JP2003071411A - Method for treating organic wastes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating organic wastes by which excess sludge generation amount can be eliminated or at least decreased in biological wastewater treatment, facilities can be miniaturized, the operation cost and installation cost can be lowered and simultaneously methane gas is produced from the excess sludge and/or organic solid waste to recycle resources as fuel, etc. SOLUTION: The organic waste treatment method involves an aerobic biological treatment step of organic wastewater, a solid-liquid separation step for biologically treated wastewater, a sludge return step of returning at least some portion of the separated sludge to the aerobic biological treatment step, and a solubilization step of solubilizing at least some of the remaining excess sludge and also an anaerobic digestion step for organic solid wastes, a digestion sludge supply step of supplying the digestion sludge subjected to the anaerobic digestion treatment to the aerobic biological treatment step and/or the solubilization step and a solubilized sludge return step of returning the solubilized sludge to the aerobic biological treatment step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for biologically treating organic waste such as organic wastewater and organic solid waste, and more specifically, excess sludge generated in the process of treating organic wastewater. And a method for treating organic waste, which reduces the volume of organic solid waste and recovers methane gas.

[0002]

2. Description of the Related Art Conventionally, as a device for treating organic wastewater such as sewage, food wastewater or kitchen wastewater, there are many biological treatment devices such as an activated sludge treatment device, a fixed bed type biological treatment device or a fluidized bed type treatment device. It is used. Further, as an apparatus for treating organic solid waste such as food waste, livestock excrement or septic tank sludge, a treatment apparatus such as an anaerobic digestion treatment apparatus or a composting apparatus is often used.

In the above activated sludge treatment device, waste water is supplied into a treatment tank in which sludge, which is an aerobic microorganism, floats.
It is a device that biologically oxidizes and decomposes organic matter in raw water by biological action of sludge by aeration with air.In addition, in fixed bed type biological treatment devices, synthetic resin is used in the treatment tank. It is a device that establishes a fixed bed of biological support carrier such as etc., causes microorganisms to adhere and grow on the surface of the carrier by aerating with air, and biologically oxidizes and decomposes organic matter in raw water by the biological action of the attached microorganisms. In addition, the fluidized bed type treatment equipment is fluidized by filling the liquid in the aerobic biological treatment tank with a biological support carrier such as synthetic resin particles so that it can flow, and supplying raw water and aerating with air. It is a device for biologically oxidatively decomposing organic matter in raw water by the biological action of microorganisms attached and propagated on the surface of the biological support carrier.

In each of the above-mentioned biological treatment devices, a large amount of grown microorganisms are generated as sludge as the organic matter is biologically decomposed. The generated sludge is separated and concentrated in a settling tank, etc., and part of it is recycled to the biological treatment process, but the rest is discharged outside the system as excess sludge, and the excess sludge is concentrated, dehydrated, and then incinerated or landfilled. It is being disposed. The excess sludge amount is said to be 20 to 50% of the organic matter amount (BOD) in the raw water introduced into the biological treatment process.

Further, as a method for reducing the volume of generated sludge as much as possible, Japanese Patent Publication No. 6-509986 discloses a combination of a mesophilic biological treatment tank and a thermophilic biological treatment tank in which sludge generated from the mesophilic biological treatment tank is combined. After solubilizing in a thermophilic biological treatment tank, it is returned to the mesophilic biological treatment tank to treat the solubilized sludge with raw water, a sludge volume reduction method is disclosed, and an apparatus provided with an anaerobic treatment step is disclosed. Japanese Patent Laid-Open No. 2000-2024
No. 90, JP 2000-246280 A, JP 2001-157900 A, and the like. In addition, solubilization of sludge means that microorganisms that compose sludge are decomposed into low-molecular organic matter, and volume reduction of sludge reduces the volume of sludge discharged as excess sludge. Means that.

The method disclosed in Japanese Patent Laid-Open No. 2000-202490 is to anaerobically digest organic wastewater,
A method of solubilizing the anaerobic digested sludge after treatment in a solubilization treatment step with ozone, supplying the solubilized sludge and treated water after anaerobic digestion to an aerobic treatment step, and treating the anaerobic digestion sludge. The method disclosed in Japanese Patent Publication No. 246280 discloses that organic sludge is anaerobically digested, the treated anaerobic digestion liquid is subjected to aerobic digestion treatment, and further, the aerobic digestion liquid is subjected to solid-liquid separation to concentrate the sludge. Then, the concentrated sludge is solubilized by solubilization treatment with ozone and returned to the anaerobic treatment step, and the method disclosed in JP 2001-157900 A is anaerobic digestion of organic sludge. After the treatment, the treated anaerobic digested sludge is subjected to solid-liquid separation to concentrate the sludge, and the concentrated sludge is solubilized by an appropriate reforming process (solubilization process) and returned to the anaerobic treatment process. is there.

[0007]

In the conventional sludge disposal method, in which sludge is concentrated and dehydrated and then incinerated or landfilled, the water content is 70 to 80 wt even after sludge is concentrated and dehydrated. Since it is as high as 10%, it is bulky, and when requesting a waste disposal company to dispose of it, the collection cost becomes high, and it currently accounts for most of the cost of wastewater treatment. Furthermore, in landfill disposal,
The remaining years of the industrial waste landfill are decreasing,
The pick-up cost is also rising year by year. In addition, in the case of incineration, the fuel content is high due to the high water content, the fuel cost is high, and it is necessary to treat exhaust gas and incineration ash.In recent years, the incineration process itself has become difficult due to the dioxin problem. It is a situation that is getting worse.

Further, in the sludge volume reduction method disclosed in Japanese Patent Publication No. 6-509986, since the treatment is carried out in a plurality of cycle operations, there are problems that the treatment process is complicated and the treatment time is long. Furthermore, in the solubilization treatment in the thermophilic biological treatment tank, since aeration with a large amount of air,
An extremely large amount of heat is lost due to the discharge of air, and since the sludge itself has a strong odor, an extremely strong odor is released by aeration.

Further, in the method of reducing the volume of sludge by the anaerobic digestion method, the sludge is supplied into a treatment tank in which anaerobic microorganisms such as methane bacteria are suspended and aerated with anaerobic gas. Is a method of decomposing organic matter in sludge into methane gas, carbon dioxide gas and the like by the biological action of anaerobic microorganisms, which is a preferable method because it has an advantage that methane gas can be effectively used as fuel and the like. -2024
In the method disclosed in Japanese Patent Publication No. 90, since there is a solubilization treatment step as a pretreatment for the organic effluent as an anaerobic treatment step, the load in the solubilization step cannot be reduced and the sludge is solubilized. There is a problem that methane is not efficiently recovered in the subsequent anaerobic digestion process.

Further, according to the method disclosed in Japanese Patent Laid-Open No. 2000-246280, since the sludge is circulated between the anaerobic treatment step and the ozone solubilization treatment step, the anaerobic digestion sludge before the ozone solubilization treatment step. There is a problem that the reducing substance must be oxidized again by aerobic treatment.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. 2001-157900, since there is no aerobic treatment step after the anaerobic treatment step, the anaerobic digested sludge is discharged as excess sludge, and it is necessary to dispose of it. There is a problem such as becoming.

[0012] Further, although the above-mentioned respective publications describe the volume reduction of sludge, there is no description about the treatment of organic solid waste. Therefore, organic solid waste will be treated by a separate device as a conventional method of treating by anaerobic digestion treatment or composting treatment, but in the case of anaerobic digestion treatment of organic solid waste, it is extremely treated. There is a problem that it takes a long time and a large amount of digested sludge is generated after the treatment. In the composting process, depending on the type of solid waste, there are some that are not used for composting, and at present,
There is also a problem that the manufactured compost has to be collected in a few places and must be disposed of in landfills.

The present invention has been made in view of the problems in the above-mentioned conventional sludge disposal and volume reduction treatments, and aims at reducing the amount of excess sludge generated in biological wastewater treatment to at least zero or reducing the volume. In addition, the equipment can be downsized, and operating costs and equipment costs can be reduced. At the same time, it was made for the purpose of providing a method for treating organic waste, which is capable of producing methane gas from excess sludge and / or organic solid waste and recycling the produced methane gas as fuel or the like.

[0014]

Means for Solving the Problems The gist of the present invention for achieving the above-mentioned object is, in the invention described in claim 1, an aerobic biological treatment step for biologically treating organic wastewater aerobically, and an organism. A solid-liquid separation step of solid-liquid separating sludge in the treated mixed liquid, a sludge returning step of returning at least a part of the separated sludge to the aerobic biological treatment step as return sludge, and a residual sludge surplus The sludge is provided with a solubilization treatment step of solubilizing at least a part of the sludge, and an anaerobic digestion treatment step of biologically treating the organic solid waste with anaerobic digestion and digested sludge subjected to the anaerobic digestion treatment as described above. It is characterized by providing a digestive sludge supplying step for supplying to the aerobic biological treatment step and / or the solubilizing treatment step and a solubilized sludge returning step for returning the solubilized solubilized sludge to the aerobic biological treatment step. A treatment method of organic waste.

When the volume of the excess sludge is reduced only by the anaerobic digestion treatment, the polypeptides and polysaccharides constituting the cells of the activated sludge microorganisms are difficult to decompose and easily remain, but the constitution of the above-mentioned claim 1. By doing so, since polypeptides and polysaccharides that do not decompose can be reduced to low molecular weight in the solubilization treatment tank, the volume of sludge can be efficiently reduced and the amount of excess sludge generated can be reduced to zero. Alternatively, at least the volume can be reduced. Furthermore, by using methane gas generated from organic solid waste for heating sludge, it is possible to suppress the running cost of volume reduction treatment, and to reduce operating costs and equipment costs.

When an anaerobic digestion tank is used in the anaerobic digestion process, the temperature is 25 to 75 ° C., preferably 45.
It is processed at -60 ° C and a residence time of 24 hours to 2 weeks. When the temperature is lower than 25 ° C, there is a problem that biological anaerobic digestion treatment is difficult to proceed, and when the temperature is higher than 75 ° C, there is a problem that anaerobic microorganisms are hard to survive. Further, when a thermophilic microorganism solubilization tank using high temperature aerobic microorganisms is used in the solubilization treatment step, the treatment is carried out at a temperature of 45 to 75 ° C, preferably 55 to 70 ° C, and a residence time of 10 to 100 hours. If the temperature is lower than 45 ° C, there is a problem that the activity of thermophilic microorganisms is almost lost.
If it is higher than ℃, there is a problem that the thermophilic microorganisms are hard to survive.

Further, in the invention described in claim 2, in the method for treating organic waste according to claim 1, a concentration step for concentrating excess sludge and / or organic solid matter is provided to provide concentrated solid matter. Is a method for treating organic waste, in which at least a part of the above is supplied to the anaerobic digestion treatment step and biologically treated anaerobically.

In the constitution provided with the sludge concentrating step of claim 2, it is more preferable in biological treatment by supplying the concentrated sludge and / or organic solid matter to the solubilization treatment step and the anaerobic digestion treatment step. Since the water content and the organic matter concentration are high and the treatment capacity can be reduced, methane gas can be efficiently obtained and at the same time, sludge can be efficiently solubilized.

The sludge concentration concentrated in the sludge concentration step is preferably 2 to 10 wt%, and if the sludge concentration is lower than 2 wt%, there are problems such as a decrease in treatment speed and a large amount of heating energy. On the other hand, if it is higher than 10% by weight, the fluidity is lowered and thus the mixing becomes difficult and the treatment efficiency is lowered.

In each of the above claims, in the solubilization treatment step, a thermophilic microbial solubilization method using a high-temperature aerobic microorganism, an alkali solubilization method that decomposes with an alkali, an ultrasonic solubilization method that solubilizes with ultrasonic waves, and various other methods. A known solubilization method can be appropriately used. Further, in the solid-liquid separation step, a sedimentation tank or a filtration membrane separation device is used, and in the sludge concentration step,
A centrifugal separator, a filter membrane separator, a filter, or the like is used. Furthermore, when the thermophilic microbial solubilization method is used as the solubilization treatment step, heat exchange for heat exchange between the concentrated sludge solid-liquid separated in the settling tank and the solubilized sludge in the solubilization treatment tank. May be provided.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a system diagram of an organic waste treatment apparatus according to one embodiment of the present invention, FIG. 2 is a system diagram of an organic waste treatment apparatus according to another embodiment of the present invention, and FIG. It is a systematic diagram of the organic waste treatment apparatus of the embodiment. In all the drawings, the same reference numerals are given to members having corresponding functions.

In all of the drawings, 1 is a flow rate adjusting tank for adjusting the amount of supplied wastewater such as sewage, food wastewater, kitchen wastewater, or human waste water and the pH value, and 2 is an aeration means 7 provided at the bottom. , An activated sludge treatment tank 3, which is an aerobic biological treatment process that decomposes the organic matter in the raw water by a biological action of aerobic microorganisms by aerating the supplied raw water with an oxygen-containing gas such as air. A sludge separation tank, which is a solid-liquid separation process for settling and separating sludge in the treated mixed liquid, is a crushing machine for fragmenting relatively large solid matter in organic solid waste such as food waste and septic tank sludge. Machines 5 are anaerobic digestion tanks, which are anaerobic digestion treatment steps for decomposing organic substances in organic waste by the biological action of anaerobic microorganisms.

Further, 6 is a solubilization treatment tank which is a solubilization treatment step for solubilizing the organic solid waste, the anaerobic digestion sludge, and / or the excess sludge which is at least a part of the sludge separated and settled. The solubilization treatment tank 6 is provided with an air diffuser 8 at the bottom and is an organic substance that forms sludge by aeration with an oxygen-containing gas such as air under a high temperature condition of 40 to 100 ° C. Is a thermophilic microbial solubilization treatment tank for aerobically treating and solubilizing aerobic organisms, but is not limited thereto. The solubilization treatment tank 6 is provided with a heating means (not shown) such as steam for heating the sludge in the treatment tank.

In FIG. 2, 9 is a sludge concentrating device such as a centrifugal separator which is a process for concentrating excess sludge, and
In FIG. 3, reference numeral 10 denotes a solid substance concentrating device which is a solid substance concentration step of concentrating the solid substance in the organic solid waste crushed by the crusher 4. The solid matter concentrating device 10 may be shared with the sludge concentrating device 9,
Further, the crusher 4 for subdividing the organic solid waste does not necessarily have to be provided depending on the processed material.

Further, in the above-mentioned embodiment, a normal activated sludge treatment device is used in the aerobic biological treatment step, but a fixed bed filled with a biological support carrier such as synthetic resin or fibrous material is fixed. It may be a fluidized bed type biological treatment tank in which a biological treatment tank or a biological support carrier is fluidly filled. Further, in the anaerobic digestion treatment step, although it is a single-tank treatment by an anaerobic digestion tank, it may be a two-tank treatment combining an acid fermentation tank and an anaerobic digestion tank, and the like. In the solubilization treatment process, a thermophilic microbial solubilization method using a thermophilic aerobic microorganism is used, but an alkali solubilization method that decomposes in an alkaline manner, an ultrasonic solubilization method that solubilizes by ultrasonic waves, and various other known solubilization methods The method can be used as appropriate.

Further, although it is preferable to use a sedimentation tank as the sludge separation tank in the solid-liquid separation step, a filtration membrane separation device or the like may be used, and the sludge concentration apparatus in the sludge concentration step uses a centrifugal separator. However, a filtration membrane separation device or a filtration device may be used. A heat exchanger for exchanging heat between the concentrated sludge solid-liquid separated in the sludge separation tank and the sludge solubilized in the solubilization treatment tank may be provided.

Next, a treatment method for treating organic waste by the organic waste treatment apparatus having the configuration of FIG. 1 will be described in detail below. The organic wastewater of the organic waste is supplied from the raw water supply flow path 20 to the flow rate adjusting tank 1 and temporarily stored, and after adjusting the pH value and the like as necessary, the wastewater supply amount is adjusted to adjust the raw water. By supplying the activated sludge from the supply channel 21 to the activated sludge treatment tank 2 and aerating with the oxygen-containing gas such as the air supplied from the air diffusing means 8, the activated sludge, which is a floating aerobic microorganism, has a biological effect. , Organic matter in raw water is efficiently oxidatively decomposed. The treatment temperature in the activated sludge treatment tank 2 is preferably 10 to 45 ° C.

The mixed liquid in which the sludge grown in the activated sludge treatment tank 2 is mixed is introduced into the sludge separation tank 3 from the mixed liquid discharge passage 22 and left to stand to allow the sludge to spontaneously settle and separate to be cleaned. The treated water thus treated is discharged from the treated water discharge channel 23 to the outside of the system. The sludge settled and separated in the sludge separation tank 3 is extracted from the sludge extraction flow path 24 of the sludge separation tank 3, and a part of the sludge is returned from the sludge return flow path 25 to the activated sludge treatment tank 2 as return sludge. It The remaining separated sludge is extracted from the surplus sludge supply channel 26, and a part thereof is discharged from the sludge discharge channel 32 to the outside of the system and treated by a sludge treatment device (not shown) or the like. The remaining excess sludge is supplied to the solubilization treatment tank 5.

On the other hand, the organic solid waste among the organic waste is supplied from the solid waste supply passage 28 to the crusher 4, and after the relatively large solid matter is fragmented, the crushed waste is supplied. It is supplied to the anaerobic digestion tank 5 from the flow path 29, and in an anaerobic state, the temperature is 25 to 75 ° C, preferably 45 to 60 ° C.
By treating with a residence time of 24 hours to 2 weeks, organic matter in the solid matter is efficiently reduced and decomposed by the biological action of floating anaerobic microorganisms, and the gas mainly generated is methane gas. It is discharged from the system 31 to the outside of the system, optionally desulfurized, and then stored in a gas holder or the like and used as fuel gas or the like. In the crusher 4, the solid matter is subdivided into 10 mm or less, but preferably 2 mm or less.

The anaerobic digested solid waste is supplied to the solubilization treatment tank 6 as digestion sludge from the solubilization digestion sludge supply channel 30. The excess sludge and digested sludge supplied to the solubilization treatment tank 5 contain oxygen such as air supplied from the aeration means 8 at a temperature of 45 to 75 ° C., preferably 55 to 70 ° C., and a residence time of 10 to 100 hours. By aeration with gas, the microorganisms in the sludge are efficiently killed and decomposed by the biological action of the thermophilic aerobic microorganisms, and solubilized as low-molecularized organic matter. Further, there may be provided a step of supplying at least a part of the excess sludge to the anaerobic digestion tank 5 from the excess sludge supply flow path 26a and performing an anaerobic digestion treatment similar to the solid waste. The step of circulating and supplying the digested sludge that has been subjected to the digestive digestion treatment to the activated sludge treatment tank 2 from the digested sludge circulation channel 30a may be performed. In the solubilization treatment tank 5, by using a high-concentration oxygen-containing gas, the oxygen dissolution efficiency can be made extremely high,
It is preferable because the treatment efficiency is also high.

The sludge solubilized in the solubilization treatment tank 5 is circulated and supplied from the sludge circulation channel 27 to the activated sludge treatment tank 2, and the biology of sludge, which is an aerobic microorganism floating with the organic matter in the raw water. It is possible to reduce the volume of the generated sludge by efficiently oxidizing and decomposing it by a physical action, and to reduce the amount of the generated excess sludge to zero or at least.

Next, a treatment method for treating organic waste by the organic waste treatment apparatus having the configuration of FIG. 2 will be described in detail below. The organic wastewater of the organic waste is supplied from the raw water supply flow path 20 to the flow rate adjusting tank 1 and temporarily stored, and after adjusting the pH value and the like as necessary, the wastewater supply amount is adjusted to adjust the raw water. By supplying the activated sludge from the supply channel 21 to the activated sludge treatment tank 2 and aerating with the oxygen-containing gas such as the air supplied from the air diffusing means 8, the activated sludge, which is a floating aerobic microorganism, has a biological effect. , Organic matter in raw water is efficiently oxidatively decomposed.

The mixed liquid in which the sludge grown in the activated sludge treatment tank 2 is mixed is introduced into the sludge separation tank 3 from the mixed liquid discharge channel 22, and the sludge is naturally settled and separated by standing and cleaned. The treated water thus treated is discharged from the treated water discharge channel 23 to the outside of the system. The sludge settled and separated in the sludge separation tank 3 is extracted from the sludge extraction flow path 24 of the sludge separation tank 3, and a part of the sludge is returned from the sludge return flow path 25 to the activated sludge treatment tank 2 as return sludge. It The remaining separated sludge is extracted from the excess sludge extraction flow path 26, and a part of the separated sludge is discharged to the outside of the system from the sludge discharge flow path 32 and processed by a sludge treatment device (not shown) or the like. The remaining excess sludge is supplied from the excess sludge supply channel 26 to the sludge concentrating device 9 and concentrated, and then supplied from the concentrated sludge supply channel 33 to the solubilization treatment tank 6. The sludge concentration of the sludge that has been concentrated is 2-1.
0 wt% is preferable, and if the sludge concentration is lower than 2 wt%, there are problems such as a decrease in processing speed and a large amount of heating energy, and if it is higher than 10 wt%, mixing becomes difficult due to a decrease in fluidity. However, there is a problem that the processing efficiency decreases.

On the other hand, the organic solid waste among the organic waste is supplied to the crusher 4 from the solid waste supply flow path 28, and after the relatively large solids are fragmented, the crushed waste is supplied. The organic substances in the solid matter are efficiently reduced and decomposed by the biological action of the floating anaerobic microorganisms supplied to the anaerobic digestion tank 5 from the flow path 29, and the generated gas mainly generated methane gas is discharged. It is discharged from the flow path 31 to the outside of the system, optionally desulfurized, stored in a gas holder or the like, and used as fuel gas or the like.

The anaerobic digested solid waste is supplied as digestion sludge from the digestion sludge supply channel 30 to the solubilization treatment tank 6. The excess sludge and digested sludge supplied to the solubilization treatment tank 5 are aerated with an oxygen-containing gas such as air supplied from the air diffusing means 8 to cause biological effects of high temperature aerobic microorganisms, and Microorganisms are efficiently killed and decomposed to become low molecular weight organic matter and solubilized. Further, there may be provided a step of supplying at least a part of the concentrated sludge to the anaerobic digestion tank 5 from the concentrated sludge supply flow path 33a and performing an anaerobic digestion treatment similar to the solid waste. A step of supplying the digested sludge subjected to the sexual digestion treatment to the sludge concentrating device 9 from the digested sludge condensing channel 34a may be provided. The treatment conditions in the activated sludge treatment tank 2, the solubilization treatment tank, the anaerobic digestion tank, etc. are shown in FIG.
It is preferable to carry out under the same conditions as.

The sludge solubilized in the solubilization treatment tank 5 is circulated and supplied from the sludge circulation channel 27 to the activated sludge treatment tank 2, and the biology of sludge, which is an aerobic microorganism floating with the organic matter in the raw water. It is possible to reduce the volume of the generated sludge by efficiently oxidizing and decomposing it by a physical action, and to reduce the amount of the generated excess sludge to zero or at least.

Next, a treatment method for treating organic waste by the organic waste treatment apparatus having the configuration of FIG. 3 will be described in detail below. The organic wastewater of the organic waste is supplied from the raw water supply flow path 20 to the flow rate adjusting tank 1 and temporarily stored, and after adjusting the pH value and the like as necessary, the wastewater supply amount is adjusted to adjust the raw water. By supplying the activated sludge from the supply channel 21 to the activated sludge treatment tank 2 and aerating with the oxygen-containing gas such as the air supplied from the air diffusing means 8, the activated sludge, which is a floating aerobic microorganism, has a biological effect. , Organic matter in raw water is efficiently oxidatively decomposed.

The mixed liquid in which the sludge grown in the activated sludge treatment tank 2 is mixed is introduced into the sludge separation tank 3 from the mixed liquid discharge channel 22 and left to stand to allow the sludge to spontaneously settle and separate, and to be cleaned. The treated water thus treated is discharged from the treated water discharge channel 23 to the outside of the system. The sludge settled and separated in the sludge separation tank 3 is extracted from the sludge extraction flow path 24 of the sludge separation tank 3, and a part of the sludge is returned from the sludge return flow path 25 to the activated sludge treatment tank 2 as return sludge. It The remaining separated sludge is extracted from the excess sludge extraction flow path 26, and a part of the separated sludge is discharged to the outside of the system from the sludge discharge flow path 32 and processed by a sludge treatment device (not shown) or the like. The remaining excess sludge is supplied from the excess sludge supply channel 26 to the sludge concentrating device 9 and concentrated, and then supplied from the concentrated sludge supply channel 33 to the solubilization treatment tank 6. The sludge concentration of the sludge that has been concentrated is 2-1.
0 wt% is preferable, and if the sludge concentration is lower than 2 wt%, there are problems such as a decrease in processing speed and a large amount of heating energy, and if it is higher than 10 wt%, mixing becomes difficult due to a decrease in fluidity. However, there is a problem that the processing efficiency decreases.

On the other hand, the organic solid waste of the organic waste is supplied from the solid waste supply passage 28 to the crusher 4, and after the relatively large solids are fragmented, the crushed waste is supplied. The solid content concentrator 10 is supplied from the flow path 29.
After the solid matter in the organic solid waste supplied to the solid matter concentrating device 10 is concentrated, it is supplied to the anaerobic digestion tank 5 from the concentrated solid matter supply channel 35, and the biological matter of the floating anaerobic microorganisms is supplied. By the action, the organic matter in the solid matter is efficiently reduced and decomposed, and the produced gas mainly composed of the generated methane gas is discharged from the system through the gas discharge passage 31 and, if necessary, desulfurized and then stored in a gas holder or the like. And used as fuel gas.

The anaerobic digested solid waste is supplied to the solubilization treatment tank 6 as digestion sludge from the solubilization digestion sludge supply channel 30. The excess sludge and digested sludge supplied to the solubilization treatment tank 5 are aerated with an oxygen-containing gas such as air supplied from the air diffusing means 8 to cause biological effects of high temperature aerobic microorganisms, and Microorganisms are efficiently killed and decomposed to become low molecular weight organic matter and solubilized. Further, a step of supplying at least a part of the solid matter concentrated by the solid matter concentrating device 10 directly to the solubilization treatment tank 6 from the concentrated solid matter supply flow path 35a, the digested sludge subjected to the anaerobic digestion treatment is digested sludge concentrated. You may provide the process etc. which supply to the sludge condensing device 9 from the flow path 34a. Further, a step of circulating and supplying the digested sludge that has been subjected to the anaerobic digestion treatment to the activated sludge treatment tank 2 from the digested sludge circulation flow channel 30a may be adopted.
The treatment conditions in the activated sludge treatment tank 2, the solubilization treatment tank, the anaerobic digestion tank, the sludge concentrator and the like are preferably the same as those shown in FIGS. 1 and 2.

The sludge solubilized in the solubilization treatment tank 5 is circulated and supplied from the sludge circulation channel 27 to the activated sludge treatment tank 2, and the biology of sludge which is an aerobic microorganism floating with the organic matter in the raw water. It is possible to reduce the volume of the generated sludge by efficiently oxidizing and decomposing it by a physical action, and to reduce the amount of the generated excess sludge to zero or at least.

[0042]

INDUSTRIAL APPLICABILITY The present invention can reduce the amount of surplus sludge generated in biological wastewater treatment to at least zero, or at least reduce the volume of the facility, and can downsize the facility. Can be cheaper. At the same time, it is a method for treating organic waste, which is capable of producing methane gas from excess sludge and / or organic solid waste and recycling the produced methane gas as fuel or the like.

[Brief description of drawings]

FIG. 1 is a system diagram of an organic waste treatment device according to an embodiment of the present invention.

FIG. 2 is a system diagram of an organic waste treatment device according to another embodiment of the present invention.

FIG. 3 is a system diagram of an organic waste treatment device according to another embodiment of the present invention.

[Explanation of symbols]

1: Flow rate adjustment tank 2: Aerobic biological treatment process (activated sludge treatment tank) 3: Solid-liquid separation process (sludge separation tank) 4: Crusher 5: Anaerobic digestion process (anaerobic digester) 6: Solubilization treatment process (solubilization treatment tank) 7, 8: Aeration means 9: Sludge concentrator 10: Solid concentration device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 11/04 B09B 3/00 D

Claims (2)

[Claims] 1. An aerobic biological treatment step of aerobically treating organic wastewater, a solid-liquid separation step of solid-liquid separation of sludge in a biologically treated mixed liquid, and at least a part of the separated sludge. A sludge returning step of returning the sludge to the aerobic biological treatment step as a returning sludge, and a solubilization processing step of solubilizing at least a part of the remaining sludge as an excess sludge, and anaerobic organic solid waste. Anaerobic digestion treatment step of biological treatment with oxidative property, digestive sludge supply step of supplying digested sludge subjected to anaerobic digestion treatment to the aerobic biological treatment step and / or the solubilization treatment step, and solubilized treatment A method for treating organic waste, comprising a solubilized sludge returning step for returning solubilized sludge to the aerobic biological treatment step. 2. The method according to claim 1, wherein a concentration step for concentrating excess sludge and / or organic solid matter is provided, and at least a part of the concentrated solid matter is supplied to the anaerobic digestion treatment step to perform anaerobic biological treatment. Of organic waste treatment.