JP2002153891A - Treatment method for refractory material-containing waste water and equipment for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for refractory material-containing waste water which is capable of decomposing refractory materials, such as environmental hormones as represented by dioxins, bisphenols A and co-PCBs even in high-concentration SS-containing waste water, does not allow the refractory materials to remain in sludge and treated water and minimizes a floor area. SOLUTION: This waste water equipment has a treating vessel 10 for oxidatively decomposing the refractory materials included in the waste water 1 by combination of >=1 among oxidizing agents, such as ozone 14a or hydrogen peroxide 15 or the like, and irradiation with UV rays 19. The equipment is provided with a solid-liquid separator 11 by membrane separation behind the treating vessel 10 and has a return line of at least the portions of the solid content 3 discharged from the solid-liquid separator 11 to the decomposing treatment means. Dioxin cracking equipment 20 for the discharged solid content is interposed on a line for feeding the discharged solid content 3b to a dehydrator 12 on the downstream side from the branch point of the return line to dehydrate the discharged solid content 3D by the dehydrator 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to dioxins, bisphenol A, environmental hormones represented by co-PCB and the like contained in leachate of waste incineration ash landfills and smoke and wastewater from waste incinerators. Particularly, the present invention relates to a wastewater treatment method and apparatus for oxidatively decomposing decomposable substances and oxidizing and decomposing the hardly decomposable substances using ultraviolet rays and oxidizing agents such as ozone and hydrogen peroxide.

[0002]

2. Description of the Related Art Conventionally, refractory substances such as dioxins, bisphenol A, and environmental hormones represented by co-PCB contained in leachate from waste incineration ash landfills and wastewater from smoke incinerators. The oxidative decomposition method is often used for the treatment. This treatment method comprises adding an oxidizing agent such as ozone or hydrogen peroxide to the hardly decomposable substance-containing wastewater and decomposing the wastewater into carbon dioxide and chloride ions under oxidizing conditions. A method of adding ozone or hydrogen peroxide and irradiating with ultraviolet rays has also been adopted as a method for obtaining this. This is a thing which is oxidatively decomposed by the action of a very oxidatively strong hydroxyl radical generated when irradiating ultraviolet rays in the presence of the oxidizing agent,
The decomposition power is much higher than the oxidizing power of an oxidizing agent such as ozone or hydrogen peroxide alone.

However, refractory substances such as dioxins, bisphenol A, and environmental hormones represented by co-PCB have very low solubility in water, and most of the refractory substances in wastewater are SS (floating). Present in a form attached to or contained in the substance. Accordingly, since the contact ratio with the hydroxyl radical is lower than that of the dissolved hardly decomposable substance and it is difficult to perform oxidative decomposition, a method for efficiently treating the hardly decomposable substance attached to and contained in SS is required. Have been.

As a treatment method effective for wastewater having a high SS concentration in wastewater, Japanese Patent Application Laid-Open No. 9-225482 discloses ozone and hydrogen peroxide, ozone and hydrogen peroxide and ultraviolet irradiation, and hydrogen peroxide and ultraviolet light. A method has been proposed in which the generation of active species (hydroxy radicals) is promoted by irradiation or the like, and oxidative decomposition of a hardly decomposable substance is performed. As shown in FIG. 3, the present invention comprises a reforming step 04 for decomposing by the active species and a coagulation sedimentation step 03 provided at the latter stage of the reforming step. Advanced processing became possible without accompanying.

[0005]

However, in the prior art, since a coagulant is used, solid-liquid separation is not performed reliably, and there is a possibility that particulate solids may remain on the liquid side. There is a concern that the waste may be emitted while containing hardly decomposable substances. In addition, a coagulant must be used properly according to the wastewater, and in some cases, separation and partitioning cannot be performed with only one coagulant. In addition, a post-treatment suitable for each coagulant must be performed. Further, it takes a long time for coagulation and sedimentation, so that the treatment efficiency is poor. When the amount of wastewater is large, the apparatus itself must be enlarged. Further, the sludge 011 separated in the solid-liquid separation tank 010 contains a large amount of hardly decomposable substances, and a treatment device for the sludge 011 must be newly provided.

In order to solve the above problems, the present invention is capable of decomposing hardly decomposable substances such as dioxins, bisphenol A and environmental hormones represented by co-PCB even in wastewater containing SS at a high concentration. It is an object of the present invention to provide a method for treating a wastewater containing a hardly decomposable substance, which does not leave the hardly decomposable substance in sludge or treated water and can reduce the installation area, and an apparatus therefor.

[0007]

Means for Solving the Problems In order to solve the above problems, the invention according to claim 1 is a method for resolving dioxins, bisphenol A, and environmental hormones represented by co-PCB contained in wastewater. In a wastewater treatment method in which a substance is oxidatively decomposed by one or two or more of an oxidizing agent such as ozone or hydrogen peroxide and ultraviolet irradiation, the oxidatively decomposed wastewater is solid-liquid separated by membrane separation or other solid-liquid separation means. It is characterized in that it is separated, and at least a part of the separated solid is returned and subjected to oxidative decomposition treatment again.
The invention uses a method of generating hydroxyl radicals using any one of the oxidizing agent such as ozone or hydrogen peroxide and ultraviolet irradiation to promote the oxidative decomposition of the hardly decomposable substance. The waste water after the oxidative decomposition is passed through a membrane having fine pores to perform solid-liquid separation. Accordingly, the SS component in the wastewater can be easily separated, and most of the hardly decomposable substances in the wastewater that cannot be removed by the oxidative decomposition are attached to and contained in the SS component and can be separated.

[0008] At least a part of the separated solids is withdrawn and returned and subjected to the oxidative decomposition treatment again, so that the solids to be discharged can be suppressed below the emission regulation value of harmful substances. The concentration of the hardly decomposable substance in the oxidative decomposition treatment tank is increased by the returned solids, and the decomposition rate of the hardly decomposable substance is improved. This is apparent from FIG. 2 showing the initial concentration of dioxins and the decomposition rate constant, and the decomposition rate constant K of dioxins increases almost in proportion to the initial concentration of dioxins. Therefore, it can be said that the higher the concentration of the substance to be treated in the wastewater, the higher the decomposition rate. The drainage A and drainage B are at an ozone supply rate of 0.4 g / m ³ / min, and the drainage C and drainage D are at an ozone supply rate of 1.2 g / m ³ · min.

Further, as an apparatus for suitably realizing the above-mentioned invention, the invention according to claim 2 is characterized in that a hardly decomposable substance such as dioxins, bisphenol A, and environmental hormones represented by co-PCB contained in wastewater is used. In a drainage device provided with a decomposition treatment means for oxidatively decomposing by one or more of an oxidizing agent such as ozone or hydrogen peroxide and ultraviolet irradiation, a membrane separation of oxidatively decomposed wastewater is provided at a stage subsequent to the decomposition treatment means. A solid-liquid separating means for performing solid-liquid separation by other means is provided, and a return line for returning at least a part of the solid component discharged from the solid-liquid separating means to the decomposition processing means is provided. In this case, the solid-liquid separation means may be configured by combining one or more means selected from among coagulation sedimentation and filtration, in addition to membrane separation. Furthermore, the invention described in claim 3 provides the invention according to claim 2
A flow control means is provided on the return line described above, and the return amount of the solid is adjusted according to the concentration of the solid content and the concentration of the hardly decomposable substance in the decomposition treatment means.

As described above, by providing the flow control valve and the pump, the amount of solids returned to the decomposition processing means can be adjusted, and the solid content in the decomposition processing means and the concentration of the hardly decomposable substance can be adjusted. The decomposition treatment of the hardly decomposable substance can be performed in the most efficient state. In addition, by circulating the solids separated by the membrane separation means as described above, the solids concentration in the decomposition treatment means gradually increases, so that the ultraviolet transmittance decreases and the oxidative decomposition rate decreases. It is advisable to increase the amount of the oxidizing agent or supply another type of oxidizing agent to promote the generation of hydroxy ions.

According to a fifth aspect of the present invention, there is provided a dehydration line for returning a part of the solid discharged from the solid-liquid separating means to the decomposition treatment means and dehydrating the remaining discharged solid through a dioxin decomposing device. It is characterized by having.

According to this invention, not all the solids discharged from the solid-liquid separation means are decomposed by dioxin, but the solids in the return line are left as they are, and the remaining discharged solids discharged without being returned are removed. Since dehydration is performed through the dioxin decomposer, the efficiency is improved without applying an extra load to the dioxin decomposer.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention thereto, unless otherwise specified, and are merely illustrative examples. Not just. FIG. 1 is a schematic configuration diagram of a wastewater treatment apparatus according to an embodiment of the present invention, in which reference numeral 10 denotes a treatment tank for performing a decomposition treatment of a hardly decomposable substance, 11 denotes a solid / liquid separation apparatus for performing solid / liquid separation, 12 denotes a dehydration apparatus, Reference numerals 16 and 18 denote pumps, and reference numerals 17a and 17b denote circulation amount control valves for adjusting the circulation amount of the waste water.

The wastewater 1 to be treated in the present embodiment is wastewater containing refractory substances such as dioxins, bisphenol A, and environmental hormones represented by co-PCB discharged from a waste incineration plant. The wastewater 1 has a high SS concentration. The processing tank 10 is provided with an ultraviolet lamp 19, which is preferably 185 lamps.
It is preferable to use a low-pressure mercury lamp, an excimer laser, or the like that generates ultraviolet light having a low wavelength of 254 nm or 254 nm. The ozone generator 13 is provided with an ozone diffuser 14 for supplying ozone generated in the ozone generator 13 into the processing tank 10. , The processing tank 1
It is configured such that the inside of 0 is mixed and stirred. Further, the treatment tank 10 is provided with a hydrogen peroxide inlet, and is configured to be able to supply a hydrogen peroxide 15 as needed.

In the present embodiment, means for generating hydroxy radicals in the processing tank 10 include ozone and ultraviolet irradiation, hydrogen peroxide and ultraviolet irradiation, ozone and hydrogen peroxide,
Ozone, hydrogen peroxide, and ultraviolet irradiation may be mentioned. Of these methods, in the case of ozone and ultraviolet irradiation, for example, a low-pressure mercury lamp having an output of 10 to 200 W and a wavelength of 185 are used.
254 nm is irradiated to waste water having an ozone concentration of 10 g / m ³ . Also, with hydrogen peroxide and UV irradiation,
The method of irradiating low-wavelength ultraviolet rays with the low-pressure mercury lamp while setting the injection amount of hydrogen peroxide to 10 to 5000 mg / l and using ozone and hydrogen peroxide together is to set the injection amount of ozone to 50 to 5000 mg / l. The method of irradiating ultraviolet rays with an injection amount of hydrogen peroxide of 10 to 5000 mg / liter and using a combination of ozone and hydrogen peroxide generates hydroxy radicals by combining the above methods.

On the downstream side of the treatment tank 10, a solid-liquid separation device 11 is provided. The solid-liquid separation device 11 is configured to allow suspended solids such as SS components to be removed by permeating waste water. A membrane having fine pores separable from permeated water is provided. Such a membrane has a pore size of 0.5 μm to 1.0 μm.
Use a material that can reliably separate solids in wastewater with a diameter of about m. In addition, in the case of wastewater having a high SS concentration, it is particularly easy to block, so that a tubular type or a flat membrane type, which is resistant to blockage, is used. Further, when a predetermined amount of treated water cannot be obtained, the filtration rate is recovered by washing. The solid-liquid separation device 11 may be configured not only by the solid-liquid separation device but also by a combination of one or more devices selected from the coagulation sedimentation and the filtration.

The dewatering device 12 for dewatering the solids separated by the solid-liquid separation device 11 includes a mechanical dehydration such as a centrifugal separator and a filtration device, a dehydration by sedimentation and concentration, and a heat dehydration such as an evaporator and a drier. Any of dehydration and the like may be used.

Next, the operation of the wastewater treatment apparatus according to the present embodiment will be described. The wastewater having a high SS concentration discharged from a waste incineration facility or the like is introduced into the treatment tank 10 and mixed and stirred by ozone-containing bubbles generated by the ozone generator 13 and supplied from the ozone diffuser 14. It is oxidatively decomposed by hydroxyl radicals generated in wastewater by ultraviolet irradiation in the presence of ozone. Then, the oxidatively decomposed treated water 2 is fed to a solid-liquid separator 11, where the treated water 2 is separated into a solid 3 containing SS component and treated water 4. In the wastewater, most of the hardly decomposable substances are S
Since the treated water 4 hardly contains undecomposed and hardly decomposable substances, which is attached to or contained in the S component, the treated water 4 is discharged out of the system or returned to the waste incineration facility and recycled. It is possible to do.

On the other hand, the solid 3 containing the hardly decomposable substance remaining in the oxidative decomposition treatment is sent out of the solid-liquid separator 11 by the pumps 16 and 18,
The amount of return according to the concentration or the concentration of the hardly decomposable substance, or the amount of the returned so that the concentration of the hardly decomposable substance remaining in the sludge 6 discharged out of the system becomes equal to or less than the emission regulation value, is appropriately determined. By adjusting 17a and 17b, the returned solid portion 3a is sent to the treatment tank 10 and the discharged solid portion 3b is sent to the dehydrating device 12, respectively.

The returned solids 3a are introduced into the treatment tank 10 and again subjected to the oxidative decomposition treatment together with the waste water 1. In this manner, by returning the solid portion 3a to the processing tank 10, the concentration of the hardly decomposable substance in the processing tank 10 is increased, and the decomposition rate is further improved. Further, by circulating the solid component 3a, the SS concentration in the processing tank 10 gradually increases,
Accordingly, the ultraviolet transmittance decreases, so that hydrogen peroxide 1
5 is supplied to generate a hydroxyl radical. Thereby, oxidative decomposition is promoted by the oxidizing power of the hydroxyl radical and the oxidizing power of each of hydrogen peroxide and ozone.

When the content of the hardly decomposable substance in the solid content is reduced below the emission regulation value, the discharged solid content is increased, the returned solid content 3a is reduced, and the solid content concentration in the processing tank 10 is reduced. It is good to let. Then, the solid content is subjected to dehydration treatment of centrifugal separation and filtration in the dehydrator 12 and discharged out of the system as sludge having a low water content, and the treated water 5 is circulated or discharged together with the treated water 4 to the outside. Is done.

As described above, by maintaining the concentration of the hardly decomposable substance in the treatment tank 10 at a certain level or more, it is possible to maintain the decomposition treatment speed at which the treatment can be performed with high efficiency, and to reduce the sludge discharged to the outside of the system. Since the concentration of the hardly decomposable substances contained can be kept below the emission regulation value, it is not necessary to add a new treatment facility.

FIG. 4 is a modified example of the waste water treatment apparatus according to the embodiment of FIG. 1, which is a portion downstream of a return line for returning a part of solids discharged from the solid-liquid separation device 11 to the decomposition treatment means. The exhausted solids 3b are supplied to the dehydrating device 12 on the side thereof, and the discharged solids are interposed in the dioxin decomposing device 20 and dehydrated by the dehydrating device 12 through the dioxin decomposing device 20. Then, the solids in which the dioxin has been decomposed are subjected to dehydration treatment of centrifugal separation and filtration in a dehydrator 12 and discharged out of the system as sludge having a low water content, and the treated water 5 is circulated and used together with the treated water 4. Or it is discharged outside the system. (Note that the pump 16 is omitted.)

[0024]

As described above, according to the present invention, by performing solid-liquid separation treatment after oxidative decomposition treatment, SS in wastewater can be easily separated. Further, since almost all of the hardly decomposable substances in the wastewater which could not be removed by the oxidative decomposition adhere to and are contained in the SS component, almost no hardly decomposable substances remain in the treated water discharged out of the system. . Further, since such processing is preferably performed by membrane separation, the processing speed can be maintained and the installation area of the apparatus can be minimized. In particular, according to the fifth aspect of the present invention, not all solids discharged from the solid-liquid separation device 11 are decomposed into dioxins, but the solids in the return line are kept as they are, and the remaining discharge discharged without being returned is returned. Since the solid content is dehydrated through the dioxin decomposer, the efficiency is improved without applying an extra load to the dioxin decomposer.

Further, at least a part of the solids separated by the membrane separation or other solid-liquid separation treatment is extracted and returned, and the oxidative decomposition treatment is again performed, so that the solids discharged to the outside of the system are harmful substances. It is possible to reduce the concentration of the hardly decomposable substance in the oxidative decomposition treatment tank by the returned solids, and the decomposition rate of the hardly decomposable substance is improved, thereby improving the efficiency. Thus, the decomposition process can be performed. In order to reduce the transmittance of ultraviolet rays due to the increase in SS in the treatment tank due to the return of solids after the membrane separation, supply of hydrogen peroxide or increase in the supply of ozone is performed to increase the generation of hydroxy ions. As well as the oxidizing power of each single substance increases,
The decomposition processing speed can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a wastewater treatment device according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between initial concentrations of dioxins and decomposition rate constants.

FIG. 3 is a flowchart showing a wastewater treatment method for wastewater containing hardly decomposable organic matter in the related art.

FIG. 4 shows a schematic configuration diagram of a wastewater treatment apparatus according to another modification of the wastewater treatment apparatus of FIG. 1 according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waste water 4, 5 Discharge treated water 6 Discharged sludge 10 Processing tank 11 Solid-liquid separation device 12 Dehydration device 13 Ozone generator 14 Ozone diffuser 16, 18 Pump 17a, 17b Circulation control valve 19 Ultraviolet lamp 20 Dioxin decomposition device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) C02F 1/78 C02F 1/78 9/00 502 9/00 502E 502P 502R 502N 503 503C 504 504B 504E // C02F 1/00 1/00 L (72) Inventor Yuji Yasuda 12 Nishikicho, Naka-ku, Yokohama-shi F-term in Mitsubishi Heavy Industries, Ltd. Yokohama Works 4D006 GA07 KA01 KA03 KB04 KC01 KD21 KD22 MA02 MA03 PB08 PB15 4D015 BA19 BA25 BB01 CA20 EA32 FA24 4D037 AA11 AB02 AB11 AB14 AB16 BA18 BB01 CA02 CA08 CA11 4D050 AA12 AB15 AB19 BB02 BB09 BC09 BD06 CA09 CA15 CA16 4D062 BA19 BA25 BB01 CA20 EA32 FA24

Claims (5)

[Claims] 1. An insoluble substance such as dioxins, bisphenol A, and environmental hormones represented by co-PCB contained in wastewater is treated with one or two of an oxidizing agent such as ozone or hydrogen peroxide and ultraviolet irradiation. In the wastewater treatment method for oxidative decomposition by the above combination, the oxidative decomposition treatment wastewater is subjected to solid-liquid separation by solid-liquid separation means, and at least a part of the separated solid is returned and subjected to the oxidative decomposition treatment again. A method for treating wastewater containing a hardly decomposable substance. 2. The method according to claim 1, further comprising the step of removing a hardly decomposable substance such as dioxins, bisphenol A, and environmental hormones represented by co-PCB contained in the wastewater by oxidizing agent such as ozone or hydrogen peroxide and ultraviolet irradiation. In a drainage device provided with a decomposition treatment means that oxidatively decomposes by the above combination, a solid-liquid separation means for solid-liquid separation of the oxidatively decomposed wastewater by membrane separation is provided at a stage subsequent to the decomposition treatment means,
An apparatus for treating wastewater containing hardly decomposable substances, comprising a return line for returning at least a part of solids discharged from the solid-liquid separation means to the decomposition treatment means. 3. The method according to claim 1, wherein a flow rate adjusting means is provided on the return line, and a return amount of the solid content is adjusted according to a solid content concentration and a hardly decomposable substance concentration in the decomposition treatment means. 2. An apparatus for treating wastewater containing a hardly decomposable substance according to 2. 4. The treatment of wastewater containing a hardly decomposable substance according to claim 2, wherein the solid-liquid separation means according to claim 2 is one or more means selected from membrane separation, coagulation sedimentation, and filtration. apparatus. 5. A dewatering line for returning a part of the solids discharged from the solid-liquid separation means to the decomposition treatment means and dewatering the remaining discharged solids through a dioxin decomposer. 3. The treatment device for wastewater containing a hardly decomposable substance according to claim 2.