (not shown) attaching the uprights 30 of plate 26 to the side walls of the housing 12.

In an alternative embodiment, the passageway floor 22, adjacent the inlet aperture, may be inclined such that the plate 26 can slide forwards into the contaminated water to the required depth. The plate 26 may additionally be pivoted to provide greater flexibility of movement.

Alternatively, the height of the housing 12 in the water may be adjusted, for example, by altering the inflation of the buoyancy tanks 34. Therefore in one operational mode, part of the inlet aperture 14 may be below the water surface. However this mode is less preferred as it will lead to increased drag of the device in the water.

In Fig. 6, it can be seen that the floor 22 of the channel 14 is shaped to inhibit or prevent flow back of water/contaminant. The flow of water/contaminant is indicated schematically by arrow F. The liquid guide surface 26 is positioned such that its leading edge is below the level of floating contaminant. Forward movement of the CRD causes the contaminant to be skimmed off the water surface, up the liquid guide surface 26 and into the opening 16 of the channel 14. Due to the forward motion of the CRD₁ the contaminant/water is able to flow up over an inclined weir surface 23 within the channel 14. The weir 23 has a smooth surface and rounded profile to offer the least possible resistance to water flowing over it. The weir 23 has a steeper trailing edge 23' than leading edge 23" so that flow IS

of water/contaminant along the passageway towards the outlet 18, in direction F, is much easier than in the opposite direction.

The interior of the CRD can be fitted with high pressure nozzles (not shown) so that the interior surfaces and/or the contaminated water can be sprayed either continuously or intermittently.

Additionally or alternatively, a non-return valve, such as the flap valve 25 shown in Figure 6, may be provided in the channel 14, outlet 18 or tube 20 to prevent or inhibit flowback of recovered material through the device.

In Figs. 7 and 8 the CRD 10 is shown connected via the connector tube 20 to an inlet 40 of a separator/storage unit 42, The separator/storage unit 42 comprises an open, outer support frame 44 comprising upper and lower pairs of parallel frame members, upper and lower pairs of parallel, lateral frame members and front and rear pairs of upright members connected at ends thereof to each other using right angled brackets. The frame members are tubular to reduce weight. The frame is mounted on a floating deck 46. Additional buoyancy is provided by four elongate, closed- ended inflatable tubes 48 attached outwardly of the deck 46. The outer frame 44 is formed of hollow beams that clip together. The outer frame 44 is approximately 6m long by 3m high by 2.4m wide so that it can fit inside a shipping container when assembled.

As its name implies, the separator/storage unit 42 comprises integrally formed separator 50 and storage 52 units: each is described separately in detail below. In Fig. 9, the separator unit 50 comprises a stack of parallel, vertically spaced laths 56 to which flexible tanks (not shown) attach using hooks 58 spaced 0.3m apart on each lath. The laths 56 are mounted, by connectors at each end, on a pulley and belt system 60 such that rotation of the pulleys causes the laths 56 to move up and down - making it possible to index the flexible tanks (not shown) relative to an inlet.

The flexible tanks (not shown) have a self-sealing device in a neck portion thereof so that once filled, they can be un-coupled from the inlet without egress of contaminant. The self-sealing valve may have a guide recess connected therewith, which guides the neck into correct alignment with the inlet. Sensors may be provided to use the current alignment of the tank with respect to the inlet.

The self-sealing valve may have an insert mechanism that protrudes outwards when the flexible tank to be filled has been dropped by the laths to the correct position. This could be controlled by a couple of line sensors.

The insert of the valve then expands outwards into the CRD, which locks the two units together. At the same time, flow of contaminant starts to enter the empty bag.

It could also be possible for the insert part to be in the outlet pipe of the CRD.

A micro processor may control when each of the 24 bags are lowered by the laths onto the filling and self-sealing valve. The micro-processor may be used to monitor the amount of contaminant going into each bag, and/or the volume to weight ratio.

Additionally, an oil sensor within the flexible tank may be provided so that water below the oil contaminant can be pumped from the tank back into the sea.

When oil sensor reacts to pumped contaminant, the micro-processor turns off power to the pumps and contaminant then starts to fill once again.

In Figs. 10 and 11 , it can be seen that the deck 46 of the separator comprises, at its leading edge, an inlet 62 that connects to the outlet 18 or connector tube 20 of the CRD. Thus, contaminated water flows from the CRD 10 into the separator 50 via the inlet 62. The inlet 62 has a non-return the valve 64 that prevents or inhibits backflow of contaminated water into the CRD 10. Using the pulley mechanism previously described, the flexible tanks can be indexed and sequentially connected to the inlet 62 of the separator 50.

Also shown in Figs. 10 and 11 are a pair of elongate cavities 66 formed in the underside of the deck 46 for receiving and storing the deflated buoyancy tanks 48. When the separator unit 50 is not in use, the buoyancy tanks 48 can be deflated and folded under the deck where they can be stowed in the cavities to save space and facilitate handling etc.

Turning now to Fig. 12, a schematic showing how one possible type of separator 50 might operate has an inlet 62, an outlet 66 communicating with a tank 68, Contaminated water flows in through the inlet 62 and falls onto an inclined wire grid 70. Solid matter 72 in the contaminated water hits the grid 70 and slides off into the tank 68. However, water can flow through the grid 70, flow through a conduit 74 and out of the separator 50 via the outlet 66. A second grid 76 is provided at the bottom of the tank 68 to allow surface/absorbed water to flow off the solid matter 72 in the tank 68 onto an inclined base wall 75 of the tank 68 and into the conduit 74. The grid 70 can be replaced by a filter and/or a series of gradually smaller grids so that progressively smaller solid matter 72 can be separated from the water at each stage.

Fig. 13 shows a different type of separator 50 for separating immiscible components of contaminated water, in this case, oil 76 and water 78. The separator of Fig. 13 comprises a tank 68 having an inlet 62 located at the top of the tank through which contaminated water enters. When the contaminated water is left to stand, the immiscible components thereof separate, (i.e., the oil 76 floats on top of the water 78). A valved tapping port 60 is provided at a level above the water-oil interface 82 such that the oil 76 can be removed from the tank 68 and passed via a conduit 84, into a second, storage tank 86. An outlet is provided at the bottom of the tank 68 through which the water component 78 of the contaminated water can be drained.

An exemplary scenario were the CRD could be utilised involves a chemical spillage into a river, e.g. a benzine and nitrobenzine toxic slick. A nearby, heavily populated city is dependent on the river for its water supply. Various emergency measures are implemented, e.g. putting hospitals on stand-by for possible poisoning victims, cutting off water supplies, and evacuating parts of the population. Being discharged into a river, the contaminant can impact on various countries.

Apart from putting thousands of tons of activated carbon into the rivers, few alternatives are available to reduce or remove the benzine contaminant from off the water. At the narrow points of the rivers a number of CRDs can be placed across the total width.

The surface pollutant flows over the blades of the units, and once this happened, the operator would have control of the pollutant.

The pollutant would then flow across the body of the CRDs, exit via the rear pipes to a mobile floating pump unit which directs the pollutant to land areas were it could have been stored in very quickly dug out pits, then pumped into tanker vehicles for removal to refinery for salvage.

This action could be repeated at various points along the rivers.

The units and mobile floating pumping unit, when the pollutant had passed that area, could be lifted and sent on by vehicles or train to further places down river.

In one example, the floating pumping station size could be 40ft x 8ft x 8ft. It could have ten pumps, diesel electric generator, battery's, diesel storage tank, reels of hose from ten forty feet wide recovery units at one end, reels of hose from station to other vessels, or shore at the other end, cockpit and outboard motor.

If only four pumps are required for a problem, then the other six reels of hose could be coupled to the four reels that were being used, this would give a longer distance between lifting contaminant units, or water area, to storage pits, tanks, salvage vessel, barge or scene of fire.

Besides working with the CRD system, the pumping station could be lifted by helicopter, to assist in a vessel fire at sea. Also to lift water from a lake, river, sea, canal where a fire engine may have trouble accessing, (hillside grass fire, deep mud, soft sand, no road areas).

In Fig. 14, a modified version of the CRD of Figure 1 is shown in which the underside of the CRD is provided with five tubes 88 that extend telescopically from tubular cavities 90 formed in the underside of the hull of the CRD. The tubes 88 each have a closed end 91 and series of spaced apart apertures 92 disposed along a line extending from the closed end 91 of the tube 88 towards the CRD. Thus, by delivering pressurised gas, e.g. air to an open end 93 of the tube 88, bubble jets are created at the nozzles 92. A high pressure pump 94 serves to deliver a supply of compressed air to the open end 93 of each tube 88 and by controlling the delivered air pressure and extension of the tubes 88, a desired distribution of rising bubbles can be created ahead of the CRD. As previously described, a "cloud" of rising bubbles can be used to cause submerged contaminants (e.g. blue-green algae) to rise to the water surface where they can be skimmed off by the blade of the CRD.

An optional/additional bed scarifier is shown in Fig. 15 that can be fitted to the CRD. Fig. 15 shows a bed scarifier 96 that can be used in conjunction with the CRD to decontaminate a sea bed. The scarifier 96 comprises a generally inverted dome 97 formed by a flexible sheet 105 that is held in shape using resilient stays 106 extending radially and acuately from a central boss. The stays 106 extend beyond the periphery 98 of the flexible sheet 105 and form barbed tines 107 that can be planted in the sea bed until the periphery 98 of the dome 97 abuts the sea bed 99.

The dome 97 has a vacuum port 100 therein to which a vacuum tube 101 is sealingly connected. The CRD above has a vacuum unit, e.g. a pump, which draws water from within the dome 97, up the tube 101 and into a separator or storage tank as previously described. The dome 97 has a further port 102 through which a drive shaft 103 sealingly passes. The drive shaft 103 is connected to two sets of rotating blades 104, one that rotates parallel to and the other that rotates perpendicular to the general plane of the sea bed 99. The blades 104 are arranged to dig into and disturb the sea bed 99 to cause contaminants embedded therein to rise into the dome 97 where they are drawn out via the vacuum tube for subsequent separation from the water. Dispersed oil, waves and subsurface turbulence can break floating oil into small droplets that can be driven into the water column, permanently removing oil from the surface slick.

This type of dispersion occurs naturally and can often be accelerated with the use of chemical dispersants, dispersion has a significant impact on the slick and reduces the threat to the water surface and coastal environments. However, dispersion increases the oil in the water column.

With the growing use of the heavier oils and refined products, the percentage of non-buoyant oil spills increases. Sinking/submerged oil provides response and cleanup challenges different than for surface oils.

The CRD system, with its underside telescopic pipes, may assist in raising the droplets to the surface, were it can be drawn onto the contaminant unit by the slow forward movement, or the stationary system with revolving blades drawing the contaminant on board.

The use of the underfloor suction pipes could lift the contaminated near-shore sediments pumping it through the unit to floating pumping station were the contaminated substance can be directed to other storage vessels or land fill sites for further removal to salvage depots. Commercial shell/fish farms are another potential use for the system in the removal of contamination from under the nets and sediment bottom.

A modified contaminant recovery system comprises a collector connected to a plurality of CRDs. Fig. 16 shows a distributor 110 that enables a plurality of CRDs to be connected to a common separator/storage device. A toroidal inflatable buoyancy tank 112 supports ten circumferentially spaced pumps 114 that are each arranged to draw contaminated water from a CRD that is connected to it via a flexible outlet pipe 20. The outlet of each pump 114 is sealingly connected to an aperture in a wall of a generally toroidal pipe 116. Two take-off pipes 118 are provided to convey the contaminated water from the toroidal pipe 116 to a remote separation / storage facility.

Fig. 17 shows a modified version of the distributor shown in Fig. 16. The modified distributor comprises three pumps connected, via flexible outlet pipes 20, to three CRDs 10. The CRDs 10 are able to tackle small oi! spills 120 in a confined area (e.g. a dock), whilst the oil-contaminated water is conveyed, via the distributor 110 and one of the take-off pipes 118 to a shore- based separation and storage facility 122. A theoretical scenario where the CRD may be utilised is where an oil tanker unloads at an oil refinery. A pipe from the vessel to the refinery becomes ruptured putting light crude oil onto surface of the water.

The master of the oil tanker had placed three of the ship's liquid contaminant recovery units (10) and one floating mobile pumping unit (110) which was linked up to the oil terminal's flexible pipe line (118), in the canal prior to discharging the ship's cargo. The spilt oil can be quickly lifted off the surface by the recovery units and to shore pollution tanks (122) where it can be collected by a number of road tanker vehicles and returned to the refinery for salvage.

Fig. 18 shows a further possible modification to the CRD of Fig. 1 in which a revolving brush 124 is fitted to the front of the CRD 10. The brush 124 has a plurality of blades or bristles 126 that each touch the blade 14 of the CRD as the brush revolves. Thus, flotsam and/or viscous contaminants can be swept up the blade 14 and into the passageway of the CRD, where otherwise they might not have done and/or caused a blockage. Figs 19 and 20 show a CRD in the form of a small catamaran vessel

150 having a scoop 152 fitted between the two hulls 154. When viewed from above, the catamaran's shape is generally rectangular, which facilitates storage in a container and transport by road. The hulls 154 and scoop 152 are integrally formed from upper 156 and lower 158 GRP mouldings that are sealingly joined along a seam line 160 to form a hollow body.

As per a conventional catamaran, the two hulls 154 are maintained in a parallel and spaced apart relationship to form a stable work platform. However, unlike a conventional catamaran, the scoop 152 spans the hulls 154 between their forward ends. The scoop 152 comprises a curved planar surface 162, whose leading edge 26 is positioned, in use, at a level below the waterline. In use, forward movement of the catamaran 150 causes the water's surface to be skimmed and to flow up the scoop's surface 162 over a weir 164 similar to that previously described, which impedes backflow of skimmed water back down the scoop 152.

After flowing over the weir 162, the water encounters, when viewed from above, a symmetric aerofoil shaped divider 166, which divides and concentrates the flow into two separate streams. By concentrating the water, its flow rate increases, which facilitates discharge through the discharge aperture 168 at the rear of the vessel 150. Additionally, by providing a divider 166, transverse flow of water is impeded, which might otherwise cause roll stability problems for the vessel 150. The catamaran of Figs 19 and 20 is no longer than 20 feet in length, no wider than 8 feet, and preferably has an unladen weight of less than 400kg so that it can be fitted into a 20 foot ISO shipping container. The vessel 150 is propelled forwards by a pair of outboard motors (not shown) at a speed that is sufficient to cause skimmed water to flow up the scoop 152 and over the weir 164, but not so high as to cause problems controlling the flow of water into the attached storage container (not shown). Fully laden with water, outboard motors and a crew, the displacement of the vessel is designed to be less than 1000kg.

In use, the top of the weir is located between 400 and 600 mm above the waterline and the forward movement of the vessel alone must be sufficient to raise the skimmed water to this height. This height provides clearance for the cross deck (not shown) and also allows a gentle downward slope read of the weir 164 towards the outlet aperture 168. The scoop's surface 162 could take any number of forms, e.g. short and steep of long and shallow. Computational Fluid Dynamics (CFD) modelling was used out for five different setups to test for steady flow at different speeds with the following results:

The above CFD models were carried out assuming a scoop slop of between 16 and 18 degrees. Thus, the catamaran needs to move forwards at between 7 and 8 knots to achieve a steady flow of water over the weir. This corresponds to a catamaran operating at a Froude number of 0.5 and initial calculations indicate a pair of 25 horsepower outboard motors should provide sufficient power to meet this requirement.

The invention is not limited to the details of the aforementioned embodiments, in particular, the shape and configuration of the CRD can be adapted to suit particular applications, the CRD can be self-propelled and the collection units might be capable of being jettisoned for later collection.

A foam screen filter could be placed downstream of the weir for the water/oil mix to flow over: the denser water component of oil/water mix could flow down through the filter, but not the less dense oil component. The CRD could be manufactured from GRP laminate, plywood or aluminium for lightness and strength.

Claims

1. A contaminant recovery device (CRD) for recovery of floating contaminants, comprising a housing, a passageway extending through the housing between an inlet at one end and an outlet at an opposite end, a liquid guide surface at the inlet and means for positioning the liquid guide surface in or under the layer of contaminant, whereby forward motion of the device in the water causes said contaminant to flow or pass over the liquid guide surface into the passageway.

2. A CRD as claimed in claim 1 , further comprising one or more storage containers releasably connectable to the outlet of the CRD.

3. CRD as claimed in claim 1 or claim 2, further comprising a contaminant separation unit.

4. A CRD as claimed in any preceding claim, wherein the liquid guide surface is formed by the inlet of the device.

5. A CRD as claimed in any preceding claim, wherein the liquid guide surface is movable relative to the housing.

6. A CRD as claimed in claim 5, wherein the CRD comprises one or more selectively fillable or emptyable ballast or buoyancy tanks.

7. A CRD as claimed in any preceding claim, wherein the liquid guide surface comprises a plate having one or more upright blades thereon.

8. A contaminant recovery system for recovery of contaminants in water, comprising a movable contaminant recovery device (CRD) adapted recover the contaminants by skimming the surface of the water as it moves across it, the contaminant recovery device comprising a passageway for directing the collected contaminants and water towards an outlet, a collector unit connected to and arranged to receive the contaminants from the outlet, the collector unit being further arranged to separate the at least some of the water from the contaminants, and a storage unit into which the contaminants and/or water are dischargeable.

9. A CRD or system as claimed in any preceding claim, wherein, at least part of the CRD below the inlet is streamlined.

10. A CRD or system as claimed in any preceding claim, wherein the CRD comprises attachment means adapted to attach to one or more powered watercraft or an on-board propulsion unit.

11. A CRD or system as claimed in any preceding claim, wherein the contaminant recovery device further comprises a raising means for raising submerged contaminants to or towards the surface of the water.

12. A CRD or system as claimed in claim 11 , wherein the raising means comprises one or more jets, positionable in front of and/or below the liquid guide surface, connectable to a gas supply.

13. A CRD or system as claimed in any of claims 8 to 12, wherein the collector unit comprises a towable floating platform that can be towed behind the CRD.

14. A CRD or system as claimed in any of claims 8 to 13, wherein the separator comprises any one or more of a sieve, a micro-filter system, a chemical separator, a biological separator, a cyclonic separator and a settling tank.

15. A CRD or system as claimed in claim 14, wherein the separator is a multi-stage separator.

16. A CRD or system as claimed in any of claims 8 to 15, wherein the separator unit comprises a towable floating platform.

17. A contaminant recovery system as claimed in any of claims 8 to 16, comprising two or more CRDs connectable via connecting tubes to a central separator/storage unit.

18. A CRD or system as claimed in any preceding claim, wherein the CRD further comprise a sweeping means associated with the liquid guide surface for sweeping the contaminants into the CRD.

19. A CRD or system as claimed in claim 18, wherein the sweeping means comprises a rotatable drum having blades and/or bristles thereon mounted above and/or in front of the liquid guide surface.

20. A CRD or system substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.