JP2005087853A - Method and apparatus for treating methane fermentation waste liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an inexpensive and compact apparatus for treating methane fermentation waste liquid, by each of which the methane fermentation waste liquid can be nitrified/denitrified efficiently by adding an absolute minimum amount of a hydrogen donor according to the property/state of the methane fermentation waste liquid and in each of which surplus organic matter in a methane fermentation system can be used effectively as the hydrogen donor. <P>SOLUTION: The amount of the organic matter to be added to the methane fermentation waste liquid as the hydrogen donor is adjusted on the basis of the value calculated from a value of the measured ammonia nitrogen concentration of the methane fermentation waste liquid and the charging amount of the methane fermentation waste liquid. A value of the nitrate nitrogen concentration when a methane fermentation waste liquid nitrifying step is completed can be used instead of the value of the ammonia nitrogen concentration. It is preferable to use a solution obtained by solubilizing waste sludge physicochemically or a filtrate obtained by subjecting the organic waste to be subjected to methane fermentation to solid-liquid separation as the organic matter to be added as the hydrogen donor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and a processing apparatus for efficiently and low-cost nitrification denitrification treatment of nitrogen compounds such as ammonia contained in methane fermentation waste liquid discharged when methane fermentation treatment is performed on organic waste such as straw.

  Conventionally, as one method for treating organic waste such as straw and livestock waste, methane fermentation is performed using anaerobic bacteria and the like, and digestive waste liquid discharged after methane fermentation (in the present invention, methane There is known a methane fermentation treatment system for purifying a fermentation waste liquor).

  In the purification treatment of methane fermentation waste liquid in this methane fermentation treatment system, it is necessary not only to remove organic substances contained in the methane fermentation waste liquid but also to remove high-concentration nitrogen compounds. In general, a biological nitrification denitrification treatment method is known as a method for removing nitrogen compounds from methane fermentation waste liquid. This biological nitrification denitrification process consists of a nitrification process in which ammonia nitrogen contained in methane fermentation wastewater is converted to nitrite nitrogen or nitrate nitrogen by the action of nitrifying bacteria under aerobic conditions, and the produced nitrite nitrogen Alternatively, it consists of a denitrification step in which nitrate nitrogen is reduced to nitrogen gas and removed by the action of denitrifying bacteria under anaerobic conditions.

  In the above denitrification step, a hydrogen donor that supplies hydrogen for reducing nitrite nitrogen or nitrate nitrogen to nitrogen gas is required, and organic substances contained in methane fermentation waste liquid are usually used as hydrogen donors. Is done. In addition, since the organic matter is also necessary as an energy source for denitrifying bacteria, an appropriate amount of the organic matter must remain in the methane fermentation waste liquid in order to efficiently perform the denitrification step.

  In general, in order to efficiently perform biological nitrification denitrification treatment, about three times as much organic matter as nitrogen to be removed is required, but methane fermentation waste liquid consumes a lot of organic matter in the methane fermentation process, Since there are not enough organic substances necessary for nitrogen removal, the denitrification reaction does not proceed, resulting in poor nitrogen removal.

  Therefore, in the conventional methane fermentation treatment apparatus as shown in FIG. 3, methanol is added as an organic substance to the methane fermentation waste liquid, and this methanol is used as a hydrogen donor to efficiently advance the denitrification reaction. As shown in FIG. 3, the organic waste is slurried by removing plastics and metals from the pulverizing / separating machine 1, and then charged into the methane fermentation tank 3 by the transfer pump 2. Methane fermentation treatment is performed while circulating. Biogas generated by methane 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 and a gas engine, or boiler.

  The methane fermentation waste liquid discharged from the methane fermentation tank 3 is charged into the waste liquid treatment tank 5 and aerated by the aeration device 6 while being stirred by the stirrer 7, thereby performing nitrification denitrification treatment. At that time, methanol is added from the methanol storage tank 8 to the waste liquid treatment tank 5 by the methanol injection pump 9.

  The methane fermentation waste liquid after the nitrification denitrification treatment is sent to the membrane separation tank 10, and after the solid content (activated sludge) is separated by the membrane unit 11, it is discharged as treated water. On the other hand, the separated activated sludge is returned to the waste liquid treatment tank 5 by the sludge return pump 12, and a part of the activated sludge is discharged as excess sludge by the excess sludge discharge pump 13.

  In addition, as another method for biologically removing nitrogen compounds in wastewater, for example, in Patent Document 1 below, a nitrogen-containing substance contained in wastewater is biologically nitrified using a hydrogen donor. In a wastewater treatment method in which nitrogen treatment is performed, a wastewater treatment method is disclosed in which an organic slurry obtained by wet-grinding organic waste is used as the hydrogen donor.

  In Patent Document 2 below, in a method of treating nitrogen-containing wastewater containing NOx-N in a nitrogen removal system including a denitrification tank, the wastewater containing NOx-N is introduced into the denitrification tank and biological nitrogen is introduced. A denitrification process for denitrification, and a reforming process in which part of the biological sludge generated in the nitrogen removal system is extracted to be easily biodegradable and then introduced into the denitrification tank. In the denitrification tank, a nitrogen-containing wastewater treatment method is disclosed in which denitrification is performed so that the NOx-N concentration of the denitrification tank effluent is 5 mg-N / L or more.

Further, in Patent Document 3 below, removal of nitrate nitrogen from tap water for removing nitrate nitrogen by pressurizing and introducing treated water to the primary side of a reverse osmosis membrane that selectively permeates water. In the method, denitrifying bacteria and organic substances are added to nitrate nitrogen concentrated wastewater generated in the treatment step, and nitrate nitrogen is reduced to nitrogen gas by the reducing action of the denitrifying bacteria, and chemicals generated by washing the reverse osmosis membrane There is disclosed a method for removing nitrate nitrogen from raw tap water characterized by using washing wastewater as a source of organic matter necessary for the denitrifying bacteria.
JP 2001-29993 A JP 2002-192189 A JP 2002-18486 A

  As described above, when the nitrogen compound in the methane fermentation waste liquid is to be biologically removed, it is necessary to add an organic substance as a hydrogen donor according to the concentration of the nitrogen compound or organic substance in the methane fermentation waste liquid. If organic matter is added more than necessary, excess organic matter will remain in the treated water, or conversely, if the amount of organic matter added is insufficient, nitrification denitrification will not be performed sufficiently. Therefore, in the above conventional method, it is difficult to adjust the addition amount of the organic substance according to the concentration of the nitrogen compound or the organic substance in the methane fermentation waste liquid. In addition, in the said patent document 3, ORP (oxidation reduction potential) of the to-be-processed water in a biological denitrification reaction tank is measured, and adjusting the addition amount of methanol based on the value is described. However, in this method, since the nitrate nitrogen concentration is indirectly measured, there is a concern that the denitrification treatment cannot be performed stably due to lack of stability and reliability.

  Moreover, since methanol generally used as a hydrogen donor is expensive, there is a disadvantage that the processing cost is increased. Therefore, in the said patent document 1, the organic slurry obtained by wet-grinding organic substances, such as soot, is used as a hydrogen donor of a denitrification process. However, since this organic slurry contains a large amount of solids, the load on the processing apparatus is increased, and not only the volume of the waste liquid treatment tank needs to be increased accordingly, but also discharged from the waste liquid treatment tank. There was a drawback that the amount of activated sludge also increased.

  Therefore, the object of the present invention is to efficiently add a hydrogen donor in a minimum amount according to the properties of the methane fermentation waste liquid when biologically nitrifying and denitrifying nitrogen compounds in the methane fermentation waste liquid. Provided is a low-cost and compact methane fermentation waste liquid treatment method and treatment apparatus that can perform nitrification and denitrification treatments, and that can effectively utilize surplus organic matter in a methane fermentation system as a hydrogen donor. There is.

  In order to achieve the above object, one of the methods for treating methane fermentation waste liquid according to the present invention uses a hydrogen donor for nitrogen compounds contained in methane fermentation waste liquid discharged when methane fermentation treatment is performed on organic waste. In the method of biologically nitrifying and denitrifying, the ammonia nitrogen concentration of the methane fermentation waste liquid charged into the waste liquid treatment tank is measured, and the ammonia nitrogen concentration value and the input amount of the methane fermentation waste liquid are measured. Based on the calculated value, the amount of the organic substance added as the hydrogen donor to the methane fermentation waste liquid is adjusted.

  Further, another method for treating methane fermentation waste liquid according to the present invention is to use a hydrogen donor to convert nitrogen compounds contained in methane fermentation waste liquid discharged when organic waste is subjected to methane fermentation. In the method of nitrification denitrification, a nitrification step of converting ammonia nitrogen contained in the methane fermentation waste liquid charged into the waste liquid treatment tank into nitrite nitrogen or nitrate nitrogen under aerobic conditions is performed, and the nitrification step Measure the nitrate nitrogen concentration of the methane fermentation waste liquid at the end, and based on the value calculated from the nitrate nitrogen concentration value and the input amount of the methane fermentation waste liquid, donate the hydrogen to the methane fermentation waste liquid It is characterized by adjusting the amount of organic matter added as a body.

  According to the method of the present invention, the ammonia nitrogen concentration of the methane fermentation waste liquid charged into the waste liquid treatment tank or the nitrate nitrogen concentration of the methane fermentation waste liquid at the end of the nitrification step is measured, and this value and the input amount of the methane fermentation waste liquid By adjusting the amount of organic matter added as the hydrogen donor to the methane fermentation waste liquid based on the value calculated from Nitrogen treatment can be performed.

  In the method of the present invention, the amount of the organic substance added as the hydrogen donor is preferably calculated based on the following formulas (1) to (3).

c = a × b × 3 (kg-BOD / kgN) (1)
a: Ammonia nitrogen concentration (g / L) of the methane fermentation waste liquid charged into the waste liquid treatment tank or nitrate nitrogen concentration (g / L) at the end of the nitrification process of the methane fermentation waste liquid charged into the waste liquid treatment tank
b: Input amount of methane fermentation waste liquid to waste liquid treatment tank (L)
c: Amount of BOD component (g) required for denitrification of methane fermentation waste liquid charged into the waste liquid treatment tank

e = c− (d × b) (2)
In the above formula (2), b and c have the same meaning as described above.
d: Concentration of BOD component (g / L) contained in the methane fermentation waste liquid charged into the waste liquid treatment tank
e: Amount of BOD component (g) that is insufficient when denitrifying the methane fermentation waste liquid charged into the waste liquid treatment tank

g = e ÷ f (3)
In the above formula (3), e has the same meaning as described above.
f: BOD component concentration of organic substance used as hydrogen donor (g / L)
g: Amount of organic substance added as hydrogen donor (L)

  In the method of the present invention, as the organic substance to be added as the hydrogen donor, a solution obtained by physicochemically solubilizing excess sludge discharged from the waste liquid treatment tank or an organic waste to be subjected to methane fermentation is solidified. It is preferable to use a filtrate which has been subjected to liquid separation. According to this, since a cheap organic substance compared with methanol is used as the hydrogen donor, the running cost can be reduced. Moreover, the waste disposal cost of excess sludge can also be reduced by using the solution which solubilized the excess sludge physicochemically.

  On the other hand, one of the processing apparatuses for methane fermentation waste liquid of the present invention is an organic waste supply means for slurrying and introducing organic waste degradable by anaerobic microorganisms into a methane fermentation tank, and the organic waste A methane fermentation tank for fermenting waste, a flow rate measuring means for measuring the flow rate of the methane fermentation waste liquid discharged from the methane fermentation tank, and an ammonia nitrogen concentration of the methane fermentation waste liquid Ammonia nitrogen concentration measuring means, a waste liquid treatment tank for nitrifying and denitrifying the methane fermentation waste liquid, the ammonia nitrogen concentration of the methane fermentation waste liquid measured by the ammonia nitrogen concentration measuring means and the methane fermentation waste liquid From the input amount of the methane fermentation waste liquid to the waste liquid treatment tank measured by the flow rate measuring means, the hydrogen donor and the hydrogen donor to the methane fermentation waste liquid A calculation means for calculating the amount of organic matter to be added, and a solution obtained by physicochemically solubilizing a part of the excess sludge discharged from the waste liquid treatment tank based on the value calculated by the calculation means, Alternatively, it comprises a hydrogen donor addition means for adding a predetermined amount of the filtrate obtained by taking out a part of the organic waste subjected to methane fermentation treatment and solid-liquid separation to the waste liquid treatment tank as a hydrogen donor. And

  Further, another apparatus for treating methane fermentation waste liquid according to the present invention comprises an organic waste supply means for slurrying and introducing organic waste degradable by anaerobic microorganisms into a methane fermentation tank, A methane fermentation tank for fermenting volatile waste, a flow rate measuring means for measuring the flow rate of the methane fermentation waste liquid discharged from the methane fermentation tank, and a waste liquid for nitrifying and denitrifying the methane fermentation waste liquid A treatment tank, nitrate nitrogen concentration measuring means for measuring nitrate nitrogen concentration of methane fermentation waste liquid in the waste liquid treatment tank, and nitrate nitrogen of the methane fermentation waste liquid measured by the nitrate nitrogen concentration measurement means As the hydrogen donor to the methane fermentation waste liquid, the concentration and the amount of the methane fermentation waste liquid input to the waste liquid treatment tank measured by the methane fermentation waste liquid flow rate measuring means A computing means for computing the amount of organic matter to be added, and a solution obtained by physicochemically solubilizing a part of excess sludge discharged from the waste liquid treatment tank based on the value calculated by the computing means, or A hydrogen donor addition means for adding a predetermined amount of the filtrate obtained by taking out a part of the organic waste to be subjected to methane fermentation treatment and solid-liquid separation to the waste liquid treatment tank as a hydrogen donor. To do.

  According to the treatment apparatus of the present invention, the flow measurement means and the ammonia nitrogen concentration measurement means or the nitrate nitrogen concentration measurement means grasp the properties of the methane fermentation waste liquid subjected to nitrification denitrification treatment. The amount of hydrogen donor required for denitrifying the methane fermentation waste liquid can be accurately calculated by the calculation means. As a result, a minimum amount of hydrogen donor can be added to the methane fermentation waste liquid, and the nitrification / denitrification treatment can be performed efficiently, and the waste liquid treatment tank can be made compact.

  Further, as a hydrogen donor, a part of the excess sludge discharged from the waste liquid treatment tank is taken out and a physicochemically solubilized solution, or a part of the organic waste subjected to methane fermentation treatment is taken out as a solid liquid. Since the separated filtrate is used, the running cost can be reduced.

  According to the present invention, when the methane fermentation waste liquid is subjected to nitrification denitrification, the flow rate of the methane fermentation waste liquid to be introduced into the waste liquid treatment tank, the ammonia nitrogen concentration in the methane fermentation waste liquid, or the methane fermentation waste liquid at the end of the nitrification process. By measuring the nitrate nitrogen concentration and calculating the amount of hydrogen donor required for denitrification based on these measurements, the amount of hydrogen donor added can be minimized, so that Nitrogen treatment can be performed efficiently.

  Moreover, since the organic substance which became surplus by a methane fermentation system can be utilized effectively as a hydrogen donor, a running cost can be reduced.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a treatment apparatus that can be used in the method for treating a methane fermentation waste liquid of the present invention. In the figure, a path indicated by a broken line indicates a signal line, and a solid line indicates a flow of fluid such as waste liquid.

First, the processing apparatus of FIG. 1 includes a pulverizing and sorting machine 21 that pulverizes organic waste, a methane fermentation tank 23 that performs methane fermentation, a flow meter 25 that measures the flow rate of methane fermentation waste liquid, and ammonia nitrogen in methane fermentation waste liquid Ammonia meter 26 for measuring concentration, waste liquid treatment tank 27 for treating methane fermentation waste liquid, NO ₃ meter 30 for measuring nitrate nitrogen concentration of methane fermentation waste liquid in waste liquid treatment tank 27, separating treated water and activated sludge Membrane separation tank 31, solubilization tank 37 in which a part of excess sludge is physicochemically soluble, the amount of organic matter added as a hydrogen donor is calculated, and the amount of surplus sludge input to the solubilization tank 37 is adjusted It is mainly comprised from the arithmetic unit 35.

  The pulverization / separation machine 21 is connected to the methane fermentation tank 23 via a pipe 51, and the methane fermentation tank 23 is connected to a waste liquid treatment tank 27 via a pipe 53. In the middle of the pipe 53, a flow meter 25 and an ammonia meter 26 connected to the arithmetic unit 35 are provided, and the amount of methane fermentation waste liquid and ammonia nitrogen concentration that are put into the waste liquid treatment tank 27 are measured. Each measurement value can be transmitted to the arithmetic unit 35. In addition, the stirring pump 24 is provided in the methane fermentation tank 23 via the piping 52 in order to perform methane fermentation efficiently. The waste liquid treatment tank 27 is provided with an aeration device 28 and a stirrer 29 in order to efficiently perform the nitrification denitrification treatment.

  As the flow meter 25, any ordinary flow meter can be used without particular limitation. The ammonia meter 26 is preferably a concentration meter capable of continuous measurement. For example, a diaphragm type ammonia electrode can be used.

Further, the waste liquid treatment tank 27 is connected to the membrane separation tank 31 via a pipe 54, and a NO ₃ meter 30 connected to the arithmetic unit 35 is provided in the middle of the pipe 54. The nitrate nitrogen concentration of the methane fermentation waste liquid is measured, and the measured value can be transmitted to the arithmetic unit 35.

The NO ₃ meter 30 is preferably a concentration meter capable of continuous measurement. For example, an ultraviolet absorption nitrate nitrogen concentration meter or an ion electrode can be used.

  A membrane unit 32 is installed in the membrane separation tank 31, and a pipe 58 for discharging the separated filtrate as treated water and a pipe 55 for discharging a part of the separated activated sludge as excess sludge. Is provided. A pipe 56 branched from the pipe 55 is connected to the solubilization tank 37 so that a part of the excess sludge can be introduced into the solubilization tank 37 by the excess sludge transfer pump 36. Further, the membrane separation tank 31 is connected to the waste liquid treatment tank 27 via a pipe 58 so that the separated activated sludge can be returned to the waste liquid treatment tank 27 by the sludge return pump 33.

  The membrane unit 32 only needs to be capable of solid-liquid separation of nitrified and denitrified methane fermentation waste liquor. For example, an MF (microfiltration) membrane can be used.

  The surplus sludge transfer pump 36 is connected to the calculation device 35, and the operation time can be controlled by a signal from the calculation device 23. Here, the arithmetic unit 35 is necessary for removing nitrogen compounds in the methane fermentation waste liquid from the amount of the methane fermentation waste liquid charged into the waste liquid treatment tank 27 and the value of the ammonia nitrogen concentration or the nitrate nitrogen concentration. It is programmed to calculate the amount of organic matter and adjust the amount of excess sludge to be introduced into the solubilization tank 25 by controlling the operating time of the excess sludge transfer pump 36 based on the result.

  The solubilization tank 37 is connected to the waste liquid treatment tank 27 via a pipe 57 so that a solution obtained by physicochemically solubilizing excess sludge can be added to the waste liquid treatment tank 27. In order to solubilize excess sludge physicochemically, the solubilization tank 37 is provided with, for example, ozone addition means, heating means, and the like. In addition, the physicochemical solubilization of surplus sludge as used in the present invention means that the cell walls of microorganisms in the surplus sludge are broken and solubilized.

  Next, the processing method of the methane fermentation waste liquid of this invention using this processing apparatus is demonstrated. As shown in FIG. 1, organic waste such as soot is finely pulverized by a pulverization / separation device 21 and foreign matter such as plastic that is not suitable for fermentation is separated and removed. It is put into a slurry and adjusted to a solid content concentration suitable for methane fermentation (usually a solid concentration of 10 to 20% by mass).

  The slurried organic waste (organic slurry) is put into the methane fermentation tank 23 by the transfer pump 22 to perform methane fermentation. The methane fermentation tank 23 is provided with an agitation pump 24, whereby the organic slurry in the methane fermentation tank is circulated and agitated. And the biogas produced | generated by fermentation is collect | recovered by the gas holder which is not shown in figure, and is effectively utilized as fuel of generators, such as a fuel cell power generation device and a gas engine, and a boiler.

  The methane fermentation tank 23 is provided with a fixed filter bed or the like filled with immobilized microorganisms to which anaerobic microorganisms such as methane bacteria are attached and supported. Here, methane fermentation of the organic slurry is performed, and anaerobic is performed. Organic waste is decomposed by microorganisms. It is preferable to perform the temperature in methane fermentation at 50-60 degreeC. According to this, since it is possible to perform fermentation with a more active high-temperature methane bacterium, the decomposition rate of organic waste can be further improved.

  The methane fermentation waste liquid discharged from the methane fermentation tank 11 is put into the waste liquid treatment tank 27 in order to remove nitrogen compounds. At this time, an organic substance (a solution obtained by physicochemically solubilizing excess sludge) in an amount necessary for denitrifying nitrogen compounds in the methane fermentation waste liquid is also added at the same time.

In the present invention, when the methane fermentation waste liquid is introduced into the waste liquid treatment tank 27, the input amount of the methane fermentation waste liquid and the ammonia nitrogen concentration are measured by the flow meter 25 and the ammonia meter 30 and transmitted to the arithmetic unit 35. The amount of organic matter necessary for denitrifying nitrogen compounds in the methane fermentation waste liquid is calculated. Note that the nitrate nitrogen concentration measured by the NO ₃ meter 30 can be used instead of the ammonia nitrogen concentration.

  Calculation of the amount of organic matter necessary for denitrifying nitrogen compounds in the methane fermentation waste liquid is specifically performed based on the following formulas (1) to (3).

c = a × b × 3 (kg-BOD / kgN) (1)
a: Ammonia nitrogen concentration (g / L) of the methane fermentation waste liquid charged into the waste liquid treatment tank or nitrate nitrogen concentration (g / L) at the end of the nitrification process of the methane fermentation waste liquid charged into the waste liquid treatment tank
b: Input amount of methane fermentation waste liquid to waste liquid treatment tank (L)
c: Amount of BOD component (g) required for denitrification of methane fermentation waste liquid charged into the waste liquid treatment tank

e = c− (d × b) (2)
In the above formula (2), b and c have the same meaning as described above. D: Concentration of BOD component (g / L) contained in the methane fermentation waste liquid charged into the waste liquid treatment tank
e: Amount of BOD component (g) that is insufficient when denitrifying the methane fermentation waste liquid charged into the waste liquid treatment tank

g = e ÷ f (3)
In the above formula (3), e has the same meaning as described above.
f: BOD component concentration of organic substance used as hydrogen donor (g / L)
g: Amount of organic substance added as hydrogen donor (L)

That is, in the above formula (1), the parameter a is the ammonia nitrogen concentration or nitrate nitrogen concentration measured by the ammonia meter 30 or the NO ₃ meter 30, and the parameter b is methane fermentation measured by the flow meter 25. The amount of waste liquid input. Then, the total amount (c) of the BOD (biological oxygen demand) component necessary for denitrification of the methane fermentation waste liquid is obtained by the above formula (1). In the present invention, the BOD component means an organic substance that can be decomposed by aerobic microorganisms in water.

  Next, the amount of the BOD component that is insufficient when denitrifying the methane fermentation waste liquid charged into the waste liquid treatment tank, that is, the amount of the BOD component to be added to the methane fermentation waste liquid is obtained by the above formula (2).

  And the quantity of the organic substance actually added to a methane fermentation waste liquid is calculated | required by the said Formula (3).

  Based on the value calculated by the above formula, the arithmetic unit 35 controls the operating time of the excess sludge transfer pump 36 and a predetermined amount of excess sludge is charged into the solubilization tank 37. The excess sludge charged into the solubilization tank 37 is solubilized in the tank and then charged into the waste liquid treatment tank 27. For example, when solubilization of excess sludge is performed by heating, it can be performed by heating at 80 to 100 ° C. for 1 to 2 hours.

  The waste liquid treatment tank 27 contains activated sludge containing nitrifying bacteria, denitrifying bacteria, and the like, and the methane fermentation waste liquid to which a predetermined amount of organic matter is added is intermittently aerated by the aeration apparatus 28 to be anaerobic and aerobic. By repeating the state alternately, under aerobic conditions, ammonia nitrogen contained in methane fermentation waste liquid is nitrified by nitrifying bacteria and converted into nitrite nitrogen or nitrate nitrogen, and the produced nitrite nitrogen or nitrate Nitrogen is reduced to nitrogen gas by denitrifying bacteria using the organic matter in the methane fermentation wastewater as a hydrogen donor under anaerobic conditions and released to the atmosphere. The methane fermentation waste liquid is put into the waste liquid treatment tank 27 in an anaerobic state, and is usually anaerobic state for 0.5 to 1.5 hours and an aerobic state for 1.5 to 0.5 at 10 to 35 ° C. While repeating the time alternately, the sample is retained in the waste liquid treatment tank 27 for 5 to 10 days, and biological nitrification denitrification treatment is performed.

  The methane fermentation waste liquid that has been subjected to nitrification and denitrification is discharged from the waste liquid treatment tank 27, sent to the membrane separation tank 12, and after the solid content (activated sludge) is separated by the membrane unit 13, the filtrate is treated water. As discharged. On the other hand, the separated activated sludge is returned again to the waste liquid treatment tank 27, but a part of the activated sludge is introduced into the solubilization tank 37 as the excess sludge as described above, or is removed from the system by the excess sludge discharge pump 34. It is discharged, and after disposal such as dehydration, it is disposed of as waste.

  FIG. 2 shows a schematic configuration diagram of another processing apparatus that can be used in the method for processing a methane fermentation waste liquid of the present invention. In the following description, parts that are basically the same as those in FIG.

  In the treatment apparatus of FIG. 2, as a hydrogen donor addition means, instead of the solubilization tank 37 that physically solubilizes a part of the excess sludge transfer pump 36 and the excess sludge, dehydration that separates the organic slurry into solid and liquid is performed. It differs from the processing apparatus shown in FIG. 1 in that it has a machine 38, a filtrate tank 39 for storing filtrate of organic slurry, and a filtrate transfer pump 40.

  The pulverizing / separating machine 21 is connected to the methane fermentation tank 23 via a pipe 60, and a pipe 61 branched in the middle is connected to a dehydrator 38. The methane fermentation tank 23 is connected to the waste liquid treatment tank 27 via a pipe 64. In the middle of the pipe 64, a flow meter 25 and an ammonia meter 26 connected to the arithmetic unit 35 are provided, and the amount of methane fermentation waste liquid and ammonia nitrogen concentration to be introduced into the waste liquid treatment tank 27 are measured and calculated. Each measurement value can be transmitted to the device 35.

The waste liquid treatment tank 27 is connected to the membrane separation tank 31 via a pipe 65, and a NO ₃ meter 30 connected to the arithmetic unit 35 is provided in the middle of the pipe 65. The nitrate nitrogen concentration of the methane fermentation waste liquid is measured, and the measured value can be transmitted to the arithmetic unit 35.

  A membrane unit 32 is installed in the membrane separation tank 31, and a pipe 67 for discharging the separated filtrate as treated water and a pipe 66 for discharging a part of the separated activated sludge as excess sludge. Is provided. Further, the membrane separation tank 31 is connected to the waste liquid treatment tank 27 through a pipe 68 so that the separated activated sludge can be returned to the waste liquid treatment tank 27 by the sludge return pump 33.

  In this apparatus, the filtrate separated by the dehydrator 38 is stored in the filtrate tank 39 and can be introduced into the waste liquid treatment tank 27 through the pipe 69 by the filtrate transfer pump 40. The filtrate transfer pump 40 is connected to the calculation device 35, and the operation time can be controlled by the calculation device. On the other hand, the separated solid matter is returned to the pulverizing / separating machine 21 through the pipe 62.

  The dehydrator 38 only needs to be capable of solid-liquid separation of the organic slurry. For example, a centrifugal dehydrator or a screw press dehydrator can be used.

  Next, the processing method of the methane fermentation waste liquid of this invention using this processing apparatus is demonstrated. As shown in FIG. 2, organic waste such as soot is finely pulverized by a pulverization / separation device 21 and foreign matter such as plastic that is unsuitable for fermentation is separated and removed. It is put into a slurry.

  The organic slurry is put into the methane fermentation tank 23 by the transfer pump 22 and methane fermentation is performed. The biogas generated by the fermentation is collected in a gas holder (not shown), and a generator such as a fuel cell power generator or a gas engine. It has come to be used effectively as fuel for boilers and boilers.

  A part of the organic slurry is sent to the dehydrator 38 for solid-liquid separation. The separated filtrate containing no solid content is stored in the filtrate tank 39, and the separated solid content is returned to the pulverization / separator 21.

  The methane fermentation waste liquid discharged from the methane fermentation tank 11 is put into the waste liquid treatment tank 27 in order to remove nitrogen compounds. At this time, an amount of organic matter (filtrate obtained by solid-liquid separation of an organic slurry as a raw material for methane fermentation) necessary for denitrifying nitrogen compounds in the methane fermentation waste liquid is also added at the same time.

In the present invention, when the methane fermentation waste liquid is introduced into the waste liquid treatment tank 27, the input amount of the methane fermentation waste liquid and the ammonia nitrogen concentration are measured by the flow meter 25 and the ammonia meter 30 and transmitted to the arithmetic unit 35. As described above, the amount of organic matter necessary to denitrify the nitrogen compound in the methane fermentation waste liquid is calculated. Note that the nitrate nitrogen concentration measured by the NO ₃ meter 30 can be used instead of the ammonia nitrogen concentration.

  Then, based on the calculated value, the arithmetic unit 35 controls the operating time of the filtrate transfer pump 40, and a predetermined amount of filtrate is put into the waste liquid treatment tank 27.

  The methane fermentation waste liquid that has been subjected to nitrification and denitrification is discharged from the waste liquid treatment tank 27, sent to the membrane separation tank 12, and after the solid content (activated sludge) is separated by the membrane unit 13, the filtrate is treated water. As discharged. On the other hand, the separated activated sludge is returned again to the waste liquid treatment tank 27, but a part of the activated sludge is discharged out of the system by the surplus sludge discharge pump 34 as surplus sludge, and after being subjected to treatment such as dehydration, as waste Will be disposed of.

  By performing such an apparatus configuration and operation, surplus sludge that has been disposed of as waste in the past can be used instead of expensive methanol that is generally used as a hydrogen donor for biological nitrification denitrification. A solubilized solution or a filtrate of an organic slurry that is a raw material for methane fermentation can be used, and the running cost can be reduced. In addition, the amount of addition is calculated based on the amount of methane fermentation waste liquid and the measured value of ammonia nitrogen concentration or nitrate nitrogen concentration, so the minimum amount of organic substances that can remove nitrogen compounds contained in methane fermentation waste liquid Therefore, it is possible to efficiently perform nitrification / denitrification treatment, and it is not necessary to treat excess organic matter in a waste liquid treatment tank. Therefore, the volume of the waste liquid treatment tank can be made compact.

  By the processing apparatus having the configuration shown in FIG. 2, the methane fermentation treatment of organic waste containing cow manure and raw garbage was performed using the method for treating a methane fermentation treatment waste liquid of the present invention. In addition, methane fermentation was performed at 55 degreeC and the residence time in the methane fermentation tank 23 was 10 days.

The methane fermentation waste liquid discharged from the methane fermentation tank 23 is charged into the waste liquid treatment tank 27 at a flow rate of 100 m ³ / day, and at the same time, the filtrate obtained by solid-liquid separation of the organic slurry (BOD concentration 98,000 mg / day). L) was added at 2.86 m ³ / day for nitrification denitrification treatment. Table 1 shows the properties of the methane fermentation waste liquid.

  The input amount of the filtrate is calculated based on the above formulas (1) to (3). Further, the nitrification denitrification treatment was performed at 20 ° C., and the nitrification denitrification treatment was held in the waste liquid treatment tank 27 for 10 days while intermittently aeration was performed by the aeration apparatus 28.

The methane fermentation waste liquid that has been subjected to the nitrification and denitrification treatment discharged from the waste liquid treatment tank 27 is sent to the membrane separation tank 12, and the solid content (activated sludge) remaining is separated by the membrane unit 13. Discharged (100 m ³ / day). Table 2 shows the properties of the treated water.

  From Table 2, it can be seen that organic substances and nitrogen compounds in the methane fermentation waste liquid are sufficiently removed.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for removing organic substances and nitrogen compounds in methane fermentation waste liquid discharged when methane fermentation treatment is performed on organic waste such as manure, raw garbage, and food processing residue using anaerobic microorganisms. .

It is a schematic block diagram which shows one Embodiment of the processing apparatus of the methane fermentation waste liquid of this invention. It is a schematic block diagram which shows another embodiment of the processing apparatus of the methane fermentation waste liquid of this invention. It is a schematic block diagram of the conventional methane fermentation processing apparatus.

Explanation of symbols

21. Crushing and sorting machine 22. Transfer pump 23. Methane fermentation tank 24. Stirring pump 25. Flow meter 26. Ammonia meter 27. Waste liquid treatment tank 28. Aeration device 29. Agitator 30. NO ₃ total 31. Membrane separation tank 32. Membrane unit 33. Sludge return pump 34. Excess sludge discharge pump 35. Arithmetic device 36. Surplus sludge transfer pump37. Solubilization tank 38. Dehydrator 39. Filtrate tank 40. Filtrate transfer pump

Claims (7)

In a method of biologically nitrifying and denitrifying nitrogen compounds contained in methane fermentation waste liquid discharged when methane fermentation treatment of organic waste is performed using a hydrogen donor,
Measure the ammonia nitrogen concentration of the methane fermentation waste liquid charged into the waste liquid treatment tank, and based on the value calculated from the ammonia nitrogen concentration value and the input amount of the methane fermentation waste liquid, A method for treating a waste liquid of methane fermentation, comprising adjusting an amount of an organic substance added as the hydrogen donor. In a method of biologically nitrifying and denitrifying nitrogen compounds contained in methane fermentation waste liquid discharged when methane fermentation treatment of organic waste is performed using a hydrogen donor,
Performing a nitrification step of converting ammonia nitrogen contained in the methane fermentation waste solution charged into the waste liquid treatment tank into nitrite nitrogen or nitrate nitrogen under aerobic conditions, and nitric acid of the methane fermentation waste solution at the end of the nitrification step The amount of organic matter added to the methane fermentation waste liquid as the hydrogen donor is adjusted based on the value calculated from the nitrate nitrogen concentration value and the input amount of the methane fermentation waste liquid. A method for treating methane fermentation wastewater, characterized in that: The processing method of the methane fermentation waste liquid of Claim 1 or 2 which calculates the quantity of the organic substance added as the said hydrogen donor based on following formula (1)-(3).
c = a × b × 3 (kg-BOD / kgN) (1)
a: Ammonia nitrogen concentration (g / L) of the methane fermentation waste liquid charged into the waste liquid treatment tank or nitrate nitrogen concentration (g / L) at the end of the nitrification process of the methane fermentation waste liquid charged into the waste liquid treatment tank
b: Input amount of methane fermentation waste liquid to waste liquid treatment tank (L)
c: Amount of BOD component (g) required for denitrification of methane fermentation waste liquid charged into the waste liquid treatment tank
e = c− (d × b) (2)
In the above formula (2), b and c have the same meaning as described above. D: Concentration of BOD component (g / L) contained in the methane fermentation waste liquid put into the waste liquid treatment tank
e: Amount of BOD component (g) that is insufficient when denitrifying the methane fermentation waste liquid charged into the waste liquid treatment tank
g = e ÷ f (3)
In the above formula (3), e has the same meaning as described above. F: BOD component concentration (g / L) of organic substance used as a hydrogen donor
g: Amount of organic substance added as hydrogen donor (L)   The treatment of methane fermentation waste liquid according to any one of claims 1 to 3, wherein a solution obtained by physicochemically solubilizing excess sludge discharged from the waste liquid treatment tank is used as the organic substance added as the hydrogen donor. Method.   The processing method of the methane fermentation waste liquid as described in any one of Claims 1-3 using the filtrate which solid-liquid-separated the organic waste to which a methane fermentation process is carried out as an organic substance added as the said hydrogen donor. Organic waste supply means for slurrying and introducing organic waste degradable by anaerobic microorganisms into a methane fermentation tank,
A methane fermenter for methane fermentation of the organic waste,
Flow rate measuring means for measuring the flow rate of the methane fermentation waste liquid discharged from the methane fermentation tank;
Ammonia nitrogen concentration measuring means for measuring the ammonia nitrogen concentration of the methane fermentation waste liquid;
A waste liquid treatment tank for nitrifying and denitrifying the methane fermentation waste liquid;
From the ammonia nitrogen concentration of the methane fermentation waste liquid measured by the ammonia nitrogen concentration measuring means and the input amount of the methane fermentation waste liquid into the waste liquid treatment tank measured by the methane fermentation waste liquid flow rate measuring means Computing means for computing the amount of organic matter added to the waste liquid as the hydrogen donor;
Based on the value calculated by the calculation means, a part of the surplus sludge discharged from the waste liquid treatment tank is taken out and physicochemically solubilized, or part of the organic waste subjected to methane fermentation An apparatus for treating methane fermentation waste liquid, comprising: a hydrogen donor addition means for adding a predetermined amount of the filtrate obtained by taking out the solid and separating it into the waste liquid treatment tank as a hydrogen donor. Organic waste supply means for slurrying and introducing organic waste degradable by anaerobic microorganisms into a methane fermentation tank,
A methane fermenter for methane fermentation of the organic waste,
Flow rate measuring means for measuring the flow rate of the methane fermentation waste liquid discharged from the methane fermentation tank;
A waste liquid treatment tank for nitrifying and denitrifying the methane fermentation waste liquid;
Nitrate nitrogen concentration measuring means for measuring nitrate nitrogen concentration of methane fermentation waste liquid in the waste liquid treatment tank;
From the nitrate nitrogen concentration of the methane fermentation waste liquid measured by the nitrate nitrogen concentration measuring means and the input amount of the methane fermentation waste liquid into the waste liquid treatment tank measured by the methane fermentation waste liquid flow rate measuring means Computing means for computing the amount of organic matter added to the waste liquid as the hydrogen donor;
Based on the value calculated by the calculation means, a part of the surplus sludge discharged from the waste liquid treatment tank is taken out and physicochemically solubilized, or part of the organic waste subjected to methane fermentation An apparatus for treating methane fermentation waste liquid, comprising: a hydrogen donor addition means for adding a predetermined amount of the filtrate obtained by taking out the solid and separating it into the waste liquid treatment tank as a hydrogen donor.

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