JP2005046788A - Methane fermentation treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methane fermentation method by which the targeted quantity of the object to be treated can be treated in a short period of time by shortening a culture period of a microbial cell when the input of the object to be treated is increased when methane fermentation is started or restarted or during the methane fermentation and to provide a methane fermentation apparatus. <P>SOLUTION: The object which is to be treated and consists of organic waste or organic matter-containing waste water is thrown in a methane fermentation tank and is subjected to the methane fermentation and the treated object is withdrawn from the methane fermentation tank. When the input of the object to be treated is increased when the methane fermentation is started or restarted or during the methane fermentation, the microbial cell in seed sludge or a fermented liquid is thrown in a separation membrane concentration unit 20 and concentrated by a separation membrane 22 immersed in a concentration tank 21 to obtain a microbial cell-concentrated liquid 28 having high microbial cell concentration. The object to be treated is added to the obtained liquid 28. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for methane fermentation treatment of organic waste such as raw garbage, food processing residue, surplus sludge from activated sludge treatment, or wastewater containing organic matter.

  The methane fermentation treatment method for organic waste such as raw garbage, food processing residue, surplus sludge from activated sludge treatment, or wastewater containing organic matter is treated in a methane fermentation solution kept in an anaerobic state. An object to be treated is introduced, and organic substances are finally decomposed into methane gas and carbon dioxide by the action of various fungi in the fermentation broth.

  As a method for improving the processing efficiency in the above methane fermentation, it is known to increase the concentration of bacteria by using a separation membrane or the like during normal operation. In a septic tank that has a plurality of treatment chambers that decompose the components of wastewater by action in the septic tank body, this septic tank separates wastewater from the upstream processing chamber into solid and liquid and supplies permeate to the downstream processing chamber. A configuration including a membrane separation device that returns the concentrated liquid to the upstream processing chamber is disclosed.

  Further, in Patent Document 2, a separation membrane is installed at the upper part of a reaction tank that performs activated sludge treatment, and an aeration apparatus that generates fine bubbles is installed at the lower part of the reaction tank. In the meantime, a membrane separation activated sludge treatment device is disclosed, in which a bubble coalescence device is formed by coalescing fine bubbles into enlarged bubbles.

  Furthermore, in Patent Document 3, an air diffuser is installed at the lower part of the membrane module as a treatment plant wastewater treatment device that can prevent the membrane surface from being clogged by the sludge separated by filtration or the channel between the membrane elements. There is disclosed a water treatment plant wastewater treatment apparatus in which a submerged membrane separation apparatus is disposed in a circulation zone formed in an upper area of the immersion tank, and a sedimentation zone having a predetermined water depth is formed in a lower area of the immersion tank.

  On the other hand, when starting up a new methane fermentation tank, seed sludge or fermentation liquid containing bacteria that decompose organic substances in the material to be treated is obtained separately, and this seed sludge or fermentation liquid is put into the methane fermentation tank. After that, a method of obtaining a desired predetermined biogas generation amount or treated water quality by gradually acclimatizing useful bacteria while gradually accustoming to the object to be treated has been performed.

In addition, when increasing the input load from the methane fermentation tank operating with a constant organic substance load amount until the target input load amount of the object to be processed is reached, or when restarting the methane fermentation tank, A method of gradually increasing the input load amount and shifting to a stable operation of the target input load amount while accustoming the useful bacteria group has been conventionally performed.
JP-A-6-71274 JP 2003-53368 A JP 2002-191946 A

  As described above, when a new methane fermentation tank is started up or restarted, the input load is reached from the methane fermentation tank operating at a constant organic substance load until the target input load of the workpiece is reached. In general, a long acclimatization period is required in order to increase the amount. When a large load is applied to the object to be treated with a small number of cells, the organic matter is solubilized and decomposed into an organic acid, and this organic acid accumulates. This is because the pH of the fermentation broth is reduced to a so-called rancid state and the methane fermentation treatment system fails.

  For example, when a new methane fermentation tank using seed sludge as described above is launched, the seed sludge is collected from a processing facility that is processing a component different from the object to be treated. There are many cases to do. Therefore, since the concentration of bacteria suitable for methane fermentation treatment of the material to be treated is low in this seed sludge, it is necessary to increase the number of bacteria and to obtain the biogas generation amount and treated water quality as designed. Alternatively, a period for acclimatizing the fermentation broth is required.

  Therefore, in the acclimatization period, it is common to gradually increase the load from an input load that is lower than the design processing amount. Therefore, it takes a very long time to reach the planned amount processing amount. There was a problem of becoming.

  However, in any of the above-described conventional techniques, the shortening of the acclimatization period has not been studied. For example, in the method of the above-mentioned JP-A-6-71274, although it is disclosed that the outflow of bacteria is prevented by membrane separation during normal operation and the cell concentration is increased, the methane fermenter is newly started up In addition, there is no disclosure of a processing method in the case where the operation is performed while increasing the input load. In addition, if the bacterial cell concentration is increased while constantly returning bacteria on the separation membrane during normal operation, clogging of the separation membrane is likely to proceed, and the frequency of membrane cleaning and replacement increases, making it impossible to operate efficiently. There's a problem.

  Moreover, although the apparatus structure using a separation membrane is disclosed by Unexamined-Japanese-Patent No. 2003-53368 and Unexamined-Japanese-Patent No. 2002-191946, the shortening of a habituation period is not examined.

  The present invention has been made in view of the above-mentioned problems of the prior art, and provides a methane fermentation treatment method capable of shortening the acclimatization period of seed sludge or fermentation liquor and processing a target throughput in a short period of time. The purpose is to do.

In order to achieve the above object, the methane fermentation treatment method of the present invention is a methane fermentation treatment method in which an object to be treated consisting of organic waste or waste water containing organic matter is put into a methane fermentation tank and methane fermentation is performed to take out. ,
At the start of methane fermentation, at the time of restart, or when increasing the input load of the processing object during operation, a bacterial concentrate that has increased the bacterial cell concentration by concentrating the bacterial cells in the seed sludge or fermentation broth It adds to the said processed material, The said processed material is added to the said microbe concentration liquid, It is characterized by the above-mentioned.

  According to the treatment method of the present invention, at the start of methane fermentation, that is, at the start-up of a new methane fermentation tank, the bacterial cells in the seed sludge are concentrated to increase the bacterial cell concentration, and then this concentrated solution is treated. The acclimatization period can be shortened by starting to increase the input load while gradually adding things. Also, when increasing the input load during restart or during operation, after increasing the concentration of cells in the stopped methane fermentation liquid to increase the concentration of cells, add the material to be treated while gradually adding it. By starting to increase the load, the acclimatization period can also be shortened.

  Furthermore, since the above-described concentration operation can be performed in a short time, an increase in the input load can be started quickly. Further, since it is not necessary to concentrate the bacteria after starting to increase the input load, problems such as clogging of the separation membrane caused by the continuous concentration of the bacteria, such as the method described in JP-A-6-71274 described above. No efficient operation is possible.

  In said method, it is preferable to concentrate the said microbial cell by centrifugation or membrane separation. Moreover, in said method, it is preferable to concentrate the said microbial cell so that the said microbial cell density | concentration may be 5,000-100,000 mg / L in a sludge density | concentration. According to this, a sufficient number of bacteria can be secured with a short concentration time, and the acclimatization period can be shortened efficiently.

  On the other hand, the methane fermentation treatment apparatus of the present invention is a methane fermentation of the treatment object supply means for introducing the treatment object consisting of organic waste or waste water containing organic substance into the methane fermentation tank, and the treatment object. A methane fermentation tank, a digestion solution extraction means for taking out the digestion solution after the methane fermentation, and a cell concentration means for concentrating the cells in the seed sludge or the fermentation solution to increase the cell concentration The fungus body concentration means is provided outside the methane fermentation tank, or is arranged so as to be able to be taken in and out of the methane fermentation tank.

  According to the treatment apparatus of the present invention, the bacterial cell concentration means is provided outside the methane fermentation tank, or is disposed so as to be able to be taken in and out of the methane fermentation tank, so there is no need to constantly concentrate the bacteria. Further, problems such as clogging of the membrane caused by always using the separation membrane can be prevented.

  In the processing apparatus, it is preferable that the bacterial cell concentration means is a centrifugal separator or a membrane separator. Moreover, it is preferable that the said microbial cell concentration means is comprised so that the microbial cell density | concentration in the said seed sludge or fermentation liquid may be 5,000-100,000 mg / L in a sludge density | concentration. According to this, a sufficient number of bacteria can be secured with a short concentration time, and the acclimatization period can be shortened efficiently.

  According to the present invention, in the methane fermentation treatment of organic waste such as surplus sludge such as raw garbage, food processing residue, activated sludge treatment, etc., by concentrating the bacterial cells in the seed sludge or fermentation broth in advance, the acclimatization period And the target processing amount can be processed in a short period of time.

Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings.
1 and 2 show an embodiment of the organic waste methane fermentation treatment apparatus of the present invention. FIG. 1 is a schematic configuration diagram of a methane fermentation treatment apparatus, and FIG. 2 is a schematic configuration diagram of a separation membrane concentrating device in FIG.

  First, the processing apparatus of FIG. 1 will be described. This processing apparatus pulverized organic waste, a pulverizer 11, a pulverized organic waste further pulverized pulverizer 12, and pulverized. A slurry adjustment tank 13 for storing organic waste to prepare a slurry, a methane fermentation tank 14 for performing methane fermentation of organic waste, a gas holder 16 for storing gas generated by fermentation, and a seed It is mainly comprised with the separation membrane concentration apparatus 20 for concentrating the microbial cell in sludge or a fermented liquor.

  A pulverizer 11 for charging and pulverizing organic waste is connected to a fine pulverizer 12 by a supply pipe, and is further connected to a slurry adjusting tank 13 for slurrying organic waste. Yes. And the supply piping from the slurry adjustment tank 13 is connected to the methane fermentation tank 14 via the supply pump which is not shown in figure. In addition, a pipe for taking out digestive juice is connected to the bottom of the methane fermentation tank 14.

  In the methane fermentation tank 14, a stirring blade 15 for stirring the slurry is installed, and a filter bed (not shown) on which anaerobic microorganisms mainly composed of methane bacteria are attached and supported is provided. .

  A pipe connected to the gas holder 16 is connected from the upper space of the methane fermentation tank 14, and the biogas generated in the methane fermentation tank 14 is stored in the gas holder 16. As a result, the biogas stored in the gas holder 16 is sent to the gas utilization system 17 which is a generator such as a fuel cell power generation device or a gas engine, where it is effectively used as fuel.

  The methane fermentation tank 14 is connected with a separation membrane concentrator 20 for obtaining a bacterial concentrate having a higher bacterial cell concentration by concentrating the bacterial cells in the seed sludge or fermentation broth, and the bacterial cell concentration in the present invention. Means. In the present invention, the separation membrane concentrating device 20 is not necessarily connected to the methane fermentation tank 14.

  Referring also to FIG. 2, in the separation membrane concentrating device 20, the separation membrane 22 is disposed in the concentration tank 21, and the liquid after membrane separation is discharged from the pipe 33 by the pump 25. . Further, an air diffuser 23 is disposed below the separation membrane 22.

  As the separation membrane 22, a conventionally known MF (microfiltration membrane), UF (ultrafiltration membrane) or the like is preferably used, and any type such as a flat membrane, a hollow fiber, and a tubular can be used. The pore size of the membrane is preferably such that useful bacteria do not flow out, and is preferably 0.01 to 0.5 μm. If the pore size is less than 0.01 μm, the filtration resistance increases, so the efficiency of the filtration treatment is reduced. This is not preferable, and if the pore size exceeds 0.5 μm, the bacteria pass and the concentration efficiency is reduced, which is not preferable.

  The air diffuser 23 is for performing a stable membrane separation process by washing the surface of the separation membrane 22, and a conventionally known air diffuser can be used.

  In the present invention, as the driving force of the separation membrane 22, in addition to suction by the pump 25, a water level difference may be used, or a pressurization method that increases the internal pressure of the concentration tank 21 may be used. Further, the bacterial cell concentration means in the present invention is not limited to a membrane separation device, and a centrifugal separation device or the like may be used.

  A pipe 31 for introducing the water to be concentrated is connected to the upper space 21 a of the concentration tank 21. An anaerobic gas cylinder 26 for replacing the upper space 21 a with anaerobic gas is connected via a valve 27.

  Further, the pipe 32 connected to the upper space 21 a is connected to the air diffuser 23 via the blower 24, and is configured so that the anaerobic gas in the upper space 21 a is sent to the air diffuser 23.

Next, a methane fermentation treatment method using the above methane fermentation treatment apparatus will be described.
For example, when a new methane fermentation tank is started up, as shown in FIG. 2, first, seed sludge or fermentation liquor that is to-be-concentrated water is introduced into the concentration tank 21 through a pipe 31.

  Here, the seed sludge is sludge that is the basis for performing methane fermentation, and is, for example, sludge in an anaerobic state such as sewage digestion sludge. Depending on the source of sludge, the species of fungi (bacteria) vary, and some of them contain methane bacteria.

  Moreover, a fermentation liquid is a liquid which is performing methane fermentation, and is sludge in which methane bacteria (especially high temperature methane bacteria if high temperature methane fermentation is performed) preferentially exists. In addition to methane bacteria, various bacteria in symbiotic relationship with methane bacteria exist in a well-balanced manner, and the sludge contains bacterial species (bacteria) that can be decomposed into methane without delay. Such a fermentation broth can be obtained from other methane fermentation tanks such as a medium temperature methane fermentation process (about 35 ° C.) and a high temperature methane fermentation process (about 55 ° C.) that have already been subjected to methane fermentation.

  The amount of inflow into the concentration tank 21 is preferably controlled by a water level sensor (not shown) installed in the concentration tank 21 or it is desirable to keep the water level in the concentration tank 21 constant by siphon, and the water level is higher than that of the separation membrane 22. It is more preferable to set it upward. Thereby, since the whole separation membrane 22 is immersed in to-be-concentrated water, the separation membrane 22 can be used efficiently, and damage to the membrane due to drying of the separation membrane 22 can be prevented.

  Next, prior to concentration by the separation membrane 22, when the concentrated tank 21 is filled with water to be concentrated, the valve 27 is opened, and the upper space 21 a in the concentrated tank 21 is replaced with anaerobic gas by the anaerobic gas cylinder 26. It is preferable to keep it. As the anaerobic gas, nitrogen, carbon dioxide, methane gas, generated biogas in methane fermentation treatment, or the like can be used.

  Further, at the time of concentration, it is preferable that the anaerobic gas is bubbled through the blower 24 by the air diffuser 23 installed below the separation membrane 22. Thereby, the surface of the separation membrane 22 can be washed, and stable membrane separation treatment can be performed. In addition, anaerobic microorganisms can also be killed by bubbling anaerobic gases.

  Next, the water to be concentrated in the concentration tank 21 is solid-liquid separated by the separation membrane 22 immersed in the concentration tank 21. As a result, the bacteria in the water to be concentrated are concentrated to become the bacteria concentrate 28 and remain in the concentration tank 21, and the separation liquid that does not contain the bacteria permeated through the separation membrane 22 is discharged out of the system by the suction pump 25. .

  The concentration ratio of the bacteria by the membrane is determined by the amount of water to be concentrated and the amount of the separation liquid to be added, and can be arbitrarily set according to the target organic substance load amount, etc., but the MLSS concentration (sludge concentration) in the bacteria concentrate 28 ) Is preferably concentrated to 5,000 to 100,000 mg / L, more preferably 10,000 to 50,000 mg / L. When the MLSS concentration is less than 5000 mg / L, it is not preferable because the concentration of bacteria is insufficient and the effect of shortening the acclimatization period is small, and when it exceeds 100,000 mg / L, filtration becomes difficult and the filtration efficiency is lowered, which is not preferable.

  At the time when the above-mentioned bacteria concentration ratio in the predetermined range is obtained, the membrane separation operation is stopped, the bacteria concentrated solution 28 is taken out and put into the methane fermentation tank 14, and then the methane fermentation treatment is started.

  That is, organic waste such as raw garbage discharged from restaurants and general households, food processing residues discharged from food factories, surplus sludge such as activated sludge treatment, or sewage treatment as human waste treatment An object to be treated consisting of drained wastewater containing organic matter such as sludge is roughly pulverized by a pulverizer 11 and then finely pulverized by a pulverizer 12 and put into a slurry adjusting tank 13. In this slurry adjustment tank 13, it adjusts so that it may be added as needed and it may become solid substance concentration 10-20 mass%. Thus, the decomposition rate and digestibility can be improved by grind | pulverizing and slurrying the organic waste used for a methane fermentation process.

  This slurry is sent to the methane fermentation tank 14 and added to the above-mentioned fungus concentrate 28 to perform methane fermentation in the fermentation tank. At this time, in the present invention, the object to be treated is added to the bacterial concentrated liquid 28 whose bacterial cell concentration has been increased in advance, so that the acclimatization period at startup can be greatly shortened.

  Other methane fermentation treatment conditions are not particularly limited, and the method of the present invention can be used for any treatment of medium temperature methane fermentation and high temperature methane fermentation. In addition, as described above, the microbial fermentation liquid 28 may be input into the methane fermentation tank 14 prior to the start of methane fermentation, or may be performed simultaneously with the start of the input load of the workpiece. Good.

  In addition, the methane fermentation treatment method of the present invention is not limited to when the methane fermentation tank is newly started up, but can also be applied when the input load of the object to be processed is increased at the time of restarting the methane fermentation treatment or during operation. In this case, what is necessary is just to use the methane fermentation liquid which already exists in the methane fermentation tank 14 as a fermentation liquid used as a liquid to be concentrated. That is, after concentrating the methane fermentation solution in the methane fermentation tank 14 using the separation membrane concentrating device 20 to obtain the bacterium concentrate 28, the bacterium concentrate 28 is returned to the methane fermentation tank 14 again. What is necessary is just to perform restart or increase in the input load of a to-be-processed object. Thereby, the acclimatization period in the case of increasing the input load of the workpiece during restart or during operation can be greatly shortened.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.
Example Using the processing apparatus as shown in FIGS. 1 and 2, continuous operation was performed using the methane fermentation treatment method of the present invention.

  Simulated garbage, which is organic waste, was used as the object to be treated. As simulated raw garbage, fruits, vegetables, meat, fish, eggs, rice, bread, etc. are mixed at a mixing ratio, diluted with tap water to a TS (solid content) concentration of 10%, and mixed. Using.

As seed sludge, digested sludge obtained by subjecting sewage-treated sludge to intermediate temperature methane fermentation was used, and seed sludge was concentrated using a hollow fiber membrane having a pore diameter of 0.1 μm in a separation membrane concentrator as shown in FIG. The MLSS concentration before concentration of seed sludge was 12000 mg / L, which was concentrated 2.5 times to obtain a bacterial concentrate having an MLSS concentration of 30000 mg / L. This microbial concentrate is transferred to a methane fermenter as shown in Fig. 1, and medium temperature methane fermentation using simulated raw garbage on HRT (fermentation liquid residence time) of 15 days (equivalent to COD _Cr loading of 10 g / (L · d)) Processed. As a result, the organic acid concentration was 100 to 150 mg / L during 30 days from the start of the methane fermentation treatment, the organic acid accumulation was small, and the methane fermentation treatment was performed smoothly.

Comparative Example 1
Except for not concentrating the seed sludge, the conditions were the same as in the example, and the seed sludge having an MLSS concentration of 12000 mg / L was transferred to the methane fermentation tank as it was to perform a medium temperature methane fermentation treatment. As a result, the organic acid concentration increased from the second day of operation, and the organic acid concentration exceeded 15000 mg / L on the fifth day. Along with this, the pH in the fermenter dropped to 5.3, the generation of methane gas stopped, and the methane fermentation treatment system broke down.

Comparative Example 2
As in Comparative Example 1, the seed sludge was not concentrated, and the seed sludge was transferred to the methane fermentation tank as it was, and the medium temperature methane fermentation treatment was started on HRT 30 days (corresponding to a COD _Cr load of 5 g / (L · d)). After 21 days, HRT was set to 25 days, 14 days later, HRT was set to 20 days, and 14 days later, HRT was set to 15 days, and operation was continued for 30 hours in this state. As a result, the organic acid concentration during this period was 80 to 150 mg / L and there was no accumulation of organic acid, and the methane fermentation treatment was performed smoothly. Cost.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for organic waste such as raw garbage, food processing residue, surplus sludge from activated sludge treatment, or methane fermentation treatment of wastewater containing organic matter.

It is a schematic block diagram which shows one Embodiment of the methane fermentation processing apparatus of this invention. It is a schematic block diagram of the separation membrane concentration apparatus in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Crusher 12 Fine pulverizer 13 Slurry adjustment tank 14 Methane fermentation tank 15 Stirring blade 16 Gas holder 17 Gas utilization system 20 Separation membrane concentrator 21 Concentration tank 22 Separation membrane 23 Aeration device 24 Blower 25 Suction pump 26 Anaerobic gas cylinder 27 Valve 28 Bacteria concentrate 31, 32, 33 Piping

Claims (6)

In the methane fermentation treatment method in which a waste material containing organic waste or wastewater containing organic matter is put into a methane fermentation tank and methane fermentation is performed to take it out.
At the start of methane fermentation, at the time of restart, or when increasing the input load of the processing object during operation, a bacterial concentrate that has increased the bacterial cell concentration by concentrating the bacterial cells in the seed sludge or fermentation broth A methane fermentation treatment method comprising adding to the treatment object or adding the treatment object to the bacterium concentrate.   The methane fermentation treatment method according to claim 1, wherein the bacterial cell concentration is increased by centrifugal separation or membrane separation of the seed sludge or fermentation broth.   The methane fermentation treatment method according to claim 1 or 2, wherein the bacterial cells are concentrated so that the bacterial cell concentration in the seed sludge or the fermentation broth is 5,000 to 100,000 mg / L as the sludge concentration.   A processing object supply means for introducing a processing object consisting of organic waste or waste water containing organic substance into a methane fermentation tank, a methane fermentation tank for methane fermentation of the processing object, and after the methane fermentation Digestive juice extraction means for taking out the digestive juice of the above, and bacterial cell concentration means for concentrating the bacterial cells in the seed sludge or fermentation liquid to increase the bacterial cell concentration, the bacterial cell concentration means comprising the methane A methane fermentation treatment apparatus, characterized in that it is provided outside the fermenter or is arranged so as to be able to be put in and out of the methane fermenter.   The methane fermentation treatment apparatus according to claim 4, wherein the bacterial cell concentration means is a centrifugal separator or a membrane separator.   The methane fermentation according to claim 4 or 5, wherein the cell concentration means is configured such that the cell concentration in the seed sludge or the fermentation broth is 5,000 to 100,000 mg / L as the sludge concentration. Processing equipment.

Images