WO2023007167A1

WO2023007167A1 - Filtration module for a floating fish farm tank outlet and methods

Info

Publication number: WO2023007167A1
Application number: PCT/GB2022/051986
Authority: WO
Inventors: Douglas Ian HUNTER; Benjamin James HADFIELD
Original assignee: Mowi Scotland Limited
Priority date: 2021-07-29
Filing date: 2022-07-28
Publication date: 2023-02-02
Also published as: GB2609424A; GB202110953D0

Abstract

Filtration Module (104, 204) and MethodsA filtration module (104, 204) for a floating fish farm tank (101, 1) outlet (107, 207). The filtration module (104, 204) comprises a filter inlet (105, 205) connectable to the fish farm tank outlet (103), a first filtration compartment (106, 206) fluidly connected to the filter inlet (105, 205), and a filter outlet (107, 207). Also disclosed is a floating fish farm tank (101, 1) comprising a plurality of tank outlets (103, 3) and a filtration module (104, 204) for each tank outlet (103), wherein each of the filtration modules comprises a filter inlet (105, 205) connectable to the fish farm tank outlet (103), a first filtration compartment (106, 206) fluidly connected to the filter inlet (105, 205), and a filter outlet (107, 207), and the filter inlet (105, 205) of each filtration module (104, 204) is connected to its respective tank outlet (103). Also disclosed is a method of filtering water from a floating fish farm tank (101, 1), the method comprising: a nutrient filtration step (401), the nutrient filtration step (401) comprising passing the water over mussels and/or seaweed, and/or a solid waste filtration step (402), the solid waste filtering step comprising passing the water over sediment containing bioturbating re-workers.

Description

FILTRATION MODULE FOR A FLOATING FISH FARM TANK OUTLET AND METHODS

Technical Field

The present disclosure relates to filtration of waste water from floating fish farm tanks, particularly, but not exclusively, a filtration module for a floating fish farm tank outlet.

Background

Floating fish farms are often used in seas or lochs to enclose farmed fish. Traditionally, fish farm enclosures have been made of net which means that water, nutrients, waste products and small creatures can flow freely between the wild environment and the enclosure of the fish farm. This has several disadvantages such as the possibility of disease spreading between wild and farmed fish, the easy flow of fish food out of the enclosure, and passage of small creatures into the fish farm.

Floating fish farm tanks have been developed which have water impermeable walls which may be made from a solid material or an impermeable fabric, meaning that the farmed fish are better separated from the surrounding wild environment of the sea/loch. This advantageously means that farmed fish and wild fish are separated by an impermeable tank wall and therefore disease spread between farm and wild populations is not possible. Further, small creatures cannot simply pass into the fish enclosure through holes in the net and contents of the fish farm tank such as fish food can only exit the tank by flowing through outlets of the tank.

Summary of invention

There is provided a filtration module for a floating fish farm tank outlet, the filtration module comprising: a filter inlet connectable to the fish farm tank outlet, a first filtration compartment fluidly connected to the filter inlet, and a filter outlet.

When the filtration module is connected to the outlet of the fish farm tank, water from the tank outlet will pass through the filter inlet of the filtration module, through the first filtration compartment where the water will undergo filtration and out of the filter outlet. By fitting a filtration module to an outlet of the tank, the quality of water released from the fish farm tank into the surrounding water can be improved, thereby reducing the impact of the fish farm on the environment.

The filtration module may further comprise a second filtration compartment, the second filtration compartment being fluidly connected to the first filtration compartment and the filter outlet being fluidly connected to the second filtration compartment. Including a further filtration compartment enables multiple types of filtration to take place sequentially, enabling a better quality of filtering of water from the fish farm. For example, different types of filter substrate can be included in each filtration compartment.

The first and/or second filtration compartment may comprise a nutrient filtration compartment, the nutrient filtration compartment containing mussel lines. The mussel lines may be suspended from a roof of the nutrient filtration compartment. Having mussel lines in the nutrient filtration compartment means that mussels can efficiently grow in the nutrient filtration compartment. When the filtration module is in use, mussels and/or seaweeds consume nutrients dissolved in the water from the fish farm tanks, thereby filtering the nutrients from the water.

The nutrient filtration compartment may comprise mussels which may be on mussel lines. The nutrient filtration compartment may further comprise seaweed, which may be on the mussel lines. The mussels and/or seaweed may be added after the filtration module has been installed or immediately prior to installation. This may ensure the mussels and/or seaweed does not degrade or perish prior to installation, when the filtration module may be dry.

The nutrient filtration compartment may have an outer wall which separates the inside of the nutrient filtration compartment from the outside of the filtration module. The nutrient filtration compartment may have an impermeable outer wall. In this way, waste water cannot leave the compartment through the walls and must pass through the length of the compartment. Further, water from the environment cannot enter the compartment through the outer wall. Alternatively, the nutrient filtration compartment may have apertures and/or slots in the outer wall or may comprise a permeable outer wall. In this way, water may be exchanged with the outside environment which may be preferable for the health of the mussels and/or seaweed. The nutrient filtration compartment may be sealed except for a nutrient compartment inlet and a nutrient compartment outlet. This ensures that the waste water travels through the length of the compartment and cannot escape the filter process too early and ensures that creatures from the outside environment cannot enter the compartment.

The nutrient filtration compartment inlet may be connected or integral with the filter inlet or with another filtration compartment outlet. The nutrient filtration compartment outlet may be connected or integral with the inlet of another filtration compartment or the filter outlet.

In this application, an outer wall is a wall which separates the inside of a filtration compartment from the outside environment. As discussed above, it may have apertures or slots and/or may be permeable or impermeable.

The nutrient filtration compartment may be removable from the filtration module. This facilitates ease of cleaning the compartment and/or replacing the mussels and/or seaweed. The nutrient filtration compartment may be emptiable. For example, the nutrient filtration compartment may have an openable door. This may allow the mussel lines to be removed.

The first and/or second filtration compartment may comprise a solid waste filtration compartment, the solid waste filtration compartment comprising a sediment support structure. The solid waste filtration compartment may comprise sediment which may be supported in the compartment by the sediment support structure. The sediment may be seabed sediment. The sediment may include sand, and/or silt and/or soil. The sediment may comprise bioturbating re-workers such as nematodes. The bioturbating re-workers feed on solid waste, for example fish food and fish faecal matter, in the waste water from the fish farm and thereby break it down. Advantageously, the nematodes do not produce pollutants. This acts to filter solid waste from the water. The sediment and/or bioturbating re-workers may be added after the filtration module has been installed or immediately prior to installation.

The sediment support structure may comprise a folded or coiled channel. The sediment support structure may be a helical channel. This ensures a large surface area of the sediment support structure so that the bioturbating re-workers act over a large area, thereby filtering the solid waste effectively. A further advantage of the folded, coiled or helical shape of the sediment support structure is that the speed of the waste water will be reduced, thereby giving a longer time in the compartment for filtering to take place. In use, solid waste may fall out of the waste water to the sediment supported by the sediment support structure and then be broken down by the bioturbating re-workers.

The solid waste filtration compartment may have an outer wall which separates the inside of the solid waste filtration compartment from the outside of the filtration module. The solid waste filtration compartment may have an impermeable outer wall. In this way, waste water cannot leave the compartment through the walls and must pass along the sediment support structure. Further, water from the environment cannot enter the compartment through the outer wall. Alternatively, the solid waste filtration compartment may have apertures and/or slots in the outer wall or may comprise a permeable outer wall. In this way, water may be exchanged with the outside environment which may be preferable for the health of the bioturbating re-workers. The solid waste filtration compartment may be sealed except for a solid waste filtration compartment inlet and a solid waste compartment outlet. This ensures that the waste water travels through the length of the compartment and cannot escape the filter process too early and ensures that creatures from the outside environment cannot enter the compartment.

The solid waste filtration compartment inlet may be connected or integral with another filtration compartment outlet or with the filter inlet. The solid filtration compartment outlet may be connected or integral with the filter outlet or with the inlet of another filtration compartment. The solid waste filtration compartment may be removable from the filtration module. This facilitates ease of cleaning the compartment and/or changing the sediment composition and/or replacing the sediment. The solid waste filtration compartment may be emptiable. For example, the solid waste filtration compartment may have an openable door allowing ejection of the sediment.

The nutrient filtration compartment and the solid waste filtration compartments may be used sequentially. As such, the filtration module may comprise: the filter inlet connectable to the fish farm tank outlet, the nutrient filtration compartment fluidly connected to the filter inlet, the nutrient filtration compartment comprising mussel lines, the solid waste filtration compartment fluidly connected to the nutrient filtration compartment, the solid waste filtration compartment comprising a sediment support structure, and the filter outlet, the filter outlet fluidly connected to the solid waste filtration compartment.

The filter inlet may comprise a hole in the first filtration compartment or a pipe connected to the first filtration compartment. The filter inlet may be sized to match the tank outlet pipe such that the filter inlet is connectable to the tank outlet by insertion of the tank outlet into the inlet of the filtration module. The filter inlet of the filtration module may be connectable to the tank outlet by a friction fit, a clamp and/or using a compressible seal.

The filtration module may further comprise mussel line fixings. The mussel line fixings may be on the outside of an outer wall of the filtration module or may be on or attachable to a bottom surface of the floating fish farm tank. The outer wall of the filtration module may have an outlet side, the outlet side being a side through which the outlet passes. The fixings may be on the outlet side of the outer wall. The fixings may be hooks or loops that mussel lines may be hung from. The fixings may be attached to the outside of the outer wall of the second filtration compartment. The filtration module may further comprise outer mussel lines, which may be hung on the mussel line fixings or resting on the bed (e.g. seabed, lochbed) beneath the fish farm tank. The filtration module may further comprise mussels on the outer mussel lines. In this way, mussels can be grown in water expelled from the filter outlet. The water expelled from the filter outlet is nitrate rich which beneficially feeds mussels on the outer mussel lines. This filters the nitrate from the water and means that water leaving the area under the fish farm tank is clean. Advantageously, this also enables the mussels to grow effectively and healthily, so the mussels may be harvested.

The mussel lines in the nutrient filtration compartment may be referred to as inner mussel lines to distinguish them from the outer mussel lines which are outside of the filtration compartments, for example, hung on the fixings or resting on the seabed.

The filtration module may be connected to an outlet of a fish farm tank.

There is further provided a floating fish farm tank comprising a tank outlet and a filtration module as described above, wherein the filter inlet is connected to the tank outlet. The fish farm tank may comprise a plurality of tank outlets and a filtration module for each tank outlet, wherein each of the filtration modules is as described above, and the filter inlet of each filtration module is connected to its respective tank outlet. The tank may comprise an impermeable side wall. The side wall may be made from a solid plastics material or from an impermeable fabric material, such as a tarpaulin material.

There is further provided, a kit comprising: a filtration module for a floating fish farm tank outlet comprising: the filter inlet connectable to the fish farm tank outlet, the nutrient filtration compartment fluidly connected to the filter inlet, the nutrient filtration compartment comprising mussel lines, the solid waste filtration compartment fluidly connected to the nutrient filtration compartment, the solid waste filtration compartment comprising a sediment support structure, and the filter outlet, the filter outlet fluidly connected to the solid waste filtration compartment, and sediment for use in the solid waste filtration compartment, and/or mussels, and/or seaweed. The kit may further comprise mussel line fixings attachable to the bottom of the floating fish farm tank. The kit may further comprise mussel lines. There is further provided a method of installing a filtration module as described above on a floating fish farm tank outlet, the method comprising: providing the filtration module, and connecting the filter inlet to the tank outlet.

The method of installing may further comprise putting mussel lines in the nutrient filtration compartment. The method of installing may further comprise putting mussels onto mussel lines in the nutrient filtration compartment. The method of installing may further comprise putting seaweed onto mussel lines in the nutrient filtration compartment. The method of installing may further comprise putting the sediment into the solid waste filtration compartment. The method of installing may further comprise collecting the sediment from the sea or loch bed. The method of installing may further comprise compiling the sediment by mixing ingredients. The ingredients may be sand, silt, soil and/or nematodes. The method of installing may further comprise hanging outer mussel lines from fixings on the filtration module and/or on the bottom of the floating fish farm tank. The method of installing may further comprise attaching the mussel line fixings to the outside of the outer wall of the filtration module and/or to the bottom of the floating fish farm tank. The method of installing may further comprise laying outer mussel lines on the sea or loch bed under the floating fish farm tank. The method of installing may further comprise putting mussels onto outer mussel lines.

There is further provided a method of filtering water from a floating fish farm tank, the method comprising: a nutrient filtration step, the nutrient filtration step comprising passing the water over mussels and/or seaweed, and/or a solid waste filtration step, the solid waste filtering step comprising passing the water over sediment containing bioturbating re-workers.

The method may further comprise a nitrate filtration step, the nitrate filtration step comprising passing the water over mussels. The nitrate filtration step may occur after the nutrient filtration and/or solid waste filtration steps. The steps may be performed in any order. Preferably, the nutrient filtration step is performed first, followed by the solid waste filtration step, followed optionally by the nitrate filtration step.

The nutrient filtration step may comprise passing the water over mussels and/or seaweed in a compartment sealed from the wild environment. The solid waste filtration step may comprise passing the water over sediment containing bioturbating re-workers in a compartment sealed from the wild environment. In this way, unfiltered water cannot pass into the wild environment.

The floating fish farm tank may have a tank outlet and a filtration module as described above connected to the tank outlet, and the method of filtering water may comprise passing water from the floating fish farm tank through the tank outlet and into the filtration module.

The method of filtering water from a floating fish farm tank may further comprise the method of installing the filtration module as described above.

Further features and advantages of the aspects of the present disclosure will become apparent from the claims and the following description.

Brief Description of Drawings

Embodiments of the present disclosure will now be described by way of example only, with reference to the following diagrams, in which: -

Fig. 1 shows a perspective view of the underside of a floating fish farm tank;

Fig. 2 shows a schematic side view of a floating fish farm tank with filtration modules connected to the tank outlets;

Fig. 3 shows a schematic cut-through view of a filtration module;

Fig. 4 shows a flow chart of a method of filtering water from a floating fish farm tank. Detailed Description

A number of different embodiments of the disclosure are described subsequently. In order to minimise repetition, similar features of the different embodiments are numbered with a common two-digit reference numeral and are differentiated by a third digit placed before the two common digits. Such features are structured similarly, operate similarly, and/or have similar functions unless otherwise indicated.

Fig. 1 shows a floating fish farm tank 1 having solid, water impermeable walls 2 meaning that the farmed fish in the tank 1 are separated from the surrounding wild environment of the sea/loch in which the tank 1 is situated. The water impermeable walls 2 may be made from a solid plastics material or from a water impermeable fabric. Farmed fish in the tank 1 and wild fish outside the tank are separated by solid tank wall 2 and therefore disease spread between farm and wild populations is not possible.

In use, the floating fish farm tank is towed to its desired location and then sunk to the desired depth in the sea/loch/other water body. Once in position, water is pumped into the tank 1 from the surrounding environment and waste water exits the tank via tank outlets 3. The waste water exits the tank outlets into the surrounding environment of the sea/loch. Tanks may have any number of tank outlets and in the example of Fig. 1, the tank 1 has eight tank outlets 3.

Fig. 2 shows a floating fish farm tank 101 having solid, impermeable walls 102 and tank outlets 103. Two outlets 103 are shown in Fig. 2. A filtration module 104 is connected to each of the outlets 103. The filtration modules are identical and each have the features explained below.

The filtration module 104 has a filter inlet 105 connected to the fish farm tank outlet 103, a first filtration compartment 106 fluidly connected to the filter inlet 105, and a filter outlet The first filtration compartment 106 has an outer wall 109 which separates the inside of the filtration compartment 106 from the outside environment. The outer wall 109 is solid and impermeable to water, thereby forcing water entering the filter inlet 105 to travel through the filtration compartment 106 and out of the filter outlet 107. As can be seen in Fig. 2, the outlet 107 is situated in the lower side of the outer wall 109 of the filtration module. So, the lower side may be referred to as the outlet side of the filtration module 104.

The filtration module 104 has outer mussel lines 108 attached to the outer wall 109. The outer mussel lines 108 are attached to the outside of the outlet side of the outer wall 109 of the filtration module.

The outer mussel lines may be connected to the outer wall 109 by hanging the lines 108 on fixings attached to the outside of the outer wall 109 at the outlet side. The fixings may be hooks or loops that mussel lines may be hung from.

In an alternative embodiment, outer mussel lines may be laid along the sea/loch bed 110. This may be in addition to or instead of the outer mussel lines 108 which hang from the filtration module.

The filter inlet 105 is connected to the tank outlet 103, so that waste water exiting outlet 103 flows into the filter inlet 105. The waste water will then pass through the first filtration compartment 106 where the water will undergo filtration and out of the filter outlet 107. The water will then pass over the outer mussel lines 108 where mussels on the mussel lines feed on nitrate in the waste water, thereby further filtering the waste water. The water expelled from the filter outlet 107 is nitrate rich which beneficially feeds mussels on the outer mussel lines 108.

The filter inlet 105 in Fig. 2 is a hole in the outer wall 109 of the first filtration compartment. The filter inlet 105 is sized to match the tank outlet 103 such that the filter inlet 105 is connected to the tank outlet 103 by insertion of the tank outlet into the filter inlet. The filter inlet 105 may be connected to the tank outlet 103 by a friction fit, a clamp and/or using a compressible seal. The filtration module 104 can be installed by simply connecting the filter inlet 105 to the tank outlet 103. During installation, the outer mussel lines 108 can be hung from fixings on the outer wall 109. The mussel line fixings may be attached to the outside of the outer wall 109. The method of installing may further include laying outer mussel lines on the sea or loch bed 110 under the floating fish farm tank 101. Installation may further include putting mussels onto outer mussel lines.

Inner mussel lines, mussels and/or seaweed may be placed in the filtration compartment 106. Alternatively, sediment may be put into the filtration compartment 106. The sediment may be collected from the sea or loch bed or compiled by mixing ingredients such as sand, silt, soil and/or nematodes.

Filtering waste water from tank outlet 103 using the filtration module 104 includes, a filtration step in the filtration compartment 106. For example this may be a solid waste filtration step or a nutrient filtration step or both. Then a nitrate filtration step occurs by passing the water over mussels on the outer mussel lines 108. The nitrate filtration step occurs after the waster passes out of the filter outlet 107 and so occurs after the nutrient filtration and/or solid waste filtration steps in the filtration compartment 106.

Fig. 3 shows a filtration module 204 which is connectable to a tank outlet. The filtration module204 has a filter inlet 205 connectable to a fish farm tank outlet, a first filtration compartment 206 fluidly connected to the filter inlet 205, and a filter outlet 207. The filtration module 204 also has a second filtration compartment 211, the second filtration compartment 211 is fluidly connected to the first filtration compartment 206 by opening 212 and the filter outlet 207 being fluidly connected to the second filtration compartment 211.

The first filtration compartment 206 is a nutrient filtration compartment and contains inner mussel lines 213. The inner mussel lines 213 are suspended from a roof of the nutrient filtration compartment. When the filtration module is in use, mussels and/or seaweeds on the inner mussel lines 213 consume nutrients dissolved in the water from the fish farm tanks, thereby filtering the nutrients from the water. The nutrient filtration compartment 206 has an impermeable outer wall 214 which separates the inside of the nutrient filtration compartment from the outside of the filtration module. In this way, waste water cannot leave the compartment through the outer wall 214 and must pass through the length of the compartment from the filter inlet 205 to the opening 212. Further, water from the environment cannot enter the compartment through the outer wall 214. The nutrient filtration compartment is sealed except for a nutrient compartment inlet which is integral with the filter inlet 205 and a nutrient compartment outlet which is formed by opening 212 and is integral with the inlet of the second filtration compartment 211.

The nutrient filtration compartment is removable from the filtration module. This facilitates ease of cleaning the compartment and/or replacing the mussels and/or seaweed.

The second filtration compartment 211 is a solid waste filtration compartment, the solid waste filtration compartment has a helical sediment support structure 215. The sediment support structure holds sediment in the solid waste filtration compartment. The sediment including sand, silt and soil along with bioturbating re-workers such as nematodes. The bioturbating re-workers feed on solid waste, for example fish food and fish faecal matter, in the waste water from the fish farm and thereby break it down and filter the solid waste from the water.

The sediment support structure 215 is a helical channel which ensures a large surface area of the sediment support structure so that the bioturbating re-workers act over a large area, thereby filtering the solid waste effectively.

The solid waste filtration compartment 211 has an impermeable outer wall 216 which separates the inside of the solid waste filtration compartment from the outside of the filtration module. The impermeable outer wall 216 means that waste water must pass along the helical channel of the sediment support structure 215. The solid waste filtration compartment 211 is sealed except for a solid waste filtration compartment inlet and a solid waste compartment outlet. The solid waste filtration compartment inlet is integral with the first filtration compartment outlet at opening 212 and the solid filtration compartment outlet is integral with the filter outlet 207.

The solid waste filtration compartment 211 is removable from the filtration module 204. This facilitates ease of cleaning the compartment and/or changing the sediment composition and/or replacing the sediment.

The filter inlet 205 is a pipe connected to the first filtration compartment 206. The filter inlet is sized to match the tank outlet pipe of the floating fish farm tank.

The outer wall 209 of the filtration module 204 separates the inside of the filtration compartments 206 and 211 from the outside of the filtration module. The outer wall 209 of the filtration module comprises the outer wall 214 of the first filtration compartment 206 and the outer wall 216 of the second filtration compartment 211.

The filtration module 204 has mussel line fixings on the outside of the outer wall 209. The outer wall 209 has an outlet side, the outlet side being a side which is crossed by the outlet 207. The mussel line fixings are on the outlet side of the outer wall 209. The fixings are hooks or loops that outer mussel lines 208 are hung from. The fixings are attached to the outside of the outer wall 216 of the second filtration compartment 211. Mussels may be grown on the outer mussel lines 208. The water expelled from the filter outlet is nitrate rich which beneficially feeds mussels on the outer mussel lines. This filters the nitrate from the water and means that water leaving the area under the fish farm tank is clean. Advantageously, this also enables the mussels to grow effectively and healthily, so that they may be harvested.

The mussel lines 213 in the nutrient filtration compartment may be referred to as inner mussel lines to distinguish them from the outer mussel lines 208 which are outside of the filtration compartments, for example, hung on the fixings or resting on the seabed.

Installation of the filtration module 204 can be achieved by simply connecting the filter inlet to the tank outlet. The filtration module 204 filters the water from a floating fish farm tank according to the method outlined in Fig. 4.

The method shown in Fig. 4 includes a nutrient filtration step 401, the nutrient filtration step comprising passing the water over mussels and/or seaweed, a solid waste filtration step 402, the solid waste filtering step comprising passing the water over sediment containing bioturbating re-workers, a nitrate filtration step 403, the nitrate filtration step comprising passing the water over mussels, and then the water is released to the environment surrounding the filtration module.

The nutrient filtration step 401 involves passing the water over mussels and/or seaweed, optionally in a compartment sealed from the wild environment such as the first filtration compartment 206. The mussels and/or seaweed consume nutrients dissolved in the water, thereby filtering the nutrients from the water.

The solid waste filtration step 402 involves passing the water over sediment containing bioturbating re-workers, optionally in a compartment sealed from the wild environment such as the second filtration compartment 211. By using sealed compartments, unfiltered water cannot pass into the wild environment.

Although particular embodiments of the disclosure have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the invention.

It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the scope of the invention as defined by the claims.

Claims

1. A filtration module for a floating fish farm tank outlet, the filtration module comprising: a filter inlet connectable to the fish farm tank outlet, a first filtration compartment fluidly connected to the filter inlet, and a filter outlet.

2. A filtration module according to claim 1, wherein the first filtration compartment comprises a nutrient filtration compartment, the nutrient filtration compartment containing mussel lines.

3. A filtration module according to claim 2, wherein the nutrient filtration compartment further comprises mussels and/or seaweed.

4. A filtration module according to any preceding claim, the filtration further comprising a second filtration compartment, the second filtration compartment being fluidly connected to the first filtration compartment and the filter outlet being fluidly connected to the second filtration compartment.

5. A filtration module according to claim 4, wherein the second filtration compartment comprises a solid waste filtration compartment, the solid waste filtration compartment comprising a sediment support structure.

6. A filtration module according to claim 6, wherein the solid waste filtration compartment further comprises sediment, the sediment supported in the compartment by the sediment support structure.

7. A filtration module according to claim 6 wherein the sediment comprises bioturbating re-workers.

8. A filtration module according to claim 6 or claim 7, wherein the sediment support structure comprises a folded or coiled channel.

9. A filtration module according to claim 8 wherein the sediment support structure comprises a helical channel.

10. A filtration module according to any of claims 5 to 9, wherein the solid waste filtration compartment is removable from the filtration module.

11. A filtration module according to any preceding claim, further comprising outer mussel lines, the outer mussel lines being outside of the filtration compartment(s).

12. A filtration module according to any preceding claim, the filtration module further comprising mussel line fixings on the outside of an outer wall of the filtration module.

13. A filtration module according to claim 11, wherein the outer wall of the filtration module has an outlet side, the outlet side being a side through which the outlet passes and, wherein the fixings are on the outlet side of the outer wall.

14. A filtration module according to any preceding claim, wherein the filtration module is connected to an outlet of a floating fish farm tank.

15. A floating fish farm tank comprising a tank outlet and a filtration module according to any of claims 1 to 13, wherein the filter inlet is connected to the tank outlet.

16. A floating fish farm tank comprising a plurality of tank outlets and a filtration module for each tank outlet, wherein each of the filtration modules is according to any of claims 1 to 13, and the filter inlet of each filtration module is connected to its respective tank outlet.

17. A kit comprising: a filtration module for a floating fish farm tank outlet according to claim 1, claim 2 and claim 5, and sediment for use in the solid waste filtration compartment, and/or mussels, and/or seaweed, and/or mussel lines, and/or mussel line fixings attachable to the bottom of the floating fish farm tank.

18. A method of installing a filtration module on a floating fish farm tank outlet, the method comprising: providing the filtration module, and connecting the filter inlet to the tank outlet, wherein the filtration module is according to any of claims 1 to 13.

19. A method of installing a filtration module on a floating fish farm tank outlet according to claim 18, when the filtration module is according to claim 7, wherein the method further comprises collecting the sediment from the sea or loch bed and putting the sediment into the solid waste filtration compartment.

20. A method according to claim 18 or 19, the method of installing further comprising: hanging outer mussel lines from fixings on the filtration module and/or on the bottom of the floating fish farm tank, or laying outer mussel lines on the sea or loch bed under the floating fish farm tank.

21. A method of filtering water from a floating fish farm tank, the method comprising: a nutrient filtration step, the nutrient filtration step comprising passing the water over mussels and/or seaweed, and/or a solid waste filtration step, the solid waste filtering step comprising passing the water over sediment containing bioturbating re-workers.

22. A method of filtering according to claim 21, the method of filtering further comprising: a nitrate filtration step, the nitrate filtration step comprising passing the water over mussels, the nitrate filtration step occurring after the nutrient filtration and/or solid waste filtration steps.

23. A method of filtering according to claim 21 wherein the nutrient filtration step and/or the solid waste filtration step occur in a compartment sealed from the wild environment.

24. A method of filtering water from a floating fish farm tank according to any of claims 21 to 23, wherein the floating fish farm tank is according to claim 15 or 16 and the method of filtering water comprises passing water from the floating fish farm tank through the tank outlet and into the filtration module.

25. A method of filtering water according to claim 24, the method further comprising the method of installing the filtration module according to any of claims 18 to 20.