JP2020015028A - Sludge treatment system, sludge treatment method and organic wastewater treatment system - Google Patents

Abstract

To provide a sludge treatment system, a sludge treatment method, and an organic wastewater treatment system, that can more efficiently recover energy resources from sludge generated by organic wastewater treatment.SOLUTION: A sludge treatment system of an embodiment is a sludge treatment system for recovering energy resources from sludge generated in an organic wastewater treatment facility including a first settling basin, a biological reaction tank and a final settling basin, including: a first sludge treatment section and a second sludge treatment section. The first sludge treatment section decomposes a sludge derived from the first settling basin into digested gas and digested sludge by anaerobic digestion treatment. The second sludge treatment section recovers energy resources from the digested sludge generated in the first sludge treatment section and a surplus sludge derived from the final settling basin and not subjected to anaerobic digestion treatment, or performs disposing of the digested sludge and the surplus sludge.SELECTED DRAWING: Figure 2

Description

  Embodiments of the present invention relate to a sludge treatment system, a sludge treatment method, and an organic wastewater treatment system.

  Conventionally, attempts have been made to recover energy resources from sludge generated in organic wastewater treatment. The organic wastewater treatment facility includes a biological reaction tank that decomposes pollutants in wastewater by utilizing the action of microorganisms. In the case of treating wastewater containing a large amount of solids, a pretreatment facility (for example, a first settling basin or the like) for separating relatively large solids is often provided in a stage preceding the biological reaction tank. In an organic wastewater treatment facility equipped with such a pretreatment facility, when an attempt is made to recover energy resources from sludge generated in both the biological reaction tank and the pretreatment facility, the conventional method requires an investment for recovering energy resources. It may not be possible to recover enough energy resources for the cost.

Japanese Patent No. 5,801,769 Japanese Patent No. 3391941

  An object of the present invention is to provide a sludge treatment system, a sludge treatment method, and an organic wastewater treatment system that can more efficiently recover energy resources from sludge generated in organic wastewater treatment.

  A sludge treatment system according to an embodiment is a sludge treatment system for recovering energy resources from sludge generated in an organic wastewater treatment facility including a first settling basin, a biological reaction tank, and a final settling basin. It has a sludge treatment unit. The first sludge treatment section decomposes the sludge derived from the first settling pond into digestion gas and digestive sludge by anaerobic digestion treatment. The second sludge treatment section recovers energy resources from the digested sludge generated in the first sludge treatment section and excess sludge from the final sedimentation basin and not subjected to anaerobic digestion treatment, or Disposing of the digested sludge and the surplus sludge.

The figure which shows the example of a structure of the conventional sludge processing system 90. The figure which shows the example of a structure of the sludge processing system 100a of 1st Embodiment. The figure which shows the example of a structure of the sludge processing system 100b of 2nd Embodiment. The figure which shows the example of a structure of the sludge processing system 100c of 3rd Embodiment. The figure which shows the example of a structure of the sludge processing system 100d of 4th Embodiment.

  Hereinafter, a sludge treatment system, a sludge treatment method, and an organic wastewater treatment system according to an embodiment will be described with reference to the drawings.

(Summary)
FIG. 1 is a diagram showing a configuration example of a conventional sludge treatment system 90. The sludge treatment system 90 is a system that recovers energy resources from sludge by treating sludge supplied from the organic wastewater treatment system 80 by anaerobic digestion. Anaerobic digestion refers to the decomposition of organic matter by microorganisms under anaerobic conditions in the absence of oxygen. For example, the sludge treatment system 90 collects digestive gas and charcoal generated by anaerobic digestion, concentration, dehydration, and carbonization of sludge as energy resources.

  First, the configuration of the organic wastewater treatment system 80 will be described. The organic wastewater treatment system 80 includes a first settling basin 1, a biological reaction tank 2, and a final settling basin 3. First, the sedimentation basin 1 is a reservoir into which organic wastewater to be purified by the organic wastewater treatment system 80 flows. Hereinafter, the organic wastewater from first flowing into the sedimentation basin 1 until it becomes treated is referred to as “treated water”, and the treated treated water is referred to as “treated water”. First, in the sedimentation basin 1, solid matter having a relatively large specific gravity is separated from the water to be treated by gravity sedimentation and sedimentation. First, the supernatant water from which solids are separated in the sedimentation basin 1 is sent to the biological reaction tank 2 at the subsequent stage. The settled sludge (primary sludge) is first withdrawn from the sedimentation basin 1 and sent to the sludge treatment system 90.

  In the biological reaction tank 2, pollutants contained in the water to be treated are decomposed by the action of microorganisms contained in the activated sludge. The water to be treated in which the pollutants have been decomposed is sent to the final sedimentation basin 3 at the subsequent stage.

  In the final settling basin 3, solids such as activated sludge remaining in the water to be treated are separated from the water to be treated by sedimentation by gravity sedimentation. The supernatant water from which solids have been separated in the final sedimentation basin 3 is subjected to advanced treatment such as sand filtration or chlorination if necessary, and then discharged to public water bodies or the like as treated water. A part of the sludge deposited on the bottom of the final sedimentation basin 3 (return sludge) is returned to the upstream part of the biological reaction tank 2 for reuse in biological treatment. Excess sludge (excess sludge) excluding returned sludge is withdrawn from the final sedimentation basin 3 and sent to the sludge treatment system 90.

  Next, the configuration of the sludge treatment system 90 will be described. The sludge treatment system 90 includes an initial sludge thickening tank 4, an excess sludge thickening machine 5, an anaerobic digestion tank 6, a sludge dewatering machine 7, and a carbonization furnace 8. The first sludge thickening tank 4 is a thickening tank for the first sludge sent from the first settling basin 1. The first settling sludge thickening tank 4 sends the thickened sludge to the anaerobic digestion tank 6 and also returns the separated liquid obtained by the thickening to the first settling tank 1.

  The surplus sludge concentrator 5 is a device that condenses surplus sludge sent from the final settling basin 3. The excess sludge concentrator 5 sends the concentrated sludge to the anaerobic digestion tank 6 and returns the separated liquid obtained by the concentration to the final sedimentation basin 1.

  The anaerobic digester 6 is a digester for the concentrated sludge sent from the initial sludge thickener 4 and the excess sludge thickener 5. The concentrated sludge is decomposed by anaerobic digestion into digested sludge and digested gas containing methane, carbon dioxide, hydrogen and the like. While the generated digestive gas is recovered as an energy resource, the digested sludge is sent to the sludge dewatering machine 7.

  The sludge dewatering machine 7 is a device for dewatering digested sludge sent from the anaerobic digestion tank 6. The sludge dewatering machine 7 sends the dewatered sludge (dewatered sludge) to the carbonization furnace 8 and also returns the desorbed liquid obtained by the dewatering to the precipitation tank 1 first.

  The carbonization furnace 8 is a device that carbonizes the dewatered sludge sent from the sludge dewatering machine 7. The coal generated by the carbonization furnace 8 is recovered as an energy resource.

  According to the conventional sludge treatment system 90 having such a configuration, energy resources can be recovered from the sludge generated in the organic wastewater treatment system 80. However, in the conventional sludge treatment system 90, energy resources are efficiently treated by similarly treating the initial sludge extracted from the sedimentation basin 1 and the excess sludge extracted from the final sedimentation basin 3 in the anaerobic digestion tank 6. In some cases, it could not be collected well.

  According to the sludge treatment system of each embodiment described below, it becomes possible to recover energy resources more efficiently than the above-described conventional sludge treatment system 90.

(First embodiment)
FIG. 2 is a diagram illustrating a configuration example of the sludge treatment system 100a according to the first embodiment. The sludge treatment system 100a differs from the conventional sludge treatment system 90 in that the sludge sent to the surplus sludge concentrator 5, the anaerobic digestion tank 6, and the sludge dewatering machine 7, or the sludge sent from the sludge source or destination is different. The other configuration of the sludge treatment system 100a is the same as that of the conventional sludge treatment system 90. Therefore, the same components are denoted by the same reference numerals as those in FIG.

  More specifically, the sludge treatment system 100a is different from the sludge treatment system 100a in that the concentrated sludge from the excess sludge thickener 5 is sent to the sludge dewatering machine 7, and the anaerobic digestion tank 6 is dedicated to the first sludge sent from the first sludge thickening tank 4. A conventional sludge treatment system is used in that it is used as a digestion tank, and the sludge dewatering machine 7 dehydrates the concentrated sludge sent from the excess sludge concentrator 5 in addition to the digested sludge sent from the anaerobic digestion tank 6. Different from 90.

  The initial sludge thickening tank 4 may be a centrifugal thickener. Further, the excess sludge concentrator 5 may be a centrifugal concentrator or a sludge concentrator. Further, the sludge dewatering machine 7 may be a centrifugal dewatering machine or a press machine such as a belt press, a screw press, and a filter press. Further, the carbonization furnace 8 may be an incinerator, a sludge composting facility, or the like.

  According to the sludge treatment system 100a of the first embodiment configured as described above, it becomes possible to recover energy resources more efficiently than the sludge treatment system 90 of the conventional configuration.

  In general, the initial settled sludge in the first settling basin often has properties that are easily decomposed by anaerobic microorganisms, and the excess sludge in the final settled basin is often difficult to be decomposed by anaerobic microorganisms. Therefore, when the initial settled sludge and the excess sludge are mixed and digested and decomposed, it is necessary to secure the residence time of the sludge in the anaerobic digestion tank in accordance with the decomposition rate of the excess sludge that is hardly decomposed by the anaerobic microorganisms. . This means that the primary sludge, which is originally degraded in a shorter time than the surplus sludge, must stay in the anaerobic digestion tank until the surplus sludge is decomposed. Therefore, in the conventional sludge treatment system, the volume of the anaerobic digestion tank has to be increased more than necessary.

  On the other hand, in the sludge treatment system 100a of the first embodiment, the decomposition rate of sludge can be increased by using the anaerobic digestion tank 6 as a digestion tank dedicated to initial sludge. Thereby, the equipment scale of the anaerobic digestion tank 6 can be reduced. In addition, by using the anaerobic digestion tank 6 as a digestion tank dedicated to initial sludge, an improvement in sludge decomposition rate is expected. Thereby, it is possible to reduce the energy required for heating the anaerobic digestion tank 6 for the purpose of maintaining the decomposition efficiency.

  As described above, in the sludge treatment system 100a according to the first embodiment, the facility cost or the operation cost of the sludge treatment can be reduced, so that the efficiency of recovering energy resources can be improved.

(Second embodiment)
FIG. 3 is a diagram illustrating a configuration example of a sludge treatment system 100b according to the second embodiment. The sludge treatment system 100b is different from the sludge treatment system 100a of the first embodiment in that the sludge treatment system 100b further includes a digestion sludge dehydrator 9 and that a surplus sludge dehydrator 10 is provided in place of the sludge dehydrator 7. Other configurations of the sludge treatment system 100b are the same as those of the sludge treatment system 100a of the first embodiment, and the same components are denoted by the same reference numerals as in FIG.

  Specifically, digestion sludge dewatering machine 9 dehydrates digestion sludge generated in anaerobic digestion tank 6 and sends the dewatered sludge to carbonization furnace 8. The surplus sludge dewatering machine 10 is different from the sludge dewatering machine 7 in the first embodiment in that the surplus sludge dewatering machine 10 is used as a dewatering machine dedicated to the concentrated sludge generated by the surplus sludge concentrating machine 5. The digested sludge dewatering machine 9 and the surplus sludge dewatering machine 10 may be centrifugal dewatering machines or press machines such as a belt press, a screw press, and a filter press. In this case, the dewatered sludge generated by each of the excess sludge dewatering machine 10 and the digested sludge dewatering machine 9 is sent to the carbonization furnace 8.

  According to the sludge treatment system 100b of the second embodiment configured as described above, it becomes possible to recover energy resources more efficiently than the sludge treatment system 90 of the conventional configuration.

  Specifically, in general, digested sludge generated by digestion and decomposition of primary sludge has relatively high dewatering properties, but concentrated sludge derived from excess sludge is not stabilized by coagulation with a flocculant, and good dewatering is performed. In many cases, the property cannot be obtained. This is because the properties of the initial settled sludge and the excess sludge are significantly different due to the influence of seasonal fluctuations and the like. Such a difference in properties affects conditions such as the type of coagulant added to sludge as a pretreatment for dehydration and the rate of addition. Therefore, in the sludge treatment system 100a of the first embodiment in which digested sludge derived from primary sludge and concentrated sludge derived from surplus sludge are dehydrated by the same sludge dewatering machine 7, fluctuations in properties and mixing ratios of digested sludge and concentrated sludge are performed. As a result, sludge dewatering treatment may be difficult.

  On the other hand, the sludge treatment system 100b of the second embodiment is configured to dewater digested sludge derived from primary sludge and surplus sludge by different dehydrators (digestion sludge dehydrator 9 and excess sludge dehydrator 10). By providing, the sludge can be dehydrated stably. Specifically, the type or injection rate of chemicals such as a dehydration method, a coagulant added to sludge, a pH adjuster, etc., depends on the type of sludge (digested sludge derived from primary sludge or concentrated sludge derived from excess sludge). It can be optimized accordingly. This makes it possible to reduce the chemical injection rate and downsize the dehydrator by improving the processing efficiency.

  As described above, in the sludge treatment system 100b according to the second embodiment, the facility cost or the operation cost relating to the dewatering of sludge can be suppressed, so that the efficiency of recovering energy resources can be further improved.

(Third embodiment)
FIG. 4 is a diagram illustrating a configuration example of a sludge treatment system 100c according to the third embodiment. The sludge treatment system 100c differs from the conventional sludge treatment system 90 in that the destination of the separated liquid of the excess sludge concentrator 5 and the destination of the desorbed liquid of the sludge dehydrator 7 are different. The other configuration of the sludge treatment system 100c is the same as that of the conventional sludge treatment system 90, and the same components are denoted by the same reference numerals as those in FIG.

  Specifically, the sludge treatment system 100c is different from the conventional sludge in that the separated liquid of the excess sludge concentrator 5 and the desorbed liquid of the sludge dewaterer 7 are first returned to the biological reaction tank 2 instead of the settling tank 1. Different from the processing system 90.

  According to the sludge treatment system 100c of the third embodiment configured as described above, it becomes possible to recover energy resources more efficiently than the sludge treatment system 90 of the conventional configuration.

  In general, solid matter is not completely recovered in the excess sludge concentrator 5 or the sludge dewatering machine 7, and a part of the solid remains in the desorbed liquid (or separated liquid). I can't. For this reason, in the sludge treatment system 90 having the conventional configuration, the desorbed liquid is first returned to the sedimentation basin 1 to perform a purification treatment, and then discharged from the final sedimentation basin 3 as treated water. However, since the desorbed liquid contains a large amount of hardly decomposable solids such as excess sludge and residues of anaerobic digestion in the anaerobic digestion tank 6, even if this is sent to the anaerobic digestion tank 6 again, it is sufficient. There is little prospect of recovering energy resources. Circulating hard-to-degrade solids also increases the processing load on the first settling basin 1, the first settling sludge thickening tank 4, and the anaerobic digestion tank 6.

  On the other hand, in the sludge treatment system 100c of the third embodiment, the separated liquid of the excess sludge concentrator 5 and the desorbed liquid of the sludge dewatering machine 7 are first returned to the biological reaction tank 2 instead of the settling tank 1. Thereby, the processing load on the first settling basin 1, the first settling sludge concentration tank 4, and the anaerobic digestion tank 6 can be reduced, and the efficiency of recovering energy resources can be improved.

(Fourth embodiment)
FIG. 5 is a diagram illustrating a configuration example of a sludge treatment system 100d according to the fourth embodiment. The sludge treatment system 100d is different from the second sludge treatment system 100b in that the destination of the separation liquid of the excess sludge concentrator 5 and the separation liquid of the digestion sludge dehydrator 9 and the excess sludge dehydrator 10 are different. The other configuration of the sludge treatment system 100d is the same as that of the second sludge treatment system 100b, and the same components are denoted by the same reference numerals as in FIG.

  Specifically, the sludge treatment system 100d returns the separated liquid of the excess sludge concentrator 5 and the desorbed liquid of the digested sludge dewatering machine 9 and the excess sludge dewatering machine 10 to the biological reaction tank 2 instead of the sedimentation pond 1 at first. This is different from the sludge treatment system 100b of the second embodiment in that the

  According to the sludge treatment system 100d of the fourth embodiment configured as described above, it is possible to recover energy resources more efficiently than the sludge treatment system 90 of the conventional configuration.

  Specifically, in the sludge treatment system 100d of the fourth embodiment, the separated liquid of the surplus sludge concentrator 5 and the desorbed liquid of the digested sludge dewatering machine 9 and the surplus sludge dewatering machine 10 are not initially settled in the sedimentation tank 1 By returning to the biological reaction tank 2, the processing load of the first settling basin 1, the first settling sludge thickening tank 4 and the anaerobic digestion tank 6 is reduced as in the third embodiment, and the recovery efficiency of energy resources is improved. Can be improved.

  According to at least one embodiment described above, first, an anaerobic digestion tank 6 (an example of a first sludge treatment unit) that decomposes sludge derived from the sedimentation basin 1 into digestion gas and digested sludge by anaerobic digestion treatment. A carbonization unit 8 (a second sludge treatment unit) for recovering energy resources from digested sludge generated in the anaerobic digestion tank 6 and excess sludge derived from the final settling basin 1 and not subjected to the anaerobic digestion treatment. Example), or by having facilities (an example of a second sludge treatment unit) such as an incinerator or sludge composting facility that disposes digested sludge and excess sludge, enables more efficient removal of sludge generated by organic wastewater treatment. Energy resources can be recovered.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

100a, 100b, 100c, 100d: Sludge treatment system of the embodiment, 80: Organic wastewater treatment system, 90: Sludge treatment system of conventional configuration, 1 ... First settling tank, 2 ... Biological reaction tank, 3 ... Final settling tank, 4 ... First sludge thickening tank, 5 ... Sludge sludge thickener, 6 ... Anaerobic digestion tank, 7 ... Sludge dewatering machine, 8 ... Carbonization furnace, 9 ... Digestion sludge dewatering machine, 10 ... Excess sludge dewatering machine

Claims (10)

A sludge treatment system for recovering energy resources from sludge generated in an organic wastewater treatment facility including a first settling basin, a biological reaction tank, and a final settling basin,
A first sludge treatment section that decomposes the sludge derived from the first settling basin into digestion gas and digested sludge by anaerobic digestion treatment;
Recovering energy resources from the digested sludge generated in the first sludge treatment section and excess sludge from the final sedimentation basin and not subjected to anaerobic digestion treatment, or the digested sludge and the excess sludge A second sludge treatment unit that performs waste treatment of
Sludge treatment system comprising: A concentrator for concentrating the excess sludge,
A dehydrator that dewaters the digested sludge and the excess sludge concentrated by the concentrator and supplies the sludge to the second sludge processing unit;
Further comprising,
The sludge treatment system according to claim 1. The separated liquid obtained by the concentrator and the desorbed liquid obtained by the dehydrator are returned to the first precipitation tank,
The sludge treatment system according to claim 2. The separated liquid obtained by the concentrator and the desorbed liquid obtained by the dehydrator are returned to the biological reaction tank,
The sludge treatment system according to claim 2. A first dehydrator for dehydrating the digested sludge and supplying the digested sludge to the second sludge treatment unit;
A concentrator for concentrating the excess sludge,
A second dehydrator for dehydrating the excess sludge concentrated by the concentrator and supplying the sludge to the second sludge treatment unit;
Further comprising,
The sludge treatment system according to claim 1. Returning the separated liquid obtained by the concentrator and the desorbed liquid obtained by the first dehydrator and the second dehydrator to the first precipitation tank,
The sludge treatment system according to claim 5. Returning the separated liquid obtained by the concentrator and the desorbed liquid obtained by the first dehydrator and the second dehydrator to the biological reaction tank,
The sludge treatment system according to claim 5. The digested sludge generated in the anaerobic digestion unit, and further comprising a carbonization unit for carbonizing excess sludge that has not been subjected to anaerobic digestion treatment, which is sludge derived from the final sedimentation basin, as the second sludge treatment unit,
The sludge treatment system according to any one of claims 1 to 7. A sludge treatment method for recovering energy resources from sludge generated in an organic wastewater treatment facility including a first settling basin, a biological reaction tank, and a final settling basin,
A first sludge treatment step of decomposing the sludge derived from the first settling basin into digestion gas and digestive sludge by anaerobic digestion treatment;
Recovering energy resources from the digested sludge generated in the first sludge treatment step and excess sludge derived from the final settling basin and not subjected to anaerobic digestion treatment, or recovering the digested sludge and the excess sludge A second sludge treatment step of performing a waste treatment,
A sludge treatment method comprising: An organic wastewater treatment facility comprising a first settling basin, a biological reactor and a final settling basin;
The sludge treatment system according to any one of claims 1 to 8, wherein the sludge treatment system recovers energy resources from sludge generated in the organic wastewater treatment facility,
An organic wastewater treatment system comprising:

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