JPH06262188A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To efficiency perform a purification treatment of waste water by performing a wet oxidation treatment of the waste water incorporating S and/or a sulfur compound of low-class iron oxide so as to satisfy each of conditions for respectively specific temp., pressure and pH of the treating liquid under supply of gas incorporating oxygen. CONSTITUTION:The waste water incorporating sulfur and/or the sulfur compound of low-class iron oxide is subjected to a wet oxidation treatment so as to satisfy the conditions of temperature being at 110-370 deg.C, the pressure maintaining the waste water in liquid phase and >=5 of the pH of the treating liquid under supply of the gas incorporating oxygen. At this time, at first the waste water in a line 9 is pressurized with a pump 3, and also NaOH in a line 10 is pressurized with a pump 4 and the gas incorporating oxygen in a line 11 is pressurized with a compressor 6. next the gas liquid mixture is fed to a heat exchanger 2 from a line 12 and is heated and then is introduced to a wet oxidation reaction tower 1 to perform wet oxidation treatment. Subsequently the treated water is fed to the heat exchanger 2 from a line 13, and is cooled and then is introduced to a gas liquid separator 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying waste water discharged from various industrial plants such as chemical plants, food processing equipment, metal processing equipment, metal plating equipment and printing plate making equipment by a wet oxidation method. More specifically, high chemical oxygen demand (hereinafter also referred to as "COD")
Which is a wet oxidation method of wastewater containing sulfur and / or a sulfur compound having a lower oxidation number (hereinafter, also referred to as “sulfur etc.”), and further includes heavy metals, aluminum, phosphorus,
The present invention relates to a method for purifying wastewater containing silicon, calcium, magnesium or the like by a wet oxidation treatment method.

[0002]

2. Description of the Related Art Conventionally, when a wastewater containing sulfur and / or a sulfur compound having a lower oxidation number is subjected to a wet oxidation treatment in a wet oxidation treatment method, the treated water after the wet oxidation treatment is treated with sulfur, Since many of the sulfur compounds with a lower oxidation number are oxidized or oxidatively decomposed into sulfate ions, the pH of the treated water generally lowers, often resulting in a strongly acidic treatment liquid. For example, sulfur and sulfur with a lower oxidation number. When the waste water containing the compound is subjected to the wet oxidation treatment under the condition that the pH after treatment is less than 5, there is a problem that the exhaust gas after the treatment produces an odor similar to the smell of hydrogen sulfide. Therefore, exhaust gas dilution,
Various measures such as purification are required, for example, a method of diluting exhaust gas with air, a method of adsorbing and removing odorous components with activated carbon, a method of oxidizing and decomposing odorous components with ozone, and a method of purifying odorous components with a catalyst. Methods etc. have been proposed.

In addition, heavy metals, aluminum, phosphorus, silicon, calcium, magnesium and the like components that easily form scales (hereinafter also referred to as "scale-forming substances").
When the wastewater containing the is subjected to a wet oxidation treatment, there is a problem that scale adheres to the heat exchanger, the reaction tower, the packing, the catalyst and the like. Therefore, various methods, for example, (i) a method of adding an additive or the like to waste water to make it difficult to generate scale, (ii) a method of removing adhered scale by using a cleaning agent, (iii) waste water by pretreatment There have been implemented or proposed methods such as removing the scale-forming substance in the inside to prevent the scale from being generated, and (iv) improving the system such as an apparatus to make it difficult for the scale to adhere.

However, the above method is often inadequate, and when the waste water containing the scale-forming substance and sulfur etc. is subjected to the wet oxidation treatment, the adhesion of scale is particularly remarkable.

[0005]

When the above-mentioned methods are used, there are many problems as described below, and any of the methods needs improvement. Countermeasures for deodorization are secondary treatment equipment different from the original wastewater treatment,
It is more preferable in terms of equipment that the method of wet oxidation treatment is improved so that no odor countermeasure is required. Further, as a measure relating to scale, for example, the method of adding an additive (i) has an effect on a specific scale producing substance, but does not have a wide effect on various scale producing substances. In addition, as described above, no particular effect can be expected for wastewater containing sulfur or the like. (ii) In the method of removing the scale by using a cleaning agent, the wastewater treatment must be stopped and washed every time the scale adheres, which causes problems in maintenance and operation of the wastewater treatment. (iii) In the method of removing the scale-forming substance by pretreatment, a large amount of pretreatment is required to remove all the various scale-forming substances, and it is difficult to remove it sufficiently. Therefore, the merit of treating the wastewater by the wet oxidation treatment method is reduced.
(iv) The method of solving the problem by improving the system of the device is difficult with the waste water containing sulfur as described above.

Therefore, an object of the present invention is to solve the above-mentioned problems, that is, the cost of the wastewater and the organic compounds of the wastewater to a sufficiently low level without the production of secondary pollutants in the treatment liquid, It proposes a method for purifying the wastewater which can remove contaminants such as inorganic compounds and is easy to maintain without generation of scale.

[0007]

Means for Solving the Problems As a result of intensive research to solve the above problems, the present inventor has supplied waste water containing sulfur and / or a sulfur compound having a lower oxidation number with a gas containing oxygen. Under the temperature of 110 ° C. to 370 ° C., the pressure for holding the liquid phase of the waste water, and the pH of the treatment liquid after the wet oxidation treatment is 5 or more, the treatment method of waste water is characterized by performing the wet oxidation treatment. The present invention has been completed by finding a method for purifying the wastewater which is excellent in terms of easiness, practicality, and economy.

That is, according to the present invention, waste water containing sulfur and / or a sulfur compound having a lower oxidation number is supplied with a gas containing oxygen at a temperature of 110 ° C. to 370 ° C. and the waste water maintains a liquid phase. A method for treating wastewater is characterized in that the pressure and the treatment liquid pH after the wet oxidation treatment are 5 or more, and the wet oxidation treatment is performed.

The sulfur and / or sulfur compound having a lower oxidation number is added to the waste water at 300 mg / liter (as sulfate ion conversion).
It is preferable to contain the above.

Heavy metals, aluminum, phosphorus, silicon,
It is preferable that at least one selected from the group consisting of calcium and magnesium is contained in the wastewater in an amount of 1 mg / liter (equivalent to each element) or more.

It is preferable to add an alkali before and / or during the wet oxidation treatment so that the pH of the treatment liquid after the wet oxidation treatment is 5 or more.

A solid catalyst may be used in the wet oxidation treatment.

The sulfur and / or the sulfur compound having a lower oxidation number to be treated in the present invention is not particularly limited. For example, in addition to sulfur itself, the sulfur compound having a lower oxidation number is sodium thiosulfate. , Various thiosulfates such as potassium thiosulfate, various sulfide inorganic salts such as sodium sulfide, potassium sulfide, and sodium hydrogen sulfide, or hydrogen sulfide, or organic substances containing sulfur such as various alkyl sulfides and mercaptans. .

This treatment method is particularly effective for various thiosulfates or various sulfide inorganic salts among the above sulfur and the like, and is more effective for wastewater containing various thiosulfates.

The amount of sulfur or the like according to the present invention is not particularly limited, but is not less than 300 mg / liter (sulfuric acid ion conversion) in total in the waste water together with sulfur and / or a sulfur compound having a lower oxidation number. It is effective and more effective when it is contained in an amount of 1 g / liter (sulfuric acid ion conversion) or more. If it is less than 300 mg / liter, sulfur or the like is promptly oxidized or oxidatively decomposed into sulfate ions, and there is no particular problem. On the contrary, as the amount is large, the low-oxidation-number sulfur-containing substance is not readily oxidized or oxidatively decomposed and is likely to cause scale formation, so that the effect of the treatment method according to the present invention becomes remarkable. On the other hand, if it exceeds 200 g / liter (in terms of sulfate ion), the wet oxidation reaction becomes a rate-determining factor for the dissolution of oxygen and the treatment efficiency decreases, and preferably 15
It is less than 0 g / liter (sulfuric acid ion equivalent), and more preferably 100 g / liter (sulfuric acid ion equivalent).

Substances contained in addition to sulfur and the like contained in the wastewater according to the present invention include heavy metals, aluminum,
It is at least one selected from the group consisting of phosphorus, silicon, calcium and magnesium (scale-generating substance), and examples of heavy metals include cadmium (Cd), nickel (Ni), cobalt (Co), manganese (M
n), copper (Cu), zinc (Zn), silver (Ag), iron (F
e), tin (Sn), antimony (Sb), lead (P
b), thallium (Tl), mercury (Hg), arsenic (A
s), chromium (Cr), and bismuth (Bi), and the state thereof is not particularly limited, but is, for example, an element ion of the above various metal ions, a complex ion, or an organometallic compound. It is particularly effective for those heavy metals that produce sparingly soluble sulfides. Further, Pb and Fe are particularly effective.

Aluminum (Al), phosphorus (P), silicon (Si), calcium (Ca) and magnesium (M)
The state of g) is not particularly limited, but is, for example, the above-mentioned various metals and the like, and is particularly effective for Al and P.

The amount of the scale-forming substance is effective when the total amount of the above-mentioned metals and the like is 1 mg / liter (each element conversion) or more in the waste water, and 20 mg / liter is more effective.
It is liter or more, more preferably 30 mg / liter or more. If the amount is less than 1 mg / liter, the generation of scale is not particularly significant and does not pose a problem.

On the contrary, the larger the amount, the more problematic the scale generation, and the effect of the processing method according to the present invention becomes remarkable. However, when the total amount of the scale-forming substances exceeds 200 g / liter, the wet oxidation reaction becomes a rate-determining factor for the dissolution of oxygen and the treatment efficiency decreases, preferably less than 150 g / liter, more preferably 100 g / liter. It is less than liter.

The waste water often contains contaminants such as organic compounds and inorganic compounds, and these substances can also be purified by the wet oxidation treatment of the present invention. The kind of the pollutant is not particularly limited, but as organic compounds, methanol, phenol, formalin, DMSO, DMF, pyridine, various surfactants,
There are various types such as various polymers, and for inorganic compounds,
There are various kinds of nitrite ion, sulfite ion and the like.

The concentration of COD in the waste water is effective when it is contained in the range of 1 g / liter to 200 g / liter, and more effective is 5 g / liter to 150 g.
g / liter. When the concentration of COD exceeds 200 g / liter, the heat of oxidation of COD becomes very large, which makes it difficult to control the treatment equipment. When it is less than 1 g / liter, the treatment method of the present invention is used. There is little effect of treating the wastewater, and it can be treated using other conventional techniques. If it is less than 5 g / liter,
The COD has a small heat of oxidation, and in such a case, even if a heat exchange device is used as an auxiliary equipment to recover the heat, it becomes difficult to independently operate the wet oxidation treatment device by this heat. Further, in such a case, although there is no problem in the wet oxidation itself, a separate heat supply device is required for the treatment, which is relatively disadvantageous in terms of energy consumption.

As the wet oxidation treatment apparatus used in the present invention, a commonly used one is used, and the wet oxidation reaction tower may be of a single-tube type or a multi-tube type.
Depending on the components contained in the wastewater and the amount thereof, a single pipe type and a multi-pipe type may be used alone or in combination, and the components contained in the above wastewater may be separately treated under conditions suitable for the treatment.

The wet oxidation treatment described here is not particularly limited, but it may be treated as an empty column without filling anything in the wet oxidation reaction column, or may be filled with the catalyst described below. However, wet oxidation treatment may be performed. Further, it is also possible to fill the inside of the wet oxidation reaction tower with a filler such as metal or ceramic to improve stirring of liquid and gas.

The catalyst described herein may be any catalyst as long as it is a solid catalyst and has both activity and durability under the conditions of liquid phase oxidation, such as titanium,
A catalyst containing iron, aluminum, silicon, zirconium, activated carbon, or the like can be used, and it is preferable to use an oxide such as titanium, titanium-zirconium, or titanium-iron. These catalysts may contain a second component in addition to the above components (hereinafter also referred to as the first component).

As the second component, at least one metal such as manganese, cobalt, nickel, tungsten, copper, cerium, silver, platinum, palladium, rhodium, gold, iridium or ruthenium, or a component thereof is used. Can be used. This catalyst preferably accounts for 75 to 99.95% by weight of the first component and 25 to 0.05% by weight of the second component.
In addition, various shapes of the catalyst can be adopted and are not particularly limited.

The treatment pressure of the wet oxidation treatment of the present invention is appropriately selected according to the correlation with the treatment temperature, and is determined by the pressure at which the liquid retains the liquid phase.

The treatment temperature of the wet oxidation treatment of the present invention is 11
The temperature is 0 ° C or higher and lower than 370 ° C, and preferably 140 ° C or higher and lower than 300 ° C. This is because the liquid cannot hold the liquid phase when the temperature is 370 ° C. or higher. On the other hand, if the temperature is lower than 110 ° C., the treatment efficiency will decrease.

The oxygen-containing gas used in the reaction is a gas containing oxygen, air or ozone. When a gas such as ozone or oxygen is used, it can be appropriately diluted with an inert gas or the like before use. . In addition to these gases, oxygen-containing waste gas generated from other plants can also be used as appropriate.

The amount of this gas used can be appropriately selected depending on the concentration of the wastewater. In this case, the COD of the wastewater
0.5 times to 5 times the amount of oxygen required to completely transform the components into water, carbon dioxide gas, nitrogen gas, inorganic salts, and other ash is effective, and more effectively 1 time to 3 times. Is. When it exceeds 5 times, unnecessary oxygen is supplied, and when it is less than 0.5 times, the amount of oxygen required is insufficient and purification of the waste water becomes incomplete. Further, the range of 0.5 times to 1 time is not sufficient as the amount of oxygen required to completely convert the COD component of the waste water into water, carbon dioxide gas, nitrogen gas, inorganic salts, and other ash content. The reason for this is that the processing efficiency of COD is usually less than 100%, so the supplied oxygen is not used 100% in the end, and in such a case the amount of oxygen supplied should be adjusted to 1 times the actual processing efficiency. Even if it is reduced to less than COD
This is because the processing efficiency of does not change.

[0030] As the space velocity of the waste water of the wet oxidation process of the present invention, 0.1hr ~ ¹ ~10hr ~ ¹ is effective, is 0.3hr ~ ¹ ~5hr ~ ¹ is the more effective . If the space velocity is less than 0.1 hr to ¹ , the amount of waste water to be treated will be reduced and the equipment will be excessive. On the contrary, if it exceeds 10 hr to ¹ , the treatment efficiency will be reduced, which is not preferable.

In the treatment method of the present invention, the waste water may be subjected to wet oxidation treatment, and then a solid-liquid separation treatment apparatus may be used to perform solid-liquid separation removal of insoluble matter and the like. This removing operation may be performed by continuously performing solid-liquid separation and removing operation under pressure, or may be performed by solid-liquid separation under normal pressure conditions after decompressing, and is not particularly limited. Not something. As the solid-liquid separation treatment device, various devices such as a sedimentation separation treatment device, a centrifugal separation treatment device, or a filtration separation treatment device can be adopted. At this time, a coagulant, a coagulant aid, a filter aid, etc. may be added as necessary to increase the processing speed and separation efficiency. As the coagulant, coagulant aid, and filter aid, various conventional materials can be used and are not particularly limited.

In the treatment method of the present invention, the pH of the treatment liquid after the wet oxidation treatment needs to be 5 or more, and the pH is 5 or more.
If the amount is less than the above, the treatment efficiency of COD and sulfur is improved, but an odor similar to hydrogen sulfide is generated in the exhaust gas, and further scales and solids are generated in the heat exchanger, reaction tower, packing, catalyst, etc. And the like adhere to each other, resulting in blockage or pressure loss, reduction in heat transfer efficiency, and the like.

The pH of the treatment liquid is not particularly limited as long as it is 5 or more, but it is preferably pH 6 to 10.
It is effective to be controlled to pH 7, and more effective is pH 7-9. The higher the pH of the treatment liquid, the higher the effect of preventing scale adhesion. However, when the pH is 10 or more, it is necessary to readjust the pH both when the treatment liquid is directly discharged and when biological treatment is performed as a post-treatment, and the acid for the readjustment of the pH needs to be readjusted. Besides increasing the amount used, it is dangerous to handle the processing liquid.

The alkali added to the wastewater according to the present invention is not particularly limited, but it is preferable to use NaOH or Na ₂ CO ₃ from the viewpoint of cost,
More preferably, it is convenient to handle when it is used as an aqueous solution.

The method of adding the alkali and the place of addition are not particularly limited, but the alkali is made into an aqueous solution and directly fed to the pressurizing system by a pressurizing pump, and continuously mixed with the wastewater in the pressurizing system. Is effective.

The pressurizing system described here refers to a wet oxidation reaction tower, a heat exchanger, and a pressure-applied line attached to these.

When the waste water is wet-oxidized without adding an alkali, the pH of the treated liquid after treatment is 5
If it becomes the above, addition of an alkali is especially unnecessary. Further, even if the pH of the waste water after the treatment is 5 or more, the pH may be less than 5 in the reaction tube during the wet oxidation treatment, and in such a case, it is necessary to add an alkali.

[0038]

[Effect] By this treatment method, most of sulfur or sulfur oxides having a lower oxidation number are oxidized or oxidatively decomposed, and most of sulfur atoms are converted into sulfate ions, and the wastewater can be purified.

Further, the exhaust gas can be discharged without containing a substance that causes secondary pollution and without the need to take special measures for deodorizing.

Most of the scale-forming substances in the wastewater are
It changes into water-insoluble or sparingly soluble substances such as oxides, hydroxides, inorganic salts, and other compounds, and it precipitates from wastewater, but it adheres to heat exchangers, reaction towers, packing materials, catalysts, etc. as a scale. It is processed without doing. Then, these solids are discharged together with the processing liquid.

Further, pollutants such as organic compounds and inorganic compounds in the wastewater are also oxidized, oxidatively decomposed or decomposed to be converted into lower molecular weight organic substances, inorganic salts, carbon dioxide gas, nitrogen gas, water or ash. As a result, contaminants of the wastewater can be removed, and the wastewater can be purified stably for a long period of time without being affected by scale.

The wastewater purified by the treatment method of the present invention can be discharged directly or subjected to biological treatment or chemical treatment as a post-treatment. Even in this case, pollutants and the like are considerably reduced, and residual pollutants and the like are decomposed into substances that are very easily decomposed in biological treatment or chemical treatment. The burden on the chemical treatment is very small. Further, after the treatment method of the present invention, the heavy metals and the like dissolved in the wastewater can be easily removed by solid-liquid separation from the wastewater, so that further biological treatment or chemical treatment can be performed. The burden can be reduced.

In addition, since the present invention requires only a small land and the apparatus is compact, the conventional wastewater treatment equipment, for example, biological treatment equipment such as activated sludge treatment equipment or chemical treatment equipment such as combustion treatment equipment. Compared with the case where the wastewater is treated by adopting a treatment facility or the like without combining it with a wet oxidation treatment facility, the treatment facility is small, the treatment process is simplified, and it is advantageous in terms of capital investment and running cost. Become.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0045]

【Example】

(Example 1) Using the wet oxidation treatment apparatus shown in FIG.
The wet oxidation treatment was performed continuously for 00 hours. And 50
The amount of aluminum in the filtrate of the treatment liquid obtained after 0 hours was measured by inductively coupled high frequency plasma emission spectroscopy to determine the concentration. Further, the concentrations of thiosulfate ion and sulfite ion were determined using an ion chromatographic analyzer, and the concentrations of S ² to ion were also determined by absorptiometry. Further, TOC and COD (Cr) were measured to determine the concentration and treatment efficiency.

A detailed method of using this treatment apparatus is to use the waste water sent from the waste water supply line 9 for the waste water supply pump 3.
Pressure feed up to 9 kg / cm ² G at a flow rate of 0.5 liter / hr, and the NaOH aqueous solution supply line 10
The 1 wt% NaOH aqueous solution sent from the NaOH aqueous solution supply pump 4 is also 9 k at a flow rate of 50 ml / hr.
The pressure was fed up to g / cm ² G. On the other hand, after the air supplied from the oxygen-containing gas supply line 11 is pressurized by the compressor 6, the O ₂ / COD (Cr) (oxygen content in the air / chemical oxygen demand) = 3.0 Mixed in wastewater.

The gas-liquid mixture is supplied to the gas-liquid mixture supply line 1
After being heated in the heat exchanger 2 via 2 and then introduced into the wet oxidation reaction tower (empty tower) from below, the wet oxidation treatment is carried out at a treatment temperature of 160 ° C., and the treated water is heat-exchanged through the treated water line 11. It was cooled in the vessel 2 and passed into the gas-liquid separator 5. The space velocity of this wastewater was 0.5 hr- ¹ . In the gas-liquid separator 5, the liquid level controller (LC) detects the liquid level to operate the liquid level control valve 7 to maintain a constant liquid level, and the pressure controller (PC) detects the pressure. Then, the pressure control valve 8 is operated to maintain a constant pressure, and the treated water is discharged from the treated water discharge line 15.

The properties of the wastewater used for the treatment are as follows: aluminum 110 mg / liter (element conversion) and S ² ~
The amount of ions was 8.5 g / liter (sulfur atom conversion).
TOC is 3.4g / liter, COD (Cr) is 22g
/ Liter, the pH was 11.2.

The properties of the waste water after wet oxidation are aluminum 1 mg / liter (elemental conversion) or less, S ² to ion 1 mg.
/ Liter (sulfur atom conversion) or less, thiosulfate ion of 0.
63 g / liter (sulfur atom equivalent), sulfite ion 50
It was mg / liter (equivalent to sulfur atom). Also, TO
C concentration 1.6g / l, COD (Cr) concentration 3.5g
/ L, respectively, TOC treatment efficiency 53%, COD
The (Cr) treatment efficiency was 84%. The pH was 8.9. After the treatment for 500 hours, no particular deposit was found on the side surface inside the reaction tower. Further, the exhaust gas during the treatment had no particular odor.

Example 2 Using the wet oxidation treatment apparatus shown in FIG. 1, the wet oxidation treatment was continuously carried out for 500 hours under the following conditions by the same operation as in Example 1, and the treatment after 500 hours was performed. The liquid was analyzed.

The wet oxidation conditions are as follows: flow rate of the waste water is 2 liter / hr, concentration of NaOH aqueous solution is 10 wt%, NaOH
The flow rate of the aqueous solution is 0.2 liter / hr, the space velocity of the waste water is 2.0 hr- ¹ and O ₂ / COD (Cr) (the amount of oxygen in the air /
Chemical oxygen demand) = 2.0, processing pressure 90 kg / cm
² G, the treatment temperature was 260 ° C. The properties of the wastewater subjected to the treatment were as follows: copper 20 mg / liter (element conversion), iron 1.2 g / liter (element conversion), thiosulfate ion 9.1 g / liter (sulfur atom conversion). .
Also, TOC is 17.1 g / liter, COD (Cr) 46
The pH was 9.6 at g / liter.

The properties of the waste water after wet oxidation are as follows: copper in the filtrate of the treatment liquid is 1 mg / liter (elemental conversion) or less, iron 1 mg
/ Liter (element conversion) or less and thiosulfate ion 1 m
g / liter (sulfur atom equivalent) or less, sulfite ion 1 m
It was below g / liter (equivalent to sulfur atom). Also, T
OC concentration 5.5g / liter, COD (Cr) concentration 14g
/ Liter, TOC treatment efficiency 68%, COD
The (Cr) treatment efficiency was 70%. The pH was 7.8. After the treatment for 500 hours, no particular deposit was found on the side surface inside the reaction tower. Further, the exhaust gas during the treatment had no particular odor.

Example 3 Using the wet oxidation treatment apparatus shown in FIG. 1, a catalyst composed of titanium-iron oxide and ruthenium (1.5% by weight of ruthenium) was added to the upper part (outlet side) of the reaction tower. 0.2 liter was filled, the wet oxidation treatment was continuously performed for 500 hours by the same operation as in Example 1 under the following conditions, and the treated liquid after 500 hours was analyzed.

The wet oxidation treatment condition is that the flow rate of the wastewater is 1.0.
Liter / hr, NaOH aqueous solution concentration 10 wt%, Na
The flow rate of the OH aqueous solution is 10 ml / hr, the space velocity of the waste water is 1.0 hr to ¹ (empty tower standard of the entire reaction tower), O ₂ / COD
(Cr) (oxygen amount in air / chemical oxygen demand amount) = 1.
2. The treatment pressure was 70 kg / cm ² G and the treatment temperature was 240 ° C. In addition, the property of the wastewater used for treatment is 35 m of lead.
g / liter (element conversion) and thiosulfate ion 0.8
It was 0 g / liter (equivalent to sulfur atom). Also TOC
Was 29 g / liter, COD (Cr) was 84 g / liter, and the pH was 8.3.

The properties of the waste water after wet oxidation were 1 mg / liter of lead (calculated as element) or less, 1 mg / liter of thiosulfate ion (calculated as sulfur atom) or less, and 1 mg / liter of sulfite ion (calculated as sulfur atom) or less. The TOC concentration was 3.1 g / liter and the COD (Cr) concentration was 6 g / liter, and the TOC treatment efficiency was 89% and the COD (Cr) treatment efficiency was 93%, respectively. The pH was 7.5. Also, 5
After the treatment for 00 hours, no particular deposit was found on the side surface inside the reaction tower. Further, the exhaust gas during the treatment had no particular odor.

(Comparative Example 1) A wet oxidation treatment was carried out under the same conditions as described in Example 2 except that the aqueous NaOH solution was not fed.

The results obtained are as follows: copper 1 mg / liter (element conversion) or less, iron 1 mg / liter (element conversion) or less and thiosulfuric acid 1 mg / liter (sulfur atom conversion) or less,
It was 1 mg / liter (sulfur atom conversion) or less of sulfite ion. Also, TOC concentration 5.0g / liter, COD
At a (Cr) concentration of 12 g / liter, the TOC treatment efficiency was 71% and the COD (Cr) treatment efficiency was 74%, respectively. The pH of the treatment liquid was 1.7. However, after the treatment for 500 hours, black deposits had adhered to the inside of the reaction tower. As a result of analysis with an electron probe microanalyzer, it was found that copper, iron and sulfur were the main components. Further, the exhaust gas during the treatment had an odor similar to that of hydrogen sulfide.

Comparative Example 2 The treatment was carried out under the same conditions as described in Example 2 except that air was not fed. As a result, hydrogen sulfide was generated during the treatment, and after about 50 hours, the reaction tower was blocked and the treatment could not be performed. Black deposits adhered to the inside of the reaction tower. As a result of analysis by an electron probe microanalyzer, it was found that copper, iron and sulfur were the main components. The exhaust gas during treatment had a fairly strong hydrogen sulfide odor.

[Brief description of drawings]

FIG. 1 is one of embodiments of a processing apparatus according to the present invention.

[Explanation of symbols]

 1. Wet oxidation reaction tower 2. Heat exchanger 3. Waste water supply pump 4. NaOH aqueous solution supply pump 5. Gas-liquid separator 6. Compressor 7. Liquid level control valve 8. Pressure control valve 9. Waste water supply line 10. NaOH aqueous solution supply line 11. Oxygen-containing gas supply line 12. Gas-liquid mixture supply line 13. Treated water line 14. Gas discharge line 15. Treated water discharge line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kunio Sano Inventor, Kunio Sano 1 992 Nishikioki, Kamahama, Aboshi-ku, Himeji-shi, Hyogo, Japan Catalysis Research Institute, Inc.

Claims (5)

[Claims] 1. Waste water containing sulfur and / or a sulfur compound having a lower oxidation number is fed with a gas containing oxygen to obtain 11
A temperature of 0 ° C. to 370 ° C., a pressure at which the wastewater holds a liquid phase,
A method for treating wastewater, wherein the treatment liquid after the wet oxidation treatment has a pH of 5 or more, and the wet oxidation treatment is performed. 2. The method for treating wastewater according to claim 1, wherein the sulfur and / or the sulfur compound having a lower oxidation number is contained in the wastewater in an amount of 300 mg / liter (sulfuric acid ion conversion) or more. 3. The method for treating wastewater according to claim 1, wherein the wastewater contains at least 1 mg / liter (each element conversion) of at least one selected from the group consisting of heavy metals, aluminum, phosphorus, silicon, calcium and magnesium. . 4. The pH of the treatment liquid after the wet oxidation treatment by adding an alkali before and / or during the wet oxidation treatment.
Is 5 or more, The method for treating wastewater according to claim 1. 5. The method for treating wastewater according to claim 1, wherein the wet oxidation treatment is performed using a solid catalyst.