JP2024098614A - Method for controlling the amount of seawater intake supplied to a feed production device - Google Patents

Abstract

To provide a control method for an intake amount of sea water for controlling an intake amount of sea water in a sewage discharge zone where sewage discharge water is discharged, and supplying sea water with a constant vegetable biomass quantity to a feed production device.SOLUTION: In a method for feeding marine organisms in which sea water is taken in from a sewage discharge zone where sewage discharge water treated at a water treatment facility is discharged and is subjected to filtration treatment, treatment liquid after the filtration treatment is supplied to a seaweed culture zone, and suspension substances separated at the time of filter material backwashing are supplied to a shellfish culture zone together with washing waste liquid, a reference value Pn0 of a biomass quantity is set beforehand with a latitude given and the quantity of the biomass contained in the sea water taken in from the sewage discharge zone is measured at the time of filtration treatment process; the speed of a sea water pump 13 is slowed down gradually when a measurement value Pn is higher than the reference value Pn0; the speed of the sea water pump 13 is increased gradually when the measurement value Pn is lower than the reference value Pn0; feed can be supplied to shellfish and seaweeds stably by controlling the quantity of biomass within a range of the reference value Pn0.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for controlling the amount of seawater intake supplied to a food production device for marine organisms such as shellfish and seaweed.

In the past, oligotrophy has occurred in marine areas where shellfish, seaweed, and other marine organisms live due to a lack of nutrients such as nitrogen and phosphorus. This oligotrophy causes a decrease in phytoplankton, which leads to problems such as the insufficient growth of oysters, which feed on phytoplankton, and the discoloration of seaweed, which grows by absorbing nutrients, causing problems for the aquaculture industry.

Patent Document 1 discloses a technology for simultaneously cultivating seaweed and shellfish, and describes controlling the amount of seawater supplied from the seaweed culture tank to the shellfish culture tank depending on the amount of saturated dissolved oxygen in each tank.

Patent Document 2 discloses a technology that controls the amount of plankton production by adjusting the amount of nutrients input based on the concentration of nutrients in seawater, thereby promoting the proliferation of marine fishery products that feed on plankton.

JP 2022-114928 A JP 2001-211777 A

Conventionally, seaweed grows by absorbing nutrients, so it can be said that in terms of growth it has a close relationship with oysters, which feed on phytoplankton that feeds on nutrients. Therefore, we were investigating whether there was a way to efficiently cultivate seaweed by producing the nutrients and phytoplankton that are the food for each marine organism in a single feed production device and feeding them simultaneously.

Patent Document 1 describes a technology for controlling the amount of seawater supplied to a shellfish culture tank based on the amount of saturated dissolved oxygen in the seaweed culture tank and the shellfish culture tank, but it uses the measured amount of dissolved oxygen as an index for control, and is not a technology for controlling the amount of seawater supplied based on the amount of phytoplankton calculated using the amount of dissolved oxygen. In addition, there is no mention of a purpose for control such as obtaining a stable supply of food for the seaweed and shellfish, and it is merely a matter of controlling the amount of dissolved oxygen in the farm. Furthermore, when feeding food to the seaweed and shellfish, a feed feeding device needs to be installed in each tank.

Patent Document 2 describes a technology that adjusts the amount of nutrients supplied to the ocean based on the measured nutrient concentration, but the nutrients used to adjust the concentration in the ocean are dissolved in fresh water, and are not sewage effluent containing nutrients discharged from water treatment facilities. Therefore, nutrients must be prepared separately.

The present invention has been made in consideration of the above problems, and provides a method for controlling the amount of seawater intake supplied to a feed production device, which is characterized by continuously measuring the dissolved oxygen concentration in the sewage discharge area into which the sewage effluent is discharged during the filtration process, and controlling the amount of seawater intake using the net production amount of plant biomass calculated based on the measured value, thereby making it possible to constantly supply a constant amount of plant biomass to the feed production device, and to provide a stable supply of feed to shellfish and seaweed.

In a method for feeding marine organisms, seawater is taken from a sewage discharge area into which sewage effluent treated at a water treatment facility is discharged, filtered, the filtered liquid is fed to a seaweed cultivation area, and suspended matter detached during backwashing of the filter media is fed to a shellfish cultivation area together with the washing effluent. A reference value Pn0 for the amount of biomass with a predetermined range is set, and the amount of biomass contained in the seawater taken from the sewage discharge area during the filtration process is measured, and if the measured value Pn is higher than the reference value Pn0, the speed of the seawater pump is gradually decreased, and if the measured value Pn is lower than the reference value Pn0, the speed of the seawater pump is gradually increased, thereby controlling the amount of biomass to be within the range of the reference value Pn0, and seawater with a constant amount of biomass can be taken from the sewage discharge area.

The amount of biomass is the net production amount of plant biomass calculated from the following (Equation 1) using the dissolved oxygen concentration in the sewage discharge area measured during the filtration treatment process, so that seawater with a constant amount of plant biomass can be supplied to the feed production device during the filtration treatment process.
Pn=(12L+12D)-0TIME...(Formula 1)
Pn: Net production of plant biomass 12L+12D: Dissolved oxygen concentration measured under 12 hours of light + dissolved oxygen concentration measured under 12 hours of dark 0TIME: Initial dissolved oxygen concentration measured

The amount of biomass is the amount of plant biomass calculated from at least one of the measurement data of the chlorophyll fluorescence intensity measured during the filtration process or the captured image, so that seawater with a constant amount of plant biomass can be supplied to the feed production device during the filtration process.

By installing a storage tank to temporarily store seawater taken from the sewage discharge area and supplying the seawater from the storage tank to the filtration device, it is possible to continuously supply feed even in the event of a natural disaster such as a tsunami.

According to the present invention, the amount of plant biomass contained in seawater taken from the sewage discharge area is measured, and the amount of water taken is adjusted according to the measured value, so that seawater containing a constant amount of plant biomass can be supplied to the feed production device at all times. Specifically, the dissolved oxygen concentration in the sewage discharge area is measured in real time, and the net production amount of plant biomass calculated based on the concentration is used for control, so that the feeding efficiency does not decrease even if the water quality in the sewage discharge area changes due to seasonal fluctuations, etc. In addition, since there is no excessive supply of plant biomass to the shellfish culture area, it is possible to take measures against red tides in the surrounding sea areas. Furthermore, since sewage discharge water treated at a water treatment facility is discharged into the sewage discharge area, there is no need to prepare nutrients or plant biomass separately. Since the feeding of shellfish and seaweed is performed by a single device, the efficiency of aquaculture can be improved.

1 is a schematic diagram of a feed production device according to the present invention; FIG. This is also a downflow filtration device.

FIG. 1 is a schematic diagram of a feed production apparatus according to the present invention, and FIG. 2 is a downflow type filtration apparatus according to the present invention.
As shown in Fig. 1, the feed production device 1 according to this embodiment includes a transport unit 3 that takes in treated liquid (seawater) from a sewage discharge area into which sewage discharge water treated in a water treatment facility is discharged and supplies it to a filtration device 2, the filtration device 2 that separates seawater into suspended matter and a treated liquid, a feeding unit 4A that feeds the treated liquid to seaweed in a seaweed cultivation area, and a feeding unit 4B that feeds suspended matter detached by a cleaning fluid supplied from a cleaning fluid supply pipe 5 connected to the filtration device 2 together with the cleaning effluent to shellfish in the shellfish cultivation area. Each component will be described in detail below.

The transport section 3 is composed of a seawater pump 13 installed in the sewage discharge area and a seawater supply pipe 6 connected at one end to the seawater pump 13 and at the other end to the filtration device 2, and is configured to pump up seawater in the sewage discharge area and supply it to the filtration device 2. In this embodiment, the seawater taken in by the seawater pump 13 is directly supplied to the filtration device 2, but a separate storage tank (not shown) may be installed to temporarily store the pumped up seawater. In this case, the seawater after the sewage discharge water is discharged may be stored, or the seawater before the sewage discharge water is discharged may be supplied to the storage tank and stored separately from the sewage discharge water.

Sewage effluent discharged into a sewage discharge area is a treated liquid that has been biologically treated after primary treatment of wastewater containing nutrients (nitrogen, phosphorus, etc.) such as human waste, sewage, and wastewater from food production and processing to remove solids. Specifically, the liquid to be treated flowing into a sewage treatment plant is separated by settling in a first settling tank, the separated supernatant is biologically treated in a reaction tank supplied with oxygen, and then further separated by settling in a final settling tank to obtain the supernatant. The supernatant may be disinfected before use.

The supernatant liquid discharged from water treatment facilities is generally discharged into the ocean, but the above-mentioned treatment methods cannot completely remove the nutrients contained in the treated liquid. For this reason, it can be said that the sewage discharge area into which sewage effluent is discharged has a relatively high concentration of nutrients compared to other ocean areas. In addition, sewage discharge areas with high nutrient concentrations also have a large amount of plant biomass because phytoplankton (hereinafter referred to as plant biomass), which feeds on nutrients, proliferate there.

In this embodiment, seawater is pumped from a sewage discharge area where the nutrient concentration and plant biomass amount are high, and the pumped seawater is supplied to the filtration device 2. Note that the sewage discharge area in this embodiment is a closed water area with little water flowing in and out from the outside, and is a sea area where nutrients tend to accumulate.

As shown in FIG. 2, the filtration device 2 is a downward flow filtration device in which a seawater supply pipe 6 is connected to a filtration tank 7, and seawater is supplied from above the filtration tank 7 and discharged from below. Inside the filtration tank 7, a filter media outflow prevention screen 8 is disposed at a predetermined height from the bottom of the tank, and a filter media layer 9 having a predetermined thickness is formed on the upper side of the screen.

The filter layer 9 is formed by filling it with irregular granular fiber filter media, and captures suspended matter contained in seawater supplied from above the filter layer 9. The suspended matter in the seawater contains plant biomass, so by filtering the seawater, plant biomass can be obtained in the filter tank 7. The suspended matter in the seawater also contains organic matter derived from the remains and feces of living organisms, but in this embodiment, the purpose is to obtain plant biomass that can be used as food for marine organisms (bivalves).

The filter medium is not limited to fiber filter medium, and other filter mediums such as resin filter medium, sand, etc. may be used. The diameter, shape, etc. are also selected appropriately depending on the application. Depending on the conditions, the filter device 2 may be placed on a raft or the like to make it a floating type.

A cleaning fluid supply pipe 5 is connected below the filtration tank 7, so that cleaning fluid can be supplied from below the filtration tank 7 when cleaning the filter media. In this embodiment, a cleaning liquid supply pipe is used as the cleaning fluid supply pipe 5, and seawater (cleaning liquid) is supplied from below the filtration tank 7 to clean the filter media, but if necessary, compressed air, agitating blades, etc. may also be used in combination to agitate and clean the filter media. Also, the cleaning fluid is not limited to seawater.

The filtration device 2 further includes a foam separator 10 disposed above the filtration tank 7. The foam separator 10 is disposed below the seawater supply pipe 6 connected to the filtration tank 7, and is configured to perform foam separation on the seawater supplied from the seawater supply pipe 6.

The foam separation device 10 is composed of an air diffuser tube with one end connected to an air supply source such as a blower or compressor (not shown), and by driving the air supply source, fine air bubbles are sprayed into the seawater from numerous nozzle holes 12 formed at the top of the air diffuser tube. By supplying fine air bubbles to the seawater, suspended matter in the seawater is separated by floating, forming stable foam on the water surface.

The stable foam is supplied to the shellfish cultivation area from the feeding section 4B, which will be described in detail later. Since this stable foam contains plant biomass, the recovery rate of the plant biomass can be increased by performing foam separation. Note that the foam separation device 10 is not limited to the aeration tube type, and can be any device that generates fine bubbles.

The feeding section 4A is a pipe connected at one end to the bottom of the filtration tank 7 and at the other end to the seaweed cultivation area, and is configured to supply seawater (treated liquid) discharged after filtration to the seaweed cultivation area. The treated liquid supplied to the seaweed cultivation area has a high concentration of nutrients because it is seawater pumped up from a sewage discharge area and filtered, where the concentration of nutrients is relatively high.

Since seaweed grown in seaweed farming areas grows by absorbing nutrients, supplying a treatment solution with a high concentration of nutrients promotes the growth of the seaweed. This allows the production of high-quality seaweed that does not fade.

If necessary, a return pipe 16 may be connected to the feeding section 4A as shown in FIG. 1. By connecting the other end of the return pipe 16 to the seawater supply pipe 6, the treatment liquid can be supplied to the liquid to be treated (seawater) supplied from the seawater supply pipe 6, making it possible to adjust the concentration of the liquid to be treated. This makes it possible to reduce the solids load on the filtration device 2 even if the seawater taken contains suspended matter other than plant biomass.

On the other hand, the feeding section 4B is a pipe with one end connected to the top of the filtration tank 7 and the other end connected to the shellfish cultivation area, and is configured so that the plant biomass contained in the stable foam and the plant biomass detached during cleaning of the filter layer 9 can be supplied to the shellfish cultivation area together with the cleaning effluent. The cleaning effluent supplied to the shellfish cultivation area contains a large amount of plant biomass because it is seawater pumped up from a sewage discharge area and filtered, where the amount of plant biomass is relatively large.

Oysters cultivated in shellfish farming areas grow by capturing plant biomass, so supplying them with washing effluent, which contains a high amount of plant biomass, promotes oyster growth.

In this embodiment, when performing filtration using the above-mentioned filtration device 2, the net production amount of plant biomass contained in the seawater taken by the seawater pump 13 shown in FIG. 1 is determined, and the amount of water taken is determined based on the net production amount. The value of the dissolved oxygen concentration measured by the measurement unit 14 consisting of a dissolved oxygen meter installed in the sewage discharge area is sent to the control unit 15, and the control unit 15 sends a command to the seawater pump 13. Note that the measurement unit 14 may be installed in the seawater supply pipe 6 as it is only necessary to measure the dissolved oxygen concentration of the liquid to be treated supplied to the filtration device 2. The timing of measuring the dissolved oxygen concentration may be simultaneous with the start of the filtration process or prior to the filtration process.

The feed production method in this embodiment will be described in detail below with reference to Figures 1 and 2.

<Discharge process>
In the discharge process, the sewage effluent (supernatant) obtained after gravity settling in the final settling tank of the water treatment facility is discharged into any sea area (sewage discharge area).

<Transportation process>
In the transport process, seawater is pumped up from the sewage discharge area by driving a seawater pump 13 installed in the sewage discharge area, and the seawater is supplied to the filtration device 2 via the seawater supply pipe 6. At this time, the valve V1 installed in the seawater supply pipe 6 and the valve V2 installed in the feeding section 4A are open.

<Filtration process>
In the filtration process, the pumped seawater is supplied to the filtration device 2 for filtration. Seawater is supplied from the seawater supply pipe 6 into the filtration tank 7, and fine air bubbles are supplied from the nozzles 12 of the foam separator 10 toward the upper part of the filtration tank 7, while suspended matter is captured by the filter layer 9 filled in the filtration tank 7. At this time, the valve V3 installed in the feeding section 4B is open.

The many fine bubbles that are ejected adsorb suspended matter mixed in the seawater supplied from above, and suspended matter that has naturally detached from the filter layer 9 due to the effects of water pressure, etc., and rise to the water surface. Then, the bubbles that adsorb the suspended matter that rise one after another gather at the water surface, forming a stable foam on the water surface.

The stable foam formed on the water surface is supplied to the shellfish cultivation area from the feeding section 4B connected above the filtration tank 7. Since the stable foam contains plant biomass that serves as food for the shellfish, it can be said that by performing foam separation during the filtration process, the food can be efficiently fed to the shellfish.

Foam separation is performed continuously during the filtration process, but the timing for starting the supply of compressed air is determined appropriately. The method of supplying stable foam from the feeding section 4B to the shellfish cultivation area can be selected as appropriate, for example by discharging the water by overflowing while keeping the water level in the filtration tank 7 constant during the filtration process. Depending on the conditions, the foam separation device 10 may be omitted and only the normal filtration process may be performed.

During the filtration process, plant biomass contained in the seawater passing through the filter layer 9 gradually accumulates on the filter layer 9. Meanwhile, the seawater that has passed through the filter layer 9 is supplied as a treatment liquid from the feeding section 4A to the seaweed cultivation area. The treatment liquid supplied to the seaweed cultivation area from the feeding section 4A contains fine air bubbles sprayed from the foam separation device 10, and supplying this treatment liquid to the seaweed cultivation area promotes the growth of seaweed.

Filtration may also be performed using an upflow filtration device. In this case, the liquid to be treated (seawater) is supplied from the bottom of the filtration tank 7, the treated liquid discharged from the top of the filtration tank 7 is supplied to the seaweed cultivation area, and the plant biomass detached from the filter material by the cleaning liquid (seawater) supplied from above is supplied to the shellfish cultivation area from the bottom of the filtration tank 7.

In this embodiment, the dissolved oxygen concentration in the sewage discharge area is measured in real time during the filtration process, and the measured value is used to calculate the net production amount Pn of plant biomass. Then, based on the calculated net production amount Pn, the seawater pump 13 is controlled to adjust the amount of seawater intake. The method for calculating the net production amount Pn of plant biomass and the method for controlling the amount of seawater intake are described in detail below.

First, the net production amount Pn of plant biomass is calculated by the following formula (1).

Pn=(12L+12D)-0TIME...(Formula 1)

Pn: Net production of plant biomass 12L+12D: Dissolved oxygen concentration measured under 12 hours of light + dissolved oxygen concentration measured under 12 hours of dark 0TIME: Initial dissolved oxygen concentration measured

12L+12D is the sum of the dissolved oxygen concentration measured in the sewage discharge area under 12 hours of light conditions during the filtration process and the dissolved oxygen concentration measured in the sewage discharge area under 12 hours of dark conditions. 0TIME indicates the initial dissolved oxygen concentration measured in the sewage discharge area before starting to measure the dissolved oxygen concentration in the sewage discharge area under 12L+12D conditions. By subtracting the initial dissolved oxygen concentration (0TIME) from the calculated 12L+12D value, the net daily production Pn of plant biomass living in the sewage discharge area can be calculated.

Next, a method for controlling the amount of seawater intake will be described in detail. A reference value Pn0 for the net production amount of plant biomass with a predetermined range is set in advance. The net production amount Pn calculated by the above-mentioned method is then compared with the preset reference value Pn0, and if the calculated value Pn is higher than the reference value Pn0, the rotation speed of the seawater pump 13 is gradually decreased to reduce the amount of water intake. On the other hand, if the calculated value Pn is lower than the reference value Pn0, the rotation speed of the seawater pump 13 is gradually increased to increase the amount of water intake. The above control is repeated until the calculated value Pn falls within the range of the reference value Pn0.

If the calculated value Pn is within the range of the reference value Pn0, the seawater pump 13 continues to operate while maintaining its rotation speed. Note that the control uses PID control to gradually increase or decrease a predetermined adjustment amount α so that the calculated value Pn falls within the range of the reference value Pn0.

In this way, by adjusting the amount of seawater intake based on the net production amount Pn of plant biomass contained in the seawater in the sewage discharge area, a constant amount of plant biomass can be constantly supplied to the feed production device 1. By continuously supplying seawater containing a constant amount of plant biomass to the filtration device 2 that constitutes the feed production device 1 and filtering it, a constant amount of plant biomass can be constantly obtained. The obtained plant biomass is deposited on the filter layer 9, peeled off by backwashing, which will be described later, and supplied to the shellfish cultivation area, allowing a stable supply of feed to the shellfish.

In addition, by constantly cleaning and recovering a constant amount of solid matter (plant biomass) in the filtration device 2 during the cleaning process described below, the filtration efficiency does not decrease, and the filtration process can be continued for a long period of time. This allows a constant amount of treatment liquid to be continuously supplied to the seaweed cultivation tank, allowing a stable supply of food to the seaweed.

In this embodiment, the amount of plant biomass contained in the sewage discharge area was calculated using the above formula, but to grasp the amount of plant biomass, control may be performed by comparing the measured value of chlorophyll fluorescence intensity with a predetermined reference value using a known chlorophyll fluorescence sensor, or control may be performed based on image data captured using a known image detection device. The chlorophyll fluorescence sensor and the image detection device may be used together. The chlorophyll fluorescence intensity and captured image are measured at any point between the sewage discharge area and the filtration device 2.

In addition, to maintain a constant net production volume Pn, the amount of seawater taken from the sewage discharge area was controlled, but the amount of sewage effluent discharged from the water treatment facility may also be controlled. Since sewage effluent contains nutrients such as nitrogen and phosphorus that serve as food for plant biomass, the net production volume of plant biomass can be adjusted by controlling the amount of sewage effluent.

Furthermore, in this embodiment, real-time control is performed using the dissolved oxygen concentration continuously measured during the filtration process, but a control method may also be used in which two consecutive measured values are obtained at a predetermined interval, the two measured values are used to calculate the net production volume Pn, and the calculated net production volume Pn is used to calculate the total production volume Pg and the respiration volume R, and whether the net production volume Pn is on an increasing or decreasing trend is predicted. The increase/decrease prediction control method is described in detail below.

First, to obtain two consecutive dissolved oxygen concentration measurements, the dissolved oxygen concentration is measured at a given measurement time Tn and immediately thereafter at Tn+1. Then, using each measurement value, the net production volumes Pn and Pn+1 are calculated using the above formula (1).

Next, the total production Pgn and the total production Pgn+1 are calculated from the following (Equation 2). Here, in order to calculate each total production Pg, the respiration rates Rn and Rn+1 are calculated from the following (Equation 3). Note that (Equation 2) is a formula derived from the following (Equation 4) for calculating the net production.

Pg=Pn+R...(Formula 2)
R=0TIME-24D...(Formula 3)
Pn=Pg-R...(Formula 4)

Pg: Total production of plant biomass Pn: Net production of plant biomass calculated from (Equation 1) R: Respiration rate of plant biomass 0TIME: Initial dissolved oxygen concentration measurement value 24D: Dissolved oxygen concentration measurement value under dark conditions for 24 hours

The respiration rates Rn and Rn+1 are calculated by subtracting the measured dissolved oxygen concentration under 24-hour dark conditions from the initial dissolved oxygen concentration measured in the sewage discharge area. The respiration rate of the plant biomass can be determined by subtracting the measured dissolved oxygen concentration from the initial dissolved oxygen concentration. After calculating the respiration rates Rn and Rn+1, these values and the net production rates Pn and Pn+1 calculated above (Equation 1) are used to calculate the total production rates Pg and Pg+1. Each total production rate Pg is calculated by adding the respiration rate R to the calculated net production rate Pn.

The total production volumes Pgn, Pgn+1 and respiration volumes Rn, Rn+1 at each measurement time are calculated from the above (Equations 1-3), and the calculated total production volumes Pgn and Pgn+1 are compared. Furthermore, the ratio of respiration volume Rn to total production volume Pgn at time Tn is compared with the ratio of respiration volume Rn to total production volume Pgn at time Tn+1.

As shown in the following (Formula 5), for example, if the total production Pgn+1 is greater than the total production Pgn, it is understood that at time Tn+1, photosynthesis of the plant biomass is actively taking place in the sewage discharge area, and the plant biomass is growing in large quantities through photosynthesis. Also, as shown in the following (Formula 6), if the ratio of the respiration rate Rn+1 to the total production Pgn+1 is greater than the ratio of the respiration rate Rn to the total production Pgn, it is understood that at time Tn+1, the plant biomass is actively photosynthesizing, but the respiration rate is high, so that a large amount of the energy obtained by photosynthesis is being consumed.

Pgn<Pgn+1...(Formula 5)
Rn/Pgn<Rn+1/Pgn+1...(Formula 6)

From the above (Equations 5 and 6), when the total production Pg and the respiration rate R as a percentage of the total production Pg are large, the energy consumption of the plant biomass is large, so the net production Pn of the plant biomass calculated by subtracting the respiration rate from the total production is predicted to tend to decrease. On the other hand, at a time Tn when the total production Pg and the respiration rate R as a percentage of the total production Pg are smaller than time Tn+1, the amount of plant biomass is small and the energy consumption is also small, so the net production Pn of the plant biomass is predicted to tend to increase.

In this way, by predicting whether the net production volumes Pn, Pn+1 at specific times Tn and Tn+1 are increasing or decreasing, the state of the net production volume of plant biomass in the sewage discharge area can be grasped. If the prediction results show an increasing trend, the speed of the seawater pump 13 is gradually decreased to reduce the amount of water taken in, and if the prediction shows a decreasing trend, the speed of the seawater pump 13 is gradually increased to increase the amount of water taken in, thereby supplying a constant amount of plant biomass to the filtration device 2.

<Filter media cleaning process>
In the filter media washing step, the filter media layer 9 filled in the filtration tank 7 is washed. A washing liquid is supplied from the downstream side of the filter media layer 9 to pass the water through the filter media layer 9, and then discharged from the upstream side. This backwashing peels off the plant biomass captured by the filter media layer 9. The peeled plant biomass is supplied to the shellfish cultivation area via the feeding section 4B together with the washing wastewater (seawater that has passed through the filter media layer 9) discharged from the upstream of the filter media layer 9.

The filter media cleaning process is performed, for example, when the filtration pressure increases due to clogging caused by suspended matter captured in the filter media layer 9 during the filtration process, when the cumulative operating time reaches a specified time or time, or when the treatment liquid no longer meets a specified standard. When cleaning the filter media, valves V1 and V2 are closed, and valve V4 installed in the cleaning liquid supply pipe 17 is opened.

Since the cleaning is performed using seawater, if a compressed air supply line is added below the cleaning fluid supply pipe 5, foam separation of the seawater supplied from the cleaning fluid supply pipe 5 is performed simultaneously with the stirring and cleaning. The stirring and cleaning peels the plant biomass off the filter medium, while a stable foam containing the plant biomass can be supplied from the feeding section 4B to the shellfish cultivation area, allowing for efficient production of feed.

In this embodiment, seaweed and oysters are listed, but the invention can be applied to other marine organisms that feed on nutrients and plant biomass.

The present invention is not limited to the embodiment described above. Modifications can be made as appropriate without departing from the spirit of the present invention.

The present invention is capable of constantly supplying seawater containing a constant concentration of plant biomass to a feed production device, and is therefore a useful technology for cultivating multiple marine organisms, as it can steadily obtain feed for multiple marine organisms. In addition, the technology can be implemented simply by installing the feed production device in a designated sea area, and therefore can be used in any sea area.

2 Filtration device 13 Seawater pump Pn0 Reference value of net production of plant biomass Pn Measured value of net production of plant biomass

Claims (4)

A method for feeding marine organisms, comprising the steps of: taking seawater from a sewage discharge area into which sewage discharge water treated at a water treatment facility is discharged, filtering the filtered liquid, feeding the treated liquid to a seaweed culture area, and feeding suspended matter detached during backwashing of a filter medium together with the washing effluent to a shellfish culture area,
A reference value (Pn0) of the amount of biomass having a certain range is set in advance,
The amount of biomass contained in seawater taken from the sewage discharge area during the filtration process is measured,
If the measured value (Pn) is higher than the reference value (Pn0), the rotational speed of the seawater pump (13) is gradually reduced,
If the measured value (Pn) is lower than the reference value (Pn0), the rotation speed of the seawater pump (13) is increased stepwise.
A method for controlling the amount of seawater intake supplied to a feed production apparatus, comprising controlling the amount of biomass within a range of a reference value (Pn0). A method for controlling the amount of seawater intake supplied to a feed production device as described in claim 1, characterized in that the amount of biomass is the net production amount of plant biomass calculated from the following (Equation 1) using the dissolved oxygen concentration in the sewage discharge area measured during the filtration treatment process.
Pn=(12L+12D)-0TIME...(Formula 1)
Pn: Net production of plant biomass 12L+12D: Dissolved oxygen concentration measured under 12 hours of light + dissolved oxygen concentration measured under 12 hours of dark 0TIME: Initial dissolved oxygen concentration measured A method for controlling the amount of seawater intake supplied to a feed production device as described in claim 1, characterized in that the biomass amount is a plant biomass amount calculated from at least one of measurement data of chlorophyll fluorescence intensity measured during a filtration treatment process or an image captured. A method for controlling the amount of seawater taken in and supplied to a feed production apparatus described in any one of claims 1 to 3, characterized in that a storage tank is provided for temporarily storing the seawater taken in from the sewage discharge area, and the seawater is supplied from the storage tank to a filtration apparatus (2).

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