JP4933734B2 - Treatment of water containing persistent substances - Google Patents

Description

  The present invention relates to a method for treating water containing a hardly decomposable substance such as dioxins and other endocrine disrupting substances.

  In Japan, the Act on Special Measures against Dioxins was enacted in 1999, and in the Act on Special Measures against Dioxins, the emission standard for dioxins is regulated to 10 pg-TEQ / L or less. On the other hand, wastewater from incinerator demolition work, industrial wastewater from certain facilities, and some soil leachate may contain high-concentration dioxins that greatly exceed these standards. Development of is strongly desired.

  In addition, endocrine disrupting substances such as bisphenol other than dioxins (so-called environmental hormones and endocrine disrupting chemical substances) and various organochlorine compounds represented by trichloroethane are also non-degradable substances, and their emission standards are On the other hand, as with the dioxins described above, development of a reduction treatment technique or removal technique is strongly desired.

  As a method of removing the substance from waste water (contaminated water) containing these hardly decomposable substances, for example, as the removal of dioxins, the waste water is directly decomposed by ozone, photolysis, chemical decomposition of dioxin by hydrogen peroxide, Decomposition by microorganisms, separation and removal using an adsorbent and a flocculant, and the like are performed. However, such a separation and removal technique directly processes the diluted solution, and therefore, it is inefficient and requires a large capital investment. In addition, when the wastewater is contaminated at a high concentration, it may not be possible to satisfy the discharge standard, and it is not a preferable means.

  As a means for detoxifying such a hardly decomposable organic compound, for example, as a method for removing dioxins, ozone, photolysis, chemical decomposition by hydrogen peroxide, decomposition by microorganisms, adsorption on the dioxins Means such as separation and removal using an agent and a flocculant are known. Among these, in order to simplify the operation, a treatment for detoxifying the dioxins by adding an oxidant and chemically decomposing it is used. As an oxidant for chemically decomposing dioxins, For example, a technique using a persulfate is provided (for example, Patent Document 1 and Patent Document 2).

On the other hand, a step of settling the contaminated water, a step of filtering through a net having an average pore size of 10 to 100 μm, a step of catalytically decomposing the permeate by irradiating it with ultraviolet light in the presence of a photocatalyst powder, and then an ultrafiltration membrane The technique about the waste water treatment method which performs the process processed by this is reported (for example, patent document 3).
Also, a treatment method has been proposed in which wastewater is subjected to a separation treatment with a reverse osmosis membrane (RO membrane) and then introduced into an oxidation treatment step in which the concentrated solution is chemically decomposed with active oxygen (for example, Patent Documents). 4 and Patent Document 5).

  Moreover, as a technique for preventing the discharge of a hardly decomposable substance, for example, a physical method, a chemical method, and a biological method are known. There is an adsorption method as one of physical methods, and an adsorption method by introducing activated carbon into water (for example, see Non-Patent Document 1) and a method of introducing activated carbon into exhaust gas have been developed. However, in this case, the activated carbon having adsorbed the hardly decomposable substance still retains the hardly decomposable substance therein and cannot be discarded as it is.

  Therefore, the activated carbon used for this adsorption is incinerated, pyrolyzed, or landfilled and disposed of, but it is discharged together with the exhaust gas to cause secondary pollution or elute from the landfill. Therefore, a safe and economical treatment method is desired.

  The methods for decomposing refractory materials in wastewater containing refractory substances, soil, and sludge include thermal decomposition methods, chemical decomposition methods using alkali, methods using supercritical fluids, and processes such as ozone and hydrogen peroxide. There are methods using a combination of oxides or hypochlorite and ultraviolet rays, and further, biological methods using white rot fungi, enzymes produced by microorganisms, and the like have been studied.

  Each of these methods has its own characteristics, and there are cases where it is easy to apply and cases where it is difficult to apply depending on the presence state of the hardly decomposable substance. For example, thermal decomposition and supercritical water decomposition require expensive equipment and energy, and are often difficult to use economically. In addition, the method of combining ozone, hydrogen peroxide, and ultraviolet rays cannot be applied to suspensions that are difficult to transmit ultraviolet rays or solids such as soil and sludge. For this reason, wastewater containing suspended solids and suspended solids is processed after the suspended solids and suspended solids are removed by filtration or sedimentation once, but they are hardly decomposed by the suspended solids or suspended solids. Sexual substances must be detoxified separately.

For waste water, various chemical decomposition methods combining hydrogen peroxide and iron salt and chemical decomposition methods using persulfate and permanganate have been proposed.
For example, Patent Document 6 discloses a treatment method that can remove an endocrine disrupting substance to a low concentration in a short time with a simple apparatus and operation. In this technique, the endocrine disrupting substance-containing water is adsorbed by activated carbon or the like, concentrated by desorption, and contacted with a peroxide such as persulfate, and decomposed. In general, harmful substances such as endocrine disrupting substances are problematic in that the more complicated the operation, the higher the possibility of recontamination of the human body and the surrounding environment.

  Therefore, if it can be decomposed as it is without eluting the hardly decomposable substance adsorbed on the solid, the operation is simple and the risk of recontamination of the human body and the surrounding environment can be avoided. It is possible to reuse the adsorbent used for adsorptive separation of difficult-to-decompose substances and to transport the material to be processed, and it has many industrial advantages, such as being applicable to soil and sludge solid contaminants. Development is desired.

Hereinafter, the treatment of waste water containing a hardly decomposable substance will be described in detail.
Sources of wastewater containing refractory substances include chlorinated bleaching facilities in kraft pulp manufacturing plants, decomposition facilities for waste PCBs or PCB processed products, cleaning facilities for PCB contaminated materials or PCB processed products, and production of aluminum and aluminum alloys Waste gas cleaning equipment, wet dust collection equipment, waste pits for discharging sewage and the like related to melting furnaces and the like for use are known.

  In addition, the Environmental Agency revised the standards for water-environmental pollutants, and organic compounds such as trichlorethylene, tetrachloroethylene, and PCB were newly added to the target substances for environmental standards that had been mainly heavy metals.

  Conventionally, a technology has been developed that removes hardly decomposable substances from treated water containing hardly decomposable harmful substances by using filtration devices, membrane separation methods, etc. as much as possible, and decomposes the hardly decomposable substances in the treated water. . (For example, see Patent Document 7)

  In order to treat wastewater containing persistent substances as described above, filtration treatment, biological treatment, etc. are applied as pretreatment, and ozone treatment, ultraviolet irradiation treatment, catalyst treatment, activated carbon treatment, etc. are applied as posttreatment. The Thus, until now, it had to be disassembled and removed using a great deal of labor and materials.

  In addition, taking the ultraviolet irradiation treatment as an example, it is a technique that can be used only in a reaction system that can transmit ultraviolet rays, and there is a problem that it cannot be used for a liquid containing a solid or a solid. Further, the hardly decomposable substance removed by the pretreatment needs to be made harmless separately in order to prevent secondary contamination.

Therefore, it is strongly desired to develop a technology for efficiently decomposing these hardly decomposable substances using a closed system that does not recontaminate the human body and the surrounding environment.

JP 2003-93999 A JP 2003-285043 A JP 2003-144857 A Japanese Patent Laid-Open No. 11-347591 JP 2000-354894 A JP 2000-189945 A JP-A-11-99395 Directed by Naomichi Hirayama, “Countermeasures against dioxins” published by CMC, 197-205 (1998)

  However, in the case where persulfate is added to the hardly decomposable organic compound and the compound is chemically decomposed as disclosed in Patent Document 1 and Patent Document 2 described above, the hardly decomposable organic compound is used. Since the decomposition efficiency of the compound is low, it was extremely difficult to cope with a high concentration. On the other hand, as a means for treating such a high concentration of hardly decomposable organic compound, a metal salt such as ruthenium salt may be added to persulfate, but such a metal salt is very expensive. In terms of cost, it was not practical.

  In the technique as disclosed in Patent Document 3, in the case of waste water with a small amount of solids in the decomposed product, a solid deposited film layer in the decomposed product is not formed on the metal mesh. In some cases, the dissolved dioxin permeated through the metal mesh, resulting in insufficient treatment.

  In the techniques disclosed in Patent Document 4 and Patent Document 5, when free chlorine is present in contaminated water, it is necessary to add a reducing substance such as bisulfite excessively in order to neutralize this. However, since this bisulfite and the like inhibit chemical decomposition, it cannot be said to be a means for efficiently separating and removing hardly decomposable substances.

  Therefore, the object of the present invention is to concentrate non-degradable substances such as dioxins contained in contaminated water (treated raw water) such as incinerator demolition construction wastewater, industrial wastewater from specified facilities, and some soil leachate. In addition to being able to be applied to water containing reducing substances such as bisulfite that neutralizes free chlorine, it is not restricted by the properties of the hard-to-decompose substances contained, and is made harmless efficiently and at low cost. An object of the present invention is to provide a method for treating water containing a hardly decomposable substance.

  The present invention provides a method for effectively decomposing a hardly decomposable substance adsorbed on a solid under the above-described conditions as it is without performing an operation such as desorption, and the hardly decomposable substance It is an object of the present invention to provide a method for regenerating an adsorbent used for the adsorption separation of slag.

  Furthermore, the present invention relates to a wastewater treatment method capable of adsorbing and separating a hardly decomposable substance from waste water containing a harmful hardly decomposable substance, efficiently decomposing the separated hardly decomposable substance in a solid state, and enabling a closed system. The second object is to provide the above.

  And this invention combines various separation processes and decomposition processes, and even when the concentration of the hardly decomposable substance in the wastewater fluctuates, a reliable wastewater treatment system that can reliably meet the discharge standards. The third purpose is to provide it.

In order to achieve the above object, the present inventors have conducted intensive research and combined a concentration technique, a chemical decomposition technique, and / or a photodegradation technique by membrane separation, and thereby a hardly decomposable substance such as dioxin in waste water or waste. It has been found that the concentration of can be reduced to lower levels.
Also, a salt contained in sewage or the like by combining a treatment with a reverse osmosis membrane (RO membrane) or nanofilter membrane (NF membrane) capable of concentrating salt and an ultrafiltration membrane (UF membrane) through which the salt passes. It was found that the increase in osmotic pressure due to concentration in the process can be suppressed, and the decrease in filtration capacity can be suppressed.
Furthermore, by using titanium dioxide with high adsorption efficiency as an adsorbent, the efficiency of chemical decomposition can be increased. At the same time, since titanium dioxide functions as a photocatalyst, it is used as a catalyst in photolysis and combined with photolysis. Thus, the present inventors have found that a highly reliable treatment system for water containing hardly decomposable substances can be provided, and the present invention has been completed.

That is, this invention provides the processing method and processing apparatus of the following hardly decomposable substance containing water.
[1] The following steps:
(B) A process of adding an adsorbent to water containing hardly decomposable substance (processed raw water) and adsorbing the hardly decomposable substance to the adsorbent (adsorption treatment process)
(C) A step of separating the adsorbent adsorbing the hardly decomposable substance using a filtration membrane to obtain water concentrated with the adsorbent adsorbing the hardly decomposable substance (membrane filtration treatment step)
(D) The hardly decomposable substance adsorbed on the separated adsorbent is brought into contact with a peroxide to the hardly decomposable substance without performing a desorption operation from the adsorbent. Process of chemical decomposition (chemical decomposition process)
A method for treating water containing a hardly decomposable substance, comprising:
[2] The method for treating hardly decomposable substance-containing water according to the above [1], wherein in the step (D), the peroxide is used in an amount of 100 times mol or more with respect to the hardly decomposed substance.
[3] Further, (A) a step of obtaining water in which the hardly decomposable substance is concentrated from the water containing the hardly decomposable substance using a reverse osmosis membrane (RO membrane) or a nanofilter membrane (NF membrane) (membrane concentration treatment) Process)
The method for treating water containing a hardly decomposable substance according to the above [1] or [2].
[4] Treatment of water containing hardly decomposable substance according to any one of the above [1] to [3], further comprising (E) a step of neutralizing chlorine in water containing hardly decomposable substance (chlorine neutralizing process) Method.
[5] The method for treating water containing a hardly decomposable substance according to any one of the above [1] to [4], further comprising (F) a step (photodecomposition step) of decomposing the hardly decomposable substance by irradiation with ultraviolet rays. .
[6] (G) A step of backwashing the filtration membrane from which the adsorbent that has adsorbed the hardly decomposable substance in the step (C) is obtained to obtain water in which the adsorbent adsorbing the hardly decomposable substance is concentrated (reverse Washing process)
The method for treating hardly-decomposable-substance-containing water according to any one of [1] to [5] above.
[7] Further, (H) a step of adding an aggregating agent to water in which the adsorbent adsorbing the hardly decomposable substance is concentrated, and aggregating and sedimenting the adsorbent adsorbing the hardly decomposable substance (aggregating and separating step) )
The method for treating hardly-decomposable-substance-containing water according to any one of the above [1] to [6].
[8] The adsorbent added in the step (B) is one or two selected from the group consisting of titanium dioxide, zeolite, acid clay, activated clay, diatomaceous earth, metal oxide, metal powder, activated carbon and carbon black. The method for treating hardly-decomposable substance-containing water according to any one of the above [1] to [7], which is an inorganic adsorbent of a kind or more.
[9] The method for treating hardly decomposable substance-containing water according to the above [8], wherein the adsorbent added in the step (B) is titanium dioxide.
[10] The filtration membrane used in the step (C) is selected from the group consisting of an ultrafiltration membrane (UF membrane), a nanofilter membrane (NF membrane), a microfiltration membrane (MF membrane), and a reverse osmosis membrane (RO membrane). The method for treating hardly-decomposable substance-containing water according to any one of [1] to [9] above.
[11] The method for treating hardly decomposable substance-containing water according to any one of [1] to [10], wherein the peroxide used in the step (D) is a persulfate.
[12] At least one of the water concentrated in the hardly decomposable substance obtained in the step (A) and / or the water concentrated in the adsorbent adsorbing the hardly decomposable substance obtained in the step (C). Part is added to the hardly decomposable substance-containing water (treated raw water), and at least one step selected from the group consisting of the step (A), the step (B) and the step (C) is performed again. The method for treating hardly decomposable substance-containing water according to any one of [1] to [11].
[13] An adsorbent addition unit for adding an adsorbent to water containing hardly decomposable substance (treated raw water),
A membrane filtration processing unit for separating the adsorbent adsorbing the hardly decomposable substance using a filtration membrane and concentrating the adsorbent adsorbing the hardly decomposable substance;
An apparatus for treating difficult-to-decompose substance-containing water, comprising a chemical decomposition unit for oxidatively decomposing the hardly-decomposable substance by adding a peroxide to the adsorbent adsorbing the hardly-degradable substance.
[14] A reducing substance input unit for supplying a reducing substance that neutralizes chlorine in the water into the hardly-decomposable substance-containing water (treated raw water);
A membrane concentration treatment unit for concentrating a hardly decomposable substance from water containing a hardly decomposable substance using a reverse osmosis membrane (RO membrane) or a nanofilter membrane (NF membrane);
An adsorbent addition unit for adding an adsorbent to the water in which the hardly decomposable substance is concentrated and adsorbing the hardly decomposable substance to the adsorbent;
A membrane filtration processing unit for separating the adsorbent adsorbing the hardly decomposable substance using a filtration membrane and concentrating the adsorbent adsorbing the hardly decomposable substance;
A flocculant addition unit for adding an aggregating agent to water in which the adsorbent adsorbing the hardly decomposable substance is concentrated, and aggregating the adsorbent adsorbing the hardly decomposable substance;
A solid-liquid separation unit for allowing the adsorbent adsorbing the hardly decomposable substance agglomerated by the flocculant to separate the precipitate and the supernatant into solid and liquid, and adding a peroxide to the sediment An apparatus for treating water containing a hardly decomposable substance, comprising a chemical decomposition part for oxidizing and decomposing the hardly decomposable substance in the product.

According to the present invention, a hardly decomposable substance such as dioxin contained in water can be efficiently decomposed and removed without being influenced by its concentration.
According to the present invention, it is possible to efficiently reduce a hardly decomposable substance contained in water to a lower level by combining chemical decomposition by an oxidizing agent and photolysis by ultraviolet irradiation, and a highly reliable treatment system. Can be provided.

  Furthermore, according to the present invention, the adsorbent can be regenerated by performing the chemical decomposition treatment as described above without performing a desorption operation in a state where the hardly decomposable substance is adsorbed to the solid. The adsorbent can be used repeatedly.

  Further, according to the method for treating water containing a hardly decomposable substance according to the present invention, water containing the hardly decomposable substance can be efficiently and safely treated by the closed system, and the water containing the hardly decomposable substance containing water is generated. Since all the treatments are completed, the need for transporting persistent materials that cause environmental pollution is eliminated, and the environment is not adversely affected.

Hereinafter, the present invention will be described in detail.
The method for treating hardly-decomposable substance-containing water of the present invention (hereinafter referred to as the method of the present invention) comprises the following steps:
(B) A process of adding an adsorbent to water containing hardly decomposable substance (processed raw water) and adsorbing the hardly decomposable substance to the adsorbent (adsorption treatment process)
(C) A step of separating the adsorbent adsorbing the hardly decomposable substance using a filtration membrane to obtain water concentrated with the adsorbent adsorbing the hardly decomposable substance (membrane filtration treatment step)
(D) The hardly decomposable substance adsorbed on the separated adsorbent is brought into contact with a peroxide to the hardly decomposable substance without performing a desorption operation from the adsorbent. It includes a step of chemically decomposing (chemical decomposition step).
In the method of the present invention, the hardly decomposable substance contained in water is concentrated and removed by membrane filtration treatment, and the concentrated hardly decomposable substance is detoxified by chemical decomposition and, if necessary, photodegradation. Is. The essential steps of the method of the present invention are shown in FIG.

  Examples of the hardly decomposable substance that can be detoxified by the method of the present invention include dioxins that are harmful pollutants in soil and sludge, other endocrine disrupting substances, and carcinogenic substances.

  Here, examples of dioxins include halogenated dibenzodioxins, halogenated dibenzofurans, PCBs (particularly, coplanar PCBs substituted with a chlorine atom in addition to the ortho position) and the like.

  Examples of halogenated dibenzodioxins include 2,3,7,8-tetrachlorodibenzo-P-dioxin, 1,2,3,7,8-pentachlorodibenzo-P-dioxin, 1,2,3, 4,7,8-hexachlorodibenzo-P-dioxin, 1,2,3,4,6,7,8-heptachlorodibenzo-P-dioxin, 1,2,3,4,6,7,8,9 -Octachlorodibenzo-P-dioxin and the like.

  Examples of halogenated dibenzofurans include 2,3,7,8-tetrachlorodibenzofuran, 1,2,3,7,8-pentachlorodibenzofuran, 1,2,3,4,7,8-hexachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzofuran, 1,2,3,4,6,7,8,9-octachlorodibenzofuran and the like.

  Examples of PCBs (particularly coplanar PCBs substituted with a chlorine atom other than the ortho position) include 3,3 ′, 4,4 ′, 5-tetrachlorobiphenyl, 3,3 ′, 4,4 ′, 5 -Pentachlorobiphenyl, 3,3 ', 4,4', 5,5'-hexachlorobiphenyl and the like.

  Examples of endocrine disrupting substances and carcinogenic substances other than dioxins include alkylphenols such as t-butylphenol, nonylphenol and octylphenol, halogenated phenols such as tetrachlorophenol and pentachlorophenol, and 2,2-bis (4 -Hydroxyphenyl) propane (bisphenol A), 1-bis) 4-hydroxyphenyl) cyclohexane and other bisphenols, benzopyrene, chrysene, benzoanthracene, benzofluoranthene, picene and other polycyclic aromatic hydrocarbons, dibutyl phthalate, Examples thereof include phthalic acid esters such as butylbenzyl phthalate and di-2-ethylhexyl phthalate.

  In addition to the dioxins and PCBs described above, refractory organic halogen compounds such as dichloropropane, trichloroethane, trichloroethylene, tetrachloroethylene and dichloroethylene can also be removed by photolysis or chemical decomposition by the method of the present invention. .

  The method of the present invention includes (B) an adsorption treatment step, (C) a membrane filtration treatment step, and (D) a chemical decomposition step, and if necessary, (A) a membrane concentration treatment step, (E) in chlorine. One or more steps selected from the group consisting of a summing step, (I) prefiltration step, (F) photolysis step, (G) backwashing step, and (H) agglomeration separation step may be included. Each of the above steps may be performed only once, or may be performed twice or more. By performing one or more of the above steps a plurality of times, it is possible to decompose and remove the hardly decomposable substance to a lower concentration with higher reliability. Hereinafter, each step will be described with reference to FIG.

(E) Chlorine neutralization step This is a step of neutralizing residual chlorine in water containing hardly decomposable substances. Since residual chlorine causes oxidation and deterioration of the reverse osmosis membrane, it is desirable to remove it in advance. Measure the chlorine concentration with a chlorine concentration meter and add an appropriate amount of reducing substance.
Examples of the reducing substance include sodium bisulfite, sodium metabisulfite, sulfur dioxide and the like, and sodium bisulfite is preferable.

(I) Prefiltration step In order to prevent clogging of the reverse osmosis membrane due to dust in the water containing the hardly decomposable substance, for example, it is a step of filtering with a 10 μm prefilter.

(A) Membrane concentration treatment step This is a step of obtaining water in which a hardly decomposable substance is concentrated from a hardly decomposable substance-containing water using a reverse osmosis membrane (RO membrane) or a nanofilter membrane (NF membrane). For example, the molecular weight of dioxin is 200 or more and can be separated at the molecular level by a reverse osmosis membrane or a nanofilter membrane. The reverse osmosis membrane and the nanofilter membrane do not allow permeation of not only the hardly decomposable substance but also salts contained in water. Therefore, since the salt is also concentrated at the same time, the osmotic pressure of the concentrated hardly decomposable substance-containing water increases, and the filtration performance decreases.
Here, “salt” includes all kinds of salts (inorganic salts of alkali metals) contained in water containing hardly decomposable substances, and main salts include sodium chloride, metabisulfite or heavy salt. Examples thereof include sulfites and sodium hydrogen sulfate. Since sodium chloride is produced when neutralizing residual chlorine, it is contained in a large amount of water containing a hardly decomposable substance to be treated.

  The operating pressure in the membrane concentration treatment with a reverse osmosis membrane is not particularly limited, but usually, the higher the operating pressure, the higher the removal rate of hardly decomposable substances such as dioxin, so it is higher than the general setting of 0.3 MPa. It is preferable to operate at 1 MPa or more, more preferably 1.5 MPa or more. Furthermore, in order to operate the reverse osmosis membrane for a long period of time and to prevent a reduction in the removal rate due to the concentration of circulating water, the ratio of the concentrated water and the permeated water may be appropriately determined according to the properties of the waste water, Is in the range of 1:99 to 80:20, preferably 30:70 to 60:40, particularly 50:50.

  Constituent materials for reverse osmosis membranes (hereinafter sometimes referred to as RO membranes) include polyamides (including crosslinked polyamides and aromatic polyamides), aliphatic amine condensates, heterocyclic polymers, and cellulose acetates. , Polyethylene-based, polyvinyl alcohol-based, and polyether-based resin materials.

The membrane form of the reverse osmosis membrane is not particularly limited, and can be an asymmetric membrane or a composite membrane.
Further, as the membrane module, a flat membrane type, a hollow fiber type, a spiral type, a cylindrical type, a breez type, etc. can be appropriately employed.

  The constituent material of the nanofilter membrane (NF membrane) includes polyamide (including cross-linked polyamide and aromatic polyamide), aliphatic amine condensate, heterocyclic polymer, cellulose acetate, polyethylene, and polyvinyl alcohol. Examples thereof include resin materials such as those based on polyether and polyether.

There is no restriction | limiting in particular as a film | membrane form of a nano filter film | membrane, It can be set as an asymmetric membrane or a composite film similarly to the above-mentioned reverse osmosis membrane.
In addition, as the membrane module, a flat membrane type, a hollow fiber type, a spiral type, a cylindrical type, a pleated type and the like can be appropriately employed.

Although there is no restriction | limiting in particular as a desalination rate (sodium chloride exclusion rate) of a reverse osmosis membrane, It is preferable to use a thing with a selectivity of 95% or more in general. Moreover, if it is a nano filter membrane, it is preferable to use the selectivity whose desalting rate is about 40% or more.
Moreover, the liquid component (concentrated water) that has not passed through the membrane by the membrane concentration treatment using the reverse osmosis membrane or the nanofilter membrane may be returned to the untreated water containing the hardly decomposable substance.

(B) Adsorption treatment step A step of adding an adsorbent to the water containing the hardly decomposable substance (treated raw water) or the water in which the hardly decomposable substance is concentrated in the step (A) and causing the adsorbent to adsorb the hardly decomposable substance. It is. Even if the water hardly concentrated or the water concentrated by the above membrane concentration treatment is directly subjected to the membrane filtration treatment step (C), the molecular weight of the filtration membrane is large relative to the size of the hardly degradable material such as dioxin. , Refractory substances cannot be concentrated. Therefore, after adding an adsorbent and adsorbing the fine hardly decomposable substance to the large adsorbent particles, the hardly decomposable substance is concentrated by performing (C) membrane filtration treatment.

Adsorbents used in the method of the present invention include inorganic porous materials and organic porous materials, specifically, inorganic porous materials such as zeolite, diatomaceous earth, acidic clay, activated clay, carbon black, and metals such as titanium dioxide. Examples thereof include inorganic adsorbents such as oxides and metal powders, and organic porous bodies such as activated carbon and ion exchange resins. These may be used individually by 1 type, and may be used in combination of 2 or more types. As the adsorbent, an inorganic adsorbent is preferable, and titanium dioxide having a high adsorption efficiency is particularly preferable.
Moreover, when providing the photolysis process of (F-1) and (F-2) mentioned later, it is preferable to use the adsorbent which can function as a photocatalyst, and as such an adsorbent, for example, titanium dioxide is used. Can be mentioned.

The amount of adsorbent added may be appropriately determined in consideration of the type of adsorbent, the adsorption performance, the type and amount of contaminants to be treated, the treatment time and cost, etc., but in general, it may be 1 to 1000 ppm, It is preferable to set it as 10-100 ppm.
When titanium dioxide is used as the adsorbent, the amount of the hardly decomposable substance adsorbed increases as the amount added increases, but the cost increases. Therefore, the addition amount of titanium dioxide should be appropriately selected in consideration of cost and the like, and is usually preferably in the range of 1 to 100,000 ppm, and preferably in the range of 10 to 1,000 ppm. More preferred.
In order to increase the adsorption efficiency and the decomposition efficiency, it is preferable to use an adsorbent having a large specific surface area. For example, in the case of titanium dioxide, an X-ray particle size of about 7 nm is preferable.

  Further, the longer the contact time of the adsorbent with the hardly decomposable substance-containing water, the better the adsorption efficiency, but it may be determined appropriately in consideration of the size of the treatment tank, for example, 1-2 hours. It is preferable to set the degree.

(F) Photolysis step This is a step of decomposing the hardly decomposable substance by irradiating the hardly decomposable substance-containing water or the water containing the adsorbent adsorbing the hardly decomposable substance with ultraviolet rays. That is, the hardly decomposable substance in water that is not adsorbed by the adsorbent and a part of the hardly decomposable substance adsorbed by the adsorbent are decomposed. By providing this process, the hardly decomposable substance contained in the treated discharged water can be reduced to a lower concentration.
Further, in this step, when the adsorbent used in the present invention is titanium dioxide, the hardly decomposable substance in water is more efficiently photodegraded by light irradiation (preferably 250 to 380 nm). The longer the photolysis is performed, the higher the decomposition efficiency. For example, when 20 ppm of titanium dioxide is added and irradiated with ultraviolet rays (254 nm) for 30 minutes, the decomposition efficiency of dioxins of about 60 to 70% is obtained.

(C) Membrane filtration process The permeated water containing salt but not containing the hardly decomposable substance is separated using a filtration membrane that does not allow the adsorbent that has adsorbed the hardly decomposable substance to pass through, but allows the salt to pass through. This is a step of obtaining water in which the adsorbent adsorbing the hardly decomposable substance is concentrated. By this step, the salt can be removed.

  The type of membrane used in the membrane filtration treatment is not particularly limited as long as it has the above-mentioned separation performance, but in terms of good separation performance, simplicity, etc., for example, an ultrafiltration membrane (UF membrane) It is preferable to use a nanofilter membrane (NF membrane), a microfiltration membrane (MF membrane), a reverse osmosis membrane (RO membrane) or the like.

  Among these, the use of an ultrafiltration membrane (hereinafter sometimes referred to as a UF membrane) sufficiently removes fine adsorbents adsorbing dioxins and the like and fine particles such as dioxins insoluble in water. In addition, the operability and economy are good.

Examples of the constituent material of the ultrafiltration membrane (UF membrane) include cellulose acetate-based, polyacrylonitrile-based, polysulfine-based, and polyethersulfone-based resin materials.
In addition, as the membrane module, a flat membrane type, a hollow fiber type, a spiral type, a cylindrical type, a pleated type and the like can be appropriately employed.
The molecular weight cutoff of the ultrafiltration membrane is not particularly limited, but a molecular weight of about 3000 to 150,000 may be used.

Examples of the constituent material of the microfiltration membrane (MF membrane) include cellulose ester-based, polyacrylonitrile-based, polysulfine-based, and polyethersulfone-based resin materials. Further, as the format, a flat membrane, a filter cartridge, a disposal cartridge, etc. may be selected as required.
The size of the pores (pores) of the microfiltration membrane may be appropriately determined depending on, for example, the particle size of the adsorbent used in the adsorption process, but may be about 0.01 to 1 μm.

  The reverse osmosis membrane (RO membrane) and the nanofilter membrane (NF membrane) are as described in the above (A) membrane concentration treatment step.

(G) Backwashing step In the above step (C), when an ultrafiltration membrane is used, an adsorbent that adsorbs a hardly decomposable substance (especially when titanium dioxide is used as the adsorbent) is ultrafiltered. It causes clogging of the film. Therefore, it is preferable to perform regular backwashing in order to prevent a decrease in the filtration capacity of the filtration membrane. What is necessary is just to select the frequency of backwashing suitably, For example, about 1 to 10 minutes is preferable once for 30 to 120 minutes. Moreover, in performing this backwashing, it is preferable to use clear water that does not contain solid matter. It is economical if the permeated water obtained in the (A) membrane concentration treatment step or the permeated water obtained in the (C) membrane filtration treatment step is used as water for backwashing (backwash water). Particularly preferred is the permeated water obtained in the (A) membrane concentration treatment step.

  And for this backwash water, it is preferable to add a disinfectant such as sodium hypochlorite for sterilization, and the amount of such sodium hypochlorite added is the residual chlorine concentration after backwash May be added so as to be in the range of 1 to 100 mg / L.

  In addition, in order to improve the decomposition efficiency of the hardly decomposable substance in the latter stage, the water to be transferred to the (D) chemical decomposition step described later is only the backwash waste water from which the adsorbent that has adsorbed the hardly decomposable substance is washed out. Preferably, or if necessary, (A) the hardly decomposable substance concentrated water obtained in the membrane concentration treatment step may be transferred to the (D) chemical decomposition step.

(H) Aggregation and separation step The flocculant is added to the water in which the adsorbent adsorbing the hardly decomposable substance obtained in the step (C) is concentrated, and the adsorbent adsorbing the hardly decomposable substance is further aggregated. -It is a process of obtaining a sediment containing a hardly decomposable substance by sedimentation.
In addition, the supernatant liquid obtained by separating the sediment in this step can be returned to any step in the treatment method of the present invention. Further, if the concentration of the hardly decomposable substance is below the emission standard value, it may be discharged.

  This step is performed in order to shorten the time since the adsorbent that adsorbs the hardly decomposable substance is fine and requires time for solid-liquid separation, and to improve the decomposition efficiency in the subsequent (D) chemical decomposition step. .

  As the flocculant, either an inorganic flocculant or an organic flocculant can be used alone or in combination. Examples of inorganic flocculants include aluminum sulfate, ferric chloride, ferrous sulfate, polyaluminum chloride, and zeolite.

  Examples of the organic flocculants include various anionic polymer flocculants such as sodium polyacrylate, a copolymer of sodium acrylate and acrylamide, and cationic polymer flocculants.

  The flocculant is not particularly limited as long as it does not adversely affect the (D) chemical decomposition step, but a small amount of an inorganic substance capable of obtaining an aggregate having a high bulk density is preferred.

  The addition amount of the flocculant may be appropriately determined in consideration of the kind of the flocculant, the adsorption performance, the cost, etc., as in the case of the adsorbent, but generally may be 1 to 10,000 ppm, and 10 to 1,000 ppm. It is preferable that

(D) Chemical decomposition step The peroxide is brought into contact with the adsorbent obtained by adsorbing the separated hardly decomposable substance obtained in the step (C), or the precipitate obtained in the step (H), and hardly decomposed. This is a step of oxidatively decomposing a sexual substance. When chemical decomposition is performed, the peroxide is brought into contact with the hardly decomposable substance without desorbing the hardly decomposable substance adsorbed on the adsorbent.

Examples of peroxides used in this process include permanganate, persulfate, sodium peroxide, barium peroxide, zinc peroxide, cadmium peroxide, potassium peroxide, calcium peroxide, and chromium peroxide. Examples include metal salt, hydrogen peroxide, ozone, and a combined system of a metal catalyst and a hydrogen supplier.
Among these, peroxides used as preferred oxidizing agents are permanganate and persulfate.

  Permanganates include zinc permanganate, cadmium permanganate, potassium permanganate, calcium permanganate, silver permanganate, strontium permanganate, cesium permanganate, sodium permanganate, permanganate Examples include barium, magnesium permanganate, lithium permanganate, and rubidium permanganate.

Examples of the persulfate include ammonium persulfate, sodium persulfate, potassium persulfate, potassium hydrogen persulfate, lead persulfate, and rubidium persulfate. Examples of the oxidizing agent include ammonium persulfate, sodium persulfate, and Persulfates such as potassium persulfate are particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more types. The amount used is preferably 100 times mole or more, more preferably 10 ⁴ to 10 ¹² times mole, and still more preferably 10 times, based on the number of moles of the hardly decomposable substance adsorbed on the adsorbent. It is selected in the range of ⁷ to ¹⁰ times mol. If the amount of peroxide used is at least 100 times the mol of the hardly decomposable substance, even if the concentration of the hardly decomposable substance in the hardly decomposable substance-containing water fluctuates, it is difficult to adsorb to the adsorbent. The degradable substance can be chemically decomposed stably up to the emission standard value of industrial waste (3,000 pg-TEQ / g) or less.

  Specifically, the amount of peroxide added may be appropriately determined according to the type and concentration of the persistent organic compound in the persistent material-containing material and the type and concentration of the coexisting material. When the active substance-containing material is in the form of a solution, the content is preferably 100 to 100,000 ppm, particularly preferably 1000 to 50,000 ppm. On the other hand, when the hardly decomposable substance-containing material is a solid, it is preferably 0.01 to 100% by mass, and preferably 0.1 to 20% by mass with respect to the hardly decomposable substance containing material. Particularly preferred.

The amount of peroxide added depends on the pH of the water to be treated, but when only the reaction is promoted, it may be added in consideration of the oxidizing power of persulfuric acid.
In order to promote decomposition by peroxide, the peroxide is preferably brought into contact in a dissolved state in water, and another oxidizing agent such as hydrogen peroxide or ozone may coexist.

  Furthermore, in order to carry out this decomposition reaction more effectively, an appropriate amount of an organic solvent can be added to this reaction system. As such an organic solvent, hydrocarbons having 2 to 12 carbon atoms, for example, n-hexane, toluene, xylene, methylphthalene and the like are preferably used.

  Persulfate is decomposed by heating to generate bisulfate ion radicals, sulfate ion radicals and hydroxy radicals, and these radicals decompose difficult-to-decompose substances such as dioxins, but these radicals emit electrons in a short time. Therefore, in order to increase the decomposition efficiency, it is preferable to stir the adsorbent that has adsorbed the hardly decomposable substance in a slurry state. The more vigorous stirring is, the higher the probability that the radicals and the hardly decomposable substance will come into contact with each other. However, there is a limit to the stirring, and there is no economically disadvantageous range depending on the capacity of the decomposition vessel and the viscosity of the slurry. It is preferable to carry out vigorously.

  The reaction temperature at which the hardly decomposable substance adsorbed on the adsorbent is chemically decomposed with peroxide is preferably from room temperature to 100 ° C. More preferably, it is 40 to 100 degreeC. If it is less than 40 ° C., it may take a long time to decompose.

  The higher the chemical decomposition treatment temperature, the higher the decomposition rate, but a pressure vessel is required to perform decomposition at a temperature higher than the boiling temperature of water (higher than 100 ° C when the salt concentration increases), so atmospheric pressure below the boiling temperature. It is preferable to perform the decomposition treatment below. In addition, when the decomposition treatment is performed at atmospheric pressure above the boiling temperature, the difficulty of decomposing substances such as dioxin evaporates as the temperature rises as the water evaporates. It is necessary to provide it.

  In the present invention, when heating, the heating method is not particularly limited, and any of an electric heating method, a heating water supply method, a steam suction method, a boiler method, etc. can be used. Care must be taken not to increase the amount of water. If the water content is too high, the persulfate concentration for the reaction will decrease. The chemical decomposition treatment time depends on the treatment temperature and other conditions, and cannot be generally defined, but is usually about 10 minutes to 500 hours.

  The adsorbent that had adsorbed the hardly decomposable substance that had undergone chemical decomposition was confirmed to have an emission standard value (3,000 pg-TEQ / g) or less after the chemical decomposition. It can be disposed of in the same way as normal industrial waste.

  In addition, the adsorbent once used for adsorption of the hardly decomposable substance can be used repeatedly until it degrades the performance as an adsorbent without immediately discarding it, and the wastewater is treated as an on-site, closed system. Is possible, extremely safe and economical. Even when the adsorbent of the hardly decomposable substance is finally discarded, the remaining amount of the hardly decomposable substance can be sufficiently reduced and disposed of, so that the natural environment is not adversely affected. .

In order to further reduce the waste, after the chemical decomposition in the step (D) is completed, the decomposition product can be left still for solid-liquid separation. The supernatant obtained by solid-liquid separation of the decomposition product can be returned to any step in the treatment method of the present invention. Further, if the concentration of the hardly decomposable substance is below the emission standard value, it may be discharged.
On the other hand, the sediment can be disposed as industrial waste after confirming that it is 3,000 ppm-TEQ / g or less.

Next, the treatment apparatus for water containing a hardly decomposable substance of the present invention (hereinafter referred to as the apparatus of the present invention)
Adsorbent addition part for adding adsorbent to water containing persistent substances,
A membrane filtration processing unit for separating the adsorbent adsorbing the hardly decomposable substance using a filtration membrane and concentrating the adsorbent adsorbing the hardly decomposable substance;
A chemical decomposition unit is provided for adding a peroxide to the adsorbent adsorbing the hardly decomposable substance to oxidatively decompose the hardly decomposable substance.

  One or more of each of the above parts may be provided. A mode in which two or more of the above-described parts are provided is shown in FIGS.

Particularly preferred embodiments of the device according to the invention are:
A reductive substance input section for introducing a reducible substance that neutralizes chlorine in the water into the hardly decomposable substance-containing water,
A membrane concentration treatment unit for concentrating a hardly decomposable substance from water containing a hardly decomposable substance using a reverse osmosis membrane (RO membrane) or a nanofilter membrane (NF membrane);
An adsorbent addition unit for adding an adsorbent to the water in which the hardly decomposable substance is concentrated and adsorbing the hardly decomposable substance to the adsorbent;
A membrane filtration processing unit for separating the adsorbent adsorbing the hardly decomposable substance using a filtration membrane and concentrating the adsorbent adsorbing the hardly decomposable substance;
A flocculant addition unit for adding an aggregating agent to water in which the adsorbent adsorbing the hardly decomposable substance is concentrated, and aggregating the adsorbent adsorbing the hardly decomposable substance;
A solid-liquid separation unit for allowing the adsorbent adsorbing the hardly decomposable substance agglomerated by the flocculant to separate the precipitate and the supernatant into solid and liquid, and adding a peroxide to the sediment A chemical decomposition unit is provided for oxidative decomposition of a hardly decomposable substance in the product.

Hereinafter, an example of a preferred embodiment of the apparatus of the present invention will be described with reference to FIG.
FIG. 3 is a schematic view of the treatment apparatus 1 for carrying out one aspect of the method for treating hardly decomposable substance-containing water of the present invention. The processing apparatus 1 shown in FIG. 3 includes a reducing substance input unit 10, a membrane concentration processing unit 20, an adsorbent addition unit 30, a membrane filtration processing unit 40, a flocculant addition unit 60, a solid-liquid separation unit 70, and a chemical decomposition process. The unit 80 is a basic configuration. FIG. 3 further shows an ultraviolet irradiation unit 50 provided as necessary.

[Reducing substance input unit 10]
Water containing a hardly decomposable substance such as dioxins is first put into the charging tank 11. Free chlorine in the raw water is neutralized by adding sodium bisulfite from the reducing substance supply unit 12 to the charging tank 11 via a pump (not shown). Further, the raw water and sodium bisulfite are mixed in the charging tank 11 by a stirring means, and the residual chlorine concentration of the raw water is measured by a chlorine concentration meter (not shown).

[Membrane concentration processing unit 20]
The hardly decomposable substance-containing water neutralized with sodium bisulfite can remove suspended substances and the like by passing through the prefilter 21. And the water which passed the pre filter 21 is sent to the reverse osmosis membrane 22 via the pump which is not shown in figure, and a membrane process is carried out by the said reverse osmosis membrane 22 concerned. And it will be divided into the permeated water which passed the said reverse osmosis membrane 22, and the liquid part (concentrate) which did not pass the film | membrane.
Among these, the permeated water that has passed through the reverse osmosis membrane 22 can be discharged to the outside if the content of the hardly decomposable substance is equal to or less than the discharge standard value (10 pg-TEQ / L). Moreover, it can store in the backwash water tank 42 of the membrane filtration process part 40 mentioned later, and can be used as backwash water for backwashing the ultrafiltration membrane 41. FIG.

Further, as shown in FIG. 3, the liquid (concentrate) that has not passed through the reverse osmosis membrane 22 is mixed with the hardly-decomposable substance-containing water after passing through the prefilter 21, and again. Reverse osmosis membrane treatment is performed.
In this way, the concentrate is retransmitted several times, but the concentrate that has not passed through the reverse osmosis membrane 22 due to this is sent to the treatment tank 31 disposed in the adsorbent addition / ultraviolet irradiation unit 30. It will follow.

[Adsorbent addition part 30]
In the adsorbent addition unit 30, the adsorbent sent from the adsorbent supply unit 32 via a feeder (not shown) is added to the liquid (concentrate) sent to the processing tank 31. In the processing tank 31, the liquid component of the concentrate and the adsorbent are mixed by the stirring means, so that the hardly decomposable substance remaining in the liquid component is efficiently adsorbed by the added adsorbent. become.

  When titanium dioxide is used as the adsorbent, the hardly decomposable substance in the liquid can be adsorbed on the adsorbent, and at the same time, the UV lamp 33 can be irradiated with ultraviolet rays to photodegrade the hardly decomposable substance. . At this time, titanium dioxide as an adsorbent functions as a photocatalyst and promotes photolysis of the hardly decomposable substance.

[Membrane filtration processing unit 40]
The liquid component (concentrate) to which the adsorbent has been added is subjected to membrane filtration processing by the ultrafiltration membrane 41 through a pump (not shown) in the membrane filtration processing unit 40. In addition, when performing membrane filtration with the ultrafiltration membrane 41, if the filtration membrane 41 is backwashed, it is possible to prevent a reduction in filtration capacity, while performing such backwashing. As shown in FIG. 3, the permeated water that has passed through the reverse osmosis membrane 22 in the membrane concentration treatment unit 20 may be used as water for backwashing (backwashing water).
And with respect to this backwash water, you may add sodium hypochlorite from the disinfectant supply part 43 via the pump which is not illustrated from the backwash water tank 42. FIG.

  By the membrane filtration treatment by the ultrafiltration membrane 41, the liquid content of the hardly decomposable substance-containing water to which the adsorbent has been added is divided into permeated water and concentrate (backwash solution). Among these, permeated water can be discharged to the outside as discharged water if the content of the hardly decomposable substance is equal to or less than the discharge standard value (10 pg-TEQ / L).

[Ultraviolet irradiation unit 50]
In the ultraviolet irradiation unit 50, the concentrate (backwash solution) that has not passed through the ultrafiltration membrane 41 in the membrane filtration processing unit 40 is sent to the decomposition tank 51, and is irradiated with ultraviolet rays by the ultraviolet lamp 53 while being stirred by the stirring means. Thus, the hardly decomposable substance may be decomposed. In the ultraviolet irradiation unit 50, hydrogen peroxide solution may be added from the promoter supply unit 52 via a pump (not shown) in order to promote photolysis by ultraviolet rays.
In the present invention, in order to perform photolysis, it is necessary that the adsorbent added in the adsorbent addition section 30 is titanium dioxide that functions as a photocatalyst. By using titanium dioxide, a photolytic process with high resolution is performed.

[Flocculant addition part 60]
In the flocculant addition part 60, with respect to the concentrate (backwash water) containing the hardly decomposable substance which was sent to the coagulation tank 61 and concentrated by the ultrafiltration membrane and subjected to the photolysis treatment as necessary. The flocculant sent from the flocculant supply unit 62 via a feeder (not shown) is added. In the coagulation tank 61, the liquid of the concentrate (backwash water) and the coagulant are mixed by the stirring means, so that the hardly decomposable substance adsorbed by the adsorbent remains in the liquid. , The added flocculant is efficiently agglomerated and easily settled.

[Solid-liquid separation unit 70]
In the solid-liquid separation unit 70, the hardly decomposable substance aggregated by the coagulant in the coagulant adding unit 60 is settled in the precipitation tank 71, and is solid-liquid separated into a supernatant and a sediment (slurry).
Stirring means (not shown) is provided so that the sediment does not harden at the bottom of the sedimentation tank 71, and stirring is performed at a gentle rotational speed of about 1 rpm.
The clear supernatant can be returned to the processing tank 31 of the adsorbent addition unit 30 or discharged if it is less than or equal to the discharge reference value (10 pg-TEQ / L).

[Chemical decomposition unit 80]
In the chemical decomposition unit 80, a peroxide is added from the oxidant supply unit 82 to the sediment (slurry) extracted from the bottom extraction port of the settling tank 71 of the solid-liquid separation unit 70 sent to the decomposition tank 81. The material is stirred by a stirring means to chemically decompose the hardly decomposable substance in the sediment (slurry).

  After completion of the chemical decomposition, the clear supernatant can be returned to the treatment tank 31 of the adsorbent addition unit 30 or discharged if it is less than the discharge reference value (10 pg-TEQ / L).

  On the other hand, the solid content (discharged solid) can be disposed as industrial waste after confirming that the emission standard of industrial waste is satisfied, or can be reused as an adsorbent.

  As described above, the permeated water generated in the above (A) reverse osmosis membrane treatment step and (C) membrane filtration step can be used as backwash water or returned to (B) adsorption treatment step, etc. If it is below a standard value (10pg-TEQ / L), it can be discharged outside as discharged water. The discharge to the outside usually means discharge into a river or the like.

  By the way, when the concentration of refractory substances in raw water fluctuates, the outlet concentration of effluent after wastewater treatment also fluctuates in conjunction with this, and contains refractory substances at concentrations exceeding the discharge standard value. The discharged water may be discharged. However, it takes about one month for the official method and about two weeks for the simplified method to measure the concentration of persistent substances such as dioxins in the discharged water. Impossible.

Therefore, in the present invention, even when the concentration of the hardly decomposable substance in the raw water fluctuates, in order to stably keep the concentration of the hardly decomposable substance in the discharged water below the discharge standard value, (C) It is preferable to perform a membrane filtration treatment step. Moreover, after adding an adsorbent with respect to permeated water, it is preferable to perform a (C) membrane filtration process process further.
According to the experiments by the present inventors, not only the emission standard value (10 pg-TEQ / L) is stably reduced below the environmental standard value (1 pg-TEQ / L) by two or more membrane filtration treatments. It was also confirmed that Table 1 below shows the change in the concentration of dioxin in the permeated water and the removal rate (%) of dioxin when the membrane filtration treatment is performed twice.

  An embodiment of a contaminated water treatment system including a plurality of (C) membrane filtration treatment steps is shown in FIGS.

  For example, in the embodiment of FIG. 4 (a), an adsorbent is added to the hardly decomposable substance-containing water (raw water) ((B-1) adsorption treatment step) and separated into a concentrate and permeate by membrane filtration. ((C-1) membrane filtration treatment step). About a concentrate, it processes in the above-mentioned (D) chemical decomposition process. After the adsorbent was further added to the permeated water ((B-2) adsorption treatment step), membrane filtration ((C-2) membrane filtration treatment step) was performed again, and the concentrate that did not permeate the filtration membrane was used. (B-1) Since it is returned to the adsorption treatment step and the permeated water is below the discharge standard value, it can be discharged to the outside as discharged water.

  In the embodiment of FIG. 4 (b), (B) the adsorption treatment step is provided once and (C) the membrane filtration treatment step is provided twice, which is a more economical system.

In FIG. 5, the water containing the hardly decomposable substance is subjected to membrane concentration treatment (A) before adsorbent addition. The filtration membrane used here is preferably a reverse osmosis membrane or a nanofilter membrane.
The concentrated liquid in the first stage membrane concentration treatment (A) is subjected to membrane filtration treatment (C) after adding an adsorbent (B) to obtain permeated water and a concentrated liquid. The concentrate is sent to the chemical decomposition step (D).
The permeated water of the first stage membrane concentration treatment (A) becomes drained water after further adsorbing agent (B-2) and membrane filtration treatment (C-2) in FIG. 5 (c). The concentrated solution of this membrane filtration treatment (C-2) is subjected to membrane filtration treatment (C) after adding an adsorbent (B) in the same manner as the concentrated solution of the first stage membrane concentration treatment (A).
The permeated water of the membrane filtration treatment (C-2) is discharged water after further adsorbing agent (B-3) and membrane filtration treatment (C-3). The concentrated solution of the membrane filtration treatment (C-3) is subjected to membrane filtration treatment (C) after adding an adsorbent (B) in the same manner as the concentrated solution of the first stage membrane concentration treatment (A).

  In the embodiment of FIG. 5D, (A) the membrane concentration treatment step is provided once, (B) the adsorption treatment step is performed once, and (C) the membrane filtration treatment step is provided three times. The (B) adsorption treatment process of the embodiment of () is a more economical system than three times.

  In the embodiment of FIG. 5 (e), (A) membrane concentration treatment step is provided once, (B) adsorption treatment step is once, and (C) membrane filtration step is provided twice. The (C) membrane filtration treatment step of the embodiment is a more economical system than three times.

  According to the method and apparatus of the present invention, as shown in FIGS. 3 to 5 above, by providing the membrane concentration treatment step and the membrane filtration treatment step a plurality of times, it is difficult to decompose dioxins and the like in the discharged water. The substance concentration can be reduced more stably to below the emission standard value.

  Furthermore, according to the method and apparatus of the present invention, the concentration of the hardly decomposable substance is stabilized more stably than before by treating the hardly decomposable substance contained in the contaminated water with a combination of concentration, photolysis and chemical decomposition. Can be reduced.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Reference Example 1 (See Fig. 6)
(B) Adsorption treatment process Raw water (dioxin concentration 6500 pg-TEQ / L) was placed in an adsorption tank having a residence time of 1 hour, and 1000 ppm of diatomaceous earth was added as an adsorbent and adsorbed with stirring.

(C) Membrane filtration treatment step The water to which the adsorbent was added was subjected to membrane filtration treatment with an ultrafiltration membrane (hollow fiber type, molecular weight cut off 150,000), and the liquid that did not pass through the ultrafiltration membrane A part of the solution was added (returned) to the raw water to which the adsorbent was added, and completely filtered at an operating pressure of 0.3 MPa. The permeated water at this time was 2.5 pg-TEQ / L, which was below the discharge standard value (10 pg-TEQ / L). Washing water was backwashed for 1 minute with a permeated water amount 4 times the ultrafiltration membrane permeated water amount, and this backwashed solution was used as a concentrate (slurry).

(D) Chemical decomposition process Sodium persulfate was added to the concentrate obtained at the said process (C) so that it might become a density | concentration of 10 mass%, and it was made to react at 70 degreeC for 7 hours. The dioxin concentration of the solid in the decomposition product after the reaction was 1,000 pg-TEQ / g, which was less than the emission standard value (3,000 pg-TEQ / g).

Reference Example 2 (See Fig. 7)
(A) Membrane concentration treatment step Raw water (dioxin concentration 6,500 pg-TEQ / L) was filtered through a reverse osmosis membrane (spiral type, sodium chloride rejection 95%). A part of the liquid (concentrated water) that did not pass through the reverse osmosis membrane was added (returned) to the raw water and filtered at an operating pressure of 1 MPa or more. 2/3 of the amount treated was permeated water. The dioxin concentration of the permeated water at this time was 1 pg-TEQ / L, which was less than the emission standard value (10 pg-TEQ / L).

(B) Adsorption treatment step As in Reference Example 1 , 1/3 of the treated water obtained in the above step (A) is placed in an adsorption tank having a residence time of 1 hour, and activated clay 2, as an adsorbent. 000 ppm was added and adsorbed with stirring.

(C) Membrane filtration treatment step The concentrated water to which the adsorbent was added was subjected to membrane filtration treatment with an ultrafiltration membrane (hollow fiber type, 10,000 fraction). A part of the liquid (concentrate) that did not pass through the ultrafiltration membrane was added (returned) to the concentrated water to which the adsorbent obtained in the above step (B) was added, and the operating pressure was 0.3 MPa. Filtered through. The dioxin concentration of the permeated water that passed through the ultrafiltration membrane was 1.8 pg-TEQ / L, which was less than the discharge standard value (10 pg-TEQ / L). A part of the concentrate obtained in the step (C) may be returned to the adsorption tank in the step (B).
The reverse osmosis membrane permeated water obtained in the step (A) and the ultrafiltration membrane permeated water obtained in the step (C) were combined to form discharged water (dioxin concentration: 1.3 pg-TEQ / L).
(G) Backwashing process Permeation of the solid content (concentrate) adhering to the ultrafiltration membrane in the above step (C) is 4 times the amount of permeated water of the ultrafiltration membrane using the permeated water of the membrane concentration treatment process. The solution was backwashed with water for 1 minute, and this backwash solution was used as a concentrate.

(D) Chemical decomposition process Sodium persulfate was added to the concentrate obtained at the said process (G) so that it might become a density | concentration of 10 mass%, and it was made to react at 70 degreeC similarly to the reference example 1 for 7 hours. The dioxin concentration of the solid in the decomposition product after the reaction was 950 pg-TEQ / g, which was below the emission standard value (3,000 pg-TEQ / g).

Reference Example 3 (See Fig. 8)
(E) Chlorine neutralization step and (A) membrane concentration treatment step For raw water (dioxin concentration 6,500 pg-TEQ / L, free chlorine concentration 50 mg / L), sodium bisulfite is 3 times the amount of free chlorine It added and stirred so that it might be 150 mg / L. This was filtered through a reverse osmosis membrane (spiral type, sodium chloride rejection of 95%). A part of the liquid (concentrated water) that did not pass through the reverse osmosis membrane was added (returned) to the raw water to which sodium bisulfite was added, and filtered at an operating pressure of 1 MPa or more. 2/3 of the treated amount was permeated water. The dioxin concentration of the permeated water at this time was 1.1 pg-TEQ / L, which was less than the emission standard value (10 pg-TEQ / L).

(B) Adsorption treatment step As in Reference Example 1 , 1/3 of the treated water obtained in the above step (A) is placed in an adsorption tank having a residence time of 1 hour, and 2 activated clay is used as an adsorbent. 1,000 ppm was added and adsorbed with stirring.

(C) Membrane filtration treatment step The concentrated water to which the adsorbent was added was ultrafiltered with an ultrafiltration membrane (hollow fiber type, 10,000 fraction). A part of the liquid (concentrate) that did not pass through the ultrafiltration membrane was added (returned) to the concentrated water to which the adsorbent was added, and filtered at an operating pressure of 0.1 MPa. The dioxin concentration of the permeated water that passed through the ultrafiltration membrane was 1.7 pg-TEQ / L, which was less than the emission standard value (10 pg-TEQ / L).
The reverse osmosis membrane permeated water obtained in the step (A) and the ultrafiltration membrane permeated water obtained in the step (C) were combined to form discharged water (dioxin concentration: 1.3 pg-TEQ / L).

(G) Backwashing process Using the permeated water of the membrane concentration treatment process, the permeated water amount of the solid content (concentrate) adhering to the ultrafiltration membrane in the above step (C) is four times the ultrafiltration permeated water amount. For 1 minute, and this backwash solution was used as a concentrate.

(D) Chemical decomposition process Sodium persulfate was added to the concentrate obtained at the said process (G) so that it might become a density | concentration of 10 mass%, and it was made to react at 70 degreeC similarly to the reference example 1 for 7 hours. The solid dioxin concentration in the decomposed product after the reaction was 970 pg-TEQ / g, which was less than the emission standard value (3,000 pg-TEQ / g).
From the above, it was confirmed that the treatment of neutralizing free chlorine, which causes deterioration of the membrane, with sodium bisulfite does not affect the chemical decomposition reaction.

Reference example 4 (see FIG. 9)
(E) Chlorine neutralization step and (A) Membrane concentration treatment step With respect to raw water (dioxin concentration 6,500 pg-TEQ / L, free chlorine concentration 50 mg / L), sodium bisulfite is three times the amount of free chlorine. It added and stirred so that it might be 150 mg / L. A part of the liquid (concentrated water) that did not pass through the reverse osmosis membrane with a reverse osmosis membrane (spiral type, sodium chloride rejection rate 95%) was added (returned) to the raw water to which sodium bisulfite was added. Filtration was performed at an operating pressure of 5 MPa or more. 2/3 of the treated amount was permeated water. The dioxin concentration of the permeated water at this time was 1.1 pg-TEQ / L, which was less than the discharge standard value (10 pg-TEQ / L). The dioxin concentration of the concentrated water which became 1/3 of the treatment amount was 20,000 pg-TEQ / L.

(B) Adsorption treatment step and (F) photolysis step The concentrated water obtained in the above step (A) is placed in an adsorption tank with a residence time of 1 hour, and 15 ppm of titanium dioxide is added as an adsorbent and adsorbed with stirring. Ultraviolet rays (wavelength 254 nm) were irradiated. The dioxin concentration of the concentrated water after the photolysis treatment was 6,000 pg-TEQ / L.

(C) Membrane filtration treatment step The concentrated water after the adsorbent was added and irradiated with ultraviolet rays was subjected to membrane filtration treatment with an ultrafiltration membrane (hollow fiber type, 10,000 fraction). A part of the liquid (concentrate) that did not pass through the ultrafiltration membrane was added (returned) to the concentrated water after the adsorbent was added and subjected to the photolysis treatment, and the operation was performed at 0.3 MPa. Filtered under pressure. The dioxin concentration of the permeated water that passed through the ultrafiltration membrane was 1.2 pg-TEQ / L, which was less than the discharge standard value (10 pg-TEQ / L).

(G) Backwashing process Using the permeated water of the membrane concentration treatment process, the permeated water amount of the solid content (concentrate) adhering to the ultrafiltration membrane in the above step (C) is four times the ultrafiltration permeated water amount. And backwashed for 1 minute, and this backwash liquid was used as a concentrate (slurry).
(D) Chemical decomposition process Sodium persulfate was added to the concentrate obtained at the said process (G) so that it might become a density | concentration of 10 mass%, and it was made to react at 70 degreeC similarly to the reference example 1 for 7 hours. The dioxin concentration of the solid in the decomposition product after the reaction was 900 pg-TEQ / g, which was less than the emission standard value (3,000 pg-TEQ / g).
From the above, it was found that the concentrate can be decomposed by adding titanium dioxide to the concentrate that did not pass through the reverse osmosis membrane and irradiating with ultraviolet rays.

Reference example 5 (see FIG. 10)
Until the step (G), the treatment was carried out in the same manner as in Reference Example 4, and then the following steps were carried out.
(F-2) Second photolysis step The concentrate (backwash water: dioxin concentration 15,000 pg-TEQ / L) obtained in the above step (G) was subjected to ultraviolet irradiation (wavelength 254 nm) for 24 hours. As a result, the dioxin concentration after the ultraviolet irradiation was 750 pg-TEQ / L.

(D) Chemical decomposition step Sodium persulfate was added to the concentrate (slurry) obtained in the step (G) so as to have a concentration of 10% by mass, and the reaction was carried out at 70 ° C. for 7 hours as in Reference Example 1. I let you. The dioxin concentration of the solid in the decomposition product after the reaction was 850 pg-TEQ / g, which was less than the emission standard value (3,000 pg-TEQ / g).
Thereby, it turned out that the said concentrate can be decomposed | disassembled by performing ultraviolet irradiation with respect to the concentrate which did not pass an ultrafiltration membrane.

Reference example 6 (see FIG. 11)
(H) Aggregation separation process
To the concentrate (slurry) obtained in the step (G) of Reference Example 5 , 1,000 ppm of polyaluminum chloride as an inorganic flocculant was added and stirred. After 12 hours, the sediment was withdrawn as a 10% strength by weight slurry concentrate.

(D) Chemical decomposition process Sodium persulfate was added to the slurry concentrate obtained at the said process (H) so that it might become 20 mass%, and it was made to react at 90 degreeC for 24 hours. The dioxin concentration after the reaction was 550 pg-TEQ / g, which was less than the emission standard value (3,000 pg-TEQ / g).

Example 7 (example of multiple filtration) (see FIG. 12)
The (B) adsorption treatment step, (C) membrane filtration treatment step, and (D) chemical decomposition step are carried out in the same manner as in Reference Example 1, and the permeated water obtained in step (C) is further treated as follows. did.
(C-2) Second membrane filtration process
The permeated water obtained in the (C) membrane filtration treatment step from the raw water of Reference Example 1 (dioxin concentration 6,500 pg-TEQ / L) is put into an adsorption tank with a residence time of 1 hour, and 100 ppm of diatomaceous earth is added as an adsorbent. Adsorbed with stirring. The permeated water to which this adsorbent was added was subjected to membrane filtration ( (C-2) membrane filtration treatment step) with an ultrafiltration membrane (hollow fiber type, molecular weight cut off 150,000). A part of the liquid (concentrate) that did not pass through the ultrafiltration membrane permeates through the ultrafiltration membrane of step (C) and is added (returned) to the permeated water to which the adsorbent is added. Filtration at an operating pressure of 2 MPa. The dioxin concentration of the permeated water at this time was 1 pg-TEQ / L or less, which was less than the environmental standard value (1 pg-TEQ / L).

The concentrate of the ultrafiltration membrane obtained in the step (C-2) was also returned to the adsorption tank before the (C) membrane filtration treatment step of Reference Example 1 , but the treated water (discharged water) and the chemical decomposition product There was no change in the dioxin concentration.

Example 8 (example of multiple filtration) (see FIG. 13)
The (B) adsorption treatment step, (C) membrane filtration treatment step, and (D) chemical decomposition step are carried out in the same manner as in Reference Example 1, and the permeated water obtained in step (C) is further treated as follows. did.
(C-2) Second membrane filtration process
The permeated water obtained in the (C) membrane filtration treatment step from the raw water of Reference Example 1 (dioxin concentration 6,500 pg-TEQ / L) was filtered through an ultrafiltration membrane (hollow fiber type, molecular weight cut off 3,000). did. A part of the liquid (concentrate) that did not pass through the ultrafiltration membrane was added (returned) to the permeated water obtained in the (C-1) membrane filtration treatment step and filtered at an operating pressure of 0.2 MPa. . At this time, the dioxin concentration in the permeated water was 1 pg-TEQ / L or less, and the environmental standard value (1 pg-TEQ / L) or less.
The ultrafiltration membrane concentrate obtained in the step (C-2) was returned to the adsorption tank before the (C) membrane filtration treatment step in Reference Example 1 , but the treated water (discharged water) and chemical decomposition products There was no change in the dioxin concentration.

Example 9 (example of multiple filtration) (see FIG. 13)
The (B) adsorption treatment step, (C) membrane filtration treatment step, and (D) chemical decomposition step are carried out in the same manner as in Reference Example 1, and the permeated water obtained in step (C) is further treated as follows. did.
(C-2) Second membrane filtration process
The permeated water obtained in the membrane filtration treatment step (C) of Reference Example 1 was filtered through a nanofilter membrane (hollow fiber type, sodium chloride rejection 30%). A part of the liquid (concentrate) that did not pass through the nanofilter membrane was added (returned) to the permeated water obtained in the (C) membrane filtration treatment step, and filtered at an operating pressure of 0.5 MPa. At this time, the dioxin concentration in the permeated water was 1 pg-TEQ / L or less, and the environmental standard value (1 pg-TEQ / L) or less.
The concentrate of the nanofilter membrane obtained in the step (C-2) was returned to the adsorption tank before the (C) membrane filtration treatment step of Reference Example 1 , but the treated water (discharged water) and the dioxin of the chemical decomposition product There was no change in concentration.

Reference Example 7 ( Example of multi-stage filtration) (see FIG. 14)
(A) Membrane concentration treatment step, (B) Adsorption treatment step, (C) Membrane filtration treatment step and (D) Chemical decomposition step are carried out in the same manner as in Reference Example 2, and steps (A) and (C) The permeated water obtained in the above was further treated as follows.

(1) (B-2) Second adsorption treatment step and (C-2) Second membrane filtration treatment step for the permeated water obtained in step (A)
The permeated water obtained in the membrane concentration treatment step (A) of Reference Example 2 was placed in an adsorption tank having a residence time of 1 hour, and 100 ppm of activated clay was added as an adsorbent and adsorbed with stirring. The permeated water to which this adsorbent was added was filtered through an ultrafiltration membrane (hollow fiber type, molecular weight cut off 150,000). A part of the liquid (concentrate) that did not pass through the ultrafiltration membrane was added (returned) to the permeated water from step (B-2) to which the adsorbent was added, and the operating pressure was 0.2 MPa. Filtered. The dioxin concentration in the permeated water was 1 pg-TEQ / L or less, and was an environmental standard value (1 pg-TEQ / L) or less.

(2) (B-3) Third adsorption treatment step and (C-3) Third membrane filtration treatment step for the permeated water obtained in step (C)
The permeated water obtained in the membrane filtration treatment step (C) of Reference Example 2 was put in an adsorption tank having a residence time of 1 hour, and 1,000 ppm of activated clay was added as an adsorbent and adsorbed with stirring. The permeated water to which this adsorbent was added was filtered through an ultrafiltration membrane (hollow fiber type, molecular weight cut off 150,000). A part of the liquid (concentrate) that did not pass through the ultrafiltration membrane was added (returned) to the permeated water from step (B-3) to which the adsorbent was added, and the operating pressure was 0.3 MPa. Filtered through. The dioxin concentration of this permeated water was 1 pg-TEQ / L, which was less than the environmental standard value (1 pg-TEQ / L).
All the concentrates were returned to the adsorption tank in the (B) adsorption treatment process, but there was no change in the dioxin concentration of treated water (discharged water) and chemical decomposition products.

Reference Example 8 ( Example of multiple filtration) (see FIG. 15)
(A) Membrane concentration treatment step, (B) Adsorption treatment step, (C) Membrane filtration treatment step and (D) Chemical decomposition step are carried out in the same manner as in Reference Example 2, and steps (A) and (C) The permeated water obtained in the above was further treated as follows.

(1) (C-2) Second membrane filtration step for the permeated water obtained in step (A)
The permeated water obtained in the step (A) of Reference Example 2 was filtered through a reverse osmosis membrane (spiral type, sodium chloride rejection of 95%). A part of the liquid (concentrate) that did not permeate the reverse osmosis membrane was added (returned) to the permeated water from step (A) and operated at 1 MPa or more. The dioxin concentration of the permeated water was 1 pg-TEQ / L or less, and the environmental standard value (1 pg-TEQ / L) or less.

(2) (C-3) Third membrane filtration treatment step for the permeated water obtained in step (C)
The permeated water obtained in the step (C) of Reference Example 2 was filtered through a nanofilter membrane (hollow fiber type, sodium chloride rejection 30%). A part of the liquid (concentrate) that did not permeate the nanofilter membrane was added (returned) to the permeated water obtained in step (C), and filtered at an operating pressure of 0.6 MPa. The dioxin concentration of the permeated water at this time was 1 pg-TEQ / L or less, which was less than the environmental standard value (1 pg-TEQ / L).
The concentrate obtained in the step (C-2) and the concentrate obtained in the step (C-3) were returned to the adsorption tank of the step (B), but treated water (discharged water) and chemical decomposition There was no change in the dioxin concentration of the product.

Reference Example 9 ( Example of multiple filtration) (see FIG. 16)
(A) Membrane concentration treatment step, (B) Adsorption treatment step, (C) Membrane filtration treatment step and (D) Chemical decomposition step are carried out in the same manner as in Reference Example 2, and steps (A) and (C) The permeated water obtained in the above was further treated as follows.

(C-2) Second membrane filtration treatment step for the permeated water obtained in step (A) and the permeated water obtained in step (C)
Drainage (dioxin concentration 1.2 pg-TEQ / L) of the permeated water obtained in the step (A) of Reference Example 2 and the permeated water obtained in the step (C) was converted into a nanofilter membrane (hollow fiber type, (Sodium chloride rejection 30%). A part of the liquid (concentrate) that did not permeate the nanofilter membrane was added (returned) to the drained water matched to the permeated water obtained in the above steps (A) and (C), and 0.5 MPa was added. Filtration at an operating pressure of. The dioxin concentration of the permeated water at this time was 1 pg-TEQ / L or less, which was less than the environmental standard value (1 pg-TEQ / L).
The concentrate obtained in the step (C-2) was returned to the adsorption tank of the step (B), but there was no change in the dioxin concentration of the treated water (discharged water) and the chemical decomposition product.

Example 13
The treatment apparatus shown in FIG. 3 was used to detoxify contaminated water containing dioxins.
(A) Membrane concentration treatment step (including (E) chlorine neutralization step and (I) pre-filtration step)
In the reducing substance input part 10, the sodium bisulfite is 3 times the amount of free chlorine with respect to the contaminated water containing dioxins (dioxins concentration 6,300 pg-TEQ / L, free chlorine concentration 50 mg / L). It added under stirring so that it might be 150 mg / L.

  The contaminated water (electric conductivity: 3,000 μS / cm) added with sodium bisulfite is passed through a prefilter in the reverse osmosis membrane treatment unit 20 to remove large suspended solids, and then the desalination rate is 95%. Membrane treatment was performed with the above reverse osmosis membrane. In this reverse osmosis membrane treatment, a part of the liquid that did not permeate the reverse osmosis membrane was supplied to the reverse osmosis membrane again together with the contaminated water that passed through the prefilter. The electric conductivity was adjusted to 9,000 μS / cm or less, which is 3 times or less of contaminated water. The concentration of dioxins in the permeated water was 1.9 pg-TEQ, which was below the emission standard value (10 pg-TEQ / L).

(B) Adsorption treatment step and (F-1) first photolysis step Next, with respect to the liquid that did not pass through the reverse osmosis membrane (dioxin concentration 3,000 pg-TEQ / L), adsorbent addition and In the ultraviolet irradiation unit 30, 10 ppm of titanium dioxide, which is an adsorbent that can function as a photocatalyst, was added, mixed with stirring, and then irradiated with ultraviolet rays having a wavelength of 254 nm to photolyze dioxins. The concentration of dioxins in the liquid at this time is 1,200 pg-TEQ / L, and it can be seen that 60% was photodegraded.

(C) Membrane filtration process (including (G) backwash process)
The liquid fraction after the photolysis was subjected to membrane filtration treatment by passing it through an ultrafiltration membrane having a molecular weight cut off of 150,000 in the membrane filtration treatment section 40. In the membrane filtration treatment using this ultrafiltration membrane, a solution obtained by adding 3 ppm of hypochlorous acid to the permeate obtained by the treatment by the above-described (A) reverse osmosis membrane treatment was used as the backwash water. Once per minute, the ultrafiltration membrane was washed with 4 times the amount of water permeated through the ultrafiltration membrane. The concentration of dioxins in the permeated water that passed through the ultrafiltration membrane was 0.65 pg-TEQ / L and an emission standard value (10 pg-TEQ / L) or less.
Then, the reverse osmosis membrane permeated water and the ultrafiltration membrane permeated water were combined to be discharged water (dioxins concentration was 1.5 pg-TEQ / L).

(F-2) Second photolysis step The concentrate (backwash water) obtained by membrane filtration treatment is transferred to the ultraviolet irradiation unit 50, and 100 ppm of hydrogen peroxide, which is a photolysis accelerator, is added, Again, ultraviolet rays having a wavelength of 254 nm were irradiated to photolyze dioxins. The concentration of dioxins in the liquid at this time is 120 pg-TEQ / L, and it can be seen that 90% was photodegraded.

(H) Aggregation and separation step In the aggregate after photolysis, 1,000 ppm of polyaluminum chloride is added as an aggregating agent in the aggregating agent addition unit 60, and the mixture is gently stirred to sufficiently absorb the adsorbent adsorbing dioxins. After agglomeration, the agglomerate was allowed to settle for 18 hours while stirring at a rotational speed of 1 rpm so that the sediment did not harden at the bottom. The clear supernatant was returned to the adsorbent addition / ultraviolet irradiation section 30.

(D) Chemical decomposition process In the chemical decomposition process part 80, 4g (100 times mole with respect to dioxins) of powdery sodium persulfate is added as a precipitate, and a sediment makes the whole volume 40 mL with water. After that, the chemical decomposition treatment was performed by heating at a temperature of 70 ° C. for 24 hours while stirring. After the chemical decomposition was completed, the decomposition product was allowed to stand to separate into solid and liquid.
The concentration of dioxins in the supernatant was 32 pg-TEQ / L. The supernatant was neutralized with a 20% aqueous sodium hydroxide solution and returned to the adsorbent addition / ultraviolet irradiation section 30.
The amount of dioxins in the concentrate (solid matter) after chemical decomposition was 270 pg-TEQ / g, which was below the emission standard value for industrial waste (3,000 pg-TEQ / g).

  The method of the present invention chemically decomposes difficult-to-decompose organic compounds such as dioxins and PCBs contained in, for example, industrial wastewater, soil leachate, cleaning wastewater generated in incinerator demolition work, and concentrates thereof. Can be made harmless, and can be widely used as a treatment method that can stably reduce the concentration of a hardly decomposable substance in the discharged water to a discharge standard value or less.

It is a flowchart which shows the structure of the essential process of the processing method of the hardly decomposable substance containing water of this invention. It is a flowchart which shows the structure of the one aspect | mode of the processing method of the hardly decomposable substance containing water of this invention. It is a schematic diagram of the processing apparatus for implementing one aspect | mode of the processing method of the hardly decomposable substance containing water of this invention. 1 is one embodiment of the apparatus of the present invention including a multiple filtration step. It is another embodiment of the apparatus of this invention including a multiple filtration process. It is a schematic diagram of the apparatus used in Reference Example 1. It is a schematic diagram of the apparatus used in Reference Example 2. It is a schematic diagram of the apparatus used in Reference Example 3. It is a schematic diagram of the apparatus used in Reference Example 4. 10 is a schematic diagram of an apparatus used in Reference Example 5. FIG. It is a schematic diagram of the apparatus used in Reference Example 6. 10 is a schematic diagram of an apparatus used in Example 7. FIG. It is a schematic diagram of the apparatus used in Examples 8 and 9. 10 is a schematic diagram of an apparatus used in Reference Example 7. FIG. 10 is a schematic diagram of an apparatus used in Reference Example 8. FIG. 10 is a schematic diagram of an apparatus used in Reference Example 9. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing apparatus 10 Reducing substance input part 11 Input tank 12 Reducing substance supply part 20 Membrane concentration processing part 21 Prefilter 22 Reverse osmosis membrane 30 Adsorbent addition / ultraviolet irradiation part 31 Processing tank 32 Adsorbent addition part 33 Ultraviolet lamp 40 Membrane filtration processing unit 41 Ultrafiltration membrane 42 Backwash water tank 43 Disinfectant supply unit 50 Ultraviolet irradiation unit 51 Decomposition tank 52 Accelerator supply unit 53 Ultraviolet lamp 60 Coagulant addition unit 61 Coagulation tank 62 Coagulant supply unit 70 Solid liquid Separation section 71 Sedimentation tank 80 Chemical decomposition treatment section 81 Decomposition tank 82 Oxidant supply section

Claims (10)

The following process:
(B) Water containing a hardly decomposable substance selected from the group consisting of halogenated dibenzodioxins, halogenated dibenzofurans, and PCBs including coplanar PCBs substituted with a chlorine atom in addition to the ortho position (treated raw water) In addition, titanium dioxide and / or diatomaceous earth is added as an adsorbent so as to be 1 to 1000 ppm, the hardly decomposable substance is adsorbed on the adsorbent, and water containing the adsorbent adsorbing the hardly decomposable substance is obtained. Process (adsorption treatment process)
(C) Water containing an adsorbent adsorbing the hardly decomposable substance is converted into ultrafiltration membrane (UF membrane), nanofilter membrane (NF membrane), microfiltration membrane (MF membrane) and reverse osmosis membrane (RO membrane). Using a filtration membrane selected from the group consisting of: separating permeated water that does not contain an adsorbent that adsorbs a hardly decomposable substance, and backwashing the filter membrane to concentrate the adsorbent that adsorbs the hardly decomposable substance To obtain the treated water (membrane filtration process)
(D) The hardly decomposable substance adsorbed on the adsorbent in the water in which the adsorbent that adsorbs the hardly decomposable substance is concentrated on the hardly decomposable substance without desorption from the adsorbent. The process of chemically decomposing difficult-to-decompose substances by bringing them into contact with peroxides (chemical decomposition process)
(C-2) A step of separating the permeated water separated in the step (C) into water and permeated water in which a hardly decomposable substance is concentrated using a reverse osmosis membrane or a nanofilter (second membrane filtration Treatment method), and a method of treating the water containing the hardly decomposable substance, including the step of returning the water concentrated with the hardly decomposable substance separated in the step (C-2) to the step (B).   The method for treating hardly decomposable substance-containing water according to claim 1, wherein in the step (D), the peroxide is used in an amount of 100 times mol or more with respect to the hardly decomposed substance. Prior to the step (B), (A) the hardly decomposable substance is concentrated from the water containing the hardly decomposable substance (treated raw water) using a reverse osmosis membrane (RO membrane) or a nanofilter membrane (NF membrane). Of separating the separated water and permeate (membrane concentration treatment process)
The processing method of the hardly decomposable substance containing water of Claim 1 or 2 containing this.   Before the said process (A) or the said process (B), (E) The process (chlorine neutralization process) of neutralizing the chlorine in the water (process raw water) containing a hardly decomposable substance is included. The method for treating water containing a hardly decomposable substance according to any one of 3 above. (H) A step of adding a flocculant to water in which the adsorbent that has adsorbed the hardly decomposable substance is concentrated, aggregating and sedimenting the adsorbent adsorbing the hardly decomposable substance, and separating the supernatant (aggregation separation step) )
The processing method of the hardly decomposable substance containing water of any one of Claims 1-4 containing this. Further, the permeated water separated in the step (A) and / or the supernatant separated in the step (H) are concentrated with water and permeated water using a reverse osmosis membrane or a nanofilter, and the refractory substance is concentrated. The process (3rd membrane filtration process process) isolate | separated into (3), and the process of returning the water where this hardly decomposable substance was concentrated to the said process (B), It is any one of Claims 1-5 A method for treating water containing persistent substances.   The halogenated dibenzodioxins are 2,3,7,8-tetrachlorodibenzo-P-dioxin, 1,2,3,7,8-pentachlorodibenzo-P-dioxin, 1,2,3,4, 7,8-hexachlorodibenzo-P-dioxin, 1,2,3,4,6,7,8-heptachlorodibenzo-P-dioxin and 1,2,3,4,6,7,8,9-octa From the group consisting of chlorodibenzo-P-dioxins, the halogenated dibenzofurans are 2,3,7,8-tetrachlorodibenzofuran, 1,2,3,7,8-pentachlorodibenzofuran, 1,2,3, Consists of 4,7,8-hexachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzofuran and 1,2,3,4,6,7,8,9-octachlorodibenzofuran And PCBs including coplanar PCBs substituted with chlorine atoms in addition to the ortho positions are 3,3 ′, 4,4 ′, 5-tetrachlorobiphenyl, 3,3 ′, 4,4 ′, 5- The method for treating water containing a hardly decomposable substance according to any one of claims 1 to 6, which is selected from the group consisting of pentachlorobiphenyl and 3,3 ', 4,4', 5,5'-hexachlorobiphenyl. .   The method for treating hardly-decomposable substance-containing water according to any one of claims 1 to 7, wherein the adsorbent added in the step (B) is titanium dioxide.   The method for treating hardly-decomposable substance-containing water according to any one of claims 1 to 8, wherein the peroxide used in the step (D) is a persulfate. At least a part of water concentrated in the hardly decomposable substance obtained in the step (A) and / or water concentrated in the adsorbent adsorbing the hardly decomposable substance obtained in the step (C), 2. It adds to the hardly decomposable substance-containing water (treated raw water), and at least one step selected from the group consisting of the step (A), the step (B) and the step (C) is performed again. The processing method of the hardly decomposable substance containing water of any one of -9.

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