JP5521592B2 - Method and apparatus for treating high concentration nitrogen-containing water - Google Patents

Description

The present invention performs stable and efficient biological treatment by efficiently removing ammonia in raw water when biological treatment is performed in a biological treatment tank using high-concentration nitrogen-containing water causing ammonia product inhibition as raw water. The present invention relates to a method and an apparatus.
The present invention is particularly effective in reducing ammonia inhibition in methane fermentation treatment.

In methane fermentation treatment using high-concentration nitrogen-containing water as raw water, there is a problem of product inhibition due to high-concentration ammonia contained in the raw water. Conventionally, in order to prevent this ammonia inhibition,
(1) Before raw water flows into the methane fermentation tank, nitrogen components such as protein are removed in advance.
(2) Dilute raw water.
(3) The raw water is aerated with the generated biogas and ammonia stripping is performed.
Etc. are adopted.

However, the above method (1) is ineffective in inhibiting ammonia of nitrogen components other than proteins; in some cases, it is difficult to separate proteins with garbage, etc .; cost adjustment such as pH adjustment, solid-liquid separation, etc. There is a problem.
In the method (2), dilution water is required, and the amount of treated water increases due to dilution, which causes problems such as an increase in the size and cost of the apparatus.
The method (3) is extremely inefficient because the ammonia stripping rate is slow at neutral pH.

  For these reasons, there is currently no method that can be satisfactorily satisfied as a method for preventing ammonia inhibition of high-concentration nitrogen-containing water.

  In addition, in Patent Document 1, after solid-liquid separation of the treatment liquid after methane fermentation with an ultrafiltration membrane, prior to reverse osmosis membrane treatment of the separation liquid, ammonia is prevented from remaining in the final product, For the purpose of preventing harmful deposits on reverse osmosis membranes, it is described that ammonia stripping is performed to remove carbon dioxide together with ammonia and discharge it out of the system. It does not reduce the concentration and is ineffective in preventing ammonia inhibition.

JP-T 2002-511832

  The present invention has been made in view of the above-described conventional situation, and efficiently removes ammonia in raw water when processing in a biological treatment tank using high-concentration nitrogen-containing water that causes ammonia product inhibition as raw water. An object of the present invention is to provide a method and apparatus for performing stable and efficient biological treatment.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention deammonia the ammonia in the biological treatment liquid by a degassing membrane and return it to the biological treatment tank, and also inject water into the extraction side of the degassing membrane. By suppressing the precipitation of ammonium hydrogen carbonate, the ammonia concentration in the liquid in the biological treatment tank is kept low to prevent ammonia inhibition, and the degassing membrane is also prevented from being clogged. It was found that biological treatment and deammonification treatment can be performed.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] When high-concentration nitrogen-containing water that causes ammonia product inhibition is treated in a biological treatment tank, the biological treatment liquid in the biological treatment tank is deammonized using a degassing membrane, A method for treating high-concentration nitrogen-containing water, which is returned to the biological treatment tank and injected into the extraction side of the degassing membrane to suppress precipitation of ammonium hydrogen carbonate.

[2] The method for treating high-concentration nitrogen-containing water according to [1], wherein the degassing membrane is immersed in the biological treatment tank.

[3] The method for treating high-concentration nitrogen-containing water according to [1] or [2], wherein water is intermittently injected into the extraction side of the degassing membrane.

[4] The method for treating high-concentration nitrogen-containing water according to any one of [1] to [3], wherein the biological treatment tank is a methane fermentation treatment tank.

[5] The method for treating high-concentration nitrogen-containing water according to any one of [1] to [4], wherein the biological treatment liquid to be deammoniated is heated to 40 to 80 ° C.

[6] In any one of [1] to [5], an ammonium hydrogen carbonate solution obtained by dissolving the gas extracted from the degassing membrane in water is poured into the extraction side of the degassing membrane. A method for treating high-concentration nitrogen-containing water.

[7] In a treatment apparatus for high-concentration nitrogen-containing water that includes a biological treatment tank that treats high-concentration nitrogen-containing water that causes ammonia product inhibition, a degassing membrane that deamminates the biological treatment liquid in the biological treatment tank; A high concentration comprising: means for returning the deammonia treatment liquid of the degassing membrane to the biological treatment tank; and means for suppressing the precipitation of ammonium bicarbonate by pouring water into the extraction side of the degassing membrane Nitrogen-containing water treatment equipment.

[8] The apparatus for treating high-concentration nitrogen-containing water according to [7], wherein the degassing membrane is immersed in the biological treatment tank.

[9] The processing apparatus for high-concentration nitrogen-containing water according to [7] or [8], wherein water is intermittently injected into the extraction side of the degassing membrane.

[10] The processing apparatus for high-concentration nitrogen-containing water according to any one of [7] to [9], wherein the biological treatment tank is a methane fermentation treatment tank.

[11] The apparatus for treating high-concentration nitrogen-containing water according to any one of [7] to [10], further comprising means for heating the biological treatment solution to be deammoniated to 40 to 80 ° C.

[12] In any one of [7] to [11], the gas absorbing means for dissolving the gas extracted by the degassing membrane in water, and the ammonium hydrogen carbonate solution obtained by the gas absorbing means are degassed. And a means for pouring water on the extraction side of the membrane.

  According to the present invention, the ammonia in the biological treatment liquid is deammoniad by the deaeration membrane and returned to the biological treatment tank, and water is poured into the extraction side of the deaeration membrane to suppress precipitation of ammonium hydrogen carbonate. The ammonia concentration of the liquid in the biological treatment tank is kept low to prevent ammonia inhibition, and the degassing membrane is also prevented from being clogged, so that stable and efficient biological treatment and deammonia treatment can be performed.

It is a systematic diagram which shows an example of embodiment of this invention. It is a systematic diagram which shows the experimental apparatus used in the experiment example.

  Hereinafter, embodiments of the method and apparatus for treating high-concentration nitrogen-containing water of the present invention will be described in detail.

  In the present invention, when high-concentration nitrogen-containing water that causes ammonia product inhibition is treated in a biological treatment tank, the biological treatment liquid is deammoniated using a degassing membrane, and the deammonification treatment liquid is treated as a biological treatment tank. By returning to, the ammonia concentration in the biological treatment tank is kept low, and water is poured into the extraction side of the degassing membrane to suppress the precipitation of ammonium hydrogen carbonate.

That is, ammonia in the biological treatment liquid exists as ammonium hydrogen carbonate, and this ammonium hydrogen carbonate (NH ₄ HCO ₃ ) is preferably extracted under reduced pressure using a degassing membrane, preferably under heating. As a result, it vaporizes as ammonia (NH ₄ ) and carbon dioxide (CO ₂ ) and permeates the deaeration membrane. For this reason, the biological treatment liquid can be deammoniated using a degassing membrane, and the ammonia concentration in the biological treatment tank can be kept low by returning the deammonification treatment liquid to the biological treatment tank.

  A portion of the ammonia and carbon dioxide that permeated through the deaeration membrane reacts with the water vapor that permeated through the deaeration membrane together with ammonia and carbon dioxide to generate ammonium hydrogen carbonate again.

In this case, for example, the vapor pressure of each of ammonium hydrogen carbonate and water vapor at 50 ° C. is 513 hPa for ammonium hydrogen carbonate and 123 hPa for water vapor. There is a concern about the clogging of the degassing film due to the deposition on the extraction side of the gas film.
In the present invention, water is poured into the extraction side of the degassing membrane, and ammonium bicarbonate is dissolved and pulled out, thereby preventing clogging due to precipitation of ammonium hydrogencarbonate on the degassing membrane surface, and the degassing membrane device. Long-term stable operation can be performed.

In the present invention, the ammonia concentration of high-concentration nitrogen-containing water that causes ammonia product inhibition varies depending on the type of treatment in the biological treatment tank. For example, in the case of methane fermentation treatment, it is usually 3000 mg / medium for medium temperature methane fermentation. It is said that there is no significant inhibition in NH ₄ -N concentration of 1000 mg / L or less in high temperature methane fermentation at L or less. Therefore, when the NH ₄ -N concentration of the liquid in the biological treatment tank exceeds this concentration, the present invention is applied to perform the deammonia treatment of the biological treatment liquid, whereby the NH in the liquid in the biological treatment tank is obtained. It is preferable to maintain the _4- N concentration below the upper limit.

  The degassing membrane used for the deammonia treatment of the biological treatment liquid is not particularly limited as long as it does not allow water to permeate and allows gas dissolved in water to permeate. For example, polypropylene, polydimethylsiloxane, polycarbonate -Polydimethylsiloxane block copolymer, polyvinylphenol-polydimethylsiloxane-polysulfone block copolymer, poly (4-methylpentene-1), poly (2,6-dimethylphenylene oxide), polytetrafluoroethylene, etc. Examples thereof include molecular films.

  Also, the form of the deaeration membrane is not particularly limited, and various types such as a flat membrane type, a spiral type, a hollow fiber internal pressure type, and a hollow fiber external pressure type can be used. In particular, a spiral membrane module or a hollow fiber membrane module is preferably used.

  In particular, the membrane used for the hollow fiber membrane module may be any membrane that is hydrophobic and can be molded into a hollow fiber shape, such as polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, poly-4-methylpentene, and the like. However, a polymer made of polyvinylidene fluoride or poly-4-methylpentene is particularly preferable. In order to further increase the hydrophobicity of these membranes, it is possible to form a silicone-based or fluororesin-based thin film on one or both of the inner and outer surfaces of the hollow fiber.

  On the other hand, the membrane used in the spiral membrane module is generally an asymmetric membrane or a composite membrane, but a composite membrane is particularly common. The composite membrane is composed of a porous support layer and a polymer homogeneous layer or a dense layer provided thereon. The porous support layer has sufficient rigidity to prevent mechanical deformation of the polymer homogeneous layer as a support layer of the polymer homogeneous layer that most affects the performance of the hydrophobic gas permeable membrane, and has sufficient gas. It is necessary to have transmission performance. In order to further increase the strength of the support layer, it is preferable to have a reinforcing layer such as polyester fiber or nonwoven fabric under the support layer.

  Examples of the polymer constituting the porous support layer include polyester, polyamide, polyolefin, polyacrylate, polymethacrylate, poly-4-fluoroethylene, polysulfone, and polycarbonate. Polysulfone or polypropylene is particularly preferable. is there.

  Specific examples of the homogeneous polymer layer formed on the porous support layer include polyorganosiloxane, cross-linked polyorganosiloxane, polyorganosiloxane / polycarbonate copolymer, polyorganosiloxane / polyphenylene copolymer. , Polyorganosiloxane / polystyrene copolymer, polytrimethylsilylpropyne, poly-4-methylpentene, and the like. Among these, cross-linked polydimethylsiloxane is most preferable because it has high mechanical strength and a large oxygen permeability coefficient.

  In such a composite film, a material in which the polymer homogeneous layer is mainly composed of the above-mentioned cross-linked polydimethylsiloxane is called a cross-linked silicone composite film. In general, the cross-linked silicone thin film formed on the surface forms an extremely dense film surface, so in addition to the hydrophobicity of the silicone itself, it has excellent characteristics that it can suppress the adsorption of dirt components. Yes. The silicone film can be further improved in hydrophobicity by forming a fluororesin ultra-thin film on its surface.

  The degassing membrane module is divided into a liquid phase chamber and a gas phase chamber by the degassing membrane as described above, and a liquid to be degassed is passed through the liquid phase chamber, and the gas phase chamber is decompressed with a vacuum pump ( By evacuating, the gas in the liquid flowing through the liquid phase chamber is allowed to pass through the degassing membrane and be transferred into the gas phase chamber. A small amount of water vapor also moves into the gas phase chamber together with the gas in the liquid.

  In the present invention, ammonium hydrogen carbonate (ammonia and carbon dioxide) transferred to the gas phase chamber is absorbed together with water vapor into a liquid having a lower ammonia concentration than the biological treatment liquid. This absorbing solution is appropriately discharged out of the system and processed by a biological treatment apparatus at the subsequent stage, or recovered and reused as fertilizer, but can be used as water to be poured into the deaeration membrane as described later.

On the other hand, the deammonia treatment liquid from the deaeration membrane module is returned to the biological treatment tank.
In the deammonia treatment by the degassing membrane module, the higher the temperature, the lower the pressure on the extraction side, and the thinner the boundary membrane, the faster the degassing membrane permeation rate of ammonium bicarbonate (ammonia and carbon dioxide). .
For this reason, the degree of decompression on the extraction side (gas phase chamber) of the degassing membrane module is −0.04 MPa or less, for example, about −0.04 to −0.09 MPa, and the residence time in the degassing membrane module is increased. Moreover, it is preferable in terms of the deammonization efficiency to heat the treatment temperature (the temperature of the biological treatment solution used for the deammonification treatment) to 40 to 80 ° C, preferably about 45 to 60 ° C. If this temperature is too low, the efficiency of ammonia permeation through the degassing membrane is poor. If it is too high, the heating cost is high and there is a problem of water evaporation, which is not preferable.

  In the present invention, in order to prevent clogging of the degassing membrane due to the deposition of ammonium hydrogen carbonate during the deammonia treatment by the degassing membrane, the extraction side of the degassing membrane, that is, the gas phase chamber of the degassing membrane module is used. Water is poured, ammonium hydrogen carbonate is dissolved and discharged from the gas phase chamber. This water injection is performed by injecting water from the side opposite to the suction side by the vacuum pump for depressurizing the degassing membrane, and discharging the water in which ammonium hydrogen carbonate is dissolved in the degassing membrane is a separately provided pump. Or a vacuum pump for reducing the pressure in the gas phase chamber.

  The water used for the water injection may be water having a lower ammonia concentration than the biological treatment liquid, and city water, industrial water, etc. can be used. However, an absorption liquid that absorbs ammonium hydrogen carbonate from the degassing membrane module ( An ammonium hydrogen carbonate solution) can also be used.

  If this injection is always performed, the deammonia efficiency by the deaeration membrane module is impaired, and therefore it is preferable to perform the injection intermittently. The water injection frequency and the water injection amount vary depending on the precipitation tendency of ammonium hydrogen carbonate in the deaeration membrane module, the amount of the deammonia treatment, the size of the deaeration membrane module, etc., but once every 20 minutes to 6 hours. It is preferable that the amount of water injected once is about 1/5 times to the equivalent volume of the gas side volume of the deaeration membrane module.

  In order to carry out the present invention, the biological treatment liquid in the biological treatment tank can be extracted and fed to the degassing membrane module for deammonia treatment, and the treatment liquid can be returned to the biological treatment tank again. By immersing the gas membrane module in the biological treatment tank and directly deammonizing the liquid in the biological treatment tank, the transfer of the liquid can be omitted, and the contact efficiency between the biological treatment liquid and the degassing membrane (Retention time in the degassing membrane) can be increased, which is preferable.

  In this case, as shown in FIG. 1, the degassing membrane module 2 is immersed in the biological treatment tank 1 having the stirrer 1A so that the liquid in the biological treatment tank 1 flows through the degassing membrane module 2. Alternatively, the liquid in the biological treatment tank 1 is in direct contact with the degassing membrane of the degassing membrane module 2, and the gas phase chamber side of the degassing membrane module 2 is sucked with the vacuum pump 3 to reduce the pressure. Is absorbed in the absorption liquid in the gas absorption tank (or gas-liquid contact tower) 4, and the absorption liquid in the gas absorption tank 4 is intermittently opened and closed by opening and closing the water injection valve 5. The method of pouring water can be adopted.

  The biological treatment tank to which the present invention is applied is not particularly limited, but the present invention is particularly preferably applied to a methane fermentation tank having a large problem of ammonia inhibition, and in particular, a temperature condition of 40 to 80 ° C. is adopted. It is preferable to apply to a high-temperature methane fermentation tank because heating during deammonia treatment becomes unnecessary.

  Hereinafter, the present invention will be described more specifically with reference to experimental examples, comparative experimental examples, examples, and comparative examples.

[Experimental Example 1]
Using the experimental apparatus shown in FIG. 2, a deaeration experiment of ammonium hydrogen carbonate-dissolved water was conducted.
As the deaeration membrane module 13, “Liqui-Cel 1.7 × 5.5 Mini Module (registered trademark)” manufactured by Celgard was used.

A solution of ammonium bicarbonate dissolved in pure water at a concentration of 23 g / L (NH ₄ —N concentration: 4090 mg / L) is placed in a beaker 11 and heated to 55 ° C., and the circulation pump 12 While circulating through the liquid phase chamber at 1 L / hr, the gas phase chamber side of the degassing membrane module 13 was decompressed to −0.08 MPa by the vacuum pump 14. The exhaust from the vacuum pump 14 was absorbed in 500 mL of pure water in the gas absorption bottle 15. Further, the water injection valve 16 is opened and closed, and the absorbent in the gas absorption bottle is introduced into the gas phase chamber of the degassing membrane 13 from the inlet on the side opposite to the decompression side (the suction side by the vacuum pump) of the gas phase chamber. Water was injected at a rate of 10 mL / time once every 90 minutes.
As a result, the NH ₄ —N concentration of the ammonium hydrogen carbonate solution in the beaker 11 decreased to 1960 mg / L after 20 hours.
The NH ₄ —N concentration of the absorption liquid in the gas absorption bottle 15 was 4,260 mg / L.

[Comparative Experiment Example 1]
In Experimental Example 1, a deaeration experiment was performed in the same manner except that the absorption liquid in the gas absorption bottle 15 was not injected. As a result, carbon dioxide was clogged due to clogging of the deaeration film 10 hours after the start of the experiment. The permeation of ammonium hydrogen and water vapor disappeared, and the decrease in the ammonium hydrogen carbonate concentration of the ammonium hydrogen carbonate solution in the beaker 11 was stopped. At this time, the NH ₄ —N concentration of the ammonium hydrogen carbonate solution in the beaker 11 was 3,010 mg / L.

[Example 1]
Using the apparatus of FIG. 1, methane fermentation treatment of high-concentration nitrogen-containing water was performed.
As the biological treatment tank 1, a 3L jar fermenter is used, and wastewater mainly composed of protein (COD _Cr : 51,000 mg / L, K-N (Kjeldahl nitrogen): 6,900 mg / L, crude protein 43,000 mg / L L) Methane fermentation treatment was performed.

As the degassing membrane module 2, the outer cylinder of “Liqui-Cel 1.7 × 5.5 Mini Module (registered trademark)” manufactured by Celgard Co., Ltd. was peeled off to expose the liquid phase chamber, and deaerated. The gas-phase chamber side of the membrane module 2 was maintained at a reduced pressure of −0.08 MPa by sucking with the vacuum pump 3. The exhaust from the vacuum pump 3 was passed through 500 mg / L of pure water in the gas absorption tank 4. Further, the absorption liquid in the gas absorption tank 4 is transferred to the gas phase chamber of the deaeration membrane module 2 by opening and closing the water injection valve 5 from the inlet on the side opposite to the suction side by the vacuum pump 3 every 60 minutes. Water was injected at a rate of 10 mL / time.
When the jar fermenter was heated to 55 ° C. and treated for a residence time of 30 days, COD _Cr of the treated water was 400 mg / L, NH ₄ -N was 1600 mg / L, and the generation of methane gas was also remarkable. There was no clogging of the degassing membrane.

[Comparative Example 1]
In Example 1, the treatment was performed under the conditions of a residence time of 30 days and a temperature of 30 ° C. except that the deaeration process using the deaeration membrane and the heating of the jar fermenter were not performed. _Cr was 28,000 mg / L, NH ₄ -N was 6,100 mg / L, and the amount of methane gas produced was negligible.
In Comparative Example 1, methane fermentation was inhibited by ammonia in the waste water.

DESCRIPTION OF SYMBOLS 1 Biological treatment tank 2 Deaeration membrane module 3 Vacuum pump 4 Gas absorption tower 5 Water injection valve 11 Beaker 12 Circulation pump 13 Deaeration membrane module 14 Vacuum pump 15 Gas absorption bottle 16 Water injection valve

Claims (12)

When processing high-concentration nitrogen-containing water that causes ammonia product inhibition in a biological treatment tank,
The biological treatment liquid in the biological treatment tank is deammonized using a degassing membrane, the deammonized treatment liquid is returned to the biological treatment tank, and water is poured into the extraction side of the degassing membrane to precipitate ammonium hydrogen carbonate. A method for treating high-concentration nitrogen-containing water, which comprises suppressing the concentration of nitrogen-containing water.   The method for treating high-concentration nitrogen-containing water according to claim 1, wherein the degassing membrane is immersed in the biological treatment tank.   The method for treating high-concentration nitrogen-containing water according to claim 1 or 2, wherein water is intermittently injected to the extraction side of the degassing membrane.   The method for treating high-concentration nitrogen-containing water according to any one of claims 1 to 3, wherein the biological treatment tank is a methane fermentation treatment tank.   The method for treating high-concentration nitrogen-containing water according to any one of claims 1 to 4, wherein the biological treatment liquid to be deammoniated is heated to 40 to 80 ° C.   6. The ammonium hydrogen carbonate solution obtained by dissolving the gas extracted from the degassing membrane in water is injected into the extraction side of the degassing membrane according to claim 1. A method for treating highly nitrogen-containing water. In a treatment apparatus for high-concentration nitrogen-containing water comprising a biological treatment tank that treats high-concentration nitrogen-containing water that causes ammonia product inhibition,
A degassing membrane for deammonizing the biological treatment liquid in the biological treatment tank, means for returning the deammonized treatment liquid of the degassing membrane to the biological treatment tank, and pouring water into the extraction side of the degassing membrane to add hydrogen carbonate And a high-concentration nitrogen-containing water treatment apparatus.   In Claim 7, The said deaeration film | membrane is immersed in the said biological treatment tank, The processing apparatus of the high concentration nitrogen containing water characterized by the above-mentioned.   The apparatus for treating high-concentration nitrogen-containing water according to claim 7 or 8, wherein water is intermittently injected into the extraction side of the degassing membrane.   The apparatus for treating high-concentration nitrogen-containing water according to any one of claims 7 to 9, wherein the biological treatment tank is a methane fermentation treatment tank.   The apparatus for treating high-concentration nitrogen-containing water according to any one of claims 7 to 10, further comprising means for heating the biological treatment liquid to be deammoniated to 40 to 80 ° C.   12. The gas absorbing means for dissolving the gas extracted by the degassing membrane in water and the ammonium hydrogen carbonate solution obtained by the gas absorbing means according to any one of claims 7 to 11 And a high-concentration nitrogen-containing water treatment device.

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