JP2003251340A - Water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment apparatus which can independently be installed in lakes, marshes or the like without power supply from other power sources and in which the efficient decomposition treatment of hazardous substances can be made possible by largely increasing the contact area of a photocatalyst with water. <P>SOLUTION: This water treatment apparatus includes a floating body for floating the apparatus body near the water surface of water to be treated, an aeration means which pumps up the water to be treated from the water depth direction below the floating body and circulates it, a water sprinkling means for sprinkling the water pumped up with the aeration means, near the water surface of the upper part of the floating body, and solar cells to be installed on the position of the upper part of the floating body which is irradiated with solar light. Granular photocatalysts for making granular light- transmissive catalyst carriers carry the photocatalyst are arranged near the water surface of the upper part of the floating body and are brought into contact with the water to be treated which is pumped up with the aeration means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment apparatus which is optimal for treating environmental water in lakes and the like, and more specifically to efficiently treat low-concentration harmful substances represented by environmental hormones present in environmental water. The present invention relates to a water treatment device that can be decomposed into water.

[0002]

2. Description of the Related Art In environmental water such as rivers, lakes and dams,
For example, there are low concentrations of harmful substances represented by environmental hormones. In the treatment of such low concentration harmful substances,
As the owner is not clear like rivers and lakes,
There are many areas where the management body has not been decided, and it is necessary to keep running costs as low as possible and perform efficient processing. In the decomposition treatment of low-concentration harmful substances, it is considered that a photocatalyst such as TiO _{2 that} can effectively utilize sunlight is advantageous in terms of performance and cost. So far, floating type (Japanese Patent Laid-Open No. 11-104629, Japanese Patent Laid-Open No. 9-174046) and liquid-feeding (Japanese Utility Model Laid-Open No. 6-85085, Japanese Patent Laid-Open No. 9-131587) water treatment technologies that utilize sunlight have been proposed. In the floating type (type in which the liquid on the surface does not flow), a raft-like floating material is floated on the water surface, and by the action of the photocatalyst such as titanium oxide coated on the surface of this floating material
Treat water in sunlight. The liquid transfer type (type in which surface liquid flows) is mainly used in environmental water where there is a certain degree of gradient such as in rivers, or in environmental water in which liquid can be artificially flowed, for example, by a pump. It is a device that is used and installed slightly submerged from the water surface. The photocatalyst is applied to the upper surface on the water surface side, and the liquid flowing above the upper surface of the device is decomposed by the action of sunlight and the photocatalyst.

However, although the conventional floating type and liquid feeding type devices are effective for purifying water near the surface of environmental water, in order to efficiently promote purification of the entire enclosed environmental water (for example, the entire lake) and natural purification. Was insufficient. In order to purify the environmental water of the whole lake, it is necessary to purify not only the surface but also the water layer other than the surface, for example, the deep water of the lake. In particular, deep water above a certain level in lakes and marshes exists as a non-convective layer. Even if water circulates in the convective layer from the surface to a certain depth, water circulation does not normally occur in the non-convective layer. . In addition, for example, for harmful substances with a specific gravity of more than 1 and substances that easily adhere to dust, etc., because they sink in deep water in environmental water, they are forced to circulate,
If oxygen is not supplied to the deep water and self-cleaning is promoted, pollution will gradually progress from the lower part of the environmental water. Therefore, in order to treat the water in the water layer portion other than the surface, a water circulation device that forcibly circulates the water near the surface is required,
A more powerful purifying action is required to efficiently treat a large amount of treated water generated by such circulation.

On the other hand, the conventional water circulation device has the function of promoting self-cleaning and filtering foreign substances, but does not decompose the above-mentioned low-concentration harmful substances. Further, in the environmental water, foreign matters may be deposited on the photocatalytic water treatment device while the water is flowing, or the tubular portion may be clogged or blocked. Such foreign matter has adhered to the surface of the photocatalyst and has been a cause of blocking sunlight. As a result, the catalytic action is reduced and the efficiency of water purification is also reduced.

On the other hand, conventionally, there is known an apparatus in which a photocatalyst is provided on a floating body and a conveying path by a screw or the like and a rectifying plate are provided. For example, since the catalyst layer has a plate wave shape, light can be received even when the angle of the sun changes A mode for doing so has also been proposed. However, when the photocatalyst is fixed to act as a photocatalyst layer, the decomposition processing speed of harmful substances by the catalyst is slow, durability or catalyst activity is deteriorated due to accumulation of dirt on the catalyst surface, and regeneration or replacement of the catalyst is difficult. Therefore, there was a problem that regular maintenance was required. Also,
There is a possibility that sunlight will be attenuated at the contaminated part, and further reduction of treatment efficiency was considered. Furthermore, when a rectifying plate is used as the device configuration, the rectifying plate may reduce the light receiving area of the catalyst layer or the solar cell, which reduces the light receiving surface area of the catalyst. In such a conventional treatment apparatus using a catalyst, since it is necessary to efficiently contact water and the photocatalyst, the catalyst is applied to a flat surface to form a layer, and therefore the application surface It is difficult to contact the catalyst with the above area. Even if the catalyst is applied thickly on the coated surface, the effect does not change because the permeation into the treated water is not seen, and even in the laminated type, the light acts only on the uppermost part. As a result, environmental water was limited to water purification near the water surface.

[0006]

In view of the above problems, the present inventors have made it possible to efficiently increase the contact area between the photocatalyst and water and efficiently decompose the harmful substances.
We have earnestly studied to develop a water treatment device that can be installed independently in lakes and marshes without supplying electric power from other power sources. As a result, the present inventors have made it possible to increase the surface area by using a granular photocatalyst, and by combining the granular photocatalyst with an aeration means for closed water circulation, an efficient photocatalytic action can be exerted to achieve high water content. Purification effect is obtained,
It has been found that such problems can be solved by using a solar cell as a power source for aeration. The present invention has been completed from this point of view.

[0007]

[Means for Solving the Problems] That is, according to the present invention, a floating body for floating an apparatus main body near the surface of treated water, an aeration means for pumping and circulating the treated water from the depth direction of the lower part of the floating body, and the aeration means. The treated water pumped by the above, spraying means for spraying near the water surface of the upper part of the floating body, and a solar cell installed at a position on the upper surface of the floating body where sunlight is irradiated,
And a granular photocatalyst in which a photocatalyst is supported on a granular catalyst carrier having a light-transmitting property, the granular photocatalyst is disposed near the water surface above the floating body, and is brought into contact with the treated water pumped up by the aeration means. A processing device is provided. Here, in the present invention, it is preferable that the granular photocatalyst is supplied into the treated water by the aeration means, is sprayed from the water sprinkling means to the vicinity of the water surface together with the treated water, and then the granular photocatalyst is collected by the collecting means. Also, on the water surface around the aeration means,
A mode in which a photocatalyst device comprising a floating particulate photocatalyst is also included. In the present invention, a high water purification action is obtained by combining a photocatalyst with an aeration (pumping) means for circulation in a closed water area, and a solar cell is used as a power source in that case.
Here, the granular photocatalyst is preferably magnetic catalyst particles, which can reduce the load in the recovery means (recovery step) and improve the utilization efficiency of the catalyst particles.

In the present invention, a photocatalyst layer may be provided on the surface of the floating body on which the sunlight is irradiated. As a result, the harmful substances can be more efficiently treated from the treated water on the upper surface of the device. Further, in the present invention, the solar cell is preferably made of a transparent or translucent material and allows a part of sunlight to pass through. This allows the photocatalyst layer to be superposed on the photocatalyst layer, and the device itself can be downsized. further,
According to the aspect of installing the artificial light source under the photocatalyst layer,
The purification process can be performed even at night when the sun is not available or in bad weather. In this case, it is efficient to cover the power of the artificial light source with the electric power obtained by the solar cell. By providing the artificial light source driven by such a solar cell, the purification speed of the entire environmental water can be promoted.

The granular photocatalyst used in the present invention is
A photocatalyst is supported on a granular catalyst carrier having light transparency. The catalyst carrier is not particularly limited as long as it has a light-transmitting property, but an inorganic light-transmitting material such as quartz, silica gel, or glass is preferable. Further, from the viewpoint of securing a large supported area for the catalyst carrier,
It may be a porous shape or material. And
A material that is resistant to light attenuation and has abrasion resistance is preferable.

The types of photocatalyst components used in the present invention include, for example, TiO ₂ , ZnO, WO ₃ , SnO, SrTiO ₃ , S
Examples thereof include iC, Fe ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ , B ₂ O ₃ , P ₂ O ₃ and CdS. Examples of the shape of these photocatalysts are spherical,
It may be cylindrical, polygonal, prismatic, ellipsoidal, plate-like, or powdery. For use as a granular photocatalyst, a spherical or ellipsoidal catalyst is preferable in consideration of filling and abrasion. These photocatalytic components are
In addition to being supported on the catalyst carrier, it can also be used for a photocatalyst layer.

The particle size of the granular photocatalyst is usually 0.1 to 100 m.
m, preferably 1.0 to 10 mm. 100
If it exceeds mm, the particles are too large, which may cause inconvenience during circulation, and in particular, it may be difficult to raise by the aeration means, which is not preferable. If it is less than 0.1 mm, it is difficult to manufacture the particles, and the loss is increased when the particles are circulated, which is not preferable. The optimum particle size is such that the surface area is increased as much as possible and clogging is less likely to occur, for example, a particle size of about 3 mm.

Further, in the present invention, a catalyst having magnetism can be used as the above-mentioned granular photocatalyst, and when such a catalyst is used, the catalyst can be easily recovered by magnetic separation by the recovery means. it can. In addition, a method other than magnetic separation can be used as the recovery means, and examples thereof include a method of recovering the catalyst after separation by using a difference in specific gravity and a method of recovering the catalyst after solid-liquid separation. Since the photocatalyst has a protective function as compared with other catalysts, the degradation activity is usually less deteriorated. However, deterioration is gradually progressed by continuous use in environmental water for a long time. Therefore, according to the aspect of circulating the catalyst as in the present invention, the self-cleaning mechanism is sufficiently exerted and dirt that causes deterioration is less likely to adhere to the catalyst particles, and the replacement of the granular photocatalyst or the addition of a new catalyst is added. Can be done very easily.

In the treatment of harmful substances using a photocatalyst, the harmful substances are decomposed by a chemical reaction. Usually, the photocatalyst is exposed to sunlight in the presence of oxygen,
Decomposes harmful substances such as environmental hormones. When titanium dioxide (TiO ₂ ) is used among the above photocatalysts, when irradiated with light having a band gap or longer (wavelength shorter than 390 nm), electrons of the valence body are excited in the conduction band, and holes are generated in the traces. . The holes react with harmful substances in the aqueous solution and oxidize them, as well as water and O adsorbed on the surface of titanium dioxide.
H ^-, or to generate OH radicals react with Chitanoru group, there are cases where this radical oxidizes harmful substances. Further, the electrons and reducing the oxygen dissolved in water, O ₂ ^- generated radicals. This radical is considered to generate an OH radical via H ₂ O ₂ .

Here, if both holes and electrons are not consumed, they are recombined and the reaction is stopped. In the water treatment with titanium dioxide, the reaction of holes is more efficient and the reaction of electrons is slower. Therefore, by adding an electron acceptor such as H ₂ O ₂ , separation of holes and electrons is maintained. It can promote efficiency. According to the present invention as described above, the contact area between the photocatalyst and water can be significantly increased to decompose the harmful substances extremely efficiently, and the catalyst can be easily regenerated and replaced without requiring regular maintenance. Become. Further, the device alone can be operated voluntarily and independently without supplying electric power used for the aeration means from another power source.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of a processing apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the entire processing apparatus of the present invention, and FIGS. 2 and 3 show an example of a mode used in addition to FIG.

In the present embodiment shown in FIG. 1, the solar irradiation surface of the aeration device 3 (including the pump 11) for purifying water driven by the solar cell 10 mounted on the floating body 2 comes into contact with water. A granular photocatalyst 1 that decomposes harmful substances in the treated water is arranged in the portion to be treated. In the device of the present invention, the aeration device 3 and the floating type floating body 2 are combined, the treated water is sucked and aerated from the depth direction, and is raised to the sprinkler device 4 above the floating body 2. Then, the treated water that has risen is discharged from the sprinkler 4 to the surface of the upper surface of the floating body 2 that is exposed to sunlight. At this time, it is preferable that the treated water is discharged in the vicinity of the sprinkler 4. As a result, the treated water pumped from the lower part of the aeration device 3 can be brought into contact with the granular photocatalyst 1 within the range of sunlight to decompose the contained harmful substances.

In the present invention, by circulating the treated water using the aeration device 3, convection is generated even in the deep part of the closed water area, and air is sent to promote self-cleaning, and the power source at that time is the solar cell 10. To do. According to the present invention, it is possible to bring the entire environmental water into contact with the photocatalyst by pumping water even from the lower part of the environmental water, even if the treated water was able to contact the photocatalyst only near the surface of the environmental water. The decomposition process can be accelerated. As for the power of the aeration device 3 that pumps the treated water from below, the power source can be secured by the solar cell 10 incorporated in the floating body 2. In addition, since the decomposition by the photocatalyst does not proceed in the place or the time zone where the sunlight is not irradiated, it is not usually necessary to perform the pumping by the aeration device 3 at night. Therefore, if the solar cell 10 can secure the power source during the daytime, the decomposition treatment by the photocatalyst can be effectively performed.

The aeration device 3 is provided in the depth direction of environmental water.
It is a device that sucks up treated water to the upper part of the floating body 2 and circulates it. Specifically, for example, a method of sucking water using a pump 11 or a method of installing an air pump (air lifter or ejector) for sending air to the lower part of the apparatus to reduce the specific gravity of the treated water and circulate the water. , And so on. Install a tower-shaped tube at the bottom in the depth direction,
The treated water is sucked into the inside of the cylinder from the bottom to the top. This makes it possible to build up the water in the non-convective layer in a lake or the like into the convective layer. In the treatment of low-concentration harmful substances such as the target of the present invention, for example, environmental hormones, there are many substances that are difficult to biologically treat, and it is difficult to treat by simple aerobic / anaerobic treatment. In the present invention, the low-concentration harmful substance in the treated water that has been aerated and increased is effectively decomposed by the above-described decomposition action of the photocatalyst.

The sprinkler device 4 is a device that sprinkles the treated water sucked up by the aeration device 3 thinly and uniformly on the surface of the water on which the photocatalyst is placed. The treated water evenly sprinkled by the water sprinkler 4 is decomposed by the action of the photocatalyst in the low concentration of harmful substances contained in sunlight. It is preferable that the treated water be thinly flowed in all directions, and sprinkled so that the treated water flows on the upper surface of the apparatus without separating from the floating body 2 as much as possible. From the viewpoint of efficient recovery of the granular photocatalyst 1, the spraying range is usually within the upper surface area up to the end of the floating body 2, and preferably from the viewpoint of ensuring sufficient contact with the treated water. Sprinkler 4
To the end of the floating body 2 is within a ½ range, and more preferably within a ¼ range of the distance from the sprinkler 4 to the end of the floating body 2.

The solar cell 10 attached to the floating body 2 is
It is installed to supply electric power as a power source such as a pump of the aeration device 3. Usually, panel type solar cells are arranged side by side on the upper surface of the floating body 2. The materials of the solar cell 10 used are classified as follows. Solar cells are roughly classified into silicon type and compound type solar cells.
Any solar cell (such as Group III or Group III-V) can be used. Silicon-based solar cells include crystalline and amorphous (non-crystalline) solar cells. The crystal system has excellent power generation efficiency, and it is a thin film type single crystal (GaAs, InP) or polycrystal (CdS / CdT).
In addition to (e, CIS), a polycrystal is preferably used in a bulk system. On the other hand, when amorphous is used, the cost can be reduced because thin film amorphous silicon is grown on a low-cost substrate such as glass. In addition, in recent years, light-transmitting solar cells have also begun to be developed.
If a light transmissive solar cell as proposed in -339087 (daylight type solar cell module and daylighting type solar cell system) is used, the photocatalyst and the solar cell can be stacked. Amorphous silicon is often used as the solar cell material here. With such a solar cell,
Since aeration power can be supplied independently inside the device, it can be installed anywhere beyond the power transmission site, and is particularly effective in environments such as lakes and marshes. Also, in terms of running cost, the electricity bill can be suppressed low.

In the present invention, as shown in FIG. 2, the photocatalyst layer 6 may be provided on the surface of the upper surface of the floating body 2 which is irradiated with sunlight. Since the surface of the solar cell 10 is large, the photocatalyst is applied to the surface of the floated body of the solar cell to improve the decomposition efficiency of the treated water. According to such an aspect, since the photocatalyst is fixed and carried in the vicinity of the liquid surface of the device irradiated with sunlight, water purification is further promoted. However, since the photocatalyst layer 6 is not completely transparent, the light may be attenuated in the depth direction to make it difficult for the light to reach the solar cell, and the photocatalyst layer 6 may be decomposed as much as possible. It is preferably thin. Alternatively, the photocatalyst can be applied to the surface not having the solar cell 10, for example, in a grid pattern.

In the present invention, since the granular photocatalyst 1 is introduced near the water surface, a means for collecting the particles is provided. For example, the particles are collected by a magnet by making the granular photocatalyst a magnetic substance. Various modes are conceivable for the method of circulating the photocatalyst particles, and the method is not limited at all. Specifically, for example, as shown in FIG. 4, a method of introducing photocatalyst particles in the middle of the cylinder of the aeration device 3 can be considered. According to this method, the granular photocatalyst 1 is uniformly mixed in the water sprinkled from the water sprinkler 4, so that the catalyst and the water are evenly and uniformly contacted with each other to decompose the harmful substances. In the collecting means for the granular photocatalyst flowing on the upper surface of the solar cell 10, for example, a collecting device having an electromagnet is provided below the end of the floating body 2 in the deep water direction. The granular photocatalyst 1 collected in the recovery device is sent through a pipe or the like in the middle of the cylinder of the aeration device 3 and is used again as a photocatalyst.

The catalyst recovery device is not limited to the type in which a magnetic material is attracted by a magnet, and may be any other method as long as it can recover particles in water existing in the vicinity. Since the catalyst particles are heavier than water and precipitate in the lower part, for example, a mode in which a precipitation tank is provided in the lower part of the end of the solar cell can be mentioned. The bottom surface of the settling tank only needs to be able to be trapped without passing the catalyst particles, and may have, for example, an inclined plate-like body or a mesh-like structure. The inclination inside the settling tank is preferably such that the particles roll toward the aeration device. The catalyst particles accumulated at the end inside the settling tank due to this inclination are sent to the aeration device by a transfer means such as a pipe. In the aeration device,
When circulating the granular photocatalyst, it is necessary to aerate the water with a certain power or more in relation to the particle concentration. A single particle in water gradually accelerates to settle due to the action of gravity, but on the other hand, since the resistance force of water due to the settling works in the opposite direction, it becomes constant from the time when gravity becomes equal to the resistance force. It begins to settle at a speed. The velocity at this time is called the terminal sedimentation velocity and can be expressed by the following formula.

[0024]

[Equation 1]

Where V _t : terminal sedimentation velocity, g: gravitational acceleration, D
_p : particle diameter, ρ _s , ρ _L : density of particles and liquid, C: resistance coefficient of liquid. For example, when a granular photocatalyst having almost the same specific gravity as water which is liquid is used, the final sedimentation velocity Vt is 0. It means that the granular photocatalyst circulates even if there is a slight water flow.
The location of introducing the particles is not particularly limited, but when adding from the lower part of the aeration, it is necessary to raise the particles to the upper part.

Further, in the present invention, as shown in FIG. 3, an artificial light source (for example, a UV lamp 5) driven by a solar cell 10 is provided to irradiate sunlight during daytime and artificial light during nighttime or bad weather. It is also possible to provide a water purification device that can be decomposed even when it is not exposed to sunlight. By providing the artificial light source, the water can be purified for a long time and the purification speed can be improved. Further, since the driving force is the solar cell, the running cost can be suppressed.

[0027]

According to the water treatment apparatus of the present invention, since the contact area between the photocatalyst and the treated water can be widened, the reaction efficiency is greatly improved. Further, as compared with the fixed type processing apparatus using only the photocatalyst layer, the circulation type apparatus of the present invention is less likely to stain the surface of the photocatalyst and is less likely to cause catalyst deterioration. Further, the catalyst particles can be replenished or replaced, and maintenance during operation is easy.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing an example of a water treatment device of the present invention.

FIG. 2 is a configuration diagram when a photocatalyst layer is provided in addition to the device of FIG.

FIG. 3 is a configuration diagram of a case where a UV lamp is provided in addition to the device of FIG.

FIG. 4 is a configuration diagram in the case of circulating a granular photocatalyst in the apparatus of FIG.

[Explanation of symbols]

1 Granular photocatalyst 2 floating body 3 Aeration device 4 Sprinkler 5 UV lamp 6 Photocatalyst layer 10 solar cells 11 pumps

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhiro Sueoka             1-8 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa               Mitsubishi Heavy Industries Yokohama Research Center F-term (reference) 4D029 AA01 AB05 BB11                 4D037 AA05 AB18 BA16 BA18 CA12                 4D050 AA02 AB11 BB01 BC06 BC09                       BD03 BD06                 4G069 AA03 BA01A BA02A BA04A                       BA04B BA05A BA14A BA38                       BA48A BB01A BB04A BB06A                       BB09A BB15A BC12A BC22A                       BC35A BC36A BC50A BC60A                       BC66A BD02A BD03A BD05A                       BD07A CA05 EA02X EA02Y                       EB18Y EC27

Claims (6)

[Claims] 1. A floating body for floating the apparatus main body near the surface of the treated water, an aeration means for pumping and circulating the treated water from the depth direction of the lower part of the floating body, and a treated water pumped by the aeration means for treating the treated water above the floating body. Of a water-dispersible granular catalyst carrier including a water-spraying means for spraying near the water surface and a solar cell installed at a position on the upper surface of the floating body where sunlight is irradiated. A water treatment device, wherein a photocatalyst is arranged near the water surface above the floating body and brought into contact with the treated water pumped up by the aeration means. 2. The granular photocatalyst is supplied to the treated water by an aeration means, is sprayed together with the treated water near the water surface from an aeration means, and then the granular photocatalyst is recovered by a recovery means. Water treatment equipment. 3. The water treatment device according to claim 1, wherein the granular photocatalyst is magnetized catalyst particles. 4. The water treatment apparatus according to claim 1, wherein a photocatalyst layer is provided on a surface of the floating body on which the sunlight is irradiated. 5. The water treatment device according to claim 1, wherein the solar cell is made of a transparent or translucent material and allows a part of sunlight to pass therethrough. 6. The water treatment device according to claim 1, wherein an artificial light source is installed below the photocatalyst layer.