JP2008188503A - Wastewater treatment apparatus and wastewater treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the wastewater treatment apparatus and method capable of forming a habitat region of an animalcule contributing to the predation of microbial sludge to reduce excessive sludge without a separate carrier to efficiently reduce the excessive sludge. <P>SOLUTION: The wastewater treatment apparatus 10 is equipped with: an aeration tank 2 for housing microbial sludge to biologically treat organic wastewater; a final sedimentation basin 3 for receiving the supply of the aerated liquid, which is discharged from the aeration tank 2, and separating and recovering separated sludge containing the microbial sludge from the aerated liquid; and a sludge volume-reducing tank 4 to which at least a part of a biologically treated liquid and/or separated sludge is supplied as a liquid to be treated. The sludge volume reducing tank 4 is constituted so that the microbial sludge contained in the liquid to be treated is gathered to form particulate granules, the granules to be preyed formed by adding animalcule for preying upon the microbial sludge are added to granules are housed and the volume of the microbial sludge is reduced by the predation of the animalcule. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wastewater treatment apparatus and a wastewater treatment method for treating organic wastewater.

  In sewage treatment facilities and the like, the activated sludge method is widely adopted as a method for treating organic wastewater. The activated sludge method is a method of biologically treating organic wastewater under aerobic conditions in an aeration tank containing aerobic microbial sludge (activated sludge). When organic wastewater is treated by this method, organic components (so-called BOD components) are decomposed by metabolism of microbial sludge. At this time, about 40 to 50% of the decomposed BOD component is used for the growth of bacteria such as bacteria. Therefore, a lot of excess sludge is generated due to the proliferation of the bacterial cells, and the treatment becomes a problem.

  As a method for reducing the volume of excess sludge, for example, there is a method in which the generated excess sludge is solubilized or refined by performing ozone treatment, alkali treatment or ultrasonic treatment, and then returned to the aeration tank for treatment. Are known. However, this method requires expensive chemicals and special crushing devices for solubilization or refinement of excess sludge.

  Therefore, a method for reducing the amount of surplus sludge generated using a food chain of microorganisms and micro-animals has been proposed. Specifically, it is a method in which micro-animals such as protozoa (for example, Paramecium, vertebrate beetle) and metazoans (for example, earthworm, rotifer) prey on microorganisms. According to this method, since the microbial sludge that has proliferated along with the decomposition treatment of the organic components in the wastewater is preyed and digested by the micro-animals, it is possible to reduce the amount of surplus sludge generated without using chemicals or the like. There is.

In the method using a food chain, a liquid to be treated containing microbial sludge is supplied into a treatment tank inhabited by minute animals. In the treatment tank, generally, a floating carrier or a fixed carrier that holds a microanimal as a predator and forms a habitat for the microanimal is accommodated. For example, Patent Document 1 describes a treatment tank in which a spherical or pellet-shaped carrier is filled.
JP 08-39092 A

  However, when a treatment tank filled with a carrier as in Patent Document 1 is used, the inside of the carrier becomes deficient and microorganisms and micro animals are prone to anaerobic rot. Oxygen deficiency reduces the efficiency with which microanimals prey on microbial sludge. In addition, when a carrier having a complicated shape with high attachment efficiency of micro animals is used, there is a problem that the cost of the carrier becomes high.

  The present invention has been made in view of such circumstances, and it is possible to form a habitat for minute animals that contribute to the reduction of excess sludge by feeding on microbial sludge without using a separate carrier. An object of the present invention is to provide a wastewater treatment apparatus and a wastewater treatment method capable of efficiently reducing the amount of wastewater.

  The wastewater treatment apparatus of the present invention is supplied with a biological treatment tank containing microbial sludge and biologically treating organic wastewater, and at least a part of the biological treatment liquid discharged from the biological treatment tank. A solid-liquid separation tank that separates and collects separated sludge containing microbial sludge from the liquid, and a part of the biological treatment liquid from the biological treatment tank and / or at least a part of the separated sludge from the solid-liquid separation tank is supplied as the liquid to be treated. Sludge reduction that contains the microbial sludge contained in the liquid to be treated and produces granulated granules, and that contains the prey granules that the micro animals that prey on the microbial sludge adhere to the granules. And a container. Here, the microanimal refers to protozoa such as Paramecium and worm, and / or metazoans such as worms and rotifers.

  Microanimals that prey on microbial sludge have the property that if microbial sludge is attached to the surface of the carrier, it will also adhere to the surface and inhabit. Therefore, conventionally, a method has been used in which various carriers are arranged in a treatment tank for reducing excess sludge and a micro-animal habitat is formed therein.

  On the other hand, in the sludge volume reducing tank of the waste water treatment apparatus of the present invention, various animals are attached to the granular granules produced by the collection of microbial sludge without using various carriers. Since the granules themselves are aggregates of microbial sludge, the micro animals adhere to the surface and inside of the granules due to the above-mentioned properties of the micro animals. The attached micro-animals inhabit by preying on the microbial sludge that constitutes the granules. That is, the granule in the sludge volume reducing tank plays a role as a carrier for a micro animal and a role as a food for the micro animal. Thus, the amount of surplus sludge generated can be sufficiently reduced without using chemicals or the like by precipitating granules (prey granules).

  In addition, according to the wastewater treatment apparatus of the present invention, since there is no oxygen deficiency inside the carrier that may occur when the carrier is filled as in the prior art, the efficiency of microanimals foraging and digesting microbial sludge is reduced. Can be avoided. This is because the granule is a granular material having a particle size of several millimeters, and oxygen sufficiently reaches the inside. In addition, oxygen consumption increases when a micro animal or the like grows, but the granule itself is preyed and digested and disappears as the micro animal grows.

  Moreover, in the waste water treatment apparatus of this invention, it is preferable to provide the nutrient source supply means which supplies a nutrient source to a sludge volume reduction tank and activates the microorganism sludge in the said tank. This is because when the nutrient source is supplied to the microbial sludge in the sludge volume reduction tank, granulation is promoted. This is thought to be because microbial sludge secretes a large amount of mucus substances necessary for granulation when it becomes active in a nutrient-rich environment.

  The nutrient source supply means preferably includes a branch line branched from a supply line for supplying organic wastewater to the biological treatment tank. It is preferable to add the organic waste water before the biological treatment is applied to the sludge volume reducing tank through such a branch line. Organic wastewater used for biological treatment contains a large amount of BOD component, and this component is a nutrient source for microbial sludge.

  The biological treatment liquid and the separated sludge that can be supplied to the sludge volume reduction tank as the liquid to be treated are those that have undergone biological treatment in the biological treatment tank. That is, the BOD component is decomposed by the microbial sludge, and its content is sufficiently reduced. When organic waste water containing a large amount of BOD components, which are nutrient sources for microbial sludge, is added to such a liquid to be treated, the microbial sludge is activated and granules can be efficiently generated.

  The wastewater treatment method according to the present invention includes a biological treatment process for biologically treating organic wastewater with microbial sludge, and a solid-liquid separation that at least part of a biological treatment liquid obtained by biological treatment is separated into a separated liquid and separated sludge. Granule which produces | generates a granule by processing so that the separation process and a part of biological treatment liquid and / or at least one part of separation sludge may be processed liquid, and the microbial sludge contained in the said processed liquid may become granular It is characterized by comprising a generation step and a predation treatment step in which the granules are preyed on by the minute animals attached to the granules.

  In the wastewater treatment method of the present invention, various carriers are not used, and micro-animals are attached to the granulated granule aggregated with microbial sludge. The attached micro-animals inhabit by preying on the microbial sludge that constitutes the granules. In other words, the granule plays a role as a carrier for a micro animal and a role as a feed for the micro animal. By causing the micro animals to prey on the microbial sludge constituting the granules, the amount of excess sludge generated can be sufficiently reduced without using chemicals or the like.

  In addition, according to the wastewater treatment method of the present invention, since there is no oxygen deficiency inside the carrier that can occur when the carrier is filled as in the prior art, the efficiency of micro-animal predation and digestion of microbial sludge is reduced. Can be avoided.

  According to the present invention, it is possible to form a micro-animal habitat that contributes to the reduction of excess sludge by precipitating microbial sludge without using a separate carrier, and can efficiently reduce excess sludge and waste water treatment equipment. A processing method can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are used for the same elements, and duplicate descriptions are omitted.

<Effluent treatment device>
FIG. 1 is a schematic configuration diagram showing a preferred embodiment of a wastewater treatment apparatus according to the present invention. A wastewater treatment apparatus 10 shown in FIG. 1 is an apparatus for treating organic wastewater with aerobic microbial sludge.

  The wastewater treatment apparatus 10 includes a first sedimentation tank 1, an aeration tank (biological treatment tank) 2, a final sedimentation tank (solid-liquid separation tank) 3, and a sludge volume reduction tank 4.

  The first settling basin 1 is a pretreatment means for precipitating and separating solid matter having a relatively large particle size, which is contained in the organic wastewater introduced through the line L1. Of the solids contained in the organic wastewater that first flows into the settling basin 1, the precipitated ones are extracted from the line L <b> 2. The “line” means a pipeline.

  The organic waste water first subjected to the precipitation separation process in the settling tank 1 is introduced into the aeration tank 2 through the line L3. As shown in FIG. 1, the line L3 branches in the middle, and the leading end side of the branched branch line (nutrient source supply means) L3a is connected to a sludge volume reducing tank 4 described later. Through this branch line L3a, organic wastewater rich in nutrients for microbial sludge can be supplied to the sludge volume reducing tank 4. A valve is disposed in the middle of the branch line L3a.

  The aeration tank 2 is a biological treatment tank for biologically treating organic wastewater with aerobic microbial sludge. The aeration tank 2 is provided with an aeration device for aerating air. In the aeration tank 2, microbial sludge whose dominant species is aerobic bacteria exists and is stored in a floating state. The microbial sludge in the aeration tank 2 grows by consuming oxygen supplied by the aeration apparatus while using the BOD component in the organic wastewater as a nutrient source. As a result, organic wastewater is biologically treated, and sludge (excess sludge) is generated mainly by the growth of aerobic bacteria.

  The biota of the microbial sludge in the aeration tank 2 is mainly composed of bacteria as described above. The main reason why bacteria become the dominant species in microbial sludge is that the growth rate of bacteria is higher than the growth rate of protozoa in the state where the concentration of the BOD component is high. Further, in an environment where bacteria are dominant species, a large amount of excreta is discharged from the bacteria. In such an environment, since the growth of protozoa and the like is inhibited, the dominance of bacteria is further promoted.

  The aeration tank 2 is a cross-flow type aeration tank whose interior is divided into a plurality of regions by partition walls, and the introduced organic waste water sequentially passes through each region. By setting it as such a structure, the aeration conditions suitable for the organic waste_water | drain in each area | region etc. can be set, for example. The organic wastewater supplied to the upstream region of the aeration tank 2 is sufficiently biologically processed until reaching the downstream region to which the line L4 is connected. Aeration liquid (biological treatment liquid) is introduced into the final sedimentation tank 3 through the line L4.

  A line L5 is connected to the bottom of the downstream area of the aeration tank 2. A part of the aeration liquid in the aeration tank 2 can be discharged by opening a valve disposed in the middle of the line L5. The discharged aerated liquid is supplied to a sludge volume reducing tank 4 described later through a line L5.

  The final sedimentation basin 3 is a solid / liquid separation means for separating the aerated liquid from the aerated tank 2 into separated sludge and separated liquid. The separation liquid is a so-called supernatant liquid, and the content of microbial sludge is sufficiently reduced. On the other hand, the separated sludge is mainly microbial sludge that has flocated and settled, and contains microbial sludge in a high concentration. The separated sludge also contains solids that have not been decomposed by the biological treatment in the aeration tank 2.

  A line L6 and a line L7 are connected to the final sedimentation tank 3. The line L6 is a line for transferring the separated liquid to equipment for sterilization. On the other hand, the line L7 is a line for extracting the separated sludge from the final sedimentation tank 3. Most of the extracted separated sludge is returned to the upstream region of the aeration tank 2 through the line L8 as return sludge. The separated sludge that is not returned in the line L8 is discharged out of the system through the line L9. The sludge discharged out of the system through the line L9 is called surplus sludge.

  The sludge volume reducing tank 4 is a tank for generating granules by processing (granulating) so that microbial sludge becomes granular. In addition to this, the sludge volume reducing tank 4 also plays a role of reducing the volume of microbial sludge by precipitating the granules to the micro animals adhering to the generated granules. The sludge volume reduction tank 4 is an airlift type semi-batch reactor (SBR), and gradually forms granules from microbial sludge by repeatedly performing a predetermined basic period. In the description of the sludge volume reducing tank 4 below, the activated sludge including microbial sludge and granules is also referred to.

  2-5 is a figure which shows the state in each operation of the granule production | generation process of the sludge volume reduction tank 4, respectively. As shown in FIGS. 2-5, the sludge volume reduction tank 4 is equipped with the cylindrical tank 41 for accommodating a liquid.

  A line L <b> 10 for discharging the treated water W that has been treated in the tank 41 is connected to the side wall of the tank 41. This line L10 is connected to a position higher than the deposited layer made of activated sludge G that has settled in the stationary step S3 (see FIG. 6) described later. On the other hand, a line L11 for pulling out the settled solid matter and sludge is connected to the bottom of the tank 41. The leading ends of the line L10 and the line L11 are both connected to the line L4. A valve is provided in each of the lines L10 and L11.

  Further, an inner cylinder 42 is disposed in the tank 41, and an aeration bulb 43 is provided at the lower portion of the inner cylinder 42 as an aeration means for aeration of the inside of the tank 41. A blower 45 is connected to the air diffuser 43, and air from the blower 45 is blown into the air diffuser 43 to be diffused into the tank 41.

<Wastewater treatment method>
Next, a method for treating organic wastewater by the wastewater treatment apparatus 10 according to the present embodiment will be described. The wastewater treatment method in this embodiment includes a decomposition and removal treatment for decomposing and removing organic components contained in organic wastewater, and a sludge volume reduction treatment for reducing the volume of microbial sludge that has proliferated with the decomposition of the organic components. Is what you do.

  The organic component decomposition and removal treatment is performed in the first settling tank 1, the aeration tank 2, and the final settling tank 3 described above. Specifically, first, pretreatment is first performed in the settling basin 1, and then organic wastewater is supplied to the aeration tank 2 through the line L3. Organic waste water is aerated in the aeration tank 2, and the organic components are decomposed by the metabolic function of the microbial sludge accommodated in the aeration tank 2 (biological treatment process).

  The aeration liquid is introduced from the aeration tank 2 into the final sedimentation basin 3 through the line L4, and the aeration liquid is separated into the separated liquid and the separated sludge in the final sedimentation basin 3 (solid-liquid separation process). After sterilizing the separation liquid discharged from the final sedimentation tank 3 through the line L6, the separation liquid is discharged into a river or the like.

  On the other hand, sludge volume reduction processing for reducing the volume of microbial sludge is performed in the sludge volume reduction tank 4. Sludge volume reduction treatment is a process of generating granules from microbial sludge contained in the liquid to be treated (granule generation process), and a process in which granules are predated by micro animals adhering to the generated granules ( Predation processing step). Hereinafter, the sludge volume reduction process in the sludge volume reduction tank 4 is demonstrated.

(Granule production process)
As shown in FIG. 6, the granulation of microbial sludge is performed by a semi-batch process that repeats the basic period composed of the injection step S1, the air diffusion step S2, the stationary step S3, and the discharge step S4. Hereinafter, each step will be described.

  In the injection step S1, as shown in FIG. 2, a liquid to be treated containing microbial sludge is introduced into the tank 41. FIG. 2 shows a state in which treated water and organic waste water are again injected from each line (line L5, line L8a, branch line L3a) after performing a basic cycle (described later) of the granule generation process at least once. Show. The hatching of the activated sludge G indicates a state where the microbial sludge G1 and the granulated granule G2 are precipitated and deposited.

  In order to generate granules which are aggregates of microbial sludge, it is necessary to introduce a liquid to be treated containing microbial sludge into the tank 41. Here, the aeration liquid supplied through the line L5 and the return sludge supplied through the line L8a branched from the line L8 are used as the liquid to be treated. The valves disposed in the middle of the line L5 and the branch line L3a are opened, and both fluids are introduced into the tank 41.

  In addition, the to-be-processed liquid in the sludge volume reduction tank 4 may be any one of an aeration liquid and return sludge, and these liquid mixture may be sufficient as it. However, it is preferable that the liquid to be treated is prepared by appropriately mixing a return sludge having a high concentration of microbial sludge and an aeration liquid having a low concentration so as to obtain a concentration suitable for granulation.

  On the other hand, organic wastewater is introduced into the tank 41 through the branch line L3a. This is because the nutrient contained in the organic waste water activates the microbial sludge in the liquid to be treated to promote granulation. The amount of the organic waste water added to the liquid to be treated is preferably 1 to 3 parts by volume of the organic waste water with respect to 1 part by volume of the liquid to be treated. When the added amount of the organic waste water is less than 1 part by volume, the microbial sludge is not sufficiently activated, and the progress rate of granulation tends to be low. On the other hand, when the added amount of the organic waste water exceeds 3 parts by volume, the nutrient source becomes excessive, the bacteria grow in the tank 41, and the growth of micro animals that prey on these tends to be inhibited.

  In the subsequent aeration step S2, as shown in FIG. 3, the blower 45 is driven and blown to the aeration bulb 43, and the aeration of the aeration from the aeration bulb 43 causes the liquid in the tank 41 to be aerated. From the viewpoint of efficiently generating the granule G2, it is preferable to adjust the amount of air diffusion so that the circulation flow rate in the tank 41 is about 0.5 to 10 m / min. The microbial sludge G1 gathers in the process of flowing at a circulation flow rate in the above range to form small granules and grows gradually.

  In the stationary step S3 after the air diffusing step S2, as shown in FIG. 4, the blower 45 is stopped to stop the aeration and to stand still. As a result, the solid matter (activated sludge G) floating in the liquid in the tank 41 settles, and the activated sludge G accumulates at the bottom of the tank 41. Subsequently, in the discharge step S4, as shown in FIG. 5, the treated water W, which is a supernatant, is discharged from the line L10.

  The basic cycle consisting of the injection step S1, the air diffusion step S2, the stationary step S3, and the discharge step S4 is repeated. By repeating the basic period, when aeration is performed in the aeration step S2, the microbial sludge G1 is self-granulated to generate granules G2 having a large particle size. The particle size of the granules G2 to be produced varies depending on the processing conditions, but is usually about 0.5 mm to several mm.

  Of the injection step S1, the diffusion step S2, the stationary step S3, and the discharge step S4, the time required for the injection step S1 and the discharge step S4 depends on the scale of the apparatus (the internal volume of the tank 41, etc.). On the other hand, the time required for the air diffusion process S2 and the stationary process S3 is less dependent on the scale of the apparatus. For example, the aeration time in the air diffusion step S2 may be about several hours to about 24 hours, and the standing time in the standing step S3 may be about several tens of minutes to several hours.

  In the granule production process that repeats the above basic period, the organic waste water is supplied through the branch line L3a in the injection process S1. Therefore, the nutrient source (organic matter) contained in the organic waste water is given to the microbial sludge G1 in a pulsed manner. Therefore, for the microbial sludge G1, a state in which nutrition is abundant (satiated state) and a state in which nutrition is insufficient (starvation state) are repeated. As described above, when the stagnation state is reached after the starvation state, the microbial sludge G1 ingests more nutrients, so that an extracellular polymer is easily formed, and the microbial sludge G1 is easily self-granulated.

(Predation process)
When the granule G2 is formed in the tank 41 as described above, micro-animals contained in the aeration liquid and the return sludge adhere to the granule G2. The attached micro-animal grows on the surface and inside of the granule G2, and prey and digest the granule G2, which is an aggregate of the microbial sludge G1, (predation process). In particular, since the predation activity of the micro-animal becomes active in the presence of oxygen, the granule G2 is preyed mainly in the aeration process S2.

  As described above, in the sludge volume reducing tank 4, granulation of microbial sludge and predation treatment of granules (precipitated granules) proceed simultaneously. To stably reduce the volume of microbial sludge G1 by balancing the amount of granule G2 generated and the amount of predation by micro-animals so that the particle size of granule G2 is maintained above a predetermined value. Can do.

  Usually, when microbial sludge is preyed on by a micro animal, 30 to 40% of the predated microbial sludge is converted into a micro animal. This means that 30 to 40 parts by volume of micro animals are produced from 100 parts by volume of the microbial sludge subjected to predation treatment. In other words, 60 to 70% of microbial sludge volume reduction can be achieved by precipitating granules in the sludge volume reducing tank 4.

  As mentioned above, although one Embodiment of this invention was described, it is not limited to the said embodiment of this invention, The following may be sufficient.

  In the said embodiment, although the sludge volume reduction tank provided with the inner cylinder 42 was illustrated, if a circulating flow can be generated in the tank 41 by an air lift effect | action, it will not be limited to this. For example, a partition plate or the like may be provided in the tank 41 instead of the inner cylinder 42 to provide a circulation flow path. Further, the inner cylinder 42, the partition plate and the like may not be provided in the tank 41.

  Further, the nutrient source supply means for the microbial sludge in the tank 41 is not limited to the line L3a for adding organic wastewater, and for example, a liquid or powdered nutrient containing a nutrient source such as organic matter or nitrogen source is added. You may attach the means to do to the sludge volume reduction tank 4. FIG.

Further, as the aeration tank 2, a cross-flow type in which the inside of the tank is divided into a plurality of regions by partition walls is illustrated, but a completely mixed type aeration tank may be adopted. Moreover, you may employ | adopt the biological treatment tank which equips with an anaerobic tank, an oxygen-free tank, an aerobic tank etc. instead of the aeration tank 2. FIG. Such a biological treatment tank is used for the activated sludge method called A ₂ O method, and can also perform denitrification treatment and dephosphorization treatment.

  Moreover, you may implement the process of organic waste_water | drain as follows. For example, in the above-described embodiment, the case where the particle size of the granule G2 is processed so as to be maintained at a predetermined value or more is illustrated. However, after the granule G2 is generated, the aeration is continued from the aeration balloon 43 for a long time. You may do it. Thereby, you may make a micro animal prey until the granule G2 turns into fine sludge.

  If the granule G2 is preyed until it becomes fine sludge, the minute animal can not adhere to it and floats in the treatment liquid water W. Then, the treatment liquid containing a large amount of minute animals is discharged from the line L10. In such a case, it is preferable to transfer the treatment liquid water W to an anaerobic digester and treat it under anaerobic conditions. Small animals die more easily under anaerobic conditions than bacteria, and are solubilized and converted into organic acids and the like by acid-producing bacteria. By carrying out such solubilization of micro animals and organic acid fermentation treatment, it is possible to further reduce the volume of excess sludge. What is necessary is just to transfer the process liquid which passed through the process in an anaerobic digester through the line to the aeration tank 2, for example. In addition, what is necessary is just to implement a granule production | generation process again in the sludge volume reduction tank 4, when reducing volume of microbial sludge continuously after that.

  The means for treating the micro animals from the sludge volume reducing tank 4 is not limited to the anaerobic digestion tank as described above, and a micro animal crushing apparatus may be used instead of the anaerobic digestion tank. Examples of the minute animal crusher include a pump with a cutter, a high speed mixer, a food waste disposer, and a high-pressure nozzle injection device.

  Furthermore, in each injection process S1 of the basic cycle to be repeated, only the liquid to be treated may be introduced or only the organic waste water may be introduced according to the physical properties of the liquid in the tank 41.

It is a schematic structure figure showing a suitable embodiment of a waste water treatment equipment concerning the present invention. It is a figure which shows the state in the injection | pouring process of a sludge volume reduction tank. It is a figure which shows the state in the air diffusion process of a sludge volume reduction tank. It is a figure which shows the state in the stationary process of a sludge volume reduction tank. It is a figure which shows the state in the discharge process of a sludge volume reduction tank. It is a flowchart which shows the basic period of a granule production | generation process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Waste water treatment apparatus, 1 ... First sedimentation tank, 2 ... Aeration tank (biological treatment tank), 3 ... Final sedimentation tank (solid-liquid separation apparatus), 4 ... Sludge volume reduction tank, 41 ... Tank, 42 ... Inner cylinder 43 ... Aeration balloons, 45 ... Blower, G ... Activated sludge, G1 ... Microbial sludge, G2 ... Granule, L3 ... Line (supply line), L3a ... Branch line (nutrient source supply means).

Claims (4)

In wastewater treatment equipment for treating organic wastewater,
A biological treatment tank containing microbial sludge and biologically treating the organic waste water;
A solid-liquid separation tank in which at least a part of the biological treatment liquid discharged from the biological treatment tank is supplied, and the separated sludge containing the microbial sludge is separated and recovered from the biological treatment liquid;
A part of the biological treatment liquid from the biological treatment tank and / or at least a part of the separated sludge from the solid-liquid separation tank is supplied as a liquid to be treated, and the microbial sludge contained in the liquid to be treated is assembled. And a granulated granule, and a sludge volume reducing tank that accommodates the prey granule formed by adhering to the granule microanimals that prey on the microbial sludge,
A wastewater treatment apparatus comprising:   The wastewater treatment apparatus according to claim 1, further comprising a nutrient source supply means for supplying a nutrient source to the sludge volume reducing tank and activating the microbial sludge in the tank.   The nutrient source supply means includes a branch line branched from a supply line for supplying the organic wastewater to the biological treatment tank, and the organic wastewater before the biological treatment is applied as the nutrient source The wastewater treatment apparatus according to claim 2, wherein the wastewater treatment apparatus is supplied into a sludge volume reduction tank. In the wastewater treatment method for treating organic wastewater,
A biological treatment process for biologically treating the organic wastewater with microbial sludge;
A solid-liquid separation step in which at least a part of the biological treatment liquid obtained by the biological treatment is separated into a separated liquid and separated sludge;
Granule generation in which a part of the biological treatment liquid and / or at least a part of the separated sludge is treated liquid, and the microbial sludge contained in the treated liquid is processed to be granular to generate granules. Process,
A predation process in which the granules are preyed on by the micro animals adhering to the granules;
A wastewater treatment method comprising:

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