Patent Description:
Land based Recirculated Aquaculture Systems (RAS) are known and varieties exist and as an example, Moore discloses a fish growing tank and method in the patent literature <CIT>.

Cleansing systems are also known and an integrated closed loop system for water purification is known from the patent literature e.g. <CIT>.

Document <CIT> discloses a fish husbandry system having a fish rearing vertically extending tank wherein the water flows in substantially laminar fashion from bottom to top.

Document <CIT> discloses a process and means for processing water used in a land based farming installation. The document describes a continuously circulating process of water through different cleaning stages, by means of a cleansing system comprising an inlet to inlet aqueous medium into a first volume surrounded by an annulus section having a second volume in communication with the first volume, the annulus section further comprising an outlet to outlet cleaned aqueous medium.

Document <CIT> discloses a wastewater treatment system with a centralized tank and a peripheral aeration zone divided into three sectors: aeration tank, activated sludge regeneration and aerobic mineralizer.

Finally, document <CIT> discloses a land based water recirculating system with different treatment phases: mechanical filtration, aerobic treatment, anaerobic/ anoxic treatment, and optimally ozonation and optionally protein skimming.

Different parts or sub-systems have generally been interconnected and handled separately.

It is an object of the invention to improve the cleansing systems of aquaculture system.

It is an object of the invention to improve a recirculation aquaculture system (RAS). Although circular systems exist, further improvements are needed to save space.

The objects above are achieved according to the invention by a cleansing system comprising the features of independent claim <NUM>, a method for cleansing an aqueous medium comprising the features of independent claim <NUM>, and a recirculating aquaculture system comprising the features of independent claim <NUM>.

A cleansing system configured to receive aqueous medium from at least one fish tank and to return a cleaned aqueous medium to the at least one fish tank, comprises a cleansing system inlet arranged at a cleansing system inlet level to inlet the aqueous medium into a first volume. The first volume is substantially surrounded by an annulus section having at second volume. The first volume and the second volume are in communication via at least a first-second-overflow leveller arranged at first-second overflow leveller level and to radially overflow the aqueous medium from the first volume to the second volume. There is a cleansing system outlet arranged in the annulus section configured to outletting the now cleaned aqueous medium from the annulus section.

This particular configuration allows for an effective distribution of an aqueous medium such as water, say in an aquaculture system, through different volumes that can be configured according to specific purposes as will be described herein.

According to the invention, the annulus section is parted in arc-sections forming at least a further third volume in the annulus section, where first volume and the third volume are in communication via at least a first-third-overflow leveller arranged at a first-third overflow leveller level and to radially overflow the aqueous medium from the first volume to the third volume.

This particular configuration allows for an effective distribution of the medium into at least three different process volumes. It further allows for the medium to be processed in parallel in the second and third volume. The arc-sections may be designed according to a certain ratio. The arc-sections may be adjustable.

A person skilled in the art will appreciate the generic concept and will be able to configure the described volumes, the first volume, the second, and the third volume according to circumstances. Preferably, the first volume is configured with a specific purpose as first reactor, e.g. as a moving bed type of configuration, the second volume is configured with a specific purpose as a second reactor, e.g. as a fixed bed type of configuration, the third volume is configured with a specific purpose as a degassing section.

According to the invention, the second volume and the third volume are in communication via at least a second-third-overflow leveller arranged at second-third overflow leveller level and to tangentially overflow the aqueous medium from the third volume to the second volume.

This further allows for mixing the medium from third volume with the medium in the second volume. This configuration saves space and energy since the arc-sections may be designed or adjusted and the tangential flow may be controlled. Thereby, a three-stage process may be implemented and the medium may simply cascade through the volumes. The volumes may be configured to optimise the desired process. The actual flow rate and/or flow ratio may easily be controlled or adjusted to achieve the desired overall process, such as cleaning a contaminated aqueous medium.

Preferably, the annulus section is parted in arc-sections forming at least a further fourth volume in the annulus section, where first volume and the fourth volume are in communication via at least a first-fourth-overflow leveller arranged at a first-fourth overflow leveller level and to radially overflow the aqueous medium from the first volume to the fourth volume.

Preferably, the third volume and the fourth volume are in communication via at least a third-fourth-overflow leveller arranged at third-fourth overflow leveller level and to tangentially overflow the aqueous medium from the fourth volume to the third volume.

Preferably, the fourth volume comprises return flow means for returning the aqueous medium from the fourth volume to the first volume as a return flow. The return flow means may be an arrangement with one or more pumps. The pumps may be configured or controlled to ensure a certain level in the volume or a certain exchange to and from the volume.

There may be tangential flow means for exchanging the medium between the fourth and a third volume. The tangential flow means may be one or more arrangements of pumps.

Preferably, at least one first or second volume may be configured to biologically filtering of the aqueous medium. The other first or second volume may be configured to degassing the aqueous medium.

Preferably, the at least one first or second volume is configured with means for nitrification of the aqueous medium.

Preferably, the annulus section comprises at least one volume for nitrification and another volume for de-nitrification.

Preferably, the first volume is configured to biologically filtering of the aqueous medium by a moving bed system. The second volume is configured to degassing the aqueous medium. The third volume is configured to biologically filtering the aqueous medium by a fixed bed system.

Preferably, the one or more volumes may be configured as follows.

At least one first volume may be configured to for nitrification of the aqueous medium. At least one second volume may be configured for degassing the aqueous medium. At least one third volume may be configured for nitrification of the aqueous medium. At least one fourth volume is configured for de-nitrification of the aqueous medium.

This configuration may allow for de-nitrification. Whilst additional carbon provided for de-nitrification may degenerate the medium, if returned to a fish tank, and result in increased algae production, this particular configuration enables the aqueous medium to be returned to a volume configured for nitrification. The nitrification volume may be the first volume, the third volume or both. The additional carbon may then be consumed by bacteria in one of the nitrification volumes. The first, centre, volume may be a moving bed type and consume carbon at a relatively high level. The third, annulus, volume may be a fixed bed type and consume carbon at a relatively low level. A person skilled in the art will appreciate the option to balance the levels of carbon consumption. In particular a person skilled in the art will appreciate the option and the ease to install pumps to adjust the levels or the flows between volumes configured for de-nitrification and volumes configured for nitrification.

Preferably, the cleansing system may be configured so that the fourth volume is arranged adjacent to at least one third volume and wherein the least one third volume and the fourth volume are in communication via at least a third-fourth-overflow leveller arranged at third-fourth overflow leveller level and to tangentially overflow the aqueous medium from the fourth volume to the least one third volume.

Preferably, the first volume may be configured as a moving bed type of reactor; the second volume may be configured for degassing the aqueous medium. The second volume may be sandwiched between two third volumes each configured as a fixed bed type of reactor. The fourth volume may be between the two third volumes and configured for de-nitrification of the aqueous medium.

This configuration will allow one third volume to be cleaned or maintained whilst the other third volume is in operation or use; and vice versa. In example, the third volumes may be configured for nitrification. The configuration enables a "mirror-like" system and as seen and further disclosed in the detailed section, the suggested means allows for easy cleaning of the third volume.

Having only one degassing volume saves some piping. In an aspect, there may be pipes or outlets arranged at the two ends of degassing section, which outlets return the degassed aqueous medium to respective fish tanks.

A person skilled in the art may want to make use of the configurations suggested. In an aspect the first volume, the centre volume, may be configured for de-nitrification. The fourth volume may then be configured for nitrification.

An object is achieved by a method for cleansing an aqueous medium from an aquaculture system in a cleansing system, the method comprising the steps of independent claim <NUM>.

An object is achieved by a recirculating aquaculture system, the system comprising a cleansing system as disclosed herein and comprising at the least one fish tank and arranged so that the water is recirculated between the at least one fish tank and the cleansing system, according to independent claim <NUM>.

Preferably, each of the least one fish tanks has a fish tank outlet in communication with the cleansing system inlet and where the cleansing system inlet level is at a gravitational level that is lower than a fish tank outlet level of each of the least one fish tanks; and which cleansing system outlet is in communication with a flow-setter in each of the least one fish tanks; wherein there is a pump in the communication between the cleansing system and the least one fish tanks.

Disclosed here below is a method for cleansing an aqueous medium from an aquaculture system in a cleansing system. The method may comprise the following acts.

There may be an act of providing the aqueous medium to a cleansing system inlet in the cleansing system.

There may be a following act of mechanical filtering of the aqueous medium in a mechanical screen filter.

There may be a following act of biologically filtering the aqueous medium in a first reactor section.

There may be a following act of parting the aqueous medium into a second reactor and a degassing section.

In the degassing section and the second reactor there may be acts performed in parallel.

There may be an act of degassing the aqueous medium in the degassing section. There may be an act overflowing of the aqueous medium from the second reactor into the degassing section.

From the degassing section there may be an act of outletting the now cleaned aqueous medium through a cleansing system outlet.

There may be an act of pumping the aqueous medium.

It is understood that a reactor or section is a chamber or volume in which the aqueous medium or water can be and in which a reaction or process can take place. Each reactor or section may be a chamber or volume. Thus, the first reactor may be a first volume in which a first reaction may be performed. The second reactor may be a second volume in which a second reaction may be performed. In a very special embodiment a volume or a reactor may be used simply as storage or a buffer without any further purpose.

It is understood that the aqueous medium from the fish tank is contaminated with at least carbon dioxide and nitrogenous products. The medium may also contain biological organic waste products, e.g. faeces, particulate matter, i.e. smaller or larger physical objects. In general, the aqueous medium may be waste water from an aquaculture system, a fish farming system including fish farming of salmon or the like.

It is achieved that the contaminated aqueous medium is cleaned and degassed and sufficiently prepared for recirculation. The contaminated aqueous medium may be contaminated from an aquaculture tank and may have to be returned or recirculated into the aquaculture tank. The process performs this in a particular effective way that saves process steps and thus, resources to provide or enable the process steps. In particular the process provides an integrated process that results in e.g. sufficient cleaning, including mechanical cleaning, and biological cleaning, say nitrification, as well as degassing.

The process is further advantageous since the process allows for, either as per design or during operation, to adjust the partition of the medium between the second reactor process and the degassing process.

In example the first reactor may perform nitrification and the overflow to the second reactor and degassing may be adjusted by changing the volume, either the diameter or the level of barriers between sections. The activity or recirculation in the moving bed character may also be adjusted. Thereby, the nitrification level may be controlled before overflowing the medium to the second reactor and the degassing section.

The first reactor or volume may be a moving bed type of reactor. The first reactor may be configured with aeriation means such as airlifts to generate mixing flows according to design or practice.

The first reactor may be configured to sustain bio-elements or -carriers in the medium in the first reactor by being configured with means sealing off such bio-element from the first reactor from the annulus ring or arc-sections. There may be perforated walls, grids or other barriers restraining the bio-elements whilst allowing the aqueous medium to flow.

The second reactor may be used to filter or clean a certain part of the medium before overflowing into degassing. The second reactor may involve further nitrification, removal or containment of finer particles. The filtering may be biological or mechanical. In an aspect use of bio-elements suspended in the medium will harvest particles and products by a growth process whereby the medium is cleaned or filtered.

The second reactor may be optional and the second reactor may also be a pass-through (buffer-type) of volume. Optionally, there may be a mechanical filter.

The second reactor or volume may be a fixed bed type of reactor. The second reactor or volume may be a moving bed type of reactor. Likewise, the second reactor or volume may be configured to sustain bio-carriers in the second reactor. There may be a perforated barrier such as top deck that allows the aqueous medium to flow through in an upward direction whilst restraining bio-carriers.

The degassing may involve injecting air into the medium. The medium may, from the overflow from the first and second reactors be broken into smaller drops, droplets by overflowing a perforated plate or through crown nozzles. There is an effective cascading of the medium (downward by gravitation) that meet with a counter flow or counter directed stream of say air or oxygen enriched (upward) stream.

There may be volume of the aqueous medium that is still and from which degassing (of CO2 and N2) takes place so that the degassing leaves the medium and is removed upwardly.

In one embodiment, the percentage of the aqueous medium during the act of parting into the second reactor and the degassing section may be adjusted either before or after the construction of cleansing system. A person skilled in the art would know the right percentages to obtain optimal condition.

Parting the aqueous medium may be performed in a substantially radially directed outward flow from the first reactor section into arc-sections of a surrounding annulus section. The arc-sections include at least the second reactor and the degassing section.

The second reactor receives part of the aqueous medium. The degassing section receives part of the aqueous medium. The second reactor and the degassing section may divide the aqueous medium.

The arc-sections in the annulus section may be adjusted to adjust the division or parting of the aqueous medium from the first section.

The act of overflowing of the aqueous medium may be performed in a substantially tangentially directed flow at arc-section dividers from the second reactor and the degassing section.

Thereby, the flow is controlled since the arc-section divider works or can be modified to adjust the flow and the nature of the flow into the degassing section.

Different types of perforations, holes, tubes, pipes may be applied. Furthermore, there may be valve or blinds that can adjust the flow, the level or close the flow.

The act of providing the aqueous medium to an inlet in the cleansing system may be performed at a gravitational level that is above the act of parting the aqueous medium into the second reactor and the degassing section.

Below the act of parting the act of overflowing of the aqueous medium from the second section into the degassing section is performed.

Below the act of overflowing there is the act of outletting the aqueous medium.

Thus, the aqueous medium cascades from a centre inlet and is distributed radially in the first reactor and cascades radially outward over levellers or edges into respective second reactor(s) and degassing section(s). The second reactor and the degassing section being configured with a leveller or edge in between so that the aqueous medium cascades from the second reactor to the degassing section. Finally, the aqueous medium is outlet from a lower most or bottom part of the degassing section.

Thereby the aqueous medium is effectively cleaned. That is mechanically and/or biologically. That includes cleaned for particulates (that is objects, biological matter or collections of biological matter). The cleaning includes to be degassed. The cleaning is achieved with reduced energy or pumping equipment than hereto. Furthermore, the arrangement results in optimisation of space and thus reduces the need of construction materials as well piping.

Disclosed here below is a cleansing system configured to receive aqueous medium from at least one fish tank and to return a cleaned aqueous medium to the at least on fish tank.

The cleansing system may comprise a cleansing system inlet centrally located in the cleansing system. The inlet is in communication with a mechanical filter configured to mechanical filtering of the aqueous medium. The inlet is arranged above and substantially surrounded by a first reactor section configured to biological filtration of the aqueous medium. The first reactor is substantially surrounded by an annulus section.

The annulus section is parted in arc-sections of at least a second reactor; and a degassing section configured to degassing the aqueous medium.

There is a cleansing system outlet configured to outletting the now cleaned aqueous medium from the annulus section. The cleansing system outlet is from the degassing section.

In one embodiment, there may be one or more mechanical filter(s). Thereby, the aqueous medium is filtered before entering the first reactor and larger particles are discarded. The mechanical filter may be a drum screen type of filter.

In one embodiment there may be one or more degassing systems.

An effect of the degassing system may be to decrease the amount of or remove CO<NUM>. Thereby, the quality of the aqueous medium is maintained to secure optimal condition in the fish tank.

Another effect of the degassing system may be to decrease the amount of or remove Nitrogen from the aqueous medium. If atmospheric air is pumped into the system from below, the air may be saturated with Nitrogen. If the amount of Nitrogen is not decreased and the aqueous medium is later used in a fish tank it may cause decompression sickness systems for the fish.

In an embodiment, the cleansing system may have a flushing outlet. The effect of the flushing outlet is to remove part of or the whole aqueous medium from the cleansing system. This may be helpful to do as colonies of small particles may build up in the system.

Furthermore, the accumulation of organic materials and other wastes materials is kept to a minimum. Fouling is thus reduced.

Overall the method and system disclosed will lower the energy consumption otherwise needed. The cleansing system or method will only need or have to "lift" the water once to clean the water in four processes, where big particles are cleaned by a drum filter, nitrification is performed in the first section, such as a moving bed section, degassing (incl. CO2, N2) is performed in a degassing section, and small particles may be cleaned in a second section such as a fixed bed filtration. The water flows or cascades via gravitation between the four cleaning processes.

A further advantage of the system or method is that all sections or volumes will experience a continuous flow of water, which reduces or eliminates dead zones or stagnant water. Thereby further reducing or eliminating the need for piping to reduce creation or contamination with Sulphur.

Hence, the need for piping and space is reduced or eliminated. Also the need of pumps and space and energy for such pumps are reduced or eliminated.

Thus, all the cleaning of the water in "one-step" and water can be re-circulated to get an improved or optimal water quality for the fish breading.

Hence, water of the required purity and with acceptable concentrations (e.g. of CO2) can be recirculated thus allowing for aquaculture whilst reducing environmental impact.

A second reactor may be configured with an overflow leveller arranged at a gravitational level that is above the gravitational level in the degassing section for overflowing of the aqueous medium from the second reactor into the degassing section.

The annulus section may comprise a pair of second reactors and a pair of degassing sections; which pairs separate each other.

The parting may be performed into a pair of opposite second reactors and a pair of opposite degassing sections. The act of overflowing is performed at tangentially directed and oppositely directed flows at annulus dividers from the second reactors into the degassing sections.

The degassing section may comprise a cross-flow or counter-flow applicator arrangement of air arranged below crown nozzles for cascading the aqueous medium onto an upper part of the cross-flow or counter flow applicator arrangement. There may be air communicators arranged to guide air to a lower part of the cross-flow or counter flow applicator arrangement.

Thereby is provided as large a surface contact between air and the aqueous medium as possible. The cross-flow applicators may be arrangements of plates that are bent and having as large a surface as possible. The plates may be coated with anti-fouling coatings. The plates or arrangements may be suspended in the degassing section and air may be directed to the bottom of the plates or channels formed, whereas the medium drizzles or cascades down to the top of the plates or channels formed.

The aqueous medium may drizzle down and experiences a free fall of say <NUM> to <NUM> meters to form small droplets. Crown nozzles may be used to initiate the droplets or cascade process.

The second reactor may comprise a deck arranged to cover the second reactor and configured with deck perforations for an up-ward penetration of the aqueous medium.

The deck may withhold bio-carriers or particular matter. Furthermore, the deck perforation may be altered or distributed to generate or balance pressure differentials so as to provide an even water level in the tangential level, thereby ensuring the overall flow performance or characteristics.

In particular, there may be differential pressure at edge or at the leveller between the second reactor and the degassing section. The pressure differential may be countered by having larger perforations towards the leveller.

The first reactor section may comprise transverse plates substantially arranged in vertically and in parallel.

Thereby, enabling or providing a substantial vertical flow-pattern between the plates and thereby, a desired or complete suspension of bio-elements during operation. There may be aeration or an air lift in every other chamber, section or volume between two plates.

The annulus section may be formed by prefabricated plates/arc-sections, such as metal plates or glass-fibre plates and configured for receiving the first reactor section inserted substantially in the centre.

The foundation or base may be concrete or a plate. Using metal plates, glass-fibre plates or the like will greatly reduce the use of materials and the like. Using plates, such as pre-fabricated elements will also reduce maintenance costs and efforts and allow for adjustments.

The mentioned elements may also easily be modified to balance the overall flow characteristics of the system.

Disclosed here below is a recirculating aquaculture system (RAS), the system comprising a cleansing system and at least one fish tank, wherein the water is recirculated between the least one fish tank and the cleansing system.

In one embodiment, the RAS system may have one or more buffer tanks. One effect of a buffer tank may be to maintain suitable conditions for optimal function in both the cleansing system and the fish tank. The buffer tank may be a buffer to maintain temperature. The buffer tank is further advantageous during fish outtake since it allows to maintain the state of the aqueous medium.

In one embodiment, the fish tank may be intended for salmons or other sensitive species. To breed salmons, the water temperature should be stable around <NUM> and the level of CO<NUM> should be lower than <NUM>/L. Therefore, it may be important to have an affective cleansing system, and a buffer tank.

In one embodiment, there may be a motor/a pump for recirculating the aqueous medium in the RAS system. The motor/pump may be placed after the cleaning system outlet. Thereby, the motor is located after the aqueous medium is cleansed. This may help to keep the maintenance at a minimum and the lifespan at a maximum.

In one embodiment, there may be walls between the fish tank and the cleansing system. Thereby, the fish are shielded of any possible noise from the cleansing system and the stress levels of the fish may be reduced.

Each of least one fish tanks may have a fish tank outlet in communication with the cleansing system inlet which cleansing system inlet is at a gravitational level that is lower than a fish tank outlet leveller of each of the least one fish tank. The cleansing system outlet is in communication with a flow-setter in each of the least one fish tanks. There is a pump in the communication between the cleansing system and the least one fish tanks.

The cleansing system may be as outlined in this disclosure.

The fish tank may have a fish tank wall that is cylindrical with the fish tank outlet coaxially arranged; and wherein the flow-setter is arranged and extends upwards at the fish tank wall and has flow-setter perforations in the upward direction.

In one embodiment, the fish tank may be cone-shaped towards the bottom of the tank.

The cleansing system may thus be driven by gravitation, since the inlet is at a highest level, below which the level of the overflow from the central first reactor into the annulus section is arranged. There may be a level from the first reactor into the second reactor. There may be the same level or another (lower) level from the first reactor into the degassing section. With the arc-sections there may be a level between the second reactor into the degassing section. The levels may be adjusted or configured to be adjusted so as they generate a flow through the cleansing system in accordance with the necessary levels of cleaning, including nitrification and degassing of CO2.

In combination with one or more fish tanks, the level of the input level in the cleansing tank may be arranged below the level of the output of the (dirty) aqueous water from the one or more fish tanks. Thereby, only one pump may drive the flow. The pump may be placed just after the output from the cleansing system thereby experiencing the cleanest possible medium. At the same time, the pump may provide the required pressure to one or more flow setters in one or more fish tanks.

Embodiments of the invention will be described in the figures, whereon:.

<FIG> illustrates a method <NUM> for cleansing an aqueous medium (not shown) from an aquaculture system (not shown) in a cleansing system (not shown).

The method <NUM> comprises the acts of providing <NUM> the aqueous medium to a cleansing system. Next followed by an act of mechanical filtering <NUM> of the aqueous medium.

Afterwards followed by an act of biologically filtering <NUM> of the aqueous medium.

Next followed by an act of parting <NUM> the aqueous medium into a second reactor (not shown) and a degassing section (not shown). In the second reactor there is an act of overflowing <NUM> of the aqueous medium from the second reactor into the degassing section. In the degassing section there is an act of degassing <NUM> the aqueous medium.

In the degassing section there is an act of outletting <NUM> the now cleaned aqueous medium through an cleansing system outlet (not shown).

<FIG> illustrates a perspective view of the cleansing system <NUM>.

The cleansing system <NUM> has a mechanical filter <NUM> intended for mechanically filtering <NUM> the aqueous medium <NUM> (not shown).

The mechanical filter <NUM> is surrounded by a first reactor section <NUM>.

The first reactor section <NUM> (or volume/chamber) is intended for biological filtration <NUM> of the aqueous medium <NUM>.

The first reactor has transverse plates <NUM> arranged vertically and in parallel.

The first reactor section <NUM> is surrounded by an annulus section <NUM>. The annulus section <NUM> comprises two arc-sections <NUM>.

The parting <NUM> of the aqueous medium <NUM> is performed in a substantially radially directed <NUM> outward flow from the first reactor section <NUM> into arc-sections <NUM>.

The flow from the first reactor section <NUM> into the arc-sections <NUM> is enabled (or adjusted) by levels of or perforations in a wall between the first reactor section <NUM> and the arc-sections <NUM>.

The levels of or perforations/holes may form the degassing inlet <NUM> as illustrated. In this embodiment there is a second reactor inlet pipe <NUM> connecting the first reactor <NUM> with the second reactor <NUM>. There are valves on each inlet pipe <NUM> to adjust the level and flow.

Each arc-sections <NUM> include a second reactor <NUM> (or volume/chamber) and a degassing section <NUM> (volume/chamber). Thereby, the annulus section <NUM> comprises a pair <NUM> of second reactors <NUM> and a pair <NUM> of degassing sections <NUM>.

The arc-sections <NUM> are divided by arc-section dividers <NUM>.

There is an overflowing <NUM> of the aqueous medium <NUM>. The overflowing <NUM> is performed in a substantially tangentially directed <NUM> flow at arc-section dividers <NUM> from the second reactor <NUM> and into the degassing section <NUM>.

The second reactor <NUM> has an overflow leveller <NUM> arranged at a gravitational level that is above the gravitational level in the degassing section <NUM>. The overflow leveller is intended for overflowing <NUM> of the aqueous medium <NUM> from the second reactor <NUM> into the degassing section <NUM>.

The second reactor <NUM> has a flushing outlet <NUM> intended for emptying the cleansing system <NUM> for the aqueous medium <NUM> during maintenance and cleaning.

The degassing section <NUM> has a cleansing system outlet <NUM> intended for providing cleansed aqueous medium <NUM> to a fish tank <NUM> (not shown).

The degassing section <NUM> has a degassing section deck <NUM>. The degassing section top deck <NUM> is perforated.

<FIG> illustrates a perspective view of a cleansing system <NUM> and the interior of a second reactor <NUM> and a degassing section <NUM>.

The second reactor <NUM> is an up-flow second reactor. The aqueous medium <NUM> (not shown) enter the second reactor <NUM> through four second reactor inlet pipe <NUM> near the lower part of the second reactor <NUM>.

The second reactor comprises a deck <NUM>. The deck <NUM> is located near the top of the second reactor <NUM> and covers the second reactor <NUM>. The second reactor deck has deck perforations <NUM>.

The degassing section has crown nozzles <NUM> and a counter-flow applicator arrangement <NUM> arranged below crown nozzles <NUM>. The crown nozzles are intended for cascading the aqueous medium <NUM> onto an upper part of the counter flow applicator arrangement <NUM>.

The degassing section <NUM> has an air communicator <NUM> intended for guiding air to the lower part of counter-flow applicator arrangement <NUM>.

The air communicator <NUM> has an air communicator outlet <NUM> and an air communicator inlet <NUM>.

<FIG> illustrates a cross section view of a cleansing system <NUM>, the cross section being through a first reactor <NUM> and a second reactor <NUM>.

The cleaning system <NUM> has two cleansing system inlets <NUM> located at the centre <NUM> of the cleansing system.

The cleansing system <NUM> has a mechanical filter <NUM>. The mechanical filter is a drum filter.

<FIG> illustrates a cross section view of a cleansing system <NUM>, the cross section being through first reactor <NUM> and a degassing section <NUM>.

The cleaning system <NUM> has two cleansing system inlets 15a,b and is capable of receiving an aqueous medium <NUM> (not shown) from two fish tanks <NUM> (not shown).

<FIG> illustrates a side view of a recirculating aquaculture system <NUM> comprising a cleansing system <NUM> and a fish tank <NUM>.

The cleansing system <NUM> has a cleansing system inlet <NUM> for receiving water from a fish tank <NUM> and a cleansing system outlet <NUM> for providing the cleansed aqueous medium to the fish tank <NUM>.

The cleansing system outlet <NUM> has a pump <NUM> intended for pumping the cleansed aqueous medium <NUM> to the fish tank <NUM>.

The fish tank <NUM> has a fish tank inlet <NUM>. The lower part of the fish tank <NUM> is cone-shaped and a fish tank outlet <NUM> located at the centre of the fish tank <NUM>.

The fish tank <NUM> has a fish tank outlet <NUM> in communication with the cleansing system inlet <NUM> which cleansing system inlet <NUM> is at a gravitational level that is lower than a fish tank outlet leveller <NUM> (see <FIG>) of the fish tank <NUM>. The cleansing system outlet <NUM> is in communication with a flow-setter <NUM> in the fish tank <NUM>. There is a pump <NUM> in the communication between the cleansing system <NUM> and the fish tank <NUM>.

<FIG> illustrates a top view of multiple RAS-systems <NUM>, where each RAS-system <NUM> comprise a cleansing system <NUM> in connection with two fish tanks <NUM>.

The cleansing system <NUM> comprises a pair <NUM> of second reactors <NUM> and a pair <NUM> of degassing sections <NUM>.

The RAS-system <NUM> has a buffer tank <NUM>.

Aquaculture system wall <NUM> shields the fish tanks <NUM> from the cleansing system <NUM>.

<FIG> illustrates a side view of a fish tank <NUM>.

The fish tank <NUM> is cone-shaped towards the bottom end and has a central fish tank outlet <NUM>.

<FIG> illustrates a top view of a fish tank <NUM> with a fish tank wall <NUM>.

The fish tank <NUM> has a central fish tank outlet <NUM> surrounded by a fish tank outlet leveller <NUM>.

The fish tank <NUM> has two flow-setters 600a,b located inside the tank <NUM> and near the wall <NUM>. The flow-setters 600a,b are arranged and extend upwards at the fish tank wall <NUM>.

<FIG> illustrates a side view of a flow-setter <NUM> and <FIG> illustrates a perspective view of a flow-setter <NUM>.

The flow-setter has flow-setter perforations <NUM> to provide the cleansed aqueous medium <NUM> (not shown) to the fish tank <NUM> (not shown). The flow-setter perforations <NUM> extend in the upward direction <NUM>. The flow-setter perforations are intended for outletting the aqueous medium <NUM> to the fish tank <NUM>.

The flow-setter has a flow-setter inlet <NUM> to receive the aqueous medium <NUM> from the cleansing system <NUM> (not shown). The flow-setter inlet <NUM> is located at the lower part of the flow-setter <NUM>.

The flow-setter has mountings <NUM> for mounting the flow-setters in the fish tank <NUM>.

<FIG> illustrates a recirculating aquaculture system <NUM>, the system comprising a cleansing system <NUM> a fish tank <NUM>. The water is recirculated between the fish tank <NUM> and the cleansing system <NUM>.

From the fish tank <NUM> water overflows into the fish tank outlet <NUM> at fish tank outlet leveller level <NUM> determined by a fish tank outlet leveller <NUM> and flows via a piping system to a cleansing system inlet <NUM> at a cleansing system inlet level <NUM> into the cleansing system <NUM>. From the cleansing system <NUM> there is a cleansing system outlet and by a pump <NUM> the water is elevated back into the fish tank <NUM> and a flow is established by a flow-setter <NUM>.

The cleansing system <NUM> may be configured as disclosed in the figure, configured as disclosed in the previous figures or as in <FIG> and <FIG>.

<FIG> illustrates, in continuation of <FIG>, a cleansing system <NUM> and a fish tank <NUM> interconnected as a RAS-system. The cleansing system <NUM> is arranged with a first volume <NUM> surrounded by an annulus section <NUM> with a first arc forming a second volume <NUM> and a second arc forming third volume <NUM>. From the first volume <NUM> there is radial flow <NUM> parting the medium into the second volume <NUM> and into the third volume <NUM>. There is a tangential directed flow <NUM> from the second volume <NUM> to the third volume <NUM>. The cleansing system <NUM> is configured with leveller arrangements so that ordered gravitationally from a highest level, the order is fish tank outlet leveller level <NUM>, cleansing system inlet level <NUM>, first-second-overflow leveller level <NUM>, and lowest second-third-overflow leveller level <NUM>. The first-third overflow leveller level <NUM> is not shown, but it may be at the first-second overflow leveller level <NUM> or between that and the second-third overflow leveller level <NUM>.

<FIG> illustrates a cleansing system <NUM> configured to receive aqueous medium <NUM> from at least one fish tank <NUM> (not shown) and to return a cleaned aqueous medium (<NUM>) to the at least one fish tank <NUM>.

The cleansing system <NUM> comprises a cleansing system inlet <NUM> arranged at a cleansing system inlet level <NUM> to inlet the aqueous medium <NUM> into a first volume <NUM>. The first volume <NUM> is substantially surrounded by an annulus section <NUM> having at second volume <NUM>. The first volume <NUM> and the second volume <NUM> are in communication via at least a first-second-overflow leveller <NUM> arranged at first-second overflow leveller level <NUM> and to radially overflow the aqueous medium <NUM> from the first volume <NUM> to the second volume <NUM>.

In this embodiment, there is a radially directed outward flow <NUM> from the first volume <NUM> to respective second volume <NUM> and third volume <NUM>. The radially directed outward flow <NUM> is from the first volume <NUM> to the second volume <NUM> via a first-second overflow leveller <NUM> arranged with a first-second overflow leveller level <NUM>. The leveller is at the wall here formed as the inner circle of the annulus section <NUM>. The leveller may be a barrier or valve which may be adjustable to adjust the first-second overflow leveller level <NUM>. Similarly, the radially directed outward flow <NUM> is from the first volume <NUM> to the third volume <NUM> via first-third overflow leveller <NUM> arranged with a first-third overflow leveller level <NUM>.

There is also a tangentially directed flow <NUM> from the third volume <NUM> to the second volume <NUM> via a second-third overflow leveller <NUM> at a second-third overflow leveller level <NUM>.

There is a cleansing system outlet <NUM> arranged in the annulus section <NUM> configured to outletting the now cleaned aqueous medium <NUM> from the annulus section <NUM>. In this embodiment, the cleansing system outlet <NUM> is from the second volume <NUM>.

With reference to <FIG>, the first volume <NUM> may be configured as a first reactor <NUM>. The second volume <NUM> may be configured as a degassing section <NUM>. The third volume <NUM> may be configured as a second reactor <NUM>.

The first-second overflow leveller <NUM> may be configured as the degassing inlet <NUM> between the first reactor <NUM> and the degassing section <NUM> as seen in <FIG> and <FIG>. The first-third overflow leveller <NUM> may be configured as one or more of the reactor inlet pipe(s) <NUM>, see <FIG>, between the first reactor <NUM> the second reactor <NUM>. The second-third overflow leveller <NUM> may be configured as the overflow leveller <NUM> between the second reactor <NUM> and the degassing section <NUM> e.g. in <FIG>.

<FIG> discloses an additional configuration and features of a cleansing system <NUM>. For illustrative purposes the cleansing system <NUM> is shown in connection with two fish tanks <NUM> each supplied by pumps <NUM>. The return system is not shown.

<FIG> uses elements readily available from <FIG> such as the levellers <NUM> and level <NUM>. Other overflows levellers and flows are understood in view of previous figures and the arrows show the intended or implied resulting flow directions.

A first volume <NUM> is enclosed or surrounded by an annulus section <NUM> comprising a second volume <NUM>, and here two third volumes <NUM>.

The cleansing system <NUM> has an annulus section <NUM> that is parted in arc-sections <NUM> forming at least a further volume <NUM>. The further volume <NUM> is a fourth volume <NUM> that is in the annulus section <NUM>. The first volume <NUM> and the fourth volume <NUM> are in communication via at least a first-fourth-overflow leveller <NUM> arranged at a first-third overflow leveller level <NUM> to radially overflow the aqueous medium <NUM> from the first volume <NUM> to the fourth volume <NUM>.

Optionally there may be return flow means <NUM> for returning the aqueous medium <NUM> from a volume in the annulus section <NUM> to the first volume <NUM> in a return flow <NUM>. The return flow <NUM> is here shown from the fourth volume <NUM> back into the first volume <NUM>. The return flow means <NUM> may be perforations in the wall section between the annulus section <NUM> and the first volume <NUM>. Alternatively, the return flow means <NUM> may be a pump arrangement.

The third volume <NUM> and the fourth volume <NUM> are in communication via at least a third-fourth-overflow leveller <NUM> arranged at third-fourth overflow leveller level <NUM> and to tangentially overflow the aqueous medium <NUM> from the fourth volume <NUM> to the third volume <NUM>.

Optionally there may be return flow means <NUM> for returning the aqueous medium <NUM> from the fourth volume <NUM> to the first volume <NUM> as a return flow <NUM>.

The volumes disclosed in <FIG> may be configured as follows. The first volume <NUM> is configured to for nitrification of the aqueous medium <NUM>. The second volume <NUM> is configured for degassing the aqueous medium <NUM>. The third volume <NUM> is configured for nitrification of the aqueous medium <NUM>. The fourth volume <NUM> is configured for de-nitrification of the aqueous medium <NUM>.

In this particular embodiment, the cleansing system <NUM> may be considered as being configured as follows. The first volume <NUM> is configured as a moving bed type of reactor.

The second volume <NUM> is configured for degassing the aqueous medium <NUM>. The second volume <NUM> is sandwiched between two third volumes <NUM>. Each third volumes <NUM> are configured as a fixed bed type of reactor. The fourth volume <NUM> is between the two third volumes <NUM> and configured for de-nitrification of the aqueous medium <NUM>.

In this embodiment, the flow from the first volume <NUM> to volumes (second <NUM>, third <NUM> or fourth volumes <NUM>) is through a permeable retainer <NUM> that is configured to allow the aqueous medium <NUM> to flow into volumes in the annulus section <NUM> whilst retaining say bio-cleaning elements in the first volume <NUM>. In this embodiment, the first volume <NUM> is separated with other volumes by individual permeable retainers <NUM>. A permeable retainer may be a screen with perforations or holes impermeable to bio-cleaning elements.

<FIG> exemplifies the embodiment illustrated in <FIG> and the reference numbers are readily recognisable from <FIG>.

A person skilled in the art will readily be able to install one or more pumping systems to provide the aqueous medium to the chamber or to move the aqueous medium from the chamber.

In this example, the additional chamber <NUM> i.e. the fourth volume <NUM> is configured for de-nitrification <NUM>. There is a cover <NUM> or lid. There is an air lift <NUM> arrangement seen in the volume.

Also shown are details of the third volume <NUM>, which here is arranged as a fixed bed type of chamber for nitrification. The third volume <NUM> has air lifts arranged.

The generic configuration disclosed in <FIG> may be implemented in special configurations derived from <FIG>.

Claim 1:
A cleansing system (<NUM>) configured to receive aqueous medium (<NUM>) from at least one fish tank (<NUM>) and to return a cleaned aqueous medium (<NUM>) to the at least one fish tank (<NUM>); the cleansing system (<NUM>) comprising:
- a cleansing system inlet (<NUM>) arranged at a cleansing system inlet level (<NUM>) to inlet the aqueous medium (<NUM>) into a first volume (<NUM>) that is substantially surrounded by:
- an annulus section (<NUM>) having a second volume (<NUM>), and where the first volume (<NUM>) and the second volume (<NUM>) are in communication via at least a first-second-overflow leveller (<NUM>) arranged at a first-second overflow leveller level (<NUM>) and to radially overflow the aqueous medium (<NUM>) from the first volume (<NUM>) to the second volume (<NUM>); wherein the annulus section (<NUM>) is parted in arc-sections (<NUM>) forming at least a further third volume (<NUM>) in the annulus section (<NUM>), where the first volume (<NUM>) and the third volume (<NUM>) are in communication via at least a first-third-overflow leveller (<NUM>) arranged at a first-third overflow leveller level (<NUM>) and to radially overflow the aqueous medium (<NUM>) from the first volume (<NUM>) to the third volume (<NUM>); and the second volume (<NUM>) and the third volume (<NUM>) are in communication via at least a second-third-overflow leveller (<NUM>) arranged at a second-third overflow leveller level (<NUM>) and to tangentially overflow the aqueous medium (<NUM>) from the third volume (<NUM>) to the second volume (<NUM>); and
- a cleansing system outlet (<NUM>) arranged in the annulus section (<NUM>) configured to outletting (<NUM>) the now cleaned aqueous medium (<NUM>) from the annulus section (<NUM>).