JP2005058854A - Method and apparatus for waste water treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently decompose 1,4-dioxane and remove it from real waste water, such as sewage waste water and leachate waste water, containing the 1,4-dioxane. <P>SOLUTION: Before the 1,4-dioxane contained in the waste water is decomposed and removed by dioxane decomposing devices 20, 54 using an advanced oxidation method or a Fenton oxidation method, decomposition and removal of organic substances coexisting in the waste water in a biological treatment tank 12 and solid-liquid separation of the waste water are carried out as pretreatments before dioxane decomposition. Then the separated water generated by the solid-liquid separation is treated by the dioxane decomposing devices 20, 54. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wastewater treatment method and apparatus, and more particularly to a wastewater treatment method and apparatus for decomposing and removing 1,4-dioxane contained in wastewater by an accelerated oxidation method or a Fenton oxidation method.

  1,4-Dioxane is generally used as a solvent and is also contained in detergents such as commercially available polyoxyalkyl ethers. For this reason, 1,4-dioxane is contained in wastewater from the process of producing 1,4-dioxane, or wastewater from the process of producing and using polyethylene-based products. Since it is a hardly degradable substance, it can hardly be decomposed and removed by biological treatment at a sewage treatment plant, and water pollution has been pointed out.

  As a method for decomposing and removing such a hardly decomposable substance, conventionally, an ozone oxidation method, an activated carbon adsorption method, a coagulation precipitation method, an accelerated oxidation method (see Patent Document 1, Patent Document 2, and Patent Document 3), and Fent oxidation There is a law.

However, although 1,4-dioxane can be expected to be slightly decomposed by the ozone oxidation method, it has a drawback of poor reaction efficiency. In addition, 1,4-dioxane is difficult to remove by the adsorption method because of its poor activated carbon adsorption property, and furthermore, since it is highly water soluble, it cannot be removed by coagulation precipitation. On the other hand, it has been reported that 1,4-dioxane can be decomposed by the accelerated oxidation method or the Fenton oxidation method, and synthetic wastewater containing 1,4-dioxane is treated by the accelerated oxidation method or the Fenton oxidation method. It is possible.
JP 2001-029966 A JP 2001-121163 A JP 2000-202466 A

  However, wastewater containing 1,4-dioxane collected from actual wastewater such as leachate wastewater from sewage treatment plants and landfills, not synthetic wastewater, is not subject to 1,4-dioxane even when the accelerated oxidation method or Fenton oxidation method is applied. Cannot be sufficiently decomposed and removed, and further improvement is necessary to increase the effectiveness of the accelerated oxidation method and the Fenton oxidation method.

  The present invention was made in view of such circumstances, and wastewater treatment capable of efficiently decomposing and removing 1,4-dioxane from actual wastewater such as sewage wastewater and leachate wastewater containing 1,4-dioxane. It is an object to provide a method and apparatus.

  In order to achieve the above object, claim 1 of the present invention is a wastewater treatment method in which 1,4-dioxane contained in wastewater is decomposed and removed in a dioxane decomposition step by an accelerated oxidation method or a Fenton oxidation method. As a pretreatment of the process, an organic substance removal process for decomposing and removing organic substances coexisting in the wastewater in a biological reaction tank, and a solid-liquid separation process for solid-liquid separation of the wastewater treated in the organic substance removal process are provided. The separated water separated in the separation step is treated in the dioxane decomposition step.

  Here, the accelerated oxidation method is a method of promoting oxidation mainly by ozone treatment and using at least one of hydrogen peroxide treatment and ultraviolet treatment in combination. The Fenton oxidation method is an oxidation method using OH radicals generated by adding hydrogen peroxide under a metal catalyst.

  According to claim 1 of the present invention, as a pretreatment for decomposition and removal in the dioxane decomposition step by the accelerated oxidation method or the Fenton oxidation method, organic substances in the wastewater are decomposed and removed, and further, SS components in the wastewater are separated by solid-liquid separation. The 1,4-dioxane was decomposed and removed by the accelerated oxidation method or the Fenton oxidation method for the separated water that had been pretreated, and the 1,4-dioxane decomposition performance was improved. be able to.

  In the case of organic matter treatment in a biological reaction tank, there is concern about an increase in excess sludge due to the conversion of organic matter to SS components. However, as a characteristic of wastewater containing 1,4-dioxane, polyethylene glycol-based organic matter such as ethylene Since a large amount of glycol coexists, there is almost no increase in excess sludge. That is, polyethylene glycol-based organic matter is easily decomposed by biological treatment with activated sludge and the like, and the conversion rate from organic matter (BOD) to solid substance (SS) (sludge conversion rate) is small. Therefore, even if the biological treatment tank in the sewage treatment plant is used as it is for the organic substance decomposition removal in the dioxane decomposition process, 1,4-dioxane is efficiently used in the dioxane decomposition process with almost no excess sludge in the biological reaction tank. Can be decomposed and removed.

  Next, a solid-liquid separation step is performed for solid-liquid separation of the wastewater treated in the organic matter removal step, and the separated water separated in the solid-liquid separation step is treated in the dioxane decomposition step. As a result, the SS component, which is a factor that lowers the decomposition performance of 1,4-dioxane, in the accelerated oxidation method or the Fenton oxidation method, particularly in the accelerated oxidation method when accompanied by ultraviolet irradiation, can be removed. The decomposition performance of 1,4-dioxane by the Fenton oxidation method can be further improved.

  Claim 2 is the method of claim 1, wherein the ratio of the organic matter concentration (mg / L) to the 1,4-dioxane concentration (mg / L) contained in the wastewater is 1.5 or less. It is characterized by decomposing and removing organic matter in wastewater in the organic matter removing step. This is closely related to the organic matter concentration relative to the 1,4-dioxane concentration in the wastewater and the decomposition rate of the accelerated oxidation method or the Fenton oxidation method. This is because when the ratio is 5 or less, the decomposition rate increases rapidly. A particularly preferable value of the organic substance concentration relative to the 1,4-dioxane concentration is 1 or less.

  A third aspect of the present invention is characterized in that, in the first or second aspect, the wastewater contains a 1,4-dioxane concentration of 10 mg / L or more. This is particularly significant when the concentration of 1,4-dioxane in the wastewater is 10 mg / L or more, and the coexistence of organic substances in the accelerated oxidation method or the Fenton oxidation method has a significant impact on 1,4-dioxane decomposition performance. This is because the present invention is effective.

  A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, when the dioxane decomposition step is performed by the accelerated oxidation method, the generated waste ozone gas is blown into the biological reaction tank. Thereby, the sludge of a biological reaction tank can be decomposed | disassembled with waste ozone gas, the excess sludge generation amount can be reduced, and the burden in a solid-liquid separation process can be reduced. Further, by blowing waste ozone gas into the biological reaction tank, the sludge conversion rate, which is the conversion rate of organic matter to SS, can be reduced, and a reduction in the amount of excess sludge generated can be expected.

  A fifth aspect according to any one of the first to third aspects, wherein when the dioxane decomposition step is performed by the Fenton oxidation method, the addition of the metal catalyst under metal catalyst and hydrogen peroxide is performed in a plurality of stages. Features. Thus, by performing the addition of the metal catalyst and hydrogen peroxide in a plurality of stages, it is possible to improve the decomposition performance of 1,4-dioxane by the Fenton oxidation method. This is because hydrogen peroxide itself has the property of reacting with OH radicals. Therefore, when high concentration of hydrogen peroxide is added at a time under a metal catalyst, excess hydrogen peroxide reacts with 1,4-dioxane. This is because it reacts with hydrogen oxide itself and the decomposition efficiency of 1,4-dioxane is reduced.

  In order to achieve the object, claim 6 of the present invention is a wastewater treatment apparatus for decomposing and removing 1,4-dioxane contained in wastewater, a biological reaction tank for decomposing and removing organic substances coexisting in the wastewater, Solid-liquid separation device for solid-liquid separation of wastewater treated in the biological reaction tank, and 1,4-dioxane contained in the separated water separated by the solid-liquid separation device is decomposed by an accelerated oxidation method or a Fenton oxidation method And a dioxane decomposition device for removal.

  Claim 6 constitutes the method invention of claim 1 as an apparatus invention.

  A seventh aspect of the present invention according to the sixth aspect is characterized in that the solid-liquid separation device is a membrane separation device. This is because the activated sludge concentration in the biological reaction tank can be maintained at a high concentration of 10000 mg / L to 30000 mg / L by using a membrane separation apparatus as a solid-liquid separation apparatus after organic matter removal in the biological reaction tank. This is because the above-mentioned sludge conversion rate can be further reduced and the SS component can be reliably removed by the membrane separation device so that the SS component does not go into the dioxane decomposition apparatus.

  As described above, in the wastewater treatment method and apparatus according to the present invention, 1,4-dioxane can be efficiently decomposed and removed from actual wastewater such as sewage wastewater or leachate wastewater containing 1,4-dioxane.

  Hereinafter, preferred embodiments of a wastewater treatment method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a wastewater treatment apparatus according to a first embodiment of the present invention, which is an example provided with a dioxane decomposition apparatus by an accelerated oxidation method.

  As shown in FIG. 1, the wastewater treatment apparatus 10 is mainly composed of a biological reaction tank 12, a sedimentation tank 14, a sand filtration tank 16, a conditioning tank 18, and a dioxane decomposition apparatus 20 using an accelerated oxidation method. The

  Raw water of actual waste water containing 1,4-dioxane (hereinafter referred to as “waste water”) such as sewage treatment waste water or leachate from a landfill site flows into the biological reaction tank 12 from the raw water pipe 22. A diffuser tube 24 is provided at the bottom of the biological reaction tank 12, and air is supplied from the blower 26 and aerated into the wastewater in the biological reaction tank 12. Thereby, biologically treatable components such as organic matter contained in the wastewater are biologically treated with activated sludge under aerobic conditions.

  The wastewater treated in the biological reaction tank 12 flows through the water supply pipe 28 and is sequentially sent to the precipitation tank 14 and the sand filtration tank 16, and the activated sludge that flows along with the wastewater in the precipitation tank 14 and the sand filtration tank 16. The SS component such as is solid-liquid separated. A part of the SS component such as activated sludge settled in the settling tank 14 is returned to the biological reaction tank 12 through the sludge return pipe 30, and the remaining SS component is extracted from the extraction pipe 32 as surplus sludge. On the other hand, the separated water from which fine SS has been separated by sand filtration in the sand filtration tank 16 flows through the water supply pipe 28 and is sent to the adjustment tank 18. In the adjustment tank 18, for example, the pH of the separated water is adjusted, and then flows through the water supply pipe 28 and is supplied to the dioxane decomposition apparatus 20 of the accelerated oxidation method.

  The dioxane decomposition apparatus 20 of the accelerated oxidation method is mainly composed of an accelerated oxidation tank 34, an ozone gas injection pipe 36 that injects ozone gas into the accelerated oxidation tank 34, and an ultraviolet lamp 38 provided in the accelerated oxidation tank 34. The Then, 1,4-dioxane in the separated water sent from the adjustment tank 18 to the dioxane decomposition apparatus 20 is oxidatively decomposed by an accelerated oxidation method using both ozone gas and ultraviolet irradiation. This decomposition of 1,4-dioxane is not a direct decomposition by ozone, but 1,4-dioxane is decomposed by OH radicals generated during the self-decomposition process of ozone. Waste ozone gas used for oxidative decomposition is returned to the biological reaction tank 12 through a waste ozone return pipe 40. In the accelerated oxidation method, in addition to the combination of ozone gas and ultraviolet irradiation, a combination of ozone gas and hydrogen peroxide, or a combination of ozone gas, ultraviolet irradiation and hydrogen peroxide can be used.

  Next, the operation of the wastewater treatment apparatus 10 according to the first embodiment of the present invention formed as described above will be described.

  The waste water that has flowed into the biological reaction tank 12 from the raw water pipe 22 is first decomposed and removed by using the activated sludge in the biological reaction tank 12 for organic substances that coexist in the waste water. Thereby, the decomposition performance of 1,4-dioxane by the accelerated oxidation method can be improved. This is because if the concentration of organic substances coexisting in the wastewater is high, the ability to decompose 1,4-dioxane by the accelerated oxidation method becomes extremely poor. The reason for this is that the decomposition of 1,4-dioxane by the accelerated oxidation method is considered to be mainly decomposed by OH radicals. However, if the concentration of coexisting organic substances is high, OH radicals are consumed for the decomposition of organic substances. It is considered that the decomposition of dioxane does not proceed sufficiently.

  Fig. 2 shows the relationship between the organic matter concentration (mg / L) relative to the 1,4-dioxane concentration (mg / L) in the wastewater and the decomposition rate of 1,4-dioxane. As the TOC concentration (total organic carbon content). The decomposition rate in FIG. 2 shows the value of A (1 / min) when approximating the equation of T = A × X + B, where Y is the 1,4-dioxane concentration and X is the treatment time. .

  As can be seen from FIG. 2, when the TOC concentration with respect to the 1,4-dioxane concentration is 2 or more, 1,4-dioxane is hardly decomposed. When the TOC concentration relative to the 1,4-dioxane concentration is gradually decreased from 2, the decomposition rate increases, and the decomposition rate increases rapidly from around 1.5. Therefore, it is preferable to decompose and remove organic substances in the wastewater in the biological reaction tank 12 until the TOC concentration relative to the 1,4-dioxane concentration becomes 1.5 or less. Decreasing the TOC concentration to 1,4-dioxane concentration to 1 increases the decomposition rate to about 1.0, so organic substances are decomposed in the biological reaction tank 12 until the TOC concentration to 1,4-dioxane concentration becomes 1 or less. More preferably, it is removed.

  In addition, as a characteristic of wastewater containing 1,4-dioxane, a large amount of polyethylene glycol-based organic substances coexist. This is because 1,4-dioxane is produced using ethylene glycol as a raw material, or detergents often have polyethylene glycol groups, and 1,4-dioxane is produced as a by-product in the polyethylene glycol reaction process. It is to be done.

  This polyethylene glycol-based organic matter is easily decomposed by biological treatment with activated sludge, and the conversion rate from organic matter (BOD) to suspended solids (SS) (sludge conversion rate) is less than 10% and has a merit. is there.

  Therefore, it is important to first decompose and remove the organic substances coexisting in the waste water as a pretreatment for decomposing and removing with the dioxane decomposing apparatus 20, but as a method for decomposing and removing the organic substances, biological treatment using the biological reaction tank 12 is suitable. This is because when the organic matter in the wastewater is not ethylene glycol, the sludge conversion rate by biological treatment is as high as 70%, but the organic matter in the wastewater is ethylene glycol like wastewater containing 1,4-dioxane. In the case of wastewater mainly composed of water, it can be easily decomposed and removed by biological treatment, and the sludge conversion rate is as low as 10% or less, and the generation of excess sludge can be remarkably reduced. Here, the sludge conversion rate of 10% means that SS of organic matter is generated from 100 mg / L to 10 mg / L.

  Next, the wastewater treated in the biological reaction tank 12 is solid-liquid separated in the precipitation tank 14 and the sand filtration tank 16, and the separated water separated in the solid-liquid separation is treated in the dioxane decomposition apparatus 20. This is because the degradation performance decreases when SS components such as activated sludge in the biological reaction tank 12 are present during the accelerated oxidation method, and the degradation performance of 1,4-dioxane decreases due to the adverse effect on ultraviolet irradiation. To do. Therefore, in the present invention, by utilizing the fact that 1,4-dioxane is a substance having high water solubility, 1,4-dioxane is converted into separated water by solid-liquid separation of the wastewater treated in the biological reaction tank 12. In addition, SS components that are decomposition inhibitors in the dioxane decomposition apparatus 20 can be removed. Thereby, 1,4-dioxane can be efficiently decomposed and removed from actual wastewater such as sewage wastewater or leachate wastewater containing 1,4-dioxane.

  Moreover, since waste ozone gas discharged from the accelerated oxidation tank 34 is blown into the biological reaction tank 12, sludge in the biological reaction tank 12 can be decomposed with waste ozone gas to reduce the amount of excess sludge generated, and the burden of solid-liquid separation. Can also be reduced. Moreover, the sludge conversion rate which is the conversion rate of organic substance to SS can be further reduced by blowing waste ozone gas into the biological reaction tank 12.

  FIG. 3 is a schematic configuration diagram of the wastewater treatment apparatus 50 according to the second embodiment of the present invention, which is the same as the first embodiment in that the dioxane decomposition apparatus 20 by the accelerated oxidation method is provided. A membrane separation device 42 is provided instead of the precipitation tank 14 and the sand filtration tank 16 as a solid-liquid separation means. Part of the sludge separated into solid and liquid by the membrane separator 42 is returned to the biological reaction tank 12 through the sludge return pipe 30, and the remaining sludge is extracted from the extraction pipe 32 as excess sludge.

  The same members and devices as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. The same applies to the description of the third to fourth embodiments.

  According to the embodiment of the wastewater treatment apparatus 50 of the second embodiment of the present invention, the activated sludge concentration in the biological reaction tank 12 can be reduced by using the membrane separation apparatus 42 for solid-liquid separation after organic matter removal in the biological reaction tank 12. It can be maintained at a high concentration of 10,000 mg / L to 30000 mg / L. Thereby, since the organic substance decomposition | disassembly efficiency in the biological reaction tank 12 becomes large, the sludge conversion rate mentioned above can be improved further, and a sludge conversion rate can be reduced to 7% or less. Further, by performing solid-liquid separation with the membrane separation device 42, it is possible to ensure that the SS component does not go to the dioxane decomposition device 20, so that the decomposition performance of 1,4-dioxane in the dioxane decomposition device 20 can be improved. As the membrane of the membrane separation device 42, a microfiltration membrane or an ultrafiltration membrane can be suitably used, and an immersion flat membrane type membrane separation device or a rotary flat membrane type membrane separation device can be used. .

  FIG. 4 is a modification of the wastewater treatment apparatus 50 according to the second embodiment of the present invention, and is an integrated wastewater treatment apparatus 60 in which the biological reaction tank 12 and the membrane separation apparatus 42 are configured in the same tank.

  As shown in FIG. 4, the integrated wastewater treatment apparatus 60 includes a membrane separation activated sludge treatment apparatus 44, a regulation tank 18, and a dioxane decomposition apparatus 20 using an accelerated oxidation method. In the membrane separation activated sludge treatment apparatus 44, an immersion type membrane module 48 is provided in a membrane separation tank 46, and an air diffusing pipe 24 connected to the blower 26 is provided below the membrane module 48. As a result, biologically treatable components such as organic substances contained in the wastewater flowing into the membrane separation tank 46 from the raw water pipe 22 are biologically treated under activated aerobic conditions with activated sludge, and then the membrane module 48 The separated and solid-liquid separated water flows through the water supply pipe 28 and is supplied to the adjustment tank 18. Then, 1,4-dioxane in the wastewater sent from the adjustment tank 18 to the dioxane decomposition apparatus 20 is decomposed and removed by the accelerated oxidation method as described above. Further, the waste ozone gas is returned to the air diffusing pipe 24 of the biological reaction tank 12 through the waste ozone return pipe 40.

  In this way, by configuring the biological reaction tank 12 and the membrane separator 42 in the same tank, 1,4-dioxane can be efficiently removed from actual wastewater such as sewage wastewater or leachate wastewater containing 1,4-dioxane. In addition to being able to be disassembled and removed, the space of the apparatus can be saved.

  FIG. 5 is a schematic configuration diagram of a wastewater treatment apparatus 70 according to the third embodiment of the present invention, and a dioxane decomposition apparatus using the Fenton oxidation method instead of the dioxane decomposition apparatus 20 of the accelerated oxidation method in the first embodiment. 54 is provided. In the case of the Fenton oxidation method, even if a small SS component flows into the dioxane decomposition apparatus 54, there is little adverse effect. Therefore, the sand filtration tank 16 of FIG. 1 is not provided, but may be provided. When the sand filtration tank 16 is not provided, a precipitation tank 66 for solid-liquid separation may be provided after the dioxane decomposition apparatus 54. Other configurations are the same as those of the first embodiment.

The dioxane decomposition apparatus 54 of the Fenton oxidation method includes an oxidative decomposition tank 64 that is partitioned into three chambers, a PH adjustment tank 56, a metal catalyst addition tank 58, and a metal catalyst / hydrogen peroxide addition tank 62 in order from the upstream side. The The Fenton oxidation method is a method of oxidizing and decomposing 1,4-dioxane by adding hydrogen peroxide in the presence of a metal catalyst. After acidifying the pH of the separated water in the PH adjustment tank 56, the metal catalyst addition tank At 58, a metal catalyst is added. Further, the metal catalyst and hydrogen peroxide are added in the metal catalyst / hydrogen peroxide addition tank 62. The Fenton reaction is caused by the contact between the metal catalyst and hydrogen peroxide, and OH radicals are generated to oxidatively decompose 1,4-dioxane. As conditions for making the pH of the separated water acidic, the pH of the separated water during the reaction is preferably in the range of 2 to 4. As the metal catalyst, iron (Fe ²⁺ ) is preferably used, but is not particularly limited. As a method for adding the metal catalyst and hydrogen peroxide, it is preferable not to add all the necessary amounts at once, but to add them in stages in a divided manner. This is because hydrogen peroxide itself has the property of reacting with OH radicals, so if high-concentration hydrogen peroxide is added all at once in the presence of a metal catalyst, it will be peroxidized before it reacts with 1,4-dioxane. This is because it reacts with hydrogen itself and the decomposition efficiency of 1,4-dioxane is reduced.

  In the case of this Fenton oxidation method, the result of FIG. 2 is the same, and the ratio of the organic matter concentration (mg / L) to the 1,4-dioxane concentration (mg / L) contained in the wastewater is 1.5. It is preferable to decompose and remove organic substances in the wastewater in the biological reaction tank 12 so as to be below 1.0, preferably 1.0 or below.

  The wastewater treatment apparatus 70 of the third embodiment configured in this manner efficiently decomposes and removes 1,4-dioxane from actual wastewater such as sewage wastewater and leachate wastewater containing 1,4-dioxane. In addition, there is an advantage that the influence of SS is less likely to occur because ultraviolet irradiation is not performed unlike the accelerated oxidation method.

  FIG. 6 is a block diagram showing a schematic configuration of a wastewater treatment apparatus 80 according to the fourth embodiment of the present invention, and a membrane separation apparatus 42 instead of the sedimentation tank 14 after the biological reaction tank 12 in FIG. The other configuration is the same as that of FIG.

  According to the wastewater treatment apparatus of the fourth embodiment, 1,4-dioxane can be efficiently decomposed and removed from actual wastewater such as sewage wastewater or leachate wastewater containing 1,4-dioxane and promoted. Since the ultraviolet irradiation is not performed unlike the oxidation method, there is a merit that the influence of SS is hardly generated. Furthermore, the activated sludge concentration in the biological reaction tank 12 can be maintained at a high concentration of 10000 mg / L to 30000 mg / L by using the membrane separation device 42 as a solid-liquid separation device after organic matter removal in the biological reaction tank 12. Thus, the sludge conversion rate of 10% or less can be reduced to 7% or less. Further, by performing solid-liquid separation with the membrane separation device 42, the SS component can be reliably removed with the membrane separation device 42 so that the SS component is not present in the dioxane decomposition device 54, so that 1,4-dioxane in the dioxane decomposition device 54 is obtained. The decomposition performance of can be improved.

(Example 1)
In Example 1, the wastewater treatment apparatus 10 including the biological reaction tank 12 → the precipitation tank 14 → the sand filtration tank 16 → the adjustment tank 18 → the dioxane decomposition apparatus 20 of the accelerated oxidation method shown in FIG. A decomposition removal test of wastewater containing dioxane was conducted. In Example 1, waste ozone gas discharged from the accelerated oxidation tank 34 was not returned to the biological reaction tank.

  The test wastewater has a 1,4-dioxane concentration of 200 (mg / L) and a coexisting organic substance concentration of 2000 (mg / L) in TOC, and the main organic substance is an ethylene glycol organic substance. Moreover, the activated sludge density | concentration of the biological reaction tank was 3000 (mg / L), and the residence time of waste water was operated as 4 days. As a result, most of the organic substances in the wastewater were decomposed and removed by the activated sludge treatment in the biological reaction tank 12, and the organic substance concentration in the separated water after the sand filtration tank 16 was reduced to 80 (mg / L) by TOC. In the separated water, 1,4-dioxane remained more than half of the test wastewater.

Next, this separated water was treated with the dioxane decomposition apparatus 20 of the accelerated oxidation method. The conditions of the dioxane decomposition apparatus 20 were such that the ozone injection concentration into the separated water in the accelerated oxidation tank 34 was 16 (mg / L), and the ozone injection rate was 3 (mg-O ₃ / L / min). The ultraviolet lamp was 40W. As a result, the 1,4-dioxane concentration in the treated water after the dioxane decomposition apparatus 20 was 0.05 (mg / L), and most of the 1,4-dioxane could be decomposed and removed.

  On the other hand, in the comparative example in which the test wastewater was directly treated with the dioxane decomposition device 20 of the accelerated oxidation method, the 1,4-dioxane concentration in the treated water after the dioxane decomposition device 20 was almost decomposed at 198 (mg / L). could not.

(Example 2)
In Example 2, the wastewater treatment apparatus 50 including the biological reaction tank 12 → the membrane separation apparatus 42 → the adjustment tank 18 → the dioxane decomposition apparatus 20 of the accelerated oxidation method shown in FIG. The decomposition removal test was conducted. As the membrane separator 42, a rotary flat membrane device was used. The test wastewater is the same as in Example 1.

  As a result, in the case of Example 1, the activated sludge concentration that could be held in the biological reaction tank 12 was 3000 (mg / L), but the solid-liquid separation was performed by the membrane separation device 42 as in Example 2. Thus, the activated sludge concentration in the biological reaction tank 12 could be maintained at a high concentration of 10,000 to 30,000 (mg / L). Thereby, since the organic substance decomposition | disassembly performance in the biological reaction tank 12 improved, the organic substance density | concentration of the separation water after membrane separation was able to be reduced to 50 (mg / L) by TOC.

  Moreover, the sludge conversion rate from the organic matter to the SS component in the case of Example 1 was about 10%, but in Example 2, it could be lowered to 7%. As a result, the amount of excess sludge generated was reduced. Furthermore, in Example 2, the waste ozone gas discharged from the accelerated oxidation tank 34 was returned to the biological reaction tank 12, and the sludge was decomposed and solubilized with the waste ozone gas, so that the sludge conversion rate could be further reduced from 7%.

  Moreover, in Example 2, when the separated water was processed with the dioxane decomposition apparatus 20 of the accelerated oxidation method, the 1,4-dioxane of the treated water after the dioxane decomposition apparatus 20 was 0.02 (mg / L). This is considered to be due to the solid-liquid separation of the effluent water after the biological reaction tank 12 by the membrane separation device 42 and the complete removal of the SS component.

(Example 3)
In Example 3, 1,4-dioxane is used by using the wastewater treatment apparatus 70 including the biological reaction tank 12 → the precipitation tank 14 → the adjustment tank 18 → the dioxane decomposition apparatus 54 of the Fenton oxidation method → the precipitation tank 66 shown in FIG. The decomposition removal test of the wastewater containing was conducted. The test wastewater is the same as in Examples 1 and 2.

  As a result, since the sand filtration tank 16 was not provided, the organic matter concentration of the separated water after the settling tank 14 was 100 (mg / L) higher than that of Examples 1 and 2 in TOC.

  PH of this separated water was adjusted to 2 to 4 in the PH adjustment tank 56 of the dioxane decomposition apparatus 54 of the Fenton oxidation method, and iron was added in the metal catalyst addition tank 58 and stirred. Further, iron and hydrogen peroxide were added in the metal catalyst / hydrogen peroxide addition tank 62. The total amount of iron added was 1000 (mg / L), the amount of hydrogen peroxide added was 2000 (mg / L), and the reaction time was 60 minutes. As a result, 1,4-dioxane in the separated water could be reduced to 1 (mg / L).

  Further, in order to increase the decomposition efficiency of 1,4-dioxane, two-stage addition was performed in which the addition of iron and hydrogen peroxide was added in two stages. That is, after adding the first stage at an addition amount of iron (500 mg / L) and hydrogen peroxide of 1000 (mg / L) and reacting for 30 minutes, an additional iron addition amount (500 mg / L) Then, hydrogen peroxide was added at 1000 (mg / L) for the second stage and reacted for 30 minutes. The total amount of iron added, the amount of hydrogen peroxide added, and the reaction time in the first and second stages were the same as in the first stage addition. As a result, 1,4-dioxane could be reduced to 0.4 (mg / L).

  Further, four-stage addition was performed in which the addition of iron and hydrogen peroxide was added in four stages. That is, after adding the first stage at an addition amount of iron (250 mg / L) and hydrogen peroxide (500 mg / L) and reacting for 15 minutes, an addition amount of iron (250 mg / L) was further added. Then, hydrogen peroxide was added at 500 (mg / L) for the second stage and reacted for 15 minutes. Subsequently, after the third stage addition was performed with iron addition amount 250 (mg / L) and hydrogen peroxide 500 (mg / L) and reacted for 15 minutes, iron addition amount 250 (mg / L), Hydrogen peroxide was added at the fourth stage at 500 mg / L, and reacted for 15 minutes. The total addition amount of iron, the addition amount of hydrogen peroxide, and the reaction time in the first to fourth rounds were the same as in the first stage addition. As a result, 1,4-dioxane could be reduced to 0.1 (mg / L).

  As can be seen from this result, when 1,4-dioxane is decomposed by the Fenton oxidation method, the decomposition efficiency can be increased by adding the metal catalyst and hydrogen peroxide in multiple stages.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the waste water treatment apparatus which is the 1st Embodiment of this invention. Explanatory drawing which showed the relationship between the organic substance density | concentration with respect to the 1, 4- dioxane density | concentration in wastewater, and the decomposition rate of 1, 4- dioxane. The schematic block diagram of the waste water treatment apparatus which is the 2nd Embodiment of this invention. The schematic block diagram which showed the modification of the waste water treatment apparatus which is the 2nd Embodiment of this invention. The schematic block diagram of the waste water treatment apparatus which is the 3rd Embodiment of this invention. The schematic block diagram of the waste water treatment apparatus which is the 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 50, 60, 70, 80 ... Waste water treatment apparatus, 12 ... Biological reaction tank, 14 ... Precipitation tank, 16 ... Sand filtration tank, 18 ... Adjustment tank, 20 ... Dioxane decomposition apparatus of accelerated oxidation method, 22 ... Raw water pipe 24 ... Aeration pipe, 26 ... Blower, 28 ... Water pipe, 30 ... Sludge return pipe, 32 ... Drawer pipe, 34 ... Accelerated oxidation tank, 36 ... Ozone gas injection pipe, 38 ... UV lamp, 40 ... Waste ozone return pipe, 42 ... Membrane separation device, 44 ... Membrane separation activated sludge treatment device, 46 ... Membrane separation tank, 48 ... Membrane module, 54 ... Dioxane decomposition device of Fenton oxidation method, 56 ... PH adjustment tank, 58 ... Metal catalyst addition tank, 62 ... Metal catalyst / hydrogen peroxide addition tank, 64 ... oxidation decomposition tank, 66 ... precipitation tank

Claims (7)

In a wastewater treatment method in which 1,4-dioxane contained in wastewater is decomposed and removed in a dioxane decomposition step by an accelerated oxidation method or a Fenton oxidation method,
As a pretreatment of the dioxane decomposition step,
An organic matter removing step of decomposing and removing organic matter coexisting in the wastewater in a biological reaction tank;
A solid-liquid separation step for solid-liquid separation of the wastewater treated in the organic matter removal step,
A wastewater treatment method, wherein the separated water separated in the solid-liquid separation step is treated in the dioxane decomposition step.   The organic matter in the wastewater is removed in the organic matter removal step so that the ratio of the organic matter concentration (mg / L) to the 1,4-dioxane concentration (mg / L) contained in the wastewater is 1.5 or less. The wastewater treatment method according to claim 1, wherein the wastewater treatment method is performed by decomposition and removal.   The wastewater treatment method according to claim 1 or 2, wherein the wastewater contains a concentration of 1,4-dioxane of 10 mg / L or more.   The wastewater treatment method according to any one of claims 1 to 3, wherein when the dioxane decomposition step is performed by the accelerated oxidation method, waste ozone gas generated is blown into the biological reaction tank.   The wastewater treatment method according to any one of claims 1 to 3, wherein when the dioxane decomposition step is performed by the Fenton oxidation method, the metal catalyst and hydrogen peroxide are added in a plurality of stages. In wastewater treatment equipment that decomposes and removes 1,4-dioxane contained in wastewater,
A biological reaction tank for decomposing and removing organic substances coexisting in the waste water;
A solid-liquid separation device for solid-liquid separation of the wastewater treated in the biological reaction tank;
A dioxane decomposition apparatus that decomposes and removes 1,4-dioxane contained in separated water separated by the solid-liquid separation apparatus by an accelerated oxidation method or a Fenton oxidation method;
A wastewater treatment apparatus characterized by comprising:   The wastewater treatment apparatus according to claim 6, wherein the solid-liquid separation apparatus is a membrane separation apparatus.

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