Method for controlling the amount of seawater intake supplied to a feed production device

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

[Technical Field]

[0001] The present invention relates to a method for controlling the amount of seawater intake supplied to a food producing device for marine organisms such as shellfish and seaweed. [Background technology]

[0002] 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 has led to a decrease in phytoplankton, causing problems such as the insufficient growth of oysters, which feed on phytoplankton, and discoloration of seaweed, which grows by absorbing nutrients, causing problems for aquaculture.

[0003] 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 according to the saturated dissolved oxygen levels in each tank.

[0004] Patent Document 2 discloses a technology for controlling the amount of plankton production by adjusting the amount of nutrient salts input based on the concentration of nutrient salts in seawater, thereby promoting the proliferation of marine fishery products that feed on plankton. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-114928 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-211777 Summary of the Invention [Problem to be solved by the invention]

[0006] Traditionally, seaweed grows by absorbing nutrients, so it can be said that it has a close relationship with oysters, which feed on phytoplankton that feeds on nutrients. Therefore, we investigated whether there was a way to efficiently cultivate seaweed by generating nutrients and phytoplankton, which are the food of each marine organism, in a single feed generation device and feeding them simultaneously.

[0007] Patent Document 1 describes a technology for controlling the amount of seawater supplied to a seaweed culture tank and a shellfish culture tank based on the saturated dissolved oxygen level in the tank. However, the technology uses the measured dissolved oxygen level as a control indicator, and does not control the amount of seawater supplied based on the amount of phytoplankton calculated using the dissolved oxygen level. Furthermore, there is no mention of a purpose for control, such as obtaining a stable supply of feed for the seaweed and shellfish; it merely controls the amount of dissolved oxygen in the aquaculture facility. Furthermore, when feeding seaweed and shellfish, a feed supplying device must be installed in each tank.

[0008] Patent Document 2 describes a technology for adjusting the amount of nutrients supplied to the ocean based on measured nutrient concentrations, but the nutrients used to adjust the ocean concentrations are dissolved in freshwater, not sewage effluent containing nutrients discharged from water treatment facilities. Therefore, nutrients must be prepared separately.

[0009] The present invention has been made in consideration of the above-mentioned 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 a sewage discharge area into which sewage effluent is discharged during the filtration treatment 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 provide a stable supply of feed to shellfish and seaweed. [Means for solving the problem]

[0010] In this method of feeding marine organisms, seawater is taken from a sewage discharge area into which sewage effluent treated at a water treatment facility is discharged, and filtered. The filtered liquid is then fed to a seaweed cultivation area, and suspended matter that has been removed during backwashing of the filter media is fed to a shellfish cultivation area together with the washed wastewater. A predetermined range of reference value Pn0 for the amount of biomass is set, and the amount of biomass contained in the 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 speed of the seawater pump is gradually reduced, 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.

[0011] The amount of biomass is the net production amount of plant biomass calculated using the dissolved oxygen concentration in the sewage discharge area measured during the filtration process using the following formula (1), so that seawater with a constant amount of plant biomass can be supplied to the feed production device during the filtration process. Pn=(12L+12D)-0TIME...(Formula 1) Pn: Net production of plant biomass 12L+12D: Dissolved oxygen concentration measured under 12 hours of light + 12 hours of dark 0TIME: Initial dissolved oxygen concentration measurement value

[0012] The biomass amount is the plant biomass amount 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 plant biomass amount can be supplied to the feed production device during the filtration process.

[0013] 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. [Effects of the Invention]

[0014] According to the present invention, by measuring the amount of plant biomass contained in seawater taken from a sewage discharge area and adjusting the amount of water taken according to the measured value, seawater containing a constant amount of plant biomass can be constantly supplied to the feed production device. Specifically, the dissolved oxygen concentration in the sewage discharge area is measured in real time, and the net production of plant biomass calculated based on the measured value is used for control. Therefore, feeding efficiency does not decrease even when the water quality in the sewage discharge area changes due to seasonal fluctuations, etc. Furthermore, excessive plant biomass is not supplied to the shellfish culture area, making it possible to prevent red tides in the surrounding sea area. Furthermore, since sewage effluent treated at a water treatment facility is discharged into the sewage discharge area, there is no need to separately prepare nutrients or plant biomass. Since feed for shellfish and seaweed is provided using a single device, aquaculture efficiency can be improved. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a feed production device according to the present invention. FIG. [Figure 2] It is also a downward flow filtration device. DETAILED DESCRIPTION OF THE INVENTION

[0016] FIG. 1 is a schematic diagram of a feed production apparatus according to the present invention, and FIG. 2 is a downward flow filtration apparatus according to the present invention. As shown in Figure 1, the feed production device 1 of this embodiment includes a transport unit 3 that takes in treated liquid (seawater) from a sewage discharge area into which sewage effluent treated at 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 a shellfish cultivation area. Each component is described in detail below.

[0017] The transport unit 3 comprises 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 supplied directly to the filtration device 2, but a separate storage tank (not shown) may be installed to temporarily store the pumped seawater. In this case, the seawater may be stored after the sewage effluent has been discharged, or the seawater before the sewage effluent is supplied to and stored in the storage tank separately from the sewage effluent.

[0018] Sewage effluent discharged into sewage discharge areas is a treated liquid that has undergone biological treatment after solids have been removed from wastewater containing nutrients (such as nitrogen and phosphorus) such as human waste, sewage, and wastewater from food production and processing. Specifically, the liquid to be treated flowing into a sewage treatment plant is separated by sedimentation in a primary sedimentation tank, and the separated supernatant is biologically treated in a reaction tank supplied with oxygen, after which it is further separated by sedimentation in a final sedimentation tank. The supernatant may be disinfected before use.

[0019] The supernatant liquid discharged from water treatment facilities is generally discharged into the sea, 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 sea 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 feed on nutrients, proliferates there.

[0020] 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. The sewage discharge area in this embodiment is a closed water area with little water flowing in or out of the water from the outside, and is an ocean area where nutrients tend to accumulate.

[0021] As shown in Figure 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.

[0022] The filter layer 9 is formed by filling irregular granular fiber filter media, and captures suspended matter contained in seawater supplied from above the filter layer 9. Since the suspended matter in the seawater contains plant biomass, plant biomass can be obtained in the filter tank 7 by filtering the seawater. The suspended matter in the seawater also contains organic matter derived from the remains and feces of living organisms, but the purpose of this embodiment is to obtain plant biomass that can serve as food for marine organisms (bivalves).

[0023] The filter material is not limited to fiber material, and other filter materials such as resin filter material and sand may be used. The diameter and shape may also be 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.

[0024] A cleaning fluid supply pipe 5 is connected below the filter tank 7, so that cleaning fluid can be supplied from below the filter 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 filter tank 7 to clean the filter media, but if necessary, compressed air, a stirring blade, or the like may also be used in combination to agitate and clean the filter media. Furthermore, the cleaning fluid is not limited to seawater.

[0025] Furthermore, the filtration device 2 has a foam separation device 10 installed above the filtration tank 7. The foam separation device 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.

[0026] The foam separator 10 is composed of an air diffuser pipe connected at one end to an air supply source such as a blower or compressor (not shown), and by driving the air supply source, fine bubbles are sprayed into the seawater from a large number of nozzle holes 12 formed at the top of the air diffuser pipe. By supplying the fine bubbles to the seawater, suspended matter in the seawater floats up and is separated, forming stable foam on the water surface.

[0027] 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 plant biomass can be increased by performing foam separation. Note that the foam separator 10 is not limited to the aeration pipe type, as long as it generates fine bubbles.

[0028] 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 from a sewage discharge area and filtered, where the concentration of nutrients is relatively high.

[0029] Nori grown in seaweed farming areas absorbs nutrients to grow, so supplying a treatment solution with a high concentration of nutrients promotes the growth of the nori, resulting in the production of high-quality nori that does not lose its color.

[0030] If necessary, a return pipe 16 may be connected to the feeding section 4A as shown in Figure 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 solid matter load on the filtration device 2 even if the taken-in seawater contains suspended matter other than plant biomass.

[0031] Meanwhile, feeding section 4B is a pipe with one end connected to the top of filter 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 filter layer 9 can be supplied to the shellfish cultivation area together with the cleaning wastewater. The cleaning wastewater supplied to the shellfish cultivation area contains a large amount of plant biomass because it is seawater pumped from a sewage discharge area and has been filtered, where the amount of plant biomass is relatively high.

[0032] Oysters cultivated in shellfish farming areas grow by capturing plant biomass, so supplying washing wastewater, which contains a high amount of plant biomass, promotes oyster growth.

[0033] In this embodiment, when performing filtration using the above-mentioned filtration device 2, the net production amount of plant biomass contained in seawater taken by seawater pump 13 shown in Figure 1 is determined, and the amount of seawater taken is determined based on the net production amount. The dissolved oxygen concentration measured by measurement unit 14, which is a dissolved oxygen meter installed in the sewage discharge area, is sent to control unit 15, and control unit 15 sends a command to seawater pump 13. Note that measurement unit 14 may be installed in seawater supply pipe 6 as it is only necessary to measure the dissolved oxygen concentration of the liquid to be treated that is supplied to filtration device 2. Furthermore, the timing of measuring the dissolved oxygen concentration may be simultaneous with the start of the filtration process or prior to the filtration process. [Example]

[0034] The feed production method according to this embodiment will be described in detail below with reference to FIGS.

[0035] <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).

[0036] <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.

[0037] <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 bubbles are supplied from the nozzles 12 of the foam separator 10 toward the top of the filtration tank 7, while suspended solids are captured by the filter media layer 9 filled in the filtration tank 7. At this time, the valve V3 installed in the feeding section 4B is open.

[0038] The many fine bubbles that are ejected adsorb suspended matter mixed in the seawater supplied from above, as well as suspended matter that has naturally separated from the filter layer 9 due to the influence of water pressure, and rise to the water surface. Then, the bubbles that adsorb the suspended matter that rise one after another gather on the water surface, forming a stable foam on the water surface.

[0039] 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.

[0040] Foam separation is performed continuously during the filtration process, but the timing for starting the supply of compressed air is determined appropriately. The method for supplying stable foam from the feeding section 4B to the shellfish cultivation area can be selected appropriately, for example, by maintaining a constant water level in the filtration tank 7 and discharging the water by overflow 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.

[0041] 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 treated liquid from the feeding unit 4A to the seaweed cultivation area. The treated liquid supplied from the feeding unit 4A to the seaweed cultivation area contains fine bubbles sprayed from the foam separator 10, and supplying this treated liquid to the seaweed cultivation area promotes the growth of seaweed.

[0042] Filtration may also be performed using an upflow filtration device, in which 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 from the bottom of the filtration tank 7 to the shellfish cultivation area.

[0043] 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 plant biomass production Pn. The seawater pump 13 is then controlled based on the calculated net plant biomass production Pn to adjust the amount of seawater intake. The methods for calculating the net plant biomass production Pn and controlling the amount of seawater intake are described in detail below.

[0044] First, the net production amount of plant biomass Pn is calculated using 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 + 12 hours of dark 0TIME: Initial dissolved oxygen concentration measurement value

[0045] 12L+12D is the sum of the dissolved oxygen concentration measured in the sewage discharge area under 12 hours of light conditions and the dissolved oxygen concentration measured in the sewage discharge area under 12 hours of dark conditions during the filtration process. 0TIME indicates the initial dissolved oxygen concentration measured in the sewage discharge area before starting measurements of 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 of plant biomass in the sewage discharge area, Pn, can be calculated.

[0046] Next, a method for controlling the amount of seawater intake will be described in detail. A reference value Pn0 for the amount of net production of plant biomass with a predetermined range is set in advance. The net production Pn calculated using the above method is then compared with the preset reference value Pn0. If the calculated value Pn is higher than the reference value Pn0, the rotation speed of the seawater pump 13 is gradually reduced 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.

[0047] If the calculated value Pn is within the range of the reference value Pn0, operation continues while maintaining the rotation speed of the seawater pump 13. Note that PID control is used for control, and a predetermined adjustment amount α is increased or decreased in stages so that the calculated value Pn falls within the range of the reference value Pn0.

[0048] 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 (described below), and supplied to the shellfish cultivation area, ensuring a stable supply of feed to shellfish.

[0049] In addition, by constantly washing and recovering a constant amount of solid matter (plant biomass) in the filtration device 2 during the washing 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, ensuring a stable supply of feed to the seaweed.

[0050] In this embodiment, the amount of plant biomass contained in the sewage discharge area was calculated using the above formula. However, to determine the amount of plant biomass, control may be performed by comparing the measured chlorophyll fluorescence intensity with a predetermined reference value using a known chlorophyll fluorescence sensor, or by controlling the amount of plant biomass 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 images may be measured at any location between the sewage discharge area and the filtration device 2.

[0051] Although the amount of seawater intake at the sewage discharge area was controlled to maintain a constant net production Pn, the amount of sewage effluent discharged from the water treatment facility can also be controlled. Because sewage effluent contains nutrients such as nitrogen and phosphorus that serve as food for plant biomass, controlling the amount of sewage effluent makes it possible to adjust the net production of plant biomass.

[0052] 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 measurements are taken at predetermined intervals, the two measurements are used to calculate the net production Pn, and the calculated net production Pn is used to calculate the total production Pg and the respiration rate R, and whether the net production Pn is on an increasing or decreasing trend is predicted. The increase / decrease prediction control method is described in detail below.

[0053] First, to determine two consecutive dissolved oxygen concentration measurements, the dissolved oxygen concentration is measured at a predetermined measurement time Tn and immediately thereafter at Tn+1. Then, using these measurements, the net production volumes Pn and Pn+1 are calculated using the above formula (1).

[0054] Next, total production Pgn and total production Pgn+1 are calculated using the following (Equation 2). Here, in order to calculate each total production Pg, respiration rates Rn and Rn+1 are calculated using the following (Equation 3). Note that (Equation 2) is a modified version of the following (Equation 4) which calculates net production. Pg = Pn + R... (Equation 2) R=0TIME-24D…(Formula 3) Pn = Pg - R... (Equation 4) Pg: Total production of plant biomass Pn: Net production of plant biomass calculated using Equation 1 R: Respiration rate of plant biomass 0TIME: Initial dissolved oxygen concentration measurement value 24D: Dissolved oxygen concentration measured under 24-hour dark conditions

[0055] 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 measurement within the sewage discharge area. By subtracting the measured dissolved oxygen concentration from the initial dissolved oxygen concentration, the respiration rate of the plant biomass can be determined. After calculating the respiration rates Rn and Rn+1, these values ​​and the net production rates Pn and Pn+1 calculated using Equation 1 above 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.

[0056] The total production Pgn and Pgn+1 and respiration Rn and Rn+1 at each measurement time are calculated using the above formulas (1 to 3), and the calculated total production Pgn and Pgn+1 are compared. Furthermore, the ratio of respiration Rn to total production Pgn at time Tn is compared with the ratio of respiration Rn to total production Pgn at time Tn+1.

[0057] As shown in the following (Formula 5), for example, when a result is obtained where the total production volume Pgn+1 is larger than the total production volume Pgn, at time Tn+1, photosynthesis of plant biomass is actively occurring within the sewage discharge area, and it can be seen that a large amount of plant biomass is growing due to photosynthesis. Also, as shown in the following (Formula 6), when a result is obtained where the ratio of the respiration volume Rn+1 to the total production volume Pgn+1 is larger than the ratio of the respiration volume Rn to the total production volume Pgn, at time Tn+1, while the plant biomass is actively performing photosynthesis, the high respiration ratio indicates that a large amount of the energy obtained through photosynthesis is being consumed. Pgn < Pgn+1…(Formula 5) Rn / Pgn < Rn+1 / Pgn+1…(Formula 6)

[0058] From the above (Formulas 5 and 6), when the total production volume Pg and the respiration volume R in the total production volume Pg are large, since the energy consumption of the plant biomass is large, the net production volume Pn of the plant biomass calculated by subtracting the respiration volume from the total production volume is predicted to turn to a decreasing trend. On the other hand, at time Tn when the total production volume Pg and the respiration volume R in the total production volume Pg are smaller than at time Tn+1, since the amount of plant biomass is small and the energy consumption is also small, the net production volume Pn of the plant biomass is predicted to turn to an increasing trend.

[0059] In this way, by predicting whether the net production volumes Pn and Pn+1 at the predetermined times Tn and Tn+1 are on an increasing trend or a decreasing trend, the state of the net production volume of the plant biomass in the sewage discharge area can be grasped. And from the prediction results, when it is on an increasing trend, the rotation speed of the seawater pump 13 is gradually decreased to reduce the water intake amount, and when it is on a decreasing trend, the rotation speed of the seawater pump 13 is gradually increased to increase the water intake amount, so that a certain amount of plant biomass can be supplied to the filtration device 2.

[0060] <Filter material cleaning process> In the filter media cleaning process, the filter media layer 9 filled in the filter tank 7 is cleaned. A cleaning liquid is supplied from the downstream side of the filter media layer 9, and the water is passed through the filter media layer 9, and then discharged from the upstream side. This backwashing removes the plant biomass captured by the filter media layer 9. The removed plant biomass, together with the cleaning wastewater (seawater that has passed through the filter media layer 9) discharged from upstream of the filter media layer 9, is supplied to the shellfish cultivation area via the feeding section 4B.

[0061] 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 predetermined time or a predetermined time, or when the treated liquid no longer meets a predetermined 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.

[0062] Since seawater is used for washing, if a compressed air supply line is added below the washing fluid supply pipe 5, foam separation of the seawater supplied from the washing fluid supply pipe 5 will occur simultaneously with agitation washing. The agitation washing separates the plant biomass from 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.

[0063] In this embodiment, seaweed and oysters are listed, but the present invention is applicable to other marine organisms that feed on nutrients and plant biomass.

[0064] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. [Industrial Applicability]

[0065] The present invention is a useful technology for cultivating multiple marine organisms because it can constantly supply seawater containing a constant concentration of plant biomass to a feed production device, allowing for a stable supply of feed for multiple marine organisms.Furthermore, since this technology can be implemented simply by installing the feed production device in a specified sea area, it can be used in any sea area. [Explanation of symbols]

[0066] 2. Filtration equipment 13 Seawater pump Pn0: Reference value for net production of plant biomass Pn Measured net production of plant biomass

Claims

1. A method for feeding marine organisms, comprising: taking seawater from a sewage discharge area into which sewage effluent treated at a water treatment facility is discharged, filtering the filtered solution, feeding the seaweed culture area with suspended solids that have been removed during backwashing of the filter media, together with the washing effluent, to a shellfish culture area; A reference value (Pn0) of the amount of biomass is set with a predetermined range, During the filtration process, the amount of biomass contained in seawater taken from the sewage discharge area is measured. If the measured value (Pn) is higher than the reference value (Pn0), the rotation speed of the seawater pump (13) is gradually reduced, and If the measured value (Pn) is lower than the reference value (Pn0), the rotation speed of the seawater pump (13) is increased stepwise. Control the amount of biomass within the range of the reference value (Pn0) A method for controlling the amount of seawater intake supplied to a feed production device, comprising:

2. The amount of biomass is the net production amount of plant biomass calculated by the following formula (1) using the dissolved oxygen concentration in the sewage discharge area measured during the filtration treatment process.

2. A method for controlling the amount of seawater intake supplied to the feed producing device according to claim 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 measurement value

3. The amount of biomass is calculated from at least one of the measurement data of the chlorophyll fluorescence intensity measured during the filtration process and the captured image.

2. A method for controlling the amount of seawater intake supplied to the feed producing device according to claim 1.

4. A storage tank is installed to temporarily store seawater taken from the sewage discharge area, and the seawater is supplied from the storage tank to a filtration device (2). A method for controlling the amount of seawater intake supplied to the feed producing device according to any one of claims 1 to 3.

Images