DE102019003346B3 - Method and device for oxygenating water in a fish farm - Google Patents

Abstract

The invention relates to a method and a device for the oxygenation of water in a fish farm, in which a fish population is kept in a network enclosure within a body of water. According to the invention, it is provided that air is fed into a vertically running pipeline for conveying water from deeper layers of the water into the area of the surface and oxygen is additionally fed in in the area of the lower mouth opening of the pipeline. The oxygen dissolves to a considerable extent in the water and thus leads to an oxygen enrichment of the extracted water. The oxygen-enriched water is returned to the water in the area of the water surface above the network enclosure.

Description

The invention relates to a method for oxygenation of water in a fish farm, in which a fish stock is kept in a net enclosure within a body of water and water is conveyed from a deeper layer of the water into the area of the water surface above the net enclosure by adding water into a lower mouth opening of a pipeline running upwards at least in sections within the water, the water flowing into the pipeline is mixed with air supplied above the lower mouth opening, but below the water surface, and an upward flow in the pipeline is thereby generated.

The invention further relates to a fish farming system equipped with a device for oxygen enrichment with a network enclosure arranged in a body of water.

In standing waters, depending on the climatic conditions of the environment, a horizontal stratification is formed, which is characterized by zones of different temperatures and oxygen concentrations. A typical stratification of a lake shows a near-surface layer (epilimnion) in summer, which ends about 4-6m below the water surface and is characterized by a strong thermal and material exchange with the surrounding atmosphere. The epilimnion is followed by a transition layer (metalimnion) in which the temperature and oxygen concentration decrease sharply with increasing depth. Below the Metalimnion is the deep water layer (Hypolimnion) from a depth of about 8-10 m with a year-round essentially constant temperature of about 4 ° C and a very low oxygen content of max. 4-5 mg / l.

Freshwater fish in aquaculture are usually cultivated in specially designed fish ponds or flow channels. More intensive fish farming allows the use of net enclosures or fish cages, which are placed in larger freshwater waters, for example for breeding trout, or in the open sea for breeding sea fish such as salmon. Net enclosures usually have a diameter between 4 and 60 m and a depth between 4 and 10 m. The present invention relates to fish farms with net enclosures or fish cages which are arranged within a body of water, for example in a freshwater lake or in the sea.

The natural entry of oxygen into standing water occurs on the one hand on the water surface by diffusion from the air and on the other hand through photosynthesis of the aquatic plants. The solubility of oxygen in water decreases with increasing temperature. High ambient temperatures lead to a lack of oxygen in the water, which affects the health of the fish and slows their growth. In such cases, artificial ventilation of the fish farm is required.

For the aeration of fish ponds, aeration systems are currently used in particular, in which water from deeper water layers is conveyed to the surface by means of an electric pump, where it mixes with ambient air. Furthermore, paddlewheel aerators are used, in which the surface water is circulated and thereby brought into contact with ambient air. Deep aerators are also used in particular for the restoration of standing water, in which air is introduced directly into deeper water layers by means of a compressor. A disadvantage of these systems, however, is the high outlay and the comparatively low efficiency.

The DE 20 2018 001 727 U1 describes a device for circulating and aerating water, especially fish ponds. The device described therein comprises a flow pump working according to the air lifter principle (mammoth pump principle), in which an air-water mixture is generated on the bottom in a pipeline reaching to the bottom of the water, which is then passed through an obliquely upward pipe section and emerges below the water surface. In this way, a strong current is created to circulate and aerate the water. However, the device is only suitable for aerating smaller, and above all with a maximum depth of about 1.5 m, rather shallow water. In addition, it requires the use of elaborate electrical pump arrangements to supply the air.

Tue US 6 017 020 A. describes a system for introducing air into a lake. The entry system comprises two pipes of several meters in length, which are arranged coaxially to one another and deeply embedded in the lake bed, and are connected to one another at their lower ends. Also at the lower end is a device for introducing air into the inner tube. When using the device, water flows through the outer tube into the inner tube, where it is enriched with air and rises due to the mammoth pump effect. However, due to the submarine arrangement, the entry system is very complex to install and maintain. Not least for this reason, this system is also only suitable for the ventilation of shallow waters of, for example, 1.5m depth and therefore not for fish farms that are equipped with net enclosures.

From the DE 36 15 629 A1 , of the DE 37 03 562 A1 , of the US 4,044,720 A. and the US 5,741,443 A Methods and devices for oxygen enrichment in water are known in which deep water is sucked into the devices and released again into deep water layers via pipe systems, air or oxygen injection being provided at the water inlet.

From the US 8,800,969 B2 a method and a device for oxygen enrichment in water is known, in which deep water is sucked into the device and released again into deep water layers via pipe systems. An entry system for air or oxygen is provided at the water outlet so that gas flow and water flow are opposite.

However, the objects described in these documents are very complex to construct and / or require a high level of energy or oxygen to be used in operation.

The invention is therefore based on the object of creating a simple and reliable oxygenation of water in fish farms which are equipped with net enclosures or fish farming cages in water.

This object is achieved by a method having the features of patent claim 1 and by a device having the features of patent claim 6. Advantageous embodiments of the invention are specified in the subclaims.

A method according to the invention for the oxygen enrichment of water in a fish farm of the type and purpose mentioned at the outset is characterized in that oxygen is supplied to the water flowing into the pipeline from an oxygen source at an injection device which opens into the pipeline in the region of the lower mouth opening.

“Oxygen” is an oxygen-containing gas with an oxygen content of over 90 vol.%, Preferably over 95 vol.%. The source of oxygen (also called “oxygen source” here) is, for example, an oxygen tank, a compressed gas cylinder or a bundle of compressed gas cylinders.

According to the invention, on the one hand, a strong, upward flow in the pipeline is generated by supplying a strong air flow according to the mammoth pump effect, which leads to the water flowing in at the lower mouth opening being conveyed from deeper layers of the water into the area of the water surface and on flows out of an upper mouth opening of the pipeline, which opens out above the network enclosure. The upper mouth of the pipeline can be completely or partially above or below the water surface. The air is primarily used to generate the flow within the pipeline and can take place in a comparatively near-surface area, for example 1-3 m below the water surface. In addition to entering the air, oxygen is also introduced. This takes place in an area of the pipeline which, when the method is used, is arranged below the air supply, preferably close to the lower opening of the pipeline. For example, the injection device for the oxygen on the pipeline is located a few meters, for example 3-10 m, below the height of the air inlet. The suction effect of the air intake is sufficient to be able to suck water into the pipeline from such deep layers of the water; To generate the upward flow, it is therefore not necessary to introduce the air deep into the pipeline with a corresponding effort, for example in the region of the lower mouth opening. In contrast, the oxygen introduced further down into the water runs through a comparatively long distance in the pipeline, whereby it partially dissolves in the water.

The procedure according to the invention enables the pumping of comparatively cold and oxygen-poor water from deeper water layers, into which the supplied oxygen can be redeemed well. For example, a comparatively small volume flow of supplied oxygen of, for example, 1 to 5 l / min is sufficient to enrich the supplied water with oxygen by, for example, 3-10 mg / l when there is an inflow of water via the pipeline of, for example, 5-20 l / s cause. In contrast, only a comparatively small part of the air entered dissolves in the water of the pipeline, as a result of which the nitrogen content in the water increases only slightly. The volume flow of the oxygen supplied is otherwise considerably less than the volume flow of the air supplied, which is, for example, 50-100 l / min, and, in contrast to this, only makes an insignificant contribution to conveying the water through the pipeline.

The method according to the invention cools the near-surface water in the network enclosure in summer operation by supplying cooler water from deeper layers of the water. In winter, however, the then comparatively warm water from the deeper layers prevents the water from freezing over. The method according to the invention is particularly suitable for fish farms which are set up in freshwater lakes, for example in larger natural lakes or in reservoirs; however, it is also suitable for aquaculture in the sea.

In order to further improve the dissolution of the oxygen in the water conducted through the pipeline, the injection device is preferably designed such that ambient water is introduced into the pipeline simultaneously with the oxygen. So there is already an intimate mixing of water and oxygen within the injection device. This takes place, for example, in that the oxygen supply to the injection device is designed in the manner of a Venturi nozzle and is sucked into the injection device from the water by the flow of the water which is introduced from the oxygen source at high pressure into the injection device and mixed with the oxygen.

According to the invention, the oxygen is introduced into the pipeline and / or into the injection device with an overpressure of preferably at least 3 bar, particularly preferably at least 5 bar, relative to the surrounding water pressure. The air supplied to generate the upward flow in the pipeline is introduced into the pipeline with an overpressure of, for example, 0.2 bar to 1 bar relative to the surrounding water pressure.

In a further advantageous embodiment of the method according to the invention, the lower mouth opening of the pipeline opens into the deep water of the water, so cold deep water is enriched with oxygen and conveyed through the pipeline to the network enclosure.

“Deep water” should be used here to refer to water that is low in oxygen and is present at a temperature of about 4 ° C., which is located far below the surface, preferably at a depth of more than 10 m below the water surface. In freshwater waters, this is to be used to refer to water that is in the area of the hypolimnion. Due to its low temperature and low oxygen content, deep water has a significantly higher capacity to dissolve oxygen compared to the water layers closer to the water surface.

The object of the invention is also achieved with a fish farm with the features of claim 6.

A fish farm, which is equipped with a net enclosure (also called “fish cage”) arranged in a body of water and with a device for oxygen enrichment, and in which the device for oxygen enrichment comprises a pipeline that runs at least in sections upwards and that has a lower mouth opening into the water immersed at a distance from the lower opening opening for compressed air leading into the pipeline, according to the invention is characterized in that an injection device connected via an oxygen supply line to an oxygen source for supplying oxygen to the pipeline is arranged in the region of the lower opening opening.

A “pipeline running upwards in sections” is to be understood here as a pipeline which has at least one geodetically extending section from bottom to top, for example vertically or obliquely, in which an upward flow can be generated by the supply of air according to the mammoth pump effect. The lower mouth opening preferably dips into a layer of water that is lower than the bottom (i.e. the lower boundary) of the net enclosure. For example, the lower mouth extends into the hypolimnion of the water. The pipeline opens out at an upper mouth opening of the pipeline, above or below the water surface, but above the network enclosure. Spaced below the compressed air supply, in particular in the area of the lower mouth opening, the injection device is arranged on the pipeline, through which, in addition to the compressed air, oxygen is introduced into the water passed through the pipeline.

The upward section of the pipeline - as seen in the direction of flow - preferably adjoins a section of the pipeline that runs essentially parallel to the water surface or is curved downward, which ends at the upper mouth opening of the pipeline, so the upper mouth opening is horizontally opposite the lower mouth opening offset. As a result, the extracted water can be directed into the area of the water surface above the enclosure, at the same time this arrangement ensures that the extracted water does not come from the area directly below the enclosure, which could be contaminated with waste products from the metabolism of the fish.

An advantageous embodiment of the device according to the invention is characterized in that the lower mouth opening of the pipeline opens out at a depth of at least 5 m, preferably at least 12 m below the water surface, in the latter case thus in the deep water of the water.

The supply for compressed air preferably opens into the pipeline at a depth of at most 5 m, preferably at most 2 m below the water surface of the water. This allows a comparatively weak pump to supply the air are used, which can also be supplied with power by a solar-powered unit installed on site, for example. The flow created in this way by introducing the air into an upper region of the pipeline through the mammoth pump effect is sufficient to convey the water from deeper layers of the water up through the pipeline.

In order to enable an intimate mixing of water and oxygen already within the injection device, an advantageous further development of the invention provides that the injection device comprises a mixing chamber into which a supply nozzle for oxygen and at least one supply opening for water opens and which via a discharge for Water-oxygen mixture, which is fluidly connected to the pipeline.

The mixing chamber can be designed in such a way that all the water conveyed through the pipeline passes through the injection device, which forms at least one supply opening for the water, i.e. the lower mouth opening of the pipeline, or in such a way that only a partial flow of the water flowing into the pipeline passes through the injection device is guided and mixes with the oxygen introduced there.

In particular, the supply nozzle for the oxygen can be designed as a Venturi nozzle, by means of which a strong flow of the oxygen introduced is achieved in the injection device, which flow is sufficient to draw ambient water through the supply openings for the water into the injection device.

An embodiment of the invention will be explained in more detail with reference to the drawing. The only drawing shows schematically a fish farm according to the invention.

In the 1 fish farm shown 1 includes one within a body of water 2nd , for example a lake, arranged net enclosure 3rd for receiving a fish stock, not shown here, and a device 5 for oxygenation.

The device 5 comprises an essentially L-shaped pipeline 6 with a first pipe section 7 , which in the exemplary embodiment shown here is essentially perpendicular to the water 2nd immersed and a second pipe section 8th , which is essentially at the level of the water surface 9 of the water 2nd and runs parallel to it and above the net enclosure 3rd at an upper mouth opening 10th the pipeline 6 flows out. The pipe section 8th can also be curved downwards and / or with a mouth opening pointing downwards 10th be trained.

The pipe section 7 opens with a lower mouth opening 11 in a deeper layer of the water 2nd out. The length of the pipe section 7 is chosen, for example, so that the lower mouth opening 11 into the deep water (hypolimnion) of the water 2nd protrudes into it, that is to say an oxygen-poor and comparatively cold (approx. 4 ° C.) water layer, but the invention is not restricted to this. For example, the mouth opening opens 11 approximately between 5 m and 12 m below the water surface 9 of the water 2nd out. The net enclosure 3rd is located in a layer of water above the hypolimnion and extends, for example, to a depth of 4-10 m below the water surface 9 down, but preferably not as deep as the lower mouth opening 11 the pipeline 6 .

In the area of the lower mouth opening 11 the pipeline 6 is an injection device 12th arranged to supply oxygen. The injection device 12th is via an oxygen supply 13 with an oxygen source 14 fluidly connected. For example, it is the oxygen source 14 a compressed gas cylinder or a bundle of compressed gas cylinders in which oxygen with a purity of 95% by volume is stored under pressure, for example 200 bar or 300 bar. To the pressure in the oxygen supply line 13 To be able to set a predetermined operating pressure is in the oxygen supply line 13 a pressure reducer 15 arranged.

The injection device 12th includes a mixing chamber 16 , in the one with the oxygen supply 13 flow-connected feed nozzle 17th flows in centrally for oxygen. Radial to this are a number of feeders 18th arranged for water in preferably equal angular sections. The mixing chamber also has 16 one with the pipeline 2nd flow-related diversion 19th for that in the mixing chamber 16 resulting water-oxygen mixture.

In the pipeline section 7 is above the injection device 12th , but below the water surface 9 , for example between 1 m and 3 m below, a feeder 21 arranged for compressed air. The feeder 21 for compressed air includes a perforated pipe section 22 in the pipeline 6 , the radially outside while maintaining an annular gap 23 from a piece of pipe 24th is enveloped. The pipe piece 24th is at both ends above and below the perforated pipe section 22 waterproof with the pipeline 6 connected. In the annular gap 23 opens an air supply 25th one connected to an air pump 26 connected. The air pump 26 is preferably driven electrically.

In operation of the device 5 becomes air by means of the air pump 26 via the air supply 25th and the feeder 21 into the pipeline 6 fed under an excess pressure of, for example, 0.3 bar. The resulting mixture of water and air has a much lower density than the surrounding water in the pipeline 6 , whereby within the pipe section 7 a strong, upward flow is generated (mammoth pump effect). The mixture of water and air passes through the pipe sections 7 and 8th and flows at the mouth opening 10th from the pipeline 6 out. From there it sinks into the area of the network enclosure due to its lower temperature than surface water 3rd from.

This is due to the mammoth pump effect at the lower mouth opening 11 the pipeline 6 sucked water is at the injection device 12th enriched with oxygen. To do this, oxygen comes from the oxygen source 14 via the oxygen supply 13 into the mixing chamber 16 initiated and there mixes intimately with water through the feeds 18th into the mixing chamber 16 flows in. The mixture of water and oxygen enters the pipeline 6 and becomes with the flow of the rest, over the mouth opening 11 supplied water entrained. Due to the intensive mixing of the oxygen with the water and the comparatively long common flow path, a considerable part of the oxygen is dissolved in the water. That at the mouth opening 10th escaping water is therefore highly enriched with oxygen and has a proportion of dissolved oxygen which is, for example, 5-7 mg / l above the oxygen content of the mouth 11 inflowing water.

Reference list

1

Fish farm

2nd

Waters

3rd

Net enclosure

4th

-

5

contraption

6

Pipeline

7

Pipe section

8th

Pipe section

9

Water surface

10th

Upper mouth opening

11

Lower mouth opening

12th

Injection device

13

Oxygen supply

14

Oxygen source

15

Pressure reducer

16

Mixing chamber

17th

Feed nozzle for oxygen

18th

Water supply

19th

Diversion

20

-

21

Supply for compressed air

22

perforated pipe section

23

Annular gap

24th

Pipe piece

25th

Air supply

26

Air pump

Claims (9)

Process for the oxygenation of water in a fish farm, in which a fish stock is kept in a net enclosure (3) within a body of water (2) and water from a deeper layer of the body of water (2) into the area of the water surface (9), above the net enclosure (3 ) is promoted by water flowing into a lower mouth opening (11) of a pipeline (6) running at least in sections upwards within the water, the water flowing into the pipeline (6) with above the lower mouth opening (11) but below the water surface ( 9) mixed with the supplied air and thereby an upward flow is generated in the pipeline (6), characterized in that the water flowing through the pipeline (6) flows into the pipeline (6) in the region of the lower mouth opening (11). opening injection device (12) oxygen from an oxygen source (14) is supplied. Procedure according to Claim 1 , characterized in that a mixture of water and oxygen is fed into the pipeline (6) at the injection device (12). Procedure according to Claim 2 , characterized in that oxygen is introduced into the injection device (12) and water is drawn into the injection device (12) from the body of water (2) due to the flow generated thereby. Method according to one of the preceding claims, characterized in that the oxygen into the pipeline (6) with an overpressure of at least 3 bar, preferably at least 5 bar. and / or is entered in the injection device (12). Method according to one of the preceding claims, characterized in that deep water of the water (2) is conveyed through the pipeline (6). Fish breeding plant, with a network enclosure (3) arranged in a body of water (2) and with a device (5) for oxygen enrichment, the device (5) for oxygen enrichment comprising a pipeline (6) running at least in sections, which has a lower mouth opening ( 11) dips into the water (2) and at which a feed (21) for compressed air opens into the pipeline (6) at a distance from the lower mouth opening (11), characterized in that on the pipeline (6), below the feed ( 21) for compressed air, an injection device (12) which is flow-connected via an oxygen feed line (13) to an oxygen source (14) and is used to supply oxygen to the pipeline (6). Fish farm after Claim 6 , characterized in that the lower mouth opening (11) of the pipeline (6) opens out at a depth of at least 5 m, preferably at least 12 m below the water surface (9) of the water (2). Fish farm after Claim 6 or 7 , characterized in that the supply (21) for compressed air opens into the pipeline (6) at a depth of at most 5 m, preferably at most 2 m below the water surface (9) of the water (2). Fish farm according to one of the Claims 6 to 8th , characterized in that the injection device (12) comprises a mixing chamber (16) into which a supply nozzle (17) for oxygen and at least one supply opening (18) for water open, and via an outlet (19) for a water-oxygen -Mixed with the pipeline (6).

Images