JP2002119978A - Apparatus and method for continuously treating water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for continuously treating water containing organic matter with high efficiency. SOLUTION: A liquid to be treated is received in a reaction tank 1 and gaseous ozone is supplied to the reaction tank 1 from below by an ozone diffuser 6 and photocatalyst particles charged in the liquid to be treated are dispersed and fluidized throughout the liquid to be treated by generated ozone bubbles, the water streams due to a circulating pump 15 arranged outside the system and stirring blades 5. The photocatalyst particles fluidized in the liquid to be treated absorb the light energy of an ultraviolet lamp 4 arranged in the reaction tank to generate photocatalytic reaction and the dissolved substance in the liquid to be treated is oxidized and decomposed by radicals generated by the photocatalytic reaction. The treated liquid after oxidative decomposition is separated into the photocatalyst particles and the treated liquid by a sedimentation separation pipe 7 and only the treated liquid is discharged out of the system by a drain pump 9 through a drain pipe 8. Unreacted ozone supplied to the reaction tank is discharged out of the system from an ozone exhaust pipe 10 through a waste ozone device 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous water treatment apparatus and method for performing water treatment using a combination of a photocatalyst, ozone, and ultraviolet rays.

[0002]

2. Description of the Related Art Conventionally, a water treatment apparatus using a photocatalyst includes:
(1) A method of flowing photocatalyst particles into a processing solution (Japanese Patent Application Laid-Open No. H11-10136), (2) A photocatalyst is applied to the wall surface of a processing tank to be fixed, or a photocatalyst coated and fixed substance is inserted into the tank. (Japanese Patent Laid-Open No. 9-57279). Further, the ozone decomposition method of the water treatment apparatus using ozone and ultraviolet rays is described in (3) a method of bubbling ammonia gas with a diffuser tube (JP-A-11-19456), and (4) using a gas-liquid contact device such as an ejector. Method (Japanese Unexamined Patent Publication
309450).

The method (1) of flowing a photocatalyst into a treatment liquid has the effect of increasing the probability of contact with the photocatalyst and is effective for water treatment. However, the separation of the treatment liquid and the photocatalyst particles after treatment is difficult. It was difficult. In the method (2) of coating and immobilizing the photocatalyst, only the processing liquid in contact with the photocatalyst coating surface can be decomposed, so that the reaction efficiency is poor, and decomposition products of dissolved substances in the processing liquid adhere to the photocatalyst coating surface. However, there is a problem that the reaction efficiency is reduced.

A water treatment apparatus using a photocatalyst has a problem that the photocatalyst has a sufficient decomposition ability but the reaction speed is low, so that the processing speed of the processing solution is slow and a large amount of water is required to treat a large amount of water. was there.

In the method (3) of bubbling a gas with an air diffuser, the apparatus can have a simple structure, but it is difficult to reduce the diameter of bubbles to be formed, and it is difficult to improve the gas dissolving efficiency. It is. The method (4) using a gas-liquid contact device such as an ejector can easily improve the expected dissolving efficiency, but requires a power source such as a circulating pump and has a problem of increasing running costs. .

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a processing apparatus for continuously decomposing dissolved substances in a liquid to be treated by using a promoted oxidation method to decompose dissolved substances in the processing liquid with high efficiency. It is an object of the present invention to provide a continuous water treatment apparatus and method capable of easily separating and discharging a decomposed treatment liquid that can be produced.

[0007]

A continuous water treatment apparatus according to the present invention comprises: a tank for storing a liquid to be treated; an ultraviolet lamp installed for irradiating the liquid to be treated with ultraviolet light; It is characterized by having a circulation pump installed outside the tank system and a sedimentation separation device installed for separating photocatalyst particles.

[0008] An ozone gas is used as a gas for flowing a photocatalyst, the ozone gas is decomposed by ultraviolet irradiation, and a reaction of generated OH radicals is utilized. That is, an ultraviolet lamp having a wavelength of 189.4 nm is used, the probability of contact with the ultraviolet lamp is improved by the flow of the liquid to be treated, and water treatment is performed by using high energy generated near the lamp. Further, there is provided a continuous water treatment apparatus characterized in that a decomposition product of a photocatalyst and a dissolved substance is continuously separated by a sedimentation separation tube.

As the photocatalyst, various metals, metal compounds, metal salts and the like, or a combination thereof are known. As the photocatalyst used in the present invention, hydrophobic, hydrophilic, titanium oxide, zinc oxide, cadmium sulfide,
Iron sulfide and the like are particularly preferable, and a titanium oxide compound is particularly preferable. As the particle diameter, a particle having a small particle diameter is preferably used in order to improve the contact probability with the liquid to be treated, and a particle having a diameter of 0.1 mm or more and 5 mm or less, preferably 0.2 mm or more and 1 mm or less is used. Further, it can be used by being supported on a carrier such as silica gel.

As the gas bubbles, any gas having an oxidizing power may be used, and oxygen and ozone, preferably, ozone gas are most suitable. Ozone gas is decomposed to generate radicals, which generally oxidize substances, and are widely used as oxidizing agents. The present invention further provides the ozone gas with ultraviolet irradiation,

[0009] The oxidizing power is further increased by reacting with the photocatalyst described in [0009].

The ultraviolet light is emitted using an ultraviolet irradiation device manufactured by Sen Special Light Source Co., Ltd., and the wavelength region is 184.9 nm.
Not less than 420.0 nm, preferably 184.9 nm
Not less than 254 nm. If it is above this range, the reaction with ozone and photocatalyst is slow, and if it is below this range, the speed of the oxidation reaction is almost the same level.

By combining photocatalyst, ozone and ultraviolet light, the dissolved substances in the solution to be treated and these photocatalysts,
The contact with ozone is more reliably made dense, and the oxidation treatment is more easily performed. That is, generation of radicals on the titanium oxide surface is further promoted.

Further, gas bubbles are ejected from a diffuser tube having fine holes, and are circulated in a water flow by an internal stirring mechanism and a circulating pump provided outside the system, whereby the gas bubbles are uniformly and uniformly diffused in the liquid to be treated. . As a result, the photocatalyst and the dissolved substance come into contact with each other and ozone surely comes into contact, and the irradiation of ultraviolet rays becomes more efficient.

The solution to be treated according to the present invention is one containing an organic solvent such as underground leachate. These underground leachates are discharged from factory premises and final disposal sites for waste. It also includes clean water, sewage / manure maintenance water, and the like. In particular, it is suitable for treating wastewater containing decomposed products of animals and plants contained in soil and the like.

The treatment liquid treated according to the present invention is decomposed in a reaction vessel by a photocatalyst, ultraviolet rays and ozone. In order to carry out this decomposition continuously, it is necessary to continuously decompose with a photocatalyst. Therefore, by installing a sedimentation separation tube in the reaction vessel, the photocatalyst always stays in the reaction tank and continuous treatment of the water to be treated is possible.

That is, FIG. 1 is a schematic view of a sedimentation separation tube.
One end of the sedimentation tube is opened in the liquid to be treated in the reaction vessel shown in FIG. 1, and the other end has a discharge port outside the system by a pump through a discharge tube. The opening in the liquid to be treated preferably has a height at the lower end of the ultraviolet lamp in the reaction tank, and at least one portion of the flow path is bent. In this tube, the photocatalyst and the dissolved substance decomposed are separated due to a difference in specific gravity. The sedimentation / separation tube preferably has a shape that does not cause turbulence in the flow in the reaction tank, and is preferably a cylindrical shape in which the flow velocity at the entrance of the sedimentation / separation tube is equal to or less than the particle sedimentation velocity.

As shown in FIG. 2 (a), the opening is formed so that the pipe walls facing the opening are substantially parallel to each other, or as shown in FIG. 2 (b), it is difficult to generate turbulence and eddies near the opening. The trumpet shape can minimize the flow of the liquid to be treated.

As long as no decomposed matter accumulates in the sedimentation tube, the inner diameter of the inner tube may be gradually increased with respect to the inner diameter of the opening as shown in FIG. 2 (c).
In addition, as shown in FIG. 2D, a plurality of openings are provided in order to obtain a cross-sectional area necessary for a sedimentation separation tube as shown in FIG. And the like. In the present invention, (c) was preferable.

By using the sedimentation separation tube, the separated dissolved substance and the photocatalyst can be easily separated, and continuous operation can be performed without clogging which occurs at the time of separation by a conventional filter. As a result, the decomposition products in the liquid to be treated remain in the reaction tank, and only purified water is discharged out of the system.

The stirrer may have a shape of a stirring blade for forming a vertical circulating flow. It is preferable that the mounting position of the stirring blade is lower than the position of the opening of the sedimentation / separation tube because the influence of the flow of the liquid to be treated on the opening of the sedimentation / separation tube can be reduced.
A circulation pump is not particularly specified, but a slurry pump capable of simultaneously sending a photocatalyst is preferable. ,

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A continuous water treatment apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart of the continuous water treatment apparatus of the present invention. The continuous water treatment apparatus of the present invention includes a reaction tank 1 for storing a treatment liquid, a treatment liquid supply pipe 2 for supplying a treatment liquid, a treatment liquid supply pump 3, and an ultraviolet lamp 4 installed in the reaction tank 1. , An ozone supply pipe 5 for supplying ozone, an ozone diffuser 6, a stirring blade 5 and a circulation pump 15 for stirring and mixing the photocatalyst and the liquid to be treated, a sedimentation separation pipe 7 for separating photocatalyst particles, and discharging the treatment liquid. Treatment liquid drainage pipe 8
, A drain pump 9, an ozone exhaust pipe 10 for exhausting unreacted ozone outside the system, and an exhaust ozone treatment device 11.

Next, a method for decomposing dissolved substances in the processing solution will be described. The liquid to be treated is received in the reaction tank 1, gaseous ozone is supplied from below by the ozone diffuser 6, and injected into the liquid to be treated by the generated ozone bubbles and the water flow of the circulation pump 15 installed outside the system and the stirring blade 5. The obtained photocatalyst particles are dispersed and fluidized in the liquid to be treated. The photocatalyst particles flowing in the liquid to be treated absorb the light energy of the ultraviolet lamp 4 installed in the reaction tank and cause a photocatalytic reaction,
The dissolved substances in the liquid to be treated are oxidatively decomposed by radicals generated by the photocatalytic reaction. The treatment liquid after the oxidative decomposition is separated into the photocatalyst particles and the treatment liquid by the sedimentation separation pipe 7, and only the treatment liquid is drained out of the system by the drain pump 9 via the drain pipe 8. The unreacted ozone supplied to the reaction tank is exhausted from the ozone exhaust pipe 10 to the outside of the system via the exhaust ozone device 11.

The gaseous ozone supplied in the present apparatus not only acts to flow the photocatalyst particles in the reaction tank 1 to improve the probability of contact with the liquid to be treated, but also oxidatively decomposes due to hydroxyl radicals generated by the decomposition of ozone itself. generate. The rate of decomposition of the supplied ozone is accelerated by the light energy of the ultraviolet lamp 4 installed in the reaction tank 1, and the efficiency of oxidative decomposition is improved by increasing the generation rate of the hydroxyl radical. The use of the circulation device further improves the decomposition efficiency.

Further, by circulating the liquid to be treated together with ozone bubbles, it is possible to decompose dissolved substances with high efficiency at a wavelength of 189.4 nm generated near the surface of the ultraviolet lamp 4 with high efficiency. . The circulating flow rate is preferably set so that the displacement of the reaction tank can be changed 8 times or more and 50 times or less per hour, and preferably 15 times or more and 45 times or less. If it is below this range, the stirring efficiency is reduced, and if it is above this range, the flow of the liquid to be treated becomes remarkable, affecting the sedimentation tube.

The stirring blade has a blade shape capable of forming a vertical circulating flow, and the rotation speed and the blade diameter are preferably selected under conditions in which the number of stirring Rey nozzles is in a turbulent flow region.
When it is 0 or more and 100000 or less, preferably 30,000 or more and 70,000 or less, stirring can be performed sufficiently efficiently, and the liquid level of the liquid to be treated is small. If the stirring speed is lower than this, the stirring efficiency is reduced. On the other hand, if the rotation speed is higher than this range, the liquid level greatly varies and the sedimentation separation tube is affected.

The reaction tank used in the present apparatus is preferably made of a material that can withstand ozone and ultraviolet rays, and is preferably made of stainless steel. It is preferable that the gas-liquid contact device used for ozone diffusion also use stainless steel.

[0027]

The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to the following Examples.

In the apparatus configuration shown in FIG. 1, a liquid containing a humic substance (unnecessary black matter generated by decomposing protein) was mixed and oxidized at 25 ° C. for 15 minutes as a liquid to be treated. A photocatalyst manufactured by Ishihara Sangyo Co., Ltd.
0 g was added by weight. The processing speed of extracting from the sedimentation separation tube was 300 cc / min. The chromaticity was measured according to the method of JIS K0101. The operating conditions are summarized below. -Target liquid: waste liquid containing humic substances-Reaction tank capacity: 3.5 L-Photocatalyst diameter: 0.5 mm-Ultraviolet lamp: 40 W-Ozone air volume: 1 L / min-Ozone concentration: 35 g / Nm3-Diffusion tube diameter: 40 Micron ・ Flow rate: 300 cc / min ・ Circulation flow rate: 2 L / min ・ Rotation speed of stirring blade: 450 rpm Table 1 shows some of the experimental results. The evaluation was based on chromaticity due to humic substance decomposition. As a comparative example, hydrogen peroxide and ultraviolet light alone were used instead of ozone. That is, a photocatalyst,
The ultraviolet irradiation was performed under the same conditions as in the example, and only ozone was used as a hydrogen peroxide solution. A spare port was attached to the ozone diffuser in FIG. 1 and hydrogen peroxide solution was supplied from here. Table 1 shows the results.

[0029]

[Table 1]

Table 1 From the above results, the decomposition of humic substances in this apparatus was confirmed by the change in chromaticity over time. That is, by using this processing apparatus, the chromaticity was smaller than that of the comparative example, and the transparency was confirmed.

[0031]

According to the continuous water treatment apparatus of the present invention,
Continuous water treatment using photocatalyst particles can be performed, and the dissolved substances contained in the liquid to be treated can be oxidatively decomposed with high efficiency. The present invention is very useful industrially.

[Brief description of the drawings]

FIG. 1 is an example of a flow diagram of a continuous water treatment apparatus of the present invention.

FIG. 2 is a schematic view showing a specific example of a sedimentation separation tube used in the continuous water treatment apparatus of the present invention.

[Explanation of symbols]

 1. Reaction tank 2. 2. Liquid supply pipe to be treated Liquid supply pump 4 UV lamp 5. 5. Circulation line (including liquid to be treated and ozone) Ozone diffuser 7. Settling separation tube 8. 8. Treatment liquid drain pipe Treatment liquid drainage pump 10. Ozone exhaust pipe 11. Waste ozone treatment device 12. Stirrer 13. Ozone supply pipe 14. Circulation line 15. Circulation pump 31. Separation plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/78 C02F 1/78 F term (Reference) 4D037 AA11 AB05 BA18 BB09 CA11 4D050 AA13 AB03 BB02 BC06 BC07 BC09 BD06 CA07 4G069 AA02 AA03 BA02A BA04A BA04B BA48A BB04A BB09A BC35A BC36A BC66A CA05 CA07 CA10 DA08 EA02Y EB18Y

Claims (8)

[Claims] In a system for decomposing dissolved substances in a liquid to be treated by using gas bubbles, ultraviolet rays and a photocatalyst, a water stream circulating from outside the reaction tank system while continuously supplying a new liquid to be treated to the system. A continuous water treatment in which the photocatalyst is flowed and stirred at the same time, and at the same time, while the liquid to be treated is stirred by a stirrer or the like, the treatment liquid in which dissolved substances in the liquid to be treated have been decomposed is discharged out of the system by a sedimentation tube apparatus. 2. A sedimentation separation tube for continuously separating a photocatalyst and a processing liquid obtained by decomposing a dissolved substance in a liquid to be processed according to claim 1, wherein a sedimentation separation tube is provided in the system, and the liquid to be processed is subjected to the reaction tank diameter. By circulating from the outside and bringing the liquid to be treated into contact with the photocatalyst and the bubble gas while stirring the liquid to be treated, the sedimentation tube forms a flow path through which the liquid to be treated passes while causing the photocatalyst to settle into the system. The opening for introducing the liquid to be treated in the dissolved substance dissolved in the liquid is directed to the downstream direction of the circulating flow due to the stirring of the liquid to be treated, and that at least one portion of the flow path is bent. Features continuous water treatment equipment. 3. A reaction tank for storing a liquid to be treated, an ultraviolet lamp installed to irradiate the liquid to be treated with ultraviolet light, a stirring mechanism, a circulation pump installed outside the reaction tank system, a stirring mechanism and circulation. The continuous water treatment apparatus according to any one of claims 1 to 2, wherein the photocatalyst particles are agitated by the water stream to increase the rate of contact with gas bubbles generated from the air diffuser. 4. The continuous water treatment apparatus according to claim 1, wherein the photocatalyst is titanium dioxide. 5. The continuous water treatment apparatus according to claim 1, wherein the gas bubbles are ozone. 6. The continuous water treatment apparatus according to claim 1, wherein a photocatalyst, ultraviolet light, and ozone are combined. 7. The continuous water treatment apparatus according to claim 1, wherein the liquid to be treated is a waste liquid containing an organic substance. 8. A continuous water treatment method using the continuous water treatment device according to claim 1.