JP2017100130A - Anaerobic digestion treatment method and anaerobic digestion treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anaerobic digestion treatment method and a device therefor easily concentrating sludge to a high concentration.SOLUTION: Provided is an anaerobic digestion treatment method comprising: a sediment separation step of separating sludge into sediment and sediment-removed sludge; a chemical mixing-condensation step of mixing a chemical to the sediment-removed sludge; a concentration separation step of subjecting the condensed sludge produced by the chemical mixing-condensation step to solid-liquid separation into concentrated sludge concentrated to 4 to 12 mass% and a separate liquid; a concentrated sludge feed step of recovering the concentrated sludge and constantly feeding the same to an anaerobic digestion step; an anaerobic digestion treatment step of subjecting the concentrated sludge to anaerobic digestion treatment; and a mixing step of mixing the whole amount or a part of the separated sediment and separate liquid and mixing the same into the anaerobic digestion sludge obtained by subjecting the concentrated sludge to anaerobic digestion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an anaerobic digestion treatment method and apparatus, and more particularly to an anaerobic digestion treatment method and apparatus using a sludge concentration method and apparatus suitable as a pretreatment for anaerobic digestion treatment.

  The anaerobic digestion treatment of sludge produces less sludge than aerobic treatment, promptly kills and stabilizes pathogenic microorganisms and parasite eggs, reduces oxygen consumption, and consumes less power. Since biogas as a component can also be obtained, this technology has been applied for a long time as an energy-saving treatment method. On the other hand, anaerobic digester equipment requires a large capacity, and is a technology with a large chemical cost burden in digested sludge treatment.

  Therefore, as the current sludge disposal methods, there are still many cases in which sludge is dehydrated and landfilled without anaerobic digestion, and dewatered and incinerated. For example, the conventional sludge anaerobic treatment includes the one shown in the block flow diagram of FIG. This flow will be described.

  The sludge 11 is sent to the storage device 12, then the sludge 11 is sent to the solid-liquid separation device 13, and is separated into solid-liquid separation into the concentrated sludge 14 and the separation liquid 15, and the concentrated sludge 14 is sent to the anaerobic digester 16. The sludge that has been sent and anaerobically digested is sent to the digested sludge aggregate preparation device 17 to separate the separation liquid 18 and the digested sludge aggregate 19 is prepared. The digested sludge aggregate 19 is sent to the dehydrator 20. Then, the separation liquid 21 is separated and a dehydrated cake 22 is prepared. The separation liquid 15, the separation liquid 18, and the separation liquid 21 are sent to the wastewater treatment facility 23 and the like. In the digested sludge aggregate preparation apparatus 17, a flocculant is often added.

  On the other hand, Patent Document 1 includes (a) a pretreatment process for solid-liquid separation of sludge mixed with human waste, and (b) an anaerobic digestion process for directly anaerobically digesting the solid matter separated in the treatment process without dehydration. And (c) an anaerobic digestion step for anaerobically digesting the plant and animal residue and the solids containing solid matter, (d) a dehydration step for dehydrating and separating the anaerobic digestion step effluent into solids and separated water, (e) Sludge from organic wastewater treatment facilities, sludge such as septic tank sludge, human waste, animals and plants by a treatment method consisting of biological treatment process that biologically oxidizes and denitrifies the separated water from the pretreatment process and the dewatering process It proposes a treatment method for human waste, waste, and sludge that treats waste containing residue in an energy-saving manner, and sanitizes compost and solid fuel into unsanitary sieve residue in human waste and septic tank sludge.

  In Patent Document 2, primary sludge generated from the first sedimentation basin and waste sludge generated from the final sedimentation basin in the wastewater treatment facility are mixed and stored, and a flocculant is added to the mixed sludge to perform primary flocculation treatment. Then, the mixed sludge that has been subjected to the primary flocculation treatment is concentrated so that the sludge concentration is 6 to 8%, and then the flocculant is added to the mixed sludge after the concentration treatment to perform the secondary flocculation treatment. In addition, the mixed sludge subjected to the secondary agglomeration treatment is subjected to a dehydration treatment method to concentrate the two types of sludge, the primary sludge generated by the wastewater treatment and the excess sludge, in one system and the subsequent dehydration. We propose a sludge treatment method and system that maximizes the total efficiency of the wastewater sludge concentration and dewatering process by concentrating and maintaining the optimum sludge concentration for the process.

  Further, Patent Document 3 proposes a slit type concentrator that increases the conveying ability of the solid-liquid separator and increases the pressing and pressing effect.

JP-A-10-216785 JP 2009-90240 A JP 2003-2111293 A

  In the conventional sludge concentration step, a residue having a particle size of 3 to 4 mm or more is separately removed before concentration in the previous stage, but the residue having a particle size smaller than that is supplied to the concentration step as it is and concentrated together with the sludge.

  Concentration methods include gravity concentration by settling sludge by gravity, belt concentration using a belt-like screen that allows moisture to pass through solids in sludge, and centrifugation using solid-liquid separation by centrifugal force. Examples include a mechanical concentration method such as a concentration method. Gravity concentration usually concentrates sludge without chemical injection. However, the concentration rate is about 2 to 3 times, and in order to increase the concentration rate, it is necessary to ensure a sufficient residence time, so an extremely large-capacity concentration tank is provided. Or it is necessary to add a chemical | medical solution, and it is not realistic as a method of obtaining high concentration sludge. In addition, the conventional mechanical concentration method requires a large amount of chemical solution in order to increase the solids recovery rate, and the belt concentration method requires a large amount of high-pressure cleaning water for cleaning the belt. Further, the centrifugal concentration method has a problem that a large amount of power is required because the container containing sludge is rotated at a high speed.

  In addition, there is a demand for an improved anaerobic digested sludge concentration technique that contributes to further shortening the HRT of the conventional anaerobic digestion treatment as described above and reducing the size of the digestion tank.

  Furthermore, in the prior art, there is a problem that the dewaterability of sludge after the anaerobic digestion treatment is deteriorated, and an effective means for coping with this problem has been desired.

  The subject of this invention is providing the method and apparatus which can concentrate a sludge easily to high concentration.

The anaerobic digestion method and apparatus of the present invention include the following sludge concentration method and apparatus.
1) Sludge is separated into residue and residue sludge, residue separation step, chemical solution mixing / aggregation step of mixing chemical solution with residue sludge, and agglomerated sludge generated in the chemical solution mixing / aggregation step into concentrated sludge and separation liquid A sludge concentration method including a concentration and separation step for solid-liquid separation.
2) Sludge is separated into residue and residue sludge, residue separation part, chemical liquid mixing / aggregation part that mixes chemicals into the residue sludge, and agglomerated sludge generated in the chemical liquid mixing / aggregation part into concentrated sludge and separation liquid A sludge concentrator including a concentration / separation unit for solid-liquid separation.

In the present invention, when separating the residue and the residue sludge in the residue separation step, it removes small impurities such as residue and hair, which are not removed in the past, and long and small fibrous impurities such as hair. This is the biggest feature. Since the sewage sludge obtained together with the residue is sufficiently removed compared to the conventional method, low-power and high-concentration concentrated sludge can be obtained without causing mechanical troubles such as entanglement of the rotating part in the concentration process. It becomes possible to improve the dewaterability by mixing the separated residue with anaerobic digested sludge at the subsequent stage.
Specific embodiments of the present invention are as follows.
[1] Sludge separation process for separating sludge into residue and residue sludge
A chemical solution mixing and agglomeration process for mixing the chemical solution with the debris sludge,
A concentration / separation step for solid-liquid separation of the agglomerated sludge produced in the chemical liquid mixing / aggregation step into a concentrated sludge concentrated to 4 to 12% by mass;
Concentrated sludge supply process that collects the concentrated sludge and supplies it quantitatively to the anaerobic digestion process,
An anaerobic digestion process for anaerobically digesting the concentrated sludge, and anaerobic digested sludge obtained by anaerobic digestion of the concentrated sludge by mixing all or part of the separated residue and separation liquid. An anaerobic digestion method including a mixing step of mixing.
[2] The anaerobic digestion treatment method according to [1], further including a dehydration step of dehydrating a mixture of the residue and separation liquid and the anaerobic digestion sludge.
[3] The anaerobic digestion method according to [1] or [2], wherein the screen residue separation step separates screen residue having a particle size of 0.5 mm or more or a particle size of 2.0 mm or more.
[4] Anaerobic digestion according to [1] to [3], wherein in the mixing / flocculation step, the amount of flocculant added is 0.2 to 1.0% with respect to the SS mass in the sewage sludge. Processing method.
[5] Sediment separation part for separating sludge into residue and residue sludge;
A chemical solution mixing / aggregation part for mixing the chemical solution with the debris sludge;
A concentration / separation unit that solid-liquid separates the agglomerated sludge produced in the chemical liquid mixing / aggregation unit into a concentrated sludge and a separated liquid;
A concentrated sludge supply unit that collects the concentrated sludge and can supply a fixed amount to the anaerobic digestion processing unit;
An anaerobic digestion treatment section for anaerobically digesting the concentrated sludge;
A mechanism for mixing the total amount or a part of the residue from the residue separation unit and the separation liquid from the concentration separation unit, and mixing the concentrated sludge with anaerobic digestion sludge obtained by anaerobic digestion;
Including anaerobic digestion treatment equipment.
[6] The anaerobic digestion apparatus according to [5], wherein the concentrated sludge supply unit includes a metering pump.
[7] The anaerobic digestion processing apparatus according to [5] or [6], wherein the concentrated sludge supply unit is provided at a position higher than the anaerobic digestion processing unit.
[8] The anaerobic digestion apparatus according to any one of [5] to [7], further including a dehydrator that dehydrates a mixture of the residue and separation liquid and the anaerobic digested sludge.
[9] The screen residue separation unit includes any one of [5] to [8], including a perforated plate having a hole diameter of 0.5 mm or more or a hole diameter of 2.0 mm or more, or a screen having a wire mesh of 60 to 100 mesh. The anaerobic digestion apparatus described.

  According to the present invention, it is possible to concentrate sludge in a space-saving, low-power apparatus, and the separated residue is used in other processes as a dehydrating aid or stored, and desired when desired. Can be used for sludge treatment.

It is explanatory drawing containing an example of the concentration apparatus for enforcing the one aspect | mode of the method of this invention. It is explanatory drawing showing the structure of the conventional processing apparatus. It is explanatory drawing which shows the embodiment which equips an anaerobic digester in the back | latter stage of a sludge separation part, mixes digested sludge with concentrated sludge, and returns it to an anaerobic digester.

  In this invention, sludge means the sludge discharged | emitted in the process of processing organic substances, such as sewage, manure, and sewage. Examples of such sludge include primary sedimentation sludge and excess sludge.

  In the present invention, the residue is separated from the sludge and contains coarse suspended solids separated by a sieve having a nominal size of 74 μm in accordance with a sewage test method, and preferably has a particle size of 0.5 mm. This means a coarse suspended substance separated by a screen having a particle size of 2.0 mm or more, a pore size of 0.5 mm or more, or a pore size of 2.0 mm or more, or a screen having a metal mesh of 60 to 100 mesh.

  Here, the particle diameter is a value classified by a sieve, and the hole diameter means the diameter of the hole.

  First, a residue separation process for separating sludge into residue and residue sludge will be described.

  In the residue separation step, a step of separating and collecting residue contained in sludge and an apparatus used in the step will be described.

  The sludge from which the residue is separated is a slurry and usually has an SS of 5 g / L (liter) or more.

  Separation of the residue can be basically performed by filtering the sludge using a sieve means having a pore size having a particle size less than the particle size to be separated according to the particle size of the residue or as desired. For example, when the ratio of primary sludge with a large amount of residue is generally high, a coarse screen is used. When the proportion of excess sludge with a small amount of residue is high, a fine screen is used. Used, but not limited to this.

  Examples of the sieving means include the perforated plate or a screen using a wire mesh.

  The form of the screen residue separating unit that separates the screen residue and the residue sludge is not particularly limited. For example, the separated screen scraping device and the vibration mechanism for preventing clogging of the sieve means Etc. are preferable.

  Next, the chemical solution mixing / aggregation step will be described.

  In the present application, the chemical solution means a drug containing at least a flocculant, and may contain other drugs other than the flocculant, such as a pH adjuster. Moreover, a chemical | medical solution is not limited to a liquid. The chemical solution can be used by using only the flocculant, using the flocculant in combination with other chemicals, or using a combination with a time difference.

  In this chemical solution mixing / flocculation step, at least a flocculant is injected and mixed into the debris sludge to prepare the sludge. The chemical liquid mixing / aggregation part for mixing the flocculant with the debris sludge is usually a flocculent mixing tank equipped with a flocculant injecting means. It may be a tube or a tubular body. Further, the chemical liquid mixing / flocculation unit may be provided with a flocculant storage tank that contains a fixed amount of the flocculant dissolved therein, and is performed by injecting the flocculant solution from the tank into the slag sludge into the flocculent mixing tank. be able to. This method is preferable because the flocculant can be efficiently injected without waste.

  In the chemical liquid mixing / flocculation step, the addition amount of the flocculant is preferably 0.2 to 1.0%, more preferably 0.3 to 0.6% with respect to the mass of SS (Suspended Solid) in the sludge.

  The flocculant is not particularly limited, and examples thereof include inorganic flocculants (for example, polyferric sulfate or PAC, sulfate bands, etc.) and organic polymer flocculants (hereinafter also referred to as polymer flocculants). These can be used alone or in combination, but preferably contain at least a polymer flocculant. Examples of the polymer flocculant include cationic, anionic, amphoteric, and the like, and examples thereof include amidine flocculants, acrylamide flocculants, and acrylic acid flocculants.

  Next, the concentration / separation process for solid-liquid separation of the coagulated sludge prepared in the chemical liquid mixing / coagulation process into the concentrated sludge and the separation liquid will be described.

  In the present invention, as described above, high-concentration concentrated sludge can be prepared by solid-liquid separation of the coagulated sludge in this concentration and separation step.

  Here, the concentration / separation part for solid-liquid separation of the aggregated sludge into the concentrated sludge and the separation liquid is not particularly limited, and a simple tank to which the gravity concentration method is applied, a centrifugal separator to which the centrifugal concentration method is applied, and levitation Examples include a separator to which a concentration method is applied, a separator using a screen, and the like. Among them, the slit-type concentrator is preferable. For example, the processed product described in Patent Document 3 is a processed product that includes a processed plate with a slit plate, and a large number of disks whose peripheral surfaces protrude on the slit plate in which a large number of slits are formed. By rotating eccentrically with the rotating shaft in the discharge direction, the processed material is sent to the discharge side on the slit plate, and in this process, the liquid component falls from the gap between the disk in the slit and is filtered, The solid component is separated and collected, and in addition to this means, a belt conveyor that rotates close to the upper surface of the slit plate in the discharge direction of the processed material and squeezes the collected material on the slit plate to remove liquid is provided in the slit. The mechanical structure provided on the board is mentioned. When the slit type concentrator is applied, high concentration can be achieved stably and reliably, for example, high concentration of 4 to 12% by mass can be achieved at an inexpensive running cost.

  The concentrated sludge separated in the concentration and separation step is supplied to a desired treatment step and can be subjected to any treatment.

  The concentrated sludge supply unit that collects the concentrated sludge and can supply the fixed amount to the processing apparatus is preferably provided with a pump in which the quantification means and the transfer means are integrated. Can be mentioned. However, by installing at least the sludge concentrating part of the sludge concentrating apparatus according to the present invention on the upper part of the anaerobic digestion tank, the concentrated sludge discharged from the concentrating part is dropped into the digestion tank directly or via a screw conveyer and charged. It is also possible. In this case, since a charging pump or the like is not necessary, the power can be reduced correspondingly.

  In addition, when the subsequent treatment process is a digestion process, as shown in FIG. 3, a digestion sludge extraction pipe is branched and a pipe that returns to the anaerobic digestion tank is provided. By mixing and charging, the concentration and viscosity of the sludge charged into the anaerobic digester can be lowered, and the pump power required for charging can be reduced.

  In addition, a part or all of the separation liquid obtained by solid-liquid separation of the coagulated sludge in this concentration / separation step can be mixed in any treatment step. In this case, the separation liquid may or may not be mixed with the residue.

  Next, an example in which the sludge concentration technique of the present invention is applied as a pretreatment for the anaerobic digestion treatment will be given below.

  In this embodiment, the residue obtained in the residue separation process is used to improve the dewaterability of sludge after the anaerobic digestion treatment. A chemical solution is added to the dewatered sludge from which the residue has been collected, mixed and prepared, and then concentrated to a high concentration (for example, 4 to 12% by mass). The separation liquid separated in the concentration process is mixed with the whole or a part of the residue separated in the previous stage with the anaerobic digested sludge after the anaerobic digestion treatment and supplied to the dehydration treatment step.

  The concentrated sludge separated in the concentration and separation step is introduced into the anaerobic digestion step. Conventionally, sludge was concentrated by gravity concentration or various mechanical concentrations, but the actual concentration of the sludge supplied to the anaerobic digestion process was about 3 to 4% and at most about 5%. In addition, since the residue in the sludge is not separated in the concentration step, it was introduced into the anaerobic digestion step together with the sludge, and most of it was decomposed by the anaerobic digestion treatment.

  As described above, sludge from which the residue has been collected (residue sludge) is subjected to the chemical liquid mixing and agglomeration process, and the amount of the residue that has been separated and recovered is anaerobic digested sludge after anaerobic digestion treatment. Mixed with. In this case, when the anaerobic digested sludge is further treated with a flocculant, the addition of the residue to the digested sludge is for separating the particle size of the residue and the agglomerated sludge produced by the flocculant. Depending on conditions such as the pore size of the means, it can be appropriately selected before and after the addition of the flocculant or simultaneously with the addition of the flocculant, and can be used in combination. When the residue is added after the addition of the flocculant, it is preferable to add the residue to the aggregated sludge at least during or before the generated aggregated sludge is treated in the dehydration step.

  The collected residue may be stored after being subjected to a drying process, if desired.

  The concentrated sludge separated in the concentration separation step is supplied to the anaerobic digestion step as described above. If the sludge concentrating section can be installed in the upper part of the anaerobic digester, the concentrated sludge discharged is directly injected into the digester by gravity. Otherwise, the concentrated sludge is collected and supplied quantitatively to the anaerobic digestion process. It is preferable to include a process for supplying concentrated sludge that can be performed, and an anaerobic digestion process for more efficient operation management can be performed.

  Examples of the concentrated sludge supply unit that collects the concentrated sludge and can quantitatively supply it to the anaerobic digestion processing unit include the above-described pump in which the quantification means and the transfer means are integrated.

  Moreover, a part or all of the separation liquid obtained by solid-liquid separation of the coagulated sludge in this concentration and separation step can be mixed with the anaerobic digestion sludge obtained in the anaerobic digestion step. In this case, the separation liquid may or may not be mixed with the residue.

  The digested sludge of the concentrated sludge treated in the anaerobic digestion step can be further treated with a coagulant as desired with a flocculant as described above, but if left as it is, the M alkalinity is high, and the treatment with the flocculant Is difficult to dilute, and it is preferable to dilute, and a separation liquid can be used for the dilution. In this case, the added residue may or may not be mixed with the separation liquid.

  Further, since the separation liquid contains phosphorus, calcium, siloxane and the like, it can be recovered by sending it to the process of recovering them.

  Next, an example of the present invention will be further described with reference to the drawings.

  FIG. 1 is a block flow diagram showing an embodiment of the present invention. The sludge concentrating device of the present invention includes at least a residue separating unit 1, a chemical solution mixing / aggregating unit including a coagulation / mixing tank 2 and a chemical solution storage tank 3, and a sludge concentrating unit 4. First, the sludge is sent to the residue separator 1 and separated into residue and waste sludge. Next, the debris sludge is sent to the agglomeration mixing tank 2 via a pipe, and the chemical solution in the chemical liquid storage tank 3 is added in the middle of the pipe or in the agglomeration mixing tank 2 to be agglomerated and prepared. The agglomerated sludge is introduced into the sludge concentration unit 4 and separated into a high concentration concentrated sludge and a separation liquid. The concentrated sludge is supplied to the pump through a feeder provided in the concentrated sludge transfer pump 5 and quantitatively transferred to the subsequent anaerobic digestion step. In addition, the separation liquid separated in the residue separation part and the sludge concentration part is mixed in the residue / separation liquid receiving tank 6 and mixed with the digested sludge after the anaerobic digestion process and supplied to the dehydration process. The

  FIG. 3 is a block flow diagram showing an embodiment in which an anaerobic digester 7 is provided after the concentration and separation unit 4. The concentrated sludge separated in the concentration separation unit 4 is anaerobically digested in the anaerobic digestion tank 7 to become anaerobic digested sludge, and is extracted through the digested sludge extraction pipe 10a. The digested sludge extraction pipe 10a is branched by a digested sludge return pipe 10b, and at least a part of the anaerobic digested sludge is returned to the anaerobic digester tank 7. The digested sludge return pipe 10 b is provided with a mixing tank 9 for mixing concentrated sludge and anaerobic digested sludge, and the mixed sludge is supplied to the anaerobic digester 7. In the illustrated embodiment, the input pump 8 for supplying concentrated sludge or a mixture of concentrated sludge and anaerobic digested sludge to the anaerobic digester 7, and for extracting the anaerobic digested sludge from the anaerobic digester 7. Although the sludge extraction pump 10 is used, if the sludge can be supplied or extracted by its own weight, the pump is unnecessary.

  Examples of the present invention will be described below. About the sewage sludge generated from A sewage treatment plant, the sludge concentration test of this invention was done according to the aspect of FIG. The sewage sludge used for the test is a gravity-concentrated sludge obtained by mixing primary sludge and surplus sludge at about 1: 1.

  In addition, this invention is not restrict | limited at all by this Example.

  Table 1 shows the specifications of the sludge concentrator used in the test. In the test, 0.5% (vs. SS ratio) of cationic polymer flocculant (average molecular weight: 3 million) was added to and mixed with the sewage sludge.

  Table 2 shows the sludge before and after the concentration treatment and the properties of the separation liquid obtained in the concentration separation step. Raw sludge is input sludge.

The analysis method was as follows.
TS (Total solids, total evaporation residue); 105 ° C. evaporation residue weight (JIS K 0102)
・ VTS (Volatile total solids, loss on ignition); 600 ° C loss on ignition (JIS K 0102)
SS (Suspended solids): Precipitation weight at 3,000 rpm for 10 minutes by centrifugation (JIS K 0102)
-VSS (Volatile suspended solids, volatile suspended particles); loss of ignition of suspended particles at 600 ° C (JIS K 0102)
・ M alkalinity; titration of supernatant with 0.1 mol / L hydrochloric acid solution to pH 4.8 with 3,000 rpm rotation speed by centrifuge (method of sewage test)
・ Coarse suspended solids; analysis of coarse suspended solids with a nominal size of 74 μm (sewage test method)

  From the above results, it is clear that sludge can be efficiently concentrated to a high concentration according to the present invention.

  Next, a dehydration test was performed on the sludge obtained by subjecting the concentrated sludge to anaerobic digestion, and changes in dewaterability due to the presence or absence of addition of residue separated by pretreatment were examined.

  The anaerobic digestion treatment conditions are as shown in Table 3. Table 4 shows the properties of the sludge before and after the anaerobic digestion treatment.

  Sludge obtained by mixing the anaerobic digested sludge in a ratio of 1: 1 with a mixture of the total amount of residue and the total amount of concentrated separated liquid separated by the pretreatment of anaerobic digestion was subjected to a dehydration test. As a comparative example, a dehydration test was also performed on sludge in which anaerobic digested sludge and concentrated separated liquid were mixed at a ratio of 1: 1. A cationic polymer flocculant (average molecular weight of 3 million) was used for sludge dewatering. Further, a belt press type dehydrator was used as the dehydrator, and the dehydration conditions were a filter cloth tension of 4.9 kN / m and a filter cloth speed of 1.0 m / min. As a result, the polymer flocculant injection rate and the moisture content of the dewatered sludge were as shown in Table 5.

  From the above results, it can be seen that according to the present invention, a dewatered sludge having a low chemical injection rate and a low water content can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Sediment separation part, 2 ... Coagulation mixing tank, 3 ... Chemical liquid storage tank, 4 ... Sludge concentration part, 5 ... Concentrated sludge transfer pump, 6 ... Sediment / separation liquid receiving tank, 7 ... Anaerobic digestion tank, 8 ... charging pump, 9 ... mixing tank, 10 ... sludge extraction pump, 10a ... digested sludge extraction piping, 10b ... digested sludge return piping, 11 ... sludge, 12 ... storage device, DESCRIPTION OF SYMBOLS 13 ... Solid-liquid separator, 14 ... Concentrated sludge, 16 ... Anaerobic digester, 17 ... Digested sludge aggregate preparation apparatus, 18 ... Separation liquid, 19 ... Digested sludge aggregate, 20 ... Dehydrator, 21 ... Separation liquid, 23 ... Wastewater treatment equipment

Claims (9)

Separation process for separating sludge into residue and residue sludge,
A chemical solution mixing and agglomeration process for mixing the chemical solution with the debris sludge,
A concentration / separation step for solid-liquid separation of the agglomerated sludge produced in the chemical liquid mixing / aggregation step into a concentrated sludge concentrated to 4 to 12% by mass;
Concentrated sludge supply process that collects the concentrated sludge and supplies it quantitatively to the anaerobic digestion process,
An anaerobic digestion process for anaerobically digesting the concentrated sludge, and anaerobic digested sludge obtained by anaerobic digestion of the concentrated sludge by mixing all or part of the separated residue and separation liquid. An anaerobic digestion method including a mixing step of mixing.   The anaerobic digestion method according to claim 1, further comprising a dehydration step of dehydrating a mixture of the residue and separation liquid and the anaerobic digested sludge.   The anaerobic digestion method according to claim 1 or 2, wherein the residue separation step separates residue having a particle size of 0.5 mm or more or a particle size of 2.0 mm or more.   4. The anaerobic digestion method according to claim 1, wherein, in the mixing and aggregating step, the addition amount of the aggregating agent is 0.2 to 1.0% with respect to the SS mass in the debris sludge. A residue separating unit for separating sludge into residue and residue sludge;
A chemical solution mixing / aggregation part for mixing the chemical solution with the debris sludge;
A concentration / separation unit that solid-liquid separates the agglomerated sludge produced in the chemical liquid mixing / aggregation unit into a concentrated sludge concentrated to 4 to 12% by mass and a separation liquid;
A concentrated sludge supply unit that collects the concentrated sludge and can supply a fixed amount to the anaerobic digestion processing unit;
An anaerobic digestion treatment section for anaerobically digesting the concentrated sludge;
A mechanism for mixing the total amount or a part of the residue from the residue separation unit and the separation liquid from the concentration separation unit, and mixing the concentrated sludge with anaerobic digestion sludge obtained by anaerobic digestion;
Including anaerobic digestion treatment equipment.   The anaerobic digestion apparatus according to claim 5, wherein the concentrated sludge supply unit includes a metering pump.   The anaerobic digestion apparatus according to claim 5 or 6, wherein the concentrated sludge supply unit is provided at a position higher than the anaerobic digestion unit.   The anaerobic digestion processing apparatus of any one of Claims 5-7 which further contains the dehydration apparatus which spin-dry | dehydrates the mixture of the said residue and separation liquid, and the said anaerobic digestion sludge.   The anaerobic digestion according to any one of claims 5 to 8, wherein the residue separating unit includes a perforated plate having a pore diameter of 0.5 mm or more or a pore diameter of 2.0 mm or more, or a screen having a wire mesh of 60 to 100 mesh. Processing equipment.