JP2001017980A - Method for sterilizing microorganism and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sterilize microorganisms in a liq. with high efficiency without using chemicals, or the like, by allowing the liq. to be treated to flow between electrodes in parallel with the electrodes, impressing a high-voltage pulse of the same polarity between the electrodes, moving the microorganisms in the liq. by electrophoresis and dielectric migration, collecting the microorganisms at the throttled part of an electric field and sterilizing the microorganisms. SOLUTION: A high-voltage pulse of straight polarity or the pulse superimposed with the DC voltage is impressed between an anode 1 and a cathode 2, and a liq. to be treated is introduced into an electrode gap 7 from a passage 13 and treated while discharging the treated liq. from a passage 15. At this time, since an electric field is formed between the anode 1 and cathode 2, microorganisms are moved toward the electrode by electrophoresis. In this case, as a throttled part of the electric field at the openings 5a and 6a of insulating sheets 5 and 6 is formed, the fine grains in water are moved toward the throttled part. Further, on the inside of the throttled part, innumerable throttled parts are also formed in porous insulating sheets 3 and 4, the microorganisms are collected by the throttled parts, held and sterilized by the repeated impression of the voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for disinfecting microorganisms present in a liquid by a high voltage pulse.

[0002]

2. Description of the Related Art Water is widely used as a refrigerant in boilers, heat exchangers, cooling towers, and the like.
This causes a decrease in cooling efficiency. Even in pure water, ultrapure water, etc., the presence of microorganisms causes a decrease in water quality.
In addition, when microorganisms propagate in the water used in the production process, the quality of the product may be degraded or the target product may not be produced.

In order to prevent the growth of microorganisms in water,
Although disinfection methods using disinfectants have become widespread, the safety of chemicals used for disinfection poses a problem. Further, the sterilization method using heat has no problem such as persistence, but has a drawback that the piping material needs to be heat-resistant, and the line must be stopped during sterilization. Further, the method of separating water and bacteria by membrane filtration requires periodic cleaning and replacement because the membrane causes blockage.

In addition, there has been proposed a method of destroying the cell membrane of microorganisms by high-voltage pulses for sterilization. The sterilization can be performed without chemical injection, but the sterilization efficiency is low and it is not in the stage of practical use. In such a method, in order to enhance the sterilization effect using a high-voltage pulse, an insulating partition having micropores through which the liquid to be treated passes is disposed between the electrodes (for example, Japanese Utility Model Publication No. 4-38833), A method of flowing a processing liquid at a high pressure (for example, Japanese Patent Application Laid-Open No. 2-245290) has been proposed. However, it has been difficult to significantly increase the bactericidal effect also by this method.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for disinfecting microorganisms in a liquid capable of disinfecting microorganisms in a liquid with high efficiency by using a simple apparatus and operation without using chemicals and the like. It is to provide a device.

[0006]

SUMMARY OF THE INVENTION The present invention relates to the following method and apparatus for killing microorganisms in a liquid. (1) An electric field diaphragm is formed between opposing electrodes, a liquid to be treated is caused to flow between the electrodes in a direction parallel to the electrodes, a high-voltage pulse of the same polarity is applied between the electrodes, and electrophoresis and dielectrophoresis are performed. A method for disinfecting microorganisms in a liquid, comprising moving microorganisms in a liquid, capturing the microorganisms in a narrow portion of an electric field, and sterilizing the microorganisms. (2) The method according to the above (1), wherein the aperture portion of the electric field comprises an insulating sheet having an opening and / or a porous insulating sheet. (3) The method according to the above (1) or (2), wherein a direct current is superimposed on the high voltage pulse and applied to perform electrophoresis and induction migration. (4) A high-voltage pulse of the same polarity is applied between the electrodes, a flow-through device for flowing the liquid to be treated in a direction parallel to the electrodes, a narrowing portion of an electric field formed between the electrodes, a counterpart of the electric field formed between the electrodes. And a power supply device for disinfecting microorganisms in a liquid. (5) The apparatus according to the above (4), wherein the aperture portion of the electric field is an insulating sheet having an opening and / or a porous insulating sheet. (6) The device according to the above (4) or (5), wherein the power supply device applies the superimposed high voltage pulse and direct current.

In the present invention, the liquid to be treated is a liquid containing microorganisms. Such liquids to be treated include all those capable of electrophoresis and dielectrophoresis, such as river water, groundwater, industrial water, tap water, drainage, and sewage treatment water.
In particular, high-purity water having low specific conductivity such as pure water and ultrapure water is suitable as a target. Such high-purity water has a specific conductivity of 1
It is preferably at most 00 μS / cm.

The microorganism to be removed is a microorganism present in the liquid to be treated. Examples of the microorganism include bacteria, mold, yeast,
Includes all microorganisms that cause contamination, such as algae. These are originally contained in the liquid to be treated,
Some of them are mixed or generated from outside during the process, and others are mixed in the system by peeling off from the vessel wall or the like.

In the present invention, in order to sterilize such microorganisms, an electric field restricting portion is formed between opposing electrodes, and a liquid to be treated is caused to flow between the electrodes in a direction parallel to the electrodes, so as to have the same polarity between the electrodes. A high-voltage pulse is applied, and the microorganisms in the liquid are moved by electrophoresis and dielectrophoresis, and the microorganisms are trapped and sterilized by a narrow portion of the electric field.

Electrophoresis is a phenomenon in which charged particles move toward an electrode having an opposite charge in an electric field. The electrophoresis occurs in both a uniform electric field and a non-uniform electric field. In contrast, dielectrophoresis is performed in a non-uniform electric field. This is a phenomenon in which a dielectric material is polarized and particles move due to a force generated by the interaction between the induced dipole and an electric field. In this case, the fine particles move on the narrow portion of the electric field, that is, the portion where the lines of electric force concentrate, and are collected on the electrode. Electrophoresis needs to be direct current or pulses of the same polarity, while dielectrophoresis can be alternating or pulsed.

In the present invention, in order to perform such dielectrophoresis, an aperture portion for an electric field is formed between opposing electrodes. The aperture portion of the electric field is a portion where the electric field is concentrated, where the density of the lines of electric force is increased, and the particles move toward this portion and are collected. When plate-shaped electrodes are opposed to each other, particularly when plate-shaped electrodes are opposed to each other in parallel, an insulating sheet having openings such as a punching sheet of a tetrafluoroethylene resin, a mesh, a slit, and a grid is provided between the electrodes. When it is interposed, the electric field concentrates on the opening to form a diaphragm.
Instead of the insulating sheets having such openings, or together with these insulating sheets, a porous insulating sheet such as filter paper or filter cloth may be provided on the electrode surface or between the electrodes to form the aperture portion of the electric field. Since such a porous insulating sheet has many fine openings, it can be used also as a holding portion for collected microorganisms. However, if the number of openings is large, the effect of restricting the electric field may not be large. It is preferable to use in combination with an insulating sheet having

These insulating sheets are preferably arranged near the electrodes. The insulating sheet may be disposed only near one electrode or near both electrodes, but it is preferable to dispose the insulating sheet on both sides since narrow portions are formed on both sides. Such an insulating sheet is preferable because a narrowed portion is formed even when a filter paper and an insulating sheet are provided not only in the vicinity of the electrodes but also in the space between the electrodes. In addition, as the constricted portion, by forming an uneven portion on one of the electrode plates and providing an edge portion, the electric field is concentrated on the edge portion, thereby forming a constricted portion for the electric field. Such a counter electrode may be a concentric cylindrical cylinder type in addition to a parallel plate electrode. In the case where the needle-shaped electrode is provided so as to face the plate-shaped electrode, the electric field is concentrated on the needle-shaped electrode to form a narrowed portion.

It is preferable that such an electric field constricted portion is uniformly distributed over substantially the entire area along the electrode gap of the counter electrode. For example, when an insulating sheet having an opening is interposed between the electrodes, the electric field is narrowed. Preferably, the openings provided in the sheet are arranged uniformly over substantially the entire area of the insulating sheet. Also, when an edge portion is formed on one electrode by an uneven portion, or when one electrode is a needle-like electrode, the edge portion and the needle-like electrode are arranged uniformly over almost the entire area with respect to the other electrode surface. Is preferred.

As the material of the electrode, stainless steel or thorium alloy can be used for both the anode and cathode. Coated electrodes or carbon electrodes can be used. As the insulating sheet having an opening interposed between the electrodes, besides a fluororesin (for example, polytetrafluoroethylene), glass, ceramics, and the like can be used.
A porous material such as filter paper and filter cloth can be used as the porous insulating sheet.

[0015] As the type of the electrode, in addition to the parallel plate electrode,
A concentric cylinder type cylinder, a needle-to-plate electrode, a spiral type electrode wound with a parallel plate electrode, and the like can be used.
In an electrode that forms a uniform electric field, such as a parallel plate electrode, the electric field is narrowed by sandwiching the insulating sheet to form a narrowed portion in which the electric field is locally concentrated, and the collection efficiency is increased by using the dielectrophoretic effect. be able to.

As a power supply device for applying a voltage between the electrodes, a power supply capable of applying a high-voltage pulse of the same polarity can be used, but a power supply capable of applying a DC voltage superimposed on the high-voltage pulse is preferable. Peak voltage 1kV in case of high voltage pulse power supply
１００100 kV, preferably 1 kV５０50 kV, pulse width 10 ^-9秒 10 ^-3 seconds, preferably 10 ^-6秒 10 ^-3 seconds, electric field strength in the diaphragm portion 5 部 50 kV / cm, preferably 5
２５25 kV / cm. The power supply may be a half-wave rectified diode. When a direct current is superimposed, a direct current having a voltage of 50 to 500 V, preferably 70 to 130 V is preferable. The power supply device is switched so as to be turned on during processing, and turned off during cleaning and at rest, but may be configured to apply a reverse voltage during cleaning.

The liquid passing device for passing the liquid to be treated between the electrodes includes:
During processing, the liquid to be treated is introduced from the liquid supply path at one end of the electrode gap to flow the electrodes in parallel, the processing liquid is taken out from the processing liquid path at the other end, and the cleaning liquid is switched from the cleaning liquid path by switching the flow path during cleaning. It is configured to supply and discharge the cleaning waste liquid from the cleaning drain path.

When a liquid to be treated is passed between the electrodes by a liquid passing device with a high voltage pulse of the same polarity applied between the electrodes by the power supply device or a DC voltage superimposed thereon, the underwater is applied by electrophoresis and dielectrophoresis. The fine particles move to the narrow portion of the electric field and are trapped. In this state, a high voltage is repeatedly applied, so that the cell membrane of the microorganism is destroyed and sterilized. The processing liquid from which the microorganisms have been removed is taken out from the processing liquid path. Even if a high-voltage pulse is applied to the liquid to be processed in a flowing state without forming an electric field constriction, the time during which the pulse is applied is short,
It is difficult to sterilize microorganisms contained in the liquid to be treated. Even when an electric field constriction is formed between the electrodes, only microorganisms existing near the electric field constriction are sterilized, and microorganisms existing in other portions are not sterilized. On the other hand, when a high voltage pulse is applied while the microorganisms are captured and held in the narrowed portion, the high voltage pulse is repeatedly applied to the captured microorganisms, so that the sterilization efficiency is increased.

The microorganisms collected on the electrodes are held in the openings constituting the aperture portion of the electric field. However, if they accumulate in large amounts, they will leak together with the treated water, so that they are washed intermittently. In the washing, the microorganisms accumulated near the electrodes can be washed away by stopping the application of the voltage and flowing the washing liquid. At this time, a reverse voltage may be applied. A liquid to be treated may be used as the cleaning liquid, or a treatment liquid may be used.

Even when a low DC voltage of about 100 V is applied, microorganisms can be moved and trapped by electrophoresis and dielectrophoresis, but cannot be sterilized. For sterilization, a high voltage must be applied. In this case, gas is generated by electrolysis, and the collected microorganisms are dispersed.
On the other hand, by applying a high-voltage pulse of the same polarity, generation of gas can be prevented and electrophoresis and dielectrophoresis can be performed. In particular, when a DC voltage is superimposed on a high-voltage pulse and applied, the migration effect by the DC voltage is increased, and the capture of microorganisms is promoted.

[0021]

As described above, according to the present invention, microorganisms in water are captured and killed by electrophoresis and dielectrophoresis, so that microorganisms present in water can be efficiently moved and captured with low power consumption. And can be sterilized. In this case, by applying a high-voltage pulse, the capture and sterilization of microorganisms by the combined use of electrophoresis and dielectrophoresis can be performed more efficiently without generating gas. Can be promoted.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram illustrating a submerged microorganism sterilizing apparatus according to an embodiment.

In FIG. 1, reference numeral 10 denotes an apparatus for disinfecting microorganisms in a liquid. A parallel plate electrode comprising an anode 1 and a cathode 2 is provided in a container 9 so as to face each other. The opposing electrode surfaces 1a and 2a of the anode 1 and the cathode 2 are respectively smooth surfaces, and porous insulating sheets 3 and 4 made of filter paper are provided in close contact with each other. An insulating sheet 5 having an opening 5a made of a punched sheet of polytetrafluoroethylene is provided in close contact with the porous insulating sheet 3 made of filter paper in the vicinity of one electrode (anode 1), and the other electrode (cathode) An insulating sheet 6 having an opening 6a in close proximity to 2) is provided in close contact with a porous insulating sheet 4 made of filter paper. The openings 5a and 6a are provided in the electrode gap 7.
Along the entire surface of the electrodes 1 and 2 to form an electric field aperture.

A power supply device 8 is connected to the anode 1 and a cathode 2
The side is grounded so as to apply a positive high-voltage pulse or a voltage obtained by superimposing a DC voltage on the high-voltage pulse. One side of the electrode gap 7 is connected to a supply / drainage passage 11, and the other side is connected to a supply / drainage passage 12. The supply / drainage path 11 becomes the liquid path 13 to be processed or the cleaning drainage path 14 by switching the flow path, and the supply / drainage path 12 becomes the processing liquid path 15 or the cleaning liquid path 16 by switching the flow path.

In the method for killing microorganisms in a liquid by the above-described apparatus, a positive voltage pulse or a voltage obtained by superimposing a DC voltage on the high voltage pulse is applied between the anode 1 and the cathode 2 by the power supply device 8 to cover the electrode gap 7. The processing is performed while introducing the liquid to be processed from the processing liquid path 13 and extracting the processing liquid from the processing liquid path 15. At this time, since an electric field is formed between the anode 1 and the cathode 2, microorganisms move toward the electrodes by electrophoresis. At this time, since aperture portions for the electric field are formed in the openings 5a and 6a of the insulating sheets 5 and 6, fine particles in the water move toward the portions by dielectrophoresis. In addition, since a myriad of squeezed portions are further formed inside the porous insulating sheets 3 and 4, the squeezed portions are captured and held by these and are sterilized by repeatedly applying a voltage. In this case, dielectrophoresis moves near the openings 5a and 6a of the insulating sheets 5 and 6 on both sides because the particles move to a portion where the electric field density is high regardless of the polarity of the electrodes. Collected and held near the quality opening.

Here, by applying a high-voltage pulse of positive polarity, electrophoresis also occurs, particles having negative charge move to the anode side and are trapped, and this is promoted by superimposing a direct current. For this reason, the negatively charged microorganisms move toward the anode 1 side from the cathode 2 side and are captured. As described above, the two phenomena of dielectrophoresis and electrophoresis occur at the same time, whereby the microorganisms move efficiently and are captured by the insulating sheet 3 on one electrode side. On the other hand, since the lines of electric force are concentrated at the narrow portion of the electric field, a voltage much higher than the applied voltage is obtained, and dielectrophoresis and sterilization are efficiently performed. Electrolysis is prevented by repeatedly applying a voltage with a pulse, thereby preventing generation of gas and sterilizing. At the same time as the capture and sterilization of such microorganisms, capture and removal of other fine particles are performed.

As described above, the microorganisms in the water to be treated move toward the anode 1 and the cathode 2 and are collected, sterilized and held. . When the treatment proceeds and a large amount of microorganisms are trapped, a part of the microorganism leaks into the treated water, so the treatment is stopped and the washing is performed. The cleaning method is performed by stopping the application of the voltage, switching the flow path, flowing the cleaning water from the cleaning liquid path 16, and discharging the cleaning liquid from the cleaning liquid discharge path 14. Since the electric attraction force of the electrode is lost by stopping the voltage application, the microorganisms are easily washed away by the washing water. At this time, by applying the reverse voltage, the detachment of the microorganism can be promoted. It is preferable to use treated water as the washing water.

[0028]

Embodiments of the present invention will be described below.

Example 1 A platinum parallel plate electrode (size 5 cm × 10 cm, electrode interval 4 mm) was used as the anode 1 and the cathode 2 in FIG.
Filter paper (thickness 1) was used as the porous insulating sheets 3 and 4 respectively.
0 μm), and a punching sheet of polytetrafluoroethylene (thickness 1 μm, openings 5a and 6a having a diameter of 1 m) as insulating sheets 5 and 6 to further reduce the electric field.
m, pitch 1.5 mm). A 26 kHz frequency neon transformer was used as a power supply device, a high voltage pulse whose output was half-wave rectified by a diode was applied to the anode 1, and the cathode 2 was grounded. Simulated treated water in which Escherichia coli (1 × 10 ⁶ CFU / ml as a viable cell count) was suspended in pure water was flowed at 100 ml / min as a liquid to be treated, and the cells were captured and sterilized.

Comparative Example 1 In Example 1, the insulating sheets 3, 4, 5, and 6 were not provided.
When a high voltage pulse was applied between the anode 1 and the cathode 2, almost no cells could be collected and sterilization could not be performed.

COMPARATIVE EXAMPLE 2 When a DC voltage of 100 V was applied to the diaphragm of the high-voltage pulse in Example 1, the cells were collected but could not be sterilized.

FIG. 2 shows the time-dependent changes in the viable cell count in Example 1 and Comparative Examples 1 and 2. From FIG. 2, it can be seen that in Example 1, a bactericidal effect appears 5 minutes after the start of water passage, and this stably persists, or Comparative Examples 1 and 2 show no bactericidal effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an apparatus for sterilizing microorganisms in a liquid according to an embodiment.

FIG. 2 is a graph showing the change over time in the viable cell count of Example 1 and Comparative Examples 1 and 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode 2 Cathode 3, 4 Porous insulating sheet 5, 6 Insulating sheet 5a, 6a opening 7 Electrode gap 8 Power supply 9 Container 10 Microorganism sterilizing device in liquid 11, 12 Supply / drainage liquid 13 Treatment liquid Path 14 Cleaning drainage path 15 Processing liquid path 16 Cleaning liquid path

Claims (6)

[Claims] An electric field diaphragm is formed between opposing electrodes, a liquid to be treated is caused to flow between the electrodes in a direction parallel to the electrodes, and a high-voltage pulse of the same polarity is applied between the electrodes to perform electrophoresis and dielectric electrophoresis. A method for disinfecting microorganisms in a liquid, comprising moving microorganisms in a liquid by electrophoresis, capturing the microorganisms in a narrow portion of an electric field, and sterilizing the microorganisms. 2. The method according to claim 1, wherein the electric field diaphragm comprises an insulating sheet having an opening and / or a porous insulating sheet. 3. A high voltage pulse superimposed with a direct current and applied.
3. The method according to claim 1, wherein electrophoresis and induction migration are performed. 4. An opposing electrode, a constricted portion of an electric field formed between the electrodes, a flow-through device for flowing a liquid to be treated between the electrodes in a direction parallel to the electrodes, and a high-voltage pulse having the same polarity between the electrodes. And a power supply device for applying a voltage. 5. The apparatus according to claim 4, wherein the electric field diaphragm is an insulating sheet having an opening and / or a porous insulating sheet. 6. The device according to claim 4, wherein the power supply device applies a high voltage pulse and a direct current in a superimposed manner.