JP2006075730A - Anaerobic treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably reduce the amount of organic components and to recover a large amount of methane gas even under a higher organic matter load compared with the conventional case by increasing the efficiency of anaerobic digestion treatment, and even in treatment for an organic waste liquid containing a large amount of inorganic components by preventing the storage of inorganic matters to an anaerobic digestion tank. <P>SOLUTION: The anaerobic digestion device is provided with: an anaerobic digestion tank 1 of subjecting an organic waste liquid to anaerobic digestion treatment; a solid-liquid separation means 3 of subjecting the digestion-treated liquid in the anaerobic digestion tank 1 to solid-liquid separation and discharging at least a part of the separated liquid to the outside of the system; a sludge returning means of returning the concentrated sludge separated by the solid-liquid separation means 3 to the anaerobic digestion tank 1; a sludge reforming means 4 of subjecting the digested sludge formed in the anaerobic digestion tank 1 to reforming treatment; and a reformed sludge returning means of returning the reformed sludge in the sludge reforming means 4 to the anaerobic digestion tank 1. The treatment temperature in the anaerobic digestion tank 1 is 45 to 60°C, and an inorganic component elution means 2 of mixing the digestion-treated liquid with dilution water, eluting inorganic components into water and thereafter feeding the same to the solid-liquid separation means 3 is included. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an anaerobic digester that treats organic effluent by methane fermentation in the presence of sludge containing anaerobic microorganisms, and in particular, anaerobic digestion significantly reduces the amount of organic components and more The present invention relates to an anaerobic treatment apparatus capable of recovering methane gas.

  The anaerobic digestion method that treats slurry-like high-concentration organic effluents such as organic sludge, human waste, and food wastewater by methane fermentation in the presence of anaerobic microorganisms is effectively used from the effluent at the same time as the effluent treatment. This method has been used for a long time as a method for recovering possible methane gas.

  In such anaerobic digestion treatment, sludge (digested sludge) mainly composed of undegraded substances and anaerobic microorganisms is generated. Conventionally, the produced sludge is treated by incineration, landfill, etc. after mechanical dehydration.

  As a device capable of reducing the volume of sludge produced by anaerobic digestion treatment and recovering more methane gas from organic waste liquid, JP-A-9-206785 discloses that after digestion sludge is modified by ozone treatment An anaerobic digester that returns this modified sludge to an anaerobic digester is described. In this device, digested sludge is treated with ozone to improve biodegradability, then returned to the anaerobic digester and further decomposed as a substrate for anaerobic microorganisms, and more methane gas is removed from the organic effluent. It is an effective device for recovery.

  In this equipment, in order to increase the recovery rate of methane gas, it is necessary to increase the amount of sludge to be reformed while maintaining the sludge residence time in the anaerobic digestion tank so as not to reduce the efficiency of the anaerobic digestion treatment. is there. For this purpose, a part of the digested sludge is separated into solid and liquid, the separated liquid is discharged as treated water, and the separated high-concentration sludge (concentrated sludge) is returned to the anaerobic digestion tank. It is necessary to suppress outflow from the system and keep the sludge retention and sludge concentration in the anaerobic digestion tank high.

However, the apparatus for returning the concentrated sludge separated into solid and liquid to the anaerobic digester as described above has the following problems.
(1) When the sludge concentration in the anaerobic digestion tank increases, the viscosity of the liquid in the tank increases rapidly, so that the inside of the anaerobic digestion tank is not sufficiently stirred and mixed, and the efficiency of the anaerobic digestion decreases. . Therefore, in the medium temperature anaerobic digestion treatment which is widely used in anaerobic digestion treatment of sewage sludge and is performed by heating the inside of the anaerobic digestion tank to 30 to 38 ° C., the sludge concentration in the tank is within a certain range (5 It is necessary to draw out the digested sludge as surplus sludge so as to maintain it at ˜6% or less), and the higher the organic load in the anaerobic digester, the more the organic component is reduced and the recovery of methane gas is restricted.
(2) While organic components in sludge are reduced and recovered as methane gas, inorganic components migrate into the liquid by digestion, but are not decomposed like organic components and dissolve in the liquid Most of the inorganic components are re-deposited in the anaerobic digester, except for a small part. When the sludge is separated into solid and liquid, the separated liquid is discharged out of the system, and the concentrated sludge is returned to the anaerobic digester, the inorganic components accumulate in the anaerobic digester and increase the sludge concentration. When the concentration of sludge in the anaerobic digestion tank increases, the viscosity of the liquid in the tank increases rapidly, so that the inside of the anaerobic digestion tank is not sufficiently stirred and mixed, and the efficiency of the anaerobic digestion decreases. For this reason, it is necessary to appropriately extract the digested sludge as excess sludge so as to maintain the sludge concentration in the anaerobic digester within a certain range (5 to 6% or less). And by extracting the sludge to prevent the accumulation of inorganic components, the organic components that should have been reduced and recovered as methane gas are extracted and contained in the sludge and discharged out of the system. And the recovery of methane gas is limited.
JP-A-9-206785

  The present invention solves the above-mentioned conventional problems and increases the efficiency of the anaerobic digestion treatment, thereby preventing the accumulation of inorganic components in the anaerobic digestion tank even at a higher organic load than before. An object of the present invention is to provide an anaerobic treatment apparatus capable of greatly reducing the amount of organic components and recovering a large amount of methane gas even in the treatment of many organic waste liquids.

  The anaerobic treatment apparatus of the present invention (Claim 1) solid-separates an anaerobic digestion tank for anaerobic digestion treatment of organic drainage liquid and a digestion treatment liquid of the anaerobic digestion tank, and at least one of the separated liquids. The solid-liquid separation means for discharging the part out of the system, the sludge return means for returning the concentrated sludge separated by the solid-liquid separation means to the anaerobic digestion tank, and the digested sludge generated in the anaerobic digestion tank. In the anaerobic digestion apparatus comprising the sludge reforming means for quality treatment and the modified sludge return means for returning the modified sludge of the sludge reforming means to the anaerobic digester, the treatment temperature of the anaerobic digester is It is 45-60 degreeC, It has an inorganic component elution means which mixes the said digestion process liquid with dilution water and elutes an inorganic component in water, and then sends it to the said solid-liquid separation means.

  An anaerobic treatment apparatus according to claim 2 is the dilution treatment tank according to claim 1, wherein the inorganic component elution means mixes and stirs the effluent of the anaerobic digestion tank with dilution water to elute the inorganic component in water. And a diluent feeding means for feeding the effluent of the dilution processing tank to the solid-liquid separation means.

  An anaerobic treatment apparatus according to a third aspect is characterized in that in the first or second aspect, a part or all of the dilution water is the organic drainage.

  The anaerobic treatment apparatus of claim 4 is characterized in that, in claim 1, the inorganic component elution means includes the anaerobic digestion tank, and the inorganic component is eluted in the anaerobic digestion tank.

  An anaerobic treatment apparatus according to claim 5 is the anaerobic treatment apparatus according to any one of claims 1 to 4, wherein a part of the digested sludge in the anaerobic digester and / or the concentrated sludge separated by the solid-liquid separation means is used. Returning to the biological treatment system where the organic drainage is generated, the biological treatment is performed.

  An anaerobic treatment apparatus according to a sixth aspect is characterized in that, in any one of the first to fifth aspects, the sludge reforming means is an ozone treatment means.

  According to the anaerobic treatment apparatus of the present invention, treatment at a high load is possible by performing digestion treatment at 45 to 60 ° C. where a high-temperature methanogen having an optimum temperature around 55 ° C. grows, and sludge Thus, it is possible to perform a digestion process smoothly without a problem of stirring and mixing even under high sludge concentration conditions.

  That is, mesophilic methanogens having an optimum temperature around 35 ° C. have a slow growth, so it is necessary to increase the residence time (SRT) of the anaerobic digester and increase the sludge concentration. Since the growth is fast, the residence time may be short, and the sludge concentration can be lowered. Therefore, if a tank sludge density | concentration is compared on a fixed condition, it will be possible to process even higher organic load. Moreover, since the viscosity of sludge becomes low, so that temperature is high, in the high temperature digestion process by this invention, it can process without the problem of stirring mixing even in the density | concentration higher than a medium temperature digestion process.

  Moreover, according to the anaerobic treatment apparatus of the present invention, the amount of sludge withdrawn is reduced by transferring more inorganic components in the sludge accumulated in the anaerobic digestion tank to the separation liquid and discharging it to the outside of the system. In addition, the organic components in the sludge can be greatly reduced and the methane gas recovery rate can be increased.

  That is, by mixing the digestion solution with dilution water in the inorganic component elution means and eluting the inorganic component in water, the inorganic component can be transferred into the separation liquid of the solid-liquid separation means and discharged out of the system. . For this reason, it is not necessary to extract sludge to prevent the accumulation of inorganic components, and the amount of organic components in the sludge in the system can be greatly reduced by reducing the amount of sludge extraction or making it unnecessary to extract sludge. In addition, the recovery rate of methane gas can be increased.

  As the inorganic component elution means, a diluting treatment tank that mixes and stirs the effluent of the anaerobic digestion tank with the dilution water to elute the inorganic components in the water, and sends the effluent of the dilution treatment tank to the solid-liquid separation means. Preferably, the digestion treatment solution and the dilution water are sufficiently mixed and stirred for a predetermined time in such a dilution treatment tank so that the inorganic component can be eluted in water.

  In this case, by using organic drainage as dilution water, the amount of water introduced into the system as dilution water can be reduced, and the amount of heat required for heating the anaerobic digester can be reduced.

  An anaerobic digestion tank can also be used as an inorganic component elution means. In this case, anaerobic digestion can be performed by introducing diluted water into the anaerobic digestion tank or by diluting it in advance. What is necessary is just to introduce into a tank.

  In the present invention, a part of the digested sludge in the anaerobic digester and / or the concentrated sludge separated by the solid-liquid separation means is returned to the biological treatment system in which organic drainage is generated for biological treatment. Further, it is possible to further prevent the accumulation of inorganic components in the anaerobic treatment apparatus and enhance the sludge reduction effect.

  Further, as the sludge reforming means, ozone treatment means is preferable, and digested sludge generated in the anaerobic digester can be efficiently reformed by ozone treatment.

  Hereinafter, embodiments of the anaerobic treatment apparatus of the present invention will be described in detail.

  The organic drainage to be treated in the present invention is a drainage (including sludge) containing an organic substance to be treated by an anaerobic digestion treatment, and even a slurry-like solid containing a solid contains a solid. There may be no liquid. In addition, non-biodegradable organic substances, inorganic substances, cellulose, paper, cotton, wool, cloth, solid matter in human waste may be contained. Such organic effluents include sewage, sewage initial settling sludge, human waste, septic tank sludge, food factory effluent, beer waste yeast, other industrial effluents, and sludge such as excess sludge generated when these effluents are treated. Is mentioned.

  An anaerobic digestion tank is a tank in which the organic waste liquid is subjected to methane fermentation in the presence of sludge containing anaerobic microorganisms. Sludge containing anaerobic microorganisms contains acid-producing bacteria and methanogens. In the anaerobic digester, the organic components are converted to methane gas by anaerobic microorganisms by the steps of liquefaction → low molecular weight → organic acid production → methane production.

  In this invention, 45-60 degreeC which is the temperature conditions in which the high temperature methanogen which has the optimal temperature at 55 degreeC vicinity grows as conditions for methane fermentation is employ | adopted.

  As described above, mesophilic methanogens with an optimum temperature around 35 ° C are slow to grow, so it is necessary to increase the residence time of the anaerobic digester and increase the sludge concentration. Therefore, the residence time may be short and the sludge concentration can be lowered. Therefore, if a tank sludge density | concentration is compared on a fixed condition, it will be possible to process even higher organic load. Moreover, since the viscosity of sludge becomes low, so that temperature is high, in the high temperature digestion process by this invention, it can process without the problem of stirring mixing even in the density | concentration higher than a medium temperature digestion process.

The sludge residence time in the anaerobic digester is 5 days or more, preferably 15-50 days, the organic load is 0.5-3.0 kg-VSS / m ³ · day, the SS concentration in the anaerobic digester Can be anaerobically digested at 20,000 to 120,000 mg / L (2 to 12%), preferably 40,000 to 100,000 mg / L (4 to 10%).

  The dilution processing tank as an inorganic component elution means is a tank that stirs and mixes the digested sludge of an anaerobic digestion tank with dilution water to elute the inorganic component into water. As the dilution water, clean water, industrial water, biologically treated water of organic effluent can be used, but in the present invention, part or all of the organic effluent introduced into the anaerobic digester is used. May be. The residence time in the dilution treatment tank is preferably 30 minutes to 2 days. If the residence time of the dilution treatment tank is too short, the inorganic component cannot be sufficiently eluted in water. Even if the residence time is excessively long, no further elution effect of inorganic components can be obtained, which is disadvantageous in terms of tank capacity and processing efficiency.

  In this way, in the dilution treatment tank, the digested sludge is stirred and mixed with the dilution water to dilute the inorganic compounds present in the digested sludge in the form of carbonate, phosphate, hydroxide, etc. It dissolves in water according to its solubility.

  In the present invention, an anaerobic digester can be used as the inorganic component elution means. In this case, in addition to mixing the dilution water with the organic drainage in the anaerobic digester (ie, diluting the organic drainage) or introducing it separately from the organic drainage, In the anaerobic digestion treatment, the organic effluent is concentrated in advance for the purpose of extending the residence time of the anaerobic digester and reducing the amount of heat required for heating the anaerobic digester. Although introduction into the tank has been performed, it may be introduced into the anaerobic digestion tank at an SS concentration of 3,000 to 20,000 mg / L, for example, without performing such concentration, as a diluted drainage. In this method, the amount of heat required for heating the anaerobic digester increases, but the mixing and stirring time with the dilution water can be lengthened compared to the case where a dilution tank is separately provided, and the elution of inorganic components is sufficiently performed. Can proceed.

  The solid-liquid separation means solid-liquid separates the effluent from the dilution treatment tank or anaerobic digestion tank, discharges the separated liquid as treated water and discharges the separated sludge (concentrated sludge), and the anaerobic treatment tank by the sludge return means. In the anaerobic treatment apparatus of the present invention, the inorganic components dissolved in the water in the dilution treatment tank or the anaerobic digestion tank are contained in the separation liquid of the solid-liquid separation means and discharged out of the system. The As the solid-liquid separation means, a centrifugal separator (centrifugal concentrator), a flotation separator, a sedimentation tank, a membrane separator, a filtration device, or the like can be used.

  In order to prevent the accumulation of inorganic components and difficult biodegradable organic components in the anaerobic treatment tank, a part of this concentrated sludge or a part of the digested sludge in the anaerobic digestion tank is discharged as surplus sludge, dewatered, incinerated, Disposal such as landfill may be performed. Further, the separated liquid separated by the solid-liquid separation means can be discharged as sewage directly into sewage or the like, but may be discharged after aerobic biological treatment or other post-treatment.

  In addition, in the case where the organic wastewater treated in the anaerobic digestion tank is surplus sludge generated when other organic wastewater is biologically treated, a part or all of the surplus sludge discharged from the anaerobic digestion tank Can also be introduced into the biological treatment system. In this case, the surplus sludge introduction site may be a biological reaction tank such as an aeration tank, or a solid-liquid separation tank (precipitation tank) before and after that. In the biological treatment system, the inorganic components in the excess sludge are diluted and partly dissolved and contained in the biologically treated water and discharged out of the system, and some organic components are biologically treated and the remainder is anaerobic again. Since it will be introduced into the anaerobic digester of the sewage treatment device, it is possible to reduce the amount of excess sludge discharged by dehydration, incineration, landfill, etc.

  The sludge reforming means is a means for reforming the anaerobic digested sludge drawn out from the anaerobic digestion tank to be easily biodegradable by ozone treatment, heat treatment, milling, acid / alkali treatment, preferably by ozone treatment. . By reforming the digested sludge and returning it to the anaerobic digester, the reformed sludge can be further decomposed and the sludge can be highly reduced.

Ozone treatment as sludge reforming treatment is performed by bringing anaerobic digested sludge into contact with ozone. The amount of ozone organic solids anaerobic digestion sludge ozonation (VSS) _{per, 0.01~0.08g-O 3 / g-} VSS, preferably _0.02~0.05g-O 3 / g -VSS. Further, not only anaerobic digested sludge but also a part or all of organic drainage treated in an anaerobic digester may be subjected to ozone treatment. By performing such ozone treatment, the cells in the anaerobic digested sludge are killed and modified to be readily biodegradable together with other organic substances. These readily biodegradable components are digested in an anaerobic digester and more methane gas is recovered.

  The amount of the anaerobic digested sludge that is extracted from the anaerobic digestion tank and modified is maintained as an amount of organic solids (VSS) contained in the anaerobic digested sludge in order to maintain sufficient decomposition efficiency by the anaerobic microorganisms. It is preferable that the amount is 1/3 to 5 times, preferably 1/2 to 3 times the amount of the organic solid (VSS) introduced into the sex digester. The amount of the anaerobic digested sludge to be ozone-treated per day is preferably set to an amount corresponding to 1/15 to 1/100 of the total retained sludge amount in the anaerobic digester. By setting the amount of the ozone treatment sludge per day to the above amount, the amount of microorganisms necessary for the anaerobic digestion treatment can be sufficiently retained in the anaerobic digestion tank, and the treatment efficiency can be kept high.

  Next, a preferred embodiment of the anaerobic treatment apparatus of the present invention will be described in more detail with reference to the drawings.

  1 to 5 are system diagrams showing an embodiment of the anaerobic treatment apparatus of the present invention. 1 to 5, members having the same function are denoted by the same reference numerals.

  The anaerobic treatment apparatus of FIG. 1 uses part of the organic waste liquid as dilution water, and part of the organic waste liquid introduced from the pipe 11 is fed to the dilution treatment tank 2 from the pipe 12. The remainder is introduced into the anaerobic digester 1. In the anaerobic digester 1, digestion can be smoothly performed at a high load by high-temperature digestion at 45 to 60 ° C. Digested sludge from the anaerobic digestion tank 1 is introduced into the dilution treatment tank 2 through the pipe 13 and is sufficiently stirred and mixed with the organic waste liquid as dilution water. The diluted mixed liquid is supplied to the solid-liquid separation means 3 through the pipe 16. It is fed and separated into solid and liquid, and the separated liquid is discharged out of the system. In the separated liquid, the inorganic components in the digested sludge are dissolved by the dilution mixing in the dilution treatment tank 2, and the inorganic components are dissolved in the separated liquid and discharged out of the system. Accumulation of inorganic components is prevented.

  The separated sludge (concentrated sludge) of the solid-liquid separation means 3 is returned to the anaerobic digester 1 through the pipe 18. A part of the concentrated sludge is discharged out of the system as excess sludge from the pipe 19 as necessary. The sludge extraction may be performed directly from the anaerobic digester 1 through the pipe 15.

  A part of the digested sludge in the anaerobic digestion tank 1 is pulled out from the pipe 14, reformed by sludge reforming means such as the ozone reaction tank 4, and then returned to the anaerobic digester 1 through the pipes 21 and 18. . Reference numeral 5 denotes an ozone generator that feeds ozonized air or the like to the ozone reaction tank 4 through the pipe 20.

  As described above, when a part of the organic drainage is used as the dilution water, the ratio of the organic drainage supplied to the dilution tank 2 and the organic drainage directly introduced into the anaerobic digester 1 is used. There is no particular limitation, and any ratio can be adopted, but in order to efficiently dissolve the inorganic components in the digested sludge, the same amount or more with respect to the digested sludge introduced into the dilution treatment tank 2, for example, It is preferable to introduce 2 to 10 times more organic drainage into the dilution treatment tank 2.

  The anaerobic treatment apparatus of FIG. 2 uses dilution water such as clean water, industrial water, and organic wastewater biologically treated water in addition to the organic wastewater, and the total amount of the organic wastewater is the pipe 11. More introduced into the anaerobic digestion tank 1, the dilution water is introduced into the dilution treatment tank 2 through the pipe 22.

  Even in this case, in order to efficiently dissolve the inorganic components in the digested sludge, the dilution water differs depending on the type (water quality), but the same amount or more with respect to the digested sludge introduced into the dilution treatment tank 2, For example, it is preferable to introduce 2 to 10 times into the dilution treatment tank 2.

  The anaerobic treatment apparatus shown in FIG. 3 uses organic waste liquid as dilution water and introduces the entire amount thereof into the dilution treatment tank 2 through the pipe 12. In this case as well, the diluted mixed liquid containing the organic waste liquid is solid. Solid-liquid separation is performed by the liquid separation means 3 and the separated sludge is returned to the anaerobic digestion tank 1, so that the anaerobic digestion treatment of the organic effluent can be performed without hindrance together with the dissolution of the inorganic components in the digested sludge. .

  In the anaerobic treatment apparatus of FIG. 3, as in the anaerobic treatment apparatus of FIG. 1, in order to efficiently dissolve the inorganic components in the digested sludge, the digested sludge introduced into the dilution treatment tank 2 is used. It is preferable to introduce the organic waste liquid of the same amount or more, for example, 2 to 10 times, into the dilution treatment tank 2.

  The anaerobic treatment apparatus shown in FIG. 4 further introduces dilution water such as clean water, industrial water, and biological treatment water of organic drainage into the dilution treatment tank 2 through the pipe 22 in FIG. Even in this case, the total amount of the organic waste liquid and the dilution water introduced into the dilution treatment tank 2 is equal to or more than the digested sludge introduced into the dilution treatment tank 2, for example, 2 to 10 times. It is preferable to do.

  Like the anaerobic treatment apparatus of FIG. 2, FIG. 4, melt | dissolution of the inorganic component in digested sludge can be accelerated | stimulated by introduce | transducing dilution water with favorable water quality from the outside of the system. On the other hand, when organic drainage is used as dilution water, the labor and cost of introducing dilution water from the outside of the system are saved, and the fiber content in organic drainage is included in digested sludge. Thus, the effect that the sedimentation property and dewatering property of the sludge in the solid-liquid separation means 3 can be improved is preferable.

  FIG. 5 shows an embodiment in which anaerobic digestion tank 1 is used as a dilution treatment tank, and a part of surplus sludge resulting from the anaerobic digestion process is returned to the biological treatment system where organic drainage is generated. .

  In FIG. 5, raw water is introduced into a biological treatment tank (aeration tank) 6 through a pipe 31 and biologically treated, and treated water is introduced into a sedimentation tank through a pipe 32 and separated into solid and liquid. The supernatant water of the sedimentation tank is discharged out of the system as treated water from the pipe 33, a part of the separated sludge is returned to the biological treatment tank 6 from the pipe 34, and the remainder is an organic anaerobic digester tank 1 from the pipe 11 as the drainage. To be introduced. In the anaerobic digestion tank 1, the separated sludge from the sedimentation tank 7 is introduced without being concentrated, and the inorganic components are eluted together with the anaerobic digestion treatment. In addition, you may introduce | transduce dilution water into this anaerobic digester 1 separately. The treated water in the anaerobic digester 1 is fed to the solid-liquid separation means 3 through the pipe 13A and subjected to solid-liquid separation processing. A part of the excess sludge from the pipe 15 is returned to the pipe 31 from the pipe 35 and processed in the biological treatment tank 6 together with the raw water.

  The anaerobic treatment apparatus of FIGS. 1-5 is an example of embodiment of the anaerobic treatment apparatus of this invention, Comprising: This invention is not limited to what is shown in figure, unless the summary is exceeded. For example, in the anaerobic treatment apparatus of FIG. 1, dilution water may be further introduced into the dilution treatment tank 2 from outside the system. Further, the organic waste liquid or other dilution water and the digested sludge from the anaerobic digestion tank 1 may be combined in the pipe and then stirred and mixed in the dilution treatment tank 2 for a predetermined residence time. Moreover, in the apparatus of FIGS. 1-4, you may make it return a part of surplus sludge to the biological treatment tank 6 as shown in FIG. Further, excess sludge may be returned to the settling tank 7.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
Mixing anaerobic digested sludge from a sewage treatment plant with a centrifugal concentrator as seed sludge (SS concentration 98 g / L, VSS / SS ratio 0.61), mixing for 90 days using the anaerobic treatment device shown in FIG. Anaerobic digestion of raw sludge was performed.

The mixed raw sludge charged is the first settling sludge and excess sludge (SS concentration 32 g / L, VSS / SS ratio 0.80, input amount 60 L / day) in the sewage treatment plant, and the entire amount is transferred to the anaerobic digester 1. Introduced. Further, 180 L / day of sewage secondary treated water was introduced as dilution water into the dilution treatment tank (volume 150 L) 2 and mixed with digested sludge 120 L / day extracted from the anaerobic digestion tank 1. The residence time of the dilution treatment tank 2 was 2 hours. Further, sludge was extracted from the anaerobic digestion tank 1 at 40 L / day, and ozone treatment was performed by reacting with ozonized air having an ozone concentration of 140 g-O ₃ / Nm ³ in a jar-type ozone reaction tank 4 having a volume of 20 L (ozone). Reaction rate 0.035 g-O ₃ / g-TVS). This anaerobic digester (volume 1 m ³ , VSS load 1.5 kg-VSS / m ³ · day) 1 was at a temperature of 55 ° C., and the sludge was appropriately extracted out of the system so as to maintain the SS concentration of 100 g / L in the tank. . The hydraulic residence time of the anaerobic digester 1 is 17 days.

  The diluted mixed solution in the dilution treatment tank 2 is centrifugally concentrated under the condition of 2,000 G by the solid-liquid separation means (centrifugal concentrator) 3, and the separated liquid 235 to 240 L / day is discharged out of the system, and the concentrated sludge is anaerobic. By returning to the digester 1, the liquid amount of the anaerobic digester 1 was kept constant.

Comparative Example 1
Without providing a dilution tank, the digested sludge in the anaerobic digester 1 is directly concentrated by solid-liquid separation means (centrifugal concentrator) 3 and the separated liquid 55-60 L / day is discharged out of the system and the remaining concentrated The treatment was performed in the same manner except that the amount of liquid in the anaerobic digester 1 was maintained constant by returning the sludge to the anaerobic digester 1.

Comparative Example 2
In Example 1, it processed similarly except having set the temperature of the anaerobic digester 1 to 35 degreeC.

Comparative Example 3
In Example 1, the treatment was performed in the same manner except that the temperature of the anaerobic digestion tank was set to 35 ° C. and the sludge was appropriately extracted so as to maintain the SS concentration of 80 g / L in the tank.

  The integrated amount of methane gas generated during the treatment period of Example 1 and Comparative Examples 1 to 3 is shown in FIG. 6, and the integrated amount of discharged sludge is shown in FIG.

  As apparent from FIG. 6, in Example 1 and Comparative Example 1, the amount of methane gas increased 1.6 times that of Comparative Example 2 and 1.2 times that of Comparative Example 3. The average value of the methane gasification rate during the treatment period reached 95% in Example 1 and Comparative Example 1, compared to 64% and 83% in Comparative Examples 2 and 3.

  During the treatment period, lithium chloride was introduced into the anaerobic digestion tank, and the mixed state in the tank was determined using lithium as a tracer. In Example 1 and Comparative Examples 1 and 3, there was a dead space in the anaerobic digestion tank. Compared to 10% or less, it reached 65% in Comparative Example 2, and in Comparative Example 2, the sludge viscosity became too high for an anaerobic digester because of sludge concentration at 10%. It was confirmed that the mixing of the inside became insufficient and the decomposition rate of the organic component decreased.

  From FIG. 7, in Example 1, the amount of discharged sludge can be reduced to about half compared to Comparative Example 1 by dissolving the inorganic components in the input sludge in the separation liquid and discharging it out of the system. Was confirmed.

It is a systematic diagram which shows embodiment of the anaerobic processing apparatus of this invention. It is a systematic diagram which shows other embodiment of the anaerobic processing apparatus of this invention. It is a systematic diagram which shows another embodiment of the anaerobic processing apparatus of this invention. It is a systematic diagram which shows different embodiment of the anaerobic processing apparatus of this invention. It is a systematic diagram which shows different embodiment of the anaerobic processing apparatus of this invention. It is a graph which shows the integrated amount of the produced | generated methane gas in Example 1 and Comparative Examples 1-3. It is a graph which shows the integration amount of the discharge sludge in Example 1 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anaerobic digestion tank 2 Dilution processing tank 3 Solid-liquid separation means 4 Ozone reaction tank 5 Ozone generator 6 Biological treatment tank 7 Precipitation tank

Claims (6)

An anaerobic digester for anaerobic digestion of organic drainage;
Solid-liquid separation means for solid-liquid separation of the digestion treatment liquid of the anaerobic digestion tank, and discharging at least a part of the separation liquid out of the system;
Sludge return means for returning the concentrated sludge separated by the solid-liquid separation means to the anaerobic digestion tank;
Sludge reforming means for reforming digested sludge produced in the anaerobic digestion tank;
In an anaerobic digester equipped with a modified sludge return means for returning the modified sludge of the sludge reforming means to the anaerobic digester,
The treatment temperature of the anaerobic digester is 45-60 ° C,
An anaerobic treatment apparatus comprising an inorganic component elution means for mixing the digestion treatment solution with dilution water to elute an inorganic component into water and then feeding the solution to the solid-liquid separation means.   In Claim 1, the said inorganic component elution means mixes and stirs the effluent of the anaerobic digestion tank with dilution water, and elutes an inorganic component in water, The effluent of this dilution treatment tank is made into the said solid solution. An anaerobic treatment apparatus comprising a diluent feeding means for feeding to the liquid separating means.   The anaerobic treatment apparatus according to claim 1, wherein a part or all of the dilution water is the organic drainage.   2. The anaerobic treatment apparatus according to claim 1, wherein the inorganic component elution means includes the anaerobic digestion tank, and the inorganic component is eluted in the anaerobic digestion tank.   The biological treatment according to any one of claims 1 to 4, wherein the organic drainage generates a part of the digested sludge in the anaerobic digester and / or the concentrated sludge separated by the solid-liquid separation means. An anaerobic treatment apparatus characterized in that it is returned to the system for biological treatment.   6. The anaerobic treatment apparatus according to claim 1, wherein the sludge reforming means is an ozone treatment means.

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