JP2007216207A - Method and apparatus for anaerobic digestion of organic waste liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anaerobic digestion apparatus of an organic waste liquid reducing an amount of organic substances without increasing a heating energy or an amount of a flocculant to be used, even under a high organic-matter loading, and increasing recovered amount of methane gas. <P>SOLUTION: Organic sludge (organic waste liquid) is introduced into a high-temperature digestion tank 1, and subjected to anaerobic digestion at 45-95°C. The digested sludge in this high-temperature digestion tank 1 is introduced into a medium-temperature digestion tank 2, and subjected to anaerobic digestion at 25-40°C. Part of the digested sludge in this medium-temperature digestion tank 2 is drawn out and concentrated in a solid-liquid separator 3. Liquid separated in the solid-liquid separator 3 is taken out of the system. Part of the concentrated sludge is returned to the medium-temperature digestion tank 2 through a return pipe 4. Part of the digested sludge sent from the medium-temperature digestion tank 2 is drawn out through a pipe 5 and modified in a modification device 6. The modified sludge is returned to the high-temperature anaerobic digestion tank 1 through a return pipe 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and apparatus for anaerobic digestion of organic waste liquid, and in particular, an anaerobic digestion treatment method and apparatus for organic waste liquid capable of increasing the digestion efficiency of organic waste liquid and increasing the amount of methane gas recovered. About.

  A method for reducing the amount of sludge-like organic sludge such as organic sludge, human waste, and food factory wastewater by digestion in the presence of anaerobic microorganisms has been practiced for a long time.

In JP-A-9-206785, an organic waste liquid is subjected to an anaerobic digestion treatment in an anaerobic digestion tank, and then the digested sludge is separated into solid and liquid, and the separated liquid is discharged as treated water to separate the separated sludge (concentrated sludge). There is described an anaerobic digestion method of organic waste liquid that is returned to the anaerobic digestion tank and modified by ozone treatment of a part of the digested sludge and returned to the anaerobic digestion tank. In this method, digested sludge is separated into solid and liquid, and the separated sludge is returned to the anaerobic digestion tank, so that the residence time of the anaerobic microorganisms is ensured, and another part of the digested sludge is treated with ozone to facilitate easy living. By returning to an anaerobic digestion tank after reforming to degradability, it can be decomposed again as a substrate for anaerobic microorganisms, increasing the digestibility (sludge reduction rate) and increasing the amount of methane gas recovered.
JP-A-9-206785

  In the apparatus of the above-mentioned JP-A-9-206785, in order to increase the recovery rate of methane gas, the reforming treatment is performed while maintaining the sludge residence time in the anaerobic digestion tank so as not to lower the efficiency of the anaerobic digestion treatment. It is necessary to increase the amount of sludge. For that purpose, a part of the digested sludge is separated into solid and liquid, and 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 keep the sludge retention amount and sludge concentration in the tank high. Therefore, it is necessary to increase the amount of sludge to be reformed as the organic load in the anaerobic digestion tank increases, and it is necessary to increase the concentration of sludge in the tank.

  However, 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 anaerobic digestion tank in the apparatus of the same publication, the medium temperature anaerobic digestion is performed by heating to 30 to 38 ° C. widely used in anaerobic digestion treatment of sewage sludge and the like. In that case, it is necessary to appropriately extract the digested sludge from the digestion tank as excess sludge so that the concentration of sludge in the tank is preferably maintained at 5 to 6% or less. For this reason, when the organic substance load of an anaerobic digester becomes high, the amount of extracted sludge increases, and restrictions are imposed on the reduction of organic components and the recovery of methane gas.

  In the apparatus of the same publication, when the inside of the anaerobic digestion tank is heated to 45 to 60 ° C. and high-temperature anaerobic digestion having a digestion rate higher than that of the intermediate-temperature digestion is performed, The sludge concentration can be lowered to cope with high organic load. However, in this case, some proteins, sugars, etc. derived from the modified sludge are not decomposed by enzymes produced by high-temperature microorganisms, so that soluble organic components that are not biodegradable in the tank have a significantly higher concentration than medium-temperature digestion. It will be released. Therefore, although the amount of solid organic components is reduced, there is a problem that the methane gas recovery rate cannot be increased. In high-temperature digestion, the solid-liquid separability of digested sludge deteriorates due to these soluble organic components, and the amount of flocculant used increases remarkably, and the load on the subsequent water treatment where the separated liquid is discharged is remarkably increased. There was a problem of increasing. In addition, high-temperature digestion also has a problem that more energy is required for heating than in medium-temperature digestion.

  The present invention solves these conventional problems, and an anaerobic treatment apparatus for organic waste liquid that can sufficiently reduce the amount of organic components and increase the amount of methane gas recovered even under a high organic load. The purpose is to provide.

  An apparatus for anaerobic digestion of organic waste liquid according to the present invention (Claim 1) includes an anaerobic digester for anaerobically digesting organic waste liquid, and a modified reformer for reforming part of digested sludge from the anaerobic digester. Quality means, modified sludge return means for returning the modified sludge from the reforming means to the anaerobic digester, solid-liquid separation means for concentrating the digested sludge from the anaerobic digester, and the solid-liquid An anaerobic digestion treatment apparatus for organic waste liquid having a concentrated sludge return means for returning the concentrated sludge from the separation means to the anaerobic digestion tank, wherein the anaerobic digestion tank is a high-temperature digestion at a treatment temperature of 45 to 95 ° C. And at least two tanks having a treatment temperature of 25 to 40 ° C. into which the effluent of the high-temperature digestion tank is introduced, and at least part of the digested sludge from the medium-temperature digestion tank is the solid-liquid It is introduced into the separating means.

  In the present invention, “sludge reforming” refers to modifying and destroying substances and sludge cells in sludge that are not easily assimilated by microorganisms to form them that are easily assimilated by microorganisms.

  An organic waste liquid anaerobic digestion treatment apparatus according to claim 2 is characterized in that, in claim 1, at least a part of the concentrated sludge from the solid-liquid separation means is returned to the intermediate temperature digestion tank.

  An apparatus for anaerobic digestion of organic waste liquid according to claim 3 is characterized in that in claim 1 or 2, digested sludge extracted from the intermediate temperature digester is introduced into the reforming means for reforming. is there.

  The anaerobic digestion treatment apparatus for organic waste liquid according to claim 4 returns the at least part of the modified sludge from the reforming means to the high-temperature digestion tank according to any one of claims 1 to 3. It is a feature.

  The anaerobic digestion treatment apparatus for organic waste liquid according to claim 5 is characterized in that in any one of claims 1 to 4, at least a part of the organic waste liquid is introduced into the intermediate-temperature digestion tank. is there.

  An apparatus for anaerobic digestion of an organic waste liquid according to claim 6 is characterized in that, in any one of claims 1 to 4, at least a part of the organic waste liquid is introduced into the solid-liquid separation means. It is.

  The organic waste liquid anaerobic digestion treatment apparatus according to claim 7 further comprises means for adding a flocculant to the digested sludge to be solid-liquid separated by the solid-liquid separation means according to any one of claims 1 to 6. It is characterized by this.

  The organic waste liquid anaerobic digestion treatment apparatus according to claim 8 is characterized in that, in any one of claims 1 to 7, the reforming treatment by the reforming means is ozone treatment.

  The method for anaerobic digestion of organic waste liquid according to the present invention (Claim 9) comprises anaerobic digestion of an organic waste liquid in an anaerobic digestion tank, and reforming digested sludge from the anaerobic digestion tank by a reforming means. The modified sludge from the reforming means is returned to the anaerobic digestion tank, and a part of the digested sludge from the anaerobic digestion tank is concentrated by the solid-liquid separation means, and the concentrated sludge from the solid-liquid separation means In the anaerobic digestion treatment method of the organic waste liquid that returns to the anaerobic digestion tank, the anaerobic digestion tank is introduced with a high temperature digestion tank having a treatment temperature of 45 to 95 ° C. and an effluent of the high temperature digestion tank. It has at least two tanks having a medium temperature digestion tank at a treatment temperature of 25 to 40 ° C., and at least a part of the digested sludge from the medium temperature digester is introduced into the solid-liquid separation means.

  In an anaerobic digester, organic waste liquid is subjected to methane fermentation in the presence of sludge containing anaerobic microorganisms. In the present invention, the anaerobic digester is composed of at least two tanks, a high-temperature digester with a treatment temperature of 45 to 95 ° C. and a medium-temperature digester with a treatment temperature of 25 to 40 ° C. into which the effluent of the high-temperature digester is introduced. ing. Organic components in the waste liquid are liquefied by high-temperature anaerobic microorganisms having an optimum temperature around 55 ° C. and medium-temperature anaerobic microorganisms having an optimum temperature around 35 ° C. It is converted to methane gas through the steps of organic acid production → methane production.

  In the high-temperature digestion tank, as described above, although the decomposition of the solid organic component proceeds more rapidly than the intermediate-temperature digestion, much remains as a colloidal soluble organic component. Since these colloidal organic components can be decomposed by mesophilic microorganisms, the remaining soluble organic components are also converted into methane gas by introducing the effluent of the high-temperature digester into the intermediate-temperature digester. Therefore, according to the present invention, the solid organic component can be decomposed at a high digestion rate in the high-temperature digester, and the conversion to methane gas can be promoted in the intermediate-temperature digester.

  Thus, according to the method and apparatus for anaerobic digestion of the organic waste liquid of the present invention, the efficiency of the anaerobic digestion is increased, and even when the organic load is higher than conventional, the heating energy and the amount of the flocculant used are reduced. Without increasing the amount, the organic components can be greatly reduced and a large amount of methane gas can be recovered.

  In the present invention, at least a part of the organic waste liquid can be introduced into either the high-temperature digestion tank, the intermediate-temperature digestion tank, or both, but is preferably introduced into the intermediate-temperature digestion tank.

  In the present invention, at least a part of the organic waste liquid may be introduced into the solid-liquid separation means. In this case, the digested sludge from the intermediate temperature digester is diluted with the organic waste liquid, so that the flocculant becomes effective. Moreover, the amount of treated sludge in the solid-liquid separation means can be reduced. The solid-liquid separation by this solid-liquid separation means is performed in order to keep the liquid level in the digestion tank constant (so as not to overflow) when introducing the organic waste liquid into the treatment system. It is necessary to discharge separation water (solid-liquid separation treated water) having the same volume as the effluent from the solid-liquid separation means. Generally, the SS concentration of organic waste liquid is lower than the SS concentration of digested sludge. Therefore, when separating the mixed liquid of organic waste liquid and digested sludge by solid-liquid separation and taking out the separated water in the same volume as the amount of organic waste liquid introduced, the separated water is separated into the organic waste liquid by solid-liquid separation of only the digested sludge. The amount of sludge to be treated by the solid-liquid separation means is smaller than in the case where the same volume as the amount introduced is taken out. This makes it possible to employ a smaller apparatus as the solid-liquid separation means. Moreover, since the amount of sludge to be processed is small, it contributes to energy saving.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1-12 is a systematic diagram showing an embodiment of an organic anaerobic digestion treatment method and apparatus of the present invention. 1-12, the same code | symbol is attached | subjected to the member which show | plays the same function.

[Anaerobic digestion treatment equipment for organic waste liquid in Fig. 1]
In FIG. 1, organic sludge (organic waste liquid) is introduced into the high-temperature digestion tank 1 and subjected to an anaerobic digestion treatment at 45 to 95 ° C. The digested sludge in the high-temperature digester 1 is introduced into the intermediate-temperature digester 2 and subjected to anaerobic digestion at 25 to 40 ° C. A part of the digested sludge in the intermediate temperature digester 2 is extracted and concentrated by the solid-liquid separator 3. The liquid component from the solid-liquid separator 3 is taken out of the system. A part of the concentrated sludge is returned to the intermediate temperature digester 2 via the return pipe 4.

  Further, a part of the digested sludge from the intermediate temperature digester 2 is pulled out by the pipe 5 and reformed by the reformer 6. The modified sludge is returned to the high temperature anaerobic digester 1 through the return pipe 7. A part of the sludge extracted from the intermediate temperature digester 2 to the pipe 5 is extracted out of the system as excess digested sludge as necessary. The excess digested sludge is preferably extracted so as to maintain the sludge (TS) concentration in the digesters 1 and 2 at 3 to 10%.

[Anaerobic digestion treatment equipment of organic waste liquid of FIGS. 2-4]
In FIG. 2, the organic waste liquid is supplied to the intermediate temperature digester 2, and only the reformed sludge from the reformer 6 is introduced into the high temperature digester 1. The other structure is the same as that of FIG. 1, and the same code | symbol has shown the same part.

  In FIG. 3, the organic waste liquid is supplied to both the high temperature digestion tank 1 and the intermediate temperature digestion tank 2, and in FIG. 4, the organic waste liquid is supplied to the solid-liquid separation device 3. The other structure is the same as that of FIG. 1, and the same code | symbol has shown the same part.

[Anaerobic digestion treatment equipment of organic waste liquid of FIGS. 5-8]
5-8, all the concentrated sludge from the solid-liquid separator 3 is returned to the high-temperature digester 1.

  FIGS. 5 to 8 correspond to FIGS. 1 to 4, respectively. In FIG. 5, the organic waste liquid is introduced into the high temperature digestion tank 1, in FIG. 6, the organic waste liquid is introduced into the intermediate temperature digestion tank 2, and in FIG. The organic waste liquid is introduced into the high-temperature digestion tank 1 and the intermediate-temperature digestion tank 2, and the organic waste liquid is introduced into the solid-liquid separator 3 in FIG.

  Other configurations are the same as those in FIGS.

[Anaerobic digestion treatment equipment of organic waste liquid of FIGS. 9-12]
9 to 12, the concentrated sludge from the solid-liquid separator 3 is returned to both the high-temperature digester 1 and the intermediate-temperature digester 2 through the pipes 4 a and 4 b branched from the pipe 4.

  9 to 12 correspond to FIGS. 1 to 4, respectively, in FIG. 9, the organic waste liquid is introduced into the high-temperature digestion tank 1, in FIG. 10, the organic waste liquid is introduced into the intermediate-temperature digestion tank 2, and in FIG. The organic waste liquid is introduced into the high temperature digestion tank 1 and the intermediate temperature digestion tank 2, and the organic waste liquid is introduced into the solid-liquid separation device 3 in FIG.

  Other configurations are the same as those in FIGS.

  The organic waste liquid to be treated in the present invention is a waste liquid containing an organic substance that is reduced by anaerobic digestion treatment, and may be a slurry containing a solid or a liquid containing no solid. . In addition, non-biodegradable organic substances, inorganic substances, cellulose, paper, cotton, wool, cloth, solid matter in human waste may be contained. Examples of such organic waste liquid include sewage, sewage initial sedimentation sludge, human waste, septic tank sludge, wastewater and residue from food factories, beer waste yeast, other industrial waste liquids, and excess sludge generated when these waste liquids are treated. Natural sludge.

  In the high-temperature digestion tank 1 and the intermediate-temperature digestion tank 2, such organic waste liquid is treated by methane fermentation in the presence of sludge containing anaerobic microorganisms. Sludge containing anaerobic microorganisms contains acid-producing bacteria and methanogens. In the anaerobic digestion process, organic substances are converted to methane gas and processed by anaerobic microorganisms through the steps of liquefaction → low molecular weight → organic acid production → methane production.

  In the high-temperature digestion tank 1, high-temperature methane-producing bacteria having an optimum temperature around 55 ° C. are mainly held, and in the intermediate-temperature digestion tank 2, medium-temperature methane-producing bacteria having an optimum temperature around 35 ° C. are mainly held. Since mesophilic methanogens grow slowly, it is necessary to lengthen the SRT, that is, to increase the size of the anaerobic digester. However, since treatment at a relatively low temperature is possible, facilities for warming and heat insulation are simplified. be able to. On the other hand, in the case of a high-temperature methanogen, heating and heat insulation facilities are required, but since the growth is fast, the SRT may be short, and the anaerobic digester can be made small.

  The high-temperature digestion tank 1 is heated so that the inside of the tank reaches the above temperature by blowing steam, introducing hot water, circulating sludge to the heat exchanger, and the like. The intermediate temperature digestion tank can maintain the temperature in the tank at the above-mentioned value by introducing the effluent of the high temperature digestion tank and the organic waste liquid, but may be heated or cooled.

  The sludge residence time (SRT) in the anaerobic digester is 5 days or more, preferably 10-30 days in the high-temperature digester 1, and is 10 days or more, preferably 15-50 days in the medium-temperature digester 2. The SS concentration in each anaerobic digester 1 and 2 is 20,000 to 120,000 mg / L (2 to 12%), preferably 40,000 to 80,000 mg / L (4 to 8%).

  Note that the longer the SRT, the higher the sludge decomposition rate, but the larger the tank capacity. As the SS concentration in the digestion tank is increased, the amount of sludge to be reformed increases even in the same residence time and the decomposition rate increases, but stirring and mixing in the tank and solid-liquid separation of sludge become difficult.

  The solid-liquid separation device 3 for concentrating the digested sludge is not particularly limited as long as it can be concentrated by solid-liquid separation of the digested sludge. A membrane separation device, a filtration device, or the like can be used.

  The daily extraction amount of the digested sludge extracted from the intermediate temperature digester 2 to the solid-liquid separator 3 is preferably about 1/30 to 1/10 of the retained sludge in the intermediate temperature digester 2.

  In the present invention, a flocculant, preferably a polymer flocculant, may be added to the digested sludge from the intermediate temperature digester 2 and then introduced into the solid-liquid separator 3. Thus, by adding the flocculant and aggregating the SS component in the digested sludge, the concentration factor in the solid-liquid separator 3 can be increased, and a clear separation liquid can be obtained. Moreover, the outflow of the solid content from the solid-liquid separator 3 can be suppressed, and the reduction of sludge organic components and the conversion to methane gas can be promoted.

  The soluble organic components remaining in the high-temperature digester increase the amount of flocculant added necessary for solid-liquid separation, but these soluble organic components are converted to methane gas and removed in the intermediate-temperature digester. Therefore, the digested sludge from the intermediate temperature digester 2 can be satisfactorily coagulated without increasing the amount of the flocculant added so much.

  In order to enhance the effect of this flocculation treatment, a mixing tank is provided in the front stage of the solid-liquid separator 3, and a flocculant is added to this mixing tank or to the digested sludge flowing into this mixing tank. Good.

  As the flocculant, either organic or inorganic, or both of them may be used. However, since the addition amount may be small and it is difficult to decompose and accumulate in the digester, organic polymer aggregation Agents, particularly cationic or amphoteric polymer flocculants are preferred.

  The degree of concentration of the digested sludge in the solid-liquid separator 3 depends on the performance of the concentrator used, but usually digested sludge having a TS (solid matter) concentration of about 3 to 6% is paste-like about 8 to 20%. It is preferable that the liquid is concentrated to a highly viscous liquid.

  The concentrated separation liquid of the solid-liquid separation device 3 can be discharged as treated water as it is to a sewer or the like, but may be discharged after aerobic biological treatment or other post-treatment.

  The concentrated sludge after the solid-liquid separation can be returned to either the high-temperature digester 1 or the intermediate-temperature digester 2 as shown in FIGS. 1 to 8 or both as shown in FIGS. 9 to 12. It is preferable to return to the intermediate temperature digester 2 as shown in FIGS. By returning to the intermediate-temperature digestion tank 2, the sludge residence time of the intermediate-temperature digestion tank 2 can be lengthened, and the intermediate-temperature anaerobic microorganisms with slow growth can be maintained in the tank.

  Concentrated sludge is mixed with the organic waste liquid, modified sludge described later, digested sludge of anaerobic digestion tank, clean water, industrial water, biological treatment water of other organic waste liquid, etc., and then returned to the anaerobic digester Also good.

  Digested sludge taken out from the intermediate-temperature digestion tank 2 is a part of the organic waste liquid supplied to this apparatus (anaerobic digestion treatment apparatus), or the organic substance supplied to this apparatus as shown in FIGS. After mixing and diluting with all of the waste liquid, solid-liquid separation may be performed, and the concentrated sludge containing the solid content in the organic waste liquid may be returned to the anaerobic digester. By diluting the digested sludge with the organic waste liquid, the flocculant becomes effective, and the amount of the treated sludge in the solid-liquid separator 3 can be reduced.

  In order to prevent the accumulation of inorganic components and hardly biodegradable organic components in the digesters 1, 2, the digested sludge of the anaerobic digester (for example, the digested sludge of the intermediate temperature digester 2, as shown) or the solid-liquid separation device 3 Part of the concentrated sludge may be discharged as surplus digested sludge and disposed of such as dewatering, incineration, and landfill. Also in this case, it is preferable to discharge the digested sludge in the intermediate temperature digester 2 as shown. Thereby, while reducing the flocculant addition rate at the time of dehydration, the water quality of the dehydrated separation liquid can be kept good.

  In the reformer 6, the anaerobic digested sludge extracted from the digester 1 or 2 is reformed by ozone treatment, heat treatment, milling, acid / alkali treatment, or the like. By performing such a modification treatment, the cells in the anaerobic digested sludge are killed and modified to be readily biodegradable together with other hardly decomposable organic components. By digesting these readily biodegradable components in the anaerobic digester, more organic components are reduced from the treatment system, and methane gas is recovered.

When an ozone treatment device is employed as the reforming device, the ozone treatment device is modified by bringing digested sludge from the intermediate temperature digestion tank 2 into contact with ozone. As a contact method with ozone in this ozone treatment apparatus, a method of introducing digested sludge into an ozone treatment tank and blowing ozone, a method by mechanical stirring, a method of using a packed bed, or the like can be employed. As ozone, in addition to ozone-containing gas such as ozonated oxygen and ozonized air, ozone-containing water can be used. The amount of ozone used is 0.01 to 0.08 g-O per VSS of digested sludge that is usually treated with ozone. ₃ / g-VSS, preferably 0.02 to 0.05 g-O ₃ / g-VSS. The pH of the ozone treatment is preferably 4-10.

In addition, although the decomposability improves as the amount of ozone used is increased, it gradually reaches a peak (not doubled when doubled), so 0.02 to 0.05 g-O ₃ / g- VSS is efficient. As the amount of sludge to be modified increases, the amount of feed that undergoes biodegradation increases. At the same time, the amount of microorganisms that degrade the feed decreases, so the sludge decomposition rate as a whole has a peak within a certain range. Further, since the ozone consumption per degraded sludge amount is smaller as the reforming treatment amount is smaller, it may be more efficient to reduce the reforming treatment amount even if the decomposition rate is somewhat lowered.

  In the present invention, the digested sludge to be modified may be extracted from either the high-temperature digestion tank, the intermediate-temperature digestion tank, or both, but it is preferable to extract from the intermediate-temperature digestion tank 2 as shown in the embodiments of each figure. In the intermediate temperature digestion tank 2, the soluble organic components remaining in the high temperature digestion tank 1 are decomposed to reduce the amount of biodegradable organic components. Can be done.

  The sludge after the modification may be returned to either the high-temperature digestion tank 1, the intermediate-temperature digestion tank 2, or both, but is preferably returned to the high-temperature digestion tank 1 as shown in the drawings. By returning to the high-temperature digestion tank 1, the reformed sludge can be quickly decomposed by high-temperature digestion with a digestion rate higher than the intermediate temperature.

  The amount of digested sludge extracted from the intermediate temperature digester 2 for reforming is the amount of organic solids (VSS) contained in the digested sludge in order to ensure a sufficient weight reduction effect by reforming. It is preferable that the amount corresponds to 1/3 to 5 times, preferably 1/2 to 2 times the amount of the organic solid matter (VSS) introduced into.

  The amount of digested sludge to be modified per day is 1/10 or less, preferably 1/100 to 1/15 of the total amount of organic solids (VSS) in the high-temperature digester 1 and the intermediate-temperature digester 2 Is preferably an amount corresponding to 1/50 to 1/30. By setting the amount of modification treatment per day to such an amount, the amount of microorganisms necessary for anaerobic digestion treatment can be maintained in the digestion tanks 1 and 2, and the efficiency of the anaerobic digestion treatment can be kept high. it can.

  In the present invention, the modification treatment is not limited to an ozone treatment apparatus, and any treatment can be used as long as it can denature and destroy sludge cells and can be modified to a form that is easily assimilated by microorganisms. In addition, various methods such as chemical treatment with strong oxidizing power such as hydrogen peroxide, chemical treatment with acid, alkali, etc., ultrasonic treatment, physical treatment such as grinding with mill, thermal treatment, etc. It can be employed alone or in combination of two or more.

  In addition to the digestion sludge extracted from the anaerobic digestion tank, the modification treatment may be performed on a part or all of the concentrated sludge obtained by concentrating the digested sludge.

  In addition, it is preferable to operate the solid-liquid separation device 3 in a state cut off from the atmosphere. For example, when the contact between the sludge and oxygen is restricted by concentrating the concentrator in a sealed state, the anaerobic bacteria are utilized. It can be returned to the anaerobic digestion tank as it is, and it becomes easy to maintain and increase the number of viable bacteria in the anaerobic digestion tank, thereby improving the digestion efficiency.

  It is also preferable to effectively use digestion gas (methane gas) generated in an anaerobic digestion tank to cover part or all of the power necessary for heating of the digestion tank, reforming means, and the like.

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

[Example 1]
As organic waste liquid, mixed raw sludge (average TVS concentration 30 g / L) collected from a sewage treatment plant was used for the devices shown in Fig. 1 (volumes of the high-temperature digester 1 and the intermediate-temperature digester 2 were 1.5 L. Solid-liquid separation. The apparatus 3 was processed under the following conditions using a centrifuge.

  High temperature digested sludge and medium temperature digested sludge collected from the anaerobic digester of the sewage treatment plant were used as seed sludge for the digesters 1 and 2, respectively.

  After operating for about 6 months, the concentration in the tank became almost constant, and the system was considered to have reached a steady state. FIG. 13 shows the balance of TVS components for the subsequent six months.

High temperature digester 1 temperature: 55 ° C
Medium temperature digester 2 temperature: 35 ° C
Sludge input amount: 100 mL / day (the entire amount is charged into the high-temperature digester 1)
Reformer 6: Ozone treatment device Ozone concentration: 150mg / NL
Ozone treatment sludge amount: 60mL / day
Ozone reaction rate: 0.03 g-O ₃ / g-TVS
Solid-liquid separation: Cationic polymer dissolved in 0.1% in sludge extracted from the intermediate temperature digester 2
So that the SS concentration of the supernatant after centrifugation is 2,000 mg / L or less
At the addition rate shown in Table 1, and centrifuged at 3,000 rpm for 10 minutes.
After that, the supernatant of about half the amount of sludge was discharged out of the system (concentration twice). remaining
(Concentrated sludge) was returned to the intermediate temperature digester 2.
Extraction of digested sludge: Intermediate temperature digester 2 so that the TVS concentration in the intermediate temperature digester 2 does not exceed 4%
Was pulled out from time to time. In accordance with this amount of withdrawal,
Adjust the discharge amount of the supernatant during solid-liquid separation so that the liquid volume is constant
did.

[Comparative Example 1]
The digesters 1 and 2 were both maintained at 35 ° C. with the apparatus of FIG. 5 (the input sludge was charged into the high temperature digester 1 and the concentrated sludge after solid-liquid separation was returned to the high temperature digester 1). Other conditions were the same as in Example 1.

[Comparative Example 2]
In Comparative Example 1, both digesters 1 and 2 were maintained at 55 ° C. Other conditions were the same as in Example 1.

  Using the digested sludge collected from the sewage treatment plant as the seed sludge for each digestion tank 1 and 2, the balance of TVS components for about 6 months after the system is expected to reach steady state after operating for about 6 months It is shown in FIG.

  The digestibility (1-drawn sludge amount / input sludge amount) × 100% is 80% in Comparative Example 1 and 92% in Comparative Example 2. In Comparative Example 2, the amount of extracted sludge decreased to 40% of Comparative Example 1, but the gasification rate considering TVS components discharged out of the system from the separated liquid was 72% in Comparative Example 1 and 74 in Comparative Example 2. % And the difference was slight. On the other hand, in Example 1, the digestibility was 92% and the gasification rate was improved to 83%. As shown in the transition of the gas generation amount in FIG. 14, in this example, the amount of digestion gas increased by about 15% compared to Comparative Examples 1 and 2.

  In addition, the average value of the flocculant addition rate during solid-liquid separation had to be increased to 2.5 g / g-TVS in Comparative Example 2 compared to 1.0 g / g-TVS in Comparative Example 1, In Example 1, it was 1.0 g / g-TVS equivalent to Comparative Example 1.

[Example 2]
The same organic waste liquid (mixed raw sludge) was treated under the same conditions as in Example 1 except that the entire amount of the organic waste liquid was supplied to the intermediate temperature digester 2 using the apparatus of FIG. The supply amount to the intermediate temperature digester 2 of the organic waste liquid is 100 mL / day which is the same as the supply amount to the high temperature digester 1 in Example 1.

[Example 3]
The apparatus of FIG. 3 was used under the same conditions as in Example 1 except that 1/2 amount of the organic waste liquid was supplied to the high-temperature digestion tank 1 and 1/2 amount was supplied to the intermediate-temperature digestion tank 2. The same organic waste liquid (mixed raw sludge) was treated. The supply amount of the organic waste liquid to the high-temperature digester 1 and the intermediate-temperature digester 2 is 50 mL / day.

[Example 4]
The same organic waste liquid (mixed raw sludge) was treated under the same conditions as in Example 1 except that the total amount of the organic waste liquid was supplied to the solid-liquid separator 3 using the apparatus shown in FIG. The supply amount of the organic waste liquid to the solid-liquid separator 3 is 100 mL / day, which is the same as the supply amount to the high-temperature digestion tank 1 in Example 1.

  FIG. 15 shows the relationship between the input sludge and the undigested sludge (withdrawal and separation liquid) in Examples 2 to 4. Table 1 shows the average values of the amount of treated sludge, the flocculant addition rate, and the amount of flocculant used during solid-liquid separation during the period.

[Discussion]
In each of Examples 2 to 4, in the same manner as in Example 1, the digestibility (1-drawn sludge amount / input sludge amount) was 90 to 93%, and the TVS component discharged out of the system from the separated liquid was taken into consideration. The gasification rate improved to 82-83%, and the amount of digestion gas increased by about 15% compared with Comparative Examples 1 and 2.

  As shown in Table 1, in Example 3, as compared with Examples 1 and 2, a clear separation liquid could be obtained with a lower coagulant addition rate, and the amount of coagulant used could be reduced by 15%.

  In Example 4, the digested sludge and the organic waste liquid (mixed raw sludge) are mixed and solid-liquid separation is performed by the solid-liquid separator 3. For this reason, the amount of sludge to be subjected to the solid-liquid separation process by the solid-liquid separation device 3 is reduced, and the effectiveness of the flocculant is improved. For this reason, even if the addition rate of the flocculant is lowered, the same flocculant effect can be obtained, and the amount of the flocculant used can be reduced by 46% compared to Examples 1 and 2.

It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a systematic diagram which shows embodiment of the anaerobic digestion processing apparatus of the organic waste liquid of this invention. It is a graph which shows the result of Example 1 and Comparative Examples 1 and 2. It is a graph which shows the time-dependent change of the amount of digestion gas of Example 1 and Comparative Examples 1 and 2. It is a graph which shows the result of Examples 2-4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High temperature digestion tank 2 Medium temperature digestion tank 3 Solid-liquid separation apparatus 6 Reformers, such as an ozone treatment apparatus

Claims (9)

An anaerobic digester for anaerobically digesting organic waste liquid;
Reforming means for reforming part of the digested sludge from the anaerobic digester;
Modified sludge return means for returning the modified sludge from the reforming means to the anaerobic digester,
Solid-liquid separation means for concentrating the digested sludge from the anaerobic digester;
Concentrated sludge return means for returning the concentrated sludge from the solid-liquid separation means to the anaerobic digestion tank;
In an anaerobic digestion treatment apparatus of organic waste liquid having
The anaerobic digester has at least two tanks, a high-temperature digester with a treatment temperature of 45 to 95 ° C and a medium-temperature digester with a treatment temperature of 25 to 40 ° C into which the effluent of the high-temperature digester is introduced.
An apparatus for anaerobic digestion of organic waste liquid, wherein at least part of the digested sludge from the intermediate temperature digester is introduced into the solid-liquid separation means.   2. The organic waste liquid anaerobic digestion apparatus according to claim 1, wherein at least part of the concentrated sludge from the solid-liquid separation means is returned to the intermediate temperature digestion tank.   The anaerobic digestion treatment apparatus for organic waste liquid according to claim 1 or 2, wherein the digested sludge extracted from the intermediate temperature digestion tank is introduced into the reforming means for reforming.   4. The organic waste liquid anaerobic digestion apparatus according to claim 1, wherein at least a part of the modified sludge from the reforming means is returned to the high-temperature digestion tank.   5. The anaerobic digestion apparatus for organic waste liquid according to claim 1, wherein at least part of the organic waste liquid is introduced into the intermediate-temperature digestion tank. 6.   5. The organic waste liquid anaerobic digestion apparatus according to claim 1, wherein at least a part of the organic waste liquid is introduced into the solid-liquid separation means.   7. The organic waste liquid anaerobic digestion apparatus according to claim 1, further comprising means for adding a flocculant to the digested sludge that is solid-liquid separated by the solid-liquid separation means.   The anaerobic digestion treatment apparatus for organic waste liquid according to any one of claims 1 to 7, wherein the reforming treatment by the reforming means is an ozone treatment. Anaerobic digestion of organic waste liquid in an anaerobic digester,
A part of the digested sludge from the anaerobic digester is reformed by reforming means,
Returning the modified sludge from the reforming means to the anaerobic digester,
Concentrate the digested sludge from the anaerobic digester with solid-liquid separation means,
In the anaerobic digestion treatment method of organic waste liquid for returning the concentrated sludge from the solid-liquid separation means to the anaerobic digestion tank,
The anaerobic digester has at least two tanks, a high-temperature digester with a treatment temperature of 45 to 95 ° C and a medium-temperature digester with a treatment temperature of 25 to 40 ° C into which the effluent of the high-temperature digester is introduced.
An organic anaerobic digestion method, wherein at least a part of digested sludge from the intermediate temperature digester is introduced into the solid-liquid separation means.

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