JP2001212597A - Method and apparatus for treating wastewater containing sulfoxide compounds - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat wastewater containing sulfoxide compounds efficiently by preventing the lowering of bioactivity when the wastewater is oxidized to oxidize the sulfoxide compounds to sulfone or sulfonic acid compounds and then subjected to biotreatment to decompose/remove the sulfoxide compounds. SOLUTION: After the wastewater containing sulfoxide compounds is oxidized, residual oxidizable substances are removed, and the water is subjected to biotreatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating wastewater containing sulfoxides such as dimethyl sulfoxide (DMSO) discharged from a semiconductor manufacturing plant or the like, and more particularly to a method for treating wastewater containing sulfoxides after oxidizing the wastewater. The present invention relates to a method and an apparatus for efficiently decomposing and removing sulfoxides by biological treatment.

[0002]

2. Description of the Related Art In recent years, DMSO has been widely used in semiconductor manufacturing factories and liquid crystal panel manufacturing factories, and the treatment of wastewater containing sulfoxides such as DMSO has become important.

Conventionally, as a method of treating sulfoxide-containing wastewater, a method of biodegrading sulfoxides under aerobic conditions is known. However, in this method, it is difficult to maintain the inside of a biological reaction tank under aerobic conditions. There is a problem that biodegradation occurs partially under anaerobic conditions, and toxic odorous substances such as methyl mercaptan (CH ₃ SH: MM) and hydrogen sulfide (H ₂ S) are generated by the anaerobic decomposition.

As a countermeasure, a method has been proposed in which a sulfoxide is oxidized to a sulfone or a sulfonic acid and then subjected to biological treatment (Japanese Patent Nos. 2730513 and 2792481). Generation of malodorous substances in the tank is suppressed.

[0005]

However, in the treatment of sulfoxides, if an oxidation treatment is performed as a pretreatment for biological treatment, the biological activity in the biological reaction tank is reduced, and the removal of sulfones and the like is deteriorated. There was a problem. And when designing the device in anticipation of this decrease in biological activity,
Since the size of the biological reaction tank is increased, the installation space for the apparatus is increased; and the energy cost of aeration is increased.

The present invention is intended to prevent a decrease in biological activity in chemical decomposition of a sulfoxide-containing wastewater to oxidize the sulfoxides contained therein to sulfones and sulfonic acids and then subjecting them to biological treatment to decompose and remove them. It is an object of the present invention to provide a method and apparatus for performing efficient and efficient processing.

[0007]

According to the present invention, there is provided a method for treating a sulfoxide-containing wastewater, comprising: a first step of chemically oxidizing the sulfoxide-containing wastewater; The method is characterized by comprising a second step of removing oxidizing substances contained in the treated water of the step, and a third step of biologically treating the treated water of the second step.

[0008] The apparatus for treating sulfoxide-containing wastewater according to the present invention is a device for treating sulfoxide-containing wastewater, wherein the first means for chemically oxidizing the sulfoxide-containing wastewater and the first treatment means contain- ing the treated water. A second means for removing the oxidizing substance to be removed, and a third means for biologically treating the treated water of the second means.

[0009] The present inventors have studied the cause of a decrease in biological activity when chemical oxidation is performed as a pretreatment for biological treatment. As a result, the oxidizing substance (hereinafter referred to as “oxidizing agent”) used in chemical oxidation is considered. ) Flows into the biological treatment step, and it has been found that the biological activity is reduced by the residual oxidizing agent.

In the present invention, prior to the biological treatment, the residual oxidant flowing out of the chemical oxidation treatment step is removed, so that a decrease in biological activity due to the flow of the residual oxidant into the biological treatment step is prevented.

In the present invention, the chemical oxidation step or means may be any one having a strong oxidizing power capable of oxidizing sulfoxides to sulfones and sulfonic acids, such as ozone (O ₃ ) and hydrogen peroxide (H ₂ O ₂ ), sodium hypochlorite (NaClO) or other oxidizing agent addition step or means. Ultraviolet (UV) irradiation step or means. Catalytic oxidation step or means. Electrolytic oxidation step or means.

In the present invention, sulfoxides are oxidized to sulfonic acids or sulfonic acids in advance by chemical oxidation prior to biological treatment, so that the oxidation treatment capacity is weak as in the so-called Fenton treatment. DMS
It does not include treatments that cannot oxidize sulfoxides such as O to sulfones or sulfonic acids.

The oxidizing agent removing step or means includes a reducing agent adding step or means a reducing step or means using a catalyst such as activated carbon or the like. A reducing step or means using a metal or an ion exchange step or means using an anion exchange resin.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a method and apparatus for treating sulfoxide-containing wastewater of the present invention will be described in detail.

The sulfoxides of the sulfoxide-containing wastewater treated by the method and apparatus of the present invention include DMS.
O, alkyl sulfoxides such as diethyl sulfoxide,
And sulfoxides such as diphenylsulfoxide. In the present invention, these sulfoxides, for example, DMSO are converted to dimethyl sulfone (D
MSO ₂ ) to methanesulfonic acid (MSA), and these DMSO ₂ and MSA are converted to sulfuric acid,
Decomposes into carbon dioxide and water.

The concentration of sulfoxides in such a sulfoxide-containing wastewater is not particularly limited, but the present invention is generally effective for wastewater having a sulfoxide concentration of about 2 mg / L to about 10% by weight.

In the present invention, as the chemical oxidation step or means, an oxidizing agent such as ozone (O ₃ ), hydrogen peroxide (H ₂ O ₂ ), sodium hypochlorite (NaClO) or the like is used. ) Irradiation step or means Catalytic oxidation step or means Electrolytic oxidation step or means. These may be employed in combination of a plurality of types, and in such a chemical oxidation treatment, it is preferable to adjust each to a suitable pH, and it is further preferable to heat to an appropriate temperature as needed. .

Further, as an oxidizing agent removing step or means,
Is a sodium sulfite (Na₂SO₃), Bisulfite
Thorium (NaHSO ₃), Etc., sulfites, nitrites, 2
Reducing metal salt such as ferrous salt, reducing agent such as hydrogen
Or a reduction step with a catalyst such as activated carbon or a reduction step with a metal.An ion exchange step or a means with an anion exchange resin.
The pH may be adjusted if necessary, but in general,
Treatment of chemically oxidized water without adjusting pH
It is possible. However, heating in the chemical oxidation process
If performed, the temperature is preferably lowered.

The biological treatment step or means is not particularly limited, and ordinary activated sludge treatment can be performed.
The treatment conditions are appropriately determined according to the properties of the wastewater. The pH condition of this biological treatment is preferably about 4 to 9. Therefore, when the pH of the water after removing the oxidizing agent is out of this range, a pH adjusting tank is provided before the biological treatment tank to adjust the pH. Is preferably performed.

When a reducing agent is added as an oxidizing agent removing treatment, if the reducing agent is added in excess, the sulfones and sulfonic acids generated by the oxidation of the sulfoxides in the chemical oxidation treatment are also reduced to the sulfoxides, resulting in malodor. In addition, if the reducing agent becomes excessive, it may be reduced to odorous sulfides. Therefore, when a reducing agent is used, an ORP meter or an oxidizing agent monitor monitors the amount of the reducing agent. It is preferable to appropriately adjust the addition amount so as not to be excessive.

Therefore, from the viewpoint of avoiding the problem of such an excessive addition, as a means for removing the oxidizing agent, a method using a catalyst in which only the oxidizing agent self-decomposes or a method using a metal utilizing the reaction between the metal and the oxidizing agent are used. And other methods using an anion exchange resin.

In the present invention, the acid or alkali for adjusting pH is not particularly limited, but the acid may be HCl or H _2.
SO ₄ , HNO ₃ , HF, and the like can be used. As the alkali, NaOH, Ca (OH) ₂ , Al (O
H) ₃ , Mg (OH) ₂ , KOH and the like can be used.

When a gaseous oxidizing agent or reducing agent is used, a gas-liquid mixer may be used as appropriate. In this case, the gas-liquid mixer used is not particularly limited. A gas-liquid stirring pump, an ejector, a line mixer, and the like, a dissolving film, a pressure dissolving device, and the like can be used.

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

1 to 4 are system diagrams showing an embodiment of a method and an apparatus for treating sulfoxide-containing waste water according to the present invention. 1 to 4, members having the same function are denoted by the same reference numerals.

FIG. 1 shows a process in which H ₂ O ₂ and O ₃ are used together as a chemical oxidation process, and an activated carbon process as an oxidizing agent removing process.

The effluent is added with H ₂ O ₂ and pH.
After adjusting the pH to about 2 to 12 with a regulator, the mixture is introduced into the ozone treatment tank 1 and oxidized. Here, the addition of the pH adjuster is controlled based on the measured value of the pH meter 1A. H ₂ O
Injection volume of ₂ and ozone are appropriately determined according to the sulfoxides concentration in the wastewater, usually, the H ₂ O ₂ 0.1 to 5 times the weight of the sulfoxides concentration, the O ₃ sulfoxides concentration 0 It is preferable that the amount be 0.5 to 10 times by weight.

The treated water in the ozone treatment tank 1 is then introduced into the activated carbon tower 2 to decompose and remove the residual oxidant by activated carbon.

The water from which the oxidizing agent has been removed in the activated carbon tower 2 is then pH-adjusted in a pH adjusting tank 3 by adding a pH adjusting agent based on a pH meter 3A. Get.

FIG. 2 shows a case where a treatment using both H ₂ O ₂ and UV is employed as the chemical oxidation treatment, and a reducing agent (NaHSO ₃ ) is added as the oxidant removal treatment.

H ₂ O ₂ was added to the waste water, and the pH was adjusted.
After adjusting the pH to about 2 to 12 with an adjusting agent, the mixture is introduced into the UV irradiation device 5 and oxidized. Here, the addition of the pH adjuster is controlled based on the measured value of the pH meter 5A. H ₂ O
_{2 The} injection amount and the UV irradiation amount are appropriately determined according to the concentration of sulfoxides in the wastewater, and it is generally preferable to make H ₂ O ₂ 0.5 to 10 times the weight of the concentration of sulfoxides.

The treated water UV irradiation device 5 is then introduced into a reducing agent the reaction vessel 6, the NaHSO ₃ residual oxidant (H
₂ O ₂ ) is decomposed and removed. This NaHSO ₃ is H ₂ O ₂
The addition is controlled based on a total of 6A.

The water from which the oxidizing agent has been removed in the reducing agent reactor 6 is
Next, the pH is adjusted by adding a pH adjusting agent based on the pH meter 3A in the pH adjusting tank 3 and then biologically treated in the biological reaction tank 4 to obtain treated water.

FIG. 3 shows a case where a treatment using both H ₂ O ₂ and heating is employed as the chemical oxidation treatment, and an anion exchange treatment is employed as the oxidizing agent removing treatment.

The waste water is discharged from the H ₂ O ₂ oxidation reaction tank 7 to the H ₂ O ₂
And adjust the pH to about 7 to 13 with a pH adjuster.
Adjust H and heat with steam. Here, the addition of the pH adjuster is controlled based on the measured value of the pH meter 7A. H ₂ O ₂
And the heating temperature are appropriately determined according to the concentration of sulfoxides in the wastewater. In general, H ₂ O ₂ is 0.5 to 10 times the concentration of sulfoxides, and the heating temperature is 40 to 40 times.
Preferably, the temperature is 95 ° C.

The treated water in the H ₂ O ₂ oxidation reaction tank 7 is cooled to about 10 to 40 ° C. in the heat exchanger 8 and then introduced into the anion exchange resin tower 9 to remove the residual oxidant by anion exchange treatment. .

The water from which the oxidizing agent has been removed in the anion exchange resin tower 9 is then pH-adjusted in the pH adjusting tank 3 by adding a pH adjusting agent based on a pH meter 3A.
Biological treatment to obtain treated water.

FIG. 4 shows a case where a treatment using both H ₂ O ₂ and a catalyst (a vanadium ion catalyst) is employed as the chemical oxidation treatment, and an activated carbon treatment is employed as the oxidizing agent removal treatment.

The waste water is supplied to the H ₂ O ₂ oxidation reaction tank 7 with H ₂ O ₂
And a vanadium ion catalyst are added, and the pH is adjusted to about pH 1 to about 12 with a pH adjuster to perform an oxidation treatment.
Here, the addition of the pH adjuster is controlled based on the measured value of the pH meter 7A. The adjusted pH is preferably 5 or less, particularly preferably in the range of 1 to 4. The injection amount of H ₂ O ₂ is appropriately determined according to the sulfoxide concentration in the wastewater.
It is preferable that H ₂ O _{2 is set} to 0.5 to 10 times by weight of the sulfoxide concentration. The heating temperature by steam is 4
The temperature is preferably from 0 to 95 ° C.

Examples of the vanadium source include metal vanadium, vanadium pentoxide, vanadium oxychloride, vanadium trichloride, and ammonium metavanadate. These can be converted into pentavalent vanadium ions.

The treated water in the H ₂ O ₂ oxidation reaction tank 7 is cooled to 10 to 70 ° C. in the heat exchanger 8 and then introduced into the activated carbon tower 2 to decompose and remove the residual oxidizing agent by activated carbon.

The water from which the oxidizing agent has been removed in the activated carbon tower 2 is then adjusted to a pH of about 4 to 10 based on a pH meter 10A by adding a pH adjuster in a coagulation tank 10 and a ferrous salt is added. To precipitate a hydroxide coprecipitate of vanadium and iron to recover a vanadium ion catalyst. Here, as the ferrous salt, FeSO ₄ , FeCl ₂ , Fe (OH) ₂ or the like can be used, and the addition amount thereof is a stoichiometric amount with respect to the vanadium ion catalyst (that is, 1 mol with respect to vanadium). Equivalent) or more, but usually, 60 to 120% by weight of Fe is added to the vanadium ion catalyst. As a result, vanadium of the vanadium ion catalyst is reduced to tetravalent, and precipitates as a coprecipitate of hydroxide with iron.
The coagulation liquid in the coagulation tank 10 is then introduced into the sedimentation tank 11 to be separated into a solid and a liquid, whereby the sludge containing Fe and V is separated.

The separated liquid in the sedimentation tank 11 is then adjusted in pH by adding a pH adjuster based on a pH meter 3A in the pH adjuster 3 and then biologically treated in the biological reactor 4 to obtain treated water.

[0044]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1, Comparative Example 2 Wastewater containing DMSO (DMSO concentration 500 ppm, pH
5.5) was processed in the apparatus shown in FIG.

The ozone oxidation conditions in the ozone treatment tank 1 are as follows.
The pH was adjusted to 7 in the pH adjustment tank 3 as follows.
Was. [Ozone oxidation conditions] O₃Addition amount: 1kg-O₃/ M³  H₂O₂Addition amount: 5kg-35% H₂O₂/ M³  pH: 9 Ozone treatment tank 1, activated carbon tower 2, pH adjustment tank 3, and biological counter
Compared to Example 1 in which water was sequentially passed through the reaction tank 4, Comparative Example 1
, Omit the activated carbon tower 2, ozone treatment tank 1, pH adjustment tank 3
Then, water was passed in the order of the biological reaction tank 4 for treatment.

The quality of the treated water in the biological reaction tank 4 was examined, and the results are shown in Table 1.

[0048]

[Table 1]

Example 2, Comparative Example 2 Wastewater containing DMSO (DMSO concentration 300 ppm, pH
4.2) was processed in the apparatus shown in FIG.

The amount of H ₂ O ₂ added at the entrance of the UV irradiation device 5 was 2 kg-35% H ₂ O ₂ / m ³ , and the adjusted pH was 9;
In the reducing agent reaction tank 6, the amount of NaHSO ₃ added was controlled by a H ₂ O ₂ meter, and added so that residual H ₂ O ₂ was not detected. The adjusted pH in the pH adjusting tank 3 was set to 7.

In contrast to Example 2 in which water was sequentially passed through the UV irradiation device 5, the reducing agent reaction tank 6, the pH adjusting tank 3, and the biological reaction tank 4, in Comparative Example 2, the reducing agent reaction tank 6 was omitted, and UV irradiation was performed. Water was passed through the apparatus 5, the pH adjusting tank 3, and the biological reaction tank 4 in this order to perform treatment.

The quality of the treated water in the biological reaction tank 4 was examined, and the results are shown in Table 2.

[0053]

[Table 2]

Example 3, Comparative Example 3 Wastewater containing DMSO (DMSO concentration 5000 ppm, pH
6.8) was processed in the apparatus shown in FIG.

H₂O₂H in the oxidation reaction tank 7₂O₂acid
The reaction conditions were as follows, and after the reaction, the temperature was lowered to 20 ° C.
The pH adjusted in the pH adjusting tank 3 was set to 7. [H₂O₂Oxidation conditions] H₂O₂Addition amount: 1kg-35% H₂O₂/ M³  Concentration: 70 ° C pH: 10 H₂O₂Oxidation reaction tank 7, anion exchange resin tower 9, pH adjustment
For Example 3 in which water was sequentially passed through the water tank 3 and the biological reaction tank 4
Thus, in Comparative Example 3, the anion exchange resin tower 9 was omitted and H₂
O₂Oxidation reaction tank 7, pH adjustment tank 3, and biological reaction tank 4 in this order
For water treatment.

The quality of the treated water in the biological reaction tank 4 was examined, and the results are shown in Table 3.

[0057]

[Table 3]

Example 4, Comparative Example 4 DMSO-containing wastewater (DMSO concentration 350 ppm, pH
5.5) was processed in the apparatus shown in FIG.

H₂O₂H in the oxidation reaction tank 7₂O₂acid
And the coagulation conditions in the coagulation tank 10 are as follows:
The pH adjusted in the pH adjusting tank 3 was set to 7. [H₂O₂Oxidation conditions] H₂O₂Addition amount: 2kg-35% H₂O₂/ M³  V₂O₅Addition amount: 1000 mg-V₂O₅/ L Temperature: 80 ° C pH: 3 [Aggregation conditions] FeCl₂Addition amount: 7000 mg / L pH: 10 H₂O₂Oxidation reaction tank 7, activated carbon tower 2, coagulation tank 10, sedimentation
Water was sequentially passed through the tank 11, the pH adjustment tank 3, and the biological reaction tank 4.
In contrast to Example 4, in Comparative Example 4, the activated carbon tower 2 was omitted,
H₂O₂Oxidation reaction tank 7, coagulation tank 10, sedimentation tank 11, pH
Water was passed in the order of the adjusting tank 3 and the biological reaction tank 4 for treatment.

The quality of the treated water in the biological reaction tank 4 was examined, and the results are shown in Table 4.

[0061]

[Table 4]

From Tables 1 to 4, it can be seen that according to the present invention, DMSO ₂ is highly removed in the biological reaction tank, and high-quality treated water can be obtained.

[0063]

As described above in detail, according to the method and apparatus for treating sulfoxide-containing wastewater of the present invention, chemical oxidation is performed prior to biological treatment, so that the generation of toxic malodorous substances in a biological reaction tank is prevented. be able to. The flow of the residual oxidant into the biological reaction tank and the decrease in biological activity due to the flow of the oxidant are prevented, and the biological treatment efficiency is improved. The capacity of the biological reaction tank can be reduced, the size of the equipment can be reduced, the installation space can be saved, the energy cost for aeration can be reduced, and the quality of the obtained treated water can be improved. Thus, the sulfoxide-containing wastewater can be efficiently treated at low cost.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a method and an apparatus for treating sulfoxide-containing wastewater of the present invention.

FIG. 2 is a system diagram showing another embodiment of the method and the apparatus for treating sulfoxide-containing wastewater of the present invention.

FIG. 3 is a system diagram showing another embodiment of the method and the apparatus for treating sulfoxide-containing wastewater of the present invention.

FIG. 4 is a system diagram showing different embodiments of a method and an apparatus for treating sulfoxide-containing wastewater of the present invention.

[Explanation of symbols]

1 ozone treatment vessel 2 activated carbon tower 3 pH adjusting tank 4 bioreactor 5 UV irradiation device 6 reductant reaction tank 7 H ₂ O ₂ oxidation reaction vessel 8 heat exchanger 9 the anion exchange resin column 10 flocculation tank 11 sedimentation tank

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Claims (2)

[Claims] 1. A method for treating a sulfoxide-containing wastewater, comprising: a first step of chemically oxidizing the sulfoxide-containing wastewater; and a second step of removing an oxidizing substance contained in the treated water of the first step. A method for treating wastewater containing sulfoxides, comprising: a step; and a third step of biologically treating the treated water in the second step. 2. An apparatus for treating a sulfoxide-containing wastewater, comprising: first means for chemically oxidizing the sulfoxide-containing wastewater; and second means for removing an oxidizing substance contained in the treated water of the first means. And a third means for subjecting the treated water of the second means to biological treatment.