NO20231263A1 - Arrangement and method for treatment of fish - Google Patents

Description

ARRANGEMENT AND METHOD FOR TREATMENT OF FISH

Technical Field

[0001] The present invention relates to an arrangement for treatment of fish, especially farmed salmon.

Background Art

[0002] Parasites, such as lice on farmed fish has been a significant problem for a long time. In the early years of fish farming, this was solved by the use of chemicals. However, some of the chemicals turned out not to be very environmentally friendly. Consequently, there has been put a lot of effort into finding other methods of treating the fish, predominantly salmon, to reduce the number of parasites. The methods range from mechanical, such as brushes and jet spray to laser and lump fish.

[0003] A method that has proved to be both effective with regard to lice and kind to the fish, is to expose the fish to warm water, such as around 28-34 degrees Celsius, for a period of time, such as 30 seconds to 1 minute. The warm water will weaken the lice and cause it to lose its grip on the fish.

[0004] Attempts have also been made to expose the fish to cold water or brine having a temperature of -1 degree Celsius or lower. The exposure time will then have to be up to 1 1⁄2 minute.

[0005] Another method is to expose the fish to freshwater for some time. This requires exposure for four to eight hours and is therefore less efficient than warm water.

[0006] The following patent references describe arrangements for treatment of fish by warm water:

[0007] NO332298 describes an arrangement where the fish is fed through a closed system comprising a U-shaped pipe containing a bath of warm water. The warm water is separated from the fish at a downstream separator and returned to the inlet of the pipe by a recirculating pump.

[0008] NO342036 shows an arrangement where the fish is transported through a bath of warm water by rotating vanes extending into the bath. In this arrangement too, the warm water will be recirculated.

[0009] Although the above two arrangements have proved to be suitable for delousing treatment of the fish, there is still room for increasing the efficiency and water quality and ensure that the fish health does not suffer substantially from the treatment. Consequently, the fish should have a consistent treatment time, so that no fish is exposed to the treatment longer than the prescribed time. This means that the fish should be fed through the arrangement according to the first in – first out principle. Both the above-mentioned known arrangements work according to this principle, but they do have an upper limit on the capacity as the fish has to be conveyed rather slowly through the arrangement to ensure a sufficiently long retention time.

[0010] NO 341934 describes a fish treatment facility for delousing fish using cold water. The fish is fed from one pen to another through a zig-zag pipe. At both ends of the zig-zag pipe water is separated from the fish. The water in the zig-zag pipe is recirculated. There are no means described to remove the CO2 from the water.

[0011] NO 20160441 describes a transport system for conveying fish from a treatment pen to a receiving pen. There is no treatment of the fish during the transport. The water is separated from the fish just before the fish enters the receiving pen. The separated water is fed through an aerator to remove CO2. The aerated water is conducted back to the treatment pen.

Summary of invention

[0012] The present invention has as its main objective to increase the capacity of a treatment facility as well as efficiency, water quality and fish health. By providing a long pipe containing warm water and actively pumping fish through the pipe, it will be possible to feed a higher number of fish through the bath and still maintain the prescribed retention time for the fish in the bath.

[0013] Without any intention to limit the selection, by treatment liquid in the following, the intention is to cover all types of liquid that fish may be exposed to remove or reduce parasites, such as gyrodactylus salaris, cure or prevent diseases or reduce negative effects of diseases, or in general improve fish health. The liquid may be warm water, cold water, freshwater, seawater, brine, water containing chemicals, such as anti-parasite agents, ozone, antibiotics or vitamins, or a combination of one or more of such liquids. In the detailed description warm water will be used as an example of a treatment liquid.

[0014] The objects of the invention are achieved by an arrangement for treatment of fish, comprising a pipe extending from an inlet to an outlet; further comprising a supply of treatment liquid into an upstream section of said pipe, wherein said pipe comprises an in-line carbon dioxide aerator downstream of said upstream section.

[0015] By in-line aerator is meant an aerator through which the whole content of water and fish the pipe flows. No water or fish is separated from the pipe before it enters the aerator, and the same water and fish leaves the aerator.

[0016] In a preferred embodiment the pipe has said upstream section, an intermediate section and a downstream section, said intermediate section connecting said upstream and downstream sections and said upstream and downstream sections being elevated with respect to said intermediate section, said supply of treatment liquid supplying liquid into said pipe upstream of said intermediate section. This will ensure that the treatment liquid largely fills the pipe along the intermediate section.

[0017] The arrangement may also comprise a counter-flow unit at a downstream end of the pipe to retain treatment liquid inside the pipe.

[0018] It is further preferred that the carbon dioxide aerator comprises a walled structure attached to said pipe, said walled structure having an opening into the interior of said pipe and an opening to the environment or to a suction unit. This provides a simple, robust, and reliable structure.

[0019] Preferably, the pipe is perforated within the walled structure to ensure that CO2 can escape but fish is kept inside the pipe.

[0020] If the aerator comprises an air supply the CO2 will be more efficiently expelled.

[0021] Preferably, said air supply comprises an air duct with a fan to force air into the aerator.

[0022] In a further preferred embodiment, the arrangement comprises a second supply of treatment liquid immediately upstream of or into said carbon dioxide aerator. This supply will enhance the aeration of CO2, supply liquid with a higher oxygen level, boost the quality of the treatment liquid, such as the temperature and increase flow.

[0023] In one embodiment, said second supply is directed at an angle with the flow of treatment liquid in the pipe, which will create turbulence in the flow of the pipe and kick CO2 out of the liquid.

[0024] In an alternative embodiment, said second supply is into an upper part of said walled structure of said aerator. The rain of water will enhance the expulsion of CO2 out of the liquid.

[0025] In a further embodiment, said walled structure comprises a grate extending across the walled structure below said second water supply to distribute the liquid over the cross-section of the aerator.

[0026] It is an advantage if the intermediate section of the pipe has a length of at least 50 meters. The length may also be up to 70 meters. This ensures that the fish will be subjected to the treatment liquid for a sufficiently long time while still maintaining a rapid flow of fish through the arrangement.

[0027] Preferably, the arrangement has an outlet for waste treatment liquid and an inlet for replacement treatment liquid. Thereby a targeted replacement of treatment liquid and hence maintenance of the quality of the treatment can be achieved.

[0028] The invention also resolves the object of the invention by a method of treatment of fish, where the fish is conveyed through a pipe together with a treatment liquid, where said treatment liquid is supplied into said pipe at a first location along said pipe, wherein carbon dioxide is aerated from said pipe at a second location downstream from said first location.

[0029] In one embodiment, the additional treatment fluid is supplied into said pipe immediately upstream of or at said second location. This supply will enhance the aeration of CO2, supply liquid with a higher oxygen level, boost the quality of the treatment liquid, such as the temperature and increase flow.

[0030] Preferably, a portion of the treatment liquid is continuously replaced. Thereby a targeted replacement of treatment liquid and hence maintenance of the quality of the treatment can be achieved.

[0031] It has been found that at least 15 % of the treatment liquid should be replaced per hour of operation. However, up to 100 % may also be replaced, especially if the treatment liquid can be expelled directly into the sea.

[0032] Preferably, said treatment liquid is warm water having a temperature of 28-34°C when it is supplied. This has proved to weaken parasites substantially with minimal negative effects on the fish.

[0033] A supply of oxygen into the treatment liquid will maintain quality and fish health.

[0034] In some embodiments, the fish may be rinsed with seawater downstream of said pipe. This will remove any residual treatment liquid remaining on the fish and prevent pollution of the sea,

Brief description of drawings

[0035] The invention will now be described, referring to a preferred embodiment of the invention, shown in:

Figure 1 shows an isometric view of the arrangement according to the invention,

Figure 2 shows the arrangement of figure 1 in planar view,

Figure 3 shows a sketch illustrating a CO2 aerator in the arrangement.

Detailed description of the invention

[0036] Referring to figure 1, the arrangement of the invention will now be described. The arrangement is conveniently situated on board a boat, such as a well-boat. However, the arrangement may also be placed on a raft or on shore. The arrangement comprises a pipe 1 extending from an inlet 2 to an outlet 3, through which fish is to be conveyed. In figure 1 is shown two such pipes 1, extending in parallel. It should be understood that there may be one, two or several such pipes, and that more pipes will increase the capacity of the arrangement accordingly. In the following only one of the pipes 1 and its associated components will be described. It should be understood that the other pipe(s) will have the same type of associated components as the first pipe, or that both/all pipe(s) will be connected to the same components, where applicable.

[0037] The pipe 1 is arranged to have a first upstream section 1a and third downstream section1b that are elevated with respect to a second intermediate section 1c, which connects the first and the third sections 1a, 1b. The second section has a length of between 50 and 70 meters.

[0038] Alternatively, the second section 1c may be on the same elevation as the first or third section or both of them. If the second section is at the same elevation as the third section, a counterflow may be established downstream of the second section, such as by a jet flow into the end thereof, to retain the treatment liquid inside the second section.

[0039] Fish is first pumped or otherwise brought on board a tank in the boat. From the tank, the fish is pushed into the arrangement by creating an under-pressure in the tank. The intake into the system is not visible in the figures. Downstream of the intake is a first separator 5 to separate the seawater that has followed the fish from the fish. The separated seawater is expelled through an outlet 2.

[0040] Immediately downstream of the separator 5 warm water is supplied into the pipe 1. This supply is not clearly visible from the figures, but will be supplied from a collecting tank 6, which will be described later, through filters 7, which will filter out lice that have been released from the fish and other debris from the water. Prior to entering the pipe 1, the water is heated in a heat exchanger 8. A heat source 9, such as a fuel burner, electric heater, heat pump or a heat exchanger utilizing waste heat from engine coolant.

[0041] A pump 10 ensures a sufficient velocity of the warm water to transport the fish through the pipe 1.

[0042] The pipe 1 is shown arranged in a horseshoe configuration. If space allows for it, it can also be arranged in a straight line, or if space is more limited, it may be arranged in a serpentine configuration. It is, however, a desire to have as few sharp bends as possible.

[0043] At the third pipe section 1b, lose to the outlet end 3, is a second separator 11 that will separate the warm water from the fish. The warm water is collected in a collecting tank 6 while the fish is expelled to a new habitat, such as a pen or forwarded to processing.

[0044] Some of the collected water is deliberately expelled through an exit port 12. This water may be expelled to the sea, if necessary, after filtering and decontamination. Replacement water to replace the expelled water may be supplied into a supply port 13. To ensure that the replacement water does not immediately exit through the exit port, the collecting tank may have baffles separating the inflow and the outflow or the supply port 13 may be at an opposite end of the tank from the exit port 12. It is convenient to replace about 15 – 100 % of the water per hour of operation, preferably 30 – 50 %. This will ensure that a sufficient oxygen level in the warm water can be maintained even after a long time of operation. It is also possible to add oxygen into the water by per se known means.

[0045] In the second section 1c of the pipe 1 a carbon dioxide (CO2) aerator 14 is arranged. This may conveniently be about 2/3rds of the distance along the second section 1c.

[0046] The aerator 14 is shown more detailed in figure 3. It comprises a four-walled structure 14a having an open bottom and open top and is tightly attached to the pipe 1. Inside the walls of the structure, the pipe 1 is perforated as indicated by reference number 15. Hence, fish is not able to escape into the structure 14a but will continue through the pipe 1.

[0047] Instead of having an open top, the walled structure 14a may be coupled to a suction unit that catches the CO2.

[0048] The walled structure 14a may have an air supply in the form of an air duct 14b. the air duct may have a fan 14c to blow the air into the walled structure 14a.

[0049] A warm water may be supplied either immediately upstream of the aerator 14, as shown in figures 1 and 2 or into the upper part of the walled structure 14a, as shown in figure 3.

[0050] In the first embodiment, an auxiliary pipe 16 extends from the heat exchanger 8 to a set of injection tubes 15. The injection 15 tubes are preferably set at an angle with the flow in the pipe 1. The inflow of water from the injection tubes 15 will create swirls in the water of the pipe 1 and kick CO2 out of the water. The CO2 will be forced out of the open top of the walled structure 14a by the air supplied into this.

[0051] In the alternative embodiment, the warm water is supplied through an inlet 14d near the top of the walled structure 14a. A grate 14e may be arranged between the walls of the walled structure 14a below the inlet 14d to distribute the water over the cross-section of the aerator 14. The water raining down onto the water flowing in the pipe 1 will stir the water and enhance the expulsion of CO2 from the water.

[0052] The auxiliary warm water will have a higher concentration of oxygen and a lower concentration of CO2 than the water already in the pipe.

[0053] The net result is that the warm water will have a lower CO2 concentration and a higher O2 concentration when it reaches the second separator than without the measures taken above. The temperature of the water will also be maintained at a higher level. This means that the fish will be subjected to a lower stress level and that the treatment will be more efficient.

[0054] It has also been found that the auxiliary supply of warm water will prevent a reduction of the temperature of the water. Tests have shown that that the temperature of the treatment water is 0,5 degrees higher when auxiliary water is supplied than without this supply. This increases the efficiency of the treatment.

[0055] A valve may be arranged in connection with the auxiliary pipe 16 to regulate how much water that is supplied to the pipe 1 either immediately upstream of the CO2 aerator or into the CO2 aerator.

[0056] Downstream of the second separator 11 the fish may be rinsed by seawater before it is released into the pen or into another tank in the boat.

Claims (20)

Claims

1. An arrangement for treatment of fish, comprising a pipe (1) extending from an inlet (2) to an outlet (3); further comprising a supply of treatment liquid into an upstream section (1a) of said pipe (1), characterised in that said pipe (1) comprises an in-line carbon dioxide aerator (14) downstream of said upstream section (1a).

2. The arrangement of claim 1, characterised in that the pipe (1) has said upstream section (1a), an intermediate section (1c) and a downstream section (1b), said intermediate section (1c) connecting said upstream and downstream sections (1a, 1b) and said upstream and downstream sections (1a, 1b) being elevated with respect to said intermediate section (1c), said supply of treatment liquid supplying liquid into said pipe (1) upstream of said intermediate section (1c).

3. The arrangement of claim 1, characterised in that it comprises a counter-flow unit at a downstream end of the pipe (1).

4. The arrangement of claim 1, 3 or 3, characterised in that the carbon dioxide aerator (14) comprises a walled structure (14a) attached to said pipe (1), said walled structure (14a) having an opening into the interior of said pipe (1) and an opening to the environment or to a suction unit.

5. The arrangement of claim 4, characterised in that the pipe (1) is perforated within the walled structure (14a).

6. The arrangement of any of the preceding claims, characterised in that the aerator comprises an air supply.

7. The arrangement of claim 4 and 6, characterised in that said air supply comprises an air duct (14b) with a fan (14c).

8. The arrangement of any of the preceding claims, characterised in that it comprises a second supply of treatment liquid (15, 14d) immediately upstream of or into said carbon dioxide aerator (14).

9. The arrangement of claim 8, characterised in that said second supply (15) is directed at an angle with the flow of treatment liquid in the pipe (1).

10. The arrangement of claim 4 and 8, characterised in that said second supply (14d) is into an upper part of said walled structure (14a) of said aerator (14).

11. The arrangement of claim 10, characterised in that said walled structure (14a) comprises a grate (14e) extending across the walled structure (14a) below said second water supply (14d).

12. The arrangement of any of the preceding claims, characterised in that the intermediate section (1c) of the pipe (1) has a length of at least 50 meters.

13. The arrangement of any of the preceding claims, characterised in that it has an outlet (12) for waste treatment liquid and an inlet (13) for replacement treatment liquid.

14. A method of treatment of fish, where the fish is conveyed through a pipe (1) together with a treatment liquid, where said treatment liquid is supplied into said pipe at a first location along said pipe (1), characterised in that carbon dioxide is aerated from said pipe (1) at a second location downstream from said first location.

15. The method of claim 14, characterised in that additional treatment liquid is supplied into said pipe immediately upstream of or at said second location.

16. The method of claims 14 or 15, characterised in that a portion of the treatment liquid is continuously replaced.

17. The method of claim 16, characterised in that at least 15 % of the treatment liquid is replaced per hour of operation.

18. The method of any of the claims 14-17, characterised in that said treatment liquid is warm water having a temperature of 28-34°C when it is supplied.

19. The method of any of the claims 14-18, characterised in that oxygen is supplied into the treatment liquid.

20. The method of any of the claims 14-19, characterised in that the fish is rinsed with seawater downstream of said pipe (1).