JP2015023841A - Circulation cleanup process and apparatus of breeding water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process suitable for high performance circulation cleanup for breeding water of a display aquarium.SOLUTION: In a process for circulation cleanup and clarification of breeding water through a filtration process, the filtration process has a biofouling carrier layer filled with a biofouling carrier other than sand with a filling thickness of more than 200 mm in the upper part, and a sand layer filled with sand with a filling thickness of more than 400 mm in the lower part. Breeding water passes through the bilayer filtration layer that the total of the filling thickness of the biofouling carrier layer and the sand layer is 600-1200 mm in a filtering rate of more than 20 m/h in descending current.

Description

  The present invention relates to a method and apparatus for purifying and clarifying breeding water, in particular, aquatic aquarium water such as fish.

  Conventionally, in order to purify and clarify exhibition water tanks such as aquariums, slow filtration or rapid filtration using sand or the like has been adopted. A small aquarium with shallow water circulates the aquarium water through a sand layer spread at the bottom of the aquarium, and purifies and clarifies it by purification action by microorganisms in the sand and physical filtration action by sand.

  On the other hand, large aquarium water with deep water is purified and clarified by a rapid filtration device installed near the aquarium. In the aquarium, a purification device is installed behind the exhibition zone, but due to area restrictions, it is common to use rapid filtration that can increase the amount of treated water per installation area for large aquariums. . There are two types of rapid filtration: vertical and horizontal. However, when there are spatial restrictions such as height restrictions, a horizontal installation that can increase the filtration area per unit is also adopted.

  In order to maintain the health of aquatic organisms, purification of the aquarium water in the exhibition tank is important, but clarification to ensure the transparency of the aquarium water is also extremely important for viewing aquatic organisms. Clarifying the breeding water in the aquaculture tank is important for monitoring the growth status of fish and early detection of moribund fish. Sand filtration is frequently used for rapid filtration.

  In recent years, large-scale fish tanks such as shark flat sharks, tuna fish, and many types of tanks have become huge, and the area and space required for purification facilities are limited. It has been.

  For example, Japanese Patent Application Laid-Open No. 2009-172469 discloses a water treatment apparatus used for the treatment of breeding water for creatures such as fish and shellfish. In the gazette, for the purpose of efficiently treating a trace amount of ammonia nitrogen and other harmful components, the first micro / nano bubble generator is disposed in the vicinity of the filter medium part having a filtration function, and the water treated in the filter medium part, It has been proposed that water containing micro-nano bubbles generated by the first micro-nano bubble generator is mixed and supplied to a breeding aquarium used for breeding creatures.

JP 2009-172469 A

  However, Patent Document 1 does not sufficiently consider the configuration of the filter medium itself and the optimization of operation conditions, and there is still room for improvement for highly efficient circulation purification of the exhibition aquarium water.

  The present invention was created in view of the above circumstances, and an object of the present invention is to provide a method suitable for circulating and purifying breeding water such as display aquarium water with high efficiency. Another object of the present invention is to provide an apparatus suitable for circulating and purifying breeding water with high efficiency. Furthermore, another object of the present invention is to provide a breeding water circulation purification system including a water tank and a device according to the present invention.

  The present inventor has intensively studied to solve the above-mentioned problems.The filter medium has a multi-layer structure in which the bioadhesive carrier layer is filled in the upper part and the sand layer is filled in the lower part. It was found that speeding up is effective.

  The present invention has been completed on the basis of the above knowledge, and in one aspect, the breeding water is a method of circulating purification and clarification through a filtration step, and the filtration step is filled with a bioadhesive carrier other than sand at a thickness of 200 mm. A bioadhesive carrier layer filled as described above and a sand layer filled with sand at a thickness of 400 mm or more at the bottom, and a total of the filling thickness of the bioadhesive carrier layer and the sand layer is 600 mm to 1200 mm. It is a method including passing the breeding water through the layer filtration layer in a downward flow at a filtration rate of 20 m / hour or more.

  In one embodiment of the method according to the invention, the ratio of the bioadhesive carrier layer filling thickness to the sand layer filling thickness is 0.2-0.7.

  In another embodiment of the method according to the present invention, the bioadhesive carrier is activated carbon and / or anthracite.

  In another aspect, the present invention is an apparatus for circulating and purifying breeding water, comprising a multi-layer filtration layer for passing the breeding water in a downward flow having a filtration rate of 20 m / hr or more, and comprising a multi-layer filtration. The layer has a bioadhesive carrier layer other than the upper sand having a filling thickness of 200 mm or more and a lower sand layer having a filling thickness of 400 mm or more, and the sum of the filling thickness of the bioadhesion carrier layer and the sand layer is 600 mm to It is a device that is 1200 mm.

  In one embodiment of the device according to the invention, the ratio of the filling thickness of the bioadhesive carrier layer to the filling thickness of the sand layer is 0.2 to 0.7.

  In another embodiment of the apparatus according to the present invention, the bioadhesive carrier is activated carbon and / or anthracite.

  In still another aspect of the present invention, a water tank and the apparatus according to the present invention are provided, and breeding water discharged from the water tank flows into the multilayer filtration layer of the apparatus, and the filtered water discharged from the apparatus is It is a breeding water circulation purification system in which both are connected to be sent back to the aquarium.

  In one embodiment of the system according to the present invention, the breeding water discharged from the aquarium is configured to flow into the multilayer filtration layer of the apparatus via the aeration tank.

  By using the breeding water circulation purification method and apparatus according to the present invention, breeding water can be circulated and purified with high efficiency. Therefore, for example, while the purification device is made compact, it is possible to maintain the ammonia nitrogen concentration in the breeding water at a low level and maintain good water quality, so that the present invention is an aquarium with limited installation space. Is extremely effective.

An example of the flow sheet of the circulation purification system of breeding water concerning the present invention is shown. It is a graph which shows the thickness of the sand layer in an Example, and the relationship between transparency. It is a graph which shows the relationship between the filtration rate and the amount of nitrification in an Example. It is a graph which shows the relationship between the filtration rate in the Example, and the ammonia nitrogen concentration of inflow water and effluent water. It is a graph which shows the relationship between the thickness of the activated carbon layer in an Example, and the ammonia nitrogen concentration of exhibition aquarium water.

<1. Circulation purification method>
In one aspect, the present invention is directed to a method for circulating and purifying breeding water through a filtration step. Although it is not limited as breeding water, for example, aquarium water such as an exhibition tank, aquaculture tank, live fish tank, etc., it is typical to use exhibition tank water that requires high clarity as breeding water. . The exhibition tank is a facility for visitors to observe aquatic organisms kept in aquariums. The aquatic organisms to be bred are not particularly limited, and examples include seafood, crustaceans, marine mammals, aquatic plants, seaweeds and the like. Further, it may be aquatic organisms living in fresh water or aquatic organisms living in seawater. Therefore, the breeding water to be circulated may be fresh water or sea water.

  In the filtration step, water containing urea excreted by aquatic organisms flowing out from the breeding aquarium and ammonia generated by decomposition of the residual feed is purified and returned to the breeding aquarium. The rearing tank water circulates between the rearing tank and the filtration process. The present inventor has intensively studied a method for efficiently carrying out the circulation purification of breeding aquarium water through such a filtration step, and it is very effective to combine the structure of the filtration layer and the filtration rate in the filtration step under specific conditions. I came to find out.

  First, it is important that the filtration layer is a multi-layer filtration layer having a bioadhesive carrier layer other than sand and a sand layer. While it is not excluded to incorporate other filtration layers, these two layers are typically placed one above the other. Nitrifying bacteria are attached to the bioadhesive carrier layer, and ammonia nitrogen in the water is oxidized to nitrous acid and nitric acid under aerobic conditions while the breeding aquarium water passes through the bioadhesive carrier layer. However, the bioadhesive carrier has a low ability to clarify water. On the other hand, the sand layer has a high ability to clarify water mainly by physical filtration, but its ability to nitrify by microorganisms is limited.

  Therefore, considering only the viewpoint of clarifying and purifying the breeding aquarium water, it is only necessary to increase the thickness of the bioadhesive carrier layer and the sand layer as much as possible, but increasing the thickness increases the loss head, There is a problem that the load on the pump for circulating the breeding aquarium water becomes excessive. Moreover, in the aquarium, which is a typical installation location for breeding aquarium water, a purification device is provided on the back side of the exhibition zone. However, since the space for installation is limited, the thickness of the filtration layer is also limited. Therefore, it is preferable that the total thickness of the bioadhesive carrier layer and the sand layer is small.

  As the bioadhesive carrier, bioadhesive carriers known to those skilled in the art can be used without limitation, and examples include minerals such as anthracite, activated carbon (especially spherical or granular activated carbon), ceramic, synthetic resin, zeolite, and the like. . The bioadhesive carrier can take various shapes such as spherical, granular, tubular, honeycomb, porous to increase the surface area. Among these, anthracite, activated carbon, and zeolite are preferable in terms of high bioadhesion ability, and a granular or spherical carrier shape that can be easily backwashed is preferable. In the case of a granular or spherical carrier, the particle size is preferably 0.4 to 1.2 mm, more preferably 0.5 to 0.8 mm.

  The present inventor has examined conditions for achieving water transparency and ammonia nitrogen concentration required for breeding aquarium water with a minimum filtration layer thickness. The bioadhesive carrier layer on the upper side and the sand layer on the lower side. The bioadhesive carrier layer has a filling thickness of 200 mm or more, preferably 300 mm or more, and the sand layer has a filling thickness of 400 mm or more, preferably 500 mm or more, provided that the breeding aquarium water is passed through the multi-layer filtration layer with a downward flow. If so, it was found that good water quality can be maintained by circulating purification.

  Moreover, it is important that the thickness of the bioadhesive carrier layer with respect to the thickness of the sand layer satisfies 0.2 to 0.7 in order to maintain good filtration performance while suppressing the overall thickness of the multilayer filtration layer. I found out that

  In order to maintain the ammoniacal nitrogen concentration in the breeding aquarium water in a desirable state, it is important to ensure a sufficient amount of nitrification by increasing the filtration rate (LV). Specifically, in the filtration step, it is important to pass the breeding aquarium water through the multi-layer filtration layer with a downward flow having a filtration rate of 20 m / hour or more. This is because breeding aquarium water is used for circulation purification, and the total purification capacity of the circulation purification system is more important than temporary treatment water quality. Since the amount of nitrification is further increased by increasing the filtration speed, the filtration speed is preferably 25 m / hour or more, more preferably 30 m / hour or more.

  However, when the filtration rate is 20 m / hour or more, the increase rate of the nitrification amount relative to the increase rate of the filtration rate is not so large. That is, the effect of increasing the speed is saturated. Further, when the filtration rate is increased, the load on the water circulation pump also increases. Therefore, the filtration rate is preferably 50 m / hour or less, more preferably 40 m / hour or less.

  According to the circulation purification method according to the present invention, it is possible to maintain a good quality of the breeding aquarium water while the total thickness of the bioadhesive carrier layer and the sand layer is 1200 mm or less. Considering the loss head, it is preferably 1000 mm or less, and more preferably 800 mm or less.

  In order to sufficiently supply oxygen necessary for nitrification, it is preferable to raise the dissolved oxygen concentration of the breeding tank water that has flowed out of the breeding tank before passing through the filtration step.

<2. Circulation Purification System>
FIG. 1 shows a flow sheet of an example of a circulation purification system for breeding aquarium water according to the present invention. The circulation purification system includes a breeding water tank 1 and a circulation purification device 5, and the breeding water discharged from the breeding water tank 1 flows into the multi-layer filtration layer 12 of the circulation purification device 5, and the filtered water discharged from the device 5. Are connected to each other so as to be sent back to the breeding tank 1.

  Although there is no restriction | limiting in particular as a structure aspect of the circulation purification apparatus 5, For example, a tank, a tower, a column, a cylinder, etc. can be considered. More specifically, a known shape such as a rectangular parallelepiped shape, a cubic shape, a cylindrical shape, and a tower shape can be appropriately selected as the shape, and a known material such as concrete, FRP, or cast iron can be appropriately selected as the wall material. In one embodiment, the circulation purification device 5 includes a multi-layer filtration layer for passing the breeding aquarium water in a downward flow having a filtration rate of 20 m / hour or more, and the multi-layer filtration layer has an upper biological adhesion of 200 mm or more. The carrier layer and the lower sand layer having a filling thickness of 400 mm or more are provided so that the ratio of the thickness of the bioadhesive carrier layer to the thickness of the sand layer satisfies 0.2 to 0.7.

  The breeding tank 1 filled with seawater is appropriately fed with feed for breeding fish, and ammonia is generated by decomposition of urea discharged from the fish and residual feed. The breeding tank water flowing out from the breeding tank 1 flows into the aeration tank 3 through the breeding tank water discharge line 2. In addition, air is sent from the blower 10 through the air supply line 11 to the aeration tank 3 to perform aeration.

  Aerated water that has flowed out of the aeration tank 3 flows from the upper part of the circulation purification device 5 through the aerated water supply line 4. The circulation purification device 5 has a multilayer filtration layer 12 filled with a bioadhesive carrier in the upper part and sand in the lower part, and aerated water passes through the multilayer filtration layer 12 as a downward flow. The filtrate flowing out from the lower part of the circulation purification device 5 is returned to the breeding aquarium 1 through the return line 6 for circulation.

  If the operation of the circulation purification device 5 is continued, the water flow resistance will increase due to suspended matter (turbidity) trapped in the filter medium and microorganisms grown on the filter medium surface. Stop, open the valve 8, inject seawater or fresh water from the bottom of the circulation purification device 5 from the seawater or freshwater storage tank 7 according to the aquatic organism habitat environment, and perform backwashing. The backwash waste water can be discharged via the valve 8. Further, when the filter medium is not sufficiently washed by backwashing with water, the filter medium can be air-washed by supplying air from the blower 10 from the bottom of the circulation purification device 5. The cleaning exhaust gas can be discharged from the upper part of the circulation purification device 5.

  Examples for better understanding of the present invention and its advantages are shown below, but the present invention is not limited to the following examples.

<1. Preliminary test: Selection of bioadhesive carrier>
Prior to the experiment, when selecting the nitrifying bacteria adhesion carrier to be packed in the filtration tower, the biological adhesion carrier was packed into a column with a diameter of 20 mm at a thickness of 400 mm, and the raw water adjusted to a nitrogenous nitrogen concentration of 1-2 mg / L with tap water. A water passage test was performed at a water temperature of 18 to 25 ° C. for about 3 months. Granular activated carbon (particle size 1 mm and particle size 2 to 3 mm), anthracite (particle size 3 to 4 mm), zeolite (particle size 1 to 2 mm), granular ceramic (particle size 1 to 2 mm) are selected as the bioadhesive carrier Each was tested for biofouling performance (particle size range refers to minimum and maximum values). The adhesion performance was judged by the ammonia nitrogen concentration of the treated water. As a result, the bioadhesion performance was almost the same, but we decided to use granular activated carbon with organic matter adsorption ability for the purification test of the exhibition tank.

<2. Exhibition tank purification test>
The results of experiments using the circulation purification system for the exhibition aquarium water shown in the flow sheet of FIG. 1 will be described. The operating conditions of the exhibition tank water circulation purification system are as follows.
Exhibition tank water: seawater Exhibition tank volume: width 500mm x length 1800mm x depth 800mm
Types and number of aquatic organisms: red sea bream x 2, black sea bream x 2, medina x 3
Circulation purification device 5: Filtration tower (filtration area 0.02 m ² )
Multi-layer filtration layer 12: granular activated carbon layer at the top, sand layer at the bottom Back washing: back washing with water and back washing with air (as needed)

  Initially, emphasizing nitrification performance, the upper layer was filled with activated carbon with a thickness of 400 mm, and the lower layer with 200 mm of sand. The total packed thickness of the activated carbon layer and the sand layer (total thickness: packed thickness mm of the entire filter medium) was set to 600 mm because the height of the filtration tower was limited. As a result of passing the exhibition aquarium water as a downward flow at a filtration rate of 36 m / h, the clarity does not increase, so the thickness of the sand is increased without changing the total filling thickness while measuring the transparency, as shown in FIG. When the sand layer had a thickness of 400 mm or more, the transparency was 4 m or more. In addition, since 4 m was a measurement limit value because a self-made 4 m permeability meter was used for the transparency measurement, 4 m is described as “4 m or more” in FIG.

  Next, the amount of nitrification was measured. Because the aquarium water in the exhibition is for circulation purification, the total purification capacity of the circulation purification system is more important than the temporary treated water quality. As the conditions for the upper layer activated carbon height of 400 mm and the lower layer sand height of 200 m, the change in nitrification amount when the filtration rate (LV) was changed was examined.

As a result, as shown in FIG. 3, the amount of nitrification increases abruptly to a filtration rate (LV) of 20 m / hour or more, and then the rate of increase decreases, so a constant amount of nitrification can be secured at a filtration rate of 20 m / hour or more. It was judged to be a numerical value. The amount of nitrification is the amount of nitrification per unit volume per day and is calculated according to equation (1).

Amount of nitrification (g / L · day) = Filtration process inflow water amount (L / day) × (inflow NH ₃ -N-outflow NH ₃ -N) g / L ÷ filler volume (L) (1)
The filler capacity is the sum of both the activated carbon layer and the sand layer.

The nitrification amount shown in FIG. 3 is an average value of the nitrification amounts when tested for two days at the same filtration rate.

At this time, the concentration of ammonia nitrogen (NH ₃ -N) at the inlet and outlet of the filtration tower is such that, as shown in FIG. 4, the filtration rate is 20 m / hour or more, and the amount of nitrification increases. It can be seen that the ammoniacal nitrogen concentration in the water (display tank water) tends to decrease.

  As shown in FIG. 5, from the vicinity where the activated carbon layer thickness is less than 200 mm as a result of increasing the sand layer thickness and reducing the activated carbon layer thickness at a total filling thickness of 600 mm and a filtration rate of 20 m / hour, the aquarium water (= filtration process) There was a tendency for the ammonia nitrogen concentration in the inflow water to rise sharply. That is, it was confirmed that the activated carbon layer thickness is important to be 200 mm or more.

<3. Long-term experiment>
(3-1: Examination of activated carbon layer / sand layer thickness ratio)
Based on the above results, using the circulation purification system for the exhibition aquarium water shown in the flow sheet of FIG. 1, the following experiments 1 to 4 were performed at the filtration speed of 20 m / hour as the operating conditions described above. A purification test was conducted for a long period of time (3 months) under the above filling conditions.
Experiment 1: Activated carbon filling thickness 200 mm, sand filling thickness 400 mm (activated carbon layer / sand layer thickness ratio 0.5)
Experiment 2: Activated carbon filling thickness 200 mm, sand filling thickness 1000 mm (activated carbon layer / sand layer thickness ratio 0.2)
Experiment 3: Activated carbon filling thickness 350 mm, sand filling thickness 500 mm (activated carbon layer / sand layer thickness ratio 0.7)
Experiment 4: Activated carbon filling thickness 100 mm, sand filling thickness 400 mm (activated carbon layer / sand layer thickness ratio 0.25)
As a result, in all of Experiment 1, Experiment 2, and Experiment 3, it was possible to secure a clear breeding water with a low ammonia nitrogen concentration. However, in Experiment 2, since the loss head was large and the frequency of backwashing was high, it was confirmed that the total filling thickness was preferably 1000 mm or less in order to shorten the time loss due to backwashing. In Experiment 4, a large amount of ammonia nitrogen remained as compared with Experiments 1, 2, and 3.

  As filtration continues, trapped substances and adhering microorganisms are filtered by backwashing as appropriate because trapping of suspended solids (turbidity) and microorganisms grown on the surface of the filter medium reduce the porosity and increase the head loss. It must be washed out of the tower. Since adhering microorganisms are separated and washed after the end of the backwashing operation, the nitrification ability is temporarily lowered, and the ammoniacal nitrogen concentration in the filtration tower effluent increases.

(3-2: Examination of the effects of backwashing)
In order to grasp the relationship between the effect of backwashing and the nitrification ability of activated carbon, the exhibition aquarium water (SS concentration: 2 to 3 mg / L) is filtered using the exhibition aquarium water circulation purification system shown in the flow sheet of FIG. A purification test was conducted for a long period (3 months) under the filling conditions of the following experiments 1 and 4 at a speed of 36 m / hour. During the test, backwashing (air washing 2 minutes, water washing 3 minutes) was performed when the loss head of the entire filtration layer reached 1400 to 1700 mm.
Experiment 1: Activated carbon filling thickness 200 mm, sand filling thickness 400 mm (activated carbon / sand filling thickness ratio 0.5)
Experiment 4: Activated carbon filling thickness 100 mm, sand filling thickness 500 mm (activated carbon / sand filling thickness ratio 0.2)
As a result, in both Experiment 1 and Experiment 4, the filtered water effluent ammonia nitrogen concentration increased, but the average number of days required for the ammonia nitrogen concentration to recover to the concentration immediately before backwashing was: Experiment 1 was 4 days and Experiment 4 was 11 days. From this, it was confirmed that the activated carbon thickness was 200 mm or more from the viewpoint of maintaining the nitrification ability after backwashing.

1 Breeding tank 2 Breeding tank water discharge line 3 Aeration tank 4 Aerated water supply line 5 Circulation purification device (filtration tower)
6 Return line 7 Storage tank 8 Valve 10 Blower 11 Air supply line 12 Multi-layer filtration layer

Claims (8)

  It is a method of circulating and purifying breeding water through a filtration process, wherein the filtration process comprises a bioadhesive carrier layer filled with a bioadhesive carrier other than sand at a filling thickness of 200 mm or more and a sand layer filled with sand at a lower thickness of 400 mm or more. In addition, the breeding water is passed through the multi-layer filtration layer in which the sum of the filling thickness of the bioadhesive carrier layer and the sand layer is 600 mm to 1200 mm at a filtration rate of 20 m / hour or more. A method involving that.   The method of claim 1, wherein the ratio of the bioadhesive carrier layer fill thickness to the sand layer fill thickness is 0.2-0.7.   The method according to claim 1 or 2, wherein the bioadhesive carrier is activated carbon and / or anthracite.   An apparatus for circulating and purifying breeding water, comprising a multi-layer filtration layer for passing the breeding water in a downward flow with a filtration speed of 20 m / h or more. An apparatus having a bioadhesive carrier layer other than sand and a lower sand layer having a filling thickness of 400 mm or more, and a total of the filling thickness of the bioadhesive carrier layer and the filling thickness of the sand layer is 600 mm to 1200 mm.   The device according to claim 4, wherein the ratio of the filling thickness of the bioadhesive carrier layer to the filling thickness of the sand layer satisfies 0.2 to 0.7.   The apparatus according to claim 4 or 5, wherein the biofouling carrier is activated carbon and / or anthracite.   An aquarium and the device according to any one of claims 4 to 6 are provided, and breeding water discharged from the aquarium flows into the multilayer filtration layer of the device, and the filtered water discharged from the device enters the aquarium. Circulation purification system for breeding water where both are connected so that they can be sent back.   The system for circulating and purifying breeding water according to claim 7, wherein the breeding water discharged from the tank is configured to flow into the multilayer filtration layer of the device through the aeration tank.

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