A system and method for collecting and processing BIO-waste from aquaculture enclosures

Abstract

The present invention relates to a system and method for collecting and processing bio-waste from aquaculture enclosures The system includes a collection unit with a bio-waste pot (4) positioned below the enclosure, a suction line (6) extending into the pot, and a suction pump (9) connected to a transfer line (8) leading to a processing facility. A sequence control system operates the suction pump and valves to minimize water transfer. The system features sensors to distinguish between clean water and bio-waste, and includes dump lines (17, 22) for water return. The method involves capturing bio-waste, transporting it via the suction line, and directing it to the processing facility when bio-waste is detected. Freshwater may be used for flushing, and the process includes dewatering, separating feed from faeces, and hygienizing the feed for reuse.

Description

A SYSTEM AND METHOD FOR COLLECTING AND PROCESSING BIO-WASTE FROM AQUACULTURE ENCLOSURESTechnical Field

[0001] The present invention relates to collection of waste, also called sludge, from aquaculture pens, ponds, net enclosures, cages or tanks, in particular for farmed fish, and handling of the sludge in a way that facilitates the use of the sludge as a resource.Background Art

[0002] The aquaculture industry, particularly fish farming, faces significant challenges in managing waste, specifically uneaten feed and fish faeces, which settle at the bottom of the sea or lake and impact the environment. This waste, commonly referred to as sludge, has garnered considerable interest for its potential to be processed into valuable resources within a circular bioeconomy, rather than being a source of pollution.

[0003] In land-based aquaculture facilities, water from fish tanks is pumped to a sludge treatment plant where it is cleaned before being discharged or recirculated. The cleaning process adheres to the discharge permits specific to each facility. The high water flow through the tanks relative to the amount of sludge necessitates multiple treatment steps to achieve a sufficiently high total solids (TS) content for storage or further drying to around 90% TS, making the sludge commercially viable for long-term storage.

[0004] Existing sea-based facilities for sludge collection from fish cages handle sludge by pumping it along with large volumes of water, using similar processing equipment as land-based facilities to increase the TS content. However, no current systems effectively collect and process sludge from sea-based fish cages. These systems often attempt to combine the collection of dead fish and sludge, resulting in large volumes of water and foreign matter, posing challenges for efficient sludge processing. Known systems have limited efficiency (2-3% collection rate) and face issues with hydrogen sulphide (H2S) production and operational reliability. Additionally, the high salt content in processed sludge from seawater presents a costly challenge to reduce to acceptable levels for commercial use.

[0005] A general challenge is that fish faeces and uneaten feed are treated as sludge and processed accordingly, i.e. , pumped with large volumes of water and thickened and dewatered using principles similar to those in sewage and sludge treatment plants. This relatively harsh treatment breaks down the original particle structure of both fish faeces and feed, converting it into sludge that must then be processed. The large volumes of water relative to the TS content make thickening and drying cumbersome, involving large machinery and high energy consumption.

[0006] There have been several attempts to collect waste from fish pens, ponds and net enclosures. Below is a review of concrete relevant prior art solutions.

[0007] NO172322B describes a method and apparatus for collecting particulate feed residues that sink below fish cages in aquaculture facilities. The system positions a collection device around and under the bottom of the fish cage, which directs the sinking feed residues to a collection part and a bottom outlet. The residues are then transported to the surface for processing. The collection device is made of net material with a mesh size that allows only particles above a certain size to be collected, while smaller particles and fish excrement are washed out. This system is similar to the new invention in that it aims to collect and process particulate waste from fish cages. However, it does not address the separation of feed from faeces or the use of freshwater to reduce salt content in the processed waste.

[0008] NO329813B1 describes a device for collecting dead fish and other waste from the bottom of a fish cage. The system includes a funnel-shaped collection head, and a hose connected to an airlift pump that transports the waste to the surface. The device also features a flexible sleeve that prevents small fish from being sucked into the system. While this system effectively removes dead fish and large particles, it does not focus on the separation of different types of waste or the reduction of water usage in the process. There is a need to improve upon this method by reducing water usage and facilitate separation of feed from faeces.

[0009] NO332235B1 details a pump system for removing solid particles from the bottom of a fish cage. The system includes a hose with buoyancy elements to keep it upright and a pump that creates a suction effect to lift the waste. The system is designed to handle large volumes of water and waste, which means that the sludge will have a high water content.

[0010] NO332341 B1 describes a fish cage system with a closed cage and a water intake system that pumps freshwater into the cage. The system includes a collection device for dead fish and waste, which is then transported to a processing unit. The focus is on maintaining water quality and reducing environmental impact. While it shares the goal of improving waste management in fish cages, it is not concerned with a subsequent separation of feed and faeces from water or the use or reuse of the sludge.

[0011] NO335174B1 describes a waste collection system for aquaculture cages that uses an airlift pump to remove dead fish and other waste. The system includes a collection head and a hose that transports the waste to the surface. The system is designed to handle large volumes of water and waste. However, it does not focus on the separation of sludge and water, separation of different types of waste or the reduction of water usage in the process.

[0012] NO342583B1 describes a system for collecting and removing waste from a fish cage, including a collection head and a pump system. The system is designed to handle large volumes of water and waste. However, it does not address the separation sludge and water or separation of feed and faeces.

[0013] NO342765B1 describes a system for removing waste from the bottom of a fish cage using a waste pipe and an airlift pump. The system includes protective elements to prevent the pipe from damaging the cage net. While it effectively removes waste, it does not focus on the separation of different types of waste or the reduction of water usage in the process.

[0014] NO343583B1 describes a system for collecting and removing waste from a fish cage, including a collection head and a pump system. The system is designed to handle large volumes of water and waste. However, it does not address the separation of sludge from water or separation of feed and faeces.

[0015] NO343692B1 describes a system for collecting and removing waste from a fish cage, including a collection head and a pump system. The system is designed to handle large volumes of water and waste. However, it does not address the separation of sludge and water, or separation of feed and faeces.

[0016] NO344657B1 describes a system for collecting and removing waste from a fish cage, including a collection head and a pump system. The system is designed to handle large volumes of water and waste. However, it does not address the separation of sludge and water, or separation of feed and faeces.

[0017] GB2242140A discloses a tank-based arrangement in which part of the water exits through a mesh sleeve to a central overflow, while particulate-laden water is drawn through a peripheral slot or annular “suction means” arranged around the central outlet and fed into an annular chamber with a tangential duct that establishes a vortex. Discharge of the collected slurry is performed periodically by opening a valve to a foul drain, and an opening is provided for anti-siphoning and visual observation of the sequence: initially clean water from duct, then dirty water, then clean water again. No pump is disclosed; the flows are clearly driven by gravity / head, and the “suction means” are exemplified as orifices rather than pumps. The system’s reliance on gravity makes it ill-suited to open sea cages. Although onward treatment of particles is mentioned, there is no teaching of separating uneaten pellets from feces; in practice, pellets would likely dissolve before discharge.

[0018] CN116649266A schematically shows multiple pens, each with a bottom collection unit connected by pipes to a pump and a sedimentation tank. The controller operates solenoid valves to periodically suck up sludge. A sensor detects a sludge level in the collection unit, but there is no sensor for detecting when clean water starts arriving; timing-based control is implied. There is no disclosure of distinguishing or preserving feed pellets versus feces; the text only generally states that collected material can be converted to feed or fertilizer.

[0019] US5636595A shows a detailed particle-trap / collection unit with an annular chamber and slot around a central outlet, including arrangements for taking relatively clean water via perforations and discharging particle-rich water via a separate outlet. It does not disclose using valves and pumps to empty the collection unit.

[0020] WO2021225450A1 discloses an outlet basin for closed or semi-closed pens, with separate systems for main water outlet, sludge removal via a circumferential channel covered by a mesh, and dead-fish handling. Sludge and dead fish are handled on separate paths and can be pumped out independently.

[0021] NO339302B1 concerns an air-lift based waste collection system that injects air at or near the suction head / conduit to raise a water-waste mixture, and provides an air evacuation device to prevent stagnant air pockets. A pump may assist lifting on an ascending section to a receiving station. There is no disclosure directed to preserving uneaten pellets or separating pellets from sludge.

[0022] The prior art systems for waste collection in fish cages have several limitations that the new invention aims to solve:

[0023] High Water Usage: Many existing systems use large volumes of water to transport waste, making the process inefficient and costly, and not least, results in a substantial water content in the sludge that is brought to the surface. This creates great challenges in the separation of solids from the water.

[0024] Lack of Separation: Current systems do not effectively separate feed from faeces, which complicates further processing and reduces the potential for recycling feed.

[0025] Salt Content: The use of seawater in the waste collection process results in a high salt content in the processed waste, making it less suitable for applications like biogas production or as fertilizer.

[0026] Handling of Dead Fish: Combining the collection of dead fish with waste particles leads to large volumes of mixed waste, complicating the processing and increasing the risk of system blockages.

[0027] Energy Consumption: The need for large pumps and extensive water treatment processes results in high energy consumption and operational costs.

[0028] In the context of waste management in aquaculture, particularly in fish farming, the method of lifting waste material from the waste collector to the surface is crucial. Traditional methods often employ air or sea water for this purpose. However, these methods present several drawbacks. In particular salt content in the waste poses a great problem for reuse or deposition. As the prior art solutions uses air or sea water to lift the waste, the resulting waste material retains a high salt content.This is problematic for several reasons:

[0029] Environmental Impact: High salt content in waste can lead to increased salinity in the disposal area, adversely affecting local ecosystems.

[0030] Processing Challenges: High salinity complicates the processing of waste for biogas production or as fertilizer. The presence of salt can inhibit microbial activity necessary for biogas production and can also lead to soil salinization if used as fertilizer.

[0031] Corrosion and Maintenance: The high salt content due to the significant mixing in of sea water, makes the waste material inherently corrosive, which can lead to accelerated wear and tear of the equipment used for both for pumping and transporting waste, as well for the subsequent handling. This increases maintenance costs and reduces the lifespan of the equipment.

[0032] Efficiency of Waste Separation: The efficiency of separating solid waste from water is lower when air or sea water is used to lift the waste from the pen.

[0033] Environmental Regulations: Disposing of waste with high salt content can lead to regulatory challenges, as many regions have strict guidelines on the salinity levels of discharged waste.Summary of invention

[0034] The present invention has as an object to resolve or reduce one or more of the above problems.

[0035] In first aspect the invention provides a sequence control of the process to maximize the ratio of bio-waste to water when the bio-waste arrives at the processing facility. This is conveniently achieved by controlling valves and pumps in the lines from the bio-waste pot to the processing facility to ensure that the lines upstream of the processing facility are filled with a liquid having a high particle concentration, and routing liquid having a low particle concentration out of the lines before reaching the processing facility.

[0036] In a second aspect the present invention suggests the use of seawater or alternatively freshwater as flush water at an early stage in the process to aid the lifting of the bio-waste from the bio-pot and into the suction line. Freshwater may be used as flush water instead of seawater to reduce the salt content in the processedwaste. The flush water may be introduced into the bio-waste pot, such as through the bottom of the pot or into the suction line between the pot and the suction pump. If freshwater is used, the reduction in salinity makes the waste more suitable for further processing and environmentally friendly disposal. A lower salt content makes the waste less corrosive, thereby extending the life of the equipment and reducing maintenance costs. The lower salt content facilitates better separation of solid waste from water, enhancing the overall efficiency of the waste management process, and it helps in meeting environmental regulations more.

[0037] In a third aspect the present invention provides positive displacement pumps to control the entire process, which minimize the water usage, power consumption and ensure efficient transport of waste.

[0038] In a fourth aspect the present invention provides sequential control to optimize the collection and processing of waste, reducing the need for continuous operation and lowering energy consumption, as well as further reducing the mixing in of water in the bio-waste.In a fifth aspect of the invention, it includes methods for dewatering, separating feed from faeces, and hygienizing the feed for potential reuse, providing significant operational and economic benefits.Detailed description of the invention

[0039] The invention will now be described, referring to specific embodiments, some of which are shown in the accompanying figures. These embodiments are exemplary and should not be construed to limit the protective scope of the claims.

[0040] Figure 1 shows schematically a system according to the invention,

[0041] Figure 2a shows the arrangement of lines in a first alternative,

[0042] Figure 2b shows the arrangement of lines in a second alternative,

[0043] Figures 3a-3h illustrate the operation in sequence:

[0044] Figure 3a illustrates the initial situation before any waste has been collected,

[0045] Figure 3b illustrates that waste has been collected in the bio-waste pot,

[0046] Figure 3c illustrates waste having been sucked into the suction line,

[0047] Figure 3d illustrates more waste collected in the bio-waste pot,

[0048] Figure 3e illustrates waste having reached the suction pump,

[0049] Figure 3f illustrates partial emptying of the suction line due to stuck suction line,

[0050] Figure 3g illustrates waste being directed to the processing facility,

[0051] Figure 3h illustrates a suction line and transfer line full of bio-waste, and

[0052] Figure 4 illustrate schematically an example of a system according to the invention that is coupled to a plurality of pens.

[0053] The present invention stipulates to treat the particulate material that hitherto has been termed “sludge” as biological material comprising particles and pellets ranging from approximately 1 to 30 mm, as they are when they leave the fish cage and sink towards the seabed. This material will therefore be termed "bio-waste" in the following description. It only becomes sludge when the particles break down or dissolve due to mechanical impact or over time. Based on this understanding, the inventors have developed a concept for collecting and processing bio-waste. The concept includes a novel bio-capture pot, a sequence control system to minimize water usage in the handling process, and a particle processing method to dewater bio-waste, preferably separate feed from faeces, and hygienize the feed for reuse in an energy- and cost-efficient manner.

[0054] According to the invention the bio-waste is handled gently to maintain its particle / pellet structure until it is no longer practical. The bio-waste is handled separately from dead fish.

[0055] The handling involves as little seawater as possible. Seawater can largely be replaced with freshwater early in the process to reduce the cost of achieving a satisfactorily low salt content in the processed end product without significant additional costs.Detailed description of the figures

[0056] Figure 1 shows the overall concept of the present invention, which treats particulate material, previously termed "sludge," as biological material comprising particles and pellets ranging from approximately 1 to 30 mm.

[0057] A fish pen 1 is partially illustrated in figures 2a and 2b. The fish pen 1 has a bottom 2. Below the bottom is a collection unit 3 attached to the pen 1 . The collection unit 3 may comprise a fine mesh or a water tight sheet. A bio-waste pot 4 is attached to a lower edge 5 of the collection unit 3. The collection unit 3 may be of an already existing type. The collection unit and the bio-waste pot may also be a single unit.

[0058] Figure 1 shows the lower part of the collection unit 3 and the bio-waste pot in further detail. The bio-waste pot has an upper conical portion 4a which transitions to a lower substantially cylindrical portion 4b. The bottom of the substantially cylindrical portion is rounded.

[0059] The bio-waste pot 4 may also be of conical shape all the way into the rounded bottom. The bottom may also be flat.

[0060] A suction line 6 extends into the lower portion of the bio-waste pot 4. The outer part, closest to the bottom of the bio-waste pot 4 of the suction line 6 may be a rigid pipe 6a and the part of the suction line 6 extending to the surface may be a flexible hose 6b. In the following the whole suction line 6 may sometimes be called suction hose. It should be understood that the suction line 6 may be a hose all along its length and may comprise a rigid pipe at its lower end.

[0061] Figure 1 is schematic, and the remaining component illustrated are illustrated as single lines although it should be understood that they are flow lines.

[0062] The suction line 6 is coupled to a transfer line 8 through a first valve 7. A suction pump 9 is arranged in the transfer line 8. The suction line 6 is coupled to the transfer line 8 upstream of the suction pump.

[0063] The transfer line 8 is at its upstream end coupled to a reservoir (not shown) of freshwater or seawater. Downstream of the suction pump 9, the transfer line 8 extends to a processing facility.

[0064] The transfer line 8 has a second valve 10 upstream of where the suction line 6 meets the transfer line 8 and a third valve 11 downstream of the suction pump 9.

[0065] A flush pump 12 is coupled to the transfer line 8 upstream of the second valve 10 through a flush line 13. Downstream of the flush pump 12 the flush line 13 extends to the bottom of the bio-waste pot 4. It may be coupled to the bio-waste pot 4 through a rigid connecting piece (not shown). A fourth valve 14 is arranged in the flush line 13 upstream of the flush pump 12.

[0066] A first branch line 15 is coupled to the flush line downstream of the flush pump 12 and upstream of the fourth valve 14. The first branch line 15 has a fifth valve 16. The branch line 15 extends to the suction line 6 upstream of the first valve 7 and downstream of the distal end of the suction line 6.

[0067] A second branch line 17 is coupled to the transfer line 8 downstream of the suction pump 9 and upstream of the third valve 11. This second branch line 17 can also be termed dump line or return line, as its distal end is within the fish pen 1 . The dump line 17 has a sixth valve 18.

[0068] As shown in figure 2a, the flush line 13 can extend into the inside of collection unit 3, exit through a passage 19 in the bio-waste pot 4 and be coupled to the bottom of the bio-waste pot 4. The figure also shows that the suction line 6 extends on the inside of the collection unit 3.

[0069] As shown in figure 2b, the flush line 13 may also extend along the outside of the collection unit 3 and be attached to this. The suction line 6 may also extend on the outside of the collection unit 3 and through a passage 20 to the inside.

[0070] The functioning of the system will now be described referring to figures 3a- 3h.

[0071] When fish is introduced into an empty pen, the bio-waste pot is empty of any bio-waste, as shown in figure 3a. It will only contain water. The suction line 6 is either filled with water or air. As bio-waste collects in the pot 4, the level of bio-waste will rise, as shown by the shaded area denoted by reference number 21. When the level has risen to a certain level, the suction pump 9 will start operating, initiated by a signal from a sensor in the pot 4 and / or based on experience data on production of bio-waste for the relevant pen. This experience data may be calculated by the control system based on the number and size of fish as well as feeding amount.

[0072] The first valve (not shown in figures 3a-3h) is open, and the suction pump 9 will suck bio-waste into the suction line 6 as shown by 21 in figure 3c. Water will also be sucked into the suction line 6, as shown by reference number 22. The sixth valve 18 is open and the third valve 11 is closed during this phase, so that water is expelled through the dump line 17. A sensor that can distinguish between relatively clean water and water containing a substantial among of bio-waste, such as a turbidity sensor, optical particle counter, laser diffraction sensor, acoustic doppler velocimeter, ultrasonic sensor, conductivity sensor, capacitive sensor, nephelometer, fibre optic sensor or an imaging system, is arranged at a suitable location in the suction line 6, in the transfer line 8, such as downstream of the suction pump 9, inside the suction pump 9, or in the dump line 17. As long as the flow of water through the suction line 6 is relatively free from particles, the water is diverted to the dump line 17.

[0073] When the level sensor in the bio-waste pot 4 detects that the pot is empty from bio-waste, the suction pump 9 is stopped. The bio-waste is now situated in the lower part of the suction line 6, as shown in figure 3c. The suction line 6 may have a non-return valve (not shown) that prevents the bio-waste from falling back into the pot 4.

[0074] As time progresses, the pot 4 will again fill with bio-waste, as shown in figure 3d. When the level again has reached a certain level, the suction pump is again started, relatively clean water is expelled through the dump line 17 and when the pot is empty, the pump is again stopped, as shown in figure 3e. After a few of these cycles, the bio-waste will reach the suction pump 9, as shown in figure 3e.

[0075] Unless the friction-loss in the suction line 6 exceeds a critical level for the transfer pump 9, typically caused by a long suction line, sticky bio-waste or long retention time, the pump will continue to empty the pot and the suction line, as described below.

[0076] In some instances, the friction loss in the suction line 6 will be too large for the suction pump 9 to be able to pump the bio-waste. This situation is shown in figure 3f. it will then have to be emptied. Then the flush pump 12 may pump water into the suction line 6 through the first branch line 15. These components are omitted infigure 3f. The bio-waste will then exit back again to the pot 4. During this phase the optional non-return valve in the suction line 6 will be held open.

[0077] Provided that the bio-waste 21 does not become stuck in the suction line 6, the presence of particles in the vicinity of the suction pump 9 will initiate a closing of the sixth valve 18 and opening of the third valve 11 , so that the bio-waste 21 is directed to the processing facility, as shown in figures 3g and 3h.

[0078] In the figures 3a-3h are also shown a second dump line 22. This line is arranged close to the processing facility and its purpose is to dump relatively clean water that is in the transfer line 8 between the dump or return line 17 that directs water back to the same pen as the bio-waste 21 has originated and the processing facility. This amount of water can be substantial if the transfer line is long. A sensor, such as a turbidity sensor may be arranged in the vicinity of the connection point of this dump line 22 to the transfer line 8. This phase is illustrated in figure 3g.

[0079] When the transfer line 8 is substantially empty of relatively clean water, the transfer line is opened to communicate with the processing facility, and the bio-waste flows to the processing facility, as illustrated in figure 3h.

[0080] Figure 4 shows a schematic example of a system that is coupled to serve a plurality of fish pens. One pen 1 is illustrated, while for the other pens only the suction lines, flush lines and dump lines are shown.

[0081] The suction pump 9 is common for all pens, but, in particular for larger fish farms, a plurality of pumps may be used. The pump will conveniently be placed as close to the enclosures as practically possible, such as on the edge of the pen. All suction lines 6 are coupled to this pump 9 through respective valves 7 and the transfer line 8. Only one of these valves 7 will be open at a given time. A stand-by pump 9a is also shown. This pump 9a will be used if the suction pump 7 fails, has to be maintained or if there is a need for greater pumping capacity. Valves 23, 24, 25, 26 determines which of the pumps 9, 9a are active.

[0082] A plurality of dump lines 17 are coupled to the transfer line 8, one for each pen. It is preferred to let the water flow back to the pen from whence it originated in order to minimize the risk of transferring diseases.

[0083] A flush pump 12 is also shown. This can be coupled to a respective one of the flush lines 13, one for each pen. It may pump freshwater through a freshwater line 27 or alternatively seawater through a seawater line 28. A filter 29 may be included in either of these lines.

[0084] As shown by the branch line or cross-flow line 15, the flush pump 12 can also pump water into the transfer line 8 to flush the suction lines 7 if necessary.

[0085] The transfer line is selectively coupled to the seawater line 28 through a cross-flow line 30 to supply water when it is necessary to fill the transfer line with clean water.

[0086] Figure 4 shows valves that have not been described in the above. However, the purpose of these valves will be obvious to the person of skill in the art based on the explanations above and the common general knowledge.

[0087] When the suction of the bio-waste from the pot 4 is performed, freshwater will preferably at the same time be flushed into the pot 4 from the underside. This will lift the bio-waste from the pot and dilute the salty seawater surrounding the bio-waste before the bio-waste is sucked into the suction line 6.

[0088] The bio-waste material is collected and processed using a novel bio-capture pot, a sequence control system to minimize water usage, and a particle processing method to dewater bio-waste, separate feed from faeces, and hygienize the feed for reuse. The bio-waste is handled gently to maintain its particle / pellet structure until it is no longer practical. The bio-waste is handled separately from dead fish, and the process involves as little seawater as possible, with seawater being replaced with freshwater early in the process to reduce the cost of achieving a satisfactorily low salt content in the processed end product.

[0089] Bio-waste, as the first step in dewatering, will be transported to a filter belt (not shown). Dewatering can be enhanced by blowing air on the particles and the filter belt. The bio-waste, which now consists of more particles than liquid, can be filled directly into big bags or containers for storage and transport. Bio-waste that follows with excess water out from the filter belt, and is not captured by the filter belt, can be dumped or filtered and thickened in the traditional way, if required.

[0090] Separating feed from faeces can be done using a vibrating screen or filter belt.

[0091] Additional advantages and properties of the above are that small volumes are handled, which results in minimal energy consumption. The pellet structure of the bio-waste (typical size of 1 -10 mm) allows for rapid and efficient sedimentation / thickening in a sedimentation tank, if desired. The pellet structure also facilitates easy reduction of salt content in the final product when seawater is replaced with freshwater early in the process. The differences in properties between faecal pellets and feed pellets allow for the separation of feed and faeces and their processing in separate facilities. When feed and faeces are separated, the feed can be efficiently washed and disinfected for reuse.

[0092] High TS content in the bio-waste entering the processing plant requires smaller tanks and simpler equipment for dewatering to increase TS content for transport and further processing and drying. High TS content in the bio-waste makes the addition of chemicals like an oxidant, such as Nutriox or similar, early in the process, to prevent decay and H2S formation, more cost-effective.

[0093] The principles of the present invention thus provide highly efficient bio-waste collection and processing with low investment and operating costs, offering a short path to a commercially profitable investment.

[0094] A fine-meshed conical net or other device is mounted under the cage proper holding the fish so that the bio-waste that passes through the bottom of the net of the cage is captured in the collection net / device. It is assumed that the collection of dead fish takes place inside the cage at a higher level than the collection of the bio-waste. The bio-waste will sink to the bottom of the collection net / device after a short time. The diameter can be as large as the diameter of the cage so that most of the biowaste is captured, but if the net has a bottom that is impervious to particles and guides the particles towards a centre opening of the bottom, the device may cover only the area below the opening. The collection net / device must be designed so that the bio-waste can fall into a bio-capture pot.

[0095] The bio-capture pot is arranged at the bottom of the collection net / device, and as time passes, this bio-capture pot will eventually fill up with bio-waste. The biocapture pot has an outlet connected to a suction hose that goes directly to a pumpstation. The dimension of the suction hose is adapted to the maximum size of the fish feed used, so the hose will typically have an internal diameter ranging from 50 to 75 mm. This will ensure that feed pellets do not get stuck in the suction hose and block this. The bio-capture pot is designed to be self-cleaning and without pockets where bio-waste can accumulate and remain. The pot has a gentle transition to the suction hose to reduce the risk of clogging and is equipped with sensors to measure the level of bio-waste in the pot.

[0096] The pump station can be surface mounted to provide a simple, inexpensive, and reliable construction with easy access for maintenance. However, it is also conceivable to have the pump station submerged, such as suspended in a line for easy retrieval. The station is designed to suck up the bio-waste with minimal use of seawater, but still using enough water to prevent the hose from clogging.

[0097] Any excess water that does not contain a significant particle content, may automatically be returned to the same cage it is sucked from to avoid contamination between cages.

[0098] The pump station is placed close to the cages to provide the shortest possible suction hose. It may therefore be delivered as a sealed module in several different versions, where at least one version may be placed on the cage's upper structure or mounted on a fleet that lies close to the cages. The pump station may be equipped with a flushing pump, a transfer pump, and a stand-by pump. The latter can be activated if one of the other pumps fail.

[0099] The flushing pump can be used to flush the bio-capture pot or suction hose and to provide treatment chemicals if desired. Transfer of bio-waste from the pump station to the processing facility can be done under high pressure if the distance between the pump station and the processing facility necessitates this. The ratio of water to particles will conveniently be about 60% particles and 40% water so that the mass can go directly to dewatering without further filtering / processing.

[0100] The processing facility can be made simple and compact and may come as an option pre-assembled in a standard container ready for use. The main purpose of the processing is to dewater the bio-waste sufficiently so that it can be filled into big bags or pumped to a storage tank for further transport or processing. Dewatering may be done by a belt filter, such as a wire mesh, felt or similar, as the first step. Thismay be done without the use of polymers as the particles in the bio-waste are relatively large and the amount of water is low.

[0101] In the next step Nutriox or a similar chemical is added to temporarily stop decay and the production of H2S. Separation of feed and faeces may be done as far as the feed pellets have not completely disintegrated. Sanitization of the separated feed may occur immediately after dewatering. The faeces will then be transferred to a sedimentation tank to provide the most favourable conditions for further dewatering by belt filter, centrifuge, or screw press. If desired, polymers can be mixed in for more efficient recovery of the finest particles. The processed bio-waste will then have a dry matter content and consistency that makes it suitable for filling into big bags for further transport. The processing facility is compact and can be placed on a feed barge, on a separate barge, or preferably on land if the distance to the cages is not too great.

[0102] The entire process is conveniently controlled using a PLC with a data link to communicate with the facility's other control systems. The man-machine interface is screen-based, with the possibility of monitoring via a mobile phone or tablet. The capacity for suctioning bio-waste is automatically controlled by measuring the operating conditions of the pump station, sensing the level of bio-waste in the biocapture pot, and measuring the turbidity of the bio-waste entering the pump station. There will always be several parameters that are compared to provide the best possible result and give alert if unforeseen events occur. Valves and pumps are controlled so that excess water is directed back to the cage or sea, ensuring that only concentrated bio-waste is transferred to the processing facility.

[0103] The invention consists of a bio-capture pot that, in conjunction with a transfer pump and a flushing pump, makes it possible to collect bio-waste (fish faeces and excess feed) from an aquaculture cage so gently that the pellet structure of the biowaste is retained while the seawater that normally surrounds the bio-waste can be replaced with freshwater. In connection with the bio-capture pot, a sequence control has been invented that controls pumps and valves so that water consumption is minimal and excess water is recirculated from the same cage it is taken from (to avoid contamination between cages). The invention also includes a method for particle processing of bio-waste and cleaning the feed so that it can be reused.

[0104] The bio-capture pot is a unit that fits onto a collection unit, which typically can be a conical collection net under a cage or any other device for collecting bio-waste under a sea-based aquaculture cage or tank. The bio-capture pot can be connected to the collection unit either from the outside or inside. It typically has a funnel-shaped inlet that extends down to a bottom chamber where an outlet pipe with a suction nozzle is arranged to suck up the bio waste without blockage or residues of biowaste accumulating and remaining. The outlet pipe is coupled to a suction hose and the hose is in turn coupled to a suction and transfer pump.

[0105] The suction nozzle can be equipped with a check valve if necessary. The biocapture pot is further provided with a flushing hose. The bottom chamber is connected to the flushing hose for the supply of freshwater or seawater from a flushing pump.

[0106] Instrumentation with sensors is installed to measure the level of bio-waste in the bio-capture pot. A turbidity meter is conveniently provided to distinguish between water and bio-waste handled by the transfer pump. The transfer pump is typically a standard positive displacement pump suitable for handling pellets gently and can be controlled to measure and regulate both capacity (l / min) and volume (litres) pumped. The flushing pump may be of the same type as the transfer pump so that it can be used as a reserve or back-up.

[0107] The functions of the bio-capture pot are controlled using a PLC with sequence control in close interaction with the transfer pump and flushing pump. The flushing pump is controlled to flush pipelines with clean water under high pressure if necessary and to dose in flushing water where and when necessary, to ensure good process and pump functions. Freshwater can be used as flushing water, thereby displacing the seawater in the piping and pumps with freshwater to minimize the salt content in the finished product. By controlling the amount or volume pumped by the flushing pump, water consumption is minimal.

[0108] The flushing pump, through its connection to the bottom chamber, provides the possibility of flushing water into the bottom chamber and lift the sedimented biowaste at regular intervals, preventing bridging and re-clogging of the bio-capture pot. By dosing freshwater instead of seawater into the bottom chamber, the seawater in the sedimented bio-waste in the bio-capture pot will be replaced with freshwater toreduce the salt content in further handling and processing. The use of freshwater will also increase the efficiency of using polymers in the later processing steps. If necessary, chemicals can be added to the flushing water to prevent decay and the formation of H2S. Sufficient flushing water is dosed in when the transfer pump sucks the bio-waste out of the bio-capture pot to ensure that the suction hose is filled with flushing water. The flushing water may also be seawater, such as if freshwater is not readily available. The ratio of water to bio-waste is such that the bio-waste can be pumped without problems.

[0109] The primary function of the transfer pump is to suck up bio-waste from the bottom chamber and transport it to the processing facility. When the bio-capture pot is sufficiently filled, the transfer pump starts and sucks the pellets into the suction hose until the bio-capture pot is empty. Water in the suction hose that does not contain pellets is directed back to the sea (preferably to the same cage it is sucked from) until concentrated bio-waste arrives. This reduces the water content in the biowaste pumped to the processing facility. In cases where the length of the suction hose allows for multiple emptying of the bio-capture pot, it may take several emptying sequences before the suction hose is sufficiently filled with bio-waste. When the suction hose and transfer pump are sufficiently filled with bio-waste, the bio-waste is directed to the processing facility. If the suction hose becomes clogged due to a high content of bio-sludge, flushing water can be directed into the suction hose to clean the suction hose.

[0110] A control sequence has been developed that, utilizing the bio-capture pot and associated pumps and valves, can transport bio-waste in its near-original structure and with minimal water content to the processing facility. This makes it possible to separate the feed from the rest of the bio-waste, so that feed and faeces can be processed separately. The feed can be treated for reuse as fish feed or feed for other animals, where desired. The control sequence also makes it possible to measure the amount of bio-waste from each cage and provide a measure of overfeeding. The control sequence includes a monitoring sequence for all bio-capture pots and pump stations, a suction sequence for each bio-capture pot, a transfer sequence to the processing facility, and a quantity control sequence.

[0111] The monitoring sequence involves monitoring of bio-capture pots and transfer lines. The need for emptying is coordinated between the individual cages so that transfer to the processing facility is synchronized as much as possible to reduce starts or stops in the transfer. In cases where it is desirable to separate feed from faeces or measure overfeeding, the suction sequence can be coordinated with the feeding period for the individual cage so that the bio-capture pot is emptied, especially during the feeding period, to facilitate separation. Addition of flushing water in the transfer line to avoid blockage of the line due to high dry matter content is done as needed. The addition of flushing water is controlled by adding flushing water to the suction hose for each cage. Monitoring of bio-waste content in the water transferred to the processing facility and dumping of water that does not contain bio-waste.

[0112] Monitoring of multiple pump stations and transfer to the processing facility will be controlled so that transfer occurs continuously with overlap from one station to the next to avoid stopping the transfer and reducing the need for flushing water.

[0113] Start of the suction sequence is controlled by one or more of the following parameters: Level of bio-waste in the bio-capture pot, operating conditions of the transfer pump, communication with the feeding system, and experienced production of bio-waste per time unit in each cage.

[0114] A favourable amount of collected bio-waste is emptied per suction sequence through the following sequence: The transfer pump starts and sucks the pellets into the suction hose until the bio-capture pot is empty. Water in the suction hose and transfer pump that does not contain pellets is directed back to the sea (to the same cage it is sucked from if desired) until concentrated bio-waste arrives. When concentrated bio-waste arrives at the transfer pump, it is directed to the processing facility. In cases where the length of the suction hose allows for multiple emptying of the bio-capture pot, it will take several emptying sequences before the suction hose is sufficiently filled with bio-waste. The transfer pump's power consumption and suction pressure will determine when the suction hose is sufficiently filled with biowaste and can be transferred to the processing facility. If the suction hose becomes clogged due to a high content of bio-sludge, flushing water can be directed to clean the suction hose and bio-capture pot.

[0115] In the quantity control sequence, the amount of bio-waste transferred from each cage is measured using the pumped volume and experienced dry matter content (ratio of bio-waste to water). The accuracy of the quantity measurement can be increased using an electronic quantity and density meter. By emptying the bio- capture pot before and after a feeding period and measuring the amount of bio-waste during the feeding period, a measure of overfeeding can be obtained.

[0116] Fish feed has a stronger and more resilient structure than faeces, which break down more easily into smaller fractions under mechanical stress. The method of the present invention makes it possible to transport bio-waste with minimal water content while retaining the main structure of the feed (and to some extent the faeces) until it is processed. This makes it possible to process bio-waste using a method - particle processing - that cannot be used in the facilities available today. Particle processing involves dewatering without the use of chemicals or energy-intensive machines, separating faeces and feed for separate processing and sanitizing feed for recycling using minimal energy.

Claims

Claims1 . A system for collecting and processing bio-waste from aquaculture enclosures, comprising: a collection unit comprising a bio-waste pot arranged below the closure to collect bio-waste, such as faeces and surplus feed, said bio-waste pot having an upwardly directed opening, a suction line extending through the upwardly directed opening of the biowaste pot and into a lower portion of the bio-waste pot, a suction pump coupled to the suction line for transporting bio-waste, said suction pump being a positive displacement pump, said suction pump being coupled via a transfer line to a processing facility for said bio-waste, valves arranged in the system, and a water transfer minimizing sequence control system operating the suction pump and valves and controlling the transfer of water to said processing facility.

2. The system of claim 1 , wherein said sequence control system is coupled to a sensor that can distinguish between relatively clean water and water with a substantial portion of bio-waste.

3. The system of claim 1 or 2, further comprising a first valve (7) in the suction line for controlling the flow of bio-waste from the bio-waste pot.

4. The system of claim 2, further comprising a second valve (10) in the transfer line upstream of the suction pump.

5. The system of any of the preceding claims, further comprising at least one dump line (17) coupled to the transfer line downstream of the suction pump.

6. The system of claim 5, wherein the dump line returns water to the aquaculture enclosure from which the water originated.

7. The system of claim 5 or 6, wherein the dump line (17) is coupled to the transfer line at a position immediately upstream of said processing facility.

8. The system of any of the preceding claims, wherein the suction pump is arranged at a position from the bio-waste pot and up to and including an upper edge of the at least one closure.

9. The system of any of the preceding claims, further comprising a flush pump (12) connected to a flush line for supplying water to the bio-waste pot.

10. The system of claim 9, wherein the flush line is coupled to the bottom of the bio-waste pot.11 . The system of claim 9 or 10, wherein the flush line is coupled to the suction line.

12. The system of any of the preceding claims, further comprising a sensor for detecting the level of bio-waste in the bio-waste pot.

13. The system of claim 1 , wherein the sensor distinguishing between relatively clean water and water with a substantial portion of bio-waste is a turbidity sensor, optical particle counter, laser diffraction sensor, acoustic doppler velocimeter, ultrasonic sensor, conductivity sensor, capacitive sensor, nephelometer, fibre optic sensor or an imaging system.

14. The system of any of the preceding claims, wherein the bio-waste pot has an upper conical portion transitioning to a lower substantially cylindrical portion.

15. A method for collecting and processing bio-waste from aquaculture enclosures, comprising the steps of: capturing bio-waste in a bio-waste pot arranged below the aquaculture enclosure, transporting the bio-waste from the bio waste pot through a suction line using a positive displacement suction pump, the suction line extending from a lower portion of the bio-waste pot through an upwardly directed opening of the bio-waste pot,directing the bio-waste to a processing facility, sensing the presence of bio-waste in the suction line and directing the flow from the suction pump to the processing facility when a substantive portion of the flow is bio-waste, and - directing the flow away from the processing facility when the flow is substantially clean water.

16. The method of claim 15, further comprising supplying substantially clean flushing water to the bio-waste pot.

17. The method of claim 16, further comprising the step of using freshwater to flush the bio-waste pot.

18. The method of any of the claims 15-17, further comprising the step of dewatering the bio-waste with a filter belt.

19. The method of any of the claims 15-18, further comprising the step of separating feed from faeces using a vibrating screen or filter belt.

20. The method of any of the claims 15-19, further comprising the step of hygienizing the separated feed for reuse.

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