Water purifier

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a water purification device, and more particularly to a water purification device utilizing the photocatalytic function of titanium oxide.

【0002】

[Conventional technology]

Some domestic wastewater, irrigation wastewater or industrial wastewater contains a large amount of substances such as nitrogen and phosphorus, which cause eutrophication in lakes, rivers and sea bays. When algae such as plankton, picoplankton, blue-green algae, and red tide grow due to eutrophication, the water becomes musty due to the odorant 2-methylisoborneol produced by holmidium, which is a type of plankton, and osilatoria. The so-called algal blooms, which form the so-called algal blooms, freshwater blue tides and freshwater red tides, and the so-called red tides, which color seawater reddish brown, pink, and brown It causes great damage to algae, such as spoiling the landscape, digesting oxygen in water and causing oxygen deficiency, and the generated plankton adhering to the gills of fish and causing breathing difficulty. In addition, the grown algae interfere with water purification treatment, such as clogging the filtration ponds and filtration screens of water purification plants and dams. In addition, domestic wastewater, irrigation wastewater, or industrial wastewater includes fungi such as molds, fungi such as actinomycetes, and bacteria such as Escherichia coli, which may grow in lakes, rivers, sea bays, and the like. Bacteria include infectious diseases such as typhoid and diarrhea, sulfur bacteria that promote corrosion, iron bacteria, sulfate-reducing bacteria, slime-producing bacteria and fungi, and actinomycetes that smell water. Not a few, various damages have occurred. In particular, in ponds and aquaculture tanks where fish, shellfish, crabs, shrimp, frogs, etc. are cultivated, and in aquaculture areas such as ornamental ponds and aquaculture tanks where fish are bred, water is polluted by excrement and spoilage of food. , The foul odor is emitted, and the damage caused by bacteria and fungi from excrement and putrefactive food is frequently occurring. In addition to the above, domestic wastewater, irrigation wastewater, or industrial wastewater may contain oxygen-requiring substances such as detergents and oils, organic halogen compounds contained in wastewater from semiconductor manufacturing plants, and harmful substances such as pesticides. , Pollution of lakes, rivers and sea bays, and may cause damage to living organisms.

【0003】

In order to kill or sterilize the grown algae, fungi, and bacteria, for example, a method of injecting chlorine, ozone, copper sulfate, or the like, or treating by irradiation with ultraviolet rays is adopted. Further, in order to remove odorous substances and coloring substances generated by algae, fungi and bacteria, for example, a method of adsorbing them on activated carbon or the like is adopted. In particular, water purification plants that draw water from highly polluted lakes and rivers are trying to improve water quality by administering a large amount of activated carbon. On the other hand, when titanium oxide is irradiated with light having an energy equal to or higher than the band gap, electrons are generated in the conduction band and holes are generated in the valence band by photoexcitation. A method of sterilizing, decomposing or deodorizing organic substances by utilizing the strong oxidizing power of holes has been proposed.

【0004】

[Problems to be Solved by the Invention]

Although the above-mentioned method of treating with chlorine or ozone can reduce algae, fungi, and bacteria, the effect is not sufficient, the treatment time is long, and the chemicals used or the chemicals are produced. There is a problem that the compound remains in water. The activated carbon adsorption method can reduce odor and coloring, but does not kill algae, fungi, and bacteria. The titanium oxide photocatalyst method can be expected to have a wide range of water purification effects such as killing algae and fungi, decomposing dead algae, fungi and dissolved organic substances, oxidizing ammonia, and deodorizing, but the method of irradiating light In order to improve the utilization efficiency and obtain a high photocatalytic function, the treatment is usually carried out in a state where ultrafine titanium oxide is individually dispersed. Therefore, it is necessary to separate and recover titanium oxide from the treatment system, but this separation and recovery operation is extremely difficult, and it is difficult to put it into practical use.

【0005】

[Means for solving problems]

It can be improved, (7) in particular, algae, fungi, and bacteria are easy to grow, (a) water in water storage tanks and other water storage tanks, water supply / hot water supply equipment using solar energy, and heating / cooling equipment. Water, bath water, pool water, tap water, drinking water and other domestic water, industrial water, agricultural water or raw water used for these waters, (b) aquatic organism breeding area water, and (c) Domestic effluent, manufacturing, agriculture, fisheries and other industrial effluents, sewage treatment plant effluents, pesticide-contaminated effluents from golf courses, etc. , I found that it is most suitable for purifying contaminated water such as viewing ponds. Based on these findings, further research was conducted to complete the present invention.

【0006】

That is, the present invention includes a photocatalyst made of titanium oxide, a fixed-bed photocatalyst reactor in which the photocatalyst is arranged, a means for sending water to the reactor, and a means for irradiating the photocatalyst with light containing ultraviolet rays. It is a water purification device and a purification method characterized by cascading control of a water flow.

【0007】

The present invention is to provide a simple and efficient device and method for purifying water.

【0008】

In the present invention, the photocatalytic reactor preferably has a fixed bed, and the reactor such as a fluidized bed requires a separation operation of titanium oxide, which is not desirable. As the fixed bed photocatalytic reactor, for example, a fixed layer reactor, a radial flow reactor, a parallel passage reactor, a monolithic reactor, a thin layer reactor, a tube wall reactor and the like are used. A photocatalyst made of titanium oxide is placed in the fixed bed photocatalyst reactor. Water purification treatment is to connect the fixed bed reactors in a series, divide the inside of the fixed bed reactor into multiple stages, and feed back a part of the treated water of each stage or the whole system to the previous stage. More preferred on. In this case, a molded product of titanium oxide, which is a photocatalyst, can be arranged inside the fixed bed reactor, or titanium oxide can be arranged by adhering to a filler, a wall surface inside the reactor, a wire mesh, or the like. In particular, it is preferable that titanium oxide adheres to the surface of the filler. As the filler, various materials such as an inorganic material, a metal material, and an organic material can be used, and minerals such as stone can also be used. Desirable materials include various glasses such as light-transmitting quartz and quartz glass, soda lime glass, lead glass, aluminoborosilicate glass, borosilicate glass, aluminosilicate glass, and various plastics, which are irradiated. It is desirable to use a material that allows 50% or more, preferably 70% or more of the light component to be transmitted. When such a light-transmitting filler is used, the irradiation light can be used more efficiently, and the photocatalytic function can be more exerted. The filler is preferably one suitable for cascade control of the water flow. Cascade control of water flow is to maintain a uniform and constant residence time on the widest possible contact surface when contacting treated water while irradiating the surface of the photocatalyst in the fixed bed photocatalyst reactor with light. Therefore, the flow of water is controlled in multiple stages, more preferably, to feed back a part of the treated water. Fillers suitable for water cascade control include irregular shapes, spheres, and plates, as well as Raschig rings, lessing rings, Beruru saddles, interlock saddles, and te. Various shapes such as a larlet and a pole ring can be mentioned. The size of the filler is preferably about 100 μm to 5 cm in diameter, preferably 0.1 to 3 cm, and more preferably 0.2 to 2 cm. In the present invention, the thickness of the photocatalyst is set to 50 mm or less, preferably 40 mm or less, more preferably 30 mm or less in the direction of entry of the irradiated light so that the entire photocatalyst is irradiated with light. In order to keep the thickness of the photocatalyst in the above range, the number of light sources to be irradiated with light can be increased, or the light sources can be adjusted by charging the photocatalyst in a fixed bed photocatalytic reactor.

【0009】

In the present invention, the titanium oxide used as a photocatalyst includes, in addition to titanium oxide, those generally called titanium hydroxide-containing titanium oxide, hydrated titanium oxide, metatitanic acid, orthotitanium acid, titanium hydroxide and the like, and the crystal form thereof. Does not matter. The titanium oxide can be obtained by various known methods. For example, a method of hydrolyzing a titanium compound such as titanyl sulfate, titanium chloride, or an organic titanium compound in the presence of nucleating seeds as needed, and in the presence of nucleating seeds as needed. , A method of adding an alkali to a titanium compound such as titanium chloride or an organic titanium compound to neutralize it, a method of vapor phase oxidizing titanium chloride or an organic titanium compound, or a method of firing titanium oxide obtained by the above method. Can be mentioned. In particular, titanium oxide obtained by the above method is preferable because it has a high photocatalytic function. In order to improve the photocatalytic function of titanium oxide, the surface of the titanium oxide may be coated with a metal such as platinum, gold, silver, copper, palladium, rhodium or ruthenium, or a metal oxide such as ruthenium oxide or nickel oxide. .. The titanium oxide thus obtained is suspended in a solvent such as water, alcohol, or toluene. Various dispersants and binders may be added as needed. The obtained suspension is coated with, for example, an impregnation method, a dip coating method, a spinner coating method, a blade coating method, a roller coating method, a wire bar coating method, a reverse roll coating method, or a spray coating method. It is applied or sprayed on the surface of a filler, a wall surface in a reactor, a wire mesh, etc., and then dried to attach titanium oxide. In particular, it is preferable that the titanium oxide obtained by the above method is highly dispersed in a solvent to form a titanium oxide sol, and the titanium oxide sol is applied or sprayed. The attached titanium oxide may be fired if necessary, and by this firing, the titanium oxide can be firmly adhered to the surface of the filler, the wall surface in the reactor, the wire mesh, or the like. The firing is 100 ° C or higher, preferably 200 to It is suitable to bake at a temperature of 800 ° C, particularly preferably 300-800 ° C. Further, the above-mentioned titanyl sulfate, titanium chloride, organic titanium compound and the like are hydrolyzed or neutralized in the presence of the filler, titanium oxide is deposited and adhered to the surface of the filler, and then dried, and further necessary. Titanium oxide can also be supported on the filler by firing according to the above.

【0010】

The present invention comprises means for feeding the water to be treated into the fixed bed photocatalytic reactor under pressure, reduced pressure or atmospheric pressure. Usually, it is preferable to send the liquid by a pump or gravity, and as a means for circulating in the device, a method by a pump or a natural fall by gravity is preferable. Further, a means for irradiating a photocatalyst made of titanium oxide in a fixed bed photocatalyst reactor with light containing ultraviolet rays is provided, and water is purified in the fixed bed photocatalyst reactor in the presence of light containing ultraviolet rays. .. Examples of the light containing ultraviolet rays include light such as sunlight, fluorescent lamps, black lights, halogen lamps, xenon flash lamps, germicidal lamps, mercury lamps, and incandescent lamps. In particular, light containing near-ultraviolet rays of 300 to 400 nm is preferable. The irradiation amount and irradiation time of light containing ultraviolet rays can be appropriately set depending on the degree of pollution of the water to be treated, the content of ultraviolet rays, and the like. The fixed bed photocatalytic reactor used in the present invention may have the shape of the reactors used in Examples 1 to 6 described later, may be appropriately improved, or two or more of these reactors may be connected and used. good.

【0011】

The purification device of the present invention may further include means for feedback control. In the present invention, the feedback control measures the concentration of the object to be treated contained in the water discharged from the fixed bed photocatalytic reactor, feeds back the result to a controller such as a liquid feeding means or a light source, and the controller gives the result. This is a method of determining the next operation by comparing the target and the measurement result. If the measurement result has a concentration higher than the target, an operation is performed to bring the concentration closer to the target by lowering the liquid feed amount or increasing the light irradiation amount. These operations can be controlled using a computer.

【0012】

Using the purification device of the present invention, water is sent to a fixed-bed photocatalytic reactor using titanium oxide as a photocatalyst, and the titanium oxide is irradiated with light containing ultraviolet rays to be irradiated in the fixed-bed photocatalytic reactor. Can purify water.

【0013】

[Example]

Examples of the present invention are shown below, but the present invention is not limited thereto. Example 1 Acidic titania sol (manufactured by Ishihara Sangyo Co., Ltd., CS-C) obtained by heating and hydrolyzing titanyl sulfate is TiO.₂It was diluted with water to 40 g / l as a standard. Next, the diluted solution was impregnated with a glass ball (1 cm in diameter) filler having a spherical shape and a light transmittance of 85% for 2 hours, and then ammonia water was added. It was neutralized to pH 7 and titanium oxide was attached to the surface of the filler. Subsequently, the filler to which titanium oxide was attached was separated by filtration, dried, and then calcined at a temperature of 600 ° C. in the air for 2 hours. Then, the fired filler was washed with water and dried to obtain a photocatalyst A. The amount of titanium oxide supported by the photocatalyst A was 1.6 parts by weight with respect to 100 parts by weight of the filler. As shown in FIG. 1, 300 g of this photocatalyst A was placed on the floor of the container so as to have a thickness of a packed layer of 30 mm in the direction of entry of the irradiated light, and used as a fixed bed photocatalyst reactor 1. A 20 W white fluorescent lamp 2 was installed at a distance of 15 cm above the fixed-bed photocatalytic reactor, and a pump 3 for sending water to the fixed-bed photocatalytic reactor was provided as the purification device of the present invention. This purification device was placed on the aquarium 4 (50 liters of water) in which 20 goldfish were bred, the water in the aquarium was sent to the purification device, the water was fed back, and the occurrence of phytoplankton and water contamination were investigated. .. Water flow was cascade controlled. The water flow rate of the pump was set to 10 liters / minute. This aquarium was fed 0.5 g of food twice daily. As a result, no phytoplankton was found in this aquarium even after 2 weeks. In addition, when the number of viable bacteria and the number of coliform bacteria in water 4 weeks after the start of the test were examined by the following method, the number of viable bacteria was 6620 / ml and the number of coliform bacteria was 3640 / ml. Compared to Example 1, the growth of fungi and bacteria could be suppressed. Furthermore, as shown in Table 1, the change in water transmittance was smaller than that in Comparative Example 1, and there was almost no water contamination.

【0014】

<Method of measuring the number of viable bacteria and coliform bacteria> Dilute the collected water 10-fold and 100-fold with sterile water, dispense 1 ml each into 5 sterilized petri dishes, then add 10 ml of medium, stir, and then. The cells were cultured overnight at 37 ° C, and the number of colonies was counted the next day. <Medium used> Viable cell count: Brain Heart Infusion Bouillon (manufactured by Nissui) Coliform bacteria: Dezoxycholate medium (manufactured by Nissui) [0015]

Comparative example 1 50 liters of water was placed in the aquarium, 20 goldfish were bred, and the occurrence of phytoplankton and water contamination were observed in the same manner as in Example 1. As a result, after two weeks, the aquarium was contaminated with a large number of phytoplankton so that the other side of the aquarium could not be seen. In addition, when the viable cell count and coliform bacteria count in water 4 weeks after the start of the test were examined by the same method as in Example 1, the viable cell count was 8000 cells / ml and the coliform bacteria count was 4700 cells / ml. It was. Furthermore, as shown in Table 1, the change in water transmittance was large and the water became dirty.

【0016】

[table 1]

<img file="JPH0847687A_D0001.tif" />【0017】

Example 2 TiO obtained by heating and hydrolyzing titanyl sulfate₂A standard 400 g / l acidic titania sol (manufactured by Ishihara Sangyo Co., Ltd., CS-C) is filled with a spherical, translucent glass ball (1 cm in diameter) filler with a light transmittance of 65%. After impregnation for a day, the filler was separated by filtration and dried to allow titanium oxide to adhere to the surface of the filler. Subsequently, the filler to which titanium oxide was attached was calcined in the air at a temperature of 600 ° C. for 2 hours. Then, the fired filler was washed with water and dried to obtain a photocatalyst B. The amount of titanium oxide supported by the photocatalyst B was 3.6 parts by weight with respect to 100 parts by weight of the filler. 300 g of this photocatalyst B was placed on the floor of the container so as to have a thickness of a packed layer of 50 mm in the direction of entry of the irradiated light, and used as a fixed bed photocatalyst reactor. A black light was installed above the fixed-bed photocatalytic reactor, and a pump for sending water to the fixed-bed photocatalytic reactor was provided to obtain the purification device of the present invention. In this purification device, the intensity of ultraviolet light is 1.55 mW / cm on the surface of the filler.²The water flow rate of the pump was set to 10 liters / minute. The above-mentioned purification device is placed next to a water tank containing 50 liters of water from Lake Biwa, which is used for domestic water, and the water in the water tank is sent to the purification device to feed back the water, which is a component of musty odor. -The change in the concentration of methylisoborneol was investigated. Water flow was cascade controlled. The results are shown in Table 2. Most humans do not feel a musty odor when the concentration of 2-methylisoborneol is 10 ppt or less. When the domestic wastewater was treated in the same manner using the above-mentioned purification device, the organic matter contained in the domestic wastewater was decomposed and the COD value decreased.

【0018】

[Table 2]

<img file="JPH0847687A_D0002.tif" />【0019】

Example 3 As shown in FIG. 2, 1 kg of the photocatalyst B of Example 2 was filled in a donut-shaped cylindrical container to prepare a fixed bed photocatalyst reactor 5. The thickness of the packed bed of the photocatalyst was 50 mm in the direction of entry of the irradiated light. The fixed-bed photocatalytic reactor is provided with a black light 6 inside, a mirror on the inner wall surface, and a pump 7 for sending water to the fixed-bed photocatalytic reactor to purify the present invention. It was a device. In this purification device, the intensity of ultraviolet light is 1.55 mW / cm on the inner surface of the fixed bed photocatalytic reactor.²The water flow rate of the pump was set to 10 liters / minute, and a part of the discharged water was fed back. Water flow was cascade controlled. The same water from Lake Biwa used in Example 2 was sent from above this purification device, and the concentration of 2-methylisoborneol after passing through the purification device was examined. As a result, the concentration of 2-methylisoborneol was 10 ppt or less.

【0020】

Example 4 As shown in FIG. 3, the photocatalyst A of Example 1 was arranged in a container divided into multiple stages so as to have a packing layer thickness of 50 mm, and used as a fixed bed photocatalyst reactor 8. A 10 W black light 9 was installed at a distance of 15 cm above the fixed-bed photocatalytic reactor, and a pump 10 for sending water to the fixed-bed photocatalytic reactor was further provided to obtain the purification device of the present invention. This device was placed on the aquarium 11 (50 liters of water) in which 20 goldfish were bred, the water in the aquarium was sent to the purification device, the water was fed back, and the change in COD was investigated. The water flow rate of the pump was set to 10 liters / minute. This aquarium was fed 0.5 g of food twice daily. Water flow was cascade controlled. As a result, as shown in Table 3, it was confirmed that the COD was suppressed to be lower than that of Comparative Example 2 below, and the organic matter was efficiently decomposed.

【0021】

Example 5 Acidic titania sol (manufactured by Ishihara Sangyo, CS-C) obtained by hydrolyzing titanyl sulfate is TiO₂It was diluted with water to 40 g / l as a standard. Next, the diluted solution was impregnated with a glass ball (0.5 cm in diameter) filler having a spherical shape and a light transmittance of 60% for 2 hours, and then ammonia water was added. It was neutralized to pH 7 and titanium oxide was supported on the surface of the filler. Subsequently, the filler carrying titanium oxide was separated by filtration, dried, and then calcined at a temperature of 600 ° C. in the air for 2 hours. Then, the fired filler was washed with water and dried to obtain a photocatalyst E. The amount of titanium oxide supported by this photocatalyst E was 2.5 parts by weight with respect to 100 parts by weight of the filler. The photocatalyst E and the photocatalyst A of Example 1 were mixed in the same volume and arranged in the container used in Example 4 so as to have a packed layer thickness of 50 mm to prepare a fixed bed photocatalyst reactor. A 10 W black light was installed at a distance of 15 cm above the fixed-bed photocatalytic reactor, and a pump for sending water to the fixed-bed photocatalytic reactor was provided to obtain the purification device of the present invention. This device was placed on a water tank (50 liters of water) in which 20 goldfish were bred, and the water in the water tank was sent to a purification device, the water was fed back, and changes in COD were investigated. The water flow rate of the pump was set to 10 liters / minute. This aquarium was fed 0.5 g of food twice daily. Water flow was cascade controlled. As a result, as shown in Table 3, it was confirmed that the COD was suppressed to be lower than that of Comparative Example 2 below, and the organic matter was efficiently decomposed.

【0022】

Comparative example 2 The floor of the container used in Example 1 was filled with commercially available plastic filtered cotton to a thickness of 50 mm. A 10W black light was installed at a distance of 15cm above this container, and a pump for sending water to this container was installed as a purification device for comparison. This device was placed on a water tank (50 liters of water) in which 20 goldfish were bred, and the water in the water tank was sent to a purification device, the water was fed back, and changes in COD were investigated. The water flow rate of the pump was set to 10 liters / minute. This aquarium was fed 0.5 g of food twice daily. As a result, as shown in Table 3, it was confirmed that COD increased in a short period of time and organic matter accumulated.

【0023】

[Table 3]

<img file="JPH0847687A_D0003.tif" />【0024】

Example 6 The purification device described in Example 3 is provided with a means for feedback control. That is, the concentration of 2-methylisoborneol contained in the water discharged from this purification device is measured, and based on the result, the amount of liquid sent by the pump is in the range of 5 to 20 liters / minute, and the output amount of the light source is adjusted. The intensity of ultraviolet light is 1 to 4 mW / cm²It was controlled to be. As a result, the concentration of 2-methylisoborneol could be controlled to 5 ppt or less.

【0025】

[Effect of the invention]

The present invention includes a photocatalyst made of titanium oxide, a fixed-bed photocatalyst reactor in which the photocatalyst is arranged, means for sending water to the reactor, and means for irradiating the titanium oxide with light containing ultraviolet rays. In addition, it is a water purification device that cascade-controls the water flow, and the photocatalytic function of titanium oxide kills harmful organisms such as algae, fungi, and bacteria contained in the water, decomposes harmful substances, and deodorizes and decolorizes. It is extremely useful not only for industrial use but also as a water purification device for general households because it can be performed quickly and efficiently. In particular, pathogens such as Ogusare disease and Hakuhan disease that occur in the breeding area of fish can be sterilized, and the death of fish can be prevented. Since the purification device of the present invention uses titanium oxide, it is highly safe, has a wide range of harmful substances to which it can be applied, and does not pollute the environment even if it is discarded, so that it is extremely useful in industry. Further, in the purification device of the present invention, in order to cascade control the water flow, a filler carrying titanium oxide, which is a photocatalyst, is loaded into the fixed bed reactor, or the inside of the fixed bed reactor is divided into multiple stages. Alternatively, by connecting individual fixed-bed reactors in multiple stages and, more preferably, feeding back the treated water to the previous stage, the contact between water and light with respect to the photocatalyst is improved, and the photocatalyst of titanium oxide is used. In addition to further enhancing the function, there is no outflow of titanium oxide, and the photocatalyst can be easily replaced. Further, the present invention includes a photocatalyst made of titanium oxide, a fixed-bed photocatalyst reactor in which the photocatalyst is arranged, a means for sending water to the reactor, and a means for irradiating the photocatalyst with light containing ultraviolet rays. It is a water purification device that controls the water flow in cascade and controls the feedback, and can accurately control the concentration of the object to be treated. Further, in the present invention, water is sent to a fixed bed photocatalytic reactor using titanium oxide as a photocatalyst, and the titanium oxide is irradiated with light containing ultraviolet rays to purify the water in the fixed bed photocatalytic reactor. It is a method of purifying water to be used, and is used for seawater and water in bays, lakes, dams, rivers, domestic water, industrial water, agricultural water, etc., or the source used for these waters.

[Simple explanation of drawings]

[Figure 1]

It is a conceptual diagram of the purification apparatus of this invention in Example 1. FIG.

[Figure 2]

It is a conceptual diagram of the purification apparatus of this invention in Example 3. FIG.

[Fig. 3]

It is a conceptual diagram of the purification apparatus of this invention in Example 4. FIG.

[Explanation of symbols]

A, B ... Photocatalyst 1, 5, 8 ... Fixed bed photocatalytic reactor 2 White fluorescent lamp 3, 7, 10 Liquid transfer pump 4, 11 ... Aquarium 6, 9, ... Black light Direction of water flow