JP2005152875A - Methane fermentation treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methane fermentation treatment method capable of stably performing methane fermentation by monitoring an ammoniac nitrogen concentration in a methane fermentation tank with a simple measuring method. <P>SOLUTION: In the methane fermentation treatment method of slurrying organic wastes in a slurry digester 10, feeding the slurry in the methane fermentation tank 11, causing the methane fermentation by anaerobic microorganisms and taking out the fermentation product as an fermented solution which is denitrified by a waste liquid treatment tank 12, electroconductivity in the methane fermentation tank 11 is measured with an electroconductivity analyzer 31, and, when the measured value exceeds a predetermined value, the electroconductivity in the methane fermentation tank 11 is reduced, for example, by feeding treated water in the waste liquid treatment tank 12 as dilution water into the methane fermentation tank 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a methane fermentation treatment method for treating organic waste such as manure, raw garbage, food processing residue and the like using anaerobic microorganisms.

  Most organic waste such as garbage and digested sludge is incinerated or disposed of in landfills. However, due to problems such as dioxin generation due to incineration, tightness of landfill sites, and bad odors, treatment methods with less environmental impact are available. It has been demanded. In order to solve these problems, a system has been developed in which organic waste is subjected to methane fermentation, and the generated methane gas is generated using a fuel cell or a gas engine.

  This methane fermentation is an energy-saving treatment method that can decompose organic waste into biogas and water, greatly reducing the amount of waste, and does not require aeration power because it is anaerobic. There is an advantage that methane gas can be recovered as energy.

  In the methane fermentation treatment, organic waste is pulverized and slurried, and then the slurry is put into a fermenter and fermented with methane bacteria under anaerobic conditions to convert the organic waste into methane gas. Various processing methods and fermenters have been proposed depending on the properties of the input raw materials and operating conditions.

  In methane fermentation, when fermentation is stable, a certain amount of biogas is produced if a specified amount of organic waste such as garbage is input. However, the fermentation state also fluctuates due to fluctuations in the fermentation temperature and the amount of dust input, and this fluctuation causes a reduction in fermentation performance. The reason why the fermentation performance is reduced is that the activity of the anaerobic bacteria group mainly related to methane fermentation is reduced, and as a factor of the decrease in activity, there is generation of an inhibitor such as ammonia in addition to pH and temperature. Therefore, a technique for controlling the fermentation state so that the concentration of ammonia, particularly ammoniacal nitrogen, is not more than a predetermined concentration is known.

  For example, Patent Document 1 below discloses that when organic wastewater is subjected to methane fermentation, the organic wastewater is diluted so that the concentration of ammoniacal nitrogen in the tank is 2000 mg / L or less.

  Further, in Patent Document 2 below, the ammonia nitrogen concentration in a methane fermentation tank for treating organic waste is detected by a detection unit, and water is introduced into the fermentation tank so that this concentration is 5000 mg / L or less. Supplying and diluting is disclosed.

Furthermore, the following Patent Document 3 discloses that waste water denitrified in a waste water treatment tank is injected into raw garbage as dilution water to reduce the ammonia concentration in the methane fermentation tank.
Japanese Patent Publication No.7-115030 JP 2003-39039 A Japanese Patent Laid-Open No. 11-57661

  As mentioned above, ammonia, one of the inhibitors of methane fermentation, inhibits the activity of bacteria related to methane fermentation and significantly reduces the fermentation performance. Therefore, detection and control of ammoniacal nitrogen concentration in the fermentation broth Is very important. And also in said prior art, reducing ammonia nitrogen concentration with dilution water is disclosed.

  However, in the above Patent Documents 1 to 3, a method for detecting the ammoniacal nitrogen concentration is not disclosed in detail. Usually, as a detection method, it is conceivable to detect ammonia nitrogen using an analytical instrument such as ion chromatography. However, this measurement method requires expensive precision measurement equipment, and is expensive to manage and maintain. Moreover, since the time required for detection is long and time-consuming, it is not suitable for constant monitoring.

  For this reason, it was practically difficult to control the ammonia nitrogen concentration to the optimum range by dilution while constantly monitoring the ammonia nitrogen concentration during the methane fermentation treatment.

  The object of the present invention has been made in view of the above-mentioned problems of the prior art, and is to stably perform methane fermentation by monitoring the ammoniacal nitrogen concentration in the methane fermentation tank by a simpler measurement method than before. The object is to provide a method for methane fermentation treatment.

That is, in the methane fermentation treatment method of the present invention, the organic waste is slurried in a slurry adjustment tank, put into the methane fermentation tank, methane-fermented by anaerobic microorganisms, taken out as a fermentation liquid, and the fermentation liquid is removed. In the methane fermentation treatment method to be treated in the waste liquid treatment tank to be nitriding,
At least the electrical conductivity in the methane fermenter is measured, and when the measured value of the fermenter is a predetermined value or more, means for lowering the electrical conductivity in the methane fermenter is provided.

  According to the method of the present invention, since the salt concentration in the liquid is displayed as electric conductivity, ammonium ions that are bases are also displayed as electric conductivity. The present inventors have found that there is a positive correlation between the ammoniacal nitrogen concentration in the methane fermentation tank and the electrical conductivity when the properties of the organic waste are stable. Therefore, by using the electrical conductivity in the methane fermenter as an index of the ammonia nitrogen concentration, the ammonia nitrogen concentration can be reduced at a low cost and without using a complicated and expensive analytical instrument such as gas chromatography. It was found that it can be measured easily over time and can be monitored constantly. Thus, according to the present invention, the ammonia nitrogen concentration can be monitored using the electrical conductivity as an index, and the methane fermentation state can be favorably maintained by maintaining the electrical conductivity below a predetermined value.

  In this invention, when the said fermenter measured value is 14 mS / cm or more, it is preferable to give a means to lower the electrical conductivity in the said methane fermenter. According to this aspect, since the ammoniacal nitrogen concentration in the methane fermentation tank can be maintained at 1500 mg / L or less, which is generally referred to as an inhibition region, the fermentation state in the methane fermentation tank can be stably maintained.

  Moreover, in this invention, the electrical conductivity in the said methane fermentation tank and the electrical conductivity in the said slurry adjustment tank are measured, and it is the said fermenter measured value and the electrical conductivity in the said slurry adjustment tank. When the difference from the adjusted tank measurement value is equal to or greater than a predetermined value, it is preferable to provide means for lowering the electrical conductivity in the methane fermentation tank.

  According to this aspect, for example, Na, K, Ca, Mg, etc. included in the organic waste such as garbage, which is input to the methane fermentation treatment system, from the beginning correspond to the salt concentration. Fermented garbage itself has electrical conductivity. In addition, ammonium ions generated in the methane fermentation tank are also displayed as electrical conductivity because they are bases as described above, but in order to accurately convert the ammoniacal nitrogen content present in the methane fermentation tank as electrical conductivity. It is necessary to measure the salt concentration present in the input organic waste from the beginning as the electrical conductivity and remove it from the above fermenter measurement. Therefore, the electrical conductivity of the slurry adjustment tank before being put into the methane fermentation tank is obtained as the adjustment tank measurement value, and by subtracting from the fermentation tank measurement value, an electric conductivity value correlated with the ammoniacal nitrogen concentration can be obtained. .

  From the above, the fermentation state in the methane fermentation tank can be more stably maintained more accurately by using the difference in electrical conductivity between the methane fermentation tank and the slurry adjustment tank as an index. Therefore, this aspect can be suitably used particularly when the raw organic waste is raw garbage.

  Moreover, in this invention, the fermenter measured value which measured the electrical conductivity in a methane fermenter, and the adjustment tank measured value which is the electrical conductivity in the slurry adjustment tank calculated | required from the slurry salt density | concentration in a slurry adjustment tank When the difference is greater than or equal to a predetermined value, it is preferable to provide means for lowering the electrical conductivity in the methane fermentation tank.

  For example, in the case of cooked garbage such as rice cake, since it contains a lot of salt, the salt contained in organic waste is mainly Na, and the salt concentration in organic waste is Na concentration. Can be approximated. Table 1 shows the electrical conductivity obtained by calculation from the Na concentration and the electrical conductivity actually measured with an electrical conductivity meter, but only about 1 mS / cm has occurred. Therefore, it is possible to derive the electrical conductivity of the slurry from the Na concentration without using an electrical conductivity meter, and the electrical conductivity in the slurry adjustment tank obtained by this calculation and the methane fermentation tank By using the difference from the electrical conductivity as an index, the fermentation state in the methane fermentation tank can be stably maintained.

  Moreover, in this invention, the electrical conductivity in the said methane fermentation tank and the electrical conductivity in the said waste liquid processing tank are measured, It is the said fermenter measured value and the electrical conductivity in the said waste liquid processing tank. It is also preferable to provide means for lowering the electrical conductivity in the methane fermentation tank when the difference from the measured value of the waste liquid treatment tank is a predetermined value or more.

  According to this aspect, for example, in the case of an organic waste containing a large amount of ammonia components such as human waste, the electrical conductivity of the unfermented organic waste in the slurry adjustment tank is likely to vary. For this reason, as described above, the difference in electrical conductivity between the methane fermentation tank and the slurry adjustment tank does not directly serve as an index of fermentation performance. For this reason, the fermentation state in the methane fermentation tank can be more stably maintained more accurately by using the difference in electrical conductivity between the methane fermentation tank and the waste liquid treatment tank as an index. Therefore, it can be suitably used particularly when the organic waste of the raw material contains an ammonia component and urine.

  Further, in the present invention, the electrical conductivity in the methane fermentation tank and a part of the fermentation liquid taken out from the methane fermentation tank flow into the deaeration part, and the electrical conductivity in the deaeration part after the deaeration treatment When the difference between the measured value of the methane fermentation tank and the measured value of the deaeration part is equal to or greater than a predetermined value, it is preferable to provide means for lowering the electrical conductivity in the methane fermentation tank.

  Ammonia nitrogen in the fermentation broth can be diffused and removed as ammonia gas in the gas phase by introducing air and aeration. Therefore, the difference in electrical conductivity between the methane fermentation tank and the deaerated portion after the deaeration treatment indicates an electrical conductivity value resulting from the ammonia gas removed by the deaeration treatment, and the difference in the electrical conductivity By using as an index, the ammonia nitrogen concentration in the methane fermentation tank can be grasped, and the fermentation state in the methane fermentation tank can be stably maintained.

  In addition, the electrical conductivity in the deaeration unit immediately after the fermentation broth from the methane fermenter is input to the deaeration unit and the electrical conductivity in the deaeration unit after the deaeration treatment are measured, and the measured value and degassing immediately after the input are measured. When the difference from the measured value after the gas treatment is a predetermined value or more, it is preferable to provide means for lowering the electrical conductivity in the methane fermentation tank.

  According to this aspect, by using the difference in the electrical conductivity of the fermentation broth before and after the deaeration treatment as an index, the ammoniacal nitrogen concentration in the methane fermentation tank can be grasped, so the fermentation broth in the deaeration part The fermentation state can be maintained stably only by monitoring the electrical conductivity.

  Furthermore, in this invention, when the difference of the said measured value is 9 mS / cm or more, it is preferable to give a means to reduce the electrical conductivity in the said methane fermentation tank.

  According to this aspect, when the difference in measured electrical conductivity is 9 mS / cm or more, the ammonia nitrogen concentration in the methane fermenter is reduced by reducing the electrical conductivity in the methane fermenter as described above. Can be maintained at 1500 mg / L or less.

  Further, in the present invention, as a means for lowering the electrical conductivity in the methane fermentation tank, the treated water in the waste liquid treatment tank or the supply water from the outside can be supplied as dilution water into the methane fermentation tank. preferable.

  According to this aspect, based on the measured value of electric conductivity or the difference between the measured values, the treated water in the waste liquid treatment tank or the supply water from the outside is supplied as dilution water into the methane fermentation tank. Thus, the ammonia nitrogen concentration in the methane fermentation tank can be maintained at a predetermined value or less in a simpler and more reliable manner than in the past, and methane fermentation can be stabilized.

  According to the present invention, by using the electrical conductivity in the methane fermenter as an index, the ammonia nitrogen concentration in the methane fermenter is monitored and controlled so that the electrical conductivity does not exceed a predetermined value. Since the increase in the ammoniacal nitrogen concentration in the methane fermentation tank can be suppressed and the operation can be performed so as not to inhibit the activity of anaerobic bacteria, methane fermentation can be performed stably. In addition, when using the difference in electrical conductivity between the methane fermentation tank, slurry adjustment tank, waste liquid treatment tank, or degassing section, the concentration of ammonia nitrogen according to the nature of the organic waste as the raw material Can be monitored, and a stable fermentation state can be maintained.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. The schematic block diagram of embodiment (i) of the methane fermentation processing apparatus which can be used for the methane fermentation processing method of this invention is shown by FIG.

  First, the processing apparatus of FIG. 1 will be described. This processing apparatus is for processing a slurry adjusting tank 10 for slurrying and storing organic waste, a methane fermentation tank 11, and a fermentation liquid after methane fermentation treatment. It is mainly composed of the waste liquid treatment tank 12.

  The piping from the slurry adjustment tank 10 is connected to the methane fermentation tank 11 via the slurry supply pump 21. The pipe from the methane fermentation tank 11 is connected to the waste liquid treatment tank 12, and the pipe from the waste liquid treatment tank 12 is connected to the methane fermentation tank 11 via the treatment liquid circulation pump 22, so that the waste liquid treatment is performed. A part of the treated water denitrified in the tank 12 is configured to be returned to the methane fermentation tank 11.

  The waste liquid treatment tank 12 only needs to be capable of denitrification, for example, an activated sludge tank for performing a biological treatment method for removing organic substances and nitrogen by microorganisms, or catalytic combustion with air after deaeration of ammonia. For example, an apparatus that performs an ammonia stripping method that renders nitrogen gas harmless can be used.

  From the bottom of the methane fermentation tank 11, a pipe for extracting the slurry after the methane fermentation treatment is connected via a slurry extraction pump 23. Further, a tap water tank 13 is connected to the bottom of the methane fermentation tank 11 via a supply pump 24 so that dilution water in the tap water tank 13 can be supplied into the methane fermentation tank 11.

  Furthermore, a pipe for taking out the generated biogas is connected to the upper part of the methane fermentation tank 11, and this biogas is collected by a gas holder (not shown).

  Electrical conductivity meters 30 and 31 are connected to the slurry adjustment tank 10 and the methane fermentation tank 11, respectively, and the electric conductivity in the slurry adjustment tank 10 and the methane fermentation tank 11 can be measured. Here, as the electric conductivity meters 30 and 31, conventionally known ones can be used and are not particularly limited.

  The measurement values from the electric conductivity meters 30 and 31 are configured to be input to a PLC 40 (programmable logic controller) which is an arithmetic unit. The arithmetic unit PLC 40 performs the processing shown in the flowchart of FIG. It has been broken.

  Arithmetic processing and control by the PLC 40 will be described with reference to FIG. First, in step S <b> 1, the electric conductivity in the slurry adjustment tank 10 measured using the electric conductivity meter 30 is input to the PLC 40 as a measured value. Next, in step S2, the electrical conductivity of the fermentation broth in the methane fermentation tank 11 measured using the electrical conductivity meter 31 is input to the PLC 40 as a measured value. Steps S1 and S2 are performed almost simultaneously.

  Then, the process proceeds to step S3, and it is determined whether or not the difference between measured values is within a predetermined range. It is determined whether the measured value is within a predetermined range. If it is within the predetermined range, the process proceeds to step S4, and methane fermentation is continued as it is. When the difference between the measured values exceeds the predetermined range, the process proceeds to step S5 or step S6. Either of the processes of step S5 and step S6 can be preferably used.

  In step S5, the supply pump 24 is operated to supply clean water to the methane fermentation tank 11, and the fermentation liquid in the methane fermentation tank 11 is diluted. In step S6, the processing liquid circulation pump 22 is operated to supply the processing water to the methane fermentation tank 11, and the fermentation liquid in the methane fermentation tank 11 is diluted.

  As described above, the PLC 40 is configured such that the electrical conductivity of the slurry can be controlled within a predetermined value range.

Next, the methane fermentation processing method of this invention using this processing apparatus is demonstrated.
In FIG. 1, organic waste such as livestock manure such as cattle and pigs and raw garbage is crushed and pulverized and stored in a slurry adjusting tank 10 where it is diluted with appropriate water to be slurried. Slurry is preferably adjusted so that the solid concentration is 10 to 20% by mass. The embodiment of FIG. 1 is an example that can be preferably applied particularly when the organic waste is garbage.

  Next, this slurry is put into the methane fermentation tank 11 by the slurry supply pump 21 to perform methane fermentation.

  The methane fermentation tank 11 is provided with a fixed filter bed or the like filled with immobilized microorganisms on which anaerobic microorganisms such as methane bacteria (not shown) are attached and supported. The slurry is subjected to methane fermentation and anaerobic. Organic waste is decomposed by microorganisms. It is preferable to perform the temperature in methane fermentation at 50-60 degreeC. According to this, since the fermentation with a high-temperature methane bacterium having higher activity can be performed, the decomposition rate of the organic waste can be further improved.

  In addition, the same amount of fermentation broth as the slurry supplied at regular intervals is extracted from the bottom of the methane fermentation tank 11 by the slurry extraction pump 23, and the inside of the methane fermentation tank 11 is always filled with a fixed amount of slurry. . The biogas produced by fermentation is collected in a gas holder (not shown) and is effectively used as a fuel for a power generator such as a fuel cell power generation device or a gas engine or boiler.

  Here, in the present invention, in the slurry adjustment tank 10 and the methane fermentation tank 11, the electric conductivity is measured by the electric conductivity meters 30, 31, and the adjustment tank measurement value and the fermentation tank measurement value are obtained, respectively. This is input to the PLC 40.

  And in PLC40, the difference of the electrical conductivity of an adjustment tank measured value and a fermenter measured value is calculated, and based on this measured value difference, the process liquid circulation pump 22 is operated as needed, and waste liquid A part of the denitrified treated water in the treatment tank 12 is supplied into the methane fermentation tank 11 for dilution, and maintained so that the difference in electric conductivity meter is less than a predetermined value. Here, since the treated water treated in the waste liquid treatment tank 12 has undergone a denitrification step, the ammoniacal nitrogen concentration is reduced to 10% or less of the fermentation broth.

  As described above, the present invention is characterized in that the measured value of electrical conductivity is used as a monitoring index of the methane fermentation tank instead of the ammoniacal nitrogen concentration. Since this electrical conductivity corresponds to the ionic salt concentration of the whole fermentation broth, the measured value of electrical conductivity is correlated with ammonium ions.

  In FIG. 3 and Table 2, the electrical conductivity meter was previously immersed in the fermentation liquid part of the methane fermenter, and the correlation between the electrical conductivity and the ammoniacal nitrogen concentration measured by ion chromatography was measured. It is.

  From FIG. 3 and Table 2, it can be seen that the electrical conductivity of the fermentation broth in the methane fermenter is highly correlated with ammoniacal nitrogen. Therefore, the measured value of electrical conductivity can be used as a monitoring index of ammonia nitrogen in the methane fermentation tank. In FIG. 3, even when the ammoniacal nitrogen concentration by the ion chromatograph method is zero, the electrical conductivity is 5.5 mS / cm because of ion components other than ammonium ions.

Inhibition of anaerobic bacteria such as methane bacteria by ammonia is mainly stronger in non-dissociated ammonia (NH ₃ ) than in ammonium ions (NH ₄ ⁺ ). However, it is known that when ammonium ion is measured by ion chromatography and the concentration converted to ammonia nitrogen exceeds a certain value, it becomes an inhibition region (KHHansen et al., Water Research, vol. 32, No. .1, p5-12 (1998)). According to this document, the inhibition by ammonia occurs at an ammoniacal nitrogen concentration of 4000 mg / L, and it occurs at 1500 to 2000 mg / L when acclimatization is not performed.

  Therefore, since it is considered that stable methane fermentation can be maintained if the ammonia nitrogen concentration is 1500 mg / L or less, the electrical conductivity at the ammonia nitrogen concentration of 1500 mg / L obtained from the regression equation of FIG. If the electrical conductivity in the methane fermentation tank is maintained at 14 mS / cm or less with 14.8 mS / cm as a reference, a stable methane fermentation state can be maintained.

  As described above, in this embodiment, it is assumed that the organic waste is garbage. In this case, since the nitrogen component is not yet ammonia in the slurry adjusting tank, it is not detected as the electric conductivity corresponding to ammonium ions. However, raw garbage itself has an electrical conductivity of 5 to 6 mS / cm. Therefore, the electric conductivity of the unfermented garbage itself is measured by the electric conductivity meter 30 in the slurry adjusting tank 10, and the difference from the electric conductivity in the methane fermentation tank 11 is calculated by the PLC 40. To do.

  Then, when the difference in electrical conductivity is greater than or equal to a predetermined value, the dilution water is supplied. In this case, as shown in FIG. 3, the electrical conductivity corresponding to an ammoniacal nitrogen concentration of 1500 mg / L or less at which a stable methane fermentation state is obtained is 14 mS / cm or less, and the electrical conductivity of the garbage itself is 5 to 6 mS / cm. Therefore, it is preferable to take the difference between the two and supply dilution water when the difference in electrical conductivity is 9 mS / cm or more and maintain the difference in electrical conductivity to be less than 9 mS / cm. .

  In addition, when the component of organic waste is single, only the measured value of the electric conductivity meter 31 in the methane fermentation tank 11 is used, and when this measured value of the fermenter exceeds 14 mS / cm, The treatment liquid circulation pump 22 is operated to supply and dilute part of the denitrified treated water in the waste liquid treatment tank into the methane fermentation tank 11, and the measured value of the electric conductivity meter 31 is 14 mS / cm or less. May be maintained.

  As the dilution water, the supply pump 24 may be operated in place of the treatment liquid circulation pump 22, whereby a part of tap water in the tap water tank 13 is supplied into the methane fermentation tank 11 for dilution. May be.

  FIG. 4 shows a schematic configuration diagram of an embodiment (ii) of a methane fermentation treatment apparatus that can be used in the methane fermentation treatment method of the present invention. In the following description of the embodiment, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In this embodiment, an ion meter 35 is provided instead of the electric conductivity meter 30 in the slurry adjustment tank 10, and the Na concentration value in the slurry adjustment tank by the ion meter 35 and the electric conductivity meter 31 are used. The electrical conductivity value in the methane fermenter is input to a PLC 41 (programmable logic controller) which is a computing unit, and the processing shown in the flowchart of FIG. 5 is performed in the computing unit PLC 41.

  Next, arithmetic processing and control by the PLC 41 will be described with reference to FIG. The processes in steps S2 and 4-6 are the same as those in the above embodiment, and are omitted here.

  In step S7, the ion concentration in the slurry adjusting tank is measured using the ion meter 35, and is input into the PLC 41. The process proceeds to step S8, where the ion concentration is converted into an electrical conductivity value.

  In step S9, it is determined whether or not the difference in electrical conductivity between step S2 and step S8 is within a predetermined range. If it is within the predetermined range, the process proceeds to step S4 and the methane fermentation is continued. If it is outside the predetermined range, the process proceeds to step S5 or step S6 to dilute the fermentation broth in the methane fermentation tank 11. Is called.

  That is, the PLC 41 is configured to measure the electric conductivity in the slurry adjustment tank from the Na concentration of the slurry, and further, the electric conductivity difference between the slurry adjustment tank 10 and the methane fermentation tank 11 is predetermined. It is configured to be below the value.

This embodiment can be suitably used in the case where the organic waste is mainly composed of one kind of salt component such as garbage. Also, in order to convert from salt concentration to electrical conductivity value, it is easily converted by converting to molar concentration (mol / l) and then multiplying the substance and concentration by the intrinsic molar conductivity (Scm ² / mol). I can do it. This molar conductivity is described in, for example, the Chemical Society of Japan, “Chemical Handbook Basic Edition II”, revised 4th edition, Maruzen Co., Ltd., September 30, 1993, page 447.

  A stable methane fermentation state is maintained by adjusting the electrical conductivity in the methane fermentation tank so that the difference between the electrical conductivity in the slurry adjustment tank and the electrical conductivity in the methane fermentation tank is less than 9 mS / cm. However, since the electrical conductivity in the slurry adjusting tank can be obtained from the salt concentration of the slurry, the equipment cost and the maintenance cost necessary to maintain a stable methane fermentation state can be reduced.

  FIG. 6 shows a schematic configuration diagram of an embodiment (iii) of a methane fermentation treatment apparatus that can be used in the methane fermentation treatment method of the present invention. In the following description of the embodiment, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In this embodiment, an electrical conductivity meter 32 is provided in the waste liquid treatment tank 12, and measured values from the electrical conductivity meters 31, 32 are input to a PLC 42 (programmable logic controller) that is a computing unit. .

  Next, arithmetic processing and control by the PLC 42 will be described with reference to FIG. Since the processes in steps S2 and 4 to 6 are the same as those in the above embodiment, they are omitted here.

  In step S <b> 10, the electrical conductivity of the treated water in the waste liquid treatment tank 12 measured using the electrical conductivity meter 32 is input to the PLC 42 as a measured value.

  And it progresses to step S11 and it is judged whether the difference of a measured value is in a predetermined range. It is determined whether the measured value is within a predetermined range. If it is within the predetermined range, the process proceeds to step S4 and methane fermentation is continued. If it is out of the predetermined range, step S5 or step is performed. It moves to S6 and dilution of the fermented liquor in the methane fermenter 11 is performed.

  That is, the PLC 42 has a configuration in which the difference in electrical conductivity between the methane fermentation tank 11 and the waste liquid treatment tank 12 is set to a predetermined value or less.

  This embodiment is suitably used when the organic waste is human waste or the like and has a large ammonia component. That is, if the organic waste as a raw material contains a large amount of an ammonia component, the electrical conductivity in the slurry adjustment tank fluctuates, so that the difference in electrical conductivity is directly an indicator of fermentation performance as in the above embodiment. Don't be. For this reason, the difference in electrical conductivity between the methane fermentation tank 11 and the waste liquid treatment tank 12 is used as an index, and when the difference in electrical conductivity is 9 mS / cm or more as in the above embodiment, the dilution water is supplied. As a result, the ammoniacal nitrogen concentration in the methane fermentation tank 11 can be maintained at 1500 mg / L or less.

  FIG. 8 shows a schematic configuration diagram of an embodiment (iv) of a methane fermentation treatment apparatus that can be used in the methane fermentation treatment method of the present invention. In the following description of the embodiment, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  A deaeration unit 14 for performing a deaeration process is connected to the methane fermentation tank 11 via a pipe so that a part of the fermentation liquor can be taken out to the deaeration unit 14.

  A blower 25 is installed in the degassing unit 14, and the fermentation solution is degassed by the air fed from the blower 25, and ammonia nitrogen can be removed. The deaeration unit 14 is provided with an electric conductivity meter 33 so that the electric conductivity in the deaeration unit can be measured. Then, the PLC 43 (programmable logic controller) in which the electrical conductivity value in the methane fermentation tank by the electrical conductivity meter 31 and the electrical conductivity value in the deaeration unit 14 after the deaeration treatment by the electrical conductivity meter 33 are computing units. ) And the processing shown in the flowchart of FIG. 9 is performed in the arithmetic unit PLC43.

  Next, arithmetic processing and control by the PLC 43 will be described with reference to FIG. Since the processes in steps S2 and 4 to 6 are the same as those in the above embodiment, they are omitted here.

  In step S <b> 12, the electrical conductivity after the deaeration process in the deaeration unit 14 measured using the electrical conductivity meter 33 is input to the PLC 43 as a measured value. Then, the process proceeds to step S13, and it is determined whether or not the difference between measured values is within a predetermined range. If it is within the predetermined range, the process proceeds to step S4 and the methane fermentation is continued. If it is outside the predetermined range, the process proceeds to step S5 or step S6 to dilute the fermentation broth in the methane fermentation tank 11. Is called.

  The PLC 43 is configured such that the difference between the electrical conductivity in the methane fermentation tank and the electrical conductivity in the deaeration part after the deaeration treatment is set to a predetermined value or less.

In the deaeration treatment of the fermentation liquid in the deaeration part, air is introduced into the deaeration part, the fermentation liquid is aerated, and ammonia nitrogen in the fermentation liquid is diffused as ammonia gas into the atmosphere. For example, when ammoniacal nitrogen is removed from 1 L of the fermentation broth under the condition of an aeration flow rate of 1 L / L / min, it can be removed almost completely in 48 hours, and detailed numerical values are shown in Table 3. Moreover, when 0.5L is set as the aeration flow rate 5L / L / min, it can be removed in about 2 hours. By adjusting the amount of the fermentation liquid to be put into the deaeration part and the aeration flow rate, ammonia removal from the fermentation liquid can be achieved. It can be carried out in a short time.

  In this embodiment, the electrical conductivity of the deaerated part after the deaeration treatment is measured, the difference from the electrical conductivity in the methane fermentation tank is obtained, and the difference in electrical conductivity is adjusted to be within a predetermined range. The methane fermentation state is maintained. As in the other embodiments, the difference in electrical conductivity is that the ammonia nitrogen concentration in the methane fermenter 11 is maintained at 1500 mg / L or less by supplying dilution water when it is 9 mS / cm or more. it can.

  In addition, since the fermentation liquid in the methane fermenter and the fermentation liquid in the deaeration unit are liquids having substantially the same properties such as the solid content concentration, the difference in the electrical conductivity can indicate highly accurate ammonia nitrogen. .

  FIG. 10 shows a schematic configuration diagram of an embodiment (v) of a methane fermentation treatment apparatus that can be used in the methane fermentation treatment method of the present invention.

  Similarly to the embodiment (iv) shown in FIG. 8, a deaeration unit 14 for performing a deaeration process is connected to the methane fermentation tank 11 via a pipe, and a part of the fermentation solution can be taken out to the deaeration unit 14. However, the electric conductivity meter is arranged only in the deaeration unit 14.

  The electrical conductivity immediately after charging the fermented liquid from the methane fermenter 11 to the deaeration unit 14 and immediately after the deaeration process is configured such that the measured value can be input to the PLC 44. The flow chart of FIG. The process shown is being performed.

  Next, arithmetic processing and control by the PLC 44 will be described with reference to FIG. Since the processes in steps S2 and 4 to 6 are the same as those in the above embodiment, they are omitted here.

  In step S14, using the electric conductivity meter 33, the electric conductivity immediately after the fermentation broth from the methane fermentation tank 11 is input is input to the PLC 44 as a measured value, and the deaeration process of the fermentation broth is started. And it progresses to step S15 and the electrical conductivity in the deaeration part 14 after a deaeration process for a predetermined time is input into PLC44 as a measured value.

  Then, the process proceeds to step S16, and it is determined whether or not the difference between the measurement values input previously is within a predetermined range. If it is within the predetermined range, the process proceeds to step S4 and the methane fermentation is continued. If it is outside the predetermined range, the process proceeds to step S5 or step S6 to dilute the fermentation broth in the methane fermentation tank 11. Is called.

  In other words, the PLC 44 is configured such that the electrical conductivity difference before and after the deaeration process in the deaeration part becomes a predetermined value.

  In this embodiment, the difference in the electrical conductivity of the deaeration part before and after the deaeration treatment is used as an indicator of the ammonia nitrogen concentration in the methane fermentation tank. Therefore, the time required for the deaeration treatment of the fermentation broth is measured and grasped. It is necessary to keep. However, the difference in electrical conductivity represents ammoniacal nitrogen in the fermentation broth removed by the deaeration treatment, and can more accurately indicate the ammoniacal nitrogen concentration in the methane fermentation tank. Similarly, when the difference in electrical conductivity is 9 mS / cm or more, which is the same as that in the above-described embodiment, by supplying dilution water, the ammonia nitrogen concentration in the methane fermentation tank 11 is 1500 mg / L or less. Can be maintained. Moreover, in order to maintain a stable methane fermentation state, it is only necessary to monitor the electrical conductivity in the deaeration part, and the equipment cost and the maintenance cost can be reduced.

  As described above, according to the present invention, even if the properties of the organic waste are different, the fermentation performance can always be stably maintained by appropriately selecting the monitoring point of the electrical conductivity. In addition, the measurement of the electrical conductivity in this invention may be performed continuously, and may be intermittently performed as needed.

  Hereinafter, the present invention will be described in more detail by way of examples. In addition, this invention is not limited to a following example.

Example 1
Using the treatment apparatus as shown in FIG. 1, continuous operation was performed using the methane fermentation treatment method of the present invention. As the methane fermenter 11, a fermenter having a capacity of 10 liters was used, and the fermentation temperature was 55 ° C. As an electrical conductivity meter, a conductivity meter ES-51 manufactured by HORIBA was used.

  As the organic waste, raw garbage raw materials with a lot of proteins shown in Table 4 were used. TS in Table 4 is a solid content concentration.

In addition, when the difference between the measured value of the electrical conductivity meter 30 and the measured value of the electrical conductivity meter 31 exceeds 9 mS / cm, the treated water denitrified from the waste liquid treatment tank 12 is 0.5 to 1 L. And maintained at less than 9 mS / cm. In addition, since the addition rate of dilution water and the reduction rate of electrical conductivity are proportional, for example, by adding 1 L of dilution water to a capacity of 10 L, a decrease in electrical conductivity of 10% can be expected. FIG. 12 shows the difference in electrical conductivity during operation, the time-dependent change of ammoniacal nitrogen in the methane fermenter determined by ion chromatography, and Table 5 summarizes the detailed numerical values.

  From the results shown in FIG. 12 and Table 5, the difference in electrical conductivity gradually increases after the introduction of the slurry containing a large amount of nitrogen, and ammonia nitrogen increases accordingly. When the difference in electrical conductivity exceeds 9 mS / cm (9th day), circulate the treatment liquid from the waste liquid treatment tank and lower it to less than 9 mS / cm. As a result, lower the ammonia nitrogen concentration to less than 1500 mg / L. The methane fermentation was performed smoothly.

Example 2
A continuous operation was performed using the methane fermentation treatment method of the present invention using a treatment apparatus as shown in FIG. As the methane fermenter 11, a fermenter having a capacity of 60 liters was used, and the fermentation temperature was 55 ° C. As the ion meter, a sodium ion meter C-122 manufactured by HORIBA was used. As organic waste, garbage was used for continuous operation. Moreover, the new slurry was thrown into the methane fermentation tank 11 every 5 days of operation. In FIG. 13, the electrical conductivity of the slurry adjusting tank calculated from the Na concentration of the slurry, the electrical conductivity in the methane fermentation tank measured by the electrical conductivity meter 31, and the ammonia of the fermenter determined from the ion chromatography method. Table 6 shows the detailed numerical values of the time-dependent change of nitrogen.

  From the results of FIG. 13 and Table 6, when the electrical conductivity difference is 9 mS / cm or less, the ammoniacal nitrogen concentration is 1500 mg / L or less, while when the electrical conductivity difference is 9 mS / cm or more, the ammoniacal nitrogen concentration is The result that it becomes 1500 mg / L or more is obtained, and the stable methane fermentation state can be maintained by controlling the difference in electrical conductivity to be 9 mS / cm or less.

Example 3
Except for using a treatment apparatus as shown in FIG. 6 and using organic waste mixed with 0.1 to 0.5 parts by weight of human waste relative to 1 part by weight of raw garbage raw materials in Table 2, Continuous operation was performed under the same conditions as in Example 1. FIG. 14 shows the difference in electrical conductivity during operation, the time-dependent change of ammoniacal nitrogen in the fermenter determined by ion chromatography, and Table 7 shows the detailed numerical values.

  From the results of FIG. 14 and Table 7, as in Example 1, the ammoniacal nitrogen concentration could be maintained below 1500 mg / L, and methane fermentation was performed smoothly.

Example 4
Using the treatment apparatus as shown in FIG. 8, continuous operation was performed using the methane fermentation treatment method of the present invention. As the methane fermenter 11, a fermenter having a capacity of 100 liters was used, and the fermentation temperature was 55 ° C. In addition, a deaeration unit having a capacity of 1 liter is used as the deaeration unit 14, and 0.5 L of the fermentation liquid from the methane fermentation tank 11 is caused to flow into the deaeration unit 14, and the air flow rate from the blower 25 is 3 L / L / min. The deaeration process was carried out. As an electrical conductivity meter, a conductivity meter ES-51 manufactured by HORIBA was used.

  Deaeration treatment is performed by the above method, FIG. 15 shows the electrical conductivity in the deaeration unit 14 and the methane fermentation tank, and FIG. 16 shows the ammonia gas in the deaeration unit 14 and the methane fermentation tank obtained by ion chromatography. The change in concentration with time is shown in Table 8 with detailed numerical values.

  From the results shown in FIG. 16 and Table 8, the deaeration method can remove ammonia in the fermentation solution almost completely in 2 hours, and the electrical conductivity of the deaeration part after 2 hours from the deaeration process By obtaining the difference from the electrical conductivity in the methane fermenter, the ammonia nitrogen concentration in the fermenter can be monitored, and by controlling the electrical conductivity difference to be 9 mS / cm or less, stable A methane fermentation state can be maintained.

Example 5
Using the treatment apparatus as shown in FIG. 10, continuous operation was performed using the methane fermentation treatment method of the present invention. As the methane fermenter 11, a fermenter having a capacity of 100 liters was used, and the fermentation temperature was 55 ° C. Moreover, the deaeration part 14 used the 1-liter capacity | capacitance deaeration part, and performed the deaeration process on the same conditions as Example 4. FIG. As an electrical conductivity meter, a conductivity meter ES-51 manufactured by HORIBA was used.

  From Example 4, the degassing treatment under conditions of 0.5 L of fermentation broth and air flow rate of 3 L / L / min can remove ammonia nitrogen in the fermentation broth almost completely in 2 hours. The fermentation broth in the deaeration part was exchanged.

  FIG. 17 shows the change in electrical conductivity in the deaeration unit 14. Table 9 shows the detailed numerical values.

  Since the fermented liquor after 2 hours of deaeration has almost completely removed ammoniacal nitrogen, measure the electrical conductivity of the deaerated part immediately after charging the fermented liquid and after 2 hours, and determine the difference. Therefore, the ammonia nitrogen concentration in the methane fermentation tank can be monitored, and a stable methane fermentation state can be maintained by controlling the electrical conductivity difference to be 9 mS / cm or less. Moreover, since it is the structure which replaces and observes a fermented liquid every 2 hours, it can always observe the ammoniacal nitrogen concentration in a methane fermenter.

  The methane fermentation treatment method of the present invention is suitably used for treating organic waste such as manure, raw garbage, and food processing residue.

It is a schematic block diagram which shows one Embodiment (i) of the methane fermentation processing apparatus used for this invention. It is a flowchart figure which shows the arithmetic processing in PLC40. It is the graph which calculated | required the correlation of electrical conductivity and ammonia nitrogen concentration. It is a schematic block diagram which shows embodiment (ii) of the methane fermentation processing apparatus used for this invention. It is a flowchart figure which shows the arithmetic processing in PLC41. It is a schematic block diagram which shows embodiment (iii) of the methane fermentation processing apparatus used for this invention. It is a flowchart figure which shows the arithmetic processing in PLC42. It is a schematic block diagram which shows embodiment (iv) of the methane fermentation processing apparatus used for this invention. It is a flowchart figure which shows the arithmetic processing in PLC43. It is a schematic block diagram which shows embodiment (v) of the methane fermentation processing apparatus used for this invention. It is a flowchart figure which shows the arithmetic processing in PLC44. It is the graph which measured the time-dependent change of the difference of the electrical conductivity in Example 1, and the ammonia nitrogen concentration in a methane fermenter. It is the graph which measured the time-dependent change of the difference of the electrical conductivity in Example 2, and the ammonia nitrogen concentration in a methane fermenter. It is the graph which measured the time-dependent change of the difference of the electrical conductivity in Example 3, and the ammonia nitrogen concentration in a methane fermenter. It is the graph which measured the time-dependent change of the electrical conductivity in the deaeration part in Example 4, and a methane fermentation tank. It is the graph which measured the time-dependent change of the ammonia nitrogen concentration in the deaeration part in Example 4, and a methane fermentation tank. 6 is a graph obtained by measuring a change with time in electrical conductivity in a deaeration part in Example 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Slurry adjustment tank 11 Methane fermentation tank 12 Waste liquid processing tank 13 Tap water tank 14 Deaeration part 21 Slurry supply pump 22 Treatment liquid circulation pump 23 Slurry extraction pump 24 Supply pump 25 Blower 30, 31, 32, 33 Electrical conductivity meter 40 41, 42, 43, 44, PLC (programmable logic controller)
35 Ion meter

Claims (9)

Methane to be processed in a waste liquid treatment tank in which organic waste is slurried in a slurry adjustment tank, put into a methane fermentation tank, fermented with methane by anaerobic microorganisms, taken out as a fermentation liquid, and this fermentation liquid is denitrified. In the fermentation treatment method,
At least the electrical conductivity in the methane fermentation tank is measured, and when the measured value of the fermentation tank is equal to or greater than a predetermined value, means for lowering the electrical conductivity in the methane fermentation tank is provided. .   The methane fermentation treatment method according to claim 1, wherein, when the measured value of the fermenter is 14 mS / cm or more, means for lowering the electrical conductivity in the methane fermenter is applied.   The electrical conductivity in the methane fermentation tank and the electrical conductivity in the slurry adjustment tank are measured, and the difference between the fermentation tank measurement value and the adjustment tank measurement value which is the electrical conductivity in the slurry adjustment tank. The methane fermentation treatment method according to claim 1, wherein when the value is equal to or greater than a predetermined value, means for lowering electrical conductivity in the methane fermentation tank is applied.   The difference between the fermenter measurement value obtained by measuring the electrical conductivity in the methane fermentation tank and the adjustment tank measurement value which is the electrical conductivity in the slurry adjustment tank obtained from the slurry salt concentration in the slurry adjustment tank is predetermined. The methane fermentation treatment method according to claim 1, wherein means for lowering the electrical conductivity in the methane fermentation tank is applied when the value is equal to or greater than the value.   The electrical conductivity in the methane fermentation tank and the electrical conductivity in the waste liquid treatment tank are measured, the measured value of the methane fermentation tank, and the measured value of the waste liquid treatment tank that is the electrical conductivity in the waste liquid treatment tank; The methane fermentation treatment method according to claim 1, wherein means for lowering the electrical conductivity in the methane fermenter is applied when the difference is equal to or greater than a predetermined value. In a methane fermentation treatment method in which organic waste is slurried in a slurry adjustment tank and charged into a methane fermentation tank, methane-fermented by anaerobic microorganisms, taken out as a fermentation liquid, and processed in a waste liquid treatment tank.
The electrical conductivity in the methane fermenter and a part of the fermented liquor are taken out from the methane fermenter, flow into the deaeration part, and after measuring the electrical conductivity in the deaeration part after the deaeration treatment, the waste liquid 2. The methane according to claim 1, wherein the methane is fed to a treatment tank, and when the difference between the measured value of the methane fermentation tank and the measured value of the degassed part is equal to or greater than a predetermined value, means for lowering electrical conductivity in the methane fermentation tank is provided. Fermentation processing method. In a methane fermentation treatment method in which organic waste is slurried in a slurry adjustment tank and charged into a methane fermentation tank, methane-fermented by anaerobic microorganisms, taken out as a fermentation liquid, and processed in a waste liquid treatment tank.
After removing a part of the fermented liquid from the methane fermentation tank and putting it into the deaeration part, it is sent to the waste liquid treatment tank, and the electrical conductivity of the deaeration part before and after the deaeration process is measured. A method for methane fermentation treatment, characterized in that means for lowering the electrical conductivity in the methane fermentation tank is applied when the difference between measured values before and after detreatment is greater than or equal to a predetermined value.   The methane fermentation treatment method according to any one of claims 3 to 7, wherein when the difference between the measured values is 9 mS / cm or more, a means for lowering the electrical conductivity in the methane fermentation tank is applied. The method according to any one of claims 1 to 8, wherein treated water in the waste liquid treatment tank or supplied water from the outside is supplied as dilution water into the methane fermentation tank as means for lowering the electrical conductivity in the methane fermentation tank. The methane fermentation processing method as described in one.