JP2005313120A - Anaerobic treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an amount of removed sludge, substantially decrease an organic component in the sludge and also increase a recovery rate of a methane gas by causing a larger amount of inorganic components in the sludge accumulated in an anaerobic digestion tank to migrate to a separated liquid and discharging outside the system. <P>SOLUTION: The anaerobic treatment apparatus has the anaerobic digestion tank 1 for carrying out anaerobic digestion treatment of a liquid to be treated containing an organic waste liquid, a dilution treatment tank 2 for mixing an outflow liquid from the anaerobic digestion tank 1 with diluting water and agitating to elute the inorganic component in water, diluting liquid feeding means for feeding an outflow liquid from the dilution treatment tank 2 to solid-liquid separation means 3, the solid-liquid separation means 3 for carrying out solid-liquid separation of a mixed liquid of the outflow liquid from the anaerobic digestion tank 1 and the diluting liquid to discharge at least a part of the separated liquid outside the system, and sludge recirculation means for recirculating the sludge separated by the solid-liquid separation means 3 to the anaerobic digestion tank 1. A part of the organic waste liquid is fed to the dilution treatment tank 2 as the diluting water and the remnant of the organic waste liquid is fed to the anaerobic digestion tank 1. <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. 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, in this way, in the device that returns the solid-liquid separated concentrated sludge to the anaerobic digester, the organic components in the sludge are significantly reduced and recovered as methane gas, whereas the inorganic components are not reduced. Although only a small part of the inorganic component dissolved in the liquid is contained in the separation liquid and discharged out of the system, most of the inorganic component accumulates in the anaerobic digester. Moreover, the inorganic component in sludge transfers to liquid by digestion, and it precipitates again. Therefore, as the digestion of the organic matter in the organic drainage proceeds, the inorganic matter becomes easier to reprecipitate. When the sludge concentration in the anaerobic digestion tank increases due to the accumulation of inorganic components, the viscosity of the liquid in the tank increases rapidly, so the inside of the anaerobic digestion tank is not sufficiently stirred and mixed, and the efficiency of the anaerobic digestion decreases. End up. 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. There was a problem that the effect was limited.

Japanese Patent Application Laid-Open No. 2002-361291 describes a processing method in which a part of digested sludge and organic drainage are mixed and solid-liquid separated. Although this method is an effective method for improving the solid-liquid separation property of digested sludge, it does not take enough reaction time to dissolve the inorganic components, thus preventing the accumulation of inorganic components in the anaerobic digester. I couldn't.
JP-A-9-206785 JP 2002-361291 A

  The object of the present invention is to solve the above-mentioned conventional problems, and transfer more inorganic components in the sludge accumulated in the anaerobic digestion tank to the separation liquid and discharge it outside the system, thereby eliminating the need for sludge extraction. Or providing an anaerobic treatment apparatus capable of reducing the amount of sludge withdrawn.

  The anaerobic treatment apparatus of the present invention (Claim 1) performs solid-liquid separation on an anaerobic digestion tank for anaerobic digestion treatment of a liquid to be treated containing organic drainage liquid, and an effluent from the anaerobic digestion tank. An anaerobic digester comprising: solid-liquid separation means for discharging at least part of the liquid out of the system; and sludge return means for returning sludge separated by the solid-liquid separation means to the anaerobic digestion tank. A dilution treatment tank for mixing and stirring the effluent of the digestive digestion tank with dilution water to elute inorganic components in the water, and a dilution liquid feeding means for feeding the effluent of the dilution treatment tank to the solid-liquid separation means It is characterized by comprising.

  By simply joining the effluent of the anaerobic digestion tank with the dilution water and solid-liquid separation, the inorganic component in the sewage sludge of the anaerobic digestion tank can hardly be transferred to the liquid side. It is contained in the separated sludge (concentrated sludge) returned to the anaerobic digester from the separation means and accumulates in the anaerobic digester, but the effluent of the anaerobic digester is mixed with the diluted water for a predetermined time. By stirring, the inorganic component can be eluted in water, and thereby 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.

  An anaerobic treatment apparatus according to a second aspect is the method according to the first aspect, wherein a part of the organic drainage is supplied to the anaerobic digestion tank and at least a part of the remaining part is supplied as dilution water to the dilution treatment tank. And a means for supplying. Thus, by using a part of the organic drainage as the dilution water, it is possible to increase the processing efficiency of the organic drainage and increase the solid-liquid separation efficiency in the solid-liquid separation means.

  The anaerobic treatment apparatus according to claim 3 is characterized in that, in claim 1, the whole amount of the organic drainage is fed to the dilution treatment tank. Can be reduced, and methane gas recovery efficiency can be improved.

  An anaerobic treatment apparatus according to claim 4 is the anaerobic treatment apparatus according to any one of claims 1 to 3, wherein a reforming means for reforming a part of the effluent of the anaerobic digester, and reforming of the reforming means And a reforming liquid returning means for returning the liquid to the anaerobic digestion tank, and a part of the effluent of the anaerobic digestion tank is modified and returned to the anaerobic digestion tank. As a result, it is possible to further reduce the amount of organic components and increase the amount of methane gas recovered.

  An anaerobic treatment apparatus according to claim 5 is characterized in that, in claim 4, the reforming means is an ozone treatment means, and the effluent of the anaerobic digester is efficiently reformed by ozone treatment. can do.

  According to the anaerobic treatment apparatus of the present invention, more inorganic components in the sludge accumulated in the anaerobic digester are transferred to the separation liquid and discharged out of the system, thereby reducing the amount of sludge withdrawn and sludge It is possible to greatly reduce the amount of organic components contained therein and increase the recovery rate of methane gas.

  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.

  As conditions for methane fermentation, any temperature condition in which a medium temperature methanogen having an optimum temperature around 35 ° C. and a high temperature methanogen having an optimum temperature around 55 ° C. are allowed to grow. Since mesophilic methanogens grow slowly, the residence time (SRT) needs to be increased, that is, an anaerobic digester must be enlarged, but because it can be processed at a relatively low temperature, facilities for warming and keeping warm Becomes easier. On the other hand, in the case of a high-temperature methanogen, warming and heat retention facilities are required, but since the growth is fast, the residence time may be short, and the anaerobic digester can be made small.

In the case of mainly mesophilic methanogens, the sludge residence time in the anaerobic digester is 10 days or longer, preferably about 15 to 30 days. On the other hand, when a high-temperature methanogen is mainly used, a residence time (2 days or more) shorter than the above range can be used. The treatment in the anaerobic digester is usually carried with an organic load of 0.5 to 2.0 kg-VSS / m ³ · day, and the SS concentration in the anaerobic digester is 5,000 to 100,000 mg / L, preferably 30,000. It is carried out under conditions of ˜80,000 mg / L, temperature 30 to 38 ° C. or 45 to 60 ° C.

  A dilution processing tank is a tank which stirs and mixes the digested sludge of an anaerobic digestion tank with dilution water, and elutes an inorganic component in 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.

  The solid-liquid separation means is an apparatus that separates the effluent from the dilution treatment tank into solid, discharges the separated liquid as treated water, discharges the separated sludge (concentrated sludge), and returns it to the anaerobic treatment tank by the sludge return means. In the anaerobic treatment apparatus of the present invention, the inorganic component dissolved in water in the dilution treatment tank is contained in the separation liquid of the solid-liquid separation means and discharged out of the system. 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 non-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 excess sludge for dehydration, incineration, 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.

  The reforming means is means for reforming the anaerobic digested sludge extracted from the anaerobic digestion tank to be readily biodegradable, preferably by ozone treatment, such as ozone treatment, heat treatment, milling, acid / alkali treatment, and the like. 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.

The ozone treatment as the 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. By performing the ozone treatment as described above, the microbial cells in the anaerobic digested sludge are killed and are easily 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 anaerobic digested sludge that is extracted from the anaerobic digestion tank and treated with ozone is sufficient to maintain sufficient decomposition efficiency by anaerobic microorganisms. Therefore, the amount of organic solids (VSS) contained in the anaerobic digested sludge is anaerobic. A range corresponding to 1/3 to 5 times, preferably 1/2 to 3 times the amount of organic solids (VSS) introduced into the digester is preferable. 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.

  1-4 is a systematic diagram showing an embodiment of an anaerobic treatment apparatus of the present invention. 1-4, the same code | symbol is attached | subjected to the member which show | plays the same function.

  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. 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 mixture is sent to the solid-liquid separation 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 treatment tank 2 and the organic drainage introduced directly into the anaerobic digestion tank 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.

  The anaerobic processing apparatus of FIGS. 1-4 is an example of embodiment of the anaerobic processing 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.

  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 (TS concentration 78 g / L, TVS / TS 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 input is surplus sludge from the sewage treatment plant (TS concentration 9.8 g / L, TVS / TS ratio 0.80, 120 L / day), and a part of 30 L / day to the anaerobic digester 1 The remaining 90 L / day was fed to a dilution treatment tank 2 having a volume of 100 L, and mixed in the dilution treatment tank 2 with digested sludge extracted from the anaerobic digestion tank 1 at a flow rate of 60 L / day. The residence time of the dilution treatment tank 2 was 16 hours. Also, sludge was extracted from the anaerobic digestion tank 1 at 40 L / day, and ozone treatment was performed by reacting with ozone-containing 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). The anaerobic digestion tank (volume 2 m ³ ) 1 was at a temperature of 35 ° C., and the sludge was appropriately drawn out of the system so as to maintain the TS concentration in the tank of 80 g / L.

  The diluted mixed solution in the dilution processing tank 2 is centrifugally concentrated under the condition of 2,000 G in the solid-liquid separation means (centrifugal concentrator) 3, and the separated liquid 110 to 120 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.

Example 2
In Example 1, the treatment was performed in the same manner except that all of the mixed raw sludge 120L / day was introduced into the dilution treatment tank 2 by the anaerobic treatment apparatus of FIG.

Comparative Example 1
In Example 1, the diluting tank 2 is omitted, and all of the mixed raw sludge 120L / day is introduced into the anaerobic digester 1, and the digested sludge is extracted from the anaerobic digester at a flow rate of 240 L / day and centrifuged with a centrifugal concentrator. The treatment was performed in the same manner except that it was concentrated.

  In the above-described Examples 1 and 2 and Comparative Example 1, the relationship between the integrated amount of the inorganic substance in the input sludge and the integrated amount of the inorganic substance discharged out of the system from the separation liquid is shown in FIG. The relationship with the accumulated amount of methane gas is shown in FIG.

  As is apparent from FIGS. 5 and 6, in Examples 1 and 2, the inorganic content contained in the separation liquid and discharged out of the system is about 1.8 times and about 1.9 times that of Comparative Example 1, respectively. It was. The sludge concentration in the anaerobic digestion tank is 35 to 37 g / L in each of Examples 1 and 2 and Comparative Example 1. In Comparative Example 1, the inorganic substances accumulated in the tank and discharged as excess sludge were implemented. In Examples 1 and 2, it can be seen that they are contained in the separation liquid and discharged out of the system.

  As a result, in Examples 1 and 2, the amount of methane gas was increased 1.18 times and 1.25 times that of Comparative Example 1, respectively, and the methane gas recovery rate was increased from 65% to 76% and 81%, respectively.

Example 3
Mixing anaerobic digested sludge from a sewage treatment plant with a centrifugal concentrator as seed sludge (TS concentration 78 g / L, TVS / TS 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 that was input was excess sludge (TS concentration 34 g / L, TVS / TS ratio 0.80, 45 L / day) of the sewage treatment plant, and the entire amount was introduced into the anaerobic digester 1. Further, 400 L / day of sewage secondary treated water was introduced as dilution water into the dilution treatment tank (volume 100 L) 2 and mixed with digested sludge extracted from the anaerobic digestion tank 1 at a flow rate of 90 L / day. The residence time of the dilution treatment tank 2 was 2.5 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). The anaerobic digestion tank (volume 2 m ³ ) 1 was at a temperature of 35 ° C., and the sludge was appropriately drawn out of the system so as to maintain the TS concentration in the tank of 80 g / L.

  The diluted mixed solution in the dilution processing tank 2 is centrifugally concentrated under the condition of 2,000 G by the solid-liquid separation means (centrifugal concentrator) 3, the separated liquid 435 to 445 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 2
In Example 3, the dilution treatment tank 2 is omitted, the dilution water is not used, the digested sludge is extracted from the anaerobic digestion tank 1 at a flow rate of 90 L / day, and is concentrated by centrifugation with a centrifugal concentrator, and the separation liquid is 35 to 45 L / day. The same treatment was performed except that was discharged out of the system.

Comparative Example 3
In Example 3, the diluting tank 2 is omitted, and the diluting water is directly introduced into the sludge transfer pipe from the anaerobic digester 1 to the centrifugal concentrator, and the treatment is performed in the same manner except that the diluting and mixing is performed in the pipe. went.

  In the above Example 3 and Comparative Examples 2 and 3, the relationship between the integrated amount of the inorganic substance in the input sludge and the integrated amount of the inorganic substance discharged out of the system from the separation liquid is shown in FIG. The relationship with the accumulated amount of methane gas is shown in FIG.

  As is apparent from FIGS. 7 and 8, in Example 3, the inorganic content contained in the separation liquid and discharged out of the system was about five times that of Comparative Examples 2 and 3. The sludge concentration in the anaerobic digestion tank is 30 to 32 g / L in both Example 3 and Comparative Examples 2 and 3. In Comparative Examples 2 and 3, the inorganic substances accumulated in the tank and discharged as excess sludge In Example 3, it can be seen that it was contained in the separation liquid and discharged out of the system.

  As a result, in Example 3, the amount of methane gas was increased to 1.2 times that of Comparative Examples 2 and 3, and the methane gas recovery rate was increased from 71% to 85%.

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 graph which shows the relationship between the integrated amount of the inorganic substance in input sludge and the integrated amount of the inorganic substance contained in the separation liquid and discharged | emitted out of the system in Examples 1, 2 and Comparative Example 1. It is a graph which shows the relationship between input sludge integration amount and the integration amount of produced | generated methane gas in Examples 1, 2 and Comparative Example 1. FIG. It is a graph which shows the relationship between the integrated amount of the inorganic substance in input sludge in Example 3 and Comparative Examples 2 and 3 and the integrated amount of the inorganic substance contained in the separation liquid and discharged | emitted out of the system. It is a graph which shows the relationship between the amount of input sludge integration in Example 3 and Comparative Examples 2 and 3 and the integration amount of produced | generated methane gas.

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

Claims (5)

An anaerobic digester that anaerobically digests the liquid to be treated, including organic drainage;
Solid-liquid separation means for solid-liquid separation of the effluent of the anaerobic digestion tank, and discharging at least a part of the separation liquid out of the system;
In an anaerobic digester comprising a sludge return means for returning the sludge separated by the solid-liquid separation means to the anaerobic digester,
A dilution treatment tank for mixing and stirring the effluent of the anaerobic digestion tank with dilution water to elute inorganic components in the water;
An anaerobic treatment apparatus comprising: a diluting liquid feeding means for feeding the effluent of the diluting treatment tank to the solid-liquid separation means.   2. A means for supplying a part of the organic drainage liquid to the anaerobic digestion tank and a means for supplying at least a part of the remaining part as dilution water to the dilution treatment tank. The anaerobic processing apparatus described in 1.   The anaerobic treatment apparatus according to claim 1, wherein the whole amount of organic drainage is fed to the dilution treatment tank.   A reforming means for reforming a part of the effluent of the anaerobic digestion tank, and a reforming liquid returning means for returning the reformed liquid of the reforming means to the anaerobic digestion tank. The anaerobic processing apparatus according to any one of claims 1 to 3.   The anaerobic treatment apparatus according to claim 4, wherein the reforming means is ozone treatment means.

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