CA2075442A1

CA2075442A1 - Fish breeding system with separate breeding and sedimentation tanks

Info

Publication number: CA2075442A1
Application number: CA002075442A
Authority: CA
Inventors: Jean-Claude Desrosiers; Christian Gosselin; Michel Brouillard
Original assignee: AQUA-BIOTOPE Inc
Current assignee: AQUA-BIOTOPE Inc
Priority date: 1992-08-06
Filing date: 1992-08-06
Publication date: 1994-02-07

Abstract

ABSTRACT OF THE DISCLOSURE

The system comprises breeding and sedimentation tanks both made of flexible material impervious to solid wastes. The fish breeding tank is lowered in a body of water and comprises a bottom outlet connected to an inlet of the sedimentation tank, also comprising an outlet. The sedimentation tank is immersed in the body of water beneath the breeding tank. Floatation members maintains an upper portion of the breeding tank above the level of water in the body, this upper breeding tank portion defining a top opening. Water is supplied to the breeding tank through the top opening to form a water head that causes a flow of water from the breeding tank to the sedimentation tank. Water is flowing downwardly in the breeding tank to efficiently carry solid wastes from the breeding tank to the sedimentation tank, where they settle to the bottom. The upper portion of the breeding tank is of smaller cross sectional area to reduce the volume of water in this tank above the level of water in the body and thereby reduce the load supported by the floatation members. The water supplied to the breeding tank is preferably pumped from the body at a deepness where the temperature is optimal for fish growth. A major advantage of the system is that sedimentation is carried out in a tank separate from the breeding tank whereby contamination of the fish by solid pollutants is minimized.

Description

207~2 FISH BREEDING SYSTEM WITH SEPARATE

BREEDING AND SEDIMENTATION TANKS

BACKGROUND OF THE INVENTION
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1. Field of the invention:
'~ The present invention relates to a system for breeding fish, comprising separate breeding and sedimentation tanks. A flow of water from the breeding to the sedimentation tank is produced. Water 20 is flowing downwardly in the breeding tank to efficiently carry solid wastes from the breeding to the sedimentation tank where they settle to the bottom.
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25 2. Brief descrition of the prior art:

Nowadays, many countries are experiencing a shortage in fish supply. To counter this situation, fishermen are turning their interest to fish breeding, 30 whether in net pens, in raceways or other reservoirs on land or in water.
, l However, intensive fish breeding using net I pens in marine or lake environments, has a major 1 35 drawback: organic solid wastes produced by the fish `l and unused food accumulate at the bottom of the ~ exploited water body. In a relatively short period of ,., .s .

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207~442 time depending on the size of the installation, this accumulation of solid wastes creates a negative impact on the immediate environment of each fish farming plant. Over a longer period of time, problems on a larger scale can be generated.

This negative impact on the environment results in the degradation of the exploited sites, which become polluted and unsuitable for fish breeding. Each site also becomes a menace for the local ecosystem. This happens when nature is no longer capable of recycling all the organic wastes coming from the fish farming activities.

~, 15- Thus, it is necessary to avoid, as much i as possible, releasing the solid wastes produced by intensive fish breeding in net pens into the ecosystem. To reach this objective, the conventional net of the net pens must be replaced by a material that is impervious to solid wastes. A closer control of the wastes is then enabled, with the additional advantage of also enabling control of the breeding ~!i parameters (mainly the temperature). Moreover, the 3~ added treatment products are no longer able to go adrift.

Such a fish breeding system is disclosed in United States patent N 4,711,199 granted to Nyman on December 8, 1987. This fish breeding system includes a tank made of non-rigid material impervious to solid wastes. This tank is lowered into a body of water and includes a water inlet as well as a water outlet. These inlet and outlet are positioned to . . .
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produce a generally horizontal flow of water and are so dimensioned that the water level in the tank is , somewhat above the surrounding level of the water body to maintain the wall of the tank in a tightened out position by the higher static pressure in the tank.
A device for collecting sludge is provided at the bottom of the tank.
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In the system of Nyman (United States patent N 4,711,199), a single tank is used both as fish breeding tank and as sedimentation tank. In this type of system, agitation of the water created by the ~; movements of the fish will allow solid waste particles to flow through the outlet in the surrounding water `~15 body. Noreover, pathogenic agents that thrive in the sludge accumulated in the bottom collecting device can find their way toward the fish breeding tank and affect the health and growth of the fish.
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;1An object of the invention is therefore to eliminate the above discussed drawbacks of the `prior art.
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Another object of the present invention $ is to provide a system for breeding fish comprising 330 separate breeding and sedimentation tanks. Water ~'flows downwardly in the breeding tank to efficiently ',carry the solid wastes from the breeding tank to the ,sedimentation tank.

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SUMMARY OF THE INVENTION

The present invention is concerned with a fish breeding system, comprising a fish breeding i tank having a first top water inlet and a first bottom -, water outlet, and a sedimentation tank having a second water inlet and a second water outlet, the first bottom water outlet and the second water inlet being interconnected through conduit means. Means are also provided to supply water to the breeding tank through the first top water inlet and to cause a flow of water 1~; through the breeding tank, the first bottom water outlet, the conduit means, the second water inlet, the sedimentation tank, and the second water outlet, water flowing downwardly in the breeding tank from the first top water inlet to the first bottom water outlet.

20In operation, the flow of water carries ~,~ solid wastes from the breeding tank to the sedimentation tank, where they settle to the bottom to form a sludge.

25As water flows downwardly in the breeding tank, the solid wastes are efficiently transferred from the breeding tank to the sedimentation tank.
Also, the sedimentation tank is separate from the breeding tank, and the flow of water in the conduit means from the first bottom water outlet to the second water inlet prevents any solid particles in the sedimentation tank from returning in the breeding tank.

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2~754~2 The sedimentation tank is advantageously -~ provided with a plurality of bottom depressions to : concentrate and accumulate the sludge at a common outlet. The bottom depressions increase the surface ` 5 area for settling and decrease the depth of the sedimentation tank needed for sludge concentration and ~ evacuation.

:, In accordance with a preferred embodiment : lo of the present invention, there is provided a fish breeding system installed in a body of water, and

3~ comprising:

a fish breeding tank lowered in the body of water, this breeding tank comprising an upper portion situated above the level of water of the body ~: and provided with a top opening, the breeding tank further comprising a first bottom water outlet;
, a sedimentation tank immersed in the body of water, and having a water inlet and a second water :~ outlet;

. conduit means for interconnecting the first bottom water outlet of the breeding tank and the . water inlet of the sedimentation tank;

means for supplying water to the breeding tank through the top opening and for creating and .¦ 30 maintaining in the breeding tank a level of water ~J higher than the water level of the body to thereby .~ pressurize the breeding tank and cause a flow of water through the breeding tank, the first bottom water ;~.
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2~7~42 outlet, the conduit means, the water inlet, the sedimentation tank, and the second water outlet, water flowing downwardly in the breeding tank from the top opening to the first bottom water outlet.

In operation, the flow of water carries solid wastes from the breeding tank to the sedimentation tank, the sedimentation tank being capable of containing a volume of water large enough to retain the water coming from the breeding tank during a time period sufficient to allow the solid wastes to settle to the bottom of the sedimentation tank and form a sludge.

1~ In accordance with another preferred embodiment of the present invention, the level creating and maintaining means comprises floatation means floating at the surface of the water body and attached to the breeding tank to support it at a predetermined level in the body of water, and the upper portion of the breeding tank is of smaller cross sectional area whereby the volume of water in the breeding tank above the water level of the body is smaller to thereby reduce the load supported by the floatation means.

In accordance with other preferred embodiments of the fish breeding system, (a) the breeding and sedimentation tanks are made of flexible material impervious to solid wastes, (b) it comprises first throttle means mounted on the first bottom water inlet to control the pressure and the flow of water in the fish breeding tank, and second throttle means .: -: .

2075~2 mounted on the second water outlet to control the pressure and the flow of water in the sedimentation tank, and (c) the water supplying means comprises means for pumping water from the body at a deepness where the temperature of water is optimal for fish growth.

Also, the fish breeding system may comprise a plurality of breeding tanks all connected to a common sedimentation tank, as will be described hereinafter.
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~ The objects, advantages and other features .31 of the present invention will become more apparent upon reading of the following non restrictive description of a preferred embodiment thereof, given by way of example only with reference to the accompanying drawings.

~ 20 ;, BRIEF DESCRIPTION OF THE DRAWINGS

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?~ In the appended drawings:
' 25 :d Figures 1 and 2 are respectively side '!~ elevational and plan view of a fish breeding system in , accordance with the present invention, comprising a ~, set of four breeding tanks and one sedimentation tank.

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Referring now to Figures 1 and 2 of the appended drawings, the fish breeding system in accordance with the present invention is generally identified by the reference numeral 1.

The fish breeding system 1 comprises four tanks 2a, 2b, 2c and 2d, containing the bred fish. As illustrated in Figure 1, the breeding tanks 2a - 2d are lowered in a body of water 4, for example the water of a lake or any other natural or artificial water reservoir. Each breeding tank 2a - 2d has an upper portion situated above the level 5 of the water body 4. The emerging upper portions of the breeding tanks 2a, 2b, 2c and 2d open upwardly to form top openings 3a, 3b, 3c and 3d, respectively. Figure 1 also shows the inverted conical shape of the bottom of each tank 2a, 2b, 2c and 2d.

An horizontal main water supply line 6 is ' lowered in the body of water 4 at a depth where the i temperature is optimal for fish growth. Thermal stratification of the bodies of water in temperate or ~; cold regions enables such depth selection. Line 6 has an open end 6a through which water at optimal temperature is collected. A first pump 7 sucks water through the horizontal line 6 and a vertical water , 30 supply line 8 and supplies this water to the breeding tank 2a through another water supply line 9 and the top opening 3a. In the same manner, a pump 10 sucks water through line 6 and through a vertical water ,, , "~

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. supply line 11 and supplies this water to the breeding tank 2b through another line 12 and the top opening 3b. A third pump 13 sucks water through the horizontal water supply line 6 and a vertical water supply line 14 and supplies this water to the breeding tank 2c through a further water supply line 15 and the top opening 3c. Finally, a fourth pump 16 sucks water ~: through line 6 and vertical water supply line 17 and supplies this water to breeding tank 2d through an 0 additional water supply line 18 and top opening 3d.
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-, The water supply lines 9, 12, 15 and 18 have respective open free ends (see for example 19 in - Figure 1) placed at a given height above the level of ~ 15 water (see for example 20 in Figure 1) in the ., corresponding breeding tanks 2a, 2b, 2c and 2d. The water in the breeding tanks is therefore oxygenated by ; dropping the supplied water from a given height.
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The fish breeding system 1 further comprises a sedimentation tank 21 immersed in the body ~ of water 4 beneath the fish breeding tanks 2a - 2d.
x~ The sedimentation tank 21 can also be disposed laterally with respect to the breeding tanks 2a - 2d.
Conduits 22a, 22b, 22c and 22d respectively interconnect a bottom water outlet of the breeding tanks 2a, 2b, 2c and 2d with peripheral top water inlets 210a, 210b, 210c and 210d of the sedimentation tank 21. The tank 21 comprises a top, central water ~' 30 outlet 24 and is formed with a set of four bottom depressions 32, 33, 34 and 35 in which the sludge ~ concentrates and accumulates. The bottoms of these :~ generally conical or pyramidal depressions 32 - 35 are .~ :

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connected to a common bottom sludge outlet 25 though conduits 36, 37, 38 and 39, respectively.

Alternatively, the lower end of the ; 5 conduits 22a - 22d may be connected to a top, central diffusion area (not shown) of the sedimentation tank 21. This area diffuses the water from the breeding tanks 2a - 2d in the volume of the sedimentation tank 21. The top water outlet 24 is then replaced by a plurality of peripheral top water outlets (not shown).

Throttle devices 23a, 23b, 23c and 23d (Figures 1 and 2) are installed on the bottom water outlet of the breeding tanks 2a, 2b, 2c and 2d, respectively. Another throttle device 26 is mounted on the top water outlet 24 of the sedimentation tank 21. As an example, the throttle devices 23a - 23d, as well as the throttle device 26 may be formed by adjustable valves.

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Floatation members such as 27 and 28 (Figure 1) maintain the breeding tanks 2a - 2d at the desired level in the body of water 4, while floatation ~ members such as 29 (Figure 1) maintain the - 25 sedimentation tank 21 at the desired depth.

, Operation of the fish breeding system 1 will now be described.
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The volume of water pumped by time unit ~ by each pump 7, 10, 13 and 16 and each valve 23a, 23b, ;~ 23c and 23d are adjusted to create and maintain in the breeding tanks 2a - 2d a water head. Indeed, the . .

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: ,, - ~ : . :: :. - , . .:, - , ,, :: .. , - , . , 2~75~42 level 20 (see Figure 1) of water in the tanks 2a - 2d is higher than the level 5 of water 4 of the lake or other natural or artificial water reservoir. This water head creates a positive pressure that maintains the breeding tanks 2a - 2d in a turgid state and that causes a downward flow of water in these breeding tanks, the valves 23a - 23d, the conduits 22a - 22d, the sedimentation tank 21, the water outlet 24 and the valve 26. The water head is selected to create a downward flow of water sufficient to carry the solid wastes, including pathogenic agents, from the breeding tanks 2a - 2d toward the sedimentation tank 21. The inverted conical shape of the bottom of the breeding tanks 2a -2d directs all the solid waste particles through the conduits 22a - 22d. It will appear to those skilled in the art that the downward movement of water in the breeding tanks 2a - 2b and the conduits 22a - 22d prevents any movement of the solid wastes, including pathogenic agents, toward the breeding tanks ~` 20 to possibly contaminate the fish.
:' The polluted water is treated by sedimentation of the solid waste particles in the sedimentation tank 21. This sedimentation tank is large enough to retain the water from the breeding tanks 2a - 2d during a time period sufficient to allow the solid wastes to settle to the bottom of the depressions 32 - 35 and form a sludge, when water in all the breeding tanks 2a - 2d is flowing at maximal ~ 30 rates. Water treated in the sedimentation tank 21 .~
escapes through the outlet 24. The valve 26 is adjusted to control the pressure in the sedimentation tank 21 to a level capable of maintaining this tank 21 , :i -x .... ..
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2~7~4~2 in a turgid state. To enable separate control of the different breeding tanks 2a - 2d, the pressure in the sedimentation tank 21 must obviously be lower than the pressure in all the breeding tanks. When required, s the sludge accumulated on the bottom of the depressions 32 - 35 of the sedimentation tank 21 can be pumped through the conduits 36 - 39 and the bottom sludge outlet 25.

It should also be noted that gaseous substances that form in the sedimentation tank 21 are continuously evacuated through the top, central water outlet 24.

Of course, the breeding 2a - 2d and sedimentation 21 tanks are made of material impervious to solid wastes. This material is advantageously - flexible and can comprise for example plastic.

As illustrated in Figures 1 and 2, the breeding tanks 2a - 2d are generally cylindrical with an inverted conical bottom. Their upper portions are also cylindrical but have a smaller diameter. This substantially reduces the volume and weight of the water head in the breeding tanks, whereby the size of the floatation members such as 27 and 28 (Figure 1) required to support the breeding tanks can also be greatly reduced. More specifically, the weight of the water head is reduced by a factor that is the square ; 30 of the ratio of the diameter of the breeding tanks to the diameter of their upper portions (e.g. for a ratio of two, the weight of the water head is divided by 4).
It should be pointed out here that the hydrostatic ''' , ~ . . - . . .
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.. :....... ,. ~. ~ . ~ -, paradox enables reduction of the diameter of the upper portions of the breeding tanks without reducing the efficiency of the system. In accordance with this paradox, the pressure over a surface in a liquid is function of the height of liquid over this surface, not of the total volume of liquid over it.

Respective grids, such as 30a and 30b (Figure 1), are installed on the bottom of the breeding tanks 2a - 2d to prevent live fish from passing through the conduits 22a - 22d. Dead fish accumulating on the grids such as 30a and 30b are flushed through the conduits 22a - 22d in the -~ sedimentation tank 21 by lifting, in a known manner, a gate (not shown) located centrally of each grid such as 3Oa and 3Ob.

The water outlet 24 of the sedimentation tank 21 is fitted with a screen 31 to prevent live fish from entering the environment (creating the danger of modifying the genetic quality of the indigenous species) in the event that some fish escape the breeding tanks 2a - 2d when a flush of dead fish is accomplished by lifting the central gates of the different grids such as 30a and 30b (Figure 1).

ji As illustrated in Figure 1, the top water ;~ outlet 24 of the sedimentation tank 21 opens upwardly and is situated beneath the breeding tanks 2a - 2d.
The treated water coming out of the outlet 24 of the sedimentation tank 21, having a temperature of about 4C, is therefore directed around the breeding tanks 2a - 2d and around the floatation members such as 27 ,,' .
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2~7~2 and 28 to thereby prevent ice formation during winter under temperate and cold climates.

The present invention presents, amongst others, the following advantages:

- the principal advantage results, as indicated in the preamble of the present specification, from the use of a separate tank (sedimentation tank 21) for the recovery of the solid wastes;

- the water flow carries these pollutants away from the fish;
- fish growth in temperate and cold regions is the best possible because water is pumped at a depth where its temperature is optimal (summer) or best (winter);
- the smaller diameter of the upper portions of the breeding tanks reduces the required buoyancy, thereby reducing the cost of the system;
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25- ice formation during winter can be prevented by directing the flow of treated water from the outlet 24 at 4C around the breeding tanks and their floatation members;

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30- tanks of flexible material are inexpensive to construct and operate;

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2~75442 - investment and operating costs are minimal for a maximal efficiency in fish growth and pollution control.

Although the present invention has been described hereinabove by way of a preferred embodiment thereof, this embodiment can be modified at will, within the scope of the appended claims, without departing from the spirit and nature of the present lnv-ntion.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fish breeding system, comprising:
a fish breeding tank having a first top water inlet and a first bottom water outlet;
a sedimentation tank having a second water inlet and a second water outlet;
conduit means for interconnecting said first bottom water outlet of the breeding tank and said second water inlet of the sedimentation tank;
means for supplying water to the breeding tank through said first top water inlet and for causing a flow of water through the breeding tank, the first bottom water outlet, the conduit means, the second water inlet, the sedimentation tank, and the second water outlet, water flowing downwardly in the breeding tank from the first top water inlet to the first bottom water outlet;
whereby, in operation, the flow of water carries solid wastes from the fish breeding tank to the sedimentation tank, said solid wastes settling to the bottom of the sedimentation tank to form a sludge.

2. A fish breeding system as recited in claim 1, further comprising:
first means for controlling the pressure and the flow of water in said fish breeding tank; and second means for controlling the pressure and the flow of water in said sedimentation tank.

3. A fish breeding system as recited in claim 2, wherein said first controlling means comprises throttle means mounted on the water outlet of the fish breeding tank, and wherein said second controlling means comprises throttle means mounted on the water outlet of the sedimentation tank.

4. A fish breeding system installed in a body of water, comprising:
a fish breeding tank lowered in the body of water, said breeding tank comprising an upper portion situated above the level of water of said body and provided with a top opening, said breeding tank further comprising a first bottom water outlet;
a sedimentation tank immersed in said body of water, said sedimentation tank having a water inlet and a second water outlet;
conduit means for interconnecting said first bottom water outlet of the breeding tank and said water inlet of the sedimentation tank;
means for supplying water to the breeding tank through said top opening and for creating and maintaining in said breeding tank a level of water higher than said water level of the body to thereby pressurize the breeding tank and cause a flow of water through the breeding tank, the first bottom water outlet, the conduit means, said water inlet, the sedimentation tank, and the second water outlet, water flowing downwardly in the breeding tank from said top opening to said first bottom water outlet;
whereby, in operation, the flow of water carries solid wastes from the breeding tank to the sedimentation tank, said sedimentation tank being capable of containing a volume of water large enough to retain the water coming from the breeding tank during a time period sufficient to allow said solid wastes to settle to the bottom of the sedimentation tank and form a sludge.

5. A fish breeding system according to claim 4, in which said upper portion of the fish breeding tank is of smaller cross sectional area and opens upwardly to form said top opening.

6. A fish breeding system according to claim 4, wherein said level creating and maintaining means comprises floatation means floating at the surface of the water body and attached to the breeding tank to support said fish breeding tank at a predetermined level in the water of said body, and wherein said upper portion of the breeding tank is of smaller cross sectional area whereby the quantity of water in the breeding tank above said water level of the body is smaller to thereby reduce the load supported by said floatation means.

7. A fish breeding system according to claim 6, wherein said breeding and sedimentation tanks are made of flexible material impervious to said solid wastes.

8. A fish breeding system according to claim 4, further comprising:
first means for controlling the pressure and the flow of water in said fish breeding tank; and second means for controlling the pressure and the flow of water in said sedimentation tank.

9. A fish breeding system according to claim 8, wherein said first controlling means comprises throttle means mounted on the bottom water outlet of the fish breeding tank, and wherein said second controlling means comprises throttle means mounted on the second water outlet of the sedimentation tank.

10. A fish breeding system according to claim 4, wherein said second water outlet of the sedimentation tank is a top water outlet whereby gaseous substances produced in the sedimentation tank escape through said second outlet.

11. A fish breeding system according to claim 10, wherein said sedimentation tank is located beneath said fish breeding tank and wherein said second top water outlet is positioned on said sedimentation tank to direct the water escaping from the sedimentation tank through said second outlet around the breeding tank to prevent ice formation during winter.

12. A fish breeding system according to claim 10, wherein said sedimentation tank further comprises a bottom sludge outlet to enable evacuation of the sludge accumulated on the bottom of said sedimentation tank.

13. A fish breeding system according to claim 4, in which said water supplying means comprises means for pumping water from said body at a deepness where the temperature of water is optimal for fish growth.

14. A fish breeding system according to claim 13, in which said water supplying means comprises means for dropping water in the breeding tank in order to oxygenate water in said fish breeding tank.

15. A fish breeding system according to claim 4, comprising a plurality of fish breeding tanks lowered in the water of said body and each provided with a bottom water outlet, said sedimentation tank comprising a plurality of water inlets respectively connected to the bottom water outlets of the breeding tanks through respective conduit means.

16. A fish breeding system as recited in claim 1, wherein said sedimentation tank comprises a plurality of bottom depressions for concentrating and accumulating the sludge.

17. A fish breeding system as recited in claim 16, in which said depressions each comprise a bottom sludge outlet connected to a common sludge outlet through a respective conduit.

18. A fish breeding system according to claim 4, wherein said sedimentation tank comprises a plurality of bottom depressions for concentrating and accumulating the sludge.

19. A fish breeding system according to claim 18, in which said depressions each comprise a bottom sludge outlet connected to a common sludge outlet through a respective conduit.