Method for producing culture solution and culture solution production apparatus, and cultivation system including culture solution production apparatus

Abstract

To prevent the formation of precipitates even if bicarbonate ions are contained in water.SOLUTION: A method for producing culture solution includes: a first step involving the nitrification of water containing bicarbonate ions and ammonium carbonate, leading to the conversion of ammonia nitrogen in the water into nitrate nitrogen and the conversion of bicarbonate ions into carbon dioxide; and a second step involving the addition of a fertilizer component containing at least one element selected from nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, zinc, molybdenum, nickel, and copper to the water processed in the first step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One embodiment of the present invention relates to a method for removing bicarbonate ions from water containing bicarbonate ions, a method for producing a nitrogen fertilizer and a culture solution including the method, a culture solution producing device for producing a culture solution by treating water containing bicarbonate ions, and a cultivation system including the culture solution producing device. [Background technology]

[0002] Hydroponic cultivation of plants requires the application of fertilizers containing elements essential for plant growth, such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, zinc, molybdenum, nickel, and copper. In hydroponic cultivation, chemical fertilizers containing these essential elements are dissolved in water and used as the culture solution. The raw water used to prepare the culture solution contains bicarbonate ions (HCO3 - When the raw water contains a large amount of nitrite, the pH of the culture solution is increased, which requires complicated pH adjustment and frequent replacement of the culture solution. Therefore, it is said that it is a good idea to neutralize the raw water with nitric acid or phosphoric acid as a pretreatment to adjust the pH value of the raw water and reduce the bicarbonate ion concentration to about 20 to 50 ppm (see Non-Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] "VII Fertilizer and Nutrient Solution Management in Hydroponic Cultivation", Internet<http: / / www.pref.shizuoka.jp / sangyou / sa-325 / hiryou / documents / sehi16-dai3bu7.pdf> [Non-Patent Document 2] "Calculation method for hydroponics", Internet<https: / / www.kaneyama.co.jp / image / technical_data / technical_sheet_04.pdf> Summary of the Invention [Problem to be solved by the invention]

[0004] In hydroponic cultivation, bicarbonate ions contained in ammonium carbonate, potassium carbonate, water, etc. not only raise the pH value, but also combine with cations such as calcium ions contained in the nutrient solution to precipitate, which can lead to deposition in the nutrient solution tank or waterway, a decrease in fertilizer efficiency, a decrease in the quality of the nutrient solution, clogging and blocking of openings and pipes, and increased management costs, making pretreatment necessary.

[0005] When nitric acid or phosphoric acid is added to the raw water as a pretreatment step, as in the conventional technology, the fertilizer components must be adjusted by subtracting the amount of the added nitric acid or phosphate, which requires complex fertilizer calculations.

[0006] In view of such problems, one embodiment of the present invention aims to provide a method for removing bicarbonate ions from water containing bicarbonate ions. Another object of one embodiment of the present invention is to provide a method for treating water containing bicarbonate ions and a method for producing a culture solution, which prevents the formation of precipitates in the culture solution even if the water used to produce the culture solution contains bicarbonate ions when carbonates such as ammonium carbonate and potassium carbonate are used in the culture solution, and does not require complicated fertilizer calculations when adjusting the fertilizer. Another object of one embodiment of the present invention is to provide an apparatus for producing a culture solution, which prevents the formation of precipitates even if the water used to produce the culture solution contains bicarbonate ions when carbonates such as ammonium carbonate and potassium carbonate are used in the culture solution. [Means for solving the problem]

[0007] One embodiment of the present invention is a method for producing a culture solution that does not require complicated fertilizer calculations and prevents the formation of precipitates even if the raw water contains bicarbonate ions when carbonates such as ammonium carbonate and potassium carbonate are used in the culture solution. -) and nitrification of water containing ammonia ions, thereby converting ammonia nitrogen to nitrate nitrogen and bicarbonate ions to carbon dioxide.

[0008] The method for treating water containing bicarbonate ions according to one embodiment of the present invention is to treat bicarbonate ions (HCO - This involves adding ammonium carbonate ((NH4)2CO3) to water containing nitrification salts, converting ammonia nitrogen to nitrate nitrogen and bicarbonate ions into carbon dioxide.

[0009] One embodiment of the present invention involves measuring the pH value of a culture solution to which carbonates such as ammonium carbonate or potassium carbonate have been added, or water containing bicarbonate ions, which has been treated by nitrification (treated water), and, if the pH value of the culture solution or treated water falls below 4.5, adding at least one of ammonium carbonate ((NH4)2CO3) and carbonates such as potassium carbonate (K2CO3), calcium carbonate (CaCO3), and magnesium carbonate (MgCO3) to the culture solution or treated water to adjust the pH value of the culture solution or treated water to within the range of 4.5 to 6.5. Bicarbonate ions (HCO3 - Nitrification of water containing ammonium nitrate (NH4)2CO3) can be carried out using nitrifying bacteria.

[0010] The method for producing a culture medium according to one embodiment of the present invention includes the steps of: - The method includes a first step of adding ammonium carbonate ((NH4)2CO3) to water containing bicarbonate ions or a culture solution to which a carbonate such as potassium carbonate (K2CO3) has been added, and nitrifying the water to convert ammonia nitrogen contained in the water containing bicarbonate ions or the culture solution to which a carbonate has been added into nitrate nitrogen and converting bicarbonate ions into carbon dioxide, and a second step of adding a fertilizer component containing at least one element selected from nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, zinc, molybdenum, nickel, and copper to the treated water that has been subjected to the first step.

[0011] A method for producing a culture medium according to one embodiment of the present invention includes measuring the pH of water during nitrification treatment, and when the pH value of the treated water falls below 4.5, adding at least one of ammonium carbonate ((NH4)2CO3) and carbonates such as potassium carbonate (K2CO3), calcium carbonate (CaCO3), and magnesium carbonate (MgCO3) to the water during nitrification treatment to adjust the pH value of the treated water to within a range of 4.5 to 6.5. - Nitrification of water containing ammonium nitrate (NH4)2CO3) can be carried out using nitrifying bacteria.

[0012] The culture medium manufacturing device according to one embodiment of the present invention is a device for producing bicarbonate ions (HCO - The treatment system includes a pretreatment section that adds ammonium carbonate ((NH4)2CO3) to water containing nitrate-containing nitrogen or a culture solution to which carbonates such as potassium carbonate (K2CO3) have been added, thereby converting ammonia nitrogen contained in the treatment water into nitrate nitrogen and converting bicarbonate ions into carbon dioxide, and an adjustment section that adds a fertilizer component containing at least one element selected from nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, zinc, molybdenum, nickel, and copper to the treatment water that has been subjected to the first stage.

[0013] A culture medium manufacturing apparatus according to one embodiment of the present invention may include a pH sensor in the pretreatment section that measures the pH value of the treated water, and a first chemical supply section that adds ammonium carbonate ((NH4)2CO3) to the treated water. The culture medium manufacturing apparatus according to one embodiment of the present invention may also include a control section, and the control section may have a function of adding ammonium carbonate ((NH4)2CO3) from the first chemical supply section when the measured value of the pH sensor in the pretreatment section is less than 4.5 so that the pH value of the treated water is 4.5 or more and 6.5 or less. The pretreatment section may include at least one or both of an agitation section that agitates the treated water and an aeration section that aerates the treated water.

[0014] A hydroponic cultivation system according to one embodiment of the present invention includes a culture solution producing device including a pretreatment unit and an adjustment unit, and a cultivation tank for cultivating plants, and the culture solution is supplied to the cultivation tank from the adjustment unit. Effect of the Invention

[0015] According to one embodiment of the present invention, bicarbonate ions (HCO - By adding ammonium carbonate ((NH4)2CO3) to water containing nitrified water or to a culture solution to which carbonates such as potassium carbonate (K2CO3) have been added, it is possible to suppress an increase in pH value and remove bicarbonate ions. Furthermore, when using nitrified water as a culture solution, it is possible to suppress the formation of precipitates even if fertilizer components are added to adjust the solution. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram showing a configuration of a culture solution manufacturing apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a diagram showing a configuration of a hydroponic cultivation system according to an embodiment of the present invention. [Diagram 3] 1 is a graph showing the change in pH value of a culture solution used for cultivating a plant, as measured in Example 1. [Figure 4] 1 shows photographs of the state of precipitates in a culture solution used for cultivating a plant, as measured in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different aspects, and should not be interpreted as being limited to the description of the embodiments exemplified below. In order to make the explanation clearer, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual aspect, but they are merely examples and do not limit the interpretation of the present invention. In this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same reference numerals, and detailed explanations may be omitted as appropriate. Furthermore, the letters "first" and "second" attached to each element are convenient labels used to distinguish each element, and have no further meaning unless otherwise specified.

[0018] [First embodiment] 1 shows the configuration of a culture solution manufacturing apparatus 100 according to one embodiment of the present invention. The culture solution manufacturing apparatus 100 includes a pretreatment unit 102 and an adjustment unit 104. The pretreatment unit 102 has a pretreatment tank 106 in which water (pretreated water 110) for producing nitrogen fertilizer (or culture solution) is stored. The adjustment unit 104 has an adjustment tank 108 in which fertilizer components and the like are added to the water (pretreated water 110) that has been subjected to a predetermined treatment in the pretreatment tank 106, thereby producing a culture solution 112.

[0019] The pretreatment tank 106 and the adjustment tank 108 are connected by a first pipe 116. A first valve 120 for controlling the flow of the solution is provided in the first pipe 116. The flow of pretreated water (pretreated water 110) from the pretreatment tank 106 to the adjustment tank 108 is controlled by opening and closing the first valve 120. The pretreated water 110 may be supplied from the pretreatment tank 106 to the adjustment tank 108 via a pump (not shown), or may be supplied by utilizing the difference in water levels between the two tanks. The culture solution producing apparatus 100 has a control unit 114, and the first valve 120 may be opened and closed by a signal output from the control unit 114. The first pipe 116 may also be provided with a filter 118 for removing fine particles.

[0020] Water (raw water: water before treatment) for producing nitrogen fertilizer (or culture solution) is supplied to the pretreatment tank 106 from a treated water supply unit 122. There is no limitation on the raw water supplied from the treated water supply unit 122, and various types of water can be used, including river water or groundwater, secondary treated water from domestic wastewater, and industrial wastewater. The raw water supplied from the treated water supply unit 122 contains bicarbonate ions (HCO3 - The treated water supply unit 122 may be connected to a water tank or tank (not shown) for storing raw water.

[0021] The treated water supply unit 122 and the pretreatment tank 106 are connected by piping, and a first water supply pump 134 and a second valve 128 are provided in the piping path. The supply of raw water from the treated water supply unit 122 to the pretreatment tank 106 is controlled by driving the first water supply pump 134 and opening and closing the second valve 128. The operation of the first water supply pump 134 and the opening and closing of the second valve 128 are controlled by the control unit 114.

[0022] The pretreatment tank 106 is connected to a first chemical supply unit 124. The first chemical supply unit 124 has a function of supplying the first chemical to the pretreatment tank 106. In this embodiment, the first chemical is ammonium carbonate ((NH4)2CO3), and may be supplied from the first chemical supply unit 124 as an aqueous ammonium carbonate solution. The first chemical supply unit 124 may be connected to a first chemical tank (not shown) and configured to supply the first chemical from the first chemical tank.

[0023] The first chemical supply unit 124 and the pretreatment tank 106 are connected by piping. A second water pump 136 and a third valve 130 are provided in the piping path. The supply of the first chemical from the first chemical supply unit 124 to the pretreatment tank 106 is controlled by driving the second water pump 136 and opening and closing the third valve 130. The operation of the second water pump 136 and the opening and closing of the third valve 130 are controlled by the control unit 114. Note that the second water pump 136 is omitted when ammonium carbonate powder is supplied to the pretreatment tank 106.

[0024] A second chemical supply unit 126 may be connected to the pretreatment tank 106. The second chemical supply unit 126 has a function of supplying the second chemical to the pretreatment tank 106. The second chemical may contain a component that serves as a fertilizer for plants, and may contain, for example, potassium carbonate (K2CO3), calcium carbonate (CaCO3), magnesium carbonate (MgCO3), and the like. The second chemical supply unit 126 has one or more chemical supply systems, and supplies one or more aqueous solutions selected from potassium carbonate or potassium carbonate aqueous solution, calcium carbonate or calcium carbonate aqueous solution, magnesium carbonate and magnesium carbonate aqueous solution to the pretreatment tank 106. The second chemical supply unit 126 may be connected to a second chemical tank (not shown) and configured to supply the second chemical from the second chemical tank.

[0025] The second chemical supply unit 126 and the pretreatment tank 106 are connected by piping. A third water supply pump 138 and a fourth valve 132 are provided in the piping path. The supply of the second chemical from the second chemical supply unit 126 to the pretreatment tank 106 is controlled by driving the third water supply pump 138 and opening and closing the fourth valve 132. The operation of the third water supply pump and the opening and closing of the fourth valve 132 are controlled by the control unit 114.

[0026] Nitrifying bacteria are added to the pretreatment tank 106. The nitrifying bacteria are provided in the pretreatment tank 106 directly, together with a carrier containing the nitrifying bacteria, by being contained in sludge or soil. The nitrifying bacteria are added at a volume ratio of 5 to 20%, for example 10%, to the pretreated water 110. FIG. 1 shows an embodiment in which a carrier 146 containing nitrifying bacteria is provided to the pretreatment tank 106. The pretreatment tank 106 contains the nitrifying bacteria, so that it can nitrify the bicarbonate ions and ammonium carbonate contained in the pretreated water 110. That is, water containing bicarbonate ions and ammonium carbonate can be nitrified by the nitrifying bacteria, and ammonia nitrogen can be converted to nitrate nitrogen and bicarbonate ions to carbon dioxide, which can be used as nitrogen fertilizer components.

[0027] The pretreatment tank 106 is provided with an agitator 140 so that the reaction caused by the nitrifying bacteria proceeds in the pretreated water 110. There is no limitation on the type of the agitator 140, and for example, a propeller type agitator can be used. By agitating the pretreated water 110 with the agitator 140, the nitrification reaction can be promoted. Also, instead of the agitator 140, a submersible pump may be installed in the pretreatment tank 106 so that the pretreated water 110 is circulated within the tank.

[0028] The pretreatment tank 106 may be provided with an aeration device 142 for aeration. The aeration device 142 is composed of an air pump 143 for sending air and a micro-porous body 144 such as an air stone or a micro-nano bubble nozzle. The micro-porous body 144 is preferably provided at the bottom of the pretreatment tank 106. By sending air from the bottom of the pretreatment tank 106 using the aeration device 142, it is possible to promote reactions in which ammoniacal nitrogen is converted into nitrate nitrogen, bicarbonate ions are converted into carbon dioxide, and organic matter is oxidized to water and carbon dioxide.

[0029] The pretreatment tank 106 is provided with sensors for detecting the state of the pretreated water 110. FIG. 1 shows an example in which a pH sensor 148, an EC sensor 150, and a water level sensor 152 are provided as sensors in the pretreatment tank 106. The pH sensor 148 is provided to measure the pH value of the pretreated water 110. In order to maintain a continuous nitrification reaction, it is preferable that the pH value of the pretreated water 110 in the pretreatment tank 106 is controlled to be in the range of 4.5 to 6.5. The pH sensor 148 monitors the pH value of the pretreated water 110, thereby enabling the nitrification reaction to be carried out under appropriate conditions. The measured value of the pH sensor 148 is output to the control unit 114.

[0030] The EC sensor 150 is used to measure the electrical conductivity of the pretreated water 110. The ion concentration can be evaluated by measuring the electrical conductivity of the pretreated water 110 with the EC sensor 150. In addition, a nitrate ion sensor and an ammonia ion sensor may be provided to directly measure nitrate ions and ammonia ions.

[0031] The water level sensor 152 is provided to detect the water level in the pretreatment tank 106. The measurement value of the water level sensor 152 is output to the control unit 114. When raw water is supplied to the pretreatment tank 106, the control unit 114 controls the operation of the treated water supply unit 122 based on the signal from the water level sensor 152, so that the water level does not exceed a predetermined level.

[0032] The adjusting unit 104 is provided with an agitator 141 that agitates the culture solution 112 in the adjusting tank 108, a nutrient solution supplying device 154 that adds fertilizer components to the culture solution 112, a nutrient solution adjusting device 156 that controls the operation of the nutrient solution supplying device 154, and a water level sensor 153. The nutrient solution adjusting device 156 includes sensors (pH sensor 149, EC sensor 151). The nutrient solution adjusting device 156 detects the pH value of the culture solution 112 by the pH sensor 149, and detects the electrical conductivity of the culture solution 112 by the EC sensor 151. The nutrient solution adjusting device 156 adds fertilizer components including components such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, zinc, molybdenum, nickel, and copper from the nutrient solution supplying device 154 to the culture solution 112 based on the measured values ​​of these sensors. The adjusting tank 108 is provided with a water supply port 158, through which the stored culture solution 112 is supplied to the outside.

[0033] The control unit 114 has a function of controlling the operation of the pretreatment unit 102 and the adjustment unit 104, and collecting data on the pretreated water 110 and the culture solution 112. Furthermore, the control unit 114 controls the treatment conditions of the pretreated water 110 based on the collected data, and manages the quality of the culture solution 112.

[0034] According to the culture solution manufacturing apparatus 100 of this embodiment, raw water of various water qualities can be used by treating the water (raw water) used for producing nitrogen fertilizer (or culture solution) with nitrifying bacteria in the pretreatment unit 102. That is, even if the raw water contains bicarbonate ions, it can be converted to carbon dioxide. In addition, ammonium carbonate contained in the pretreated water 110 can be converted to nitrate nitrogen to be used as a nitrogen fertilizer component. This makes it possible to suppress an increase in the pH value of the pretreated water 110, and to suppress the formation of precipitates even when the culture solution is adjusted by adding fertilizer components in the adjustment unit 104. This makes it possible to suppress an increase in the pH value of the culture solution 112, and to prevent the formation of precipitates in the adjustment tank 108, which are deposited on the openings of pipes, etc., causing clogging or blockage.

[0035] [Second embodiment] This embodiment describes the operation of the culture solution manufacturing apparatus 100 shown in the first embodiment, a method for treating water containing bicarbonate ions using this apparatus, nitrogen fertilizer produced by this apparatus, and a method for producing a culture solution.

[0036] In the culture solution manufacturing apparatus 100, water (raw water) to be used in the production of nitrogenous fertilizer (or culture solution) is treated in the pretreatment unit 102, and the nitrogenous fertilizer (or culture solution) is adjusted in the adjustment unit 104. First, water is supplied from the treated water supply unit 122 to the pretreatment tank 106. The water supplied to the pretreatment tank 106 is the water to be used in the production of nitrogenous fertilizer (or culture solution). As described in the first embodiment, various types of water (such as wastewater) can be used as this water, and the water may contain bicarbonate ions.

[0037] Simultaneously with or after the supply of raw water from treated water supply unit 122, an aqueous ammonium carbonate solution is supplied from first chemical liquid supply unit 124 to pretreatment tank 106. Nitrifying bacteria, a carrier containing nitrifying bacteria, sludge containing nitrifying bacteria, or soil are added in an amount of 10% or more by volume to pretreated water 110 containing ammonium carbonate and bicarbonate ions introduced into pretreatment tank 106. The nitrifying bacteria, the carrier containing nitrifying bacteria, the sludge containing nitrifying bacteria, or soil may be placed in pretreatment tank 106 in advance.

[0038] Next, the agitator 140 is operated to agitate the pretreated water 110, promoting the nitrification reaction by the nitrifying bacteria. Aeration by the aeration device 142 may be performed instead of agitation. The nitrification reaction by the nitrifying bacteria can be promoted by aerating the pretreated water 110 by the aeration device 142. In addition, the treatment of reacting the pretreated water 110 with the nitrifying bacteria may be performed by simultaneously performing agitation and aeration, or by alternating between agitation and nitrification. The pretreated water 110 containing ammonium carbonate and bicarbonate ions is agitated or aerated, or agitated and aerated, so that the ammonium ions contained in the pretreated water 110 can be converted into nitrate ions by nitrification, and the bicarbonate ions can be converted into carbon dioxide.

[0039] The pH value of the pretreated water 110 is measured by a pH sensor 148 and is controlled so that the pH value is within the range of 4.5 to 6.5. If the pH value falls below 4.5, an aqueous solution of ammonium carbonate is added to the pretreated water 110 from the first chemical supply unit 124 to raise the pH value. If the pH value rises to 6.5 or higher, the addition of ammonium carbonate is discontinued.

[0040] The nitrification reaction of the pretreated water 110 may be monitored by an EC sensor 150 (or a nitrate ion sensor, or an ammonia ion sensor). The quality of the pretreated water 110 can be controlled by adding ammonium carbonate while measuring the electrical conductivity of the pretreated water 110 with the EC sensor 150, and interrupting the addition of ammonium carbonate when the measured value (EC value) of the EC sensor 150 reaches a predetermined value. The control level of electrical conductivity by the EC sensor 150 is determined by the EC value set in the culture solution. For example, if the EC value of the culture solution 112 is to be 1.5 or more and 2.0 or less, the addition of ammonium carbonate is interrupted when the EC value of the pretreated water 110 in the pretreatment tank 106 reaches 0.4 dS / m.

[0041] By the above-mentioned treatment, bicarbonate ions can be removed from water containing bicarbonate ions. This water treatment method can also adjust the pH value of the water from which bicarbonate ions have been removed. In other words, when adding ammonium carbonate to water from which bicarbonate ions are to be removed, the amount of ammonium carbonate added can be controlled so as not to be excessive.

[0042] The water level of the pretreated water 110 in the pretreatment tank 106 is monitored by a water level sensor 152. When the water level in the pretreatment tank 106 drops, raw water (raw water) is supplied from the treated water supply unit 122 until the water level reaches a predetermined level.

[0043] The pretreated water 110, whose pH value has been adjusted to 4.5 to 6.5 in the pretreatment tank 106, is transferred to the adjustment tank 108. The water level in the adjustment tank 108 is measured by a water level sensor 153, and when the water level in the adjustment tank 108 falls below a predetermined level, the pretreated water 110 is supplied. The opening and closing of the first valve 120 is controlled by a signal output from the control unit 114. The pretreated water 110 is supplied from the pretreatment tank 106 to the adjustment tank 108 through the first pipe 116. The pretreated water 110 is supplied, for example, by utilizing the water level difference between the pretreatment tank 106 and the adjustment tank 108. When there is a water level difference between the pretreatment tank 106 and the adjustment tank 108, the first valve 120 is opened, and the pretreated water 110 flows from the pretreatment tank 106 to the adjustment tank 108 through the first pipe 116. Alternatively, a method of pumping the pretreated water 110 from the pretreatment tank 106 using a pump (not shown) may be used. The pretreated water 110 is supplied to the equalization tank 108 until the water level reaches a predetermined level. The water level of the equalization tank 108 is monitored by a water level sensor 153.

[0044] When the pretreated water 110 is supplied from the pretreatment tank 106 to the adjustment tank 108, the stirring or aeration or the stirring and aeration process is stopped for about 5 to 10 minutes, and the pretreated water 110 is supplied after the solid matter suspended in the pretreated water 110 has settled. That is, the supernatant of the pretreated water 110 after the stirring or aeration or the stirring and aeration process is transferred to the adjustment tank 108. The first piping 116 is provided with a first filter 118, but if the pretreated water 110 is supplied without the suspended matter having settled, the first filter 118 will quickly become clogged, so it is preferable to carry out the stirring or aeration process after a predetermined time has elapsed, as described above.

[0045] The pretreatment tank 106, whose water level has dropped, is replenished with water (raw water) from the treated water supply unit 122. The amount of replenished water (raw water) is controlled by a water level sensor 152. After the water (raw water) is replenished, the quality of the pretreated water 110 stored in the pretreatment tank 106 is monitored by a pH sensor 148 and an EC sensor 150, and ammonium carbonate is added from the first chemical supply unit 124 as necessary. If the pH value is 4.5 or lower, ammonium carbonate is added from the first chemical supply unit 124, and the addition of ammonium carbonate is interrupted when the pH value reaches 6.5 or higher. Agitation or aeration, or agitation and aeration, are performed as appropriate.

[0046] The pretreated water 110 transferred to the adjustment tank 108 contains nitrate nitrogen resulting from the nitrification of ammonium carbonate. Therefore, this aqueous solution can be used as nitrogen fertilizer or as a raw material for nitrogen fertilizer.

[0047] In addition, a culture solution 112 for use in plant cultivation can be produced by adding fertilizer components to the pretreated water 110 transferred to the adjustment tank 108. The pH value and EC value of the culture solution 112 are measured by a pH sensor 149 and an EC sensor 151 connected to a nutrient solution adjustment device 156. The fertilizer components are added to the adjustment tank 108 by a nutrient solution supply unit 154. The fertilizer components include nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, It contains one or more components selected from zinc, molybdenum, nickel, and copper.

[0048] By using the culture solution producing apparatus 100 shown in this embodiment, ammonium carbonate can be added to water containing bicarbonate ions, and nitrification can be performed using nitrifying bacteria to convert the ammonium carbonate into nitrate nitrogen, convert the bicarbonate ions into carbon dioxide, and adjust the pH value to within the range of 4.5 to 6.5. In other words, by nitrifying water containing ammonium carbonate using nitrifying bacteria, a nitrogen fertilizer containing nitrate nitrogen can be produced, and a fertilizer component can be added to produce the culture solution 112. In addition, by using the culture solution producing apparatus 100 shown in this embodiment, bicarbonate ions can be removed in a simple manner from water (raw water) containing carbonate ions and bicarbonate ions that are likely to combine with cations in the culture solution and precipitate, and complicated fertilizer calculations can be eliminated by not using nitric acid, phosphate, etc.

[0049] The pretreated water 110 transferred from the pretreatment tank 106 has been treated with nitrifying bacteria to remove bicarbonate ions, so that even if fertilizer components such as calcium are added, it is possible to prevent the generation and deposition of precipitates. Furthermore, because ammonium carbonate is converted to nitrate nitrogen, the pH value of the culture solution 112 can be adjusted to a range of 4.5 to 6.5, and the fertilizer efficiency can be maintained. Furthermore, by converting ammonium carbonate to nitrate ions, the ammonia ion concentration can be reduced, making it possible to cultivate plants that do not like nutrient solutions with high ammonia concentrations.

[0050] [Third embodiment] FIG. 2 shows a hydroponic cultivation system 160 according to one embodiment of the present invention. The hydroponic cultivation system 160 includes the culture solution manufacturing apparatus 100 shown in the first embodiment and a cultivation section 161 in which plants are cultivated. There are two known types of hydroponic cultivation methods, namely, a flooded liquid hydroponic method and a thin film hydroponic method. FIG. 2 shows an example in which the flooded liquid hydroponic method is applied to the cultivation section 161 of the hydroponic cultivation system 160. Of course, the thin film hydroponic method can also be applied to the hydroponic cultivation system 160. Since the culture solution manufacturing apparatus 100 is described in the first embodiment and the method for producing the culture solution is described in the second embodiment, the description will be focused on the parts related to the cultivation tank 162 in this embodiment.

[0051] The culture solution 112 is supplied to the cultivation tank 162 from the adjustment tank 108. The culture solution 112 is supplied from the adjustment tank 108 to the cultivation tank 162 by a pump 157. The culture solution 112 is supplied to the cultivation tank 162 through a supply pipe 166. A cultivation panel 164 is installed on top of the cultivation tank 162. The plants 200 to be cultivated are arranged on the cultivation panel 164 and cultivated so that their roots extend into the cultivation tank 162.

[0052] 2 shows a case where the hydroponic cultivation system 160 is of a circulation type. An overflow pipe 168 is provided in the cultivation tank 162, and a waterway is formed in which the culture solution that has reached a predetermined water level flows out from the overflow pipe 168 and circulates to the adjustment tank 108. Although not shown, the waterway may be provided with a storage tank that temporarily stores the culture solution that has flowed out from the overflow pipe 168. Note that, while FIG. 2 shows an example in which the cultivation tank 162 is a single stage, the present invention is not limited to this and the cultivation tanks 162 may be arranged in multiple stages.

[0053] In the adjustment tank 108, fertilizer components necessary for hydroponic cultivation are added to the culture solution from a nutrient solution supply unit 154. In the adjustment tank 108, the pH value is measured by a pH sensor 149, and the EC value is measured by an EC sensor 151, and the water quality is managed so that it is within a range suitable for the culture solution 112. When the water level in the adjustment tank 108 drops, treated pretreated water 110 is supplied from the pretreatment tank 106. In this way, the amount of culture solution 112 is managed in the adjustment tank 108, and the reduced amount is supplied from the pretreatment tank 106, allowing hydroponic cultivation to be performed continuously.

[0054] According to the hydroponic cultivation system 160 of this embodiment, raw water of various water qualities can be used by treating the water (raw water) used to produce the culture solution with nitrifying bacteria. That is, even if the raw water contains bicarbonate ions, these can be converted into carbon dioxide. In addition, ammonium carbonate contained in the pretreated water 110 can be converted into nitrate nitrogen to be used as a nitrogen fertilizer component. Even if the culture solution 112 is produced by adding fertilizer components to the culture solution in the adjustment unit 104, the generation of precipitates can be suppressed. This can prevent the deposition of precipitates in water channels such as the adjustment tank 108 and the supply pipe 166, causing clogging and blockage. EXAMPLES

[0055] 11 shows changes in pH value of a culture solution produced by the production method shown in the second embodiment and a normal culture solution when a plant is grown in the culture solution.

[0056] Hydroponic cultivation was performed using the irrigation method. The cultivation was performed indoors on a cultivation rack with artificial lighting. Container lettuce was grown as the plant. Four types of culture solutions were used as the culture solution.

[0057] The culture medium and its composition are as follows. Sample A: Culture solution in which nitrate ions were generated from ammonium carbonate to prepare the culture solution. Sample B: The culture solution was first prepared using nitrate ions produced from ammonium carbonate, and then ammonium carbonate was used to prepare the culture solution when top dressing was applied. Sample C: Comparative example, culture solution made from chemical fertilizer Sample D: Comparative example, culture solution in which ammonium carbonate was used to adjust the culture solution

[0058] The graph in Figure 3 shows the change in pH value of the culture solution when container lettuce was cultivated using Sample A and Sample B. The graph in Figure 3 also shows the results of Comparative Examples Sample C and Sample D. Cultivation was carried out twice over a 43-day cultivation period, with the first period being from the 1st to the 22nd and the second period being from the 22nd to the 43rd.

[0059] When the culture solutions of Sample A and Sample B were used, the pH value remained within the range of 5 to 7 during the first and second periods of container lettuce cultivation, with no significant fluctuations observed. On the other hand, when the culture solution of Sample C, which is a comparative example, was used, it was confirmed that the pH value increased significantly after moving from the first period to the second period. A significant increase in pH value was also confirmed in the culture solution of Sample D, which is a comparative example.

[0060] The large change in pH value in sample C of the comparative example is believed to be the result of the container lettuce growing there absorbing a large amount of specific components contained in the nutrient solution, causing the ion balance in the nutrient solution to change from the initial state. The change in the pH value of sample C of the comparative example, which increased to 7 or more, is due to, for example, the absorption of components such as nitrate nitrogen contained in the nutrient solution, which causes OH to be released from the roots. - It is presumed that this is the result of the excretion of H. When a component such as ammonia nitrogen is absorbed, H + is discharged, and the pH value drops. On the other hand, in the culture solutions of Samples A and B of the Example, the pH value is stabilized at 4.5 to 6.5 due to nitrification by the nitrifying bacteria, and the presence of an appropriate amount of ammonia nitrogen in the culture solution provides a good balance between the absorption of nitrate nitrogen and ammonia nitrogen by the plant, which is thought to prevent a sudden change in the pH value. Furthermore, it is thought that the remaining nitrifying bacteria nitrify the ammonia nitrogen and act as a buffer, thereby preventing a sudden change in the pH value.

[0061] Thus, according to this example, it was confirmed that a sudden change in pH value was suppressed when a culture solution pretreated with nitrifying bacteria was used. EXAMPLES

[0062] The culture solutions of Samples A and B used in Example 1 and the culture solutions of Samples C and D used as comparative examples were observed for the presence or absence of precipitates after 43 days of use.

[0063] No precipitates were observed in the culture fluids of samples A and B, and the culture fluids were clear. On the other hand, precipitates were observed in the culture fluids of samples C and D, which are comparative examples. These results confirmed that by treating the pretreated water with nitrifying bacteria, carbonate ions and bicarbonate ions are removed, and the occurrence of precipitates due to reactions with fertilizer components can be prevented.

[0064] As described above, according to Examples 1 and 2, it was confirmed that the use of nitrifying bacteria to remove ammonium carbonate and bicarbonate ions contained in the pretreated water stabilizes the pH value of the culture solution and prevents the formation of precipitates. [Explanation of symbols]

[0065] 100: culture medium producing device, 102: pretreatment section, 104: adjustment section, 106: pretreatment tank, 108: adjustment tank, 110: pretreated water, 112: culture medium, 114: control section, 116: first pipe, 118: first filter, 120: first valve, 122: treated water supply section, 124: first chemical supply section, 126: second chemical supply section, 128: second valve, 130: third valve, 132: fourth valve, 134: first water pump, 136: second water pump, 138: third water pump, 140: agitator, 1 41: Agitator, 142: Aeration device, 143: Air pump, 144: Microporous body, 146: Carrier containing nitrifying bacteria, 148: pH sensor, 149: pH sensor, 150: EC sensor, 151: EC sensor, 152: Water level sensor, 153: Water level sensor, 154: Nutrient solution supply unit, 156: Nutrient solution adjustment device, 157: Pump, 158: Water supply port, 160: Hydroponic cultivation system, 161: Cultivation unit, 162: Cultivation tank, 164: Cultivation panel, 166: Supply pipe, 168: Overflow pipe, 200: Plant

Claims

1. A first stage of nitrifying water containing bicarbonate ions and ammonium carbonate to convert ammonia nitrogen contained in the water into nitrate nitrogen and bicarbonate ions into carbon dioxide; and a second step of adding a fertilizer component containing at least one element selected from nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, zinc, molybdenum, nickel, and copper to the water that has been subjected to the first step.

2. The method for producing a culture medium according to claim 1, further comprising the steps of: measuring a pH of the water; and, if the pH value of the water falls below 4.5, adding at least one of carbonates of ammonium carbonate and potassium carbonate to the water to adjust the pH value of the water to within a range of 4.5 to 6.

5.

3. The method for producing a culture medium according to claim 1 or 2, wherein the nitrification is carried out by nitrifying bacteria.

4. 4. The method for producing a culture medium according to claim 1, wherein the first step is carried out in a first treatment tank, the water that has undergone the first step is supplied to a second treatment tank, and the second step is carried out in the second treatment tank.

5. a pretreatment section that nitrifies water containing bicarbonate ions and ammonium carbonate to convert ammonia nitrogen contained in the water into nitrate nitrogen and bicarbonate ions into carbon dioxide; and an adjustment unit that adds a fertilizer component containing at least one element selected from nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, zinc, molybdenum, nickel, and copper to the water supplied from the pretreatment unit.

6. The culture medium producing apparatus according to claim 5 , wherein the pretreatment section includes a pH sensor that measures a pH value of the water, and a first chemical supply section that adds ammonium carbonate to the water.

7. The culture medium producing apparatus according to claim 6, further comprising a control unit that adds ammonium carbonate from the first chemical supply unit so that the pH value of the water is 4.5 or more and 6.5 or less when the measured value of the pH sensor is less than 4.

5.

8. The culture medium producing apparatus according to claim 6 , wherein the pretreatment section further includes a second chemical supply section that adds a carbonate to the water.

9. The culture medium producing apparatus according to claim 5 , wherein the pretreatment section includes at least one of an agitation section that agitates the water and an aeration section that aerates the water, or both of these.

10. The culture solution producing apparatus according to any one of claims 5 to 9, A cultivation tank for cultivating plants; Including, A cultivation system, characterized in that a culture solution is supplied to the cultivation tank from the adjustment unit.

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