JP5548633B2 - Method and apparatus for treating 1,4-dioxane-containing wastewater - Google Patents

Description

  The present invention relates to a method and apparatus for treating 1,4-dioxane-containing wastewater, and more particularly, 1,4-dioxane-containing wastewater that biologically treats 1,4-dioxane in wastewater with 1,4-dioxane-degrading bacteria. The present invention relates to a processing method and a processing apparatus.

  1,4-dioxane is generally used as a solvent and is often used as a solvent for paints and the like. It is also contained in detergents such as commercially available polyoxyalkyl ethers. For this reason, 1,4-dioxane is produced through factory wastewater of a manufacturing plant that manufactures 1,4-dioxane or a manufacturing plant that manufactures polyoxyalkyl ether, and domestic wastewater that uses a detergent containing polyoxyalkyl ether. It is discharged into sewage.

  However, since 1,4-dioxane is a water-soluble hardly decomposable substance, it can hardly be decomposed by biological treatment or solid-liquid separation treatment in a sewage treatment plant, and there is a concern about pollution to the water environment.

  On the other hand, 1,4-dioxane has been detected in a wide range in environmental pollution surveys of designated chemical substances conducted by the Environment Agency, and pollution in water environments such as rivers and lakes has been reported. An example in which 1,4-dioxane was detected from groundwater has also been reported.

  From such a background, with the amendment of the Water Supply Law in April 2004, the content of setting the regulated value of 1,4-dioxane to 0.05 mg / L as a drinking water standard was introduced. Furthermore, in April 2010, environmental standard values have been established, and a treatment technique for efficiently decomposing and removing 1,4-dioxane in wastewater is desired.

  Conventionally, as a method for decomposing and removing 1,4-dioxane in wastewater, an accelerated oxidation method in which ozone treatment is mainly used in combination with hydrogen peroxide treatment and ultraviolet treatment to promote the formation of OH radicals has been proposed (for example, Patent Documents 1 to 3). A Fenton oxidation method is also known in which hydrogen peroxide is added under a metal catalyst to form OH radicals.

  However, the accelerated oxidation method and the Fenton oxidation method disclosed in Patent Documents 1 to 3 have a problem that the power consumption and the chemical usage fee are large, and the running cost increases. For this reason, development of a biological treatment method capable of treatment at a low cost is demanded.

  Conventionally, biological treatment of 1,4-dioxane has been considered difficult, and there are very few detailed reports on biological treatment. Among them, the applicant of the present application proposed to improve the activity of microorganisms that decompose 1,4-dioxane (hereinafter referred to as “1,4-dioxane-degrading bacteria”) and apply it to wastewater treatment (patents). Reference 4).

JP 2001-029966 A JP 2001-121163 A JP 2000-202466 A JP 2008-306939 A

However, the applicant has found that there are the following two problems in specifically treating actual wastewater (for example, sewage) using 1,4-dioxane degrading bacteria. That is,
(1) In the case of synthetic wastewater containing only 1,4-dioxane, high decomposition efficiency can be obtained, but organic substances other than 1,4-dioxane are concentrated in the wastewater as in actual wastewater. When it contains, the decomposition efficiency of 1, 4- dioxane falls remarkably (problem of decomposition efficiency fall).
(2) When biologically degrading with a biological treatment apparatus having 1,4-dioxane degrading bacteria, aerobic conditions are required, and when air aeration is performed, a part of 1,4-dioxane in the wastewater is in the atmosphere. Is released into the atmosphere (problem of atmospheric release).

  The present invention has been made in view of such circumstances, and in the treatment of 1,4-dioxane-containing wastewater using 1,4-dioxane-degrading bacteria, 1,4-dioxane has been a conventional problem. It aims at providing the processing method and processing apparatus of a 1, 4- dioxane containing wastewater which can solve the problem of decomposition efficiency fall and atmospheric release.

  In order to achieve the above object, claim 1 of the present invention provides a wastewater treatment method containing 1,4-dioxane as one kind of organic matter, wherein the wastewater is aerated in a first biological treatment tank. A first biological treatment step for obtaining a primary treatment wastewater by bringing it into contact with an organic matter-degrading bacterium that biologically degrades organic matter other than 1,4-dioxane, and in the second biological treatment tank, the primary treatment wastewater is aerated by air The second biological treatment step for obtaining treated water by contacting with 1,4-dioxane degrading bacteria that degrade 1,4-dioxane, and the gas released from the wastewater by air aeration of the first biological treatment tank A recovery step for recovery and an introduction step of introducing all or part of the recovered recovery gas into the second biological treatment tank are provided.

  Here, examples of organic substances other than 1,4-dioxane include a BOD component and a COD component.

  According to the present invention, the wastewater containing 1,4-dioxane as one kind of organic matter is brought into contact with 1,4-dioxane degrading bacteria in the second biological treatment tank before being decomposed, so that the first biological treatment tank. The organic substances other than 1,4-dioxane in the wastewater were reduced in advance. Thereby, since 1, 4- dioxane can be dominant over other bacteria in a 2nd biological treatment tank, the decomposition | disassembly efficiency of 1, 4- dioxane decomposing bacteria can be improved notably.

  In this case, the organic substance concentration other than 1,4-dioxane in the wastewater after the treatment of the first biological treatment tank is preferably 250 mg / L or less, and more preferably 100 mg / L or less. Moreover, as DO concentration in the 1st biological treatment tank by air aeration, the range of 1.5-6.0 mg / L is preferable, and the range of 2.0-5.0 mg / L is more preferable. The DO concentration in the second biological treatment tank by air aeration is preferably in the range of 2.0 to 6.0 mg / L, and more preferably in the range of 3.0 to 5.0 mg / L.

  Further, since the gas having a high 1,4-dioxane concentration released from wastewater by air aeration in the first biological treatment tank is recovered and introduced into the second biological treatment tank, 1,4 in the wastewater. -It can be decomposed without releasing dioxane to the atmosphere. In this case, in the second biological treatment tank, 1,4-dioxane can be decomposed with high decomposition efficiency, and the concentration of 1,4-dioxane in the tank can always be kept at a low level. The amount of 1,4-dioxane in the gas released by aeration can be significantly reduced.

  Further, by treating the recovered gas in the second biological treatment tank, a special decomposition apparatus for decomposing 1,4-dioxane in the recovered gas is not necessary. By the way, when 1,4-dioxane is decomposed physicochemically, decomposition waste liquid is generated, and this treatment needs to be performed.

  In the treatment method of the present invention, it is preferable that in the introduction step, the recovered gas is introduced as an air aeration gas for the second biological treatment tank. This is one mode of a preferable introduction method for decomposing the recovered gas in the second biological treatment tank. Thereby, the air supply equipment for carrying out air aeration of the primary treatment wastewater of a 2nd biological treatment tank can be abbreviate | omitted.

  In the treatment method of the present invention, it is preferable that in the introduction step, the recovered gas is scrubbed and the scrubbing water is introduced into the second biological treatment tank. This is another aspect of the preferable introduction method for decomposing the recovered gas in the second biological treatment tank. Thereby, 1,4-dioxane in the gas released from the first biological treatment tank can be reliably absorbed into the scrubbing water and introduced into the second biological treatment tank.

  In the treatment method of the present invention, in the introduction step, the recovered gas is scrubbed, a part of the scrubbing treated water is returned to the first biological treatment tank, and the rest is introduced into the second biological treatment tank. Is preferred. This is another aspect of the preferable introduction method for decomposing the recovered gas in the second biological treatment tank. Thereby, the 1, 4- dioxane load in a 2nd biological treatment tank can be prevented from becoming large too much.

  In the treatment method of the present invention, it is preferable to use treated water in the second biological treatment tank as water for the scrubbing treatment. Thereby, a water-saving process can be performed.

  In order to achieve the object, claim 6 of the present invention is a wastewater treatment apparatus containing 1,4-dioxane as one kind of organic matter, and includes a first aeration means for aerating the wastewater with air. A first biological treatment tank that has at least an organic matter-degrading bacterium that biologically degrades organic matter other than 1,4-dioxane, contacts the organic matter-degrading bacterium while aerating the wastewater with air, and air the primary treatment wastewater. A first aeration means for aeration and at least a 1,4-dioxane-decomposing bacterium for decomposing the 1,4-dioxane; and the 1,4-dioxane-decomposing bacterium while aerating the primary treatment wastewater with air A second biological treatment tank to be brought into contact; a recovery means for recovering the gas released from the wastewater by air aeration of the first biological treatment tank; and a part or all of the recovered gas from the second biological treatment tank. And introducing means for introducing into the treatment tank, characterized by comprising a.

  According to the sixth aspect of the present invention, the present invention is configured as an apparatus, thereby solving the problems of degradation of 1,4-dioxane decomposition efficiency and atmospheric emission, which have been the conventional problems.

  In the treatment apparatus of the present invention, it is preferable that the recovery means is a lid member that forms a head space having a sealed structure above the liquid surface of the first and second biological treatment tanks. Thus, by making the 1st and 2nd biological treatment tank into a confidential sealed structure, it can collect so that the gas emitted from the 1st and 2nd biological treatment tank may not leak to the atmosphere.

  In the processing apparatus of the present invention, the introduction means is a pipe that connects the recovery means and the second aeration means, and an air blower that is provided in the pipe and that sends the recovered gas recovered by the recovery means to the second aeration means. And a fan. Thereby, the gas discharge | released from the 1st biological treatment tank can be utilized as gas for air aeration of a 2nd biological treatment tank.

  In the treatment apparatus of the present invention, the introduction means receives a scrubbing device provided above the first biological treatment tank for scrubbing the recovered gas, and the second biological treatment by receiving the scrubbing water subjected to the scrubbing treatment. And a bowl-shaped member to be sent to the tank. Thereby, 1,4-dioxane in the gas released from the first biological treatment tank can be absorbed into the scrubbing water and introduced into the second biological treatment tank.

  In the processing apparatus of the present invention, the introduction means includes a scrubbing device provided above the liquid level of the second biological treatment tank in the head space, and a recovery collected from the first biological treatment tank to the head space. It is preferable to include a moving means for moving the gas above the liquid level of the second biological treatment tank. Thereby, the introduction means for absorbing 1,4-dioxane in the gas released from the first biological treatment tank into the second biological treatment tank by being absorbed by the scrubbing water can be simplified.

  According to the present invention, in the treatment of 1,4-dioxane-containing wastewater using 1,4-dioxane-decomposing bacteria, the conventional problems of degradation of 1,4-dioxane degradation efficiency and atmospheric release are solved. can do.

Sectional drawing explaining 1st Embodiment of the processing apparatus of the 1, 4- dioxane containing wastewater of this invention. Sectional drawing explaining 2nd Embodiment of the processing apparatus of the 1, 4- dioxane containing wastewater of this invention. Sectional drawing explaining the modification 1 of 2nd Embodiment Sectional drawing explaining the modification 2 of 2nd Embodiment Explanatory drawing of the manufacturing step of the entrapping immobilization support containing 1,4-dioxane degrading bacteria The figure which shows the removal rate from the wastewater of the 1, 4- dioxane containing gas by air aeration

  Hereinafter, preferred embodiments of a treatment method and a treatment apparatus for 1,4-dioxane-containing wastewater according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
The 1,4-dioxane-containing wastewater treatment apparatus 10 shown in FIG. 1 mainly includes a first biological treatment tank 12 that treats wastewater containing 1,4-dioxane as one kind of organic matter to obtain primary treatment wastewater. A second biological treatment tank 14 for treating the primary treatment wastewater to obtain treated water; and a recovery means 16 for collecting gas released from the wastewater by air aeration of the first and second biological treatment tanks 12 and 14; And introducing means 18 for introducing all or part of the recovered gas into the second biological treatment tank 14.

  The first and second biological treatment tanks 12 and 14 are partitioned by a partition plate 20 that is erected, and a raw water pipe 22 for waste water is connected to the first biological treatment tank 12. As a result, when the first biological treatment tank 12 is filled with the wastewater supplied from the raw water pipe 22, the wastewater gets over the partition plate 20 and overflows to the second biological treatment tank 14. In addition, a trough 24 is provided on the opposite side of the first biological treatment tank 12 above the second biological treatment tank 14, and treated water treated in the second biological treatment tank 14 flows out into the trough 24.

  In addition, in FIG. 1, although comprised as 1 tank which divided the 1st and 2nd biological treatment tanks 12 and 14 with the partition plate 20, the 1st and 2nd biological treatment tanks 12 and 14 are set as separate tanks, The primary treatment wastewater obtained in the first biological treatment tank 12 may be sent to the second biological treatment tank 14 by a liquid feed pump (not shown).

  A first aeration pipe 26 is provided at the bottom of the first biological treatment tank 12, and a first blower 28 is provided in the first aeration pipe 26. As a result, the wastewater that has flowed into the first biological treatment tank 12 is aerated and brought into an aerobic state. Moreover, in the 1st biological treatment tank 12, it has at least the organic substance decomposition microbe which biologically decomposes | disassembles organic substances other than 1, 4- dioxane. As the organic matter-decomposing bacteria, aerobic bacteria usually used for oxidative degradation of BOD and COD can be used, for example, activated sludge from a sewage treatment plant. When the waste water is sewage, the organic matter degrading bacteria are contained as floating sludge in the waste water supplied to the first biological treatment tank 12 via the raw water pipe 22, so that it is not necessary to add activated sludge in particular. Good. Or you may throw into the 1st biological treatment tank 12 as a support | carrier which included or adhered the activated sludge to the fixed material. Furthermore, a fixed bed may be provided in the first biological treatment tank 12, and activated sludge may be attached to the fixed bed as a biofilm.

  Similarly, a second aeration pipe 30 is provided at the bottom of the second biological treatment tank 14, and a second blower 32 is provided in the second aeration pipe 30. As a result, the primary treatment wastewater that has flowed into the second biological treatment tank 14 from the first biological treatment tank 12 is aerated and brought into an aerobic state.

  Further, the second biological treatment tank 14 has at least a 1,4-dioxane-degrading bacterium that decomposes 1,4-dioxane, and the 1,4-dioxane-degrading bacterium is 1,4-dioxane in an aerobic state. Decomposes dioxane. Here, “having at least 1,4-dioxane-degrading bacteria” means to avoid the misunderstanding that only 1,4-dioxane-degrading bacteria exist, and other bacteria may coexist.

  As seed sludge containing 1,4-dioxane degrading bacteria, soil of a factory that handles 1,4-dioxane (for example, a manufacturing factory that manufactures 1,4-dioxane or a manufacturing factory that manufactures polyoxyalkyl ether), or its Sludge from a wastewater treatment plant that treats factory wastewater can be used. However, even if seed sludge is put into the second biological treatment tank 14 as it is, the number of 1,4-dioxane-degrading bacteria is low, and sufficient activity cannot be exhibited. The explanation of the isolation and culture of 1,4-dioxane will be described later.

  The first biological treatment tank 12 is provided with a first lid member 16A (collection means) for collecting gas released from the wastewater by aeration of the wastewater with the first aeration pipe 26. Similarly, the second biological treatment tank 14 has a second lid member 16B (collection means) for collecting gas released from the primary treatment wastewater by aeration of the primary treatment wastewater with the second aeration pipe 30. ) Is provided. As a result, the first head space 12A is formed above the liquid level of the first biological treatment tank 12, and the second head space 12B is formed above the liquid level of the second biological treatment tank 14.

  In addition, an overflow port 34 is formed between the portion where the side portions of the first and second lid members 16A and 16B are adjacent to the partition plate 20, and the wastewater overflows, and the second biological treatment is performed. A treated water discharge port 36 for discharging treated water to the trough 24 is opened in the tank 14. The treated water discharge port 36 is formed below the liquid level of the second biological treatment tank 14 and is sealed with treated water accumulated in the trough 24. Therefore, the first and second head spaces 12A and 12B have a sealed structure in which the recovered gas does not leak to the outside by the water-sealed structure that seals the first lid member 16A, the second lid member 16B, and the treated water discharge port 36. Formed. Thereby, the gas discharged from the waste water or the primary treatment waste water by the air aeration in the first and second biological treatment tanks 12 and 14 is not leaked into the atmosphere, and is discharged to the first and second head spaces 12A and 12B. To be recovered.

  In addition, introduction means 18 for introducing the recovered gas recovered in the first head space 12 </ b> A into the second biological treatment tank 14 is provided. The introduction means 18 includes a first air pipe 40 extending from the first lid member 16 </ b> A through the buffer tank 38 to the suction port side of the second blower 32, and the first air pipe 40 includes a first blower fan. 42 is provided. As a result, the collected gas accumulated in the first head space 12A is sent to the second blower 32 via the buffer tank 38 and aerated from the second aeration pipe 30 into the primary treatment wastewater. The buffer tank 38 is provided with a check valve 44 so that air can be sucked from the atmosphere when the pressure in the buffer tank 38 is negative.

  A second air pipe 46 extends from the second lid member 16B, the tip of the second air pipe 46 is opened to the atmosphere, and a second blower fan 48 is provided in the second air pipe 46. Further, the second head space 12B is provided with a second sprinkling pipe 50, a pipe 52 is extended from the second sprinkling pipe 50, and the tip of the pipe 52 is immersed in treated water in the trough 24. Connected to pump 54. Thereby, the treated water accumulated in the trough 24 is sent to the second sprinkling pipe 50 by the submersible pump 54 and sprinkled as scrubbing water toward the liquid surface of the second biological treatment tank 14.

  As a result, the collected gas collected in the second head space 12B is absorbed by the scrubbing process using the water sprayed from the second water spray pipe 50. Then, the scrubbing water that has absorbed the recovered gas pours onto the liquid surface of the second biological treatment tank 14. In this case, as will be described later, since the 1,4-dioxane concentration in the gas released from the primary treatment wastewater by the air aeration in the second biological treatment tank 14 is low, the air is exhausted from the second air pipe 46 to the atmosphere. Since the amount of 1,4-dioxane to be used is extremely small, it is possible to omit the second watering pipe 50.

  In the present embodiment, the treated water from the second biological treatment tank 14 is used as the scrubbing water from the second sprinkling pipe 50, but tap water or industrial water can also be used.

  Next, the processing method for removing 1, 4- dioxane from wastewater using the processing apparatus 10 of the 1, 4- dioxane containing waste water comprised as mentioned above is demonstrated.

  Waste water supplied from the raw water pipe 22 to the first biological treatment tank 12 comes into contact with organic matter-degrading bacteria under aerobic conditions by air aeration through the first aeration pipe 26. Thereby, organic substances (for example, COD component, BOD component) other than 1,4-dioxane among the organic substances contained in the wastewater are oxidatively decomposed. Therefore, primary treatment wastewater in which organic substances other than 1,4-dioxane are reduced is obtained. The primary treatment wastewater flows over the partition plate 20 and is sent to the second biological treatment tank 14.

  In the second biological treatment tank 14, the primary treatment wastewater comes into contact with 1,4-dioxane degrading bacteria in a low concentration state, so that 1,4-dioxane can be decomposed with high decomposition efficiency. This is because, when processing the hardly degradable 1,4-dioxane and the easily decomposable organic matter in the same tank, the organic matter-degrading bacteria that proliferate by decomposing the easily degradable organic matter will proliferate, 1,4-Dioxane-degrading bacteria are less likely to proliferate. As a result, the decomposition ability of 1,4-dioxane is suppressed, and the removal performance of 1,4-dioxane is lowered. Further, as described later, 1,4-dioxane-degrading bacteria also have a property of using organic substances other than 1,4-dioxane as a substrate (nutrient source). , 4-Dioxane-degrading bacteria are more likely to decompose easily decomposable organic matter than 1,4-dioxane.

  On the other hand, gas containing 1,4-dioxane is discharged from the wastewater by air aeration through the first aeration pipe 26 and is collected in the first head space 12A. 1,4-Dioxane is easily released from wastewater by air aeration, and the release rate of the amount of 1,4-dioxane is 30% or more, and about 70% in the case of a large amount. However, due to air pollution problems, the released gas cannot be released to the atmosphere as it is. Here, the release rate of 30% means that 30% of 1,4-dioxane in the wastewater before air aeration is released from the wastewater by air aeration.

  Therefore, in the first embodiment of the present invention, the recovered gas recovered in the first head space 12A is sent to the second blower 32 via the buffer tank 38 by the first blower fan 42, and the second aeration pipe 30 is supplied. Aeration as an air aeration gas. In this case, when the amount of air aerated from the second aeration pipe 30 is larger than the amount of air blown by the first blower fan 42 and the buffer tank 38 becomes negative pressure, the check valve opens and the atmosphere is replenished into the buffer tank. The

  1,4-Dioxane is water-soluble, and 1,4-dioxane is dissolved in the primary treatment wastewater by aeration of the recovered gas containing 1,4-dioxane. Thereby, in the 2nd biological treatment tank 14, since 1, 4- dioxane and 1, 4- dioxane decomposing bacteria in recovery gas contact, 1, 4 in the gas emitted from the 1st biological treatment tank 12 -Dioxane can be removed effectively.

  In this case, even in the second biological treatment tank 14, gas is released from the primary treatment wastewater by air aeration from the second aeration pipe 30, but the concentration of 1,4-dioxane contained in the gas is This is significantly lower than the 1,4-dioxane concentration in the gas released from the biological treatment tank 12.

  This is because the release rate of 1,4-dioxane released by air aeration is constant regardless of the 1,4-dioxane concentration in the wastewater, according to the knowledge obtained from experiments conducted by the present inventors. This is because if the 1,4-dioxane concentration in the wastewater is small, the amount of 1,4-dioxane released is reduced accordingly.

  That is, in the second biological treatment tank 14, 1,4-dioxane in the primary treatment wastewater is decomposed and removed by 1,4-dioxane degrading bacteria, and the concentration is reduced. Furthermore, in the present invention, by reducing the concentration of organic substances other than 1,4-dioxane in the first biological treatment tank 12, the decomposition efficiency of 1,4-dioxane in the second biological treatment tank is remarkably improved. be able to. Moreover, since 1,4-dioxane in the wastewater is transferred into the released gas by air aeration in the first biological treatment tank 12, 1,4-distillate in the wastewater that overflows the second biological treatment tank 14. Dioxane concentration level decreases. Thereby, since the 1, 4- dioxane density | concentration in the 2nd biological treatment tank 14 can be maintained at a low level (for example, 10 mg / L or less), in order to make the inside of the 2nd biological treatment tank 14 aerobic, primary treatment wastewater 1,4-dioxane concentration in the gas released from the primary treatment wastewater is reduced even if the air is aerated. Thereby, since the 1, 4- dioxane density | concentration in the 2nd biological treatment tank 14 can be maintained at a low level, the amount of 1, 4- dioxane released | emitted from primary treatment wastewater by air aeration as mentioned above There are few. The 1,4-dioxane concentration in the second biological treatment tank 14 is preferably maintained at 10 mg / L or less, preferably 5 mg / L or less.

  Further, since the gas released from the first biological treatment tank 12 is used as the air aeration gas in the second biological treatment tank 14, a special decomposition tank for decomposing 1,4-dioxane in the gas. There is no need to provide. As a result, the device configuration can be simplified and made compact.

<Isolation and culture of 1,4-dioxane>
Since 1,4-dioxane-degrading bacteria have a very low growth rate, it is necessary to prevent other microorganisms from being mixed and preferentially grow in the isolation process. In the culturing step, it is important to give an organic substance to the 1,4-dioxane-degrading bacterium in order to promote the growth of the isolated 1,4-dioxane-degrading bacterium. For this reason, the isolation process uses an inorganic medium containing only 1,4-dioxane as the organic substance, and the culture process uses an organic medium mainly containing an organic substance other than 1,4-dioxane.

  That is, in the isolation step, first, seed sludge containing 1,4-dioxane-decomposing bacteria (dioxane) is added to 100-500 mL of a medium in which 1,4-dioxane is added to an inorganic medium so as to have a concentration of 10-100 mg / L. About 500 to 20000 mg / L of sludge collected from the wastewater treatment process containing wastewater. The enrichment culture is preferably performed at 20 to 30 ° C. for about 1 to 3 months. The presence of 1,4-dioxane degrading bacteria can be confirmed by measuring a change in 1,4-dioxane concentration in the medium. It is preferable to end the enrichment culture when the rate of decrease in 1,4-dioxane concentration exceeds 50%. The concentration of 1,4-dioxane in the medium can be measured by a known method (Ami Akemi (1997) Environmental Chemistry vol.7 No1 p95-100).

  After completion of the enrichment culture, static culture is performed at a constant temperature of 20 to 35 ° C. in a plate medium in which 10 to 15% of agar is added to the inorganic medium. By confirming the formation of colonies after static culture, 1,4-dioxane-degrading bacteria can be isolated.

The inorganic substance constituting the inorganic medium is not particularly limited, but inorganic salts (for example, K ₂ HPO ₄ , (NH ₄ ) ₂ SO ₄ , MgSO ₄ .7H ₂ O, FeCl ₃ , CaCl ₂ , NaCl) are preferable. .

  Next, in culture, the 1,4-dioxane-degrading bacterium isolated as described above is cultured in an organic medium mainly composed of organic matter. As the organic substance, a CGY medium, specifically, an easily degradable organic substance such as peptone, meat extract, glycerin, cadmium, yeast extract and the like is preferable. The organic matter may include 1,4-dioxane. In the culture, the activity of 1,4-dioxane-degrading bacteria is the highest at about 27 ° C., so the culture temperature is preferably 27 ° C., and the water temperature is preferably about 15-35 ° C., more preferably 20-30 ° C. The culture time is preferably about 5 to 30 days.

  1,4-Dioxane-degrading bacteria are difficult to grow when excessively 1,4-dioxane is given while the number of bacteria is small, whereas 1,4-dioxane-degrading activity is not given when 1,4-dioxane is not given at all. Decreases. For this reason, it is preferable to give organic substances other than 1,4-dioxane at the initial stage of culture, and to give 1,4-dioxane in the middle and later stages of culture in which the number of 1,4-dioxane-degrading bacteria has increased to some extent. That is, organic substances other than 1,4-dioxane mainly function to promote the growth of 1,4-dioxane-degrading bacteria, and 1,4-dioxane mainly decomposes 1,4-dioxane-degrading bacteria. It functions to maintain or improve activity. The addition of 1,4-dioxane is preferably performed when the number of 1,4-dioxane-degrading bacteria is 1 × 10 4 cells / mL or more. The addition amount of 1,4-dioxane is 1 to 500 mg / L or more, preferably 10 to 200 mg / L or more with respect to the organic medium. This is because if 1,4-dioxane is less than 1 mg / L, the effect of restoring the degradation activity of 1,4-dioxane-degrading bacteria is reduced. In addition, when 1,4-dioxane is 200 mg / L or more, the decomposition activity does not change any more, and 1000 mg / L is equivalent to 200 mg / L. In addition, in order to discard the medium in a harmless state, it is necessary to make the 1,4-dioxane concentration in the medium as low as possible. For this reason, it is preferable to add 1,4-dioxane little by little according to the number of bacteria of 1,4-dioxane decomposing bacteria and the degree of activity. Note that 1,4-dioxane may be contained in the organic medium from the beginning of the culture. In this case, the content of 1,4-dioxane can be the same as described above.

  The cultured 1,4-dioxane-degrading bacterium can be used as it is by putting it into the second biological treatment tank as it is. It is preferable to use a material fixed to the material. As the immobilization method, 1,4-dioxane cultured in a hydrogel is comprehensively immobilized and fluidized in a tank (encapsulated immobilization carrier), and 1,4-dioxane cultured on the surface of the carrier material is adhered and fixed. There are a method of flowing in a tank (adhesion immobilization carrier), a method of fixing 1,4-dioxane cultured on a fixed bed, and the like.

  In addition, Pseudonocardia dioxanivorans has been reported as a 1,4-dioxane-degrading bacterium, which can be purchased through a distribution agency (ATCC: American Type Culture Collection) and used for degradation tests (1,4Dioxane biodegradation at low temperatures in Arctic groundwater samples Water Research, Volume 44, Issue 9, 2010, Pages 2894-2900).

[Second Embodiment]
FIG. 2 is a second embodiment of the apparatus for treating 1,4-dioxane-containing wastewater 100 according to the present invention. The same devices, means, and members as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 2, the second embodiment is different from the first embodiment in the introduction means 18 for introducing the gas generated in the first biological treatment tank 12 into the second biological treatment tank 14. That is, the recovered gas recovered in the first head space 12A is not introduced into the second biological treatment tank 14 as an air aeration gas, but the recovered gas is scrubbed and introduced into the second biological treatment tank 14. did.

  As shown in FIG. 2, in the second embodiment, the first lid member 16A and the second lid member 16B are integrated, and the first and second head spaces 12A and 12B are made one continuous space. The first sprinkling pipe 56 is also provided in the first head space 12A so that scrubbing can be performed. In this case, as shown in FIG. 2, it is preferable that the first sprinkler pipe 56 and the second sprinkler pipe 50 are configured as one continuous sprinkler pipe.

  Further, a bowl-shaped member 58 that receives scrubbing water is provided below the first water spray pipe 56, and the bowl-shaped member 58 is inclined so as to become lower from the first biological treatment tank 12 toward the second biological treatment tank 14. Provided. A plurality of bowl-shaped members 58 can be provided according to the size of the liquid surface of the first biological treatment tank 12.

  As a result, the gas with a high 1,4-dioxane concentration released from the wastewater by the air aeration of the first biological treatment tank 12 is scrubbed by the first sprinkling pipe 56, and the scrubbing treated water flows down the bowl-shaped member 58. To be supplied (introduced) to the second biological treatment tank. Therefore, 1,4-dioxane in the gas released from the first biological treatment tank 12 can be absorbed into the scrubbing water and introduced into the second biological treatment tank 14, so that 1,4-dioxane in the gas can be removed. It can be removed efficiently.

[Modification 1 of the second embodiment]
FIG. 3 shows a first modification of the second embodiment of the treatment apparatus 200 for 1,4-dioxane-containing wastewater of the present invention, in which the bowl-shaped member 58 is omitted from the second embodiment.

  According to the first modification, a part of the gas released by air aeration in the first biological treatment tank 12 and accumulated in the first head space 12A is absorbed by the scrubbing water by the scrubbing treatment from the first water spray pipe 56. Then, it pours onto the liquid surface of the first biological treatment tank 12. The remaining gas that has not been absorbed by the scrubbing water from the first water spray pipe 56 moves to the second head space 12 </ b> B by driving the second blower fan 48. In the second head space 12B, both the gas moved from the first head space 12A and the gas released by air aeration in the second biological treatment tank 14 are scrubbed water from the second sprinkling pipe 50. And scrubbing water pours into the liquid surface of the second biological treatment tank 14. Thereby, also in the case of the modification 1, while being able to show an effect comparable as 2nd Embodiment, an apparatus structure can be simplified.

[Modification 2 of the second embodiment]
FIG. 4 is a second modification of the second embodiment of the treatment apparatus 300 for 1,4-dioxane-containing wastewater of the present invention, and the first sprinkling pipe 56 and the bowl-shaped member 58 are modified from the second embodiment. Both are omitted.

  According to the second modification, all the gas released by air aeration in the first biological treatment tank 12 and accumulated in the first head space 12 </ b> A moves to the second head space 12 </ b> B by driving the second blower fan 48. To do. Then, both the gas that has moved from the first head space 12A and the gas that has been released by air aeration in the second biological treatment tank 14 are scrubbed with scrubbing water from the second water sprinkling pipe 50, and scrubbed water. Pours onto the liquid surface of the second biological treatment tank 14.

  Thereby, also in the case of the modification 2, while being able to show an effect comparable as 2nd Embodiment, an apparatus can be simplified further. Further, by omitting the first watering pipe 56, the pumping capacity for sucking up the treated water from the trough 24 can be reduced, and the motive energy can be reduced.

  In this embodiment, an example in which one first biological treatment tank 12 and one second biological treatment tank 14 are provided has been described. However, a plurality of first biological treatment tanks and a plurality of second biological treatment tanks are provided, and a multi-stage is provided. You may make it process.

[Example]
[Test A]
In test A, when the 1st biological treatment tank 12 which reduces organic substances other than 1, 4- dioxane in a wastewater was provided in the front | former stage of the 2nd biological treatment tank 14 which has 1, 4- dioxane decomposing bacteria (Example) The treatment efficiency of 1,4-dioxane was compared between 1) and when it was not provided (Comparative Example 1).

<Waste water used for testing>
The quality of waste water (raw water) subjected to the test is shown in Table 1.

(Remarks) TOC: Total organic carbon In Comparative Example 1, the waste water in Table 1 was directly treated in the second biological treatment tank 14 charged with a carrier in which 1,4-dioxane degrading bacteria were comprehensively immobilized.

  On the other hand, in Example 1, the second biological treatment tank similar to Comparative Example 1 is used for the primary treatment wastewater obtained by treating the wastewater in Table 1 with organic substances such as COD and BOD in the first biological treatment tank 12. 14 processed. In addition, the 1st and 2nd biological treatment tanks 12 and 14 in the test A used what reduced the processing apparatus demonstrated above for the test. Moreover, since the test A is a test for observing the influence of organic substances other than 1,4-dioxane in the wastewater, the gas recovery means 16 and the second biological treatment tank 14 of the first and second biological treatment tanks 12 and 14 are used. The recovered gas introduction means 18 is not used.

  That is, the effective reaction volume of the first biological treatment tank 12 is 1 L, and a flow meter is used so that the amount of air aerated from the first aeration pipe 26 into the wastewater is constant at 0.8 L / min. And controlled. The quality of the primary treatment wastewater obtained by treating the wastewater in the first biological treatment tank 12 is as shown in Table 1 above. In addition to the fact that the concentration of organic substances in COD, BOD, and TOC has decreased from the wastewater, the concentration of 1,4-dioxane has also decreased in the primary treatment wastewater. The main reason for this is the release from wastewater by air aeration. It is a decrease due to what has been done.

<Production of entrapping immobilization carrier containing 1,4-dioxane degrading bacteria>
What entrapped and immobilized 1, 4- dioxane degrading bacteria by the following method was used.

  FIG. 5 is a diagram for explaining the flow of the manufacturing method of the entrapping immobilization carrier. As shown in FIG. 5, first, an immobilization material such as a prepolymer material and a culture solution of 1,4-dioxane-degrading bacteria are mixed, and the pH is adjusted to near neutral (6.5 to 8.5). Prepare the mixed solution. In this example, a polyethylene glycol-based material was used as the immobilization material.

Next, a polymerization initiator (potassium persulfate is used in this embodiment) is added to this mixed solution and stirred, and then immediately gelled (polymerized) into a sheet shape or a block shape. The polymerization temperature is preferably 15 to 40 ° C, and more preferably 20 to 30 ° C. The polymerization time is preferably 1 to 60 minutes, and more preferably 10 to 60 minutes. Then, the gelled sheet or block was cut into a predetermined size (in the present example, approximately 3 mm square cube shape), thereby obtaining a entrapping immobilization support. The initial immobilized concentration of 1,4-dioxane degrading bacteria was 1 × 10 ⁷ cells / mL · carrier.

And the obtained entrapping immobilization support | carrier was made into the water temperature of 25 degreeC using the inorganic wastewater containing 1, 4- dioxane, 1, 4- dioxane load shall be 1-8 kg- (Dioxan) / m < ³ > * support | carrier / day, Continuous culture was performed for about 1 month. As a result, the 1,4-dioxane decomposition activity per carrier became 7.1 kg- (Dioxan) / m ³ · carrier, and this entrapping immobilization carrier was used in Test A.

  In addition, the manufacturing method of the entrapping immobilization carrier is not limited to the above-described method, and a tube forming method, a dropping granulation method, or the like can also be employed.

<Conditions for the second biological treatment tank>
As the second biological treatment tank 14, an effective reaction volume of 1 L is used, and the entrapped immobilization support in which the 1,4-dioxane decomposition activity is enhanced by accumulating and culturing the inside of the tank as described above is 100 mL (packed) The rate was 10% by volume).

The water temperature of the primary treatment wastewater was adjusted with sodium hydroxide and hydrochloric acid so that the water jacket was kept at a constant condition at 25 ° C. and the pH in the tank was in the range of 7.0 to 8.0. Then, as described above, 10% of the entrapping immobilization carrier was filled. Further, as can be seen from Table 2, since the 1,4-dioxane concentration before treatment is different between Comparative Example 1 and Example 1, in Comparative Example 1, HRT was 56 hours, in Example 1, HRT was 39 hours, In all cases, the operation was carried out at a load of 1,4-dioxane of 4 kg- (Dioxan) / m ³ . The amount of air aerated from the second aeration tube 30 into the primary treatment wastewater was controlled to be constant at 0.8 L / min using a flow meter.

  In Test A, both Comparative Example 1 and Example 1 were continuously operated for 6 weeks, and the treated water after the operation was sampled to examine the 1,4-dioxane concentration in the treated water. And the removal rate was computed from the 1, 4- dioxane density | concentration before a process and after a process.

<Test results>
The test results are shown in Table 2.

  As can be seen from the test results in Table 2, Comparative Example 1 in which wastewater was directly treated in the second biological treatment tank 14 without passing through the first biological treatment tank 12 had a low 1,4-dioxane removal rate of 49%. . In addition, although the air aeration amount of the 1st biological treatment tank 12 was increased twice, the 1, 4- dioxane removal rate rose only about 15%.

  On the other hand, by passing through the first biological treatment tank 12, organic substances other than 1,4-dioxane in wastewater are reduced to obtain primary treated water, and this primary treated water is used as the second biological treatment tank. In Example 1 treated with No. 14, the removal rate of 1,4-dioxane was as high as 99.8%.

  From the comparison with Comparative Example 1 and Example 1, 1,4-dioxane in the wastewater can be sufficiently treated with 1,4-dioxane-decomposing bacteria even if wastewater with high organic matter concentration is directly treated in the second biological treatment tank 14. It was proved that it could not be decomposed and removed.

  As a result of investigating the cause, in the case of Comparative Example 1, aerobic microorganisms other than 1,4-dioxane-degrading bacteria grow in the tank of the second biological treatment tank 14 or on the surface of the entrapped immobilization support. It was. That is, it is considered that the main reason why the degradation activity was reduced was that 1,4-dioxane-degrading bacteria could not propagate dominantly in the tank. In addition, due to the growth of aerobic microorganisms other than 1,4-dioxane-degrading bacteria on the carrier surface, oxygen due to air aeration was not sufficiently distributed to 1,4-dioxane-degrading bacteria in the carrier, which was also considered as a major factor. Is done.

  By the way, as a result of operating the second biological treatment tank 14 under the same HRT and aeration conditions as when the entrapping immobilization support was introduced without introducing the entrapping immobilization support into the second biological treatment tank 14, , 4-Dioxane concentration decreased to 580 mg / L. From this, it can be seen that about 30% of 1,4-dioxane was released from the wastewater by air aeration.

[Test B]
In Test B, it was examined how the removal rate of 1,4-dioxane released by air aeration and removed from wastewater varies depending on the concentration of 1,4-dioxane in wastewater aerated with air.

  Test B uses the second biological treatment tank 14 described above, and is released when air is aerated at a constant condition of 0.75 L / min for six wastewaters with 1,4-dioxane concentration shown in Table 3 shown in Table 3. The 1,4-dioxane concentration in the medium was examined. However, the second biological treatment tank 14 was carried out without introducing the entrapping immobilization carrier. The residence time (HRT) was set at 12 hours.

  The 1,4-dioxane concentration in the wastewater subjected to the test is as follows.

Sample 1 (S-1) 2 mg / L
Sample 2 (S-2) ... 9 mg / L
Sample 3 (S-3) 75 mg / L
Sample 4 (S-4) ... 100mg / L
・ Sample 5 (S-5) ... 360 mg / L
・ Sample 6 (S-6): 500 mg / L
The result is shown in FIG. As can be seen from the results in FIG. 6, 20 to 40% (average of about 30%) of 1,4-dioxane in the wastewater is removed by air aeration regardless of the concentration of 1,4-dioxane in the wastewater. I understand that. Therefore, for example, in an actual apparatus-scale biological treatment tank containing 1,4-dioxane-degrading bacteria, when the 1,4-dioxane concentration in the tank is only reduced to 100 g / m ³ , 1 m ³ / day When the treatment is performed with the residence time, about 30 g of 1,4-dioxane is released into the atmosphere by air aeration.

On the other hand, if the 1,4-dioxane concentration in the tank can be lowered to 1 g / m ³ , processing at a residence time of 1 m ³ / day will result in about 0.3 g per day by air aeration. -Only dioxane is released, and the amount released can be significantly reduced.

  That is, in order to suppress the release of 1,4-dioxane due to air aeration, it is extremely important to reduce the concentration of 1,4-dioxane in the tank as much as possible. Before decomposing 1,4-dioxane with 1,4-dioxane degrading bacteria in the second biological treatment tank 14, organic substances other than 1,4-dioxane in the wastewater are reduced in the first biological treatment tank 12. It is important to keep

[Test C]
1st Embodiment (test 1) of the processing apparatus of the 1, 4- dioxane containing waste water demonstrated above, the modification (test 2) of 1st Embodiment, 2nd Embodiment (test 3), And the removal performance of 1, 4- dioxane was investigated about each of the modifications 1 and 2 (test 4) of 2nd Embodiment. In the test, waste water shown in Table 1 was used, and in Test C, all the means such as the recovery means 16 and the introduction means 18 were driven and tested.

(Test 1)
The first and second biological treatment tanks 12 and 14 having the same size and structure as described above, each having a volume of 1 L, were tested under the following conditions. That is, a biofilm of activated sludge (collected from a sewage treatment plant) adhering to the carrier is introduced into the first biological treatment tank 12 so that the apparent volume of the cylindrical plastic carrier having a size of 3 mm is 20%. Formed. Then, the wastewater in the first biological treatment tank 12 was aerated at 0.8 L / min to form an aerobic condition, and the wastewater and the biofilm were brought into contact with each other. The inflow rate of raw water was 0.6 L / day. The primary treatment wastewater treated in the first biological treatment tank 12 was sent to the second biological treatment tank 14.

  On the other hand, the gas (1,4-dioxane-containing gas) released from the wastewater by air aeration in the first biological treatment tank 12 is collected in the first head space 12A, and the first air pipe 40 and the first blower fan 42 are collected. Was sent to the second blower 32 via the 10 L buffer tank 38, and air was aerated from the second aeration pipe 30 into the primary treatment wastewater of the second biological treatment tank 14 at 0.9 L / min.

  In this test 1, the amount of 1,4-dioxane in the gas released to the first head space 12A by air aeration in the first biological treatment tank 12 was measured, and as a result, it was an extremely high value of 200 to 260 mg per day. It was. Therefore, when this invention is not used, this amount of 1,4-dioxane will be released.

  In Test 1, the scrubbing process from the second water spray pipe 50 provided in the second head space 12B was not performed.

  Adjustment operation was performed for one month under the conditions of the first and second biological treatment tanks 12 and 14, and then data was collected for about two weeks, and performance was evaluated from the average data.

  As a result, the 1,4-dioxane concentration in the treated water discharged from the second biological treatment tank 14 was 4.6 mg / L on average. This means that in the second biological treatment tank 14, 1,4-dioxane in the primary treatment wastewater and 1,4-dioxane in the recovered gas introduced as air aeration gas are good as 1,4-dioxane-degrading bacteria. It can be seen that it can be decomposed.

  Further, the concentration of 1,4-dioxane discharged into the second head space 12B and exhausted from the second air pipe 46 by air aeration in the second biological treatment tank 14 was measured. As a result, the daily exhaust amount of 1,4-dioxane exhausted was as small as 1 to 6 mg, and could be suppressed to an extremely low level.

  From the above results, by using the gas released from the wastewater by the air aeration of the first biological treatment tank 12 as the air aeration gas of the second biological treatment tank 14, the 1,4-dioxane in the wastewater is reliably removed. Prove that you can.

(Test 2) Modification of First Embodiment of FIG. 1 Test 2 is a case where scrubbing treatment was performed by sprinkling scrubbing water from the second water spray pipe 50 in addition to the conditions of test 1.

  As a result, the 1,4-dioxane concentration in the treated water discharged from the second biological treatment tank 14 was substantially the same as the result in the first embodiment. However, the amount of 1,4-dioxane exhausted from the second air pipe 46 was 0.6 to 3 mg, which was less than that in Test 1, and the effect of the scrubbing treatment was confirmed.

(Test 3)
The gas discharged from the wastewater by air aeration in the first biological treatment tank 12 and collected in the first head space 12A is scrubbed with scrubbing water from the first sprinkling pipe 56, and the scrubbing water is It is a case where it introduce | transduces into 2 biological treatment tank 14. FIG.

  As a result, the 1,4-dioxane concentration in the treated water discharged from the second biological treatment tank 14 was 3.7 mg / L on average, which was equivalent to Test 1. Further, the amount of 1,4-dioxane exhausted from the second air pipe 46 was 2 to 7 mg per day, which was equivalent to Test 1.

(Test 4)
Compared with Test 2, Test 4-1 in which the bowl-shaped member 58 is omitted from the second embodiment and Test 4-2 in which the first sprinkling pipe 56 is also omitted has a slight removal performance of 1,4-dioxane. Although it fell, it was possible to simplify the apparatus and reduce the power energy.

  10, 100, 200, 300 ... 1,4-dioxane-containing wastewater treatment device, 12 ... first biological treatment tank, 14 ... second biological treatment tank, 16 ... recovery means, 18 ... introduction means, 20 ... partition plate, 22 ... Raw water piping, 24 ... Trough, 26 ... 1st aeration pipe, 28 ... 1st blower, 30 ... 2nd aeration pipe, 32 ... 2nd blower, 34 ... Overflow port, 36 ... Treated water discharge port, 38 ... Buffer tank, 40 ... first air piping, 42 ... first sending fan, 44 ... check valve, 46 ... second air piping, 48 ... second sending fan, 50 ... second sprinkling pipe, 52 ... piping, 54 ... Submersible pump, 56 ... first sprinkling pipe, 58 ... bowl-shaped member

Claims (10)

In a method for treating wastewater containing 1,4-dioxane as one kind of organic matter,
In the first biological treatment tank, a first biological treatment step of obtaining primary treatment wastewater by contacting with organic matter-degrading bacteria that biologically degrade organic matter other than 1,4-dioxane while aerating the wastewater with air;
In a second biological treatment tank, a second biological treatment step of obtaining treated water by contacting the primary treatment wastewater with 1,4-dioxane-degrading bacteria that decomposes 1,4-dioxane while aerating with air;
A recovery step of recovering the gas released from the wastewater by air aeration of the first biological treatment tank;
An introduction step of introducing all or part of the recovered gas recovered into the second biological treatment tank;
A method for treating wastewater containing 1,4-dioxane, comprising:   2. The method for treating 1,4-dioxane-containing wastewater according to claim 1, wherein in the introduction step, the recovered gas is introduced as an air aeration gas for the second biological treatment tank.   The method for treating 1,4-dioxane-containing wastewater according to claim 1, wherein, in the introduction step, the recovered gas is scrubbed and the scrubbing treated water is introduced into the second biological treatment tank.   In the introduction step, the recovered gas is scrubbed, a part of the scrubbing water is returned to the first biological treatment tank, and the rest is introduced into the second biological treatment tank. The processing method of the 1, 4- dioxane containing waste water as described in any one of.   The method for treating 1,4-dioxane-containing wastewater according to claim 3 or 4, wherein treated water in the second biological treatment tank is used as water for the scrubbing treatment. In a wastewater treatment apparatus containing 1,4-dioxane as one kind of organic matter,
It has a first aeration means for aerating the wastewater with air and has at least an organic matter-decomposing bacterium that biologically decomposes organic matter other than the 1,4-dioxane, and contacts the organic matter-decomposing bacterium while aerating the wastewater with air. A first biological treatment tank,
The first treatment wastewater is provided with a second aeration means for aerating with air, and has at least a 1,4-dioxane-degrading bacterium for decomposing the 1,4-dioxane, and the first treatment wastewater is aerated with air. A second biological treatment tank in contact with 4-dioxane degrading bacteria;
Recovery means for recovering gas released from the wastewater by air aeration of the first biological treatment tank;
An apparatus for introducing 1,4-dioxane-containing wastewater, comprising: an introduction means for introducing all or part of the recovered gas into the second biological treatment tank.   The 1,4-dioxane-containing wastewater according to claim 6, wherein the recovery means is a lid member that forms a sealed head space above the liquid surface of the first and second biological treatment tanks. Treatment device. The introducing means includes
A pipe connecting the recovery means and the second aeration means;
The 1,4-dioxane containing wastewater of Claim 6 or 7 provided with the ventilation fan provided in the said piping and sending the collection | recovery gas collect | recovered by the said collection | recovery means to a said 2nd aeration means Treatment device. The introducing means includes
A scrubbing device provided above the first biological treatment tank for scrubbing the recovered gas;
A treatment apparatus for wastewater containing 1,4-dioxane according to claim 6 or 7, further comprising: a bowl-shaped member that receives the scrubbing water subjected to the scrubbing treatment and sends the scrubbing water to the second biological treatment tank. The introducing means includes
A scrubbing device provided above the liquid level of the second biological treatment tank in the head space;
The moving means for moving the recovered gas recovered from the first biological treatment tank to the head space above the liquid level of the second biological treatment tank, 4-Dioxane-containing wastewater treatment device.

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