JP4541776B2 - Purification method for wastewater containing organic substances - Google Patents

Description

  The present invention relates to a method for purifying wastewater containing an organic substance.

  A method of aggregating a coating component contained in a water-based paint washing waste liquid with a flocculant and then filtering and separating the aggregate with a nonwoven fabric is known (Patent Document 1).

  On the other hand, it comprises a hydrothermal reaction treatment step in which organic waste is liquefied by a hydrothermal reaction under subcritical water conditions or supercritical water conditions, and an air oxidation treatment step in which liquid hydrothermal reaction treatment products are oxidized in air. The processing method of the organic waste obtained is known. Furthermore, a method for recovering methane gas by performing methane fermentation in the presence of sludge containing anaerobic microorganisms after the hydrothermal reaction treatment step or the air oxidation treatment step is also known (Patent Document 2).

See JP2001-149948A See JP-A-2002-102870

  In the case of the method described in Patent Document 1, waste water filtered by a non-woven fabric can be discarded in an arbitrary place, and the non-woven fabric and the aggregate can be discarded as industrial waste. The remaining components that could not be aggregated by the flocculant, such as neutralizer components (amines, acids, etc.), curing agent components (melamine curing agents, etc.), organic solvent components (alcohol solvents, etc.), resin components (low Molecular weight acrylic resin, low molecular weight polyester resin, etc.) and other additive components. Accordingly, such waste water cannot be discarded because it causes problems such as environmental pollution when it is discarded in a river or the like.

  A method of removing waste water containing organic substances that cause environmental pollution as described above by biological treatment with bacteria is also conceivable. In such biological treatment, in particular, amine, melamine It was difficult to separate and remove or decompose low molecular weight components (molecular weight of about 1000 or less) such as curing agents.

  In the case of the method described in Patent Document 2, in order to perform a hydrothermal reaction treatment of organic substances directly under supercritical conditions, when waste liquid containing solids such as sludge is treated, the treatment efficiency is poor. There are problems such as poor degradation of low molecular weight organic substances such as curing agents, amines and organic solvents. Furthermore, the low molecular weight organic substance remaining in the supercritical processing is difficult to be completely decomposed and removed even if it is biologically processed.

  An object of the present invention is to provide a method for treating wastewater that efficiently separates and removes low-molecular-weight organic substances that cannot be separated and removed by conventional methods and has a low content of harmful substances.

According to the present invention, the following wastewater purification method is provided.
(A) Wastewater containing an organic substance is subjected to auxiliary treatment for assisting supercritical treatment or subcritical treatment, and then purified by treatment including supercritical treatment or subcritical treatment. In the purification method of
The auxiliary treatment includes a treatment for performing at least a microwave treatment and a treatment with 12CaO.7Al ₂ O ₃ simultaneously under heating by the microwave (hereinafter also referred to as method A). .

(B) Wastewater containing organic substances is subjected to auxiliary treatment to assist supercritical treatment or subcritical treatment, then supercritical treatment or subcritical treatment, and then purified by treatment including biological treatment. In a purification method for wastewater containing organic substances,
The auxiliary treatment includes a treatment for performing at least a microwave treatment and a treatment with 12CaO · 7Al ₂ O ₃ at the same time under heating by the microwave (hereinafter also referred to as method B). .
(C) In a purification method for wastewater containing an organic substance, the wastewater containing an organic substance is subjected to biological treatment and then purified by a treatment including supercritical treatment or subcritical treatment.
Prior to biological treatment, at least microwave treatment and treatment with 12CaO · 7Al ₂ O ₃ are simultaneously performed under heating by the microwave (hereinafter also referred to as method C). .

  As waste water containing organic substances used in the A method, B method and C method of the present invention, there are various types of waste water, but it is particularly preferable to use waste water used in painting, specifically, Examples thereof include water for washing paints generated when washing paint adhering to various painting lines and coating plants, paint booth water, paint production equipment, painting equipment, jigs, and the like.

Hereinafter, the A method will be described in detail.
The auxiliary process used in the method A is a process for assisting a supercritical process or a subcritical process (hereinafter, these processes are also referred to as a U process). By adopting this auxiliary treatment , it is possible to perform the U treatment in a short time and to obtain waste water with a low content of organic substances.
The auxiliary treatment includes a physical method (Phy method) and a chemical method (Chem method). The Phy method is a method for solid-liquid separation of a solid substance (sludge) contained in waste water. According to this solid-liquid separation treatment, the amount of wastewater to be treated in the U treatment is reduced, and as a result, the U treatment can be performed in a short time. On the other hand, the Chem method is a method in which a hardly decomposable organic substance that cannot be separated by the U method is chemically decomposed into an easily decomposable organic substance.

The Phy method, agglutination agent separation, sedimentation process, flotation process, Ru with at least one physical treatment selected from the filtration process.
By this treatment, in the waste water for coating, usually 1-100 g / liter of precipitates, COD _Mn 1,000-8,000 mg / liter, TOC 1,000-8,000 mg / liter, BOD 1,000-8,000 mg / liter, The organic solvent is processed to about 1 to 10,000 mg / liter g. Here, COD _Mn means chemical oxygen demand, TOC means total organic carbon content, and BOD means biochemical oxygen demand. Examples of the organic solvent include aqueous ether-based or alcohol-based solvents.

The above-mentioned flocculant separation treatment is conventionally performed by adding a flocculant to wastewater containing organic substances such as paint wastewater, and insolubilizing solid substances such as pigments and resins such as organic substances and inorganic substances in the wastewater. This is a known process.
By this flocculant separation treatment, the sludge that has floated or settled is separated and removed. The separated sludge is dehydrated to become sludge. Then, the waste water containing the remaining organic substance from which the sludge has been removed is subjected to a supercritical treatment or a subcritical treatment, which is a secondary treatment, after performing the Chem method as necessary.

  As the flocculant, conventionally known inorganic salts and polymer flocculants can be used. Examples of inorganic salts include PAC (polyaluminum chloride), aluminum sulfate (sulfuric acid band), sodium aluminum oxide, polyaluminum chloride, ferric chloride, ferrous sulfate, and ferric sulfate. Polymer flocculants include polyacrylate, polyacrylamide, sodium acrylate, modified polyacrylamide, polymethacrylate, polyamide, polyamine, amino condensation, and maleic acid copolymer. Products, quaternary ammonium salts, polyvinyl pyridine, polyoxyethylene, sodium alginate, water-soluble aniline resin, polythiourea, polyethyleneimine, and the like. These flocculants can be used alone or in combination of two or more according to the type of waste water.

  The settling separation process described above is a method of separating using the density difference between water and organic and / or inorganic suspended substances or solid particles present in wastewater, and is settling by gravity. And separation treatment by centrifugation. In particular, in the centrifugal separation treatment, solids such as suspended solids and solid particles have a density higher than that of water, so that solid-liquid separation is performed in a short time by high centrifugal force. The centrifugation can be performed using a conventionally known centrifuge such as a continuous horizontal type or a batch type vertical type. And the waste water containing the remaining organic substance from which the sludge has been removed is subjected to a supercritical treatment or a subcritical treatment after performing the Chem method as necessary.

  In the above-described levitation separation process, fine bubbles are introduced into waste water, the bubbles are attached to organic and / or inorganic suspended solids and solid particles, and the apparent specific gravity of the particles is reduced to float on the surface of the waste water. It is a process to separate. The levitation separation process may be performed using a conventionally known levitation separation apparatus such as a full pressure levitation separation apparatus, a partial pressure levitation separation apparatus, a circulating pressure levitation separation apparatus, or an atmospheric pressure levitation separation apparatus. it can.

  And the waste water containing the remaining organic substance from which the sludge has been removed is subjected to a supercritical treatment or a subcritical treatment after performing the Chem method as necessary.

  The filtration treatment described above can be performed under normal pressure or under pressure using, for example, a screen, cloth, filter, sieve, or the like. The treatment can be used alone or in combination of two or more.

Examples of the Chem method include a specific oxidation-reduction treatment, a specific microwave treatment, a specific inorganic substance decomposition treatment, and the like . The treatment can be used alone or in combination of two or more. Particularly, in the present invention, in combination with a treatment with microwave treatment and 12CaO · 7Al ₂ O _3, it is mandatory to be performed simultaneously under heating by the microwave. These processes can be repeated as necessary. In addition, as a process of repeating a combination of two or more kinds of processes, for example, microwave treatment is performed in the presence of 12CaO · 7Al ₂ O ₃ , and then microwave treatment is performed in the presence of an alkaline earth metal oxide. And a method of performing microwave treatment again in the presence of 12CaO · 7Al ₂ O ₃ and / or microwave treatment in the presence of an oxide of an alkaline earth metal.

In the oxidation-reduction treatment, an organic substance in waste water is oxidized or reduced to cause some chemical change to the organic substance, thereby efficiently performing decomposition by supercritical treatment or subcritical treatment. The redox treatment, Ru using electrolysis process noted below.

  The electrolysis treatment is a method in which an electrode is placed in waste water containing an organic substance such as paint waste water and a direct current is passed to cause an electrolysis reaction. In this process, electrons are taken in at the anode to cause an oxidation reaction, and at the cathode, electrons are emitted to cause a reduction reaction.

  In addition to the oxidation-reduction reactions described above, in electrolysis, solids such as organic and inorganic substances such as pigments and resins in wastewater are adsorbed into fine bubbles of oxygen and hydrogen generated by electrolysis of water. These substances can be collected on the surface of wastewater by the buoyancy of bubbles.

  By this electrolysis treatment, the sludge that has floated or settled is separated and removed. The separated sludge is dehydrated to become sludge. The waste water containing the remaining organic material from which the sludge has been removed is subjected to a supercritical treatment or a subcritical treatment, which is a secondary treatment.

To make the electrical degradation process, it performs electrolysis by introducing, dissolving an electrolyte in a test paper wastewater. In this case, a treatment tank in which a plurality of electrodes are arranged at appropriate intervals in the water tank is used. Electrolysis can be performed by energizing between the electrodes. There use an aluminum electrode as the electrode, as the electrolyte that use nitric acid sodium.

  In the electrolysis treatment, the electrolyte concentration (for example, sodium nitrate concentration) is about 0.01 to 0.05 mol / liter with respect to the solid content concentration of 20,000 mg / liter.

  The microwave treatment described above is a treatment that causes some chemical change to the organic substance by irradiating the organic substance in the wastewater with the microwave. According to this treatment, the organic substance itself is decomposed or easily decomposed by supercritical processing or subcritical processing.

The microwave is an electromagnetic wave having a wavelength of about 0.1 to 1,000 mm, and includes UHF (decimeter wave), SHF (centimeter wave), EHF (millimeter wave), and submillimeter wave. Although 2450 MHz, which is internationally allocated for industrial use, is often used, the present invention is not limited to this.
The microwave processing can be performed using a microwave generator used in a microwave oven or the like.

  The microwave irradiation time can be appropriately selected depending on the concentration of organic matter in the wastewater, the intensity of irradiation light, etc., but the irradiation time is usually preferably about 1 to 60 minutes.

  Although the wastewater generates heat by microwave irradiation, generally, the higher the temperature, the higher the rate of decomposition of organic matter. Therefore, there is no need for cooling in a range where there is no work risk such as boiling of the wastewater or volatilization of the organic solvent. The temperature of the waste water is preferably higher.

  The microwave treatment can be performed using, for example, a solid catalyst under supply of an oxygen-containing gas. According to this microwave treatment, the organic substance undergoes an oxidative decomposition treatment.

  As the solid catalyst, conventionally known catalysts can be used without particular limitation, and examples thereof include titanium, silicon, zirconium, manganese, iron, cobalt, nickel, tungsten, cerium, copper, silver, gold, platinum, palladium, rhodium, ruthenium and An insoluble or hardly soluble compound of a metal element selected from iridium or the like, or an inorganic carrier (particulate matter such as inorganic oxide, activated carbon or zeolite) supporting these metals can be used.

As an inorganic substance decomposition treatment , at least one inorganic compound selected from 12CaO · 7Al ₂ O ₃ , alkaline earth metal oxides and alkaline earth metal hydroxides is used to convert organic substances in wastewater. A process that causes some chemical change is performed . According to this treatment, the organic substance is decomposed by itself or is susceptible to degradation by supercritical processing or subcritical processing. This inorganic substance decomposition treatment can be performed simultaneously with the U treatment.

The above 12CaO · 7Al ₂ O ₃ is a crystal of 12CaO · 7Al ₂ O ₃ called C12A7, and is usually obtained by heating and baking a mixture of calcium carbonate and aluminum oxide at 1200 ° C to 1400 ° C. It is done. This calcination reaction may be performed in a normal atmosphere, but is preferably performed in a pure oxygen atmosphere from the viewpoint of the organic matter decomposition effect. As the 12CaO · 7Al ₂ O ₃ , for example, a 12CaO · 7Al ₂ O ₃ compound that includes active oxygen at a high concentration disclosed in JP-A-2002-3218 can be used.

Decomposing the organic matter containing wastewater using the 12CaO · 7Al ₂ O ₃ is the 12CaO · 7Al ₂ O ₃ was added to the waste water is carried out by stirring while heating pressurized. After completion of the treatment, 12CaO · 7Al ₂ O ₃ can be recovered by filtration (or precipitation) and reused.

The amount of 12CaO · 7Al ₂ O ₃ added is appropriately selected depending on the type and concentration of organic matter contained in the wastewater, and is usually 0.1 to 40% by weight, preferably about 0.5 to 15% by weight, based on the wastewater. Is preferred. When the amount added is less than 0.1% by weight, it is difficult to sufficiently decompose the organic matter, while when it exceeds 40% by weight, it is difficult to sufficiently stir the inside of the treatment tank, and the cost is disadvantageous. So undesirable.

  In the above treatment, the organic matter resolution of the inorganic substance can be further increased by heating. As the heating means, microwave irradiation is particularly suitable.

  The above alkaline earth metal oxide and / or hydroxide is preferably water-insoluble. As the alkaline earth metal, calcium is particularly preferable from the viewpoints of cost and organic matter resolution. Alkali earth metal oxides react with water to form hydroxides. At this time, since they react vigorously with heat generation, hydroxides are preferable from the viewpoint of handling properties and stability. Further, as the alkaline earth metal oxide and / or hydroxide, a composite metal oxide and / or hydroxide containing an alkaline earth metal may be used.

Decomposing the organic matter containing wastewater using an oxide and / or hydroxide of the alkaline earth metal, an oxide of the alkaline earth metal and / or hydroxide is added in the waste water, stirred while heating pressurized Is done by doing. After completion of the treatment, the alkaline earth metal oxide and / or hydroxide can be recovered by filtration and reused.

  The amount of the alkaline earth metal oxide and / or hydroxide is appropriately selected depending on the type and concentration of the organic matter contained in the wastewater, and usually 0.1 to 50% by weight, preferably 1 with respect to the wastewater. About 20% by weight is preferable. If the amount added is less than 0.1% by weight, it is difficult to sufficiently decompose the organic matter. On the other hand, if it exceeds 50% by weight, it is difficult to sufficiently stir the treatment tank, and the cost is disadvantageous. So undesirable.

  In the above treatment, the decomposition efficiency of the organic matter can be further increased by heating. As the heating means, microwave irradiation is particularly suitable.

As an auxiliary process performed in the method A of the present invention, the Phy method or the Chem method described above can be performed alone, or after the Phy method is performed, the Chem method can be combined. However, in the present invention, it is essential that the microwave treatment and the treatment with 12CaO · 7Al ₂ O ₃ are simultaneously performed under heating by the microwave. When the other is carried out in combination, it is preferable to perform the Chem method after removing the solid content by the Phy method, particularly when the solid content of the wastewater is high.

  The U treatment in the method A of the present invention is a treatment for decomposing an organic substance by oxidizing a waste liquid containing an organic substance that has been particularly easily oxidized and decomposed by an auxiliary treatment with supercritical water or subcritical water.

  Supercritical water means water in a state where the critical conditions of water, that is, a critical temperature of 374.1 ° C. and a critical pressure of 22.12 MPa are exceeded. Subcritical water has the same effect as supercritical water. Usually, water whose temperature is 0.65 times the critical temperature or more and the pressure is 0.65 times the critical pressure or more in Kelvin units. means. Under such conditions, it is impossible to liquefy even if pressure is applied beyond this level. In terms of physical properties, supercritical water or subcritical water cannot be called a gas or a liquid, and has an intermediate property between them. The gas-liquid boundary disappears and exists as a single phase as supercritical water or subcritical water. That is, supercritical water or subcritical water is particularly useful as a reaction solvent at the time of oxidative decomposition of an organic substance because it is mixed as a single phase in an arbitrary ratio with respect to oxygen or the like.

In the oxidation treatment using supercritical water or subcritical water, conventionally known oxidizing agents (for example, H ₂ O ₂ , K ₂ Cr ₂ O ₇ , KMnO ₄ , O ₃ , O ₂ , NaOCl, halogen) are used as necessary. Elements) can be present. The ratio is usually in the range of 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight with respect to 100 parts by weight of waste water.

  In addition, supercritical processing or subcritical processing can be performed while blowing oxygen and air into wastewater.

  The conditions for supercritical processing or subcritical processing are not limited as long as the above critical conditions are satisfied. Usually, the reaction temperature is 300 to 800 ° C, preferably 400 to 600 ° C, and the pressure is 88 to 300 atmospheres ( 8.9 to 30.4 MPa), preferably 100 to 170 atmospheres (10.1 to 17.2 MPa), and the reaction time is in the range of 30 seconds to 180 minutes, preferably 5 to 90 minutes.

In supercritical processing or subcritical processing, most organic substances are composed of gaseous products (CO, H ₂ , CH ₄ , CO _2, etc.) and volatile substances such as alcohol, aldehyde, and furan by hydrolysis and thermal decomposition reactions. Is converted to Further, in the presence of oxygen, the organic matter is decomposed into water and carbon dioxide in a few seconds to a few minutes. Moreover, when a hetero atom is contained in waste water, a basic substance can be added and isolate | separated as a salt. Further, if the carbon content in the wastewater component is 2% or more, the temperature can be raised to a state of 550 ° C. or more only by the oxidation heat possessed by itself, which is advantageous in terms of energy compared to the combustion method.

  In addition, in order to perform supercritical processing or subcritical processing, the inorganic material used in the above inorganic material processing is added to the waste water, and then the supercritical state or subcritical state is obtained. Alternatively, the subcritical process can be performed simultaneously.

According to U treatment, COD _Mn is less than 1,000 mg / liter, preferably less than 500 mg / liter, TOC less than 1,000 mg / liter, preferably less than 500 mg / liter, BOD less than 1,000 mg / liter, preferably less than 500 mg in paint wastewater. / Liter, less than 1 mg / liter organic solvent, preferably less than 0.5 mg / liter.

  If it is purified to the above-mentioned level, the waste water is discharged as it is. Otherwise, it is desirable to perform the auxiliary treatment and U-treatment again using the treated water after the above-mentioned U treatment as the return water to purify to the above-mentioned level.

  In the method A of the present invention, after the U treatment, the above-described inorganic substance treatment can be performed as necessary.

  The auxiliary treatment carried out by the method A of the present invention assists the supercritical treatment or subcritical treatment. By employing this auxiliary treatment, the U treatment can be performed in a short time, and the organic substance is contained. A small amount of waste water can be obtained.

  In supercritical water or subcritical water treatment, most organic substances are converted into gaseous products and volatile substances by hydrolysis and thermal decomposition reactions, and then the organic substances are volatilized with water in a single hour by the presence of oxygen. It can be decomposed into sex gases.

Furthermore, the inorganic substance treatment using 12CaO · 7Al ₂ O ₃ acts as a decomposition catalyst for organic substances by heating. In particular, when heated in the presence of oxygen, the inorganic substance itself generates oxygen radicals to promote the decomposition of organic substances. To do. When microwaves are used as the heating means, heating in a short time is possible, and it is also effective for generating oxygen radicals.

  In addition, the inorganic substance treatment using an alkaline earth metal is a water-soluble curing agent in which the hydroxyl ion of the inorganic substance is contained in, for example, melamine-cured paint wastewater that is generally used as a thermosetting paint at present. This has the effect of promoting the hydrolysis of the alkyl ether bond of the alkyl etherified melamine.

In the method B of the present invention, wastewater containing an organic substance is subjected to auxiliary treatment for assisting supercritical treatment or subcritical treatment, followed by supercritical or subcritical treatment, and then treatment including biological treatment. It is the purification method of the wastewater containing the organic substance characterized by purifying by this.
In the method B, it is preferable to perform a process for assisting the U process before the U process.

  The auxiliary treatment can be at least one treatment selected from a flocculant separation treatment, a sedimentation separation treatment, a flotation separation treatment, and a filtration treatment.

The auxiliary processing a particular redox processes, particular microwave treatment can be a particular inorganic substance treatment.

The redox process, Ru particular electrolysis process der.

  In the method B of the present invention, supercritical treatment or subcritical treatment and treatment with an inorganic substance can be performed simultaneously.

  In the method B of the present invention, treatment with an inorganic substance can be performed between the supercritical treatment or subcritical treatment and the biological treatment.

  According to the method B of the present invention, microwave treatment and treatment with an inorganic substance can be performed simultaneously.

In order to perform the electrical degradation process, the waste water containing organic substances, is supplied to the electrolytic cell comprising an aluminum electrode, you use a method of using sodium nitrate as the electrolyte.

Inorganic substances, 12CaO · 7Al ₂ O _3, Ru least one inorganic compound der selected from among hydroxides of oxides and alkaline earth metal of the alkaline earth metals.

In the step of treating with inorganic substances, it intends line heating.

The auxiliary process used in the method B is implemented by the same method and conditions as the auxiliary process shown in the method A. For details, refer to the description regarding the auxiliary process shown in the method A. Also in the method B, as in the method A, it is essential to perform the microwave treatment and the treatment with 12CaO · 7Al ₂ O ₃ simultaneously under the heating by the microwave.

The U treatment in the method B is for the purpose of decomposing the organic substances contained in the waste liquid containing the organic matter that has been easily oxidatively decomposed by the auxiliary treatment, and oxidizing the supercritical or subcritical water. It is processing of.
This U process can be performed in the same manner as the U process in the A method. For details, refer to the description of the U process shown for the A method.

  In the method B of the present invention, biological treatment is performed after the U treatment.

  The biological treatment is a method in which a microorganism is supported on an organic or inorganic carrier and the organic matter in the wastewater is decomposed by the microorganism, and is more efficient than the activated sludge method. Examples of the material of the organic carrier include a photocurable resin, polyurethane, polyvinyl alcohol, polyethylene, polyacrylamide, polyester, polypropylene, agar, alginic acid, carrageenan, cellulose, dextran, agarose, ion exchange resin, and the like. It is not limited to these, In addition, these and an inorganic substance can also be used together.

  What is necessary is just to select suitably from conventionally well-known aerobic bacteria and anaerobic bacteria as microorganisms used for biological treatment. Examples of the aerobic bacterium include Pseudomonas genus and Ashitobacter genus. Examples of the anaerobic bacteria include methane bacteria and Clostridium bacteria. The biological treatment can be performed, for example, under conditions of a treatment temperature of 10 to 40 ° C., pH 6.0 to 9.0, and hydraulic retention time (HRT) of 24 to 48 hours.

  The auxiliary treatment carried out in the method B of the present invention is a chemical or physical auxiliary for supercritical treatment or subcritical treatment, which can be carried out in a short time, and the organic substance Wastewater with a low content can be obtained. Further, according to this auxiliary treatment, the organic substance contained in the wastewater can be directly decomposed, or the hardly decomposable organic substance that cannot be decomposed by the U treatment can be preliminarily decomposed into easily decomposable organic substances.

  Supercritical water or subcritical water is particularly useful as a reaction solvent during the oxidative decomposition of organic substances because the boundary between water and oxygen gas-liquid is eliminated and it exists as single-phase supercritical water or subcritical water. It is.

  In supercritical water treatment or subcritical water treatment, most organic substances are converted into gaseous products and volatile substances by hydrolysis and thermal decomposition reactions, and then mixed with oxygen for a single time. And can be broken down into volatile gases.

Furthermore, in the inorganic substance treatment using 12CaO · 7Al ₂ O ₃ , the inorganic substance acts as a decomposition catalyst for organic substances by heating. In particular, when heated in the presence of oxygen, the inorganic substance itself generates oxygen radicals. Promote the decomposition of organic matter. When microwaves are used as the heating means, heating in a short time is possible and generation of oxygen radicals is promoted.

  Further, in the inorganic substance treatment using alkaline earth metal, the hydroxyl ion of the inorganic substance is, for example, a water-soluble curing agent contained in melamine curable coating wastewater generally used as a thermosetting paint at present. There is an effect of promoting hydrolysis of the alkyl ether bond portion of the alkyl etherified melamine curing agent.

The method B of the present invention is capable of decomposing organic substances that could not be oxidatively decomposed by supercritical processing or subcritical processing by combining biological processing with supercritical processing or subcritical processing.
The method C of the present invention contains an organic substance characterized in that wastewater containing an organic substance is subjected to a biological treatment and then purified by a treatment including a supercritical treatment or a subcritical treatment. This is a method for purifying wastewater.
Hereinafter, the method C will be described in detail.

In the method C of the present invention, a specific treatment is performed before the biological treatment. This specific treatment is, for example, at least one physical treatment (solid-liquid separation treatment) selected from a flocculant separation treatment, a sedimentation separation treatment, a flotation separation treatment, and a filtration treatment. However, also in the C method, like the A method and the B method, in this specific treatment, it is essential that the microwave treatment and the treatment with 12CaO · 7Al ₂ O ₃ are simultaneously performed under the heating by the microwave.
In the method C, a specific intermediate treatment for promoting the decomposition of the biological treatment and / or the supercritical treatment or the subcritical water treatment can be performed between the solid-liquid separation treatment and the biological treatment.
The intermediate treatment is a specific oxidation-reduction treatment, a specific microwave treatment, or a treatment with a specific inorganic substance.

In the method C of the present invention, treatment with an inorganic substance can be performed between biological treatment and supercritical treatment or subcritical treatment.
In the present invention method C, in order to perform the electrical decomposition treatment, the wastewater containing organic material is supplied to the electrolytic cell comprises an aluminum electrode, to use sodium nitrate as the electrolyte.
Inorganic substances, 12CaO · 7Al ₂ O _3, Ru least one inorganic compound der selected from among hydroxides of oxides and alkaline earth metal of the alkaline earth metals.
Treatment with inorganic substances, intends row while heating.
The heating can be performed by microwave treatment.
The biological treatment used in the method C of the present invention can be carried out in the same manner as the biological treatment shown in the method B. For details, see the description of the biological treatment shown in the method B. I want to be.
The supercritical processing or subcritical processing used in the method C of the present invention can be carried out in the same manner as the method shown for the method A. For details, see the description shown in the method A. .

  In the present invention, before the biological treatment, an auxiliary treatment for assisting the purification treatment by the biological treatment (primary treatment), supercritical treatment, or subcritical treatment (secondary treatment) can be performed. By this treatment, the U treatment can be performed in a short time, and waste water with a low content of organic substances can be obtained. Such auxiliary treatment includes a physical method (Phy method) and a chemical method (Chem method). These auxiliary processes can be carried out in the same manner as the auxiliary processes (Phy process, Chem process) used in the method A. For details, refer to the description of the auxiliary process in the method A.

The Phy treatment, agglutination agent separation, sedimentation process, flotation process, Ru with at least one physical treatment selected from the filtration process. These pretreatments can be carried out in the same manner as the Phy method shown in the above-mentioned method A. For details, refer to the description of the Phy method.

  Waste water containing the remaining organic substance from which sludge has been removed by the Phy treatment is subjected to a Chem treatment as necessary, and then subjected to a biological treatment which is a primary treatment.

  The filtration treatment used in the Phy treatment can be performed under normal pressure or under pressure using, for example, a screen, cloth, filter, sieve or the like. The treatment can be used alone or in combination of two or more.

  The Chem treatment can be carried out in the same manner as the Chem method shown in the above-mentioned Method A. For details, refer to the description of the Chem method.

  The Phy process or the Chem process performed in the method C of the present invention can be performed alone, or can be performed in combination with the Chem process after performing the Phy process. When implemented in combination, particularly when the solid content of the wastewater is high, it is preferable to perform the Chem treatment after removing the solid content by the Phy treatment.

Further, the treatment using the inorganic substance can be performed between the biological treatment and the supercritical water treatment or the subcritical water treatment.
In order to perform the treatment using this inorganic substance, the inorganic substance is added to the wastewater, and then the supercritical state or the subcritical state is obtained. In this way, the inorganic substance treatment and the supercritical treatment or subcritical treatment can be performed simultaneously.

In method C, COD _Mn is less than 1,000 mg / liter, preferably less than 500 mg / liter, less than TOC 1,000 mg / liter, preferably less than 500 mg / liter, BOD 1,000 mg in coating wastewater by supercritical treatment or subcritical treatment. / Liter, preferably less than 500 mg / liter, organic solvent less than 1 mg / liter, preferably less than 0.5 mg / liter.

  If it is purified to the above level, the waste water is discharged as it is, otherwise the treated water after the above U treatment is used as return water, and the Chem treatment or biological treatment is performed again to purify to the above level. Is desirable.

  The Phy treatment and Chem treatment carried out as an auxiliary treatment in the method C of the present invention chemically or physically assist biological treatment, supercritical treatment or subcritical treatment. By adopting this auxiliary treatment, the U treatment can be performed in a short time, and waste water with a low content of organic substances can be obtained.

Hereinafter, the present invention will be described in more detail with reference to examples. In Examples 1 to 12 of the examples is described as an example of performing simultaneously a process by microwave treatment and 12CaO · 7Al ₂ O ₃ under the heating by the microwave Examples 3 and 7, 11 and other examples correspond to reference examples in the present invention.

Example 1
A water-based paint for automobiles (polyester / melamine curable type, solid content 22.3% by weight) diluted with water to a solid content of 2% by weight was used as a paint wastewater sample (A). The initial COD _Mn in this sample (A) was 8,500 mg / liter, TOC was 11,000 mg / liter, and the amount of melamine curing agent was 3.49 × 10 ³ mV · sec. The amount of the melamine curing agent here indicates the product (area) of the detection potential and the detection time indicating the melamine curing agent in high performance liquid chromatography (HPLC) (hereinafter, the same meaning is shown).
A sodium nitrate solution is mixed with 280 g of this paint wastewater sample (A) so as to have a concentration of 0.02 mol / liter, and the mixed solution is put into an electrolytic cell. ^Two 35 cm ² aluminum electrode plates were placed so that the distance between the electrodes was 20 mm, and electrolysis was performed under the condition of energizing at a voltage of 10 V for 0.17 hours.
Subsequently, the obtained electrolyzed water was filtered, and 100 parts by weight of the filtrate was mixed with 5 parts by weight of H ₂ O ₂ and treated at 500 ° C. under 25 MPa supercritical water for 30 minutes. . Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 2
Add 15,000 mg of flocculant Chrystuck B100 (made by Kurita Kogyo Co., Ltd.) and 1,500 mg of Chrystak B450 (made by Kurita Kogyo Co., Ltd.) to 280 g of the same paint wastewater (A) as above, and leave it for one day. The agglomerates were removed. The COD _Mn of the treatment liquid (B) after this aggregation treatment was 5,800 mg / l and the TOC was 6,800 mg / l. The treatment liquid (B) was irradiated with microwaves (frequency 2.45 GHz, output 500 W) for 5 minutes.

Next, 100 parts by weight of the obtained microwave-treated water was mixed with 5 parts by weight of H ₂ O ₂ and treated at 500 ° C. under 25 MPa supercritical water for 30 minutes. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent in the treatment liquid.

Example 3
An amount of 12CaO · 7Al ₂ O ₃ (obtained by firing at 1250 ° C. for 3 hours in a pure oxygen atmosphere) corresponding to 10% by weight of the treatment solution (B) obtained in Example 2 was treated with the treatment solution ( After being added to B) and stirred, microwaves (frequency: 2.45 GHz, output: 500 W) were irradiated for 10 minutes. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent of the treatment liquid (C) after the 12CaO · 7Al ₂ O ₃ treatment.

It was then performed and the resulting treated water 100 parts by weight with respect to _H 2 _{O 2} to 5 parts by weight blended ones for 30 minutes treated with supercritical water under 25MPa at 500 ° C.. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent in the treatment liquid.

Example 4
An amount of calcium hydroxide corresponding to 10% by weight of the treatment liquid (B) obtained in Example 2 was added to the treatment liquid (B) and stirred, and then microwaves (frequency 2.45 GHz, output 500 W) were used. Was irradiated for 10 minutes. COD _Mn in the processing liquid after treatment of this (C), TOC, a melamine curing agent amount shown in Table 1.

It was then performed and the resulting treated water 100 parts by weight with respect to _H 2 _{O 2} to 5 parts by weight blended ones for 30 minutes treated with supercritical water under 25MPa at 500 ° C.. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent in the treatment liquid.

Comparative Example 1
In Example 1, the treatment was performed in the same manner as in Example 1 except that the supercritical water treatment was not performed. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent in the treatment liquid.

Comparative Example 2
In Example 2, the treatment was performed in the same manner as in Example 2 except that the supercritical water treatment was not performed. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent in the treatment liquid.

Comparative Example 3
In Example 3, the treatment was performed in the same manner as in Example 3 except that the supercritical water treatment was not performed. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent in the treatment liquid.

Comparative Example 4
In Example 4, the treatment was performed in the same manner as in Example 4 except that the supercritical water treatment was not performed. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent in the treatment liquid.

In Table 1, the unit of COD _Mn is mg / liter, the unit of TOC is mg / liter, and the unit of the amount of melamine curing agent is mV · sec.

Example 5
A sodium nitrate solution was mixed with 280 g of the paint wastewater sample (A) shown in Example 1 so as to have a concentration of 0.02 mol / liter. ^Two aluminum electrode plates having an area (one side) of 35 cm ² were placed so that the distance between the electrodes was 20 mm, and electrolysis was performed under the condition of energizing at a voltage of 10 V for 0.17 hours.
Subsequently, the obtained electrolyzed water was filtered, and 100 parts by weight of the filtrate was mixed with 5 parts by weight of H ₂ O ₂ and treated at 500 ° C. under 25 MPa supercritical water for 30 minutes. .

Next, the treatment liquid is put into a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium is used, and the treatment temperature is 20 to 25 ° C., pH 7 After biological treatment was performed under conditions of ˜8.5 and hydraulic residence time of 48 hours, the biologically treated water was filtered. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 6
Add 15,000 mg of flocculant Chrystuck B100 (made by Kurita Kogyo Co., Ltd.) and 1,500 mg of Chrystak B450 (made by Kurita Kogyo Co., Ltd.) to 280 g of the same paint wastewater (A) as above, and leave it for one day. The agglomerates were removed. The COD _Mn of the treatment liquid (B) after this aggregation treatment was 5,800 mg / l and the TOC was 6,800 mg / l. The treatment liquid (B) was irradiated with microwaves (frequency 2.45 GHz, output 500 W) for 5 minutes.

  Next, the obtained microwave treated water was treated at 500 ° C. under 25 MPa supercritical water for 30 minutes.

Then, the treatment liquid is put into a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium is used, and the treatment temperature is 20 to 25 ° C., pH 7 to After biological treatment was performed under conditions of 8.5 and a hydraulic residence time of 48 hours, the biologically treated water was filtered. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 7
An amount of 12CaO.7Al ₂ O ₃ (obtained by firing at 1250 ° C. for 3 hours in a pure oxygen atmosphere) corresponding to 10% by weight of the treatment liquid (B) obtained in Example 6 was treated with the treatment liquid ( After being added to B) and stirred, microwaves (frequency: 2.45 GHz, output: 500 W) were irradiated for 10 minutes. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent of the treatment liquid (C) after the 12CaO · 7Al ₂ O ₃ treatment.

It was then performed and the resulting treated water 100 parts by weight with respect to _H 2 _{O 2} to 5 parts by weight blended ones for 30 minutes treated with supercritical water under 25MPa at 500 ° C..

Next, the treatment liquid is put into a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium is used, and the treatment temperature is 20 to 25 ° C., pH 7 After performing the biological treatment under the conditions of ˜8.5 and hydraulic residence time of 48 hours, the biologically treated water was filtered. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 8
An amount of calcium hydroxide corresponding to 10% by weight of the treatment liquid (B) obtained in Example 6 was added to the treatment liquid (B) and stirred, and then microwaves (frequency 2.45 GHz, output 500 W) were obtained. Was irradiated for 10 minutes. COD _Mn of treatment liquid after treatment of this (C), TOC, a melamine curing agent amount shown in Table 2.

It was then performed and the resulting treated water 100 parts by weight with respect to _H 2 _{O 2} to 5 parts by weight blended ones for 30 minutes treated with supercritical water under 25MPa at 500 ° C..

Next, the treatment liquid is put into a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium is used, and the treatment temperature is 20 to 25 ° C., pH 7 After performing the biological treatment under the conditions of ˜8.5 and hydraulic residence time of 48 hours, the biologically treated water was filtered. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 5
In Example 5, the treatment was performed in the same manner as in Example 5 except that the supercritical water treatment was not performed. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 6
In Example 6, the treatment was performed in the same manner as in Example 6 except that the supercritical water treatment was not performed. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 7
In Example 7, the treatment was performed in the same manner as in Example 7 except that the supercritical water treatment was not performed. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 8
In Example 8, the treatment was performed in the same manner as in Example 8 except that the supercritical water treatment was not performed. Table 2 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 9
A sodium nitrate solution was mixed with 280 g of the paint wastewater sample (A) shown in Example 1 so as to have a concentration of 0.02 mol / liter. ^Two aluminum electrode plates having an area (one side) of 35 cm ² were placed so that the distance between the electrodes was 20 mm, and electrolysis was performed under the condition of energizing at a voltage of 10 V for 0.17 hours.
Next, the obtained electrolyzed water is filtered, and then the filtrate is put into a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium Was used for biological treatment under conditions of a treatment temperature of 20 to 25 ° C., a pH of 7 to 8.5 and a hydraulic retention time of 48 hours, and then the biologically treated water was filtered. Next, a mixture of 5 parts by weight of H ₂ O ₂ with respect to 100 parts by weight of the filtrate was treated at 500 ° C. under 25 MPa supercritical water for 30 minutes. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 10
Add 15,000 mg of flocculant Chrystuck B100 (made by Kurita Kogyo Co., Ltd.) and 1,500 mg of Chrystak B450 (made by Kurita Kogyo Co., Ltd.) to 280 g of the same paint wastewater (A) as above, and leave it for one day. The agglomerates were removed. The treatment liquid (B) after the aggregation treatment was irradiated with microwaves (frequency: 2.45 GHz, output: 500 W) for 5 minutes.

Then, the obtained microwave treated water is put into a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium is used, and the treatment temperature is 20 to After biological treatment was carried out under conditions of 25 ° C., pH 7 to 8.5, and hydraulic residence time 48 hours, the biological treated water was filtered. Next, a mixture of 5 parts by weight of H ₂ O ₂ with respect to 100 parts by weight of the filtrate was treated at 500 ° C. under 25 MPa supercritical water for 30 minutes. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 11
An amount of 12CaO.7Al ₂ O ₃ (obtained by firing at 1250 ° C. for 3 hours in a pure oxygen atmosphere) corresponding to 10% by weight of the treatment liquid (B) obtained in Example 10 was treated with the treatment liquid ( After being added to B) and stirred, microwaves (frequency: 2.45 GHz, output: 500 W) were irradiated for 10 minutes. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent of the treatment liquid (C) after the 12CaO · 7Al ₂ O ₃ treatment.

  Next, the treatment liquid is put into a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium is used. After performing the biological treatment under the conditions of ˜8.5 and hydraulic residence time of 48 hours, the biologically treated water was filtered.

Then, 5 parts by weight of H ₂ O ₂ converted to 100% by weight with respect to 100 parts by weight of the obtained treated water was treated at 500 ° C. under 25 MPa supercritical water for 30 minutes. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Example 12
After adding calcium hydroxide in an amount corresponding to 10% by weight of the treatment liquid (B) obtained in Example 10 to the treatment liquid (B) and stirring, microwave (frequency 2.45 GHz, output 500 W) Was irradiated for 10 minutes. The treated liquid (C) after this treatment is put in a biological reaction tank, and activated sludge having aerobic bacteria of the genus Pseudomonas, Ashitobacter, Rhodococcus, Bacillus, Candida and Fusarium is used. After biological treatment was carried out under conditions of 25 ° C., pH 7 to 8.5, and hydraulic residence time 48 hours, the biological treated water was filtered.

It was then performed and the resulting treated water 100 parts by weight with respect to _H 2 _{O 2} to 5 parts by weight blended ones for 30 minutes treated with supercritical water under 25MPa at 500 ° C.. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 9
In Example 9, the treatment was performed in the same manner as in Example 9 except that the supercritical water treatment was not performed. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 10
In Example 10, the treatment was performed in the same manner as in Example 10 except that the supercritical water treatment was not performed. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 11
In Example 11, the treatment was performed in the same manner as in Example 11 except that the supercritical water treatment was not performed. Table 3 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Comparative Example 12
In Example 12, the treatment was performed in the same manner as in Example 12 except that the supercritical water treatment was not performed. Table 1 shows the amounts of COD _Mn , TOC, and melamine curing agent.

Claims (3)

Purification treatment of wastewater containing organic substances, after purifying wastewater containing organic substances by auxiliary treatment to assist supercritical treatment or subcritical treatment, followed by treatment including supercritical treatment or subcritical treatment In the method
The purification treatment method, wherein the auxiliary treatment includes a treatment in which at least a microwave treatment and a treatment with 12CaO · 7Al ₂ O ₃ are simultaneously performed under heating by the microwave . An organic substance that purifies wastewater containing organic substances by supercritical treatment or subcritical treatment after performing auxiliary treatment to assist supercritical treatment or subcritical treatment, and then treatment including biological treatment In the method for purifying wastewater containing
The purification treatment method, wherein the auxiliary treatment includes a treatment in which at least a microwave treatment and a treatment with 12CaO · 7Al ₂ O ₃ are simultaneously performed under heating by the microwave . In a purification method for wastewater containing organic substances, the wastewater containing organic substances is subjected to biological treatment and then purified by treatment including supercritical treatment or subcritical treatment.
A purification treatment method comprising performing at least a microwave treatment and a treatment with 12CaO.7Al ₂ O ₃ simultaneously under the heating by the microwave before the biological treatment .