JP2015216854A - Cleaning method and cleaning facility of culture medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent diffusion of disease damage by effectively sterilizing disease damage fungus in a culture medium after inhibiting plant growth inhibition, in a cleaning method and cleaning facility which clean the culture medium by electrolyzing the culture medium.SOLUTION: An electrolysis is performed so that the total residual chlorine concentration in a culture medium becomes 1.0 mg-Cl/L or less. Even if the total residual chlorine concentration of the hypochlorous acid produced by electrolysis in the culture medium is a low concentration of 1.0 mg-Cl/L or less, a sufficient sterilization effect is obtained, and thereby sterilization treatment in such a low concentration can inhibit plant growth inhibition.

Description

  TECHNICAL FIELD The present invention relates to a culture liquid purification method and a purification apparatus for suppressing bacteria such as disease-causing bacteria generated in a culture solution and the spread of disease caused thereby in hydroponic culture (including hydroponics) of plants. It is.

  As one of the methods for cultivating plants, there is hydroponics that isolates plants from soil and supplies liquid fertilizer. Hydroponic cultivation can reduce manual labor compared to soil cultivation, and it is easy to control environmental conditions such as fertilizer concentration and temperature in the underground such as roots, so system automation and stable production throughout the year can be achieved. It has the advantage that it is possible, and the installation area of hydroponic cultivation facilities is increasing year by year.

  In hydroponic culture, soil and plants are isolated, so there are no continuous cropping problems or soil-borne diseases. However, in actual hydroponic cultivation, diseases occur and the culture solution is used in a circulating manner. In case, the disease spreads throughout the cultivation tank. When the disease spreads, it is necessary to change the whole amount of the culture solution and sterilize the cultivation tank, which greatly affects the production plan.

  In recent years, due to social backgrounds such as increased food safety and environmental protection, the evaluation of low pesticide-free and pesticide-free cultivation has been increased not only in soil cultivation but also in hydroponic cultivation, and disease prevention technology that does not rely on agricultural chemicals is required. ing. Various methods such as ultraviolet irradiation, ozone injection, filtration, heating, and photocatalyst treatment have been proposed as disease prevention technologies that do not rely on pesticides in hydroponic cultivation. There are cost issues such as replacement frequency. Moreover, with automation of a cultivation system, establishment of the disease prevention technique according to a growth condition and cultivation environment and integration with a cultivation system are desired.

  Patent Document 1 proposes a disease prevention method by electrolysis, and waste products (water-soluble) discharged from pathogenic fungi and crop roots by an electric field and hypochlorous acid generated by electrolysis of a circulating culture solution. It is explained that organic matter) is oxidatively decomposed and sterilized.

  Patent Document 2 proposes a hydroponic cultivation method in which the growth inhibitory substance concentration in the culture solution is reduced by electrolysis of the culture solution, and a nutrient solution component containing an iron chelating agent is replenished as a subsequent step of the electrolysis. It is described that growth inhibitory substances can be reduced by electrolysis, and that by-product hypochlorous acid can control disease-causing bacteria and increase the yield of dissolved oxygen by increasing dissolved oxygen concentration. Has been.

Patent Documents 1 and 2 do not describe the amount of hypochlorous acid produced by electrolysis, but generally, the total residual chlorine concentration at which a bactericidal effect is obtained is several mg-Cl _2. Therefore, even in Patent Documents 1 and 2, hypochlorous acid having a total residual chlorine concentration of several mg-Cl ₂ / L or more is generated in the culture solution by electrolysis. Conceivable.

JP 2002-51651 A Japanese Patent No. 517739

In the hydroponic culture system, the establishment of a planned and efficient production method is required, but among the conventional disease prevention technologies, ultraviolet irradiation, ozone injection, filtration, heating, photocatalytic treatment, etc. are problems in terms of cost On the other hand, since the method of electrolysis is not easy to adjust the electrolysis conditions, the effect is not obtained if the degree of electrolysis is weak, and if the degree of electrolysis is strong or weak, it has an adverse effect on plant growth. And there is a problem of increasing energy consumption.
That is, the hypochlorite can be sterilized by producing hypochlorous acid by electrolysis of the culture solution to suppress the spread of the disease, but the generated hypochlorous acid is contained in the plant being grown and the culture solution. Adversely affects the fertilizer components of plants, and the presence of hypochlorous acid inhibits plant growth.

In this way, hypochlorous acid has a bactericidal effect, but adversely affects the growth of the plant to be cultivated, so it responds to the growth conditions such as plant growth and metabolism, and environmental factors such as light intensity, temperature, and liquid temperature. Although it is necessary to adjust the electrolysis conditions, Patent Document 1 discloses a method for avoiding adverse effects on the growth of plants to be cultivated, an operation method at a low concentration of hypochlorous acid, and an adjustment method for electrolysis conditions. It has not been examined.
Similarly, in Patent Document 2, the adjustment of the electrolysis conditions is limited to the level controlled by the intensity (current value, etc.) and frequency of electrolysis, and the growth situation such as plant growth and metabolism, light quantity and temperature, The electrolysis conditions corresponding to environmental factors such as liquid temperature have not been adjusted.

The concentration of bacteria and other substances to be purified is affected by environmental factors such as plant growth and metabolism, light intensity, air temperature, and liquid temperature. It is necessary to adjust the electrolysis conditions according to the environmental factors.
However, since measurement of bacteria and the like requires a long time for culturing bacteria, adjustment of electrolysis conditions according to these measurements and measurement results is not practical, and alternative means are required.

  The present invention solves the above-mentioned conventional problems, and in a culture liquid purification method and purification apparatus utilizing electrolysis of a culture liquid, it suppresses plant growth inhibition and effectively sterilizes disease-causing bacteria in the culture liquid. The method and device for purifying the culture solution to prevent the spread of disease or the growth conditions such as plant growth and metabolism, the environmental conditions such as light quantity, air temperature, liquid temperature, etc. It is an object of the present invention to provide a culture medium purification method and purification apparatus that can be adjusted, and a culture medium purification method and purification apparatus that can reduce the amount of electric power required for electrolysis.

As a result of intensive studies to solve the above problems, the present inventors have found that hypochlorous acid in the culture solution produced by electrolysis is a low concentration of 1.0 mg-Cl ₂ / L or less as a total residual chlorine concentration. Even so, a sufficient bactericidal effect can be obtained. Therefore, under such low concentration conditions, plant growth inhibition can be suppressed, and the total residual chlorine concentration in the culture solution after electrolysis can be measured. Control of electrolysis conditions based on it, removal of total residual chlorine in the culture broth after electrolysis, measurement of total residual chlorine concentration in culture broth circulated in the cultivation tank, control of electrolysis conditions based on it, and electrolysis By constructing a control system for measuring the chloride ion concentration of the culture solution and adding an electrolyte based on it, it is possible to efficiently purify the culture solution by electrolysis while suppressing plant growth inhibition. so In addition, the electrolysis conditions can be adjusted accurately and the amount of power required for electrolysis can be reduced in response to environmental factors such as plant growth and metabolism, light intensity, air temperature, and liquid temperature. I have found that it can also be possible.

  The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] In a method for purifying the culture solution by generating hypochlorous acid by electrolyzing the culture solution, the total residual chlorine concentration of the culture solution is 1.0 mg-Cl ₂ / L or less. A method for purifying a culture solution, comprising performing electrolysis.

[2] A method for purifying a culture solution according to [1], wherein the total residual chlorine concentration of the culture solution after electrolysis is measured, and the electrolysis conditions are adjusted based on the measurement result.

[3] In [1] or [2], a method for purifying a culture solution after extracting and electrolyzing the culture solution in the cultivation tank, and returning the culture solution to the cultivation tank, A method for purifying a culture solution, comprising removing residual chlorine and then returning it to the cultivation tank.

[4] A method for purifying a culture solution according to [3], wherein the total residual chlorine concentration of the culture solution after removing the residual chlorine is measured, and electrolysis conditions are adjusted based on the measurement result.

[5] In any one of [1] to [4], the chloride ion concentration of the culture solution to be subjected to electrolysis is measured, and based on the measurement result, the chloride ion concentration of the culture solution is not more than a predetermined value. In this case, a method for purifying a culture solution, comprising adjusting an chloride ion concentration by adding an electrolyte containing chloride ions to the culture solution.

[6] In a method for purifying the culture solution by generating hypochlorous acid by electrolyzing the culture solution, the total residual chlorine concentration of the culture solution after the electrolysis is measured, and based on the measurement result, A method for purifying a culture solution, comprising adjusting the decomposition conditions.

[7] In a method for purifying a culture solution that is extracted from a culture tank and electrolyzed and then returned to the culture tank, after removing residual chlorine in the culture solution after the electrolysis, A method for purifying the culture broth, which is returned.

[8] The method for purifying a culture solution according to [7], wherein the total residual chlorine concentration of the culture solution after removing the residual chlorine is measured, and the electrolysis conditions are adjusted based on the measurement result.

[9] In a method for purifying the culture solution by generating hypochlorous acid by electrolyzing the culture solution, the chloride ion concentration of the culture solution to be subjected to electrolysis is measured, and based on the measurement result, A method for purifying a culture solution, comprising adjusting an chloride ion concentration by adding an electrolyte containing chloride ions to the culture solution when the chloride ion concentration of the culture solution is a predetermined value or less.

[10] In a culture solution purification apparatus comprising an electrolysis device that generates hypochlorous acid by purifying the culture solution by extracting and electrolyzing the culture solution in the cultivation tank, and then returning the culture solution to the cultivation tank. Total residual chlorine concentration measuring means for measuring the total residual chlorine concentration of the culture broth after the electrolysis, and control means for adjusting the electrolysis conditions of the electrolysis apparatus based on the measurement value of the total residual chlorine concentration measuring means A culture medium purification apparatus comprising:

[11] The culture according to [10], wherein the electrolysis conditions are controlled by the control means so that the measured value by the total residual chlorine concentration measuring means is 1.0 mg-Cl ₂ / L or less. Liquid purification device.

[12] In a culture solution purification apparatus comprising an electrolysis device that generates hypochlorous acid by purifying the culture solution by extracting and electrolyzing the culture solution in the cultivation tank, and then returning the culture solution to the cultivation tank. A residual chlorine removing means for removing residual chlorine in the culture solution purified by the electrolyzer, and the culture solution after the residual chlorine is removed by the residual chlorine removing means is returned to the cultivation tank; An apparatus for purifying a culture solution.

[13] In [12], based on the total residual chlorine concentration measuring means for measuring the total residual chlorine concentration of the culture solution from which the residual chlorine has been removed by the residual chlorine removing means, and the measurement value of the total residual chlorine concentration measuring means And a control means for adjusting electrolysis conditions of the electrolyzer.

[14] In a culture solution purification apparatus comprising an electrolyzer that generates hypochlorous acid by purifying the culture solution by extracting and electrolyzing the culture solution in the cultivation tank and then returning the culture solution to the cultivation tank. Based on the measured value of the chloride ion concentration measuring means for measuring the chloride ion concentration of the culture broth and the chloride ion concentration measuring means, when the chloride ion concentration of the culture broth is a predetermined value or less, An apparatus for purifying culture broth, comprising: chloride ion concentration adjusting means for adjusting chloride ion concentration by adding an electrolyte containing chloride ions to the culture broth.

According to the present invention, hypochlorous acid is generated by electrolysis to effectively sterilize and purify disease-causing bacteria in the culture solution, thereby preventing the spread of disease. Moreover, since the amount of hypochlorous acid generated at that time is a low concentration of 1.0 mg-Cl ₂ / L or less in the total residual chlorine, plant growth inhibition by hypochlorous acid can be suppressed ( Claims 1 and 11).

  In order to generate such a low concentration of hypochlorous acid, it is preferable to measure the total residual chlorine concentration of the culture broth after the electrolysis and to adjust the electrolysis conditions based on the measurement result (claim 2). , 6, 10).

  Further, by removing residual chlorine in the culture solution after purification by electrolysis, it is possible to reliably prevent plant growth inhibition by hypochlorous acid (claims 3, 7, and 12). At this time, by measuring the total residual chlorine concentration of the culture broth after residual chlorine removal and adjusting the electrolysis conditions based on this measurement result, the amount of electric power required for electrolysis and the load of the residual chlorine removal means are reduced. It can be made small and efficient purification can be performed (claims 4, 8, and 13).

  Also, measure the chloride ion concentration in the culture solution to be subjected to electrolysis. If the chloride ion concentration in the culture solution is insufficient based on this measurement result, add an electrolyte containing chloride ions. By adjusting the chloride ion concentration, the amount of power required for electrolysis can be reduced and efficient purification can be performed (claims 5, 9, and 14).

By applying the purification technology of the present invention to the purification of the culture solution, energy consumption and expenses related to consumable materials can be reduced compared to the conventional technology. By substituting the total residual chlorine concentration for contamination caused by bacteria, disease bacteria, waste products, growth-inhibiting substances, algae, etc., it is possible to automate the management and purification system of the culture solution.
In the present invention, it does not require complicated instruments and complicated operations necessary for measuring the concentration of bacteria in a culture solution and a long measurement time, and it remains in grasping the state of contamination of bacteria into the culture solution. Although a chlorine concentration measuring device is used and a chloride ion concentration measuring device is used for evaluating the electrolysis suitability of the culture solution, these are general-purpose meters and are easy to put into practical use. In addition, immediate measurement is possible by using these instruments. In addition, by automatically adjusting the electrolysis conditions based on the measurement results of the total residual chlorine concentration measuring device installed at the outlet of the residual chlorine removal device and the residual chlorine concentration measuring device installed in the electrolytic cell, the plant with hypochlorous acid Purification can be performed effectively while avoiding adverse effects on the growth of the plant. By combining these instantaneous measurement and automatic adjustment functions, the purification system can be easily automated and integrated with the cultivation system.

It is a systematic diagram which shows embodiment of the culture solution purification apparatus of this invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  In the present invention, the total residual chlorine is a combination of free residual chlorine and combined residual chlorine, and the total residual chlorine concentration means the sum of the free residual chlorine concentration and the combined residual chlorine concentration.

  FIG. 1 is a system diagram showing an example of an embodiment of a culture solution purification apparatus of the present invention.

  In FIG. 1, 1 is a cultivation tank and the cultivation of the plant 20 by a culture solution is performed. The culture solution in the cultivation tank 1 is extracted from the pipe 11, a part is introduced from the pipe 11A to the electrolytic tank 2, and the remaining part is introduced from the pipe 11B to the adjustment tank 3. 11a and 11b are open / close valves. In this Embodiment, the electrolytic cell 2 and the adjustment tank 3 are provided in the one septic tank 4 divided by the partition wall 4A.

  The electrolytic cell 2 is provided with a DC power source 5 and electrodes 5A and 5B, a chloride ion concentration measuring device 7 and a total residual chlorine concentration measuring device 8. The culture solution introduced into the electrolytic cell 2 is electrolyzed between the positive and negative electrodes 5A and 5B.

  In the present invention, as a purification method that requires less energy consumption and less frequent replacement of consumables, and that is easy to automate and maintain, electrolysis is employed in which a DC voltage is applied and no diaphragm is provided in the electrolytic cell. The purification mechanism by electrolysis of the culture solution is as follows.

  When the culture solution is electrolyzed, oxygen gas and chlorine gas are generated at the anode and hydrogen gas is generated at the cathode. The pH of the culture solution is usually in the range of 5 to 8, and the generated chlorine gas exists as free residual chlorine (hypochlorous acid and hypochlorite ions). These free residual chlorines are widely used for tap water disinfection and oxidation treatment of organic substances, and bacteria and the like are sterilized when free residual chlorine generated by electrolysis comes into contact with the culture solution.

  In addition, in the neutral range such as the pH range of the culture solution, the bacterial cell surface is often negatively charged due to dissociation of carboxyl groups and phosphate groups, but in the electrolysis of the culture solution, Since chlorine gas is generated at the anode, it is presumed that bacteria and the like are attracted to the anode by electrostatic attraction, thereby promoting contact with free residual chlorine and efficient purification.

  In addition, according to the electrolysis of the culture solution, not only the diffusion of the disease due to the sterilization of the disease bacteria, but also the oxidative decomposition of the waste as described in Patent Document 1, and the growth as described in Patent Document 2. Inhibitors are also reduced. Moreover, generation | occurrence | production of algae is also suppressed and the proliferation of the algae to the urethane mat used by hydroponics, and the spreading | diffusion of a disease by it are also suppressed.

The electrolysis in the electrolytic cell 2 may be performed continuously or intermittently. There is no particular limitation on the time and the frequency of electrolysis once when performing intermittently, but for example, electrolysis is performed for about 5 to 120 minutes per time at a frequency of 1 to 20 times a day. be able to.
In addition, although hydroxide may be generated and attached on the cathode surface with electrolysis, precipitation of hydroxide can be avoided by periodically inverting the polarity of the electrode.

  In the apparatus of FIG. 1, the chloride ion concentration measuring device 7 measures the chloride ion concentration of the culture solution, and an electrolyte aqueous solution containing chloride ions is supplied from the pipe 14 as needed based on the measured value. 2 is added. That is, a predetermined amount of the aqueous electrolyte solution is added as necessary by the flow rate adjusting valve 14A linked to the chloride ion concentration measuring device 7, and when unnecessary, the valve 14 is closed and the addition of the aqueous electrolyte solution is stopped. Is done.

The culture solution contains a small amount of chloride ions derived from the water used for the preparation of the culture solution, but the chloride ion concentration in the culture solution changes with the circulation of the culture solution. The voltage required to generate hypochlorous acid from chloride ions by electrolysis is affected by the chloride ion concentration. When the chloride ion concentration decreases, it is necessary to obtain hypochlorous acid at the specified concentration. Voltage rises.
When high voltage is applied to generate hypochlorous acid necessary for sterilizing bacteria in the culture solution, the running cost increases, so if the chloride ion concentration in the culture solution is low, the electrolyte contains chloride ions. It is preferable to add a small amount of to reduce the amount of power required for electrolysis.

  Any electrolyte that does not adversely affect the growth of the plant may be used, and potassium chloride, ammonium chloride, calcium chloride, magnesium chloride, sodium chloride, and the like can be applied.

  The electrolytic mass to be added depends on the culture solution and the quality of the water used for the preparation of the culture solution, but a voltage drop of about 10% is observed even when the chloride ion concentration is equivalent to 30 mg / L. Usually, when the chloride ion concentration of the culture solution to be subjected to electrolysis is less than 10 mg / L, an electrolyte containing chloride ions is added so that the chloride ion concentration of the culture solution is 30 mg / L or more. It is preferable that The upper limit of the chloride ion concentration of the culture solution to be subjected to electrolysis is generally 200 mg / L or less, although it depends on the plant to be cultivated.

  As in the apparatus shown in FIG. 1, it is possible to measure the chloride ion concentration of a culture solution to be subjected to electrolysis and to immediately and automatically inject an electrolyte containing chloride ions based on the measurement result. By being configured so as to be able to perform efficient purification by reducing the amount of power required for electrolysis of the culture solution.

Moreover, the electrolysis conditions in the electrolytic cell 2 are performed so that the total residual chlorine concentration of the culture solution after the electrolysis measured by the total residual chlorine concentration measuring device 8 is 1.0 mg-Cl ₂ / L or less.
That is, the measured value of the total residual chlorine concentration measuring device 8 is input to the control device 10, and a control signal is output from the control device 10 to the DC power source 5 based on this result. This control signal is, for example, a current value control signal when electrolysis is performed continuously, and an electrolysis time and / or electrolysis frequency per time (when electrolysis is performed intermittently). The number of times of electrolysis within a predetermined time is output as a control signal. In the present embodiment, a measurement value of a total residual chlorine concentration measuring device 9 to be described later is also input to the control device 10, and the control device 10 makes a total residual chlorine concentration measuring device 8 and a total residual chlorine concentration measuring device 9. The electrolysis conditions are controlled based on both measured values.

The greater the amount of hypochlorous acid produced in the culture solution by electrolysis, the better the purification effect. However, if the total residual chlorine concentration exceeds 1.0 mg-Cl ₂ / L, there is a problem of plant growth inhibition, which is preferable. Absent. In this Embodiment, since the residual chlorine removal apparatus 6 for removing a residual chlorine from the culture solution returned to the cultivation tank 1 after electrolysis is provided, the total residual chlorine concentration in the electrolytic cell 2 is 1 Even if it exceeds 0.0 mg-Cl ₂ / L, there is no problem of plant growth inhibition. However, if the total residual chlorine concentration is excessively high, the load of the residual chlorine removing device 6 is increased and the electric energy for electrolysis is increased. Therefore, the total residual chlorine concentration is preferably 1.0 mg-Cl ₂ / L or less, more preferably 0.5 mg-Cl ₂ / L or less, and particularly preferably 0.1 mg-Cl ₂ / L or less.

That is, the present invention is sufficient in the culture solution even if the amount of hypochlorous acid produced by electrolysis is less than several mg-Cl ₂ / L, which is the total residual chlorine concentration required for conventional general sterilization. In this way, the total residual chlorine concentration after electrolysis is suppressed to a low level, thereby preventing plant growth inhibition and preventing electrolysis. The required amount of power can be reduced. The total residual chlorine concentration of the culture solution after electrolysis may be higher than the level at which total residual chlorine is detected. Since the detection limit value of a general free residual chlorine concentration measuring device usually used for detecting the total residual chlorine concentration is usually 0.01 mg-Cl ₂ / L, the lower limit of the total residual chlorine concentration is 0.01 mg-Cl. ₂ / L or more. However, the purification effect may be observed even when the total residual chlorine concentration is less than 0.01 mg-Cl ₂ / L.

  As the total residual chlorine concentration measuring device 8 and the total residual chlorine concentration measuring device 9 described later, a free residual chlorine concentration measuring device can be used. That is, most of the residual chlorine in the culture broth after electrolysis is present in the form of free residual chlorine, and it is considered that there is almost no residual residual chlorine. It can be the total residual chlorine concentration.

  The culture solution after electrolysis flows into the adjustment tank 3 beyond the upper edge of the partition wall 4A of the septic tank 4, and is supplied with water, air, fertilizer, etc. from the pipe 15 together with the culture liquid from the pipe 11B. Adjusted. In other words, the concentration of heavy metals in the culture solution and the amount of dissolved oxygen are insufficient with the circulation use, or the amount of the culture solution itself is insufficient, so it is not necessary to add fertilizer and air and return it to the cultivation tank 1 To avoid excessive sediment formation, plant fertilizer deficiency and dissolved oxygen deficiency. In addition, the amount of the culture solution can be maintained by supplying water.

  The culture solution whose components have been adjusted in the adjustment tank 3 is supplied to the residual chlorine removing device 6 through the pipe 12 by the pump P. After the residual chlorine is removed by the residual chlorine removing apparatus 6, the cultivation tank is supplied from the pipe 13. Returned to 1.

  As a method for removing residual chlorine, there are various methods such as heating, light irradiation, addition of a reducing agent, adsorption of activated carbon, and the like, which is selected according to the cultivation environment. Taking into account the amount of energy used, the frequency of replacement of consumables, the required space, etc., activated carbon adsorption is appropriate.

The culture liquid return pipe 13 is provided with a total residual chlorine concentration measuring device 9, and the measurement value of the total residual chlorine concentration measuring device 9 is input to the control device 10, and the electrolysis conditions are based on this measurement value. Is controlled.
That is, if the total residual chlorine concentration in the culture solution after removing residual chlorine is excessively high, there is a problem of plant growth inhibition in the cultivation tank 1, and in this case, electrolysis conditions are lowered (current value, electrolysis time). , Lower the electrolysis interval).
Further, when the measured value of the total residual chlorine concentration measuring device 9 increases rapidly, the adsorption capacity of the activated carbon is broken when the residual chlorine removing device 6 fails or when the residual chlorine removing device 6 is an activated carbon adsorption tower. In this case, maintenance of the residual chlorine removing device 6 is performed.

After the residual chlorine is removed by the residual chlorine removing device 6, the total residual chlorine concentration of the culture solution returned to the cultivation tank 1 is 0.1 mg-Cl ₂ / L or less, preferably in order to prevent plant growth inhibition Should not be detected.

The purification device shown in FIG. 1 is an example of an embodiment of the present invention, and the present invention is not limited to the device of FIG. 1 as long as the gist thereof is not exceeded.
In the apparatus of FIG. 1, a part of the culture solution extracted from the cultivation tank 1 is fed to the electrolysis tank 2 for electrolysis, but the entire amount is fed to the electrolysis tank 2 for electricity. Decomposition may be performed. Moreover, the culture solution for electrolysis and the culture solution for adjusting the components by adding water, air, fertilizer, etc. are separated, that is, the electrolytic cell and the adjustment vessel are provided separately, and are extracted from the cultivation vessel 1. A part of the culture solution may be electrolyzed in an electrolytic tank, the remaining part may be adjusted in the adjustment tank, and these may be merged and returned to the cultivation tank 1.
Further, the installation location of the total residual chlorine concentration measuring device 8 and the chloride ion concentration measuring device 7 is not limited to the electrolytic cell 2 but may be a culture fluid transfer pipe.

  Hereinafter, the present invention will be described in more detail with reference to test examples in place of the examples.

[Test Example 1]
9 L of a lettuce culture solution was prepared using groundwater as water. The chloride ion concentration in the culture solution was 20 mg / L, and the chloride ion concentration after addition of a predetermined amount of potassium chloride was 52 mg / L. In addition, when the culture solution was subjected to constant current electrolysis under the electrolysis conditions described later, the voltage was about 9 volts before the addition of potassium chloride and about 8 volts after the addition of potassium chloride.

The culture solution after the addition of potassium chloride was received in a bucket, floated with polystyrene foam, and three lettuce seeded on urethane cubes were planted to prepare three culture tanks, which were tested as the following test sections.
Control group: Test group that continued to supply air after lettuce planting Weak electrolysis group: Electrode (platinum-plated titanium electrode, surface area of about 20 cm ² ) installed at the bottom of the bucket
And after supplying lettuce planting, with a constant current value (0.2A),
Test area where electrolysis was conducted intermittently under the following conditions
Electrolysis time per time: 6 minutes
Electrolysis frequency: 6 times a day (electrolysis interval is constant)
Strong electrolytic zone: An electrode (platinum-plated titanium electrode, surface area about 20 cm ² ) is installed at the bottom of the bucket
And after supplying lettuce planting, with a constant current value (0.2A),
Test area where electrolysis was conducted intermittently under the following conditions
Electrolysis time per time: 30 minutes
Electrolysis frequency: 3 times a day (electrolysis interval is constant)
Note that the voltage during electrolysis was stable at about 8 volts in both the weak electrolysis zone and the strong electrolysis zone.

  Cultivation was carried out for 18 days in a plastic house from June 26 to July 13 in the three test zones. After the cultivation, the following bacterial test was performed on the culture solution. Moreover, about lettuce, the above-ground part weight and the underground part weight were measured, and the average value of 4 each was calculated | required. The results are shown in Tables 1 and 2.

<Bacteria test>
Number of general bacteria: The number of colonies after culturing at 36 ° C. for 24 hours on a standard agar medium was determined.
E. coli group number: The number of colonies after culturing at 36 ° C. for 24 hours on a desoxycholate agar medium was determined.

  For weak electrolysis and strong electrolysis, the concentration of free residual chlorine in the culture immediately after the end of one electrolysis (after electrolysis for 6 minutes in the weak electrolysis area and after 30 minutes electrolysis in the strong electrolysis area) Was measured using a portable residual chlorine meter (RC-31P-F manufactured by Toa DKK Corporation, free residual chlorine resolution 0.01 mg / L), and the results are also shown in Table 1. In this test example, the free residual chlorine concentration was measured, but most of the residual chlorine in the culture broth after electrolysis is considered to be in the form of free residual chlorine. Can be considered.

<Consideration of Bacteria Test Results>
Comparing the control zone and the electrolysis zone (weak electrolysis zone and strong electrolysis zone) in Table 1, it was confirmed that both the number of general bacteria and the number of coliforms could be suppressed by electrolysis. Comparing the weak electrolytic zone and the strong electrolytic zone, it was confirmed that the action of suppressing bacterial diffusion was large in the strong electrolytic zone having a long total electrolysis time.
In addition, from the measurement results of free residual chlorine concentration in the culture solution, although the effect of electrolysis is recognized under the electrolysis conditions in the weak electrolysis zone, it is insufficient for suppressing bacterial diffusion, and the level of free residual chlorine can be detected. It can be seen that electrolysis under the above conditions is effective in suppressing bacterial diffusion.

<Consideration of growth survey results>
When comparing the control zone and the electrolysis zone (weak electrolysis zone and strong electrolysis zone) in Table 2, the growth inhibitory action was confirmed in the electrolysis zone, growth inhibition of 14 to 16% in the weak electrolysis zone, and 21 to 34 in the strong electrolysis zone. % Growth inhibition. In particular, the suppression of the underground weight in the strong electrolysis zone was large, and brown discoloration was observed in the roots. In the weak electrolytic zone, no brown discoloration was observed in the roots.

  Since this test example is a test condition in which electrolysis and cultivation are performed simultaneously in a cultivation tank, hypochlorous acid generated by electrolysis acts on bacteria in the culture solution, but also directly on the roots of plants. It is in a working environment. In actual cultivation, by performing electrolysis in a tank different from the cultivation tank, the influence on the roots of the plant can be prevented, and a device for removing residual chlorine before supplying to the cultivation tank is provided. Thus, it is considered that such growth inhibition can be prevented.

The electrolysis conditions (time and frequency) are preferably set based on the growing conditions and cultivation environment, but automatic operation is possible by automatically controlling the current value and electrolysis time so that a very small amount of total residual chlorine concentration is always detected. It becomes possible.
In addition, it is preferable to design the total residual chlorine concentration and contact time according to the nature and amount of the disease-causing bacteria to be sterilized, but from this test result, the total residual chlorine (free residual chlorine) concentration is 0.02 mg-Cl. _{Since the} number of bacteria is significantly reduced even at ₂ / L, only a very small amount of hypochlorous acid having a total residual chlorine concentration of 0.02 mg-Cl ₂ / L or less is generated by electrolysis. However, the spread of disease-causing bacteria can be suppressed, and when the residual chlorine removal device is provided by keeping the total residual chlorine concentration in this way, the load can be reduced. I understand.

After the above 18-day cultivation test, the culture solution water quality of each test section was compared, but no significant concentration difference was observed in heavy metal components such as iron, calcium, magnesium, and manganese.
Moreover, in the culture solution after the cultivation test, green algae was observed on the entire surface of the bottom of the cultivation tank in the control plot, but in each electrolytic zone, the amount of green algae observed on a part of the bottom of the cultivation tank was small, The effect was particularly remarkable in the strong electrolytic zone. When the culture solution was stirred and turbidity was measured, the influence of electrolysis was found to be 16.5 degrees in the control group and 7.1 degrees in the strong electrolysis section. From this result, since the generation of green algae can be suppressed by electrolysis, the electrolysis of the culture solution not only suppresses the spread of diseases, but also prevents contamination of cultivation facilities by green algae and diseases caused by infestation with green algae, etc. It was also confirmed that it is effective.

DESCRIPTION OF SYMBOLS 1 Cultivation tank 2 Electrolysis tank 3 Adjustment tank 4 Septic tank 5 DC power supply 6 Residual chlorine removal device 7 Chloride ion concentration measuring device 8,9 Total residual chlorine concentration measuring device 10 Control device 20 Plant

Claims (14)

In the method for purifying the culture solution by generating hypochlorous acid by electrolyzing the culture solution, the electrolysis is performed so that the total residual chlorine concentration of the culture solution is 1.0 mg-Cl ₂ / L or less. A method for purifying a culture solution, comprising:   2. The method for purifying a culture solution according to claim 1, wherein the total residual chlorine concentration of the culture solution after electrolysis is measured, and electrolysis conditions are adjusted based on the measurement result.   3. The method for purifying a culture solution according to claim 1 or 2, wherein the culture solution in the cultivation tank is extracted and electrolyzed, and then returned to the cultivation tank, and residual chlorine in the culture solution after the electrolysis is removed. Then, it returns to this cultivation tank, The purification method of the culture solution characterized by the above-mentioned.   4. The method for purifying a culture solution according to claim 3, wherein the total residual chlorine concentration of the culture solution after removing the residual chlorine is measured, and the electrolysis conditions are adjusted based on the measurement result.   In any one of Claims 1 thru | or 4, when the chloride ion concentration of the culture solution used for electrolysis is measured, and based on the measurement result, the chloride ion concentration of the culture solution is below a predetermined value, A method for purifying a culture solution, comprising adjusting the chloride ion concentration by adding an electrolyte containing chloride ions to the culture solution.   In the method of purifying the culture solution by generating hypochlorous acid by electrolyzing the culture solution, the total residual chlorine concentration of the culture solution after the electrolysis is measured, and the electrolysis conditions are determined based on the measurement result. A method for purifying a culture solution, comprising adjusting.   In the method for purifying the culture solution, which is extracted from the culture solution in the cultivation tank and electrolyzed and then returned to the cultivation tank, the residual chlorine in the culture solution after the electrolysis is removed, and then returned to the cultivation tank. A method for purifying a culture broth characterized by the above.   8. The method for purifying a culture solution according to claim 7, wherein the total residual chlorine concentration of the culture solution after the residual chlorine is removed is measured, and electrolysis conditions are adjusted based on the measurement result.   In a method for purifying the culture solution by generating hypochlorous acid by electrolyzing the culture solution, the chloride ion concentration of the culture solution to be subjected to electrolysis is measured, and based on the measurement result, the culture solution A method for purifying a culture solution, comprising adjusting the chloride ion concentration by adding an electrolyte containing chloride ions to the culture solution when the chloride ion concentration is less than a predetermined value.   In an apparatus for purifying a culture solution, comprising an electrolyzer for generating hypochlorous acid by purifying the culture solution by extracting and electrolyzing the culture solution in the cultivation tank and then returning the culture solution to the cultivation tank Total residual chlorine concentration measuring means for measuring the total residual chlorine concentration of the culture broth later, and control means for adjusting the electrolysis conditions of the electrolysis apparatus based on the measurement value of the total residual chlorine concentration measuring means An apparatus for purifying a culture solution. 11. The culture solution purification according to claim 10, wherein the electrolysis conditions are controlled by the control means so that the measured value by the total residual chlorine concentration measuring means is 1.0 mg-Cl ₂ / L or less. apparatus.   In an apparatus for purifying a culture solution, comprising an electrolyzer for generating hypochlorous acid by purifying the culture solution by extracting and electrolyzing the culture solution in the cultivation tank and then returning the culture solution to the cultivation tank It has a residual chlorine removing means for removing residual chlorine in the culture liquid purified by the apparatus, and the culture liquid after residual chlorine is removed by the residual chlorine removing means is returned to the cultivation tank. Purifying device for culture medium.   The total residual chlorine concentration measuring means for measuring the total residual chlorine concentration of the culture solution from which residual chlorine has been removed by the residual chlorine removing means according to claim 12, and based on the measurement value of the total residual chlorine concentration measuring means, A culture medium purification apparatus comprising: control means for adjusting electrolysis conditions of the electrolysis apparatus.   In a culture solution purification apparatus comprising an electrolysis device for extracting hypochlorous acid by extracting and electrolyzing the culture solution in a cultivation tank to purify the culture solution and then returning it to the cultivation tank, the culture solution A chloride ion concentration measuring means for measuring the chloride ion concentration of the culture medium, and when the chloride ion concentration of the culture broth is below a predetermined value based on the measured value of the chloride ion concentration measuring means, the culture broth And a chloride ion concentration adjusting means for adjusting the chloride ion concentration by adding an electrolyte containing chloride ions to the culture medium purifying device.

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