Land-based treatment plant and method for cleaning wastewater from aquaculture facilities

Abstract

Land-based treatment plant (10) for purifying wastewater from aquaculture facilities, comprising a cleaning basin (12) with inlet (14) for wastewater from one or more aquaculture facilities and outlet (16) for discharge of purified water. The cleaning basin (12) comprises a flow rectifier (24) located downstream of said inlet (14) for waste water, which flow rectifier (24) is adapted to unidirect a low-speed water flow into a sedimentation chamber (18) in the cleaning basin (12), and that a bottom (18a) in the sedimentation chamber (18) comprises filter orifices (28), as particles, related to their sinking speed, fall towards the bottom (18a) and are drawn towards the filter orifices (28), whereupon sludge / sludgy water is collected in an underlying collection chute (30) connected to a sedimentation tank (32) arranged for receiving said sludge / sludgy water.

Description

[0001]Land-based treatment plant and method for cleaning wastewater from aquaculture facilities. Field of the invention The present invention relates to a land-based treatment plant for the purification of wastewater from aquaculture facilities, comprising a cleaning basin with an inlet for wastewater from one or more aquaculture facilities and an outlet for discharging purified water, as well as a method for purifying wastewater from the aquaculture facility using the treatment plant. Background of the invention Land-based fish farming is a focus area, nationally and internationally. Excrement and feed waste are the main part of emissions, and almost 100% of the particulate waste. Amounts of faeces and feed waste released from fish farming constitute a source of organic material which is taken up by a number of marine organisms. If the amount of faeces and feed waste becomes too high, the environment will not be able to convert all the material, and there will be an accumulation of organic material on the bottom. The emissions of faeces will vary with the size of the production, feed composition, feeding regime, fish size and temperature, and the total amount can be calculated using mass balance budgets or operational models. The amount of feed waste will depend on the feeding regime and method and will vary between plants. Land-based hatchery production takes place in closed vessels, raceways, earthen ponds, etc., where the discharge is carried to the sea, river, or water. Discharges from aquaculture facilities can affect the water environment in the recipient if it is overloaded with organic matter and nutrient salts. Remains of feed and excrement can accumulate on the bottom and lead to a lack of oxygen so that the decomposition process in the bottom sediments stops. This in turn can lead to local extinction and changes to the benthic fauna. In marine facilities, most of it falls to the bottom and / or is carried on by currents and waves. Many land plants have waste pipes that run directly into the sea, often with little or no purification so that waste feed and excrement freely flow out and contaminate the recipient, both water and bottom. Furthermore, it is not unknown that wild fish stand by the outlets and eat the waste with the feed waste and excrement, with associated disease and reduced fish welfare. In land plants, there is extensive use of drum filters to capture particulate waste. Use of drum filters and other mechanical filter types will grind up and crush parts of the waste into smaller particles that are released through the filter cloth, or via the small holes in the drum filter. The result is that a significant part of the particulate waste is broken down into very small particles that are difficult to separate out / collect, and thereby eventually end up in the waste water and in the recipient. The particles' sinking speed depends on the particles' size and weight. Faeces are often fragile and easily break up into smaller parts that sink at different speeds. Most have a sinking speed of 5–10 cm per second. A small proportion are very small and sink at a speed of less than 1 cm per second. The feed pellets are relatively firm, do not break easily and have sink speeds of over 10 cm per second. Disclosure of prior art US2001017281A1 relates to an apparatus and a process for biological wastewater purification. An activation tank is provided in which, with feed of a catalyst, wastewater constituents are degraded by degradation means, for example microorganisms, suspended in the wastewater. In the activation tank is disposed at least one lamellae pack in or on which the degradation means suspended in the wastewater are separated out by sedimentation to fall as thickened sedimentation means sludge to the bottom region of the activation tank. In the bottom region of the activation tank is provided forced recirculation of the degradation means, which takes up the thickened degradation means sludge and recirculates it as suspended degradation means back to the activation tank. WO2023043479A1 relates to a stormwater treatment device for removing contaminants from stormwater. Objects of the present invention It is an object of the present invention to produce a treatment plant for a land-based aquaculture facility, as well as a method for cleaning waste water from an aquaculture facility. A further object is to provide a treatment plant with a sedimentation chamber where the water flow rate is low with a low concentration of particulate matter. The treatment plant can be used for FTS (flow-through plant), FTS-R (partly water reuse plant), RAS (recirculating aquaculture system), and / or for other cleaning needs. Its purpose is to clean wastewater before discharge to the recipient, or for full or partial reuse for fish, algae, kelp, etc., as well as recovery of organic material such as excrement, feed waste, etc. The aim is to collect the largest possible proportion of organic waste for recycling and processing. The invention can provide affordable cleaning technology, and less energy use. For example, energy can be recovered (due to excess height) in turbines by returning kWh. The treatment plant is based on two stages: sedimentation and energy recovery. No chemicals, polymers, disinfectants, metals etc. need to be used. The purification method can be used to purify waste water from the farming of all types of fish. The technology and concept make it possible to collect waste particles in the waste water for disposal in a substance suitable for further treatment. Excrement and feed particles have a defined sink rate. The cleaning basin according to the invention has a shape (rectangular, pipe, slope), a volume and a flow rate which causes particulate waste to sink to the bottom, and is then carried on the bottom towards filter orifices. A chamber or chute below the filter orifices draws water and particulate waste out to separate sedimentation tanks. By using the treatment plant according to the invention, separation of the waste water into two levels of purity can be achieved. A large amount of water and little particulate waste make effective cleaning difficult, and is something sought to be avoided with the present invention. With the invention, a low water flow with a very large particulate content is achieved. This facilitates later separation, cleaning, and reuse, as well as excrement being slightly damaged, and is then better suited for processing / reuse. The speed of the water is reduced by increasing the cross-section of the water flow. The water flow is further made unidirectional so that direction and speed are the same throughout the flow area, without turbulence. Length, cross-sectional area, water height and speed can be adjusted in the treatment plant according to liquid consistency and the hydraulic characteristics of the particles. The water’s height energy can be recovered in a Kaplan turbine. Summary of the invention According to a first aspect of the present invention, a land-based treatment plant for purifying wastewater from aquaculture facilities is produced, comprising a cleaning basin with an inlet for wastewater from one or more aquaculture facilities and an outlet for discharging purified water. The cleaning basin comprises a flow rectifier placed downstream of said inlet for waste water, which flow rectifier is adapted to unidirect a low-velocity water flow into a sedimentation chamber in the cleaning basin, and that a bottom in the sedimentation chamber comprises filter orifices, as particles, related to their sinking speed, fall towards the bottom and are drawn towards the filter orifices, after which sludge / sludgy water is collected in an underlying collection chute connected to a sedimentation tank designed to receive said sludge / sludgy water. The cleaning basin comprises a level chamber arranged downstream of the sedimentation chamber, in which the level chamber and the sedimentation chamber are separated by a second transverse partition comprising several slits or pipes equipped with adjustable dampers to rectify the water flow. Alternative versions of the treatment plant are specified in respective independent claims. The flow rectifier may comprise a first transverse dividing wall which separates a pre- chamber upstream in the cleaning basin, wherein the flow rectifier comprises several pipes or channels to unidirect the low-speed water flow into the sedimentation chamber. Said filter orifices can comprise parallel slits that lie flush with the bottom of the sedimentation chamber. The slits of the filter orifices can in one embodiment be arranged with an angle to the direction of flow in the sedimentation chamber. An example of angle can be between 5-10º. Furthermore, the bottom of the sedimentation chamber can be surface-treated with a surface coating and / or have a slope that provides reduced friction and cavitation for waste moving along the bottom towards the filter orifices. The level chamber arranged downstream of the sedimentation chamber also comprises a third transverse partition wall, and which together with the second transverse partition having several slits or pipes equipped with adjustable dampers acts as a regulation mechanism that prevents turbulence and ensures smooth and stable water flow out of the sedimentation chamber. Said regulation mechanism is designed to keep a water level in the sedimentation chamber and the level chamber at a desired level before the water is released through said outlet. Said outlet for discharging purified water can be connected to one or more Kaplan turbines arranged downstream for energy recovery. The treatment plant may comprise several sedimentation tanks which are arranged to be used in a constant sequential or linear sedimentation process. The sedimentation tanks can be connected with a return line for the transport of treated waste water from the sedimentation tanks and back to the treatment basin. The return line can run to the pre-chamber and / or to the sedimentation chamber in the cleaning basin. The treatment plant can further comprise a dewatering tank connected to said sedimentation tanks, which dewatering tank is designed to receive sediment from the sedimentation tanks. The treatment plant can also include a surface skimmer designed to capture smaller particles, proteins and oils that can float to the surface of the water. In the treatment plant, the smallest sedimentation chamber can have a rectangular shape or a circular cylindrical shape. According to a second aspect of the present invention, a method is provided for cleaning wastewater from aquaculture facilities in a land-based treatment plant, where the method comprises the steps: - reception of waste water in a cleaning basin comprising a flow rectifier which directs the waste water into a low-velocity water flow into a sedimentation chamber in the cleaning basin, - wherein the waste water is brought to maintain a steady, stable, and calm flow of water in the sedimentation chamber so that particles, related to their sinking speed, fall towards the bottom of the sedimentation chamber and are drawn towards filter orifices with an underlying collection chute, - collection of sludge / sludgy water in the collection chute, wherein the quantity of collected sludge water is adjusted according to waste characteristics, whereafter said sludge / sludgy water is transported to a sedimentation tank, - storage of said sludge / sludgy water long enough for waste to sink to the bottom of the sedimentation tank as sediment, - pumping of clean water from the sedimentation tank and back to the cleaning basin, and - pumping sediment from the sedimentation tank to a dewatering tank for the formation of dewatered mass. Alternative embodiments of the method are specified in respective independent claims. According to the method, several sedimentation tanks can be used in a constant sequential sedimentation process, where the method comprises the steps: - pumping sludge / sludgy water into a first sedimentation tank until the tank is full or nearly full, followed by - pumping sludge / sludgy water to a second sedimentation tank until the tank is full or nearly full, followed by - pumping sludge / sludgy water to a third sedimentation tank until the tank is full or nearly full, and - emptying sediment from the first sedimentation tank when the third sedimentation tank is filled, as well as pumping clean water back to the cleaning basin and pumping sediment to a dewatering tank from the first sedimentation tank, - and to repeat the process for each sedimentation tank as previous sedimentation tanks are filled or emptied. Several sedimentation tanks can be used in a linear sedimentation process, where the procedure comprises the steps: - pumping sludge / muddy water into the sedimentation tank below the tank's water level, and - pumping purified water from the sedimentation tank's upper water layer back to the purification basin or to a further sedimentation tank for further purification, and - emptying sediment to the dewatering tank. Said sequential and linear processes can be combined between the sedimentation tanks. Furthermore, the dewatered mass from the dewatering tank can be processed further into reusable products, such as fertilizer, methane gas, feed for micro and smaller organisms, and into marine proteins. The cleaning basin may comprise a level chamber arranged downstream of the sedimentation chamber, the method comprising keeping a water level in the sedimentation chamber and the level chamber being kept at a desired level. The method can also include adding a flocculant to the cleaning basin, the flocculant being caused to bind to both particulate waste, suspended material and dissolved liquids / gases. Description of figures Preferred embodiments of the invention will be described in more detail below with reference to the accompanying figures, in which: Figure 1 shows in perspective a treatment plant according to the invention. Figure 2 shows a top view of the treatment plant according to the invention. Figures 3 and 4 show respective side views of the treatment plant according to the invention. Figures 5 and 6 show respective end views of the treatment plant according to the invention. Figure 7 shows filter orifices and a collection chute in the treatment plant according to the invention. Figure 8 shows a treatment plant with at least one circular-cylindrical sedimentation chamber. Description of preferred embodiments of the invention The treatment plant according to the invention can be constructed and calculated so that it can form foundations and / or foundation walls for buildings such as slaughterhouses, smolt plants, feed storage, offices, etc. This also reduces the total investment and space requirements. As shown in figure 1, the invention comprises a land-based treatment plant 10. The treatment plant 10 comprises a cleaning basin 12 for cleaning wastewater from one or more fish farming facilities (not shown). It would be natural for the aquaculture facility or facilities to also be located on land, but it is conceivable that the treatment plant can also be used with sea-based aquaculture facilities from which the waste water is pumped via pipelines. The cleaning basin 12 comprises one or more inlets 14 for receiving waste water from the breeding facility. Upstream in the cleaning basin 12, a first transverse dividing wall separates the cleaning basin 12 into a pre-chamber 20, adjacent to said inlet 14, and a sedimentation chamber 18. The inlet 14 or the inlets can be provided in the end wall or side wall of the cleaning basin 12 so that the waste water flows into the pre-chamber 20. The first transverse dividing wall comprises a flow rectifier 24 with pipes or channels which are arranged to unidirect a low-velocity water flow into the sedimentation chamber 18 in the cleaning basin 12. The water flow becomes approximately unidirectional and prevents turbulence from keeping particulate waste suspended in turbulent water flows. The flow rectifier 24 forms the first transverse partition and may comprise a pipe stack, as illustrated in the figures. The sedimentation chamber 18 may have a smooth bottom 18a which can be treated with a surface coating, and which provides reduced friction and cavitation for waste moving along the bottom. The bottom 18a can alternatively or additionally have a slope which contributes to a similar effect. The bottom 18a in the sedimentation chamber 18 also includes filter orifices 28, so that particles, related to their sinking speed, fall towards the bottom 18a and are drawn towards the filter orifices 28. Sludge or sludge-containing water is collected in an underlying collection chute 30 connected to a sedimentation tank 32. The quantity of collected sludge water can be adjusted according to waste characteristics, such as quantities, particle content and treatment capacities. It will it is natural that the filter orifices 28, and to that extent also the collection chute 30, are located downstream in the sedimentation chamber 18. As shown in Figure 2, the filter orifices 28 and the collection chute 30 are located at the opposite end of the sedimentation chamber 18 from where the water flow enters from the pre-chamber 20. The sedimentation chamber 18 can further comprise a scraper, skimmer or similar to clean the bottom, and possibly the sidewall, of the chamber 18. Water flow in the sedimentation chamber 18 will be unidirectional and homogeneous. The design of the sedimentation chamber 18 can be calculated in length, width, height or, in the case of a circular tank, diameter, in order to maintain a smooth, stable and / or calm water flow. Particles, related to their sinking speed, fall into the sedimentation chamber 18 and towards the bottom 18a and are drawn towards the filter orifices 28. Safety margins for different sinking speeds can be taken into account when calculating the best possible water speed, current, length, width, depth, or diameter. The filter orifices 28 and the collection chute 30 are, as mentioned, preferably located at the end of the sedimentation chamber 18, i.e., downstream in the sedimentation chamber 18. The filter orifices 28 can be designed so that no changes occur in the water flow, which in turn will lead to swirling of waste materials and reduced cleaning. The filter orifices 28 are designed to create a smooth, parallel, homogeneous, laminar, and stable water flow. The filter orifices 28 can in one embodiment comprise one or more rows of longitudinal and parallel slits (when using several rows of slits) which lie completely flush with the bottom 18a of the sedimentation chamber 18. The slits can, for example, be approx.1 meter long and have a slight angle (approx.5 – 10 degrees) in the longitudinal direction (flow direction), as shown in figure 7. The slits can be placed longitudinally or alternatively transversely on the bottom 18a in the sedimentation chamber 18. From Figure 7, it is further clear that the collection chute 30 can, for example, have a V shape and be equipped with a device, for example in the form of one or more perforated pipes 40, which sucks the sludge from the entire collection chute 30. The collection chute 30 can alternatively have an approximate W shape or a U shape, preferably with a flat bottom. The collection chute 30 can further comprise a scraper, skimmer or similar to clean the bottom and sidewall of the collection chute 30. After (downstream) the filter orifices 28 and the collection chute 30, a second transverse partition wall is placed, and which separates the cleaning basin 12 in the sedimentation chamber 18 and a level chamber 22. The second partition wall comprises slits or tubes 26 equipped with dampers to regulate the water flow out of the sedimentation chamber 18, and possibly a third transverse partition wall 38. The second transverse partition wall with the pipes 26 can similarly be designed as a stack of pipes, and functions as a regulation mechanism (flow rectifier) together with the third partition wall 38. The second transverse partition with the adjustable slots or pipes 26 prevents turbulence and speed changes at the end of the sedimentation chamber 18 and out of the sedimentation chamber 18. This is to avoid creating water currents that can swirl up particulate waste. The level chamber 22 further contributes to stabilizing the water level in the pre- chamber 20 and the sedimentation chamber, and that the regulation mechanism (which may comprise the tubes 26 or the slits with dampers and the third partition wall 38) in the level chamber 22 keeps the water level in the sedimentation chamber and the level chamber 22 at a desired level, before discharge of water out the outlet 16. The lines in figures 1 and 2 are intended to illustrate level regulation in the sedimentation chamber 18. The level chamber 22 may further comprise aerating means to remove gases from the water, possibly placed after the pipes 26 (the second flow rectifier). Such aerating means can also be placed after the Kaplan turbines. The water will also be able to be aerated in the level chamber 22. Aeration in each sedimentation tank 32 can remove much of the dissolved substances such as nitrogen, phosphorus, CO2 , ammonia etc. Said outlet 16 may comprise one or more outlets and which are connected to Kaplan turbines (not shown). The Kaplan turbines can be mounted within the tubes of the outlets 16. The waste water can flow from the level chamber and pass the Kaplan turbines via, for example, a drop chamber before discharge to the recipient. The energy recovery will in principle be able to provide a 40-60% reduction in (pumping costs) energy consumption. Figure 8 shows an alternative embodiment of the treatment plant 10 according to the invention, where the treatment plant 10 comprises at least a circular-cylindrical sedimentation chamber 18. However, the entire cleaning basin 12 can also have the same shape. The filter orifices 28 are placed inside and at the lowest point of the sedimentation chamber 18, and is, as previously explained, positioned above a collection chute 30 which is connected to sedimentation tanks 32. The treatment plant shown in Figure 8 can similarly be equipped with the flow rectifier 24 comprising the first transverse partition that separates the pre-chamber 20 upstream in the cleaning basin 12, where the flow rectifier 24 comprises several pipes or channels to unidirect the low-speed water flow into the sedimentation chamber 18. In a similar way, the cleaning basin 12 comprises the level chamber 22 arranged downstream of the sedimentation chamber 18, where the level chamber 22 and the sedimentation chamber 18 are separated by the second transverse partition wall with several slits or tubes 26 equipped with adjustable dampers and the third transverse partition wall 38, and which functions as a regulation mechanism that prevents turbulence and ensures steady and stable water flow from the sedimentation chamber 18. The sludge or the sludge-containing water that is captured by the filter orifices 28 in the collection chute 30 will have a volume that has little water and a high concentration of excrement and feed waste, and which is brought and / or pressed / suctioned from the collection chute 30 through lines or pipe on to the sedimentation tanks 32 and subsequent sedimentation process. Openings - slits, in filter orifices 28 will be adapted to water speed, waste type and operating model. The collection chute 30 can be equipped with a device, such as one or more perforated pipes 40, which suck the sludge from the entire collection chute. Said pipe 40, or another means, can be used to adjust water amount removed from the collection chute 30. The quantity of sludge water pumped out from the collection chute can be adjusted to fit the amount of particles and sludge characteristics, etc. Particles that float up in the cleaning basin 12 can be caught by a skimmer (not shown) for surface cleaning and collected in a separate tank, which is included in the total sludge collection. A flocculating agent can also be added to the cleaning basin 12, which will bind to both particulate waste, suspended material and dissolved carrier gases. The flocculation agent can be adapted so that the sinking rate can be calculated, and in the case of flotation-flocculation, the skimmer can function as an ordinary surface skimmer in the plant. The skimmer for surface water can capture smaller particles, proteins and oils that can float up, and what binds to flotation-flocculation. As shown in the figures, the treatment plant 10 can comprise several large sedimentation tanks 32. From the collection chute 30, the sludge or water containing sludge can be pumped up into, for example, three large sedimentation tanks 32 which are used in a constant sequential and / or linear sedimentation process. The waste water with sludge / sludgy water in the sedimentation tanks 32 must be stagnant for a necessary number of hours, so that all waste substances sink to the bottom. After specified hours of standstill, clean water will be pumped back to the pre-chamber 20 or the sedimentation chamber 18. After specified hours, the sediment in the sedimentation tanks 32, consisting of excrement and feed waste, will be pumped to the dewatering tank 34. The compact dewatered mass can be processed further into a number of products such as fertilizer, methane gas, feed for micro and smaller organisms, and to marine proteins, etc. An example of a constant sequential sedimentation process can be as follows. Sludge and sludgy water are pumped up into a first sedimentation tank 321 until it is full or nearly full. Sludge and sludge-containing water are then pumped into the next sedimentation tank 322. The first sedimentation tank 321 then has a total stagnant water in a given unit of time, which is calculated from the sink rate of waste particles. Waste will then fall to the bottom. When the second sedimentation tank 322 is full or nearly full, filling (pumping) of sludge and sludge-containing water into a third sedimentation tank 323 begins. At the same time as the third sedimentation tank 323 is filled, sludge is emptied from the bottom of the first sedimentation tank 321 and the water is returned to the treatment plant 10. When the third sedimentation tank 323 is full or nearly full, then the first sedimentation tank 321 is free, and the process then continues, from tank to tank. This is repeated in a "perpetual" process, in a purely sequential mode of operation. In the case of a linear collection, sludge will be sent into the sedimentation tank 32 below the water level in the tank. Waste particles will sink to the bottom, while the outlet of purified water is taken out from the top of the sedimentation tank 32, i.e., the upper water layer. The precipitate is sent to the dewatering tank 34 for further drainage. Purified water is collected from the top and can be sent to a sedimentation tank 32 for further purification, alternatively back to the purification basin 12 or to the recipient. Cleaning equipment, tank volume, water quantities and time program for sinking speed are calculated so that a tank can be maintained, pumps serviced etc., without affecting the cleaning capacity. The time the waste water with sludge / sludgy water must be stagnant in the sedimentation tanks 32 can be calculated based on volume, amount of water and type of waste, so that it is ensured that most of the waste substances sink to the bottom. Purified water is then pumped back as explained, and sediment, consisting of excrement and feed waste, is pumped to the dewatering tank 34. With the present invention, a treatment plant is provided in which a very high degree of purification is achieved, and wastewater almost without particulate waste. Reuse of all organic – particulate material. Purified water can be reused in the breeding facility, but purified water can also be used as purified fresh water for the cultivation of several species, and for agriculture, greenhouses etc. Or as purified seawater for the cultivation of other fish species, for own use, and for the cultivation of seaweed, kelp, algae, shells, and benthic animals (especially bristle worm). In the production of for instance bristle worm, which is very relevant, the correct and controlled amount of waste from the sedimentation tanks can be processed and positioned as feed for bristle worms. The main goal is a high degree of cleaning for aquaculture facilities on land, avoiding that waste materials are destroyed and ground up, the greatest possible separation between water and waste materials, and energy-efficient and cost-effective cleaning. The cleaning method is suitable for safeguarding the values and resources contained in the waste, for further processing. The treatment plant 10 can also be equipped with mechanisms to keep the collection chute 30 free from the collection of waste substances. The treatment plant will be able to be divided into modules and have access from the top for module-based cleaning and maintenance without unnecessary operational disruptions.

Claims

Patent claims 1. A land-based treatment plant (10) for the purification of wastewater from aquaculture facilities, comprising a cleaning basin (12) with inlet (14) for wastewater from one or more aquaculture facilities and outlet (16) for discharge of purified water, wherein the cleaning basin (12) comprises a flow rectifier (24) placed downstream of said inlet (14) for waste water, which flow rectifier (24) is adapted to unidirect a low-velocity water flow into a sedimentation chamber (18) in the cleaning basin (12), a bottom (18a) in the sedimentation chamber (18) comprises filter orifices (28), as particles, related to their sinking speed, fall towards the bottom (18a) and are drawn towards the filter orifices (28), after which sludge / slugdy water is collected in an underlying collection chute (30) connected to a sedimentation tank (32) arranged for receiving said sludge / sludgy water, and wherein the cleaning basin (12) comprises a level chamber (22) arranged downstream of the sedimentation chamber (18), in which the level chamber (22) and the sedimentation chamber (18) are separated by a second transverse partition comprising several slits or pipes (26) equipped with adjustable dampers to rectify the water flow.

2. The treatment plant (10) in accordance with claim 1, characterized in that the rectifier (24) comprises a first transverse partition wall which separates a pre- chamber (20) upstream in the purification basin (12), the rectifier (24) comprising several pipes or channels for said unidirecting of the low-velocity water flow into the sedimentation chamber (18).

3. The treatment plant (10) in accordance with claim 1, characterized in that said filter orifices (28) comprise parallel slits which lie flush with the bottom (18a) of the sedimentation chamber (18).

4. The treatment plant (10) in accordance with claim 3, characterized in that the slits of the filter orifices (28) are arranged at an angle to the direction of flow in the sedimentation chamber (18).

5. The treatment plant (10) in accordance with claim 1, characterized in that the bottom (18a) of the sedimentation chamber (18) is surface-treated with a surfacecoating and / or has a slope that provides reduced friction and cavitation for waste moving along the bottom (18a ) against the filter orifices (28).

6. The treatment plant (10) in accordance with claim 1, characterized in that the level chamber (22) further comprises a third transverse partition (38), and which together with the second transverse partition having several slits or pipes (26) equipped with adjustable dampers functions as a regulation mechanism that prevents turbulence and ensures a smooth and stable flow of water out of the sedimentation chamber (18).

7. The treatment plant (10) in accordance with claim 6, characterized in that said regulation mechanism is designed to keep a water level in the sedimentation chamber (18) and the level chamber (22) at a desired level before the water is released through said outlet (16).

8. The treatment plant (10) in accordance with claim 1, characterized in that said outlet (16) for discharging purified water is connected to one or more Kaplan turbines arranged downstream for energy recovery.

9. The treatment plant (10) in accordance with claim 1, characterized in that the treatment plant comprises several sedimentation tanks (32) which are designed to be used in a constant sequential or linear sedimentation process.

10. The treatment plant (10) in accordance with claim 1 or 9, characterized in that said sedimentation tanks (32) are connected to a return line (36) for the transport of purified wastewater from the sedimentation tanks (32) and back to the purification basin (12).

11. The treatment plant (10) in accordance with claim 10, characterized in that the return line (36) runs to the pre-chamber (20) and / or to the sedimentation chamber (18) in the purification basin (12).

12. The treatment plant (10) in accordance with claim 1, characterized in that the treatment plant comprises a dewatering tank (34) connected to said sedimentation tanks (32), which dewatering tank (34) is designed to receive sediment from the sedimentation tanks (32) .

13. The treatment plant (10) in accordance with claim 1, characterized in that the treatment plant comprises a surface skimmer designed to capture smaller particles, proteins and oils that can float to the surface of the water.

14. The treatment plant (10) in accordance with claim 1, characterized in that at least the sedimentation basin (18) has a rectangular shape or a circular cylindrical shape.

15. A method for cleaning wastewater from aquaculture facilities in a land-based treatment plant (10) in accordance with one or more of claims 1-14, characterized in that the method comprises the steps: - reception of waste water in a purification basin (12) comprising a flow rectifier (24) which unidirect the waste water into a low-velocity water flow into a sedimentation chamber (18) in the cleaning basin (12), - wherein the waste water is brought to maintain a steady, stable, and calm flow of water in the sedimentation chamber (18) so that particles, related to their sinking speed, fall towards the bottom (18a) of the sedimentation chamber and are drawn towards filter orifices (28) with an underlying collection chute (30), - adjustable collection of sludge / sludgy water in the collection chute (30), after which said sludge / sludgy water is transported to a sedimentation tank (32), - storage of said sludge / sludgy water long enough for waste to sink to the bottom of the sedimentation tank (32) as sediment, - pumping clean water from the sedimentation tank (32) and back to the cleaning basin (12), and - pumping sediment from the sedimentation tank (32) to a dewatering tank (34) to form dewatered mass.

16. The method in accordance with claim 15, characterized in that several sedimentation tanks (32) are used in a constant sequential sedimentation process, where the method comprises the steps: - pumping sludge / sludgy water into a first sedimentation tank (321) until the tank is full or nearly full, followed by - pumping sludge / sludgy water to a second sedimentation tank (322) until the tank is full or nearly full, followed by - pumping sludge / sludgy water to a third sedimentation tank (323) until the tank is full or nearly full, and- emptying sediment from the first sedimentation tank (321) when the third sedimentation tank (323) is filled, as well as pumping clean water back to the cleaning basin (12) and pumping sediment to a dewatering tank (34) from the first sedimentation tank (321), and - to repeat the process for each sedimentation tank (32) as previous sedimentation tanks (32) are filled or emptied.

17. The method in accordance with claim 15, characterized in that several sedimentation tanks (32) are used in a linear sedimentation process, where the method comprises the steps: - pumping sludge / sludgy water into the sedimentation tank (32) below the tank's water level, and - pumping purified water from the sedimentation tank's (32) upper water layer back to the cleaning basin (12) or to a further sedimentation tank (34) for further purification, and - emptying sediment to the dewatering tank (34).

18. The method in accordance with claims 16 and 17, characterized in that said sequential and linear processes are combined between the sedimentation tanks (32).

19. The method in accordance with claim 15, characterized in that the dewatered mass from the dewatering tank (34) is further refined into reusable products, such as fertilizer, methane gas, feed for micro and smaller organisms, and into marine proteins.

20. The method in accordance with claim 15, characterized in that the cleaning basin (12) comprises a level chamber (22) arranged downstream of the sedimentation chamber (18), in which a water level in the sedimentation chamber (18) and the level chamber (22) is kept at a desired level.

21. The method in accordance with claim 15, characterized in that the method comprises adding a flocculant to the cleaning basin (12), the flocculant being caused to bind to both particulate waste, suspended material and dissolved liquids / gases.

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