Patent Description:
There is a great need for fish as a food source and the fish farming industry in Norway is experiencing a great demand. Therefore, new farming installations and tanks for different locations are being developed. Due to problems with diseases, in particular the problem surrounding salmon lice, a number of "closed" solutions have been developed lately. These are installations for use in the sea and on land, but where the tank walls are closed to prevent ingress of pathogenic organisms.

Also known are so called RAS reactors, i.e. closed Recirculating Aquaculture Systems.

RAS installations are often preferred to open installations at sea because they provide an environment for the fish that can be controlled. However, it is assumed that one manages to clean and control the water in an optimal way and that the solution is economically profitable. An RAS installation is based on standard processes for water treatment that can be illustrated by the following steps:
Disinfected water is taken into the tank to replace the water which is evaporated and removed by filtration and cleaning. The amount of water suppled to the installation is relatively modest (about <NUM>-<NUM>%), as most of the water (about <NUM>-<NUM>%) is recirculated in the installation.

The different processes which the water goes through as a part of the cleaning process are:.

The four mains steps above are often divided into several sub steps. Traditionally, such an installation is produced in that the water is pumped from one treatment unit to another. Thereby this gives installations which are composed of many treatment units spread out over a large area and with many pipe couplings between them. This is costly and the economics is poor when one considers fish farming on a large scale. Such installations often cover <NUM>,<NUM>-<NUM>,<NUM> square meters.

<CIT> describes a farming tank comprised of a central tank and one or more surrounding tanks. The central tank is used for water treatment and the surrounding tanks are used for the farming of fish.

<CIT> describes a farming installation where the fish are in a main chamber where water is transferred for cleaning to chambers inside the main chamber. After the water has been in all three chambers it is led back in pipes to the main chamber.

<CIT> discloses a farming tank according to the preamble of independent claim <NUM>.

Therefore, it is an object of the present invention to develop a more compact system where the different treatment processes can be carried out in units that are integrated into the tank. It is also an object of the invention to provide a system with more optimal water flow and this is particularly important to save energy which is necessary to lift and move the water.

Thus, the present invention relates to a tank for farming of marine organisms comprising the features of independent claim <NUM>.

In one embodiment water is circulated via pipelines to the first ring chamber and where there are openings in the wall of the first ring chamber set up so that the water is circulated back to the main chamber.

In one embodiment the tank is comprised of a second ring chamber along the periphery of, and external with respect to the main chamber and internally for the first ring chamber where the water is circulated from the main chamber via the first ring chamber and thereafter via the second ring chamber and back to the main chamber.

According to the invention, the pipelines are arranged near the centre of the main chamber and are fitted with a pumping device that lifts the water sufficiently high so that the water runs freely in the horizontally inclining section of the pipelines to the first ring chamber.

In one embodiment the pumping device is a propeller pump.

According to the invention, a vacuum pump, such as a fan, is arranged in communication with the pipelines and set up so that a negative pressure is established in the horizontally inclining section.

In one embodiment a negative pressure and venting from the pipeline are established with a cyclone.

In one embodiment water circulates slowly via the pipeline so that the water is exposed to a negative pressure for a long time.

In one embodiment the device encompasses an injector for addition of small gas bubbles, preferably microbubbles and more preferably micro air bubbles, in the fluid that is transported through the pipeline.

In one embodiment in the first ring chamber air supply means for the supply of air, preferably upwards directed air in the first ring chamber, is set up In one embodiment microbubbles are supplied with injectors to the first ring chamber.

In one embodiment the tank also comprises one or more drainage wells arranged peripherally adjoining the upper section of the first ring chamber such that foam is transferred from the first ring chamber to the drainage wells.

In one embodiment said second ring chamber is set up as a bio-filter, preferably in that air is blown into the chamber and gets the water into circulation and that arranged in the water is a number of bodies with a large surface area for nitrification of the water.

In one embodiment the tank is comprised of a third ring chamber peripheral to the main chamber in its upper section and where this third ring chamber is comprised of means for the supply of oxygen and/or air to the water in the ring chamber.

In one embodiment water is circulated from the third ring chamber to the main chamber via overflow systems arranged in the third ring chamber.

In one embodiment the tank is comprised of a main chamber with a water level V1, a first ring chamber with a water level V2 , a second ring chamber with a water level V3 and a third ring chamber with a water level V4 set up so that the water level V1 is the lowest water level and where the water level V2 in the first ring chamber is the highest water level and where respective water levels V3 and V4 are successively lower than V2 but higher than V1.

In one embodiment the first ring chamber is comprised of several nozzles along the circumference of the chamber set up to supply air to the chamber such that the water is circulated and aerated in the chamber.

In one embodiment the first ring chamber has a vertical extension corresponding to the vertical depth of the wall section of the tank.

In one embodiment the second ring chamber has a vertical extension corresponding to the vertical depth of the wall section of the tank.

In one embodiment a pump, preferably a propeller pump, is set up in the pipeline and gets the water in circulation from the main chamber to the first ring chamber.

In one embodiment means are arranged in the second ring chamber to blow air up along the wall in the second ring chamber so that the water is made to circulate vertically in the second ring chamber.

In one embodiment the bottom of the main chamber inclines and has a well in the centre for the collection of dead marine organisms and waste.

In one embodiment the outer wall of the main chamber is insulated.

In one embodiment a roof is arranged over the tank and said roof is dimensioned for lifting and anchoring of the walls between the ring chambers and between the ring chambers and the main chamber.

In one embodiment the first ring chamber is divided into several part chambers, either by horizontal or vertical wall sections.

In one embodiment such different water treatment methods are carried out in the different part chambers.

Preferred embodiments of the invention shall be described in the following in more detail with reference to the enclosed figures, where:.

<FIG> shows schematically an embodiment of a farming tank <NUM> according to the invention. The tank <NUM> is fitted with a number of walls 10a and a bottom 10b that form a main chamber <NUM> for farming of marine organisms such as fish. These wall and bottom sections can have any suitable form, but the walls 10a are often approximately vertical and the bottom section 10b is often horizontal. The bottom section can also be tapered so that it is somewhat deeper towards the centre of the tank, or it can have a section that tilts towards the centre of the tank.

The farming tank <NUM> that is shown in <FIG> is closed, i.e. the wall and bottom sections are impenetrable to water. The tank <NUM> can be arranged to float in the water or the sea and is then equipped with a float collar (not shown in the figure) to ensure sufficient buoyancy of the tank. However, preferred embodiments of the tank are used on land and are then arranged in a frame or that the tank <NUM> is sufficiently rigid so that it can be placed on land.

As large amounts of water must be treated continuously and since the water must be subjected to several different water treatment processes, units with considerable water chambers are required to carry out the different processes. With today's solutions water is transported out of the tank or the chamber and the different water treatment steps are often carried out in separate modules or processes.

With the present invention a solution is provided where different water chambers are placed in the outer circumference of the chamber/tank. As it is often preferred to use circular tanks or chambers, these water treatment chambers are set up as annular spaces in the outer periphery of the tank. The annular spaces are given an extension and volume adapted to the amount of water that shall be treated and shall be circulated back to the main chamber of the tank.

<FIG> shows a tank <NUM> with a first ring chamber <NUM>. It is preferred that the ring chamber <NUM> uses the whole or most of the vertical extension of the tank <NUM>. The tank <NUM> can be fitted with several such ring chambers and we therefore designate the outermost ring chamber <NUM> (the only ring chamber in <FIG>) as the first ring chamber <NUM>. The first ring chamber <NUM> can, in principle, be set up with a dividing wall which is set into a tank or a vessel or it can be one unit which is set up at the outside of the tank.

<FIG> also shows pipelines <NUM> to circulate water from the main chamber <NUM> to the first ring chamber <NUM>. Of course, there can be several such pipelines <NUM> to circulate water to the first ring chamber <NUM>. The pipelines <NUM> have a vertical section that extend from above the water level V1 in the main chamber <NUM> and down into the water in the main chamber <NUM> and in the main horizontally but a part 16a tilts and freely leads the water that is lifted up from the main chamber <NUM> out towards the first ring chamber <NUM>. The water inlet for the pipeline <NUM> is arranged near the centre of the tank <NUM> to ensure that the water, after it has been lifted mainly vertically up, is transported a long distance before it is sent into the first ring chamber <NUM>. For a tank with a diameter of <NUM> metres, the water can be transported much further than <NUM> metres with this solution before it is poured into the ring chamber <NUM>.

In an embodiment which does not form part of the invention, water is circulated from the main chamber <NUM> to a different location in the main chamber <NUM>. It is preferred that water is moved in this way from centrally in the main chamber <NUM> to a point nearer the outer part of the main chamber <NUM>. This point is preferably near, and external with respect to the ring chamber <NUM> as given in <FIG>.

A pumping device <NUM> to pump up the water from the main chamber <NUM> is arranged in the pipeline <NUM>. It is preferred that this is a propeller pump <NUM> which is well suited to pumping of large amounts of water at a low pressure.

With the help of an injector <NUM> placed in the pipeline16, which adds small air bubbles in the water, CO<NUM> will go from the water and into the air bubbles. Here, there is a relatively high level of CO<NUM> and low level of O<NUM>. There is then a mixture of water and small air bubbles in the pipeline section 16a and CO<NUM> goes from the water and into the air bubbles due to the equilibrium principle.

To generate a negative pressure in the pipeline section 16a, and also to get rid of the air bubbles which have, at this stage, a high level of CO<NUM>, a fan <NUM> (shown in <FIG>) will be installed which generates a negative pressure and which pulls the air bubbles out from the water. Because of the negative pressure and a large surface between the air bubbles and water this method will efficiently remove CO<NUM> from the water.

This will remove unwanted CO<NUM> from the water during the passage from the main chamber <NUM> to the first ring chamber <NUM>. It is preferred that the water moves so slowly that the water is exposed to a negative pressure over a long time and thus a good removal of CO<NUM> will be obtained.

This is the core of the present invention, i.e. that large isolated bodies of water can be established (as the first ring chamber <NUM>) as an integrated part of the tank <NUM>, and where the water which is lifted up from the main chamber <NUM> is horizontally moved slowly under a negative pressure to further water treatment processes that can be carried out in ring chamber <NUM>.

As given in <FIG>, openings <NUM> are arranged in the first ring chamber <NUM> so that the water is circulated back to the main chamber <NUM>. In the figure, these are shown at the bottom in the wall between the main chamber <NUM> and the first ring chamber <NUM>, but they can also be placed higher up on the wall. To obtain the required circulation, the openings <NUM> are preferably arranged in the bottom section of the first ring chamber <NUM>. Furthermore, one has arranged in the first ring chamber <NUM> means (not shown in the figures) for the supply of gases or air, in addition to what has been supplied to the pipeline <NUM>, as given above. These ensure that air is supplied to the first ring chamber <NUM> and preferably flows upwards in the first ring chamber <NUM>, i.e. counter current to the direction of the water. The air supply means ensure that the water in the ring chamber <NUM> is set in a circular motion and foam can be removed (explained in more detail below).

As given above a series of water treatment processes must be carried out before the water can be recirculated back to the main chamber <NUM>. Therefore, it is often preferred to have more than one ring chamber arranged peripherally outside of the main chamber <NUM>.

<FIG> shows embodiments where several ring chambers are arranged so that different water treatment methods can be carried out in the different ring chambers. However, in one embodiment of the invention the first ring chamber <NUM> is split into several part chambers so that the water circulates from one part chamber and over into the next part chamber. For example, ring chamber <NUM> can be divided by vertical walls so that the water circulates circularly from one part chamber and over into the next part chamber. One can also imagine solutions where the part chambers are below each other, separated by horizontal wall sections. Either one has a horizontal division or a vertical division of the ring chamber <NUM> into several part chambers, one can, for example, carry out skimming in a first part chamber, biofiltration in a second part chamber and oxygenation in a third part chamber, before the water is led back to the main chamber <NUM>.

In <FIG> a presently preferred embodiment of the invention is shown. A tank <NUM> is fitted with several ring chambers <NUM>,<NUM>. Arranged inside the first ring chamber <NUM> is a second ring chamber <NUM> and water is led from the first ring chamber <NUM> via this second ring chamber <NUM> to the main chamber <NUM>, preferably via overflow. Thereby, one gets a possibility to place further water treatment steps in the solution and in the embodiment shown in <FIG> a first ring chamber <NUM> is used for aeration and skimming (as explained above) and the second ring chamber <NUM> is used for biofiltration.

For biofiltration, small plastic particles with a large surface area are normally used whereupon a biofilm with bacteria that convert ammonia to nitrate (conventional nitrification) is formed.

In <FIG> a drainage well <NUM> is also shown bordering on to the upper section of the first ring chamber <NUM>, for transfer of foam (skimming) i.e. removal of foam and polluting particles from the water.

<FIG> also shows a third ring chamber <NUM> which is used for oxygenating the water. CO<NUM> that is produced by the biofilter in the second ring chamber <NUM> is also removed here before the water enters the main chamber <NUM>. The third ring chamber is, in the embodiment in <FIG>, placed such that water flows from the second ring chamber <NUM> via overflow to the third ring chamber <NUM>. Openings 44a are arranged in a third ring chamber <NUM>, preferably in the bottom section of the ring chamber <NUM> such that water flows from the third ring chamber to the main chamber <NUM>. Oxygen and/or air is supplied to the water in the third ring chamber <NUM> at the same time as CO<NUM> is removed with the help of additions of small air bubbles in the water.

The flow of water is indicated with arrows in the figures, i.e. water is led from the main chamber <NUM> via the pipeline <NUM> to the first ring chamber <NUM>, and then vertically down and through the openings <NUM> in the bottom section of the second ring chamber <NUM>. Air is supplied in the second ring chamber <NUM> to establish a vertical circular movement of the water in the ring chamber <NUM> before it flows on via overflow to the third ring chamber <NUM> and thereafter via openings in the bottom section in the third ring chamber <NUM> to the main chamber <NUM>. In this circular flow movement, water passes through different water treatment processes arranged in different ring chambers <NUM>,<NUM>,<NUM> externally to the main chamber <NUM>.

The different ring chambers <NUM>,<NUM>,<NUM> can have any possible shape and size. However, to obtain a compact installation <NUM> it is preferred that one or more of the ring chambers have a vertical extension corresponding to the vertical extension of the tank <NUM>.

<FIG> shows schematically in section a detail of the main chamber <NUM>, the first ring chamber <NUM>, second ring chamber <NUM> and a third ring chamber <NUM> and also the different water levels that are established. The water level in the main chamber <NUM> is given as V1 and is the lowest water level. The water level in the first ring chamber <NUM>, given as V2 is the highest water level. In between, the other ring chambers have successively lower water levels so that the second ring chamber <NUM> has a water level V3 which is lower than V2, but higher than the water level V4 for the third ring chamber <NUM>. Therefore, the water is forced to flow from the first ring chamber <NUM>, via the second ring chamber <NUM> via the third ring chamber <NUM> and to the main chamber <NUM>.

In a preferred embodiment the tank <NUM> is fitted with a roof. Furthermore, the outer walls of the tank are preferably insulated, and the roof is also insulated. The walls between the different ring chambers, and the wall between the main chamber and the ring chamber is preferably made from thin plastic plates or tarpaulin, and structurally fastened to the roof at several points.

If the tank/vessel is for placing on land, it is preferably manufactured from steel, concrete or plastic and covered internally by plastic.

Claim 1:
Tank (<NUM>) for farming of marine organisms, the tank (<NUM>) comprising a main chamber (<NUM>) to hold the marine organisms, wherein the tank also comprises a first ring chamber (<NUM>) arranged at the periphery of the main chamber (<NUM>) and wherein water from the main chamber (<NUM>) is circulated via pipelines (<NUM>) to the first ring chamber, characterised in that the pipelines (<NUM>) are arranged near the centre of the main chamber (<NUM>) and are fitted with a pumping device (<NUM>) that lifts the water sufficiently high up so that the water flows freely in a horizontally tilted section (16a) of the pipelines (<NUM>) to the first ring chamber (<NUM>), and in that a vacuum pump (<NUM>), such as a fan (<NUM>), is arranged in communication with the pipelines (<NUM>) and set up so that a negative pressure is established in the horizontally tilted section (16a) of the pipelines.