JP5263898B2 - Wastewater treatment equipment - Google Patents

Description

  The present invention relates to a wastewater treatment apparatus for decomposing organic substances contained in wastewater.

  In recent years, recycling of wastewater has been promoted, and organic substances contained in wastewater by biological treatment have been decomposed for recycling. However, the wastewater treatment by the above-described organisms cannot deny the enlargement of the treatment facility and the lengthening of the treatment time. Therefore, there is a need for a wastewater treatment apparatus that can effectively decompose and purify organic substances contained in wastewater.

  As a wastewater treatment method, for example, a wet oxidation treatment method is disclosed in which oxygen is added to organic matter-containing wastewater, oxidized in a high-temperature / high-pressure vessel, and decomposed into water and carbon dioxide (Patent Document 1).

JP 2008-149232 A

  However, in the method described in Patent Document 1, since oxygen gas with high oxygen purity is used, care must be taken in handling oxygen gas. In addition, special equipment such as a pressure-resistant and heat-resistant container is required, which is expensive and not practical. Furthermore, the treated waste water is currently drained as factory waste water because of insufficient decomposition of organic matter, and it is almost never reused as factory washing water.

  The present invention has been made in view of the above-described problems, and has a simple configuration and can effectively decompose organic substances present in the waste water and maintain the decomposition ability for a long period of time. An object is to provide a processing apparatus.

  In order to achieve the above object, as a result of intensive studies, the present inventors have reacted with metal ions in wastewater when the organic matter is decomposed by irradiating ultraviolet rays in wastewater containing organic matter and metal ions. Before generating organic hydroxide in the wastewater by irradiating the photocatalyst with ultraviolet rays based on that knowledge. It was found that wastewater treatment capacity can be maintained for a long time by generating metal hydroxide in wastewater and removing it. That is, the present invention includes a first reaction tank having a first ultraviolet irradiation means for irradiating waste water containing at least organic substances and metal ions with ultraviolet light, and a metal hydroxide generated in the waste water of the first reaction tank. A wastewater treatment apparatus comprising: a metal hydroxide removing means for removing water; a photocatalyst having titanium oxide on the surface; and a second reaction tank having at least a second ultraviolet irradiation means for irradiating the photocatalyst with ultraviolet light. The waste water from the first reaction tank is supplied to the second reaction tank after the waste water from the first reaction tank is treated by the first ultraviolet irradiation means and the metal hydroxide removal means. This is a wastewater treatment apparatus.

  As described above, according to the present invention, it is possible to provide a wastewater treatment apparatus that can effectively decompose organic substances existing in wastewater and maintain the decomposition ability for a long period of time with a simple configuration.

It is a conceptual sectional view of the waste water treatment equipment concerning an embodiment. It is a conceptual diagram of a photocatalyst cartridge. It is process drawing which concerns on embodiment. It is a conceptual sectional view of the waste water treatment equipment used in comparative example 2.

  Next, an embodiment of the waste water treatment apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual cross-sectional view of a wastewater treatment apparatus according to the present embodiment. The wastewater treatment apparatus 1 collects the first reaction tank 3 capable of irradiating the wastewater containing organic matter and metal ions with ultraviolet rays, and the metal hydroxide generated in the wastewater of the first reaction tank 3. A filter 5 to be removed, a photocatalyst having titanium oxide on its surface, a second reaction tank 7 for irradiating the waste water with ultraviolet light, and a flow passage 12 for communicating the first reaction tank 3 and the second reaction tank 7. Yes.

  The first reaction tank 3 includes a flow tank 20 formed in a rectangular parallelepiped shape, a circulation path 10 that communicates the upstream side (left side in FIG. 1) of the bottom surface of the fluid tank 20 and the downstream side (right side of FIG. 1) of the bottom surface, 11, and the filter 5 is provided between the flow passages 10 and 11. A drainage inlet 16 is formed on the upstream side surface of the fluid tank 20, and a drainage outlet 17 connected to the upstream side of the flow passage 12 is formed on the downstream side surface. The waste water flows from the inlet 16 to the drain outlet 17. Further, the wastewater in the fluid tank 20 is circulated between the fluid tank 20 and the filter 5 through the circulation paths 10 and 11 by a pump (not shown), that is, the waste water is fluidized from the fluid tank 20 to the circulation path 10 to the filter 5. → circulation path 11 → circulated with fluid tank 20 Further, an ultraviolet lamp 18 for irradiating the waste water in the fluid tank 20 with ultraviolet rays and an air injection part 22 for injecting oxygen into the waste water are arranged in the fluid tank 20.

  The ultraviolet lamps 18 are arranged in five rows in the vertical direction, seven rows in the flow direction, and a total of 35 in such a way that the longitudinal direction is perpendicular to the flow direction and parallel to the bottom surface of the flow tank 20. . A cover member formed in a columnar shape is provided on the outer surface of the ultraviolet lamp 18, and the cover member is made of a material that transmits not only 250 to 260 nm but also a peak wavelength of 180 to 190 nm. An example of the material of the cover member is synthetic quartz. A general low-pressure mercury lamp originally has two wavelengths of 185 nm and 254 nm. However, since glass, which is a material of a normal cover member, does not transmit short-wave ultraviolet light, it irradiates only a wavelength of 254 nm. In the wastewater treatment apparatus according to the present embodiment, the ultraviolet lamp 18 can irradiate ultraviolet rays having peak wavelengths of 180 to 190 nm and 250 to 260 nm by making the material of the cover member special as described above. Yes. The ultraviolet rays irradiated from the ultraviolet irradiation lamp 18 have a peak wavelength at 180 to 190 nm, preferably 185 nm, and a peak wavelength at 250 to 260 nm, preferably 254 nm. In the present embodiment, the cover member of the ultraviolet irradiation lamp 18 is formed in a cylindrical shape, but is not limited thereto. The number of ultraviolet irradiation lamps 18 is determined according to the amount of organic matter contained in the waste water.

  The air injection part 22 is disposed between the ultraviolet lamps of the ultraviolet lamp 18 closest to the bottom surface of the fluid tank 20 and is configured to inject air over almost the entire area of the ultraviolet lamp 18 in the longitudinal direction. The air injection part 22 is a device that can be bubbled from the lower part of the first reaction tank 3 by an aeration method. The air supply amount is preferably 200 to 500 L / min, more preferably 350 L / min, with respect to the wastewater 200 L / min. The amount of dissolved oxygen in the bubbled water is preferably 50 to 100% in terms of saturation. Further, air may be supplied together with or instead of the air injection unit 22 using a microbubble generator. In general, there are a pressure dissolution method, an ejector method, a cavitation method, and a swivel method as a method for generating microbubbles, but a pressure dissolution method and an ejector method are preferable as methods for generating microbubbles. Since the characteristics of microbubbles depend on the diameter and amount of bubbles generated, a pressure-melting generation method that can generate relatively large amounts of fine bubbles is particularly preferable. The diameter of the generated microbubbles is preferably 30 μm or less. The amount of dissolved oxygen in the water in which the microbubbles are generated by the microbubble generator is preferably 80 to 150% in terms of saturation. Oxygen above the saturation amount of dissolved oxygen can be dissolved by the self-pressurizing effect of the microbubbles.

  In the wastewater treatment apparatus according to the present embodiment, the filter 5 has a function of collecting metal oxides in the wastewater passing therethrough. As such a filter 5, for example, as an absorption filtration method The prefilter, sand filtration, biological filtration, activated carbon, and separation membrane used can be used, but it is preferable to use a prefilter. The shape of the prefilter is preferably a pleated type, and the opening size is preferably 0.2 to 2 μm.

  The second reaction tank 7 includes a fluid tank 28 formed in a rectangular parallelepiped shape, and a circulation path 32 that communicates the upstream side of the bottom surface of the fluid tank 28 and the downstream side of the bottom surface. A drainage inlet 25 connected to the downstream side of the communication passage 12 is formed on the upstream side surface of the fluid tank 28, and a drainage outlet 26 is formed on the downstream side surface. The drainage is configured to flow from the inlet 25 to the drainage outlet 26. In the fluid tank 28, a flat plate having a photocatalyst and an ultraviolet lamp 19 for irradiating the waste water in the fluid tank 28 with ultraviolet rays, an air injection part 23 for injecting oxygen into the waste water, and a photocatalyst having titanium oxide on the surface thereof. A photocatalyst cartridge 30 is disposed.

  The ultraviolet lamps 19 irradiate the photocatalyst cartridge 30 with light, 5 in the vertical direction, 3 in the flow direction, and 15 in total, the longitudinal direction of which is perpendicular to the flow direction and the flow tank 28 It arrange | positions so that it may become parallel with a bottom face. As the ultraviolet lamp 19, the same one as the ultraviolet lamp 18 used in the first reaction tank 3 can be used in this embodiment. The air injection part 23 is arranged between the ultraviolet lamps of the ultraviolet lamp 19 closest to the bottom surface of the fluid tank 28 and is configured to inject air over almost the entire area of the ultraviolet lamp 19 in the longitudinal direction. As the air injection part 23, the same one as the air injection part 22 used in the first reaction tank 3 can be used. A pair of flat photocatalyst cartridges 30 are arranged so that their surfaces intersect perpendicularly to the flow direction of drainage, and the ultraviolet lamps 19 are sandwiched therebetween, and surfaces perpendicular to the flow direction of the flow tank 28 are arranged. It is configured to reach the entire area. In the wastewater treatment apparatus according to the present embodiment, only one pair is arranged, but a plurality of pairs may be arranged according to the processing capacity and the like. In the wastewater treatment apparatus according to this embodiment, the photocatalyst cartridge 30 is arranged so as to intersect perpendicularly to the flow direction of the wastewater as described above, but the flowing wastewater efficiently passes through each flat nonwoven fabric 34. For example, it may be arranged obliquely. When the flat nonwoven fabric 34 is disposed obliquely, the flat nonwoven fabric 34 is preferably inclined at about 10 ° with respect to the flow direction, and more preferably at about 5 °.

  In the wastewater treatment apparatus according to this embodiment, an anatase-type titanium oxide is preferably used as the photocatalyst used in the photocatalyst cartridge 30. The photocatalyst can take the form of powder, fiber, thin film or thick film. In the fiber form, there are roughly three types of photocatalytic fibers. These are fibers composed of titanium oxide, fibers having a surface coated with titanium oxide, such as glass fibers, and fibers having a gradient structure of titanium oxide on the surface and high-strength silica on the inside. When composed of titanium oxide, the strength of the fiber itself is low and breakage due to flowing water pressure tends to occur. In the case of coating, there is a problem that the coating phase is peeled off by flowing water. As already shown in Japanese Patent No. 3465699, the present inventors have prepared a photocatalytic fiber having a structure in which no bridging occurs between fibers and a photocatalytic component such as titanium oxide is densely deposited on the surface of each fiber. We are developing. This photocatalyst fiber can be preferably used because it does not depend on the conventional coating technique and has solved the problem that the photocatalyst component on the fiber surface falls off.

  The photocatalyst cartridge 30 includes a flat nonwoven fabric 34 formed in a flat plate shape using the above-described photocatalytic fiber and a pair of wire meshes 36, and the flat nonwoven fabric 34 is a pair of stainless steel wire meshes 36 as shown in FIG. It is pinched by. Thus, by using the wire mesh 36 as a support material and making it into a cartridge shape, the flat nonwoven fabric 34 having a deteriorated photocatalytic function can be easily replaced.

  Next, the preferable example of the flat nonwoven fabric 34 which consists of photocatalyst fiber used for the waste water treatment apparatus which concerns on this embodiment is demonstrated in detail. The photocatalytic fiber is a silica-based composite oxidation that is a composite oxide of an oxide phase (hereinafter referred to as a first phase) mainly composed of a silica component and a metal oxide phase containing Ti (hereinafter referred to as a second phase). It is preferable to consist of physical fibers.

  The first phase is an oxide phase mainly composed of a silica component, and may be amorphous or crystalline, and may be a metal element or metal oxide capable of forming a solid solution or a eutectic compound with silica. It may contain. Examples of the metal element (A) that can form a solid solution with silica include titanium. Examples of the metal element (B) of the metal oxide that can form a solid solution with silica include aluminum, zirconium, yttrium, lithium, sodium, barium, calcium, boron, zinc, nickel, manganese, magnesium, and iron. It is done.

  The first phase forms the internal phase of the silica-based composite oxide fiber and plays an important role in bearing the mechanical properties. The ratio of the first phase to the entire silica-based composite oxide fiber is preferably 40 to 98% by weight, and the desired function of the second phase is sufficiently expressed, and high mechanical properties are also expressed. For this purpose, it is more preferable to control the ratio of the first phase within the range of 50 to 95% by weight.

  On the other hand, the second phase is a metal oxide phase containing Ti and plays an important role in developing the photocatalytic function. Ti is mentioned as a metal which comprises a metal oxide. The metal oxide may be a simple substance, or may be a compound in which a substitutional solid solution is formed with the eutectic compound or a specific element. The second phase forms the surface layer phase of the silica-based composite oxide fiber, and the proportion of the second phase of the silica-based composite oxide fiber varies depending on the type of metal oxide, but is 2 to 60% by weight. Preferably, it is more preferably controlled within a range of 5 to 50% by weight in order to sufficiently exhibit its function and to simultaneously exhibit high strength. The crystal grain size of the metal oxide containing Ti of the second phase is preferably 15 nm or less, particularly preferably 10 nm or less.

  The proportion of Ti contained in the metal oxide contained in the second phase increases in a gradient toward the surface of the silica-based composite oxide fiber, and the thickness of the region where the gradient of the composition is clearly recognized is the surface layer. From 5 to 500 nm, but may be about 1/3 of the fiber diameter. The “existence ratio” of the first phase and the second phase refers to the first phase with respect to the metal oxide constituting the first phase and the entire metal oxide constituting the second phase, that is, the entire silica-based composite oxide fiber. % By weight and the second phase metal oxide.

  Photocatalyst fibers made of silica-based composite oxide fibers can be obtained by the following production method.

(Melt spinning method)
The silica-based composite oxide fiber is a modified polycarbosilane having a structure in which a polycarbosilane having a main chain skeleton represented by the following chemical formula 1 having a number average molecular weight of 200 to 10,000 is modified with an organometallic compound or a modified polycarbosilane A silica-based composite oxide fiber can be produced by melt spinning a mixture of polycarbosilane and an organometallic compound, followed by infusibilization and firing in air or oxygen. Hereinafter, these will be described in detail by dividing them into a first step to a fourth step.

(First step)
This is a process for producing a modified polycarbosilane having a number average molecular weight of 1,000 to 50,000 used as a starting material for producing a silica-based composite oxide fiber. The basic production method of the modified polycarbosilane is very similar to JP-A-56-74126, but it is necessary to carefully control the bonding state of the functional group described therein. This is outlined below.

  The modified polycarbosilane as the starting material is composed mainly of a polycarbosilane having a main chain skeleton represented by the above chemical formula 1 having a number average molecular weight of 200 to 10,000, and a general formula, M (OR ′) n or MR ″. an organometallic compound having a basic structure of m (M is a metal element, R ′ is an alkyl group or phenyl group having 1 to 20 carbon atoms, R ″ is acetylacetonate, and m and n are integers greater than 1) Is derived from

  In order to produce a silica-based composite oxide fiber having an inclined structure, it is necessary to select a slow reaction condition in which only a part of the organometallic compound forms a bond with polycarbosilane. For this purpose, it is necessary to react in an inert gas at a temperature of 280 ° C. or lower, preferably 250 ° C. or lower. Under these reaction conditions, even if the organometallic compound reacts with polycarbosilane, it is bonded as a monofunctional polymer (that is, bonded in a pendant form), and no significant increase in molecular weight occurs. The modified polycarbosilane partially bonded with the organometallic compound plays an important role in improving the compatibility between the polycarbosilane and the organometallic compound.

  In addition, when many functional groups more than two functional groups couple | bond together, the bridge | crosslinking structure of polycarbosilane is formed and the remarkable increase in molecular weight is recognized. In this case, a sudden exotherm and a rise in melt viscosity occur during the reaction. On the other hand, when only one functional group reacts and an unreacted organometallic compound remains, conversely, a decrease in melt viscosity is observed.

  In order to produce a silica-based composite oxide fiber having an inclined structure, it is desirable to select conditions that intentionally leave an unreacted organometallic compound. Mainly, the modified polycarbosilane and the unreacted organometallic compound or the organic metal compound of about 2 to 3 mer are used as starting materials. However, the modified polycarbosilane alone has a very low molecular weight modified polycarbosilane. If a silane component is included, it can be used as a starting material as well.

(Second step)
A spinning dope is prepared by melting the modified polycarbosilane obtained in the first step or a mixture of the modified polycarbosilane and a low molecular weight organometallic compound (hereinafter sometimes referred to as a precursor). Is filtered to remove substances that are harmful when spinning, such as microgels and impurities, and this is spun by a commonly used apparatus for spinning synthetic fibers. The temperature of the spinning dope during spinning varies depending on the softening temperature of the raw material modified polycarbosilane, but a temperature range of 50 to 200 ° C. is advantageous. In the above spinning apparatus, a humidification heating cylinder may be provided below the nozzle as necessary. The fiber diameter is adjusted by changing the discharge amount from the nozzle and the winding speed of a high-speed winding device installed at the lower part of the spinning machine.

  In addition to the melt spinning, the modified polycarbosilane obtained in the first step, or a mixture of the modified polycarbosilane and a low molecular weight organometallic compound, for example, benzene, toluene, xylene or other modified polycarbosilane and a low molecular weight Synthetic fibers that are usually used after dissolving the organometallic compound in a solvent that can be melted to prepare a spinning stock solution, and in some cases filtering it to remove harmful substances such as macrogel and impurities. Spinning can be performed by a dry spinning method using a spinning device, and the winding speed can be controlled to obtain a target fiber.

  In these spinning processes, if necessary, a spinning cylinder is attached to the spinning device, and the atmosphere in the cylinder is mixed with at least one gas of the solvent, or air, inert gas, hot air, By setting the atmosphere of heat inert gas, steam, ammonia gas, hydrocarbon gas, and organosilicon compound gas, solidification of the fibers in the spinning cylinder can be controlled.

(Third step)
The spun fiber obtained in the second step is preheated in an oxidizing atmosphere under the action of tension or no tension to infusibilize the spun fiber. This step is performed for the purpose of preventing the fibers from melting and adhering to the adjacent fibers during the subsequent baking. The treatment temperature and treatment time vary depending on the composition and are not particularly limited, but generally, a treatment condition of several hours to 30 hours is selected within a range of 50 to 400 ° C. The oxidizing atmosphere may contain moisture, nitrogen oxides, ozone, or the like that increases the oxidizing power of the spun fiber, and the oxygen partial pressure may be changed intentionally.

  By the way, depending on the ratio of the low molecular weight substance contained in the raw material, the softening temperature of the spun fiber may be lower than 50 ° C. In this case, the fiber surface oxidation is promoted at a temperature lower than the treatment temperature in advance. In some cases, processing is performed. In the second step and the third step, it is considered that the low molecular weight compound contained in the raw material progresses to the fiber surface, and the base of the target gradient composition is formed. .

(4th process)
The fiber insolubilized in the third step is fired in an oxidizing atmosphere at a temperature range of 500 to 1800 ° C. under tension or no tension, and the target oxide phase mainly composed of silica component (first phase) ) And a metal oxide phase (second phase) containing Ti, a silica-based composite in which the Ti content of the metal oxide constituting the second phase increases in a gradient toward the surface layer. An oxide fiber is obtained. In this step, the organic component contained in the infusible fiber is basically oxidized, but depending on the conditions selected, it may remain in the fiber as carbon or carbide. Even in such a state, when the target function is not hindered, it is used as it is. However, when the target function is hindered, further oxidation treatment is performed. At that time, the temperature and processing time must be selected so as not to cause problems in the intended gradient composition and crystal structure.

  After making the silica-based composite oxide fiber having a photocatalytic function obtained in the fourth step into a short fiber, needle punching or the like can be performed to obtain a flat nonwoven fabric 34.

(Melt blow method)
As another production method, a flat nonwoven fabric made of silica-based composite oxide fibers is melt-blown using a melt-blowing method, and the melt is discharged from a spinning nozzle and from around the spinning nozzle. Spinning by blowing heated nitrogen gas, collecting the spun fibers in a receiver placed at the bottom of the spinning nozzle, forming a non-woven fabric, and then firing the non-woven fabric in an oxidizing atmosphere after infusibilizing. Can be manufactured.

  The diameter of the spinning nozzle is usually about 100 to 500 μm. Nitrogen gas ejection speed is about 30 to 300 m / s, and the higher the speed, the thinner the fiber. The heating temperature of the nitrogen gas is not particularly limited as long as a desired spun fiber can be obtained, but nitrogen gas heated to about 500 ° C. is usually ejected. Conventionally, in a general melt-blowing method, air is used as a jet gas, but it is necessary to use nitrogen in order to spin the precursor. Spinning can be performed stably by using nitrogen as the jet gas.

  When collecting the spun fiber in a receiver disposed at the lower part of the spinning nozzle, it is preferable to perform spinning while sucking from the lower side of the receiver using a suckable receiver. By sucking, the fibers are effectively entangled and a high-strength nonwoven fabric is obtained. The suction speed is preferably in the range of about 2 to 10 m / s.

  By performing the infusibilization treatment and firing similar to the case of the melt spinning described above on the obtained nonwoven fabric, a nonwoven fabric of silica-based composite oxide fibers can be obtained. The silica-based composite oxide fiber produced by the melt blow method has an average fiber diameter of 1 to 20 μm, preferably 1 to 8 μm, more preferably 2 to 6 μm, as compared with fibers produced by melt spinning. It can be thin. Thereby, the surface area of a fiber can also be enlarged and catalyst activity increases. In addition, the nonwoven fabric produced by the melt blow method has a longer fiber length than short fibers produced by the melt spinning method and having a length of about 40 to 50 mm made by the needle punch method. As a result, the nonwoven fabric has high strength (tensile strength of 2N or more) and has sufficient pleatability when processed into a filter or the like.

The basis weight and thickness of the flat nonwoven fabric are not particularly limited, but those having a basis weight of 50 to 500 g / m ² and a thickness of preferably 0.5 to ²⁰ mm are usually used. The thickness can be adjusted by laminating a nonwoven fabric as necessary. If the thickness is less than 0.5 mm, the amount of photocatalyst itself is too small to obtain a sufficient water purification effect. When it is thicker than 20 mm, the flat nonwoven fabric becomes resistance, pressure loss increases, and water treatment becomes difficult. The shape of the flat nonwoven fabric is not particularly limited, but can be round or square according to the shape of the fluidized tank into which the flat nonwoven fabric 34 is inserted. In order to increase the surface area of the flat nonwoven fabric 34 It can also be corrugated.

  According to the method for producing the flat nonwoven fabric 34 as described above, there is no bridging between the fibers, and from the photocatalyst fiber having a structure in which photocatalyst components such as titanium oxide are densely deposited on the surface of each fiber. A flat nonwoven fabric 34 is obtained. Moreover, since this photocatalyst fiber does not depend on the conventional technique of coating, there is no problem that the photocatalyst component on the fiber surface falls off. Further, since the flat nonwoven fabric 34 made of fibers has a structure in which each fiber is dispersed with a certain amount of voids, the contact area between the processing fluid and the photocatalyst becomes very large. Generally, in order to fully exploit the function of the photocatalyst, it is necessary to increase the light irradiation efficiency to the photocatalyst and the contact efficiency with the processing fluid.

  The surface of the photocatalyst fiber is platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu), iron (Fe), nickel (Ni ), Zinc (Zn), gallium (Ga), germanium (Ge), indium (In), and tin (Sn) are preferably supported by at least one metal.

  The method for supporting the metal is not particularly limited, and corresponds to the band gap of the metal oxide constituting the second phase while contacting the liquid containing metal ions of the metal and the silica-based composite oxide fiber. By irradiating light having energy higher than energy, the reduced metal particles can be supported on the reduction site (non-irradiated surface) of the metal oxide. For example, when the second phase is anatase-type titanium oxide, its band gap is 3.2 eV, and therefore, by irradiating light having a corresponding energy, that is, a wavelength of 387 nm or less, the surface of the titanium oxide particles. Metal particles can be supported on the substrate.

  A valve 14 is provided in the flow passage 12 that communicates the first reaction tank 3 and the second reaction tank 7, and the first reaction tank 3 and the second reaction tank 7 are respectively connected by closing the valve. It can be an independent system. In the wastewater treatment apparatus according to the present embodiment, the valve 14 can be a gate valve, a globe valve, a ball valve, a butterfly valve, a needle valve, a stop valve, a check valve, or the like, and a ball valve is preferably used. Moreover, it is preferable that the valve 14 has a function that can be opened and closed at an arbitrary time. As such a valve, an electromagnetic valve or an electric valve is preferable. The opening and closing timing is preferably controlled by the pH in the first reaction tank 3, and the valve is preferably opened and closed when the pH reaches 5.5.

  Next, the operation of the waste water treatment apparatus according to the present embodiment will be described in detail using the process chart shown in FIG. The operation of the wastewater treatment apparatus according to the present embodiment collects the first ultraviolet irradiation process for irradiating wastewater containing organic matter and metal ions with ultraviolet light, and the metal hydroxide generated by the first ultraviolet irradiation process. A metal hydroxide collection step, a second ultraviolet irradiation step of contacting the photocatalyst having titanium oxide on the surface thereof with the wastewater treated in the first ultraviolet irradiation step and the metal oxide removal step, and irradiating the photocatalyst with ultraviolet rays. Is provided.

(First UV irradiation process)
First, the valve 14 is closed, and then a pump (not shown) is operated to allow wastewater containing metal ions and organic substances to flow into the first reaction tank 3 from the drainage inlet 16. At this time, since the valve 14 is in a closed state, the wastewater that has flowed into the first reaction tank 3 does not flow into the second reaction tank 7. Simultaneously with this inflow, the ultraviolet lamp 18 and the air injection unit 22 are operated to irradiate the wastewater with ultraviolet rays and supply air, whereby the organic matter in the wastewater is oxidatively decomposed. Air may be supplied before the ultraviolet lamp 18 is operated. Due to the decomposed organic matter, the pH of the wastewater gradually shifts from the acidic side of 4 or less to the neutral side. When the pH shifts to the neutral side, metal ions in water react to form a metal hydroxide. In general, when the pH in water is 5.5, it is known that metal ions can hardly be dissolved as ions and precipitate as metal hydroxides. Examples of metal ions that precipitate as hydroxide include aluminum, iron, magnesium, calcium, titanium, chromium, manganese, cobalt, nickel, copper, and zinc.

(Metal oxide collection process)
Next, when the wastewater containing the metal hydroxide processed in the 1st reaction tank 3 is supplied to the filter 5 through the circulation path 10 by operating the pump which is not shown in figure, it will be drained by this filter 5 The metal hydroxide is collected and then returned to the first reaction tank 3 through the circulation path 11. The operation of irradiating the returned wastewater with ultraviolet rays again and sending the wastewater to the filter 5 is repeated until the pH of the wastewater is preferably 5.5, and more preferably 6.5. After reaching a predetermined pH, the valve 14 is opened, the first reaction tank 3 and the second reaction tank 7 are in communication, and a pump (not shown) is operated to drain the first reaction tank 3. Is supplied to the second reaction tank 7. In the wastewater treatment apparatus according to the present embodiment, the metal oxide is thus collected and removed by the filter 5, and the wastewater is supplied to the second reaction tank 7 in a state containing almost no metal ions. After the waste water is supplied to the second reaction tank 7, the valve 14 is closed. Thereafter, new waste water is introduced into the first reaction tank 3 and the first ultraviolet irradiation step and the metal hydroxide collecting step described above are performed again in the same manner. At the same time, the second ultraviolet irradiation step described later is performed. Do.

(Second UV irradiation process)
Next, the wastewater treated by the first ultraviolet irradiation step and the metal hydroxide collecting step flows into the second reaction tank 7 and at the same time, the wastewater and the photocatalyst cartridge are operated by operating the ultraviolet lamp 19 and the air injection unit 23. 30 is irradiated with ultraviolet rays, and air is supplied into the waste water, whereby the organic matter in the waste water is oxidatively decomposed. Air may be supplied before the ultraviolet lamp 19 is operated. As the ultraviolet lamp 19, a short wavelength ultraviolet lamp having peak wavelengths at wavelengths of 180 to 190 nm and 250 to 260 nm is used. In general, as a mechanism for decomposing organic substances by such a short wavelength ultraviolet lamp, oxygen dissolved in water is oxidized by ultraviolet rays of 180 to 190 nm to generate OH radicals, and organic substances in water are decomposed by the generated OH radicals. Is done. In other words, since the decomposition of organic matter is governed by the amount of OH radicals generated in water, the amount of dissolved oxygen in water can be maintained at a high level by always supplying air, and the decomposition effect can be maintained high. it can.

  Usually, in a wastewater treatment apparatus using a titanium oxide photocatalyst, the ultraviolet lamp is a black light fluorescent lamp having a wavelength of 351 nm or a sterilizing lamp having a wavelength of 254 nm. This is because the titanium oxide photocatalyst can be excited at a wavelength of 387 nm or less, and these lamps are easily available as products. In the wastewater treatment apparatus 1 according to the present embodiment, it is possible to obtain higher decomposition efficiency by using ultraviolet rays that have not been used conventionally. That is, the wastewater treatment apparatus 1 according to the present embodiment includes the flat nonwoven fabric 34 made of photocatalytic fibers and the ultraviolet lamp 19 that irradiates ultraviolet light having peak wavelengths of 180 to 190 nm and 250 to 260 nm. The light irradiation efficiency to the photocatalyst and the contact efficiency with the wastewater can be kept high. For this reason, it is possible to excite the photocatalyst by irradiating the flat nonwoven fabric 34 with ultraviolet rays of 250 to 260 nm, generate OH radicals with the ultraviolet rays of 180 to 190 nm, and directly decompose the organic matter in the waste water, thereby enhancing the decomposition effect. Can be maintained. At this time, since metal ions in the waste water are collected and removed by the metal hydroxide collecting step, metal hydroxide is rarely formed in the second reaction tank 7. Thereby, sufficient decomposition | disassembly capability of organic substance can be maintained for a long period of time.

Average UV intensity on flat nonwoven is preferably 1~10mW / cm ^2, is preferably a further range of 2~8mW / cm ^2. When the ultraviolet intensity on the surface of the flat nonwoven fabric is 1 to 10 mW / cm ² , water treatment with two ultraviolet components can be performed with high efficiency. In order to make such a range, the distance between the ultraviolet lamp and the flat nonwoven fabric may be set to an appropriate range. Here, the average ultraviolet intensity can be obtained by measuring the ultraviolet intensity at a plurality of locations from the center to the end of the nonwoven fabric surface and averaging the values to obtain the average ultraviolet intensity.

  When the decomposition of the organic matter is insufficient, the waste water is circulated by the circulation path 32 extending from the drain outlet 26 side of the bottom of the fluid tank 28 to the flow passage 12 side, and the decomposition of the organic matter is repeated. When the organic matter is sufficiently decomposed, the treated waste water is taken out from the waste water outlet 26, and the waste water treatment is completed.

  The wastewater treated by the wastewater treatment apparatus 1 according to this embodiment can be reused. The conductivity of this water is 10 μS / m or less, which is equivalent to the conductivity of pure water. The treated water discharged from the drain outlet 26 may remove residual metal ions and organic matter by ion exchange or the like. Moreover, it can be used as a wastewater treatment system by installing appropriate pretreatment devices and posttreatment devices before and after the wastewater treatment device. Examples of such pretreatment devices include those that mainly remove particulate foreign matters such as sand filtration, microfilters, and activated carbon filters. Examples of the post-treatment device include those for the purpose of removing dissolved substances or removing particulate foreign matters contained in a small amount of wastewater such as an ion exchange device, an ultrafiltration membrane, a microfilter, and an activated carbon filter. .

  Hereinafter, examples of the water purification apparatus according to the present invention will be described.

(Production Example 1)
First, titanium oxide / silica fibers were produced as flat nonwoven fabrics used in the examples. That is, 2.5 liters of anhydrous toluene and 400 g of metallic sodium were placed in a 5-liter three-necked flask and heated to the boiling point of toluene under a nitrogen gas stream, and 1 liter of dimethyldichlorosilane was added dropwise over 1 hour. After completion of the dropwise addition, the mixture was heated to reflux for 10 hours to form a precipitate. The precipitate was filtered, washed with methanol and then with water to obtain 420 g of white powder of polydimethylsilane. Polydimethylsilane (250 g) was charged into a three-necked flask equipped with a water-cooled reflux condenser, and heated and reacted at 420 ° C. for 30 hours under a nitrogen stream to obtain polycarbosilane having a number average molecular weight of 1200.

  After adding 100 g of toluene and 64 g of tetrabutoxytitanium to 16 g of polycarbosilane, preheating it at 100 ° C. for 1 hour, slowly raising the temperature to 150 ° C., distilling off the toluene and allowing it to react for 5 hours, further up to 250 ° C. The temperature was raised and reacted for 5 hours to synthesize modified polycarbosilane. In order to intentionally allow the low molecular weight organometallic compound to coexist with the modified polycarbosilane, 5 g of tetrabutoxytitanium was added to obtain a mixture of the modified polycarbosilane and the low molecular weight organometallic compound.

  After the mixture of the modified polycarbosilane and the low molecular weight organometallic compound was dissolved in toluene, the mixture was charged into a glass spinning apparatus, the interior was sufficiently purged with nitrogen, and the temperature was raised to distill off the toluene. Melt spinning was carried out at 0 ° C. The spun fiber was heated to 150 ° C. stepwise in air and infusible, and then fired in air at 1200 ° C. for 1 hour to obtain a titanium oxide / silica fiber nonwoven fabric according to Production Example 1.

(Production Example 2)
The titanium oxide / silica fiber nonwoven fabric obtained in Production Example 1 was immersed in a palladium plating solution (Paradex: manufactured by Tanaka Kikinzoku Co., Ltd.) with a palladium concentration of 2.5 ppm, and ultraviolet light having a wavelength of 351 nm was 4 mW / cm ² . Irradiated with intensity for 4 hours. After the irradiation, the fiber was taken out, washed with water, and further dried to obtain a palladium-supported titanium oxide / silica fiber nonwoven fabric according to Production Example 2. From the results of the weight measurement, the amount of palladium supported was 0.05% by weight.

Example 1
The photocatalyst cartridge containing the flat nonwoven fabric shown in FIG. 2 was made using the nonwoven fabric made of titanium oxide / silica fiber obtained in Production Example 1, and the waste water treatment apparatus shown in FIG. 1 was made. The used ultraviolet lamp is NIQ201 / 107XL (output: 200 W) manufactured by Heraeus Co., Ltd., and synthetic quartz is used as a cover member. The output was 200 W, and this ultraviolet lamp was used in the first reaction tank, 35 in 5 × 7 rows, and in the second reaction tank, 15 in 5 × 3 rows. The wavelengths emitted from the ultraviolet lamp are both 254 nm and 185 nm. The distance between the ultraviolet lamps in the first reaction tank was 70 mm. In the second reaction tank, the distance between the ultraviolet lamp and the photocatalyst cartridge was 45 mm, and the distance between the ultraviolet lamps was 135 mm. The average ultraviolet intensity of the flat nonwoven fabric surface was 8 mW / cm ² . The ultraviolet intensity was measured using a UVR-2 ultraviolet illuminometer manufactured by TOPCON, and nine locations were measured from the center to the end of the flat nonwoven fabric surface, and this average value was defined as the average ultraviolet intensity. A 3M liquid cartridge filter 742B was used as the filter.

  The treated water was prepared by dissolving oxalic acid and aluminum ions with ion-exchanged water to form a 200 ppm oxalic acid aqueous solution containing 30 ppm of aluminum ions. In the first reaction tank, a total of 350 L / min of air aeration was generated from the air injection section, while in the second reaction tank, a total of 200 L / min of air aeration was generated from the air injection section. Furthermore, in the first reaction tank, microbubbles were generated at 60 L / min from a microbubble generator (not shown). The average dissolved oxygen saturation in the treatment solution in each reaction tank was 110% in the first reaction tank and 80% in the second reaction tank. The dissolved oxygen amount was measured using a HORIBA D-50 dissolved oxygen meter, and the saturated dissolved oxygen amount was calculated from the temperature and the dissolved oxygen amount in water.

  The oxalic acid treatment solution 400L was circulated at 167 L / min using the waste water treatment apparatus. A 10-pass process was performed in the first reaction tank, the processed liquid was sent to the second reaction tank with the valve opened, and then a 12-pass process was performed in the second reaction tank. In the wastewater treatment apparatus, 400 L of oxalic acid treatment solution is circulated at 167 L / min, and this treatment time for treating 400 L of the entire solution in 2.4 minutes is defined as one pass for convenience. That is, if the 10-pass process is performed in the first reaction tank, the process time takes 24 minutes. If the 12-pass process is performed in the second reaction tank, the process time is 28.8 minutes only in the second reaction tank. The entire wastewater treatment equipment requires 52.8 minutes. In addition, in order to examine the repetition characteristics of the wastewater treatment apparatus, a 200 ppm oxalic acid aqueous solution containing 30 ppm of aluminum ions is prepared in the solution treated using the wastewater treatment apparatus and subjected to a circulation treatment. Up to 20 times. As a result of examination under these conditions, the oxalic acid concentration was reduced to 10 ppm and the aluminum ion concentration was reduced to 0.1 ppm or less after the first reaction vessel treatment, and then the oxalic acid concentration was decomposed to 0.6 ppm after the second reaction vessel treatment. The decomposition characteristics were almost the same at the 20th repetition, and the oxalic acid decomposition characteristics at the same level as the initial stage were obtained at the 20th repetition.

(Example 2)
Using the nonwoven fabric made of palladium-supported titanium oxide / silica fibers obtained by the method described in Production Example 2, the same conditions as in Example 1 were used for examination. 400 L of treatment solution containing 30 ppm and 200 ppm of oxalic acid in aluminum ions was circulated at 167 L / min. A 10-pass process was performed in the first reaction tank, the processed liquid was sent to the second reaction tank with the valve opened, and then a 12-pass process was performed in the second reaction tank. In the wastewater treatment apparatus, 400 L of oxalic acid treatment solution is circulated at 167 L / min, and this treatment time for treating 400 L of the entire solution in 2.4 minutes is defined as one pass for convenience. That is, if the 10-pass process is performed in the first reaction tank, the process time takes 24 minutes. If the 12-pass process is performed in the second reaction tank, the process time is 28.8 minutes only in the second reaction tank. The entire wastewater treatment equipment requires 52.8 minutes. In addition, in order to examine the repetition characteristics of the wastewater treatment apparatus, a 200 ppm oxalic acid aqueous solution containing 30 ppm of aluminum ions is prepared in the solution treated using the wastewater treatment apparatus and subjected to a circulation treatment. Up to 20 times. As a result, after the first reaction vessel treatment, the oxalic acid concentration was reduced to 10 ppm and the aluminum ion concentration was reduced to 0.1 ppm or less, and then, after the second reaction vessel treatment, the oxalic acid concentration could be decomposed to 0.2 ppm. The decomposition characteristics were almost the same at the 20th repetition, and the oxalic acid decomposition characteristics at the same level as the initial stage were obtained at the 20th repetition.

(Comparative Example 1)
The second reaction tank shown in FIG. 1 does not have a non-woven fabric made of titanium oxide / silica fiber supported and supported by palladium obtained by the method described in Production Examples 1 and 2, and the same conditions as in Example 1 were used. went. 400 L of treatment solution containing 30 ppm and 200 ppm of oxalic acid in aluminum ions was subjected to the same circulation treatment as in Example 1 at 167 L / min. In addition, in order to examine the repetition characteristics of the wastewater treatment apparatus, a 200 ppm oxalic acid aqueous solution containing 30 ppm of aluminum ions is prepared in the solution treated using the wastewater treatment apparatus and subjected to a circulation treatment. Up to 20 times. As a result, after the first reaction tank treatment, the oxalic acid concentration was reduced to 10 ppm and the aluminum ion concentration was reduced to 0.1 ppm or less. Thereafter, after the second reaction tank treatment, the oxalic acid concentration could be decomposed only to 2 ppm, and the wastewater treatment capacity was extremely low. . However, the decomposition characteristics were almost the same even at the 20th repetition.

(Comparative Example 2)
In order to examine the usefulness of the two-tank structure wastewater treatment apparatus shown in Examples 1 and 2, using a nonwoven fabric made of palladium-supported titanium oxide / silica fibers obtained by the method described in Production Example 2, FIG. The photocatalyst cartridge containing the flat nonwoven fabric shown was produced, and the waste water treatment apparatus 50 which concerns on the comparative example 2 of the 1 tank structure shown by FIG. 4 was produced.

  As shown in FIG. 4, the waste water treatment apparatus 50 includes a fluid tank 52 formed in a rectangular parallelepiped shape, an upstream side of the bottom surface of the fluid tank 52 (left side of FIG. 4), and a downstream side of the bottom surface (right side of FIG. 4). , And a filter 52 is provided between the circulation paths 54 and 55. A drainage inlet 56 is formed on the upstream side surface of the fluid tank 52, and a drainage outlet 58 is formed on the downstream side surface. The drainage inlet 56 is connected to the drainage outlet 58 by a pump (not shown). The drainage flows through the circulation paths 54 and 56. And a microbubble generator (not shown) connected from the lower part of the downstream side surface of the fluid tank 52.

  The fluid tank 52 has a flat plate-like shape having a photocatalyst and an ultraviolet lamp 66 for irradiating the waste water in the fluid tank 52 with ultraviolet light, an air injection unit 70 for injecting oxygen into the waste water, and a photocatalyst having titanium oxide on the surface. A photocatalyst cartridge 64 is disposed. The ultraviolet lamp 66 has five lines in the vertical direction and 10 lines in the flow direction so as to irradiate the photocatalyst cartridge 64 with a total of 50 lines, the longitudinal direction of which is perpendicular to the flow direction, and the flow tank 52 It arrange | positions so that it may become parallel with a bottom face. The air injection unit 70 is arranged between the ultraviolet lamps of the ultraviolet lamp 66 closest to the bottom surface of the fluidized tank 52 and is configured to be able to inject air over almost the entire area of the ultraviolet lamp 66 in the longitudinal direction. The flat photocatalyst cartridges 64 are arranged such that their surfaces intersect perpendicularly to the flow direction of the waste water and sandwich the ultraviolet lamp 66 therebetween, and are surfaces perpendicular to the flow direction of the flow tank 52. It is configured to reach the entire area.

In the wastewater treatment apparatus 50 according to Comparative Example 2, the closest distance between the ultraviolet lamp and the photocatalyst cartridge was 45 mm, and the distance between the ultraviolet lamps was 70 mm. A total of 50 ultraviolet lamps (5 × 10 rows) were used, and two photocatalyst cartridges were used. The average ultraviolet intensity of the flat nonwoven fabric surface was 8 mW / cm ² . The ultraviolet lamp used was NIQ201 / 107XL (output: 200 W) manufactured by Heraeus Co., as in Example 1, and synthetic quartz was used for the cover member. The wavelengths emitted from the ultraviolet lamp are both 254 nm and 185 nm. As the filter 62, a 3M liquid cartridge filter 742B was used.

  The treated water was prepared by dissolving oxalic acid and aluminum ions with ion-exchanged water to form a 200 ppm oxalic acid aqueous solution containing 30 ppm of aluminum ions. In addition, a total of 350 L / min of air aeration was generated from the air injection section. Furthermore, microbubbles were generated at 60 L / min from the microbubble generator. The average dissolved oxygen saturation in the treatment solution in the reaction vessel was 110%. The dissolved oxygen amount was measured using a HORIBA D-50 dissolved oxygen meter, and the saturated dissolved oxygen amount was calculated from the temperature and the dissolved oxygen amount in water.

  The oxalic acid treatment solution 400L was circulated at 167 L / min using the waste water treatment apparatus. This process was 22 passes. In the wastewater treatment apparatus, 400 L of oxalic acid treatment solution is circulated at 167 L / min, and this treatment time for treating 400 L of the entire solution in 2.4 minutes is defined as one pass for convenience. In addition, in order to examine the repetition characteristics of the wastewater treatment apparatus, a 200 ppm oxalic acid aqueous solution containing 30 ppm of aluminum ions is prepared in the solution treated using the wastewater treatment apparatus and subjected to a circulation treatment. Up to 20 times.

  As a result of examination under these conditions, after 14 passes, the oxalic acid concentration decreased to 0.1 ppm or less and the aluminum ion concentration decreased to 0.1 ppm or less. In addition, as a result of studying the repeatability, the decomposition characteristics decreased with an increase in the number of repetitions, and the oxalic acid concentration was 15 ppm after the 14th processing time, and the remarkably low decomposition characteristics were 20th. The above results are summarized in Table 1.

  In Table 1, repeatability evaluates the reduction of oxalic acid decomposition performance of the wastewater treatment apparatus, and specifically evaluates the degree of reduction of oxalic acid decomposition performance at the first and 20th cycles of the initial treatment.

  The wastewater treatment apparatus that combines the first reaction tank, the metal hydroxide removal means, and the second reaction tank may exhibit extremely excellent oxalic acid decomposition performance, aluminum ion removal performance, and extremely excellent repeatability. Recognize.

DESCRIPTION OF SYMBOLS 1 Waste water treatment apparatus 3 1st reaction tank 5 Filter 7 2nd reaction tank 14 Valve 18 Ultraviolet lamp 19 Ultraviolet lamp 22 Air injection part 23 Air injection part 30 Photocatalyst cartridge 34 Flat nonwoven fabric 36 Wire mesh

Claims (8)

A first reaction tank having a first ultraviolet irradiation means for irradiating the wastewater containing at least oxalic acid and aluminum ions with ultraviolet rays;
Metal hydroxide removing means for removing metal hydroxide produced in the waste water of the first reaction tank;
A circulation path for circulating the waste water in the first reaction tank;
A second reaction tank having a photocatalyst having titanium oxide on the surface and at least a second ultraviolet irradiation means for irradiating the photocatalyst with ultraviolet rays;
A wastewater treatment device comprising:
The metal hydroxide removal means which is connected through the circulation path to the first reaction tank, the waste water is installed to allow the circulation, drainage of the first reaction vessel the said first ultraviolet light irradiation means A wastewater treatment apparatus, wherein the wastewater from the first reaction tank is supplied to the second reaction tank after being treated by the metal hydroxide removing means. A flow path for circulating the first reaction tank and the second reaction tank;
The flow passage is provided with a valve capable of blocking the flow state,
After drainage of the first reaction vessel is treated by the metal hydroxide removal means and said first ultraviolet light irradiation means, the valve is opened, draining of the first reaction tank is supplied to the second reaction vessel The waste water treatment apparatus according to claim 1, wherein the waste water treatment apparatus is configured as described above. 3. The wastewater treatment apparatus according to claim 1, wherein at least one of the first reaction tank and the second reaction tank further includes an oxygen injection means for injecting oxygen into the wastewater. The wastewater treatment apparatus according to any one of claims 1 to 3, wherein the second ultraviolet irradiation means can irradiate ultraviolet rays having peak wavelengths of 180 to 190 nm and 250 to 260 nm. The wastewater treatment apparatus according to any one of claims 1 to 4 , wherein the photocatalyst is a non-woven fabric of photocatalyst fibers having titanium oxide on the surface. The non-woven fabric of the photocatalyst fiber is a flat nonwoven fabric formed in a flat plate shape, and the second ultraviolet irradiation means includes an ultraviolet lamp,
The flat nonwoven fabric is installed so that its surface intersects with the flow direction of drainage, and the ultraviolet lamp is installed so that its longitudinal direction intersects with the flow direction of drainage. Item 6. A wastewater treatment apparatus according to item 5 . The photocatalyst fiber is composed of a composite oxide fiber of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti, and the metal oxide constituting the second phase. The wastewater treatment apparatus according to claim 5 or 6 , characterized in that it is a silica-based composite oxide fiber in which the proportion of Ti in the product increases in a slanting manner toward the surface layer of the fiber. On the surface of the photocatalytic fiber, platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu), iron (Fe), nickel (Ni ), zinc (Zn), gallium (Ga), germanium (Ge), indium (in), and at least one or more metals in any one of claims 5 to 7, characterized in that it is carried out of the tin (Sn) The waste water treatment apparatus as described.