Description

Field of the Invention

The invention relates to fish farming facilities. Specifically, a system for minimizing pum p energy and maximizing sedimentation in a closed fish farm where the water flows in one direction through the plant.

BACKGROUND OF THE INVENTION

There are three main problems that cause large losses in the aquaculture industry in the form of lost fish, lost reputation or both. This is:

• lice,

• escape of fish, and

• pollution.

These three problems can be solved using a land-based facility where everything that comes in and out of the fish farm can be controlled. However, this creates a new problem: high costs.

Salmon louse

Salmon louse is a species of copepod. It lives like a marine parasite on salmonids. It feeds on the mucus, skin and blood of the fish. The head is wide and shield-shaped and is used as a suction cup. The back body is narrower and, in the female, filled with eggs. The female's hindquarters also have two long egg sacs or spines. At the free flowing nauplius stage, it has a length of 0.54 to 0.85 mm. In the copepodite stage it is approx. 0.7 mm long and attacks the fish. At the chalimus stage it is 1.2 to 2.8 mm long. Salmon lice are a naturally occurring ectoparasite that have direct transmission between hosts (salmon) by means of planktonic larval stages. They are light sensitive and reside mainly in the top 10 meters of the water masses, where we also produce the salmon. With the increase in salmon production, the problem of salmon lice has also exploded and is the biggest fish health problem the fish farming industry has. The industry has struggled with salmon lice for many years and has been dependent on chemotherapeutic treatments, but its frequent and continuous use has led to the development of reduced sensitivity and resistance to these in salmon lice.

Biological control of the use of lipfish that eat lice has increased in recent years to keep the salmon lice infections down, but the lip fish is sensitive to temperature and thus unsuitable to use where temperatures are below 6 ° C, as we have for periods in the northernmost counties. Salmon lice feed on the skin and mucosal tissues of the fish to cause ulcers, thus exposing it to secondary infections and osmotic stress. Salmon lice have had a major impact on the economy of the aquaculture industry as it results in reduced growth, increased feed intake, downgrading of products and costly treatments. It is estimated that the problem with salmon lice alone is in the order of 150 m€ annually. As of 2017, it is common to spend 2 kroner per kilo of fish on lice control. escape offish

There are a number of ways farmed fish can escape from a farm. Fishing gear, boats and predatory fish can damage the nuts and create an opening so the fish can swim out.

Occasionally, fish farms break down in storms and storms. Accidents happen when the fish is transported between the plants. When smolt is released into the sea it also happens that the nets have too large opening, so that the smallest fish swim straight out of the plant. Some of the escaped fish will find their way back to a river to try and spawn. There it competes with the wild fish for food, destroys spawning grounds and spawns along with wild fish. Farmed fish are bred to grow as fast as possible in captivity. This means that when the breeding genes are mixed with the genes of the wild fish, you get a fish that is less adapted to river life. As many as two of three wild salmon populations have elements of farmed genes. In several rivers, the wild salmon strain is eradicated. This is irreversible damage that impairs the diversity and viability of the salmon.

Contamination

Emissions of nutrients from aquaculture affect the environmental conditions in fjords and coastal waters. The emissions come from feeding and the fish's excrement. Nutrient salts can lead to more frequent algae blooms. In addition, this has effects for the whole ecosystems, as nutritional access increases the production of some organisms, and can change the biological composition. A more acute effect is when the degradation of biological material leads to lower oxygen levels in some sea areas, and the organisms at the bottom die.

The system for minimizing pumping energy and maximizing sedimentation and supplying sufficient oxygen by means of natural seawater without salmon lice to a closed, escape-safe aquaculture facility is based on solid ground, according to claim 1, solving the aquaculture industry's 3 biggest problems without exploding costs like traditional land based farms.

• Salmon lice - solved by removing all water from below the salmon lice's habitat.

• Escape - solved by two barriers: first a barrier in the form of a basin in the rock or concrete with grating in front of the inlet / outlet, and then a barrier in the form of a grille at the outer ends of the inlet / outlet.

• Pollution - is solved by the fact that there is a steady flow in the raceways in one direction that enables optimum sedimentation in the raceway and subsequent collection of sediments transported to the sedimentation tank and sludge depot.

• The resulting problem of large costs is solved by creating a water flow through the land- based aquaculture facility where the levels of the water surfaces in the basin and the raceways, respectively, follow the tide with a maximum difference of approximately 0.

Summary of the Invention

The invention describes a system for minimizing energy consumption and maximizing sedimentation and supplying sufficient oxygen by means of natural seawater without salmon lice to a closed fish farm based on solid ground. The system comprises a closed basin located such that the water inlets and the water outlets have access to two different currents of water, the basin having separate watertight parallel raceways. Each raceway comprises one water intake pipe having at least one escape barrier connected to an inlet end of the raceway and having at least one flow unit which retrieves seawater from below salmon lice level. Each raceway further comprises a water outlet pipe having at least one escape barrier connected to an opposite outlet end of the raceway. The water outlet pipe has an equal cross-sectional area as the inlet pipe and has at least one flow unit and means for sludge extraction from the raceway. The inlet pipes and outlet pipes of the raceways have respectively an inlet opening and an outlet opening located at a level below the lowest low tide and an upper edge of the basin is positioned above the highest high tide. The cross- sectional area (measured in m ² ) in the pipes Ap _ipe and the raceway, A _RW is according to the relation:

Apjpe X Vpipe = ARW X V _R . (1)

where the following restrictions apply:

1. Vpi _pe <1 m/s to minimize energy consumption in the form of resistance in the pipes,

2. V _RW <0.1 m/s to maximize sedimentation in the raceway, and

3. Ap _jpe > 0.016 x ton _fish , such that the farmed fish obtain sufficient oxygen by using natural seawater despite the limited water velocity in the pipes, wherein ton _fish is the maximum number of tons of fish in the raceway and V _RW and Vp _ipe is the water velocity, in the raceway and the pipes respectively.

Brief description of the figures

For a better understanding of the invention, and to show specific embodiments of the invention, reference will now be made, by way of example, to the accompanying figures in which:

Fig. 1 is a top view of a land-based fish farm facility with a basin containing fish raceways. Fig. 2 shows a basin with inlet and outlet as seen from the side.

Fig. 3 Shows a favorable location in a landscape.

Fig. 4 shows a horizontal fish barrier and a vertical separation network in a fish raceway. Fig. 5 shows the relationship between pump power needed and pipe diameter.

Detailed description

In the following, we will describe a system for minimizing pumping energy needed and maximizing sedimentation in a closed fish farm, where sufficient oxygen for the fish is provided by natural seawater. We use the terms 'moving water' and 'flow unit' (Norwegian: 'strpm setter') to emphasize that the water is not 'pumped' in the height direction. The flow unit is causing the water to move or flow.

Figure 1 shows a land-based fish farming facility according to the invention. The fish farm includes a closed fish basin 1 where the water level is kept at the same height as the tide. On one side of the fish farm there is a plurality of water intake pipes 2 which collect seawater from below the salmon lice level as shown in FIG. 2, that is, from below 10 - 15 meters, and on the other side there is a plurality of water outlet pipes 3. In the basin between the inlets and the outlets there is a plurality of fish raceways 4 with a width of 5 to 20 meters. Inlet pipes and outlet pipes 2, 3 of the raceways have an inlet opening 8 and an outlet opening 9 respectively, both of which are located at a level below the lowest low tide. Inlet pipes and outlet pipes are both equipped with at least one escape barrier 16 each as shown in FIG. 2. The depth of the basin is of the same order of magnitude as the width of the raceway 4. Between each raceway there is a waterproof partition. In another embodiment, the breeding channels may be tubular structures resting on the bottom of the basin. The length of the raceway should be roughly 5 to 20 times the width of the raceway, more preferred roughly 10 times the width. An important advantage with a raceway is that it is the only shape that will handle the amount of water that must be transported through the fish farm without turbulence, if the oxygen is taken from natural water. A round shape will create high water velocities, at least in some locations, and turbulence.

The following parameters must be balanced:

• Lowest possible water velocity in the raceway to maximize sedimentation.

• Large enough flow area in the pipes 2, 3 to minimize pump energy.

• High enough water flow in the intake pipes 2 and the outlet pipes 3 to meet the oxygen demand.

• Small enough through flow section in the pipes keep the costs of the pipes and pumps down.

To maximize sedimentation in the fish farm, there must be slow movements in the water. There must be laminar flow and little turbulence. This occurs if the flow rate is low.

Furthermore, the fish farm must be at rest, unaffected by weather, wind and waves. The latter is difficult to achieve with floating fish farms.

To minimize energy consumption, the height of which the water is to be moved must be reduced to close to 0. Furthermore, the friction in the pipes carrying water to a nd from the fish farm must be reduced. Larger diameters of the pipes give less friction pr. volume of water. Different pumping methods give different amounts of turbulence. Slow-moving large propellers produce less turbulence compared to small and fast propellers or turbines.

By founding a closed basin 1, comprised by the fish farm, on solid ground, preferably in close proximity to the sea, the fish farm will be at rest regardless of weather, wind and waves.

By positioning the basin at a height where an upper edge of the basin is above the highest high tide and intake pipes 2 and outlet pipes 3 to and from the basin are below the lowest low tide, energy is only used to move the water, not to lift the water. In order for this to work effectively, inlet pipes and outlet pipes must also have a large diameter in relation to the water needed in the basin in question. The water level in the basin will then follow the tide.

In the described fish farm, only millimeters separate the water level in the surrounding sea and the basin and large-diameter pipes and low water velocities are used to minimize turbulence and return pressure caused by level differences and friction. The larger the diameter of the inlet and the outlet pipes 2, 3 the smaller the level difference between the sea and the basin (if the flow units are running only on one side of the basin). The larger the diameter of the water inlet pipes, the slower and less turbulent the flow becomes, giving less resistance. There is a threshold diameter, which we can call D _ah =o, where the difference between the water level in the sea and the raceway is approximately zero when the maximum amount of water the fish needs can be fed into the raceway 4 through the intake pipe 2. This limit is not absolute, but follows the graph in Figure 5 in the sense that the height difference is approximately proportional to power consumption.

The following relationship applies to water velocities in the raceway and intake pipes and outlet pipes: A _Pipe x V _Pipe = A _RW x V _RW . (1)

That is, the volume of water passing through the two surfaces must be the same. A _Pipe are the cross-section of the inlet pipe and the outlet pipe, V _Pipe are the water velocity of the inlet pipe and the outlet pipe, A _RW is the cross-section of the raceway and V _RW is the water velocity of the raceway. The water velocity of the pipes V _Pipe should be sufficiently slow such that friction and turbulence are small. The water velocity V _RW of the raceway should be sufficiently slow such that sedimentation can proceed for a sufficiently long time.

Simulations show that after half an hour in water without significant turbulence, particles of fodder, feces and debris larger than 1 mm will sink to the bottom and settle in the raceway at a water velocity of 0.07 m / s (According to an analysis by SINTEF).

It is important to design the raceways such that the water flows smoothly in one direction. Furthermore, it is better for the oxygen distribution in both the longitudinal and the latitudinal directions that there is a slow homogeneous flow of water in one direction. Calculations (see Fig. 5) show that when water velocities Vp _ipe increase above 0.7 m / s or 1 m / s in the pipes 2, 3 resistance and thus energy consumption start to increase more per unit of water moved and at velocities V _RW above 0.1 m / s in the raceways, the

sedimentation is significantly reduced. Thus, according to the relation (1) above, the cross- section of a raceway 4 should be at least 5-10 times the cross-section of the intake pipes 2. On this basis, we can say that the cross-sectional area of the pipes 2, 3, A _pipe , and the raceway, A _RW must follow the equation: A _Pipe x V _Pipe = A _RW x V _RW . The constraints we have on the velocities are as follows: 1. Pipes <1 m / s so that little return pressure is created in the pipes and 2. V _RW <0.1 m / s so that sedimentation can take place in the raceway.

Furthermore, we have a third limitation: The cross-sectional area of the pipes must be above a threshold value because the water velocities in the pipes is limited. Thus the farmed fish nevertheless get enough oxygen despite limited water velocity.

The cheapest way to meet the oxygen demand of the fish is using the oxygen naturally found in the seawater. Therefore the oxygen demand of the fish and the oxygen content of the seawater controls how much water is needed in a fish raceway. The oxygen need for the fish increases with temperature while the oxygen content of the seawater decreases with increasing temperature. That is, everything must be dimensioned for maximum

temperature. The seawater typically contains between 7 and 12 mg / I in Northern Norway and is highly dependent on the temperature of the sea (15 degrees typically gives 8 mg / I and 0 degrees gives 12 mg / I at 80-100% saturation). Generally, in the industry, it is estimated that large salmon (which consumes the most energy) needs 0.66 tons of seawater per minute per ton of fish (or 660 liters of seawater per minute per 1000 kg of fish). This means that for every ton of farmed fish in the raceway, 0.66 tons of water must be pumped through the pipe every minute. If we disregard some parameters such as friction, etc., we can set up the equation on the basis of relation 1: A _Pipe x V _Pipe x 60s = 0.66 (per tonne of fish). At the same time, if V _Pipe must be below 0.7 m / s and A _Pipe = p/4 x D ² _/ih = o, it gives a threshold diameter, measured in meters:

D _Ah =o = (0.020 x ton _fish ), (2),

where ton _fish is the number of tons of fish in the raceway.

Since the outlet does not necessarily have to be a pipe, it may be smart to express this as a cross-sectional area measured in m ² :

A Ah = 0 = 0.016 x ton _fish (3)

That is, for every ton of fish a maximum channel is intended for, there must be 0.016 m ² in cross-section of the intake pipe and the outlet pipe. This is not an absolute limit in the sense that further increase of the area will result in further savings in energy consumption, but a very large area will give a very high cost of getting the intake pipe down to 15 meters. We believe that (3) provides an optimal balance between cost of construction and power used during operation. If we look at Figure 5, it is clear that the total costs for the construction and operation of intake pipes will have a V-shape with the tip of the V positioned between 3 and 6 meters somewhere (for a fish raceway of 8000 tons). In Figure 5, several parameters such as friction and length of pipe are taken into account. We can see that as cross-sectional area on intake pipes and outlet pipes decreases, energy consumption is increasing faster and faster. There is evidence that the turbulence is increasing and that there is a height difference between water level in the fish farm and the sea outside.

For example, if a raceway according to the invention has 8000 tons of fish, it should have access to at least 8 tons of oxygen per day (consumption of 3-8 kg. oxygen per ton of fish in per day or 2.1 - 5.5 g of oxygen per tons of fish per minute). With the oxygen content in the seawater in Northern Norway at 15 degrees, it provides a desired flow of water of approximately 500 tons of seawater per minute, including safety margins. In order to maintain such a flow and at the same time avoid level differences at the different water surfaces, it is desirable to have a water inlet pipe at least 4 meters in diameter (with reference to Equation 1 and a maximum flow rate in the inlet pipes of 0.7 m / s). At this speed the water is not turbulent and the friction with the walls of the pipes (2, 3) is negligible.

For fish farms in other regions with different oxygen levels and when breeding fish other than salmon with different oxygen consumption, the desired minimum diameter becomes different.

If the oxygen demand were to become critical for a shorter period due to power outages, pump system failure or severe water intake contamination, this could be countered by increasing the speed of the propellers 17 or by means of oxygenation units which are common in the industry.

The partition walls 7 in the raceways 1 are dimensioned to be able to stand when the basin and raceway are dry, but do not have to be dimensioned to withstand the pressure that occurs if two adjacent raceways are full and empty respectively. In one embodiment, large portions of the partition walls of the raceways are a waterproof cloth that is attached to a skeleton.

The location of the basin is important. Ideal location is on a relatively small elongated island with relatively good flow on both sides and with depths over 20 meters in the immediate vicinity. With such a position as shown in FIG. 3, the plant can access two independent current systems, indicated by arrows A and B, which prevent the outlet water from coming into contact with the inlet and the pipe lengths can be relatively short to reduce cost and resistance. In the case of smaller installations or upgraded treatment of the out flow, proximity to the sea with depths above 20 meters will be sufficient. Furthermore, the basin must be positioned such that the sea does not float in the event of storms and there must be opportunities for logistical solutions in the form of access for boat or truck, preferably both. The design of inlet 2 and outlet 3, basin 3 and raceway 4 is also influenced by the tidal difference in the area. With large tidal differences, large variations in fish volume become problematic. The farm according to the invention should work well for up to 6 meters maximum tidal difference. By the terms lowest low tide is meant a level that is somewhat lower than the Lowest Astronomical Low tide (LAT) and does not go below the upper point of the intake and outlet pipes more than at most once a year. By the highest high tide is meant a level which is above the Highest Astronomical High Tide (HAT) and does not exceed the upper edge of the basin more than at most once a year.

The danger of escaping salmon is almost completely eliminated by two effective barriers. First, a barrier in the form of the basin 1 that is blasted into rock or cast in concrete. The only supply of seawater is through inlet and outlet pipes 2, 3. Secondly, an escape barrier 16 in the form of at least one, preferably two grids on inlet and outlet pipes 2, 3.

Preferably, the flow units 17 are large diameter propellers 17 which move slowly such that the flow is as turbulent free as possible.

In one embodiment shown in FIG. 4, sludge collection means comprise a horizontal fish barrier 20 at the bottom of the raceway throughout its length where the fish are located and which prevents the fish from swirling up sedimented feed residues and feces and at least one sludge hoover 21, or sludge extractor, under the fish barrier which sucks up the sedimented sludge and brings it to a sedimentation tank 23 via a sludge pipe 27 where the solids content is further increased, as indicated in Figures 1 and 3. There are many sludge extractors on the market that will work.

The solids content of the sludge collected by the at least one sludge hoover is approx. 1%. Sludge pumps 29 pump the sludge to the sedimentation tank 23. In one embodiment, the sedimentation tank 23 is a circular sedimentation tank where the sludge is fed to the bottom and purified water runs off the top. A typical solids content after treatment in the sedimentation tank will be approx. 10%. After treatment in the tank 23, the sludge is pumped via a depot pipe 28 to a sludge depot 24 where it is stored for further transport or further processing, as shown in Figure 1.

In an alternative embodiment, a portion of a downstream end of the fish raceway is blocked with a separating net 25 as shown in FIG. 4. It will cause less turbulence because the fish does not swim in this area which is not burdened with feces and fodder. Thus, the sedimentation will improve. In addition, the water can be treated without having to pay attention to the fish. For example, coagulants or flocculants may be added.

In another alternative embodiment, the water pumped out from the raceways is discharged into a cleaning basin before it flows into the sea. For example, coagulants or flocculants may be added and the cleaning basin may be provided with sludge collection means of the same type as in the raceways.

It is envisaged that the fish farm should be emptied, washed and disinfected at regular intervals, e.g. once a year. To make this as simple as possible, water inlet pipes and water outlet pipes can be closed with inflatable sealing balloons and the water can then be pumped out with mobile pumps.

One of the major benefits of a fish farm of this type is the ability to purify the water passing through the fish farm. Because the water flows in one direction through the plant in a uniform laminar flow, the opportunities for sedimentation in the raceway are optimal. This is difficult to achieve at sea because of waves and currents affecting floating facilities. The best result of the sedimentation is obtained by using a process comprising the steps described below.

The first step is to feed the fish with feed having coagulants and / or flocculants added.

There are a number of such on the market that have been tested on salmon. Among the most common are guar gum and alginate. These are natural products where guar gum is a linear polysaccharide extracted from Indian cluster beans, while alginate is extracted from brown algae (Brinker et al 2005).

Second step is to provide a smooth flow of water into the raceway 4, where the flow is large enough to provide sufficient oxygen and small enough to allow for sedimentation of residues and feces at the bottom of the raceway. A typical speed in a 100 meter long raceway with a diameter of 14 meters will be about 0.07 m / s. Then, on average, the water will be in the raceway approx half an hour and this gives enough time for a fair amount of the solids to precipitate.

The third step is to continuously remove sedimented sludge from the bottom of the raceway through sludge collection means 12 as previously described.

The fourth step is to pump precipitated sludge removed from the bottom of the raceway to the sedimentation tank, while the fifth step is to pump sludge that has been processed in the sedimentation tank to the sludge depot. For these pumping operations it may be

advantageous to use vacuum pumps because they cause least turbulence at intake.

Alternatively, it is possible to shut off a portion of the raceway closest to the fish outlet by means of a dividing net 25 or alternatively place a cleaning basin after the outlets from the raceways. The separator may be a separator or mesh that prevents the fish from swimming downstream of the separator. There, the water can be treated without having to pay attention to the fish. For example, coagulants or flocculants may be added and sludge collection means of the same type as in the raceways may be added to the cleaning basin.

An added bonus of the fish farm according to the invention is that the increased degree of control of the water the fish swim in allows for a much greater degree of accuracy in measuring parameters that are of interest to fish health and fish farming. This is also on a much larger scale than traditional land-based plants. Furthermore, medication and processing of fish is more controlled and easier compared to net cage operations. It is also relatively easy to scale up the purification of the water from the water outlet pipes because the water come out of pipes and are not mixed with seawater in the first place.

The embodiments shown in the drawings and described above are exemplary only. The invention is defined by the appended claims.

Inventory

1 Basin

2 Water intake pipes

3 Water outlet pipes

4 Raceway

5 Inlet end

6 Outlet end

7 Partition wall

8 Inlet opening

9 Outlet opening

12 Sludge handling means

16 Escape barrier

17 Flow unit

18 Dividing Net

20 Fish barrier

21 Sludge hoover /means for sludge extraction

23 Sedimentation tank

24 Sludge depot

27 Sludge Pipes

28 Depot pipe

29 Sludge pumping means.