JP2005304485A - Method for preparing culture solution for hydroponics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To circulate and reuse a culture solution for hydroponics, such as tank farming, by solving such problems that conventional culture solutions are often disposed of without being circulated, or disposed of after being circulated in a short time, because troubles of difficulty in pH control of the culture solution, accumulation of unnecessary nutrients, contamination of pathogenic bacteria into raw water and the circulated culture solution, etc., are caused when the cultured solution is circulated and reused, and therefore circulation and reuse of the culture solution is desired from viewpoints of stabilization of quality, recycling of resources, cost reduction, and prevention of environmental pollution caused by disposal of the solution, etc. <P>SOLUTION: This culture solution for the hydroponics, such as the tank farming, is prepared by applying a direct current to the culture solution used as an electrolyte with the aid of insoluble electrodes and directly electrolyzing the culture solution, so that effects of controlling a pH of the culture solution for the hydroponics, supplying the culture solution with oxygen, removing the accumulated nutrients, sterilizing the solution, etc., are produced. Therefore, the solution is recycled and utilized again as the culture solution for the hydroponics. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention uses a culture medium for hydroponics such as hydroponics as an electrolyte, and directly electrolyzes it by energizing a direct current using an insoluble electrode. The present invention relates to a method of circulating use as a culture solution for hydroponics.

In recent years, hydroponic cultivation of vegetables, confectionery, etc. has increased due to demands for land productivity, product quality uniformity, and product safety. In particular, from the viewpoints of environmental conservation, fertilizer saving, and prevention of environmental pollution due to waste water, the number of methods for circulating and using the culture solution is increasing. However, if the concentration of fertilizer, etc. in the culture solution is repeatedly adjusted when the culture solution is circulated, the pH will deviate from the target value due to accumulated residual fertilizer and organic matter, and the pH will be adjusted to an appropriate value. In order to do this, it is necessary to add an acid or an alkali. Although it is important to adjust the pH to an appropriate value in the growth stage of the plant, the culture solution that cannot be adjusted due to accumulation of acid and alkali must be discarded finally. Furthermore, when pathogenic bacteria are mixed in raw water or circulating culture solution, it grows within a short time, and the entire cultivated product has to be disposed of by disposal such as incineration. .

As a method for adjusting the pH of the culture solution, there is no method other than the method using acid or alkali. Well water and tap water are used as the raw water used for the preparation of the culture solution, but the well water sometimes shows an extreme pH value and hardness, and tap water is mainly used. The tap water is often set to be slightly higher for the purpose of preventing rusting and decay of the piping, and may show a pH of about 7.5 to sometimes 8 or higher.

In addition, when a fertilizer nutrient solution is prepared, although depending on the fertilizer concentration, the pH rises again due to the consumption of the fertilizer although a slight pH decrease is observed. Furthermore, depending on the type of medium material, the pH of the culture solution increases. Therefore, in practice, acids such as phosphoric acid and sulfuric acid are added to lower the pH of the culture solution. In order to grow plants, it goes without saying that the management of fertilizer concentration by measuring the electrical conductivity of the culture solution and the management of the culture solution by pH measurement are indispensable, but pH adjustment by adding strong acids such as phosphoric acid and sulfuric acid is not possible. It is not only dangerous, including the storage of chemicals, but also difficult to adjust the pH of a large amount of culture solution.

On the other hand, as a method for sterilizing a culture solution, a method using a drug or a method using heat sterilization has been studied. In the method using a medicine, it is necessary to use several kinds of medicines according to the type of pathogenic bacteria, and there are problems such as an effect on the human body due to accumulation of agricultural chemicals and an increase in cost.

Patent Document 1 discloses a technique for sterilizing a nutrient solution, a method in which waste liquid that has passed through a cultivation tank is sterilized by electrolysis and then mixed, circulated and reused again. The technique discloses that it is achieved by the bactericidal action of both “electric field between electrodes” and “hypochlorous acid generated at the anode” during the electrolytic treatment. According to Patent Document 1, the production of the hypochlorous acid is based on the weak alkaline hypochlorous acid production method disclosed in Patent Document 2. However, the versatile sodium hypochlorite treatment can be applied to equipment, materials, seeds, etc. before the start of cultivation, but it can continue to be used during cultivation because it can cause root rot due to accumulation of hypochlorous acid, etc. I can't do it.

Furthermore, as disclosed in Patent Document 2, when hypochlorous acid is produced by an electrolysis method using an aqueous solution containing chlorine ions such as sodium chloride and potassium chloride, the liquidity of the electrolytic solution becomes alkaline. Phenomenon such as hypochlorous acid accumulation and alkalinization of culture solution is an operation in which raw water containing chlorine ions such as well water and tap water is supplied as the culture solution is circulated and reused. Repeatedly, it proceeds rapidly by the concentration of chloride ions. As a result, high concentration of hypochlorous acid is generated by electrolysis, and at the same time, the pH of the culture broth rises and becomes strong alkali, making it impossible to adjust the pH of the broth and causing root rot of cultivated plants. Problems occur. Therefore, the technique disclosed in Patent Document 1 cannot circulate and reuse the culture solution over a long period of time.

Patent Document 1 does not describe anything about the electrode material or the like. It goes without saying that the electrode reaction that occurs depends on the electrode catalyst used for electrolysis. For example, when a nickel electrode or a SUS electrode is used as an anode, hypochlorous acid is not produced, iron or the like, which is a component of nickel or SUS, dissolves, and further, the dissolved ions undergo a hydrolysis reaction, The liquid may be an acidic aqueous solution.

In addition, UV and ozone gas sterilizers are also available on the market, but UV cannot sterilize sufficiently when the optical path is short or light cannot be irradiated, and ozone gas dissolves in the culture medium. Since the amount of ozone is small and ozone reacts with organic substances and a sufficient amount for sterilization cannot be obtained in the culture solution, it is insufficient as a method for sterilization of the culture solution.

Recently, a “hydroponic cultivation nutrient sterilizer” using a heating method using a carbon dioxide heat pump as shown in Non-Patent Document 1 has been developed. This technique is a method for sterilizing a culture solution by heating the culture solution, and although it is an extremely effective means for sterilizing a culture solution, the apparatus is large and expensive. Further, if the culture solution is circulated and reused, accumulation of unnecessary components becomes a problem, and it is impossible to use the culture solution for a long period of time.

As described above, the conventional method is not widely used because it leads to cost increase due to the viewpoint of reducing agricultural chemicals and the size of the apparatus.

JP 2002-51651 PR JP 11-239791 PR SANYO TECHNICAL REVIEW VOL.35 NO.2 DEC. 2003

The present invention relates to a method for preparing a culture solution for hydroponics, in which the pH of the culture solution is adjusted by passing a direct current through an insoluble electrode and electrolyzing the culture solution for hydroponics. By supplying oxygen and preventing the generation of “anaerobic denitrifying bacteria” due to lack of oxygen, the consumption decomposition of “nitrogen fertilizer” is suppressed, and further, by sterilizing the culture solution, it fluctuates due to root decay and fermentation. It is an object of the present invention to provide a method for adjusting a culture solution for hydroponics, which can easily, safely and inexpensively adjust the culture solution for stabilizing the pH.

More specifically, when direct current is applied as a culture solution for hydroponics and the electrolysis is performed, the electrode substrate is made of titanium, tantalum, niobium, zirconium metal or an alloy thereof with platinum, iridium, A composite comprising an electrode catalyst made of one or more metals or metal oxides selected from ruthenium and palladium and a dispersion of an electrode catalyst selected from metal oxides of titanium, tin, tantalum, antimony, niobium and zirconium An insoluble anode having an oxide coating layer and an iron, nickel, copper, silver metal or an alloy thereof, a titanium, tantalum, niobium, zirconium metal or an alloy thereof, or the metal or alloy as an electrode substrate, and the electrode From one or more selected from platinum, iridium, ruthenium and palladium as an electrode catalyst for the substrate An insoluble cathode coated with a metal, alloy, or metal oxide as an electrode catalyst, or an electrode catalyst dispersion selected from metal oxides of titanium, tin, tantalum, antimony, niobium, and zirconium. By using an insoluble cathode with a composite oxide coating layer, the pH of the culture solution is adjusted, and oxygen generated from the insoluble anode is supplied to the culture solution, thereby generating anaerobic denitrifying bacteria due to lack of oxygen. By controlling the consumption and decomposition of nitrogen fertilizer by the anaerobic denitrifying bacteria, and further sterilizing the culture solution, it is easy to adjust the culture solution such as root decay and stabilizing the pH that fluctuates due to fermentation. An object of the present invention is to provide a method for preparing a culture solution for hydroponics that is performed safely and inexpensively.

As the anode used in the present invention, an electrode already on the market can be used, but it is essential that the anode be an insoluble anode. Insolubility not only prevents the culture solution from being contaminated with electrode components, but is an indispensable element for controlling the target electrode reaction. Metals such as iron, nickel, stainless steel, copper, and silver cannot be used as the insoluble anode of the present invention because the anode dissolves.

As the insoluble anode, for example, a fired electrode and an electroplated electrode manufactured by Nippon Carlit Co., Ltd. can be used. A clad electrode in which a platinum group metal is clad on the insoluble anode base material can also be used. Furthermore, an electrode having improved corrosion resistance as disclosed in JP-A-2003-293196 and JP-A-2004-204328 can also be used, and is suitable as an insoluble anode used in the present invention.

The cathode used in the present invention is indispensable to be insoluble in the culture solution like the anode. As the cathode material, a corrosion-resistant metal such as iron, nickel, copper, silver, or an alloy such as stainless steel can be used. Further, highly corrosion-resistant metals such as titanium, tantalum, niobium, and zirconium, and alloys thereof are preferable. Furthermore, using these metals as electrode substrates, and using an insoluble cathode coated with one or more metals, alloys or metal oxides selected from platinum, iridium, ruthenium and palladium as electrode catalysts on the electrode substrates, cathodic reaction By suppressing the overvoltage of hydrogen generation, it is possible to reduce the electrolysis voltage and reduce the power consumption, which is suitable as the insoluble cathode of the present invention.

The shape of the anode and cathode of the present invention can be any shape depending on the application because the substrate is a metal. In addition, since it is an insoluble electrode, there is no change in shape due to dissolution or the like. Therefore, the electrode shape may be determined in accordance with the installation location, such as the form of nutrient solution culture, the source of bacterial contamination, and the ease of management. For example, if it is installed in the culture medium passage in a state of a non-diaphragm, it is a comb-like shape in which mesh electrodes and rod-shaped electrodes having an expanded metal substrate that does not obstruct the flow of the culture medium are electrically joined by means such as welding. Electrodes are preferred.

In addition, in the case of farms that carry out hydroponics where the culture solution is intensively managed, any of plate-like, rod-like, or net-like electrodes can be used in the intensive management tank. Furthermore, an electrode in which a mesh electrode is electrically joined to a rod-like electrode by means such as welding, and similarly, an electrode in which a plurality of mesh electrodes are joined is suitable. If it is the electrode of this shape, it can be used also as a strainer other than the objective of this invention.

The electrode can be installed at any place. It may be installed for pH adjustment after fertilizer adjustment. In particular, the inside of the culture solution passage which is in contact with the atmosphere and easily contaminated with bacteria is preferable. Moreover, these may be provided side by side, and a plurality of electrodes may be installed in a distributed manner, and it is desirable to measure and manage the electrical conductivity and pH at each electrode installation location and adjust the amount of energization current.

The culture solution for nutrient solution cultivation adjusted by the electrolysis method of the present invention is a nutrient solution culture solution having nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, carbon, oxygen, hydrogen, iron, manganese, boron as elements. It consists of copper, zinc, molybdenum, chlorine, sodium, silicon, and aluminum, and the form as a compound is composed of nitrate, phosphate, sulfate, ammonium salt, chelate salt, organic fertilizer component aqueous solution, for plant cultivation This is a basic configuration. Therefore, other components may be added to the culture medium having the basic structure depending on the type of plant.

The culture medium for hydroponics is based on well water and tap water, and is basically composed of potassium nitrate, calcium nitrate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, potassium sulfate, magnesium sulfate, and contains EDTA, amino acids, organic acids, etc. A dilute solution of electrolyte with pH adjusted by adding acid and alkali to ligand, iron, manganese, copper, zinc, molybdic acid, chelate salt. Further, as the sulfate or phosphate, a first sulfate, a second phosphate, or a tertiary phosphate is also suitable.

The adjustment of the culture solution for hydroponics by the electrolysis method of the present invention directly electrolyzes the culture solution with an insoluble electrode, without causing deterioration or loss of the culture solution due to the occurrence of precipitation of the components that become fertilizers, The purpose is to maintain and control the pH of the culture solution to an appropriate value and to sterilize the culture solution.

The pH of the culture solution affects the dissolved state and solubility of dissolved ions, which are nutrients in the culture solution, and has a significant effect on growth by directly affecting the absorption balance of plants and the amount of water absorbed by plants. Become. Although the pH of the culture solution is affected by the type of plant, fertilizer concentration, etc., it is recommended from the standpoint of plant growth that it should be controlled within the pH 5.5 to pH 6.5 range, which is suitable for absorbing nutrient water. Has been. However, in the cultivation of bees and leeks, the pH of the culture solution may be controlled in the range of pH 4.5 to pH 5.0 in order to obtain the fertilizer effect of P and Ca.

Further, the pH of the culture solution of solanaceous plants such as tomatoes and peppers, bee, and leeks increases with growth. For example, in tomato growth, the pH of the culture solution is appropriate in the range of pH 5.5 to pH 6.5, but is controlled to a high pH with growth. If the pH of the culture solution is about pH 7.5, there will be no problem in the growth of tomatoes, but if it exceeds pH 8, iron, manganese, phosphorus, etc. will easily precipitate. When grown in the culture solution, deficiency may occur. In particular, the balance of the culture solution becomes large from the beginning of fruit harvesting. In such a case, it is necessary to lower the pH of the culture solution. Therefore, from the above, the pH control range of the culture solution for hydroponics is pH 4.5 to pH 8, preferably pH 5.5 to pH 6.5.

In general, when water electrolysis is performed on a non-transparent membrane through a direct current using an insoluble electrode, water is electrolyzed and oxygen is generated at the anode as an electrolytic oxidation reaction, and hydrogen is generated as an electrolytic reduction reaction at the cathode. As a result, water is decomposed and reduced to oxygen and hydrogen, but the pH of the electrolyte does not change. On the other hand, when an aqueous solution containing chlorine ions is electrolyzed, an alkaline hypochlorous acid aqueous solution is obtained.

However, electrolysis using a culture medium for hydroponics with an insoluble membrane using an insoluble electrode causes the pH to fluctuate to the acidic side and reduce the amount of luminescence from ATP and AMP derived from microbial reactions. That is, it was found that pH adjustment is possible by electrolysis, that a bactericidal effect can be obtained, and that oxygen concentration in the culture solution is increased, and electrolysis is effective for plant cultivation, and an insoluble electrode is used. By direct current electrolysis of the culture solution for hydroponics, the present invention has been achieved in which the culture solution for nutrient culture can be adjusted.

That is, as shown in Example 1, the concentration of the culture solution composed of potassium nitrate, magnesium sulfate, monoammonium phosphate, EDTA-iron, calcium nitrate, ammonium molybdate, trace element sulfate, phosphoric acid, etc. (EC) 0.1S / m, pH6.42 about the electrical conductivity and pH change of the culture solution for tomato hydroponics, using metal titanium as an electrode substrate, the electrode substrate as an electrode catalyst, by electroplating The electrode coated with platinum was used as an insoluble anode and an insoluble cathode and compared with the case of electrolysis.

The culture solution increased in pH as the nutrients were absorbed by the cultivated plants and the electrical conductivity decreased, but the pH of the culture solution without introducing the electrolysis method increased to near pH 7. However, when the electrolysis method was introduced, the pH was controlled to about pH 6.5, and it became clear that the pH of the culture solution can be controlled without adding sulfuric acid or phosphoric acid.

The reason why the pH can be controlled by supplying direct current from the insoluble electrode and directly electrolyzing the culture solution is unknown, but phosphate ions, sulfate ions, organic acids contained in the culture solution are unknown. It is inferred that polyvalent bases and acids such as ions and EDTA ions were expressed as a result of the shift of the equilibrium state of acid-base dissociation by hydrogen ions and hydroxide ions generated at the insoluble anode and insoluble cathode by electrolysis.

As the electrode reaction, phosphate ions, sulfate ions, organic acid ions, EDTA added as fertilizer in the culture solution, ATP produced by biological reaction, organic substances and other polyanions are selectively applied to the anode surface. ATP and AMP amounts derived from microorganisms such as oxygen generation, total organic carbon, and bacteria as an anodic reaction to selectively electrolyze adsorbed and highly concentrated water and adsorbed organic matter and ATP in the culture medium It is presumed that an electrolytic reaction that causes a decrease in the amount of luminescence and a decrease in the number of bacteria due to the decrease in the amount of luminescence occurs.

Therefore, it is considered that the reaction in which chlorine ions having a low concentration are anodized and hypochlorous acid is generated does not actually occur as an electrode reaction even in consideration of the electrode potential, the chlorine ion concentration, and the like. Even if it is considered that an alkaline hypochlorous acid aqueous solution is obtained by generating hypochlorous acid by the diaphragm electrolysis disclosed in Patent Document 2, the pH can be reduced by directly electrolyzing the culture solution with an insoluble electrode. This is clearly different from the results of the present invention, in which an acid liquid is obtained.

That is, there is no detailed description, “Nutrient Cultivation Method and Apparatus” technology described in Patent Document 1 to sterilize by “hypochlorous acid” and “electric field” is a technology that is clearly different from the technology of the present invention. It is clear that there is.

The control of the pH of the culture fluid that fluctuates due to the buffer action presumed to be manifested by the culture fluid electrolysis by the insoluble electrode of the present invention monitors the amount of each culture fluid and the pH variation with respect to the electrical conductivity during electrolysis. By doing so, it becomes controllable by controlling the current value to pH for the purpose of control.

On the other hand, the bactericidal effect is the active nascent oxygen produced by the anodic reaction in the culture solution, the nascent hydrogen produced by oxygen or the cathodic reaction, hydrogen, hydroxy radicals, hydroxyl ions, or direct oxidation of bacteria etc. on the electrode surface, It is assumed that it was expressed by a chemical or electrochemical reaction due to reduction or the like.

As shown in Example 2 and Example 8, it was found that changes in the amount of ATP and AMP derived from microorganisms such as bacteria due to the energization current decreased depending on the energization current amount. The contamination source of the bacteria and the like is considered to be raw water and air for preparing a culture solution. Although it is difficult to completely sterilize these regularly mixed bacteria, etc., as shown in Example 4, the pathogenesis of cultivated plants is prevented by sterilizing the culture solution to such an extent that the plant to be cultured does not become ill. It is possible to do.

Further, the sterilization effect prevents root decay and fermentation, so that the pH change of the culture solution caused by root decay and fermentation is suppressed, and the pH is easily controlled because of stabilization.

Furthermore, the oxygen concentration of the culture solution is usually performed by aeration or the like in which air is blown into the culture solution, but as shown in Example 3, by introducing the electrolytic method of the present invention, It has been found that the amount of dissolved oxygen is maintained almost saturated without using any means. This is presumably because water is electrolyzed at the anode by directly electrolyzing the culture solution, and oxygen in the nascent stage is efficiently dissolved in water, so that a high concentration of oxygen is dissolved in the culture solution.

As a result, it is possible to supply oxygen to the culture without introducing means such as aeration by electrolyzing the culture with an insoluble electrode and generating oxygen at the anode. Generation of anaerobic denitrifying bacteria can be prevented and consumption due to decomposition of nitrogen fertilizer can be prevented.

The amount of current applied to the culture solution must be adjusted depending on the type of plant to be cultivated, the concentration of the culture solution, the hardness of the raw water used, the degree of contamination of the culture solution due to sterilization, the control pH range, seasonal variations, etc. However, it is generally 30 A · h or less per liter of culture solution. The number of equivalents of the component composition contained per liter of the culture solution is about 0.05 equivalents. The energization current amount is one that loads about 1 equivalent of the energization current amount per liter of culture medium. The circulating culture solution is not only easily contaminated by bacteria and the like, but also fertilizer components and the like are accumulated, thereby increasing the buffering action of the culture solution. For this reason, the pH of the culture solution is controlled to an appropriate pH control range, pH 4.5 to pH 8, preferably pH 5.5 to pH 7, and the amount of energization current necessary for sterilization increases. For this reason, when the culture solution is adjusted by electrolysis, it is considered that it is a reasonable value that the amount of current applied per 1 L of the culture solution is 30 A · h or less.

There is no upper limit on the amount of current that can be passed, but if it is 30 A · h or more per liter of culture solution, the amount of fertilizer components and organic matter that accumulate in the culture solution will increase, and bacterial growth will be easier. In combination with electrolyte dialysis technology such as three-chamber method diaphragm electrolysis and ion exchange resin technology, the accumulated fertilizer components and organic substances are desalted to reduce the level of these accumulated fertilizer components, and then pH adjustment and sterilization are performed. This makes it easier and more efficient to adjust the circulating culture medium.

More specifically, in order to perform desalting from a circulating culture solution, as a method of desalting by a two-chamber electrolysis technique, for example, to remove a cation, the culture solution is anoded with a cation exchange membrane interposed therebetween. By flowing through the chamber and energizing from the insoluble anode and the insoluble cathode and performing electrolysis, the cation in the culture solution as the anolyte moves to the cathode chamber, and the cation in the culture solution decreases. At the same time, hydrogen ions are supplied from the anode. Therefore, it is possible to remove cations in the culture solution and lower the pH. On the other hand, in order to remove the anions, the anion in the culture solution is transferred to the anode chamber by flowing the culture solution into the cathode chamber, energizing from the insoluble anode and the insoluble cathode with the anion exchange membrane sandwiched, and electrolysis. As a result, the anion in the culture solution decreases. At the same time, hydroxide ions are supplied from the cathode, so that anions in the culture solution can be removed and the pH can be raised.

In the three-chamber electrolysis technique, an anion exchange membrane is disposed on the cathode chamber side through a cation exchange membrane and an intermediate chamber on the anode chamber side, and a culture solution is circulated in both the anode chamber and the cathode chamber to thereby form an insoluble anode. When a direct current is applied from the insoluble cathode and electrolysis is performed, the cations in the culture fluid in the anode chamber and the anions in the culture fluid in the cathode chamber are transferred to the intermediate chamber, and accumulated salts are removed from the culture fluid. Is done. The electrolytically treated anolyte and catholyte are mixed and reused.

Similarly, a similar effect can be obtained by ion exchange by immersing or passing the circulating culture solution in a cation exchange resin or an anion exchange resin or a mixed ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed. can get. The pH can be raised or lowered by adjusting the mixing ratio of the cation exchange resin and the anion exchange resin. That is, accumulated ions in the culture medium can be removed and pH can be controlled at the same time.

The culture solution processed by the two-chamber electrolysis technique, the three-chamber electrolysis technique, and the ion exchange resin technique is fertilized and pH-adjusted and recycled.

The ion exchange membrane used in the two-chamber electrolysis and the three-chamber electrolysis is a commercially available hydrocarbon resin-based or fluororesin-based cation exchange membrane, an anion exchange membrane, or a cation exchange membrane and an anion exchange membrane bonded together. Bipolar membranes can be used, and as a diaphragm used for two-chamber electrolysis, a hydrocarbon resin-based or fluororesin-based porous film having no ion exchange function or an unglazed diaphragm can be used.

The present invention is a method for preparing a culture solution for hydroponics, in the culture solution for hydroponics without adding acid or alkali for pH adjustment or pesticides to the culture solution, a direct current is passed through the insoluble electrode, By electrolysis, the pH of the culture solution is adjusted to an appropriate pH at each stage of plant growth, and oxygen is supplied to the culture solution to prevent the occurrence of "anaerobic denitrifying bacteria" due to lack of oxygen. By suppressing consumption decomposition of `` nitrogen fertilizer '' by this, furthermore, by sterilizing the culture solution, it is possible to stabilize the pH of fluctuating roots, fluctuating by fermentation, etc. The quality can be cultivated uniformly, the culture medium can be adjusted easily, safely and inexpensively, and the life of the culture medium can be extended and reused in the circulation. View of preventing environmental pollution by reducing fertilizer and wastewater It from is also very effective has been found.

Embodiments of the present invention will be described below. The present invention is not limited to the following examples.

In order to control the pH during the cultivation of the culture medium for tomato hydroponics, in order to examine whether or not it is possible by direct electrolysis of the culture medium with the insoluble electrode of the present invention, Fig. 1 and Fig. 2 show the results of investigating changes in electrical conductivity and pH indicating the fertilizer concentration of the culture solution when the non-diaphragm electrolysis that conducts DC current 20A was not introduced and when it was introduced. Indicated.

For electroless membrane electrolysis, platinum-plated electrode PLATINODE-101B made by Ishifuku Metal Industry Co., Ltd., which is platinum-plated on a titanium expanded metal with a width of 300 mm, a length of 650 mm, and a thickness of 1 mm as the anode, is the same as the cathode. A titanium expanded metal of a size was used. As an electrolytic solution, 10 tons of tomato culture solution having an electric conductivity of 0.1 S / m and a pH of 6.4 was circulated to adjust the pH control range to pH 5.5 to pH 6.5, and electrolysis was performed.

From the results of FIG. 1 and FIG. 2, the pH of the culture solution that was not electrolyzed became pH 6.8, which was outside the control range, but when the culture solution was directly electrolyzed by the insoluble electrode of the present invention, The pH became pH 6.5 or less, and could be in the range of pH 5.5 to pH 6.5 suitable for tomato growth.

Under the same diaphragmless electrolysis conditions as in Example 1, the tomato broth 500L was directly electrolyzed, and the amount of luminescence (RLU) by the reaction of biologically derived adenosine triphosphate (ATP) and luciferase was measured, and the method of the present invention However, it was examined whether it was effective for sterilization of a culture solution. The results are shown in FIG.

From the results shown in FIG. 3, although the amount of luminescence increased at the beginning of electrolysis, it decreased with the electrolysis time, and decreased by about 70% after 120 hours. From the results, it was found that the ATP derived from the organism can be decomposed and the culture solution can be sterilized by the culture solution preparation method of the present invention in which the culture solution is directly electrolyzed by the insoluble electrode.

To a round bar made of titanium with a diameter of 20 mm and a length of 500 mm, an iridium chloride and tantalum chloride hydrochloric acid solution prepared to be an electrode catalyst composed of 60% iridium oxide and 40% tantalum oxide The insoluble anode was manufactured by repeatedly applying to a titanium round bar and thermally decomposing at 550 ° C. Using the SUS electrode of the same shape as the cathode, the anode and the cathode were immersed in the return tank of the NFT hydroponics culture medium for strawberries with a cultivation tank of 50 m, and a 30 A direct current was applied to perform continuous diaphragm electrolysis. Using the treated water subjected to the electrolytic treatment as raw water, after preparing and supplying the fertilizer, the dissolved oxygen concentration in the culture solution at the outlet of the channel is measured, and the culture solution required for culturing by the method for preparing a culture solution by electrolysis of the present invention Whether or not the dissolved oxygen concentration in the medium was ensured was compared with the amount of dissolved oxygen in the culture medium when electrolysis was not performed. The results are shown in FIG.

From the results of FIG. 4, it can be seen that the amount of dissolved oxygen in the culture solution greatly depends on the flow rate of the culture solution when electrolysis is not performed. In particular, when the culture fluid flow rate is 2 L or less per minute, the dissolved oxygen concentration is 4 ppm or less, and the dissolved oxygen amount is insufficient. On the other hand, by introducing the electrolytic method of the present invention, a stable dissolved oxygen concentration at a high concentration is obtained. Obtained, stable high-quality products and high production can be expected.

Exelod C manufactured by Nippon Carlit Co., Ltd. is a calcined electrode in which a complex oxide using ruthenium oxide as an electrode catalyst is applied to a titanium expanded metal having an electrolytic area of 100 mm in length, 100 mm in width and 1 mm in thickness by electrolysis. Exode R-1000 with platinum as the electrode catalyst was used as the anode, and 1 A of direct current of 3 A was applied to the tomato hydroponics culture solution 1 L as the electrolyte to perform direct electrolysis of the diaphragm. The electrolyte solution was collected, and after culturing at 35 ° C. for 48 hours using a Petri film medium for measuring viable cell count manufactured by 3M Healthcare Co., Ltd., the number of colonies was measured, and the colony number dependency on the amount of current applied was examined. The results are shown in FIG.

From the results of FIG. 5, the number of colonies increases at the initial stage of electrolysis, but decreases as the electrolysis progresses, and the amount of energizing current is about 4.5 A / h per 1 L of the culture solution. Reduced to%. That is, about 96% of sterilization was possible.

Whether or not the electrolysis test of the present invention is effective for the purification of the culture solution essential for the circulation and reuse of the culture solution, with respect to the culture solution for tomato hydroponics, under the same conditions as in Example 4. This was investigated by measuring the dependence of total organic carbon (TOC) concentration on the amount of current applied. The results are shown in FIG.

From the results shown in Fig. 6, the culture solution before electrolysis with a TOC value of approximately 460 ppm decreased as the electrolysis progressed, and the TOC value was 100 ppm at a current of 1 Ah per liter of the culture solution, resulting in 2 Ah The amount of electricity supplied was 50 ppm, and the amount of electricity supplied was 4.5 A · h, which was 3 ppm. From the results, it is possible to purify the culture solution by the electrolysis method of the present invention. Therefore, it is possible to prolong the life of the culture solution and to reduce the amount of the culture solution to be preserved for the environment and reduce costs. It has been found.

It is immersed in hot oxalic acid, pickled, washed with water and has an electrolytic area of 100 mm in length, 100 mm in width, and 1 mm in thickness.Titanium expanded metal is used as an electrode substrate, and pyrolysis method, that is, ruthenium oxide and oxidation on the electrode substrate. After applying an electrode catalyst with a mixture ratio of iridium at a molar ratio of 2: 1 and an aqueous hydrochloric acid solution containing an electrode catalyst dispersion with a molar ratio of titanium oxide and tin oxide at a ratio of 2: 1 as a chloride, firing at 550 ° C. The titanium oxide insoluble metal electrode coated with the composite oxide was manufactured, and the insoluble metal electrode was used as an anode, and the insoluble electrode coated with an electrocatalyst made of platinum and ruthenium oxide was used as the cathode. , Asahi Glass Co., Ltd. Selemion AMV is used as an anion exchange membrane between the positive and negative electrodes, 20L of 1L of the culture broth whose electrical conductivity increased to 0.5S / m was used as the circulatory culture broth Was circulated as a catholyte, and a current of 5 A was supplied from a DC power source, and two-chamber ion exchange membrane electrolysis was performed for 2 hours. Thereafter, the catholyte whose pH was increased by two-chamber ion exchange membrane electrolysis was used as the electrolyte, 5 A direct current was applied, 4 hours of non-membrane electrolysis was performed, and the pH of the culture solution was controlled within the pH 5.5 range. The pH was adjusted to 6.5. The results are shown in Table 1.

表1の結果より、二室法イオン交換膜電解及び無隔膜電解の併用方法により、従来廃棄していた電気電導度が上昇した培養液を再生し、再循環に供することが、可能であることが判明した。

From the results shown in Table 1, it is possible to regenerate a culture medium with increased electrical conductivity, which has been conventionally discarded, and use it for recirculation by the combined method of two-chamber ion exchange membrane electrolysis and non-membrane membrane electrolysis. There was found.

As in Example 6, Exelod B manufactured by Nippon Carlit Co., Ltd., having an electrolytic area of 100 mm in length, 100 mm in width, and 1 mm in thickness, coated with titanium expanded metal on the electrode substrate by thermal decomposition using iridium oxide as an electrode catalyst. An insoluble anode, as well as Exelod RN-2000 with platinum and iridium oxide coated on a titanium expanded metal electrode substrate as an electrocatalyst, was used as an insoluble cathode, and as a cation exchange membrane between the positive and negative electrodes, Selemion manufactured by Asahi Glass Co., Ltd. As in Example 6, using CMV and Selemion AMV as the anion exchange membrane, circulating culture fluid whose electrical conductivity was increased to 0.6 S / m was circulated as an anolyte, an intermediate solution and a catholyte. A current of 5A was applied to the battery by a DC power source, and a three-chamber ion exchange membrane electrolysis was performed for 6 hours. Thereafter, the anolyte and the catholyte were mixed, the pH and electrical conductivity of the mixture were measured, and it was examined again whether or not it could be used as the raw water of the culture solution. The results are shown in Table 2.

表2の結果より、三室法イオン交換膜電解により、従来廃棄していた電気電導度が上昇した培養液を再生し、循環して培養液調製用の原水に供することが可能となることが判明した。

From the results in Table 2, it was found that the three-chamber ion exchange membrane electrolysis can regenerate and circulate the conventionally discarded culture solution with increased electrical conductivity and supply it to the raw water for preparing the culture solution. did.

To investigate whether it is possible to reuse tomato broth that has been circulated and reused at a high fertilizer concentration in order to increase the sugar content of the fruit, 20L of the broth whose electrical conductivity has increased to 0.7 S / m In order to determine the possibility of reuse, the electrical conductivity, pH, and light emission amount were measured. For the ion exchange resin treatment, the cation exchange resin Diaion SK110 and the anion exchange resin Diaion SA10A manufactured by Mitsubishi Chemical Corporation were each treated in an acid form and a base form, and then mixed in a volume ratio of 1: 1. The solution was passed through. Next, the plate-shaped Ishifuku Metal Industry Co., Ltd. MODE-200 fired electrode with an electrolytic area of 100 mm in length, 100 mm in width and 3 mm in thickness is used as the insoluble anode, and the copper plate of the same shape is insoluble. Using as a cathode, a 10 A direct current was applied to conduct electroless membrane electrolysis for 10 hours. The results are shown in Table 3.

表3の結果より、イオン交換樹脂処理では、培養液に蓄積した不要成分が除去され、電気電導度は低下したが、pH及び発光量は減少せず、pH調整と殺菌効果は得られなかった。さらに、該イオン交換樹脂処理を行った培養液を無隔膜電解した培養液では、pHがトマト栽培の育成に適するpH5.8とすることが可能となり、発光量も減少した。該イオン交換樹脂処理と無隔膜電解処理を併用した処理により、肥料濃度を高濃度で循環使用した高電気電導度の培養液を再使用するための原水として利用可能であることが判明した。

From the results in Table 3, the ion exchange resin treatment removed unnecessary components accumulated in the culture solution and decreased the electrical conductivity, but the pH and the amount of luminescence did not decrease, and the pH adjustment and bactericidal effect could not be obtained. . Furthermore, in the culture solution obtained by subjecting the culture solution treated with the ion exchange resin to electroless membrane electrolysis, the pH can be adjusted to pH 5.8 suitable for growing tomato cultivation, and the amount of luminescence is also reduced. It has been found that the treatment using both the ion exchange resin treatment and the non-diaphragm electrolysis treatment can be used as raw water for reusing a culture solution having a high electrical conductivity and circulating at a high fertilizer concentration.

Drawing showing changes in electrical conductivity and pH of tomato broth over time Drawing showing electrical conductivity and pH change over time of tomato broth subjected to membraneless electrolysis Drawing showing electrolysis time dependence of tomato broth luminescence Drawing showing the culture flow rate dependence depending on the presence or absence of electrolysis of dissolved oxygen concentration in strawberry culture Drawing showing the dependence of the number of general bacteria in the tomato broth on the amount of applied current Drawing showing the dependence of total organic carbon (TOC) concentration in tomato broth on the amount of applied current

Claims (7)

When the culture medium for nutrient solution culture is directly electrolyzed with a direct current as an electrolyte solution, the electrode substrate is made of titanium, tantalum, niobium, pH adjustment, sterilization, oxygenation, desalting, concentration adjustment of the nutrient solution culture medium. A metal of zirconium or an alloy thereof, and an electrode catalyst made of one or more metals or metal oxides selected from platinum, iridium, ruthenium, and palladium as an electrode catalyst on the electrode substrate, and titanium, tin, tantalum, antimony, niobium An insoluble anode having a composite oxide coating layer containing a dispersion of an electrocatalyst selected from metal oxides of zirconium, iron, nickel, copper, silver metals or alloys thereof, or titanium, tantalum, niobium , Zirconium metal or alloys thereof, or the metal or alloy as an electrode substrate, and platinum as an electrode catalyst on the electrode substrate. Insoluble cathode coated with one or more metals, alloys or metal oxides selected from iridium, ruthenium and palladium as electrode catalyst or selected from metal oxides of titanium, tin, tantalum, antimony, niobium and zirconium A method for preparing a culture solution for hydroponics, which comprises using an insoluble cathode having a composite oxide coating layer containing a dispersed material of an electrode catalyst. The culture medium for hydroponics is composed of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, carbon, oxygen, hydrogen, iron, manganese, boron, copper, zinc, molybdenum, chlorine, sodium, silicon, aluminum nitrate 2. The hydroponic culture according to claim 1, comprising a phosphate, sulfate, ammonium salt, chelate salt, an aqueous solution of an organic fertilizer component, and the pH is adjusted to a range of pH 4.5 and pH 8. How to adjust the culture solution. 3. The method for adjusting a culture solution for hydroponics according to claim 1 or 2, wherein the direct current power source is a solar battery when electrolyzing the culture solution for hydroponics with the direct current power source as an electrolytic solution. When the culture solution for nutrient solution culture is DC electrolyzed as an electrolyte solution and the culture solution for nutrient solution culture is prepared, the electrolysis method is selected from diaphragm electrolysis, diaphragm electrolysis of two-chamber method diaphragm electrolysis or three-chamber method diaphragm electrolysis 4. The method for adjusting a culture solution for hydroponics according to claim 1, 2, or 3, wherein the culture solution for hydroponics is adjusted. A diaphragm in which the diaphragm for electrolysis is selected from a cation exchange membrane, an anion exchange membrane, and a neutral membrane for direct current electrolysis using a culture solution for nutrient solution cultivation as an electrolyte solution and adjusting the culture solution for nutrient solution cultivation. 5. The method for preparing a culture solution for hydroponics according to claim 1, 2, 3, or 4, wherein the method is electrolysis. Direct current electrolysis as a culture solution for hydroponics, and in adjusting the culture solution for hydroponic culture, select from cation exchange resin, anion exchange resin or a mixed resin thereof, and combined treatment with the electrolysis method, 6. The method for adjusting a culture solution for hydroponics according to claim 1, 2, 3, 4, or 5, wherein the culture solution for hydroponics is adjusted. The direct current electrolysis using the culture medium for nutrient solution cultivation as an electrolytic solution, and adjusting the culture solution for nutrient solution culture, the amount of energizing current is 30 Ah or less per 1 L of the nutrient solution, , 3, 4, 5, and 6. The method for preparing a culture solution for hydroponics according to claim 1.

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