JP5246665B2 - Methane fermentation treatment apparatus and methane fermentation treatment method - Google Patents

Description

  The present invention relates to a methane fermentation treatment apparatus and a methane fermentation treatment method for methane fermentation treatment of organic substances containing a large amount of phosphorus, magnesium and nitrogen such as distilled liquor, garbage, food factory waste, etc. in distilled liquor and alcohol production processes About.

  Conventionally, as this type of methane fermentation treatment apparatus, as shown in FIG. 2, the digested sludge in the methane fermentation tank 51 is concentrated by the submerged membrane separation means 52 while circulating between the membrane separation tank 53. Some perform methane fermentation. The membrane separation means 52 is installed in the membrane separation tank 53, and the membrane separation tank 53 communicates with the methane fermentation tank 51. A solubilization tank 54 is installed in the preceding stage of the methane fermentation tank 51. Further, a biological treatment tank 55 for biologically treating the membrane permeate that has permeated through the separation membrane of the membrane separation means 52 is installed at the subsequent stage of the methane fermentation tank 51.

Between the membrane separation tank 53 and the biological treatment tank 55, a membrane permeate outlet piping 56 for transferring the membrane permeate from the membrane separation means 52 to the biological treatment tank 55 is provided.
According to this, the organic substance solubilized in the solubilization tank 54 is put into the methane fermentation tank 51 and subjected to methane fermentation treatment. Digested sludge in the methane fermentation tank 51 is solid-liquid separated by the membrane separation means 52 and concentrated. At this time, the membrane permeate that has passed through the separation membrane of the membrane separation means 52 is sucked by the suction pump 57, flows through the membrane permeate outlet piping 56, is sent to the biological treatment tank 55, and is biologically treated in the biological treatment tank 55. After that, it is discharged into rivers as treated water.

  When an organic substance having a high content of nitrogen and inorganic components such as phosphorus and magnesium is subjected to methane fermentation in the methane fermentation tank 51, magnesium ammonium phosphate (hereinafter abbreviated as MAP) is precipitated in the fermentation liquid containing SS. It becomes easy to do. In particular, the membrane permeate is higher in temperature than the outside air in the methane fermentation tank 51, but is gradually cooled by the outside air in the membrane permeate outlet piping 56, so that the MAP inorganic liquid is formed on the inner peripheral surface of the membrane permeate outlet piping 56. There is a problem that crystals tend to be generated, the inorganic crystals gradually grow, and the membrane permeate outlet piping 56 is blocked.

As a countermeasure against such a problem, in order to suppress the formation of MAP inorganic crystals, a large amount of a chemical such as iron salt is added to the methane fermentation tank 51 to remove phosphorus and adjust the pH.
Patent Document 1 below describes that a part of the digested sludge in the methane fermentation tank is drawn out, concentrated with a concentrator, and the concentrated separation liquid of the concentrator is discharged into sewers as treated water. Furthermore, when MAP crystals are precipitated in the concentrated separation liquid transfer pipe, tap water, industrial water, secondary sewage treatment water, etc. are introduced into the concentrated separation liquid to lower the concentration and suppress MAP precipitation. Is described.

JP-A-2005-199258

  However, in the conventional format shown in FIG. 2 above, there is a problem that the cost required for the addition of the chemical is high, or the pH in the methane fermentation tank 51 varies due to the addition of the chemical, and the inside of the methane fermentation tank 51 is optimal for methane fermentation. There is a problem that it is difficult to maintain a stable pH.

  Moreover, in what was shown in the said patent document 1, since the concentration separation liquid is only diluted and the density | concentration of ammonia, phosphorus, etc. contained in a concentration separation liquid is only lowered | hung, the effect which fully suppresses precipitation of MAP is obtained. It was difficult.

  The present invention provides a low-cost methane fermentation treatment apparatus and methane fermentation treatment capable of sufficiently suppressing precipitation of MAP in a membrane permeate outlet piping while maintaining a pH suitable for methane fermentation in a methane fermentation tank. It aims to provide a method.

In order to achieve the above object, the first invention is a methane fermentation treatment apparatus for performing a methane fermentation treatment while concentrating digested sludge in a methane fermentation tank with a membrane separation means,
A biological treatment means including a step of biologically treating the membrane permeate that has passed through the separation membrane of the membrane separation means in an aerobic state; a membrane permeate outlet piping for transferring the membrane permeate from the membrane separation means to the biological treatment means;
When transferring the membrane permeate from the membrane separation means to the biological treatment means, the biological treatment process liquid from the biological treatment means is injected into the membrane permeate outlet piping, and the membrane permeate flowing through the membrane permeate outlet pipe is And an injection means for diluting .

  According to this, the organic substance is subjected to methane fermentation treatment in the methane fermentation tank, and the digested sludge in the methane fermentation tank is solid-liquid separated by the membrane separation means and concentrated. At this time, the membrane permeate that has permeated the separation membrane of the membrane separation means flows through the membrane permeate outlet piping and is sent to the biological treatment means, where it is biologically treated in an aerobic state. The pH of the biological treatment process liquid of the biological treatment means thus biologically treated is lower than the pH of the liquid in the tank of the methane fermentation tank, and the biological treatment process liquid of the biological treatment means passes through the membrane by the injection means. By being injected into the liquid outlet pipe, the pH of the membrane permeate flowing through the membrane permeate outlet pipe is lowered than the pH of the liquid in the methane fermentation tank. Thereby, it can suppress that MAP precipitates on the inner peripheral surface of the membrane permeate outlet piping.

  Moreover, the sludge component (SS) in the tank of the biological treatment means is injected into the membrane permeate outlet piping by the injection means, so that the sludge component adheres to the inner peripheral surface of the membrane permeate outlet pipe, Precipitation of MAP on the inner peripheral surface of the membrane permeate outlet pipe can be further suppressed.

  As a result, the amount of chemicals such as iron salt (the amount used) can be significantly reduced, which can reduce the cost, and the pH within the methane fermentation tank can be easily optimized for methane fermentation. Can be maintained.

In the methane fermentation treatment apparatus according to the second aspect of the present invention, the biological treatment means has a first treatment unit that performs biological treatment in an aerobic state,
The injecting means injects the biological treatment process liquid of the first processing unit into the membrane permeate outlet piping.

  According to this, since microorganisms in the sludge take up soluble phosphorus components and further precipitate in the first processing section, the first processing section injects it into the membrane permeate discharge pipe from the first processing section. The concentration of the soluble phosphorus component contained in the biological treatment process liquid is reduced. As a result, the membrane permeate flowing in the membrane permeate outlet pipe is diluted with the biological treatment process liquid, and the concentration of the phosphorus component in the membrane permeate outlet pipe is lowered. Can be further suppressed.

In the methane fermentation treatment apparatus according to the third invention, the biological treatment means has a second treatment unit that performs biological treatment in an anaerobic state,
A transfer pipe for transferring the biological treatment process liquid of the first treatment unit to the second treatment unit is provided,
The injection means branches from the transfer pipe and injects the biological treatment process liquid into the membrane permeate discharge pipe.

  According to this, since nitrogen is removed in the second processing unit, the concentration of the nitrogen component contained in the biological treatment process liquid injected from the first processing unit into the membrane permeate outlet piping by the injecting means decreases. . As a result, the membrane permeate flowing in the membrane permeate outlet pipe is diluted by the biological treatment process liquid, and the concentration of the nitrogen component in the membrane permeate outlet pipe is lowered. Can be further suppressed.

The fourth invention is a methane fermentation treatment method in which methane fermentation treatment is performed while concentrating digested sludge in a methane fermentation tank with a membrane separation means,
The membrane permeate that has passed through the separation membrane of the membrane separation means is transferred from the membrane permeate outlet piping to the biological treatment means, and biological treatment is performed in an aerobic state in the biological treatment means ,
When transferring the membrane permeate from the membrane permeate outlet pipe to the biological treatment means, the biological treatment process liquid of the biological treatment means is injected into the membrane permeate outlet pipe and the membrane permeate flowing through the membrane permeate outlet pipe Is to dilute .

In the methane fermentation treatment method according to the fifth aspect of the present invention, the membrane permeate is biologically treated in an aerobic state in the first treatment part of the biological treatment means,
The biological treatment process liquid of the first treatment unit is injected into the membrane permeate outlet piping.

In the methane fermentation treatment method according to the sixth invention, the membrane permeate is biologically treated in an anaerobic state in the second treatment part of the biological treatment means,
While transferring the biological treatment process liquid of a 1st process part to a 2nd process part, the one part is inject | poured into membrane permeation | transmission liquid extraction piping.

  As described above, according to the present invention, it is possible to sufficiently suppress the precipitation of MAP in the membrane permeate discharge pipe at a low cost while maintaining the inside of the methane fermentation tank at a pH suitable for methane fermentation.

It is a figure of the methane fermentation processing apparatus in embodiment of this invention. It is a figure of the conventional methane fermentation processing apparatus.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
Reference numeral 11 denotes a methane fermentation treatment apparatus that performs digestion sludge in the methane fermentation tank 12 while being circulated between the methane fermentation tank 12 and solid-liquid separation by a submerged membrane separation means 13 to perform methane fermentation treatment. A solubilization tank 14 for solubilizing an organic material as a raw material is installed in the front stage of the methane fermentation tank 12, and a membrane permeate that has passed through the separation membrane 15 of the membrane separation means 13 in the rear stage of the methane fermentation tank 12. A biological treatment tank 16 (an example of a biological treatment means) for biologically treating the above is installed.

  The membrane separation means 13 is provided in a membrane separation tank 17 communicating with the methane fermentation tank 12, and a plurality of flat plate membrane cartridges arranged in parallel with a predetermined interval are arranged in the vertical direction. A flow path is formed between the membrane cartridges. Each membrane cartridge has a separation membrane 15 (filtration membrane) disposed on both sides of the filter plate.

  In the membrane separation tank 17, an air diffuser 18 for cleaning the surface of the separation membrane 15 by diffusing the biogas in the methane fermentation tank 12 from below the membrane separator 13 is provided. A blower device 20 is provided in the gas supply channel 19 for supplying the biogas in the methane fermentation tank 12 to the aeration means 18. The digested sludge in the methane fermentation tank 12 is circulated and stirred between the methane fermentation tank 12 and the membrane separation tank 17 by the air lift effect due to the diffusion from the diffusion means 18 in the membrane separation tank 17.

  The biological treatment tank 16 includes a nitrification tank 22 (an example of a first treatment unit) that performs biological treatment in an aerobic state and a denitrification tank 23 (an example of a second treatment unit) that performs biological treatment in an anaerobic state. Have. At the bottom of the nitrification tank 22, aeration means 24 for blowing out air is provided. A blower device 26 is provided in the air supply passage 25 that supplies air to the aeration means 24.

The nitrification tank 22 is installed at the subsequent stage of the denitrification tank 23, and is configured so that the liquid in the tank of the denitrification tank 23 overflows to the adjacent nitrification tank 22.
Between the membrane separation means 13 and the biological treatment tank 16, there is provided a membrane permeate discharge pipe 27 for transferring the membrane permeate that has permeated through the separation membrane 15 of the membrane separation means 13 from the membrane separation means 13 to the denitrification tank 23. It has been. One end of the membrane permeate outlet pipe 27 communicates with a permeate channel formed inside the membrane cartridge, and the other end communicates with the denitrification tank 23. The membrane permeate outlet pipe 27 is provided with a suction pump 28, and the membrane separation means 13 suctions and filters the digested sludge in the membrane separation tank 17 by the suction pump 28.

  The methane fermentation treatment apparatus 11 includes a transfer pipe 32 for transferring the liquid in the nitrification tank 22 (an example of biological treatment process liquid, activated sludge or excess sludge) to the denitrification tank 23, and the inside of the nitrification tank 22. An injection pipe 30 (an example of injection means) for injecting the liquid into the membrane permeate outlet pipe 27 is provided.

  One end of the transfer pipe 32 communicates with the bottom of the nitrification tank 22, and the other end communicates with the upper part of the denitrification tank 23. A circulation pump 31 is provided in the transfer pipe 32. The injection pipe 30 has one end branched from the middle of the transfer pipe 32, and the other end communicated with the membrane permeate discharge pipe 27 on the discharge side of the suction pump 28.

The pH in the solubilization tank 14, the pH in the methane fermentation tank 12, and the pH in the membrane permeate outlet pipe 27 are measured by pH meters 34 to 36, respectively.
Hereinafter, the operation of the above configuration will be described.

  The organic material solubilized in the solubilization tank 14 is put into the methane fermentation tank 12 and subjected to methane fermentation treatment. At this time, the biogas generated in the methane fermentation tank 12 is desulfurized in the desulfurization tower 37, stored in a gas holder, and used as an energy source.

  The digested sludge in the methane fermentation tank 12 is solid-liquid separated by the membrane separation means 13 and concentrated. At this time, the membrane permeate that has permeated the separation membrane 15 of the membrane separation means 13 is sucked by the suction pump 28, flows in the membrane permeate outlet pipe 27, is sent to the denitrification tank 23 of the biological treatment tank 16, and is removed. After denitrification in the nitrogen tank 23, it overflows from the denitrification tank 23 to the nitrification tank 22, is aerated in the nitrification tank 22, and is nitrified by biological treatment. Then, by driving the circulation pump 31, the liquid in the tank of the nitrification tank 22 (an example of a biological treatment process liquid) flows through the transfer pipe 32 and is transferred (returned) to the denitrification tank 23. The liquid in the tank circulates between the tanks 23 and a part of the liquid in the nitrification tank 22 is discharged from the nitrification tank 22 as treated water and discharged to a river or the like.

  At this time, the pH (for example, about pH 7) of the liquid (nitrification liquid) in the nitrification tank 22 is lower than the pH (for example, about pH 8) of the liquid (digested sludge) in the methane fermentation tank 12, and the circulation pump By driving 31, the liquid in the nitrification tank 22 is injected from the transfer pipe 32 through the injection pipe 30 into the membrane permeate outlet pipe 27 (for example, a flow rate equal to or greater than the membrane permeate flow rate). As a result, the pH of the membrane permeate flowing in the membrane permeate outlet pipe 27 is lower than the pH of the liquid in the tank of the methane fermentation tank 12, and MAP is deposited on the inner peripheral surface of the membrane permeate outlet pipe 27. Can be suppressed.

  Further, since nitrogen is removed in the denitrification tank 23, the concentration of nitrogen components contained in the liquid in the subsequent nitrification tank 22 is reduced, and further, microorganisms in the sludge in the nitrification tank 22 are soluble phosphorus. Incorporates the components and further precipitates some of them. As a result, the concentration of the nitrogen component and the concentration of the soluble phosphorus component contained in the tank liquid injected from the transfer pipe 32 through the injection pipe 30 into the membrane permeate discharge pipe 27 from the nitrification tank 22 are reduced. . By injecting the liquid in the tank in which the concentration of the nitrogen component and the concentration of the soluble phosphorus component are reduced from the injection pipe 30 into the membrane permeate outlet pipe 27 as described above, the membrane flowing in the membrane permeate outlet pipe 27 Since the permeate is diluted with the liquid in the tank and the concentration of the nitrogen component and the concentration of the soluble phosphorus component in the membrane permeate outlet pipe 27 are lowered, MAP is deposited on the inner peripheral surface of the membrane permeate outlet pipe 27. This can be further suppressed.

  Further, the sludge component (SS) in the nitrification tank 22 is injected into the membrane permeate outlet pipe 27 through the injection pipe 30, so that the sludge component adheres to the inner peripheral surface of the membrane permeate outlet pipe 27, For this reason, it can further suppress that MAP precipitates on the inner peripheral surface of the membrane permeate outlet pipe 27. The sludge component adhering to the inner peripheral surface of the membrane permeate outlet pipe 27 does not grow like a MAP crystal, and a certain amount of sludge component is present on the inner peripheral surface of the membrane permeate outlet pipe 27. If attached, the sludge component is less likely to adhere due to the flow in the membrane permeate outlet pipe 27. For this reason, the sludge component does not adhere until the membrane permeate outlet pipe 27 is closed.

  As a result, the amount of added chemicals such as salt iron (amount used) can be greatly reduced compared to the conventional case, so that the cost can be reduced and the inside of the methane fermentation tank 12 can be easily methane-free. The optimum pH for fermentation can be maintained.

  In addition, since a part of the liquid in the nitrification tank 22 can be returned to the denitrification tank 23 and injected into the membrane permeate outlet pipe 27 using a single circulation pump 31, the cost can be reduced. Can be planned.

  In the above embodiment, the other end of the injection pipe 30 is connected to the membrane permeate outlet piping 27 on the discharge side of the suction pump 28, but is connected to the membrane permeate outlet piping 27 on the suction side of the suction pump 28. It suffices to communicate with a place where precipitation of MAP becomes a problem.

  In the above embodiment, a part of the liquid in the nitrification tank 22 flowing through the transfer pipe 32 is injected from the injection pipe 30 to the membrane permeate outlet pipe 27 and the rest is returned to the denitrification tank 23. The liquid in the nitrification tank 22 flowing through the pipe 32 may be entirely injected from the injection pipe 30 into the membrane permeate discharge pipe 27 without returning to the denitrification tank 23. Further, a valve may be provided in the transfer pipe 32 or the injection pipe 30 to adjust the amount of liquid injected from the injection pipe 30 to the membrane permeate outlet pipe 27 and the amount of liquid returned from the transfer pipe 32 to the denitrification tank 23. .

  In the above embodiment, a flat membrane is used as the membrane separation means 13, but the membrane is not limited to a flat membrane. For example, a hollow fiber membrane or a ceramic tubular membrane may be used in addition to the flat membrane. Further, instead of the membrane separation tank 17, a pressure type membrane separation means for performing membrane separation by supplying digested sludge with a pressure pump may be used.

  In the above embodiment, the raw material is solubilized in the solubilization tank 14, and then the methane fermentation treatment is performed. However, in the case of a liquid or slurry raw material or an easily decomposable raw material, the solubilization tank 14 is used. The solubilization step can be omitted.

In the said embodiment, although the air lift effect by the aeration means 18 is utilized for the transfer of the digested sludge from the methane fermentation tank 12 to the membrane separation tank 17, you may transfer using a pump.
In the said embodiment, although the biological treatment tank 16 is equipped with two tanks, the nitrification tank 22 and the denitrification tank 23, it is not limited to this, It is provided with one tank or several tanks more than three tanks. Of course, other known biological treatments including an aeration process are naturally applicable.

DESCRIPTION OF SYMBOLS 11 Methane fermentation processing apparatus 12 Methane fermentation tank 13 Membrane separation means 15 Separation membrane 16 Biological treatment tank (biological treatment means)
22 Nitrification tank (first processing section)
23 Denitrification tank (second processing section)
27 Membrane permeate outlet piping 30 Injection piping (injection means)
32 Transfer piping

Claims (6)

A methane fermentation treatment apparatus for performing methane fermentation treatment while concentrating digested sludge in a methane fermentation tank with a membrane separation means,
A biological treatment means including a step of biologically treating the membrane permeate that has passed through the separation membrane of the membrane separation means in an aerobic state; a membrane permeate outlet piping for transferring the membrane permeate from the membrane separation means to the biological treatment means;
When transferring the membrane permeate from the membrane separation means to the biological treatment means, the biological treatment process liquid from the biological treatment means is injected into the membrane permeate outlet piping, and the membrane permeate flowing through the membrane permeate outlet pipe is A methane fermentation treatment apparatus comprising an injection means for diluting . The biological treatment means has a first processing unit that performs biological treatment in an aerobic state,
2. The methane fermentation treatment apparatus according to claim 1, wherein the injection means injects the biological treatment process liquid of the first treatment unit into the membrane permeate outlet piping. The biological treatment means has a second processing unit that performs biological treatment in an anaerobic state,
A transfer pipe for transferring the biological treatment process liquid of the first treatment unit to the second treatment unit is provided,
The methane fermentation treatment apparatus according to claim 2, wherein the injection means branches from the transfer pipe and injects the biological treatment process liquid into the membrane permeate discharge pipe. A methane fermentation treatment method in which methane fermentation treatment is performed while concentrating digested sludge in a methane fermentation tank with a membrane separation means,
The membrane permeate that has passed through the separation membrane of the membrane separation means is transferred from the membrane permeate outlet piping to the biological treatment means, and biological treatment is performed in an aerobic state in the biological treatment means ,
When transferring the membrane permeate from the membrane permeate outlet pipe to the biological treatment means, the biological treatment process liquid of the biological treatment means is injected into the membrane permeate outlet pipe and the membrane permeate flowing through the membrane permeate outlet pipe A method for methane fermentation treatment, which comprises diluting the methane. Biologically treating the membrane permeate in an aerobic state in the first treatment section of the biological treatment means,
The methane fermentation treatment method according to claim 4, wherein the biological treatment process liquid of the first treatment unit is injected into the membrane permeate outlet piping. Biologically treating the membrane permeate in an anaerobic state in the second treatment section of the biological treatment means,
The methane fermentation treatment method according to claim 5, wherein the biological treatment process liquid of the first treatment unit is transferred to the second treatment unit, and a part thereof is injected into the membrane permeate outlet piping.

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