JPH11319857A - Photocatalytic reaction apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalytic reaction water treating apparatus which enables continuous, stable radiation of ultraviolet of a specific strength to a catalyst surface, causes no toxicity, generates no by-product and has a low initial cost. SOLUTION: A photocatalytic reaction apparatus is equipped with mutually connected multiple water tanks 10-15 allowing the treated water to successively flow into the next tank, rotating bodies 1-6 carrying photocatalysts, which are individually placed in each tank and partially soaked in the treated water in the tank and ultraviolet radiation means 28-39 placed in the atmosphere adjacent to each rotating body. The treated water in each water tank 10-15 is stuck to the rotating bodies 1-6, transferred to the atmosphere by the rotation of the rotating body and irradiated with ultraviolet in the atmosphere to avoid decrement of the ultraviolet radiation strength generated in underwater radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water treatment technique, and more particularly, to a water treatment apparatus utilizing a photocatalytic reaction.

[0002]

2. Description of the Related Art Ozone (O ₃ ) treatment is often used in pretreatment of seawater in water purification treatment and seawater desalination. This ozone treatment has remarkable effects such as removal of mold odor, decolorization of a colored organic substance, improvement of a coagulation effect, and sterilization. However, the initial cost required for this ozone treatment is enormous, and the energy efficiency required for generating ozone is extremely low.
As for the ozone generator, an improved version of the Siemens system developed in the 19th century is still the mainstream. Of course, today's advances in electronics are reflected in improvements in the functional components of the ozone generator, but the low efficiency resulting from the fundamental ozone generation reaction has not been improved much. It is. From such a technical point of view, it is considered that those in the mature stage are gradually replaced by other new systems. Among these new methods, one of the research themes in national research institutes is water treatment using photocatalysts. Various types of photocatalysts are already known, and among them, titanium dioxide (TiO ₂ ) is harmless to the human body and can be obtained or processed relatively easily.

[0003]

Therefore, a water treatment apparatus utilizing this titanium dioxide is conceived. In such a technology of treating an organic substance in water treatment using titanium dioxide, a method of applying a photocatalyst to water treatment involves interposing water to be treated between the photocatalyst surface and an ultraviolet lamp as a light source, Chemical species having a very strong action such as OH radicals generated on the photocatalyst surface by irradiation of ultraviolet rays are used for a decomposition reaction or inactivation of organic substances and bacteria in water. Therefore, in order for the photocatalyst to continue to emit these effective species, ultraviolet light of an appropriate intensity must be continuously irradiated on the photocatalyst surface in water. However, when a method of irradiating ultraviolet rays in water is assumed, attenuation of the intensity of the ultraviolet rays until reaching the surface of the photocatalyst becomes a problem.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an apparatus capable of continuously irradiating the photocatalyst surface with ultraviolet rays of an appropriate intensity stably, with less toxic and by-products. A first object is to provide a device having a low initial cost. By the way, in the case of treating water whose turbidity is not yet complete, it is necessary to always remove microorganisms and turbid substances which are to adhere to the surface of the photocatalyst. Therefore, the present invention works to reduce the above-mentioned photocatalytic action and always removes microorganisms and turbid substances that are likely to adhere to the ultraviolet lamp and the photocatalytic surface in water.
The purpose of. Further, a third object of the present invention is to make the effect of the photocatalytic reaction more remarkable when used in combination with biological treatment. A fourth object of the present invention is to increase the processing efficiency of the apparatus.

[0005]

In order to achieve the above-mentioned object, the present invention provides a photocatalytic reactor comprising a plurality of water tanks connected to each other so that water to be treated can flow to the next water tank sequentially.
By arranging each part in each water tank so as to be immersed in the water to be treated in the water tank, a rotating body carrying a photocatalyst, and an ultraviolet irradiation means arranged in the air adjacent to each rotating body. The water to be treated in each water tank is attached to a rotating body, carried out to the air by the rotation thereof, and treated by irradiating ultraviolet rays in the air. In this case, an ultraviolet irradiation means arranged in water can be added. In order to achieve the second object, each of the water tanks is provided with an ultrasonic vibrating means for vibrating the water to be treated. Further, in order to achieve the third object, a water tank having a rotating body that does not carry a photocatalyst is connected upstream of a large number of water tanks. And the fourth
In order to achieve the above object, the most downstream water tank and the most upstream water tank are connected by a treated water return line.

[0006]

In the apparatus having the above structure, the portion supporting the photocatalyst is similar to the rotating disk method which has already been established as one of biological treatment methods in water treatment. By doing so, the surface on which the photocatalyst is supported and the water to be treated are sufficiently contacted, and a stable treatment effect is expected. Further, by rotating the photocatalyst-carrying portion, it becomes possible to irradiate ultraviolet rays in the air. In this device, even if the irradiation of ultraviolet rays is performed in the air, a thin film of water always exists on the surface of the rotating body, and the basic process of interposing water between the ultraviolet light source and the photocatalyst. The form is satisfied. In addition, since ultraviolet rays only pass through a thin film of water, the intensity of the ultraviolet rays before reaching the surface of the photocatalyst is less attenuated compared to the method of irradiating ultraviolet rays only in water, and efficient photocatalyst utilization is possible. become. In this case, more efficient use of the photocatalyst becomes possible by adding an ultraviolet irradiation means arranged in water as described in claim 2.

Next, at the stage where the turbidity of the water to be treated is not perfect, it is necessary to always remove microorganisms and turbid substances which are to adhere to the surface of the photocatalyst. As the means, it is a very effective means to apply ultrasonic waves in water and maintain the suspended matter in water to be attached to the rotating body carrying the photocatalyst in a dispersed state. obtain. Furthermore, the application of ultrasonic vibrations serves to accelerate the reaction of the photocatalyst, which is said to be relatively slow. It is already known that ultrasonic waves accelerate reactions in water, but there is no established theory as to what mechanism is used.

Further, according to the constitutions of claims 4 and 5, the present method is used as a follow-up to the rotating disk method which is a normal biological treatment, thereby supplementing substances which cannot be easily decomposed and removed by the biological treatment. Can be decomposed. In biological treatment, the turbidity of raw water can be sufficiently expected, and this combination works advantageously for the photocatalytic device.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the photocatalytic reaction device of the present invention will be described below with reference to the drawings. One embodiment of the photocatalytic reaction device of the present invention will be described with reference to FIGS.
FIG. 1 is a plan view of a photocatalytic reactor embodying the present invention (however, an upper hood is omitted). This apparatus is mainly composed of a large number of water tanks 10 to 15 provided with a large number of rotating disks 1 to 6 constituting a rotating body carrying a photocatalyst. In the drawing, the case where the number of rotating disks is six is exemplified, but the number of disks and the number of water tanks corresponding thereto are adjusted as necessary.

The rotating disks 1 to 6 carrying the photocatalyst are placed in water tanks 10 to 15 surrounding the lower part of the rotating disk so as to have an appropriate immersion rate, for example, about 30 to 40%. . These water tanks are connected to each other in the front and rear, and are arranged in such a manner that the degree of processing increases as the water tank 10 in the preceding stage shifts to the water tank 15 in the subsequent stage.

As shown in FIG. 2, on the bottom of each of the water tanks 10 to 15 in which the rotating disks 1 to 6 are immersed, ultrasonic vibration means for generating ultrasonic waves by driving with an oscillator 42, specifically, Child boxes 20 to 25 are provided. These vibrator boxes 20 to 25 actuate the vibrator while the rotating disks 1 to 6 are rotating, disperse turbidity and organisms that are to adhere to the disk surface, and constantly keep the disk surface It is provided to help clean and irradiate the irradiated ultraviolet light efficiently on the photocatalyst supported on the disk. The ultrasonic vibrations given by this process simultaneously promote the decomposition reaction of organic substances by OH radicals and active oxygen transferred into water by the reaction promoting action unique to ultrasonic waves, shortening the required reaction time of the entire device, and making the device compact. It also has the intent to make it happen.

The rotating disks 1 to 6 carrying the photocatalyst have the same diameter. These disks are fixed to a rotation shaft 9, and a rotation motor 26 is installed at one end of the shaft 9 via a speed reducer 27. These allow the peripheral speed of the disk to be changed by controlling the rotation speed of the motor 26 in order to appropriately adjust the thickness of the thin film of water through which the ultraviolet light passes. In the present embodiment,
The rotating disks 1 to 6 supporting the photocatalyst and the rotating disks 7 and 8 not supporting the photocatalyst described later are
And rotating at the same number of revolutions, but depending on the quality of the raw water, the rotating disks 1 to 6 carrying the photocatalyst
By mounting the rotating disks 7 and 8 that do not carry the same on separate rotation shafts or via a reduction gear, each can be configured to rotate at an optimum rotation speed.

The water tank 17 is connected to a raw water supply line by a raw water inflow port 18 so that raw water as the water to be treated first flows into a water tank 17 at a stage preceding the water tank 10 on which the disk 1 is disposed. In the water tank 17, a plastic ordinary rotating disk 7 that does not carry a photocatalyst is fixedly mounted on a rotating shaft 9 common to the other rotating disks.
As described above, the rotating disk 7 removes turbidity in raw water to some extent by biological treatment. If this turbidity is not sufficient with a single biological treatment rotating disk 7, the number of disks may be increased as appropriate.

In the subsequent stage of the photocatalytic reaction tank 15 in the last stage, a usual rotating disk processing tank 16 is provided. The material of the rotating disk 8 used here is the same as that of the rotating disk 7. The water in the tank 16 is already almost aseptic, and the quality of the treated water is maintained in a good condition macroscopically. This state can be known by observing the surface of the rotating disk 8. it can. Also, depending on the quality of the raw water,
It is also possible to use the organic substance degraded by the photocatalyst by biological treatment with the rotating disk 8 at the subsequent stage.

In order to irradiate the rotating disks 1 to 6 carrying the photocatalyst with ultraviolet rays, a pair of mercury lamps 28 to 39 sandwiching the disks are disposed near each disk as an ultraviolet irradiation means.
Are supported by appropriate means so as to be positioned in the air. In this case, if necessary, mercury lamps 28 'to 39' may be arranged in the water below the mercury lamps 28 to 39 arranged in the air as ultraviolet irradiation means so as to correspond to the mercury lamps 28 to 39. This enables more efficient use of the photocatalyst.

Although not shown, a UV-cuttable hood is attached to the upper part of the apparatus to prevent foreign substances from entering and preventing contamination. Since the hood generates low-concentration ozone (O ₃ ) by continuous irradiation of ultraviolet rays, it is necessary to prevent ozone from leaking out of the apparatus.

In addition, when the organic substance reduced in molecular weight is subjected to biological treatment again in this photocatalytic reaction device, the state of ingestion into living organisms is improved by the reduction in molecular weight, so that the biodegradability is enhanced, and as a result, the overall device becomes The processing efficiency is improved. Therefore, in this apparatus, a return line 40 for returning or circulating the water to be treated is provided so as to connect the downstream of the treatment water tank 16 and the supply line of raw water as shown in FIG. It is determined whether or not to perform the return processing by the return line depending on the condition of the treated water. Therefore, the return line 40 is provided with a cock 41 for switching the flow path.

Further, in order to improve the activation of the photocatalyst, the hood of the photocatalyst reaction unit (not shown) is made to be a closed type, and the ozonized air generated from a small-sized ozone generator can be introduced into the hood. It is also effective to do so. In this case, an ozone monitor is used to control the internal ozone concentration to an appropriate level. At the time of inspection, the ozone generator is stopped, the air inside the hood is exhausted by an exhaust fan, and unnecessary ozone is adsorbed on activated carbon, giving consideration to the environment.

In the apparatus configured as described above, while the raw water is supplied from the supply line, all the rotating disks 1 to 6, 7, and 8 are rotated by the driving of the motor 26 via the reduction gear 27 and the rotating shaft 9. Mercury lamps 28-39 placed in the air and mercury lamps 28'-3 placed in the water.
9 ′ is turned on to irradiate the photocatalyst carried on the rotating disks 1 to 6 with ultraviolet light.
The apparatus is operated by ultrasonically vibrating 0 to 25 and conducting ozonized air generated from a small-sized ozone generator into the hood as necessary. Thereby, first, the raw water entering the water tank 17 from the raw water inflow port 18 adheres to the biological treatment disk 7 and is subjected to biological treatment.
Enter 0. The water to be treated that has flowed into the water tank 10 adheres to the rotating disk 1 in a state where turbidity is separated by ultrasonic vibration, is taken out into the air, and is irradiated with ultraviolet rays. The water after the treatment flows to the next water tank 10 via the connecting portion. In the same manner, the water to be treated finally reaches the water tank 16, the water quality is checked with the water attached to the monitoring disk 8, and the water is discharged as treated water.
If it is determined by the monitoring by the monitoring disk 8 that further treatment is necessary, the cock 14 is opened and the treated water is fed back to the raw water inlet side through the return line 40.

Incidentally, in the case of conventional water treatment using ozone, a dedicated reaction device is required. Since the generator must be stored indoors, a dedicated building is required. Further, an exhaust ozone treatment device is required for removing residual ozone, and the initial cost including these is high for ensuring safety. In contrast, a photocatalytic reactor requires a reaction tank and power supply, but it is necessary to use a storage facility such as ozone-based water treatment, an air source compressor, a blower, and a discharge tube cooling device. There are few expensive facilities. In addition, there is an advantage that maintenance becomes easy because the number of parts is small.

By the way, a full-scale study of a photocatalyst using titanium dioxide has been carried out by obtaining oxygen and hydrogen from water using sunlight.
It then began with gaining energy (eg, MITI's Sunshine Program). Since it was pointed out that titanium dioxide can be applied to the oxidation of organic substances, decomposition experiments were conducted on titanium dioxide, which is a difficult-to-decompose organic chlorine compound such as trichloroethylene, monochloroacetic acid, PCB, and dioxins. Is shown. In addition, a photocatalyst was used for sewage, and the effect was observed. As a result, all of COD, BOD and TOC showed a significant decrease. In addition, a technique for coating titanium dioxide on a surface of glass or the like has already been established. With this technology, the trouble of collecting titanium dioxide, which is originally a powder, can be eliminated, and continuous operation in the water purification treatment field has become possible. At present, there is no example of operating as a real device, but it is a technology expected as a mainstream advanced processing in the early 21st century due to the various advantages described above.

The relationship between the use and effect of the photocatalytic reactor of the present invention will be listed below. In the water purification treatment, when used for the decomposition of humic substances, the effect of adsorbing on activated carbon increases, and the ability to generate trihalomethane decreases. Further, an effect of reducing chromaticity can be obtained. Similarly, when used for inactivating bacteria in water purification treatment, the performance of activated carbon treatment is stabilized by removing bacteria unnecessary for activated carbon treatment. In addition, Fe, Mn in water purification treatment
When used for oxidation of water, an effect of improving water quality can be obtained. Also,
Combined with activated carbon treatment will lead to lower chromaticity. Similarly, when used for the decomposition of odorous substances in water purification treatment, an ozone treatment facility becomes unnecessary due to improvement in water quality. Further, when used as a substitute for an ozone treatment facility in water purification treatment, an increase in water charges can be suppressed due to a reduction in initial costs.

When used for pretreatment of seawater desalination using a reverse osmosis membrane as an application other than the above, the life of the separation membrane is prolonged due to decomposition of an organic substance which easily causes fouling of the membrane, and the running cost can be reduced. . Further, when used for the generation of hypobromite in the pretreatment of seawater desalination, the amount of chemical replenishment can be reduced due to the decrease in the amount of chlorine agent used. Further, it is effective in suppressing the growth of bacteria related to the performance degradation of the membrane in seawater. Furthermore, it can be used for sterilization in a fish breeding tank and maintenance of hygiene by algicidation. Further, it can be used as a sterilizer for a storage water tank that refuses to add a chlorine agent. Further, it can be used as a device for decomposing dioxins in water.

[0024]

According to the present invention, a thin film of water is always present on the surface of the rotating body by rotating the photocatalyst-carrying portion while irradiating the ultraviolet light in the air. The basic form of the process of interposing water between the photocatalyst is satisfied. As a result, since the ultraviolet light only passes through the thin film of water, the intensity of the ultraviolet light before reaching the surface of the photocatalyst is less attenuated than in the method of irradiating the ultraviolet light in water. Therefore, the surface where the photocatalyst is supported and the water to be treated are sufficiently contacted, and a stable treatment effect is obtained. And especially according to the structure of Claim 2, more efficient use of a photocatalyst becomes possible. According to the third aspect of the present invention, microorganisms and turbid substances that are always attached to the surface of the photocatalyst are removed by maintaining the suspended substances in water in a dispersed state, and the photocatalyst is relatively slow. Reaction can be accelerated. Further, according to the configuration of claim 4 or claim 5, the treatment effect can be made more remarkable when used in combination with biological treatment.

[Brief description of the drawings]

FIG. 1 is a plan view of a photocatalytic reactor according to one embodiment of the present invention.

FIG. 2 is a sectional view of the device.

FIG. 3 is a perspective view of the same device as viewed obliquely from below.

[Explanation of symbols]

 1-6 Rotating disk (rotating body) 7 Biological treatment disk (rotating body) 8 Monitor disk (rotating body) 9 Rotating shaft 10-17 Water tank 18 Raw water inlet 19 Treated water outlet 20-25 Ultrasonic wave Transducer box (supersonic vibration means) 26 Motor 27 Reduction gear 28-39 Mercury lamp (ultraviolet irradiation means) 28'-39 'Mercury lamp (ultraviolet irradiation means) 40 Treated water return line 41 Switching cock

Claims (5)

[Claims] 1. A large number of water tanks which are connected to each other so that water to be treated is successively flowed to the next water tank, and a plurality of water tanks are individually installed in each of the water tanks so as to be partially immersed in the water to be treated. A rotating body that is carried, and an ultraviolet irradiation means disposed in the air adjacent to each rotating body, the treatment water in each water tank is adhered to the rotating body, carried out into the air by its rotation, and irradiated with ultraviolet light in the air. A photocatalytic reaction device characterized in that the photocatalytic reaction device is processed by performing the following. 2. The photocatalytic reactor according to claim 1, further comprising an ultraviolet irradiation means disposed in water. 3. The photocatalytic reactor according to claim 1, wherein an ultrasonic vibration unit for vibrating the water to be treated is provided in each of the water tanks. 4. The photocatalytic reaction apparatus according to claim 1, wherein a water tank having a rotating body not carrying a photocatalyst is connected upstream of the plurality of water tanks. 5. The photocatalytic reactor according to claim 1, wherein the most downstream water tank and the most upstream water tank are connected by a treated water return line.