Water treatment equipment

Abstract

The present invention provides a water treatment device that can suppress the uplift of the packing material caused by oxygen gas generated by the decomposition of hydrogen peroxide to a certain level or lower, and can prevent the outflow of the packing material from the gas venting pipe. [Solution] The water treatment device 1 includes a storage tank 2 for storing hydrogen peroxide-containing wastewater W, a decomposition tower 3 in which a packed bed 4 made of packing material in the hydrogen peroxide-containing wastewater W is arranged, a supply pipe 5 connecting the storage tank 2 and the top of the decomposition tower 3, a water pump 6 for supplying hydrogen peroxide-containing wastewater W to the decomposition tower 3 via the supply pipe 5, and a discharge pipe 7 for treated water W1 connected to the bottom of the decomposition tower 3. A gas venting pipe 8 is provided at the top of the decomposition tower 3. The packing material constituting the packed bed 4 has a backwash expansion rate of 20% or less at a backwash LV of 20 m / h at 20°C. This makes it possible to set the ratio (t / T) of the height of the free board to 1 / 2 or less.

Description

[Technical Field]

[0001] The present invention relates to a water treatment apparatus for hydrogen peroxide-containing wastewater, and particularly to a water treatment apparatus capable of easily treating hydrogen peroxide-containing wastewater. [Background Art]

[0002] Hydrogen peroxide-containing water is widely used in electronic industry processes. For example, wafer substrates and the like are cleaned using ammonia-containing hydrogen peroxide water to remove fine particles (SC1 process). Further, wafer substrates and the like are cleaned using hydrochloric acid-containing hydrogen peroxide water to remove metals (SC2 process). Further, cleaning is performed using sulfuric acid-containing hydrogen peroxide water to decompose and remove resist from substrates (SPM process). Among various cleaning steps using such hydrogen peroxide, there is also wastewater containing hydrogen peroxide with a hydrogen peroxide concentration exceeding 1000 mg / L. Known treatment methods for such hydrogen peroxide-containing wastewater include treatment with a hydrogen peroxide decomposition tower such as an activated carbon tower or a catalyst packed tower.

[0003] As a method for treating this hydrogen peroxide-containing wastewater, Patent Document 1 describes a method for removing hydrogen peroxide by passing wastewater containing high-concentration hydrogen peroxide through a manganese dioxide tower and an activated carbon tower both in an upward flow. Patent Document 2 also discloses a water treatment apparatus in which wastewater containing high-concentration hydrogen peroxide is passed through an activated carbon tower in an upward flow. By passing wastewater containing hydrogen peroxide through an activated carbon tower in an upward flow as in these cases, hydrogen peroxide can be decomposed, and oxygen gas generated by the decomposition of hydrogen peroxide can be smoothly discharged.

[0004] Further, Patent Document 3 discloses a water treatment method in which wastewater containing hydrogen peroxide is passed through an activated carbon tower in an upward flow, and then passed through a silver-supported activated carbon tower in a downward flow to decompose hydrogen peroxide. Further, Patent Document 4 discloses a water treatment apparatus in which wastewater containing hydrogen peroxide is passed downward through an activated carbon tower, and a degassing valve is provided at the upper part of the tower. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-314760 [Patent Document 2] Japanese Patent Publication No. 2006-000827 [Patent Document 3] Japanese Patent Application Publication No. 08-039054 [Patent Document 4] Patent No. 5910635 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the methods described in Patent Documents 1 and 2 have the problem that, because water is passed through the manganese dioxide tower and activated carbon tower in an upward flow, the packed manganese dioxide and activated carbon rub against each other, generating fine metals and pulverized coal from each packing material, which can lead to problems such as membrane clogging in the subsequent membrane treatment. Furthermore, in the water treatment method described in Patent Document 3, water is passed through the second stage silver-supported activated carbon tower in a downward flow, which can suppress the outflow of pulverized coal and other materials due to friction between packing materials, but because the first stage uses an upward flow, the effect of suppressing the outflow of pulverized coal and other materials is still insufficient.

[0007] Furthermore, Patent Document 4 describes a method in which wastewater containing hydrogen peroxide is passed downwards through an activated carbon tower, and the gas is discharged from a gas vent valve at the top of the tower. However, this method has the problem that the oxygen gas generated during the decomposition of hydrogen peroxide can lift the activated carbon upwards in the opposite direction of flow, potentially causing activated carbon to leak out of the activated carbon-packed tower. Spherical activated carbon is a common example of activated carbon, with an average particle size of 5 to 40 mesh, and particularly suitable for 10 to 32 mesh, but other factors that affect the lifting of activated carbon have not been identified.

[0008] Thus, in hydrogen peroxide decomposition towers, there is a risk of packing material leakage due to the uplift caused by the generated oxygen gas. Therefore, it is necessary to design the tower with sufficient excess height, known as a freeboard, relative to the packing height, which in turn necessitates a larger size for the hydrogen peroxide decomposition tower itself.

[0009] The present invention has been made in view of the above problems, and aims to provide a water treatment device that can suppress the uplift of the packing material by oxygen gas generated by the decomposition of hydrogen peroxide to below a certain level, and can prevent the outflow of the packing material from the gas venting pipe. [Means for solving the problem]

[0010] In view of the above objectives, the present invention provides a water treatment apparatus comprising: a storage tank for storing hydrogen peroxide-containing wastewater; a decomposition tower having a packed bed formed of a packing material for decomposing hydrogen peroxide in the hydrogen peroxide-containing wastewater; a supply pipe connecting the storage tank and the upper part of the decomposition tower; a water pump for supplying the hydrogen peroxide-containing wastewater to the decomposition tower; a discharge pipe connected to the lower part of the decomposition tower; and a gas venting pipe connected to the top of the decomposition tower, wherein the packing material has a backwash expansion rate of 20% or less at a backwash LV20m / h at 20°C, and the height of the packed bed (T) and the height of the free board above the packed bed (t) are t / T ≤ 0.5 (Invention 1).

[0011] According to this invention (Invention 1), by using a packing material with a backwash expansion rate of 20% or less at a backwash LV of 20 m / h at 20°C, the uplift of the packing material by oxygen gas generated by the decomposition of hydrogen peroxide can be suppressed to below a certain level, and the outflow of packing material from the venting pipe can be prevented, so the height of the free board can be reduced, which in turn allows for a lower design of the hydrogen peroxide decomposition tower, and thus enables miniaturization of the water treatment device.

[0012] In the above invention (Invention 1), it is preferable that the average particle diameter of the filler is 1.5 mm or more (Invention 2). In addition, in the above inventions (Inventions 1 and 2), the apparent density of the filler is 1 g / cm 3 or more (Invention 3).

[0013] According to the above inventions (Inventions 2 and 3), the backwash expansion rate at a backwash LV of 20 m / h at 20°C can be easily made 20% or less.

Effects of the Invention

[0014] In the water treatment apparatus of the present invention, water is passed in a downward flow through a decomposition tower provided with a packed layer for decomposing hydrogen peroxide in hydrogen peroxide-containing wastewater, treated water from which hydrogen peroxide has been decomposed and removed is discharged from the bottom of the decomposition tower, and gases such as oxygen generated along with the decomposition of hydrogen peroxide are discharged from a degassing pipe provided at the top of the decomposition tower. Since a filler having a backwash expansion rate of 20% or less at a backwash LV of 20 m / h at 20°C is used, the height of the freeboard that prevents the filler from flowing out from the degassing pipe can be reduced. Therefore, the height of the hydrogen peroxide decomposition tower can be designed to be low, and the size of the water treatment apparatus can be reduced.

Brief Description of Drawings

[0015] [Figure 1] It is a flow diagram showing a water treatment apparatus for hydrogen peroxide-containing wastewater according to an embodiment of the present invention. [Figure 2] It is a flow diagram showing a test apparatus for a water treatment apparatus for hydrogen peroxide-containing wastewater of Comparative Example 1. [Figure 3] It is a flow diagram showing a test apparatus for a water treatment apparatus for hydrogen peroxide-containing wastewater of Example 1.

Mode for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0017] [Hydrogen peroxide-containing wastewater] As the hydrogen peroxide-containing water to be treated in the present embodiment, wastewater with a high hydrogen peroxide concentration having a hydrogen peroxide concentration of 100 to 10000 mg / L, particularly about 200 to 8000 mg / L, is suitable. The pH of this hydrogen peroxide-containing water is not particularly limited, and may be any of neutral, acidic or alkaline, but neutral to alkaline hydrogen peroxide-containing water is particularly suitable.

[0018] [Water treatment apparatus] The water treatment apparatus of the present embodiment has, for example, the configuration shown in Fig. 1. In Fig. 1, the water treatment apparatus 1 includes a storage tank 2 that stores hydrogen peroxide-containing wastewater W, a decomposition tower 3 provided with a packed bed 4 formed of a filler serving as a hydrogen peroxide decomposing material for hydrogen peroxide in the hydrogen peroxide-containing wastewater W, a supply pipe 5 that communicates the storage tank 2 with the upper part of the decomposition tower 3, a water feed pump 6 that supplies the hydrogen peroxide-containing wastewater W to the decomposition tower 3 via the supply pipe 5, and a discharge pipe 7 for treated water W1 connected to the bottom of the decomposition tower 3. A degassing pipe 8 is provided at the top of the decomposition tower 3, and the degassing pipe 8 is provided with an opening adjustment valve 9 serving as an opening adjustment mechanism. The degassing pipe 8 has a diameter smaller than at least the supply pipe 5. The decomposition tower 3 maintains airtightness except for the supply pipe 5, the discharge pipe 7 and the degassing pipe 8.

[0019] In the water treatment apparatus 1 as described above, the filler constituting the packed bed 4 has a backwash expansion rate of 20% or less at a backwash LV of 20 m / h at 20°C. When the backwash expansion rate exceeds 20%, the filler rises to a high level, so it is necessary to sufficiently secure the height of the free board above the packed bed 4, making it impossible to achieve a compact water treatment apparatus. There is no particular limitation on the lower limit of the backwash expansion rate, but it is 1% or more, particularly 5% or more. In order to achieve such a backwash expansion rate, specifically, the filler preferably has an average particle diameter of 1.5 mm or more. Further, the apparent density of the filler is 1 g / cm 3 or more is preferable. Granular activated carbon is suitable as such a hydrogen peroxide decomposing material. Further, a metal catalyst that decomposes hydrogen peroxide (for example, Mn-based catalysts such as manganese dioxide, platinum group catalysts, etc.) can also be used.

[0020] (Water treatment method) Next, a water treatment method using the water treatment device 1 described above will be explained. First, the water supply pump 6 is driven to pump the hydrogen peroxide-containing wastewater W from the storage tank 2 through the supply pipe 5 to the top of the decomposition tower 3, filling the tower 3. As a result, the hydrogen peroxide-containing wastewater W passes through the packed bed 4 of the hydrogen peroxide decomposition material in a downward flow due to gravity, during which time the hydrogen peroxide is decomposed. The treated water W1, from which the hydrogen peroxide has been decomposed, is discharged from the discharge pipe 7 connected to the bottom of the decomposition tower 3. The SV of the hydrogen peroxide-containing wastewater W at this stage is 1-20h -1 , especially 5-10 hours -1 It is preferable to keep it to a certain extent. In this embodiment, since the hydrogen peroxide-containing wastewater W flows through the packed bed 4 of the hydrogen peroxide decomposition material in a downward flow, the flow of the packing material constituting the packed bed 4 can be minimized, thereby minimizing the outflow of fine metals and pulverized coal.

[0021] As this downward-flowing water continues, oxygen gas or a gas mainly composed of this oxygen gas, produced by the decomposition of hydrogen peroxide in the packed bed 4, forms bubbles B and rises up the decomposition tower 3. At this time, a gas venting pipe 8 is provided to discharge the gas, making continuous treatment possible.

[0022] In the treatment of hydrogen peroxide-containing wastewater W, as bubbles B generated by the decomposition of hydrogen peroxide in the packed bed 4 rise up the decomposition tower 3, packing materials such as activated carbon and Mn sand are stirred up. However, in this embodiment, the packing material constituting the packed bed 4 has a backwash expansion rate of 20% or less at a backwash LV of 20 m / h at 20°C. Therefore, even if the height (t) of the upper free board is set to 1 / 2 or less of the height (T) of the packed bed 4, the packing material will not be stirred up and flow out of the gas venting pipe 8, making it possible to make the water treatment device 1 more compact. Specifically, in order to achieve such a backwash expansion rate, the packing material must have an average particle size of 1.5 mm or more and / or an apparent density of 1 g / cm³. 3 That should suffice.

[0023] The present invention has been described above based on the above embodiments, but the present invention is not limited to the above embodiments and can be implemented in various modified forms. For example, the water treatment device 1 may have various ancillary equipment, for example, hydrogen peroxide-containing wastewater W may be supplied from the supply pipe 5 through a trough, or from a shower head. Also, the gas venting pipe 8 can be connected to the storage tank 2 or discharged outside the system. [Examples]

[0024] The present invention will be described in more detail based on the following specific examples, but the present invention is not limited to the following examples.

[0025] [Test equipment and processing conditions] A hydrogen peroxide solution with a hydrogen peroxide concentration of 10,000 mg / L was adjusted to a pH of 10.5 with a sodium hydroxide solution to prepare simulated hydrogen peroxide-containing wastewater W. As the hydrogen peroxide (H2O2) decomposition packing material, Kurita Water Industries Ltd.'s activated carbon "Klicol WG-868" (average particle size: 1.08 mm, apparent density: approximately 0.5 g / cm³) was used as the packing material in Comparative Example 1. 3 In Example 1, Chinese-made Mn sand (particle size: 1-2 mm, apparent density: approximately 1.85 g / cm³) was used as the packing material, with a backwash expansion rate of 25% at LV20m, 20℃. 3 A backwash expansion rate of 5% (@LV20m, 20℃) was used for each example. This packing material was packed into a column (decomposition column 3) measuring φ40mm × H1000mm to a height of H500mm (T), and the above simulated liquid was passed through it in a downward flow at SV10 ≈ 105 mL / min, and the treated water W1 was discharged from the bottom of decomposition column 3. In both Comparative Example 1 and Example 1, the hydrogen peroxide concentration of the treated water W1 was reduced to several mg / L. In addition, the generated oxygen gas was continuously discharged from the treated water W1 through a venting pipe 8 installed at the top of the column. The height (t) of the free board was 500mm, and t / T = 1.

[0026] [Comparative Example 1] In the treatment of hydrogen peroxide-containing wastewater W as described above, the activated carbon was stirred up by the oxygen gas generated by the decomposition of hydrogen peroxide, resulting in the activated carbon used as packing material P rising to approximately 40 cm from its initial packing height. In other words, it was confirmed that there is a risk of the packed activated carbon flowing out unless a free board of 80% or more relative to the packing height (T) is secured.

[0027] [Example 1] In the treatment of hydrogen peroxide-containing wastewater W as described above, although oxygen gas is generated by the decomposition of hydrogen peroxide, the stirring up of Mn sand as packing material P was limited to only a few centimeters. In other words, by using the packing material shown under these conditions, it was determined that the outflow of packing material can be suppressed even if the ratio of the height of the free board (t) to the packing height (T) (t / T) is 0.5 or less, and that the water treatment device can be miniaturized. [Explanation of Symbols]

[0028] 1. Water treatment equipment 2 Storage tanks 3 Decomposition tower 4 Filled bed 5 Supply pipe 6. Water supply pump 7 Discharge pipe 8. Gas venting pipe 9. Opening degree adjustment valve (opening degree adjustment mechanism) W Wastewater containing hydrogen peroxide W1 treated water T is the height of the packed bed. t Freeboard height B bubbles P filler

Claims

1. A storage tank for storing wastewater containing hydrogen peroxide, A decomposition tower having a packed bed formed of a packing material that decomposes hydrogen peroxide in the hydrogen peroxide-containing wastewater, A supply pipe connecting the storage tank and the upper part of the decomposition tower, A water pump for supplying the hydrogen peroxide-containing wastewater to the decomposition tower, A discharge pipe connected to the lower part of the decomposition tower, A gas vent pipe connected to the top of the aforementioned decomposition tower and A water treatment apparatus having, The aforementioned filler has a backwash expansion rate of 20% or less at a backwash LV of 20 m / h at 20°C. The height (T) of the packed bed and the height (t) of the free board above the packed bed are t / T ≤ 0.5 It is a water treatment device.

2. The water treatment apparatus according to claim 1, wherein the average particle size of the filler is 1.5 mm or more.

3. The apparent density of the filler is 1 g / cm³. ３ The water treatment apparatus according to claim 1 or 2.

Images