JP5208397B2 - Water treatment method and water treatment apparatus - Google Patents

Description

  The present invention relates to a water treatment method and a water treatment apparatus used in the electronics industry and the pharmaceutical industry, and in particular, organic substances contained in raw water such as washing water, city water, and industrial water used in a semiconductor washing process. The present invention relates to a water treatment method and a water treatment apparatus for producing pure water that has been subjected to oxidative decomposition treatment and from which organic substances are substantially removed.

  In the manufacturing process of liquid crystals, semiconductor elements (LSIs), or pharmaceuticals, pure water with a very low content of ionic substances, fine particles, organic substances, dissolved gases, viable bacteria, and the like is used. Among them, in the electronics industry, a large amount of pure water is used for pre-purification water and the like, and the demand for purity of pure water becomes more and more severe as the degree of integration of ULSI (ultra-high density large scale integrated circuit) increases. It is coming.

  By the way, in a semiconductor production process represented by ULSI or the like, an organic solvent is frequently used for removing a photoresist or the like, and an organic substance such as an organic solvent is mixed in waste water discharged in the semiconductor production process. Therefore, in order to regenerate the wastewater and reuse it for the production process of semiconductors, it is necessary to remove organic substances contained in the wastewater.

  Conventionally, as a method of removing organic substances contained in wastewater, hydrogen peroxide is added to the wastewater and ozone is dissolved to oxidize and decompose hardly decomposed organic substances, and then ion exchange treatment is performed to remove the organic matter from the wastewater. A method for removing organic substances (for example, see Patent Document 1) and a method for decomposing and removing organic substances by irradiating ultraviolet rays after dissolving ozone in waste water (for example, see Patent Document 2) have been used. It was.

  However, in these conventional methods, reaction tanks used for oxidative decomposition of organic substances by ozone are often designed with a residence time of about 1 hour, and particularly in an apparatus with a large treatment flow rate, the residence time is large. As a result, the installation space is increased as it is, and when the ultraviolet irradiation is performed, the ultraviolet irradiation apparatus is bulky, so that there are many cases where it is difficult to install due to the need for an empty space in the semiconductor manufacturing factory.

Therefore, there is a demand for a compact reactor that efficiently processes in a relatively short time such as a residence time of 2 to 5 minutes. As one of such devices, there is a reactor using an ejector (for example, And Patent Document 3). In the case of using this apparatus, ozone is dissolved in the water to be treated by using an ejector to contact the ozone gas and the water to be treated, and then introduced into the reaction vessel to oxidize and decompose the organic matter. According to this apparatus, the ozone gas and the water to be treated are contacted instantaneously by the ejector, and the mixing can be performed efficiently. Therefore, an oxidative decomposition reaction is performed in a relatively short time, and an efficient treatment becomes possible.
Japanese Patent Application Laid-Open No. 11-114584 JP 2000-84574 A JP 2003-94076 A

  However, in these conventional methods, when the amount of hydrogen peroxide supplied is small from the viewpoint of saving, the removal rate of TOC in the reaction apparatus is deteriorated. This is thought to be because the decomposition rate does not increase sufficiently when the supply amount of hydrogen peroxide is small.

  In this case, it is conceivable that the time required for the decomposition reaction is increased by increasing the residence time to allow sufficient reaction, but if the residence time is increased, the reaction vessel needs to be enlarged, as described above. Often limited by space issues.

  Furthermore, dissolved ozone is often observed in the treated water discharged from the reaction vessel, and these dissolved ozone will be decomposed and disappeared while being sent to the downstream apparatus. So, so to speak, ozone is consumed wastefully. That is, ozone that should contribute to the reaction decomposes without being used because the reaction rate is slow. In other words, the presence of these dissolved ozone is thought to be because the reaction has not converged because hydrogen peroxide has a low concentration.

  In addition, when the amount of hydrogen peroxide added is large, the TOC removal rate in the reaction apparatus also deteriorates. This is because, in the presence of hydrogen peroxide, a large amount of radicals are generated instantaneously, but these radicals disappear so that each other contributes to the decomposition of the target organic matter. It is done.

  In this case, the dissolved ozone concentration in the treated water discharged from the reactor is almost zero. That is, ozone in the solution does not remain and the reaction is considered to have converged. However, even if the hydrogen peroxide concentration is further increased, the decomposition efficiency becomes worse as the hydrogen peroxide concentration is increased. It is understood that the high concentration of hydrogen peroxide is never efficient for the decomposition of TOC.

  Therefore, it is better for the TOC decomposition efficiency to react slowly with low-concentration hydrogen peroxide. However, the residence time is required, and the residence time is often restricted at the stage of designing the apparatus. Therefore, it is considered that an appropriate concentration of hydrogen peroxide needs to be added.

  In other words, the appropriate concentration of hydrogen peroxide is the minimum hydrogen peroxide concentration at which decomposition will converge under various conditions such as the water quality conditions and the residence time, and is not more than that. The concentration of hydrogen peroxide for performing an efficient reaction has a peak. In order to improve the efficiency, it is preferable to increase the residence time. However, when the residence time cannot be increased, there is a problem that the addition of high-concentration hydrogen peroxide lowers the efficiency.

  The present invention has been made in view of such problems, and decomposes organic substances contained in water to be treated such as cleaning water, city water and industrial water used in the semiconductor cleaning process with high efficiency, and organic substances are almost removed. An object of the present invention is to provide a water treatment method and a water treatment apparatus capable of producing pure water having a sufficiently low total organic carbon content (TOC).

  The present inventor has made extensive studies to solve the above-mentioned problems. When the ozone gas is dissolved in the water to be treated and hydrogen peroxide is added in two or more stages, the residence time of the reaction vessel is short. Has also found that the decomposition efficiency of organic substances in water to be treated can be improved, and the present invention has been completed.

  That is, the water treatment method of the present invention includes a first hydrogen peroxide addition step in which first hydrogen peroxide is added and dissolved in the water to be treated, and the water to be treated in which the first hydrogen peroxide is dissolved. The ozone dissolving step for contacting ozone gas to dissolve ozone, the first hydrogen peroxide and the water to be treated in which ozone gas is dissolved are introduced into the reaction vessel, and the organic matter contained in the water to be treated is oxidatively decomposed first. The second hydrogen peroxide addition step of adding the second hydrogen peroxide to the water to be treated during the organic matter decomposition step and the first organic matter decomposition step or after the first organic matter decomposition step And a second organic substance decomposition step of further oxidizing and decomposing organic substances in the water to be treated by adding the second hydrogen peroxide.

  The water treatment apparatus of the present invention includes a first hydrogen peroxide adding means for adding and dissolving the first hydrogen peroxide to the water to be treated, an ozone gas generating means for generating ozone gas, a first excess water. The ozone water generated from the ozone gas generating means is brought into contact with the water to be treated in which hydrogen oxide is dissolved, and the ozone dissolving means for dissolving ozone and the water to be treated in which the first hydrogen peroxide and ozone are dissolved are introduced and treated. A reaction vessel that oxidatively decomposes organic substances contained in the water, and a second hydrogen peroxide addition unit that adds the second hydrogen peroxide to the water to be treated in the reaction vessel or at a later stage of the reaction vessel. It is characterized by this.

  According to the water treatment method and the water treatment apparatus of the present invention, while reducing the amount of ozone and hydrogen peroxide used in the treatment, the organic matter in the water to be treated is removed with the same decomposition efficiency as before to regenerate pure water. be able to. Further, the oxidative decomposition reaction can be performed in a short time, and the size of the apparatus itself can be designed to be compact.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows the configuration of a water treatment apparatus according to the first embodiment of the present invention. This water treatment device 1 adjusts the pH of water to be treated and a water tank 2 to be treated for storing organic wastewater containing organic matter, for example, wastewater used for cleaning semiconductor wafers in a semiconductor manufacturing device. PH adjusting means 3, first hydrogen peroxide adding means 4 for adding and dissolving first hydrogen peroxide in the water to be treated, ozone gas generating means 5 for generating ozone gas, and first peroxidation The ozone gas generated from the ozone gas generating means 5 is brought into contact with the water to be treated in which hydrogen is dissolved, and the ozone dissolving means 6 for dissolving ozone and the water to be treated in which the first hydrogen peroxide and ozone are dissolved are introduced. A reaction vessel 7 for oxidizing and decomposing organic substances contained in water; a second hydrogen peroxide addition means 8 for further adding and dissolving the second hydrogen peroxide in the water to be treated in the reaction vessel 7; container In the treated water tank 9 for storing the processed treated water, and discharge ozone treatment means 10 for treating the exhaust ozone discharged from the reaction vessel 7 and the treated water tank 9 and is formed from.

  In the water treatment method using this water treatment apparatus 1, the water to be treated contained in the water tank 2 to be treated begins to flow from the tank, and the pH of the water to be treated is first adjusted by the pH adjusting means 3, Next, a first hydrogen peroxide addition step of adding hydrogen peroxide by the first hydrogen peroxide addition means 4 is performed to dissolve the hydrogen peroxide in the water to be treated.

  The pH adjusting means 3 used here adjusts the pH of the water to be treated so that the oxidative decomposition reaction with hydrogen peroxide and ozone can be carried out efficiently. It is preferable to add an amount such that the pH at the outlet of the reaction vessel 7 is near neutral. As the pH adjuster in the present invention, a known pH adjuster can be used. However, when the reaction proceeds due to an organic acid generated by oxidative decomposition of an organic substance, the pH of the water to be treated is brought to the acidic side. Usually, alkalis such as sodium hydroxide, sodium carbonate and calcium hydroxide are preferably used.

  The first hydrogen peroxide adding means 4 may be any means as long as it adds and dissolves the first hydrogen peroxide in the water to be treated. For example, a medicine usually used for adding a chemical to the water to be treated Note pumps. The addition method may be either an intermittent supply method or a continuous supply method, and is preferably interlocked with the transfer pump of the water to be treated, and the injection operation is always performed while the transfer pump is moving.

  Next, the ozone water generated from the ozone gas generating means 5 is brought into contact with the water to be treated in which the first hydrogen peroxide is dissolved by using the ozone dissolving means 6 to perform ozone gas dissolving step for dissolving ozone, and then the first The water to be treated in which hydrogen peroxide and ozone are dissolved is introduced into the reaction vessel 7, and a first organic substance decomposition step is performed in which organic substances contained in the water to be treated are oxidized and decomposed.

Here, it is presumed that the oxidative decomposition reaction proceeds by the following mechanism.
The first hydrogen peroxide and ozone dissolved in the water to be treated are
H ₂ O ₂ + O ₃ → .OH + HO ₂ ⁻ + O ₂ [1]
HO ₂ ⁻ + O ₃ → .OH + O ₂ ⁻ + O ₂ ... [2]
OH radicals (.OH: hydroxyl radical) are generated by reacting with each other as shown in FIG.

On the other hand, on the alkaline side, hydrogen peroxide and ozone are
H ₂ O ₂ + OH ⁻ → HO ₂ ⁻ + H ₂ O [3]
H ₂ O ₂ → HO ₂ ⁻ + H ⁺ ... [4]
^{_{O 3 + OH - → · HO}} 2 + O 2 - ... [5]
HO ₂ radical (.HO ₂ ) is generated by reacting with a base as shown in FIG. Here, the resulting HO ₂ ^- are also involved in the generation of the OH radicals by reacting with the ozone. Therefore, it can be understood that the higher the concentration of ozone in the water to be treated, the more OH radicals and HO ₂ radicals are generated.

And, by the OH radical and HO ₂ radical generated by the above reaction,
RH + .OH → .R + H ₂ O ... [6]
R + O ₃ (O ₂ ) → oxidation product [7]
RH + .HO ₂ → oxidation product + H ₂ O ... [8]
The reaction shown in (1) proceeds and the organic matter is oxidatively decomposed.

Here, by making hydrogen peroxide coexist in the water to be treated and setting the pH of the water to be treated to the alkali side, the generation amount of OH radicals and HO ₂ radicals in the water to be treated can be increased. Degradation can be promoted.

The ozone gas generating means 5 can be used without any particular limitation as long as it can generate ozone gas, and usually uses an ozone generator (ozonizer) that utilizes actions such as silent discharge, electrolysis, and light from air or oxygen. be able to. In this invention, in order to accelerate | stimulate decomposition | disassembly of the organic substance in to-be-processed water, it is preferable to raise the dissolution rate of ozone in water and to raise the ozone concentration in water. The concentration of the ozone gas supplied is usually 50 to 250 g / Nm ^3, preferably from 100 to 150 g / Nm ^3.

In addition, the ozone dissolving means 6 makes the water to be treated in which the first hydrogen peroxide is dissolved and the ozone gas generated from the ozone gas generating means 5 in gas-liquid contact to dissolve ozone into the water to be treated. Examples of the ozone dissolving means 6 include a diffuser tube, a diffuser, an ejector, a venturi tube, and the like, and an ejector is preferable in that ozone can be efficiently dissolved in the water to be treated. For example, the diameter of the ejector is normally 15A to 80A (1/2 "to 3 inches), and the sectional area of the nozzle portion is 5 to 500 mm ² . Although it is related to the flow rate of the passing water, the amount of water is 0.5 to 50 m ³ / h, and the amount of gas to be sucked is 0.3 to ³⁰ N · m ³ / h. In order to carry out the reaction efficiently, it is preferably installed immediately before the reaction vessel 7.

  And the reaction container 7 introduce | transduces the to-be-processed water which melt | dissolved 1st hydrogen peroxide and ozone gas, and performs the oxidative decomposition reaction of the organic substance contained in to-be-processed water. Here, the reaction vessel 7 only needs to be able to retain the liquid to be treated for a time during which the oxidative decomposition reaction can be sufficiently performed, for example, about 2 to 5 minutes. Absent. However, if the tank type is used, the apparatus itself becomes large and requires a space. In addition, it is necessary to provide a stirring means in order to sufficiently perform the reaction in the water to be treated, so that the installation space can be made compact. It is preferable that the pipe form does not require a stirring means.

In the case of a piping type, the reaction vessel 7 is composed of a cylindrical reaction tube, and if the flow of water to be treated in this reaction vessel is a downward flow or sideways, gas-liquid separation is likely to occur, and the reaction efficiency tends to be lowered. It is preferable to use a flow. For example, in the case of an upward flow, the height of the reaction tube can be provided without any particular restriction, but considering an actual indoor installation location, about 4 to 6 m is often the limit. It is. In addition, since ozone gas is a gas, it exits the reaction tube at a higher rising speed than the water to be treated. Therefore, it is preferable to ensure the contact time with the water to be treated by making the height direction as long as possible.
Further, the thickness of the reaction tube may be set so that the liquid to be treated can be retained only for a time during which the oxidative decomposition reaction can be sufficiently performed, for example, about 2 to 5 minutes. Is preferably about 80 to 800 A, and the length is preferably about 2000 to 6000 mm, and is preferably the same as or thicker than the pipe serving as another flow path.

  In addition, when the reaction vessel 7 is in the form of a pipe as described above, the oxidative decomposition reaction can be sufficiently performed only with the pipe, and the water treatment apparatus can be made compact, and the installation space can be saved. And when the flow volume of to-be-processed water is large, this reaction container 7 can be provided in parallel and a process can also be performed efficiently.

  Next, during the first organic substance decomposition step in which the organic substance is oxidatively decomposed as described above, the second hydrogen peroxide is further added to the water to be treated using the second hydrogen peroxide addition means 8. A second hydrogen peroxide addition step to be added is performed, and the second organic matter decomposition step is performed by the addition of the second hydrogen peroxide, thereby further promoting the oxidative decomposition of the organic matter. Similar to the first hydrogen peroxide addition means, the second hydrogen peroxide addition means 8 only needs to add the second hydrogen peroxide to the water to be treated and dissolve it.

  Here, in the second hydrogen peroxide addition step, it is preferable to add additional hydrogen peroxide when the oxidative decomposition reaction proceeds to some extent in the first organic matter decomposition step and the reaction efficiency is lowered, and It is necessary to ensure the residence time of the water to be treated in the reaction vessel 7 so that the hydrogen peroxide of 2 is sufficiently diffused and mixed in the water to be treated to allow the reaction. If the residence time is short and the water to be treated is discharged from the reaction vessel 7 without being sufficiently mixed, the oxidative decomposition reaction in the second organic matter decomposition step becomes insufficient, which is not preferable.

  Therefore, the position where the second hydrogen peroxide is added by the second hydrogen peroxide addition means 8 is not particularly limited as long as the second organic matter decomposition reaction can be sufficiently performed. Circulation means may be connected to the outside, but it is preferably introduced near the center of the radial cross section of the reaction vessel 7 (in the case of a cylindrical reaction tube, near the axis of the reaction tube). In the axial direction, it is preferable to introduce at a half-divided point of the reaction vessel, that is, an intermediate point between the inlet and the outlet of the reaction vessel 7. Furthermore, introducing the circulating water in a direction opposite to the flow of the water to be treated in the reaction vessel causes the water to be treated and the circulating water to cross, and thoroughly mix ozone and hydrogen peroxide. This is preferable in that the reaction can be performed efficiently.

As described above, it is a feature of the present invention that the hydrogen peroxide to be added is added in two stages at different points in time, and the hydrogen peroxide to be added here is a second peroxidation rather than the first hydrogen peroxide. It is preferable that the injection rate when hydrogen is added is high, and the injection rate of the second hydrogen peroxide is 2 to 6 times the injection rate of the first hydrogen peroxide. Is particularly preferred. Here, the injection rate (ppm) of hydrogen peroxide is obtained by the hydrogen peroxide addition amount (g-H ₂ O ₂ / hr) ÷ treatment flow rate (m ³ / hr) and is almost the same as the actual concentration. .

In addition, regarding the relationship between ozone and hydrogen peroxide, in order to perform the reaction efficiently, when the ozone injection rate in the ozone dissolving step is 1, the excess in the first hydrogen peroxide adding step is considered. The hydrogen oxide injection rate is preferably 0.04 to 0.12. Here, the ozone injection rate (ppm) is obtained by ozone gas concentration (g-O ₃ / Nm ³ ) × ozone gas flow rate (Nm ³ / hr) ÷ treatment flow rate (m ³ / hr), and hydrogen peroxide injection rate ( ppm) is obtained by converting the concentration by hydrogen peroxide addition amount (g-H ₂ O ₂ / hr) ÷ treatment flow rate (m ³ / hr).

  The treated water treated up to the second organic matter decomposition step is discharged from the reaction vessel 7 and stored in the treated water tank 9. At this time, ozone that has not been dissolved in the water to be treated exists as a gas in the reaction vessel 7 and the treated water tank 9, and the waste ozone treatment apparatus 10 treats the waste ozone so that it is rendered harmless and can be released into the atmosphere. Is done.

  Further, it is preferable to treat the treated water discharged from the reaction vessel 7 by passing it through a column to be filled with activated carbon in order to remove residual ozone and hydrogen peroxide. At this time, the organic acid generated by oxidative decomposition is used. In addition, TOC such as organic matter that has not been decomposed can be removed at the same time. The treatment with activated carbon is preferably performed after the treated water tank 9.

  Although the case where the first organic substance decomposition reaction and the second organic substance decomposition reaction are performed in one reaction container is shown here, the reaction may be performed sequentially in separate reaction containers. In any case of using a different reaction vessel or using a different reaction vessel, the decomposition reaction of three or more stages may be performed.

(Second Embodiment)
FIG. 2 shows a configuration of a water treatment apparatus according to the second embodiment of the present invention. Here, about the structure which is common in 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. The same applies to other descriptions.

  The water treatment apparatus 11 includes a treated water tank 2 for storing organic waste water, pH adjusting means 3 for adjusting the pH of the treated water, and first hydrogen peroxide added to the treated water. The first hydrogen peroxide adding means 4 for dissolving, the ozone gas generating means 5 for generating ozone gas, the ozone gas generated from the ozone gas generating means 5 is brought into contact with the water to be treated in which the first hydrogen peroxide is dissolved, and ozone is The ozone dissolving means 6 for dissolving, the water to be treated in which the first hydrogen peroxide and ozone are dissolved are introduced, and the reaction vessel 7 for oxidizing and decomposing organic substances contained in the water to be treated is discharged from the reaction vessel 7. Circulating means 12 for circulating the water to be treated to the reaction vessel 7 and a second peroxidation further to the water to be circulated (hereinafter referred to as circulating water) in the subsequent stage of the reaction vessel 7 (in the middle of the circulation means 12). Second to add hydrogen A treatment water tank 9 for storing treated water treated by the hydrogen oxide addition means 13, the reaction vessel 7 to which the second hydrogen peroxide is added, and exhaust ozone gas discharged from the reaction vessel 7 and the treatment water tank 9 And waste ozone treatment means 10 to be treated.

  In this embodiment, the basic configuration of the apparatus is the same as that of the first embodiment, and only the differences will be described below.

  In the second embodiment, an oxidative decomposition reaction of an organic substance is performed in the reaction vessel 7, but the second hydrogen peroxide is not added to the reaction vessel 7 as in the first embodiment. The hydrogen peroxide is added to the water to be treated (circulated water) discharged from the second hydrogen peroxide by the second hydrogen peroxide addition means 13, and the second hydrogen peroxide is further added. The circulated water is again introduced into the reaction vessel 7 so that the second organic substance decomposition reaction is carried out in the reaction vessel 7.

  At this time, the position to introduce the circulation is not particularly limited as long as the second organic matter decomposition reaction can be sufficiently performed, and the circulation means may be directly connected to the outside of the pipe. It is preferably introduced near the center of the cross section in the radial direction (in the vicinity of the axis of the reaction tube in the case of a cylindrical reaction tube). 7 is preferably introduced at the midpoint between the inlet and the outlet. Furthermore, introducing the circulating water in a direction opposite to the flow of the water to be treated in the reaction vessel causes the water to be treated and the circulating water to cross, and thoroughly mix ozone and hydrogen peroxide. This is preferable in that the reaction can be performed efficiently. Such circulation is preferable because the oxidative decomposition efficiency of the organic matter can be improved as compared with the two-stage addition method in the first embodiment.

  In addition, when water is passed through activated carbon, ozone, hydrogen peroxide, and organic acid are removed by activated carbon after the second organic matter decomposition step, which is immediately after the first organic matter decomposition step. Should not be provided. This is because hydrogen peroxide remains in the water to be treated after the first organic matter decomposition step, and this is used in the second organic matter decomposition step.

(Third embodiment)
FIG. 3 shows a configuration of a water treatment apparatus according to the third embodiment of the present invention. Here, about the structure which is common in 1st and 2nd embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. The same applies to other descriptions.

  This water treatment device 21 includes a treated water tank 2 for storing organic wastewater, a pH adjusting means 3 for adjusting the pH of the treated water, and first hydrogen peroxide added to the treated water. The first hydrogen peroxide adding means 4 for dissolving, the ozone gas generating means 5 for generating ozone gas, the ozone gas generated from the ozone gas generating means 5 is brought into contact with the water to be treated in which the first hydrogen peroxide is dissolved, and ozone is The ozone dissolving means 6 for dissolving, the water to be treated in which the first hydrogen peroxide and ozone are dissolved are introduced, and the reaction vessel 7 for oxidizing and decomposing organic substances contained in the water to be treated is discharged from the reaction vessel 7. Circulation means 22 for circulating the water to be treated to the reaction vessel 7 and second hydrogen peroxide addition means for adding further second hydrogen peroxide to the circulation water at the subsequent stage of the reaction vessel 7 (in the middle of the circulation means 22). 23 and the second peracid A treated water tank 9 for storing treated water treated in the reaction vessel 7 to which hydrogen has been added, and a waste ozone treatment means 10 for treating waste ozone gas discharged from the reaction vessel 7 and the treated water tank 9 are configured. Is.

  In this embodiment, the circulation means 22 is configured to be branched into a branch line 22 a and a branch line 22 b in the middle, and each of the branched pipes is configured to circulate the water to be treated to the reaction vessel 7. Yes. At this time, it is preferable to circulate the branch line 22a at different positions so that the branch line 22a is circulated from the outlet of the reaction vessel and the branch line 22b is circulated from the inlet of the reaction vessel. For example, the dividing position when the 1/3 dividing point of the reaction vessel, that is, the length from the inlet to the outlet of the reaction vessel 7 is equally divided into three (22b is 1/3 of the vessel length from the inlet toward the outlet). It can be considered that the circulating water is supplied at the position 22a from the outlet toward the inlet side at a position 1/3 of the container length).

  The second hydrogen peroxide addition means 23 adds hydrogen peroxide only to the circulation means 22a. This is because the circulating water to the subsequent stage is more passed in the flow path of the reaction vessel 7. This is because a high hydrogen oxide concentration is preferable in terms of promoting the reaction. When the hydrogen peroxide concentration is increased at the subsequent stage of the reaction vessel 7 in this way, the water to be treated (circulated water) that has left the reaction vessel 7 and entered the circulation means 22 is subjected to a relatively high concentration of peroxide. Since hydrogen remains, a sufficient reaction occurs even if the circulating water is supplied as it is, and a higher concentration of hydrogen peroxide is supplied at the supply position of the subsequent circulation means 22a. This is because the reaction can be performed in the entire container 7 and the processing can be performed efficiently.

  However, here, the second hydrogen peroxide addition means 23 may add hydrogen peroxide to both the circulation means 22a and 22b, or the circulation means 32 may be branched as shown in FIG. Hydrogen peroxide may be added before the treatment, and the water to be treated with the second hydrogen peroxide added may be introduced at a different location in the reaction vessel 7. 4 is different from the water treatment device 21 in FIG. 3 only in the hydrogen peroxide addition position by the second hydrogen peroxide addition means 33, and the other configuration is the same (circulation). The means 32 also corresponds to the circulation means 22).

In such a configuration, the addition of hydrogen peroxide is performed in two stages, but the state can be substantially performed in three stages. Further, for example, when a plurality of reaction vessels 7 are provided in parallel, in the first embodiment, it is necessary to provide as many drug injection pumps as the number of reaction vessels. As a result, it is possible to confirm the concentration of hydrogen peroxide in one place, and the operation is simple.
In this embodiment, although the case where the injection | pouring position of the circulating water to a reaction container is two places was demonstrated, this injection | pouring position can also be made into three or more places. When the injection position is set to n places in this way (n is an integer equal to or greater than 1), the injection position in the reaction vessel is divided when the length of the reaction vessel is equally divided by 1 / (n + 1). It is preferable to set the point.

  Hereinafter, the present invention will be described by reference examples, examples and comparative examples. Note that the present invention is not limited to these descriptions.

Example 1
In the water treatment apparatus shown in FIG. 1, the treatment was performed using an apparatus provided with a mixed bed type ion exchange resin in the subsequent stage of the reaction vessel.

  First, a surfactant (manufactured by Wako Pure Chemical Industries, Ltd., trade name: NCW-1001) was added to pure water to adjust the carbon concentration to 20 ppm, which was treated water.

While flowing this treated water into the pipe (caliber: 80A) at a flow rate of 0.35 m ³ / hr, it was injected using a chemical injection pump so that the injection rate of the first hydrogen peroxide was 20 ppm, The ozone gas obtained by the ozone generating means was brought into contact with the water to be treated by an ejector (caliber: 15A, material: SUS316, nozzle diameter: 3.5 mm, throat diameter: 6.8 mm) to dissolve ozone. At this time, the ozone injection rate was set to 250 ppm.

  Water to be treated in which first hydrogen peroxide and ozone gas are dissolved is introduced into a reaction vessel having a diameter of 80 × 3400 mm in an upward flow to cause an oxidative decomposition reaction of organic substances in the water to be treated. Hydrogen peroxide was injected so that the injection rate was 20 ppm, and the oxidative decomposition reaction of organic matter was further promoted. At this time, the second hydrogen peroxide was injected at a position 1700 mm from the reaction vessel inlet. At this time, the residence time of the water to be treated was about 3 minutes.

  The treated water discharged from the reaction vessel was further passed through a mixed bed type ion exchange resin (Rohm and Haas, model: MBGP) to remove organic substances and obtain pure water. The treatment conditions and the TOC concentration of the treated water at this time are shown in Table 1, respectively.

(Examples 2 to 4)
Using the same water treatment apparatus as in Example 1, treatment was carried out by the same operation. Here, the treatment conditions and the TOC concentration of the treated water in Examples 2 to 4 are shown in Table 1, respectively.

(Example 5)
In the water treatment apparatus shown in FIG. 2, the treatment was performed using an apparatus provided with a mixed bed type ion exchange resin in the subsequent stage of the reaction vessel.

  First, a surfactant (manufactured by Wako Pure Chemical Industries, Ltd., trade name: NCW-1001) was added to pure water to adjust the carbon concentration to 20 ppm, which was treated water.

While flowing this treated water into the pipe (caliber: 80A) at a flow rate of 0.35 m ³ / hr, it was injected using a chemical injection pump so that the injection rate of the first hydrogen peroxide was 10 ppm, The ozone gas obtained by the ozone generating means was brought into contact with the water to be treated by an ejector (caliber: 15A, material: SUS316, nozzle diameter: 3.5 mm, throat diameter: 6.8 mm) to dissolve ozone. At this time, ozone was injected so that the injection rate was 175 ppm.

  The water to be treated in which the first hydrogen peroxide and ozone gas were dissolved was introduced into a reaction vessel having a diameter of 80 × 3400 mm in an upward flow to cause an oxidative decomposition reaction of organic substances in the water to be treated. At this time, the residence time of the water to be treated was about 3 minutes.

Injected into the water to be treated discharged from the reaction vessel so that the injection rate of the second hydrogen peroxide is 30 ppm, this was introduced into the reaction vessel at a position of about 1700 mm from the reaction vessel inlet, It was circulated to further promote the oxidative decomposition reaction of organic matter (second organic matter decomposition reaction). The flow rate of the treated water circulated at this time was set to 0.11 m ³ / hr.

  The treated water that had been subjected to the second organic matter decomposition reaction was further passed through a mixed bed type ion exchange resin (Rohm and Haas, model: MBGP) to remove the organic matter and obtain pure water. The treatment conditions and the TOC concentration of the treated water at this time are shown in Table 1, respectively.

(Example 6)
In the water treatment apparatus shown in FIG. 3, treatment was performed by the same operation as in Example 5 using an apparatus in which a mixed bed type ion exchange resin was provided in the subsequent stage of the reaction vessel.

The water to be treated is circulated at a position where the supply of the circulating water by the branch line 22b is about 1100 mm from the inlet of the reaction vessel 7 and the supply of the circulating water by the branch line 23a is about 2200 mm from the inlet of the reaction vessel 7, respectively. I did it. Here, the flow rate of the treated water circulated at this time was set to 0.11 m ³ / hr in each of the branch lines 22a and 22b. The treatment conditions and the TOC concentration of the treated water at this time are shown in Table 1, respectively.

(Example 7)
In the water treatment apparatus shown in FIG. 4, treatment was performed by the same operation as in Example 6 using an apparatus in which a mixed bed type ion exchange resin was provided in the subsequent stage of the reaction vessel. Here, the flow rate of the treated water circulated at this time was set to 0.11 m ³ / hr in each of the branch lines 32a and 32b. The treatment conditions and the TOC concentration of the treated water at this time are shown in Table 1, respectively.

(Comparative Examples 1-4)
In the water treatment apparatus shown in FIG. 5, the treatment was performed by the same operation as in Example 1 except that the apparatus in which the mixed bed type ion exchange resin was provided at the rear stage of the reaction vessel and the second hydrogen peroxide was not added. went. The injection rates of hydrogen peroxide to be added were 20 ppm (Comparative Example 1), 40 ppm (Comparative Example 2), and 80 ppm (Comparative Example 3), respectively. 5 has the same configuration as that of the water treatment apparatus of FIG. 1 except that the second hydrogen peroxide addition means 8 is not provided.

  Moreover, the example which performed operation same as the comparative example 2 was made into the comparative example 4 except the injection rate of ozone having been 175 ppm. The treatment conditions and the TOC concentration of the treated water at this time are shown in Table 2, respectively.

* 1: The ozone injection rate (ppm) was obtained by ozone gas concentration (g-O ₃ / Nm ³ ) × ozone gas flow rate (Nm ³ / hr) ÷ treatment flow rate (m ³ / hr). Here, the ozone gas concentration was measured with an ozone concentration meter (manufactured by Ebara Jitsugyo Co., Ltd., model: EG-600).
* 2: The hydrogen peroxide injection rate (ppm) was obtained by hydrogen peroxide addition amount (g-H ₂ O ₂ / hr) ÷ treatment flow rate (m ³ / hr).
* 3: The TOC concentration (ppm) was measured using a model: TOC-810 manufactured by Sievers after sampling in a beaker.
* 4: For the ozone concentration (ppm), an ozone concentration meter (manufactured by Hack Ultra Analytics Co., Ltd., model: orbisphere MOCA3600) was installed in the water treatment apparatus, and the dissolved ozone concentration was measured online.

It is the figure which showed the structure of the water treatment apparatus in the 1st Embodiment of this invention. It is the figure which showed the structure of the water treatment apparatus in the 2nd Embodiment of this invention. It is the figure which showed the structure of the water treatment apparatus in the 3rd Embodiment of this invention. It is the figure which showed the structure of the modification of the water treatment apparatus in the 3rd Embodiment of this invention. It is the figure which showed the structure of the water treatment apparatus used by the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Water treatment apparatus, 2 ... Water tank to be treated, 3 ... pH adjustment means, 4 ... First hydrogen peroxide addition means, 5 ... Ozone generation means, 6 ... Ozone dissolution means, 7 ... Reaction vessel, 8 ... First 2 hydrogen peroxide addition means, 9 ... treated water tank, 10 ... waste ozone treatment means, 11, 21, 31 ... water treatment device, 12, 22, 32 ... circulation means, 13, 23, 33 ... second excess Hydrogen oxide addition means

Claims (9)

A first hydrogen peroxide addition step of adding and dissolving the first hydrogen peroxide in the water to be treated;
An ozone dissolving step of bringing ozone gas into contact with the water to be treated in which the first hydrogen peroxide is dissolved to dissolve ozone;
A first organic matter decomposition step of introducing water to be treated in which the first hydrogen peroxide and the ozone gas are dissolved into a cylindrical reaction vessel to oxidatively decompose organic substances contained in the water to be treated without irradiating ultraviolet rays. When,
A second hydrogen peroxide addition step of adding a second hydrogen peroxide into the reaction vessel when performing the first organic matter decomposition step;
A second organic matter decomposition step of further oxidizing and decomposing organic matter in the water to be treated without irradiating ultraviolet rays by adding the second hydrogen peroxide;
A water treatment method characterized by comprising: A first hydrogen peroxide addition step of adding and dissolving the first hydrogen peroxide in the water to be treated;
An ozone dissolving step of bringing ozone gas into contact with the water to be treated in which the first hydrogen peroxide is dissolved to dissolve ozone;
A first organic matter decomposition step of introducing water to be treated in which the first hydrogen peroxide and the ozone gas are dissolved into a cylindrical reaction vessel to oxidatively decompose organic substances contained in the water to be treated without irradiating ultraviolet rays. When,
A second hydrogen peroxide addition step of adding a second hydrogen peroxide to the water to be treated and circulating it directly to the reaction vessel after the first organic matter decomposition step;
A second organic matter decomposition step of further oxidizing and decomposing organic matter in the water to be treated without irradiating ultraviolet rays by adding the second hydrogen peroxide;
A water treatment method characterized by comprising: The flow of water to be treated in the reaction vessel is an upward flow,
After the addition of the second hydrogen peroxide in the reaction vessel or the first organic matter decomposition step, the addition of water to be treated in which the second hydrogen peroxide is dissolved by circulation to the reaction vessel The water treatment method according to claim 1 or 2, wherein the water treatment method is carried out by introducing in a direction facing the flow of water to be treated in the container.   The oxidant removal step of removing ozone and hydrogen peroxide by passing treated water through activated carbon after the first organic matter decomposition step and / or the second organic matter decomposition step is performed. 4. The water treatment method according to any one of 3 above.   When the ozone injection rate in the ozone dissolution step is 1, the hydrogen peroxide injection rate in the first hydrogen peroxide addition step is 0.04 to 0.12, and the second hydrogen peroxide addition step The water treatment method according to any one of claims 1 to 4, wherein a hydrogen peroxide injection rate in said step is 2 to 6 times a hydrogen peroxide injection rate in said first hydrogen peroxide addition step. First hydrogen peroxide addition means for adding and dissolving the first hydrogen peroxide in the water to be treated;
Ozone gas generating means for generating ozone gas;
Ozone treatment means for dissolving ozone by bringing ozone gas generated from the ozone gas generation means into contact with water to be treated in which the first hydrogen peroxide is dissolved;
A cylindrical reaction vessel that introduces water to be treated in which the first hydrogen peroxide and ozone are dissolved and oxidatively decomposes organic substances contained in the water to be treated without irradiating ultraviolet rays ;
Second hydrogen peroxide addition means for adding second hydrogen peroxide to the water to be treated in the reaction vessel;
A water treatment apparatus comprising: First hydrogen peroxide addition means for adding and dissolving the first hydrogen peroxide in the water to be treated;
Ozone gas generating means for generating ozone gas;
Ozone treatment means for dissolving ozone by bringing ozone gas generated from the ozone gas generation means into contact with water to be treated in which the first hydrogen peroxide is dissolved;
A cylindrical reaction vessel that introduces water to be treated in which the first hydrogen peroxide and ozone are dissolved and oxidatively decomposes organic substances contained in the water to be treated without irradiating ultraviolet rays ;
A second hydrogen peroxide addition means for adding the second hydrogen peroxide to the water to be treated at a subsequent stage of the reaction vessel;
A water treatment apparatus comprising: circulation means for directly circulating the water to be treated to the reaction vessel after the addition of the second hydrogen peroxide.   The water treatment apparatus according to claim 6 or 7, wherein activated carbon for removing ozone and hydrogen peroxide from the water to be treated discharged from the reaction vessel is provided at a subsequent stage of the reaction vessel.   The water treatment apparatus according to any one of claims 6 to 8, wherein the reaction vessel is provided so that the flow of water to be treated is an upward flow.

Images