JP2005254199A - Wastewater treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for wastewater treatment, which enable a reduction in the amount of excess sludge production and a production and recovery of a large amount of biogas useful as energy. <P>SOLUTION: In this wastewater treatment apparatus 10, particulate organic sludge is also coagulated and separated in a coagulation sedimentation tank 12 installed upstream of a biological treatment tank 14. Therefore, the concentration of the organic matter in the wastewater flowed into the biological treatment tank 14 can be suppressed to reduce the amount of excess sludge production. Further, the particles of the organic sludge separated in the coagulation sedimentation tank 12, together with the excess sludge separated in a sedimentation tank 16, are refined in a refinement treatment apparatus 18 and are then subjected to digestion treatment in an anaerobic digestion treatment tank 20 with good efficiency. This can reduce the amount of sludge discharged from a sludge discharge pipe 44 to the outside of the system and can produce a large amount of methane gas which can be recovered through a biogas evolution pipe 42. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wastewater treatment method and apparatus, and more particularly, to a wastewater treatment method and apparatus for generating and recovering biogas useful as energy by anaerobic digestion of sludge generated in wastewater treatment.

  Conventionally, as a method for treating organic wastewater such as sewage (hereinafter referred to as wastewater), an activated sludge treatment method that aerobically biotreats has been adopted, but there has been a problem of generation of excess sludge. .

  In order to deal with this problem, various methods for reducing excess sludge have been studied. In particular, anaerobic digestion treatment that uses anaerobic microorganisms to treat excess sludge has a relatively low treatment cost. Since there is an advantage that the amount of sludge generated is small and biogas useful as energy can be generated and recovered, it is adopted as an effective treatment of excess sludge.

In order to efficiently perform the anaerobic digestion treatment of the excess sludge, it is preferable to solubilize the excess sludge and then perform the anaerobic digestion treatment. In Patent Document 1, the surplus sludge is first physically, chemically, or mechanically treated. A method of anaerobic digestion of the crushed and sonicated material is disclosed. Patent Document 2 discloses a method of performing anaerobic digestion treatment again after physicochemical and / or mechanically decomposing surplus sludge subjected to anaerobic digestion treatment. Further, Patent Document 3 discloses a method for performing anaerobic digestion on surplus sludge obtained by circulating a biological liquefaction process and a physicochemical and / or mechanical liquefaction process. ing.
JP 2002-336898 A JP 2002-102896 A JP 2003-190997 A

  However, since excess sludge is inherently poor in digestibility, solubilization requiring large energy is required to significantly improve the digestibility in the anaerobic digestion process. Therefore, the conventional waste water treatment apparatus that performs anaerobic digestion treatment has a problem that it is not always a satisfactory apparatus from the viewpoint of energy saving and energy creation (generation of biogas).

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wastewater treatment method and apparatus that can reduce the amount of excess sludge generated and generate and recover a large amount of biogas useful as energy. To do.

  In order to achieve the above-mentioned object, the invention according to claim 1 performs anaerobic digestion treatment on anaerobic digestion of part or all of the excess sludge generated by the biological treatment while aerobically biologically treating organic wastewater. In the method, the organic sludge is separated from the organic waste water upstream of the biological treatment, and the separated organic sludge is subjected to the anaerobic digestion treatment.

  The organic sludge described here includes organic sludge that is contained in the form of fine particles in the waste water and is difficult to recover only by gravity sedimentation separation.

  According to claim 1, since organic waste sludge mixed with waste water and composed of organic matter is solid-liquid separated, waste water with less organic sludge is biologically treated. It is possible to greatly reduce excess sludge.

  In addition, the separated organic sludge is highly biodegradable, so it can be efficiently decomposed to generate biogas useful as energy and recovered by anaerobic digestion. The amount of discharged sludge can be reduced.

  The organic sludge is preferably separated using a biodegradable flocculant. Since some organic sludge in the wastewater exists in a suspended state in the form of fine particles, the use of a biodegradable flocculant makes it possible to agglomerate the fine organic sludge and efficiently recover it. it can. In addition, since the flocculant contained in the organic sludge can be biodegraded by anaerobic digestion treatment, the amount of discharged sludge discharged out of the system can be greatly reduced.

  The invention according to claim 4 is characterized in that the separated organic sludge according to any one of claims 1 to 3 is subjected to the anaerobic process after performing a physicochemical or mechanical refinement process. It is characterized by being digested. Thereby, organic sludge can be digested more efficiently.

  The invention according to claim 5 is characterized in that a part of the sludge is extracted from the anaerobic digestion process according to any one of claims 1 to 4, refined, and then anaerobically digested again. Thereby, in the anaerobic digestion treatment, the undigested sludge is refined and again subjected to the anaerobic digestion treatment, so that the amount of sludge discharged out of the system can be further reduced and the amount of biogas generated can be increased. it can.

  In order to achieve the above object, the invention according to claim 6 aerobically biotreats organic wastewater in a biological treatment tank, and a part of excess sludge generated in the biological treatment tank by anaerobic digestion treatment means. Alternatively, in the wastewater treatment apparatus for anaerobically digesting the whole, solid-liquid separation means for separating organic sludge from the organic wastewater upstream of the biological treatment tank, and physicochemical or mechanical separation of the organic sludge And a sludge feed means for transferring the organic sludge refined by the refinement treatment means to the anaerobic digestion means.

  According to the sixth aspect, since the wastewater flows into the biological treatment tank after the organic sludge is separated by the solid-liquid separation means, it is possible to reduce the load of organic matter in the biological treatment. Thereby, the amount of excess sludge generated in the biological treatment tank can be reduced. The organic sludge separated by the solid-liquid separation means is supplied to the refinement treatment means via the mud transfer route, and flows into the anaerobic digestion treatment means after the particles are refined, so that it can be efficiently digested. Can do. Thereby, while being able to collect | recover biogas useful as energy, the generation amount of discharge | emission sludge can be reduced significantly.

  In order to achieve the above-mentioned object, the invention according to claim 7 aerobically biotreats organic wastewater in a biological treatment tank and a part of excess sludge generated in the biological treatment tank by anaerobic digestion treatment means. Alternatively, in the wastewater treatment apparatus for anaerobically digesting the whole, solid-liquid separation means for separating organic sludge from the organic wastewater upstream of the biological treatment tank, and the organic material separated by the solid-liquid separation means A transfer path for transferring sludge to the anaerobic digestion treatment means, and a refinement treatment means for drawing out a part of the organic sludge and excess sludge from the anaerobic digestion treatment means and physicochemically or mechanically miniaturizing the sludge. And a return path for returning the organic sludge and excess sludge refined by the refinement treatment means to the anaerobic digestion treatment means.

  According to the seventh aspect, after undigested organic sludge and excess sludge are extracted by the anaerobic digestion processing means and refined by the refinement processing means, they are returned to the anaerobic digestion processing means by the return route and again anaerobic. Sexually digested. Thereby, since the refined sludge is digested in the anaerobic digestion treatment means, the amount of the discharged sludge discharged out of the system can be further reduced, and the amount of generated biogas can be increased.

  The invention described in claim 8 is characterized in that the solid-liquid separation means described in claims 6 and 7 includes a flocculant charging machine for adding a biodegradable flocculant to the organic waste water. .

  In the solid-liquid separation means, by adding a biodegradable flocculant to the wastewater, a large amount of organic sludge can be recovered and the amount of surplus sludge generated can be further reduced. Since the added flocculant has biodegradability, it is digested by the anaerobic digestion treatment means, so that an increase in discharged sludge due to the addition of the flocculant can be suppressed.

  As described above, according to the wastewater treatment method and apparatus according to the present invention, by separating the organic sludge contained in the wastewater before biological treatment, the amount of surplus sludge generated by biological treatment can be reduced and anaerobic. The amount of biogas generated in the sexual digestion process can be increased. Thereby, the waste water treatment useful from the aspect of energy saving, energy creation, and environment can be performed.

  Hereinafter, preferred embodiments of a wastewater treatment method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a configuration of a wastewater treatment apparatus 10 according to the first embodiment of the present invention, which is an example in which a refinement processing unit is provided upstream of an anaerobic digestion processing unit.

  As shown in the figure, the wastewater treatment apparatus 10 is mainly composed of a coagulation sedimentation tank 12, which is a solid-liquid separation means, a biological treatment tank 14, a precipitation tank 16, a refinement treatment tank 18 which is a refinement treatment means, and an anaerobic process. It is comprised from the anaerobic digestion processing tank 20 which is a sex digestion process means.

  In the coagulation sedimentation tank 12, the low concentration organic sludge contained in the wastewater is aggregated and separated from the wastewater by introducing the flocculant into the wastewater flowing in from the inflow pipe 22 and mixing them. . The flocculant to be added is a substance having both biodegradability and aggregability, and for example, chitosan or polyglutamic acid is preferably used. Further, the method for separating the agglomerated organic sludge is not limited to the gravity sedimentation separation of FIG. 1, but may be solid-liquid separation such as centrifugal separation, flotation separation, membrane separation or the like. The separated supernatant liquid is transferred to the biological treatment tank 14 through the drainage transfer pipe 26, and the organic sludge that has been flocculated and separated is drawn out from the organic sludge extraction pipe 28 that is a mud supply path and is refined. It is transferred to.

  The biological treatment tank 14 is biologically decomposed by aeration of air with an aeration apparatus 30 provided at the bottom in a state where the wastewater separated into solid and liquid in the coagulation sedimentation tank 12 is mixed with activated sludge. Then, it is transferred from the treated water transfer pipe 32 to the settling tank 16.

  The sedimentation tank 16 performs solid-liquid separation on the treated water in which activated sludge is mixed, and causes the separated supernatant to flow out from the outflow pipe 34 as treated water. On the other hand, the separated activated sludge is drawn out from the sludge extraction pipe 36, a part of the activated sludge is returned to the biological treatment tank 14 through the sludge return pipe 38 as return sludge, and the remaining is transferred to the refinement treatment tank 18 as excess sludge. Is done.

  The refinement treatment tank 18 is provided after the organic sludge extraction pipe 28 and the sludge extraction pipe 36 are joined, and the organic sludge and the excess sludge are physicochemically processed or mechanically processed to refine fine particles. And transferred to the anaerobic digestion tank 20 through the refined sludge transfer pipe 40. Examples of the physicochemical treatment include alkali treatment, acid treatment, ozone treatment, pulse discharge treatment, hypochlorous acid treatment, and heat treatment. Examples of the mechanical treatment include ultrasonic treatment, homogenizer treatment, jet mill treatment, and ball mill treatment. Note that the miniaturization process may be performed alone or in combination. In FIG. 1, the refining treatment tank 18 is provided after the sludge extraction pipe 36 is joined to the organic sludge extraction pipe 28, but may be provided in the organic sludge extraction pipe 28 before joining.

  In the anaerobic digestion treatment tank 20, the organic sludge and excess sludge refined in the refinement treatment tank 18 are subjected to biological treatment with anaerobic microorganisms under anaerobic conditions, and the organic sludge and excess sludge are digested. In addition, biogas is generated during the decomposition process. The generated biogas is recovered from a biogas recovery pipe 42 provided in the upper portion, and the digested organic sludge and excess sludge are discharged out of the system from the sludge discharge pipe 44 as discharged sludge. In addition, as an anaerobic microorganism, it is preferable to use the microorganisms which decompose an organic substance anaerobically and ferment methane. Thereby, methane gas useful as energy can be generated and recovered.

  Next, the operation of the waste water treatment apparatus 10 according to the first embodiment of the present invention configured as described above will be described.

  The point to be noted in the present invention is not only to reduce the volume of generated sludge, but also to separate organic sludge present in the form of fine particles in the wastewater before biological treatment.

  In the wastewater treatment apparatus 10 of the present invention, since the particulate organic sludge is separated from the wastewater in the coagulation sedimentation tank 12 installed upstream of the biological treatment tank 14, the concentration of organic matter in the wastewater flowing into the biological treatment tank 14 Can be suppressed. Therefore, since the load of the organic substance in the biological treatment tank 14 is reduced, the growth of microorganisms present in the activated sludge can be suppressed, and the amount of surplus sludge generated can be reduced. Moreover, since the organic sludge separated in the coagulation sedimentation tank 12 is easier to biodegrade than the excess sludge, it is efficiently digested in the anaerobic digestion treatment tank 20. Therefore, it is possible to reduce the discharged sludge discharged from the sludge discharge pipe 44 to the outside of the system, and to generate a large amount of methane gas (biogas) and recover it from the biogas recovery pipe 42.

  Therefore, since the wastewater treatment apparatus 10 of the present invention can positively suppress the generation of excess sludge and increase the amount of biogas generated useful as energy, the wastewater treatment is excellent in terms of energy saving and energy creation. Can be performed. Further, depending on the concentration of organic matter in the wastewater, the amount of surplus sludge generated and the amount of digestion can be balanced to reduce the amount of surplus sludge to zero, so that it is possible to carry out useful wastewater treatment from an environmental point of view.

  Further, in the coagulation sedimentation tank 12, by adding a flocculant to the wastewater, organic sludge present at a low concentration in the wastewater, in particular, particulate organic sludge is agglomerated, so that it can be separated and recovered from the wastewater. The amount of organic sludge can be increased. In addition, since chitosan or polyglutamic acid having high biodegradability is used as the flocculant, it can be digested and decomposed by anaerobic microorganisms in the anaerobic digestion treatment tank 20, so that an increase in discharged sludge due to the addition of the flocculant can be suppressed.

  Since the organic sludge separated in the coagulation sedimentation tank 12 is formed into large particles by the coagulation of the coagulant, it is more efficient in the anaerobic digestion treatment tank 20 by refining the particles in the refinement treatment tank 18. Digestible. Moreover, since surplus sludge is low in biodegradability, the solubilization with respect to surplus sludge is accelerated | stimulated by refine | miniaturizing in the refinement processing tank 18, and the digestion efficiency of the surplus sludge in the anaerobic digestion processing tank 20 is improved. Can do.

  FIG. 2 is a block diagram showing the configuration of the waste water treatment apparatus 50 according to the second embodiment of the present invention, which is an example in which the anaerobic digestion treatment means is provided with a miniaturization treatment means. In addition, while the same apparatus and member as the waste water treatment apparatus 10 which is the 1st Embodiment of this invention are described with the same sign, the description is abbreviate | omitted.

  In the wastewater treatment apparatus 50, the organic sludge extraction pipe 28 provided at the bottom of the coagulation sedimentation tank 12 is directly connected to the anaerobic digestion treatment tank 20 as a transfer path and is refined near the anaerobic digestion treatment tank 20. A tank 18 is arranged. At the bottom of the anaerobic digestion treatment tank 20, an anaerobic sludge extraction pipe 52 is installed to convey the sludge extracted from the anaerobic digestion treatment tank 20 to the refinement treatment tank 18. A refined sludge return pipe 54 which is a return path for returning the converted sludge to the anaerobic digestion tank 20 is installed.

  Therefore, organic sludge and excess sludge directly flow into the anaerobic digestion treatment tank 20, but undigested sludge periodically drawn from the anaerobic sludge extraction pipe 52 is refined in the refinement treatment tank 18. And then returned to the anaerobic digestion tank 20. As a result, the sludge in the anaerobic digestion tank 20 is efficiently digested, so that the amount of sludge discharged from the sludge discharge pipe 44 to the outside of the system can be reduced, and methane gas recovered from the biogas recovery pipe 42 ( The amount of biogas) can be increased.

  In the above-described wastewater treatment apparatuses 10 and 50, the number, shape, material, and the like of each member and apparatus are not particularly limited.

  In the refinement processing tank 18, the wastewater treatment apparatus 10 according to the first embodiment is provided between the coagulation sedimentation tank 12 and the anaerobic digestion treatment tank 20, and the wastewater treatment apparatus 50 according to the second embodiment is anaerobic. Although it provided in the vicinity of the digestion processing tank 20, it does not specifically limit. You may install the miniaturization processing tank 18 in both.

  As an example, a wastewater treatment test was performed using the wastewater treatment apparatus 10 of the present invention shown in FIG.

  Further, as a comparative example, a wastewater treatment test was performed in the same manner as in the example using the wastewater treatment device 70 of FIG. In the wastewater treatment apparatus 70, a first sedimentation basin 72 for gravity sedimentation of organic sludge of large particles is installed upstream of the biological treatment tank 14, and the sludge collected from the first sedimentation basin 72 and the sedimentation tank 16 is anaerobic digestion treatment tank. Digest at 20.

  In addition, the wastewater to be used used the sewage of BOD 200mg / L and SS 200mg / L.

As a result, in the example, BOD in the waste water was removed in the coagulation sedimentation tank 12 by 60% removal rate and SS by 80% removal rate. On the other hand, in the comparative example, in the first sedimentation basin 72, only BOD was removed by 30% and SS was removed only by 50%. In the example, a methane gas amount of 0.56 Nm ³ / kg could be generated, but in the comparative example, only a methane gas amount of 0.31 Nm ³ / kg could be generated. The methane concentration of the generated methane gas was about 60% in both the examples and comparative examples.

  In the comparative example, the particulate organic sludge contained in the waste water in the first sedimentation basin 72 cannot be separated and recovered. For this reason, since biological treatment is performed in the biological treatment tank 14 with a high load of organic matter, the amount of excess sludge generated increases. Since the excess sludge is composed of microorganisms having a hardly decomposable cell membrane, it cannot be efficiently digested in the anaerobic digestion tank 20. Therefore, the amount of biogas generated in the anaerobic digestion tank 20 is reduced.

  On the other hand, in the embodiment, the particulate organic sludge present in the waste water in the coagulation sedimentation tank 12 can be separated and recovered by the coagulant, so that the amount of excess sludge generated in the biological treatment tank 14 is reduced. Can do. Since the organic sludge collected in the coagulation sedimentation tank 12 is more biodegradable than the excess sludge, the amount of methane gas generated in the anaerobic digestion treatment tank 20 can be increased.

  From this, in the waste water treatment method and apparatus of the present invention, it is possible to reduce the generation amount of excess sludge and to generate a large amount of methane gas (biogas) useful as energy.

The block diagram which showed the structure of the waste water treatment equipment which is the 1st Embodiment of this invention The block diagram which showed the structure of the waste water treatment equipment which is the 2nd Embodiment of this invention. Block diagram showing the configuration of a wastewater treatment apparatus as a comparative example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,50,70 ... Waste water treatment apparatus, 12 ... Coagulation sedimentation tank, 14 ... Biological treatment tank, 16 ... Precipitation tank, 18 ... Refinement treatment tank, 20 ... Anaerobic digestion treatment tank, 22 ... Inflow pipe, 24 ... Aggregation Agent feeding machine, 26 ... drainage transfer pipe, 28 ... organic sludge extraction pipe, 30 ... aeration device, 32 ... treated water transfer pipe, 34 ... outflow pipe, 36 ... sludge extraction pipe, 38 ... sludge return pipe, 40 ... fine Sludge transfer pipe, 42 ... Biogas recovery pipe, 44 ... Sludge discharge pipe, 72 ... First sedimentation basin

Claims (8)

In the wastewater treatment method for anaerobically digesting part or all of the excess sludge generated in the biological treatment while aerobically treating organic wastewater,
Upstream of the biological treatment, separating organic sludge from the organic waste water,
A wastewater treatment method characterized by subjecting the separated organic sludge to the anaerobic digestion treatment.   The wastewater treatment method according to claim 1, wherein the organic sludge is separated by adding a flocculant to the organic wastewater.   The waste water treatment method according to claim 2, wherein the flocculant has biodegradability.   The separated organic sludge is subjected to the anaerobic digestion treatment after performing a physicochemical or mechanical refinement treatment, and then the anaerobic digestion treatment. Wastewater treatment method.   The wastewater treatment method according to any one of claims 1 to 3, wherein a part of the sludge is extracted from the anaerobic digestion treatment, refined, and then anaerobically digested again. In a wastewater treatment apparatus that aerobically biotreats organic wastewater in a biological treatment tank and anaerobically digests some or all of the excess sludge generated in the biological treatment tank by anaerobic digestion treatment means,
Upstream of the biological treatment tank, solid-liquid separation means for separating organic sludge from the organic waste water, and refinement treatment means for subjecting the organic sludge to physicochemical or mechanical refinement,
A mud feed path for transferring organic sludge refined by the refinement treatment means to the anaerobic digestion means;
A wastewater treatment apparatus comprising: In a wastewater treatment apparatus that aerobically biotreats organic wastewater in a biological treatment tank and anaerobically digests some or all of the excess sludge generated in the biological treatment tank by anaerobic digestion treatment means,
Upstream of the biological treatment tank, solid-liquid separation means for separating organic sludge from the organic waste water, and a transfer path for transferring the organic sludge separated by the solid-liquid separation means to the anaerobic digestion treatment means, ,
Extracting part of the organic sludge and excess sludge from the anaerobic digestion processing means, physicochemical or mechanical refinement treatment means,
A return path for returning the organic sludge and excess sludge refined by the refinement treatment means to the anaerobic digestion treatment means;
A wastewater treatment apparatus comprising:   The wastewater treatment apparatus according to claim 6 or 7, wherein the solid-liquid separation means includes a flocculant charging machine for adding a biodegradable flocculant to the organic wastewater.

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