JP6986776B2 - Difficult-to-purify liquid treatment system - Google Patents

Description

The present invention relates to a difficult-to-purify liquid treatment system for purifying digestive juices such as bioplants.

In recent years, biogas power plants using organic waste such as cattle manure and swill have been attracting attention. Organic waste is placed in a fermenter and fermented with methane to produce biogas containing methane and carbon dioxide to obtain fuel for a gas engine generator.

The residue after generating biogas is called digestive juice, and since it contains nitrogen, phosphorus, and potassium, it can be used as fertilizer. Digestive juice that is not used as fertilizer needs to be discharged to rivers. At this time, SS (suspended solids), phosphorus, nitrogen, ammonia, etc. in the digestive juice will bring about eutrophication of rivers and lakes and pollution of soil and groundwater. Therefore, an apparatus has been proposed for treating digestive juice, separating SS and phosphorus, and decomposing nitrogen and ammonia.

Patent Document 1 discloses a system in which a digestive juice is electrolyzed by an electrolysis layer to separate a solid and a liquid, and nitrogen, phosphorus and the like are removed.

JP-A-2004-154762

However, in the system according to Patent Document 1, in order to prolong the time for electrolyzing the digestive juice and increase the removing ability, it is necessary to increase the size of the electrode, which causes a problem that the system becomes large. Such a problem applies not only to digestive juices but also to difficult-to-purify liquids having a high BOD or COD (for example, 1000 or more) that are difficult to purify by microorganisms.

An object of the present invention is to solve the above-mentioned problems and to provide a difficult-to-purify liquid purification system having a high processing capacity while preventing an increase in the size of the apparatus.

Some of the independently applicable features of the invention are listed below.

(1) The difficult-to-purify liquid treatment device according to the present invention is a device for treating the difficult-to-purify liquid, and is provided in a flow path for flowing the difficult-to-purify liquid and the flow path, and the difficult-to-purify liquid is provided. A pair of electrodes arranged in the flow direction of the above and a power source for supplying power to the electrodes are provided, and the electrodes are configured to have an uneven shape with respect to the flow of the difficult-to-purify liquid. The digestive juice is configured to meander and flow between the pair of electrodes.

Therefore, the performance of electrolysis can be improved without increasing the size of the device.

(2) The difficult-to-purify liquid treatment device according to the present invention is a device for treating the difficult-to-purify liquid, and is provided in a flow path for flowing the difficult-to-purify liquid and the flow path, and the difficult-to-purify liquid is provided. A pair of electrodes arranged in the flow direction of the above and a power source for supplying electric power to the electrodes are provided, and the electrodes are configured in a mesh pattern.

Therefore, the performance of electrolysis can be improved without increasing the size of the device.

(3) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that a plurality of positive electrodes and negative electrodes are alternately arranged.

Therefore, both sides of each electrode can be used as a flow path for electrolysis, and the performance of electrolysis can be improved without increasing the size of the device.

(4) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that a scooping means for scooping up the solid remaining after being electrolyzed by the electrode is provided downstream of the electrode.

Therefore, the separated solid can be removed.

(5) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that the bottom of the flow path is lowered toward the downstream.

Therefore, the difficult-to-purify liquid can flow naturally toward the downstream.

(6) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that the anode of the electrodes is composed of magnesium.

Therefore, SS can be efficiently decomposed.

(7) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that an electrolyte is added to the difficult-to-purify liquid before passing through the electrode.

Therefore, the performance of electrolysis can be improved.

(8) The difficult-to-purify liquid treatment apparatus according to the present invention is further provided with a trapping means for capturing hydrogen generated from the cathode of the electrodes.

Therefore, hydrogen generated by electrolysis can be collected and used.

(9) The difficult-to-purify liquid treatment apparatus according to the present invention is further provided with a capturing means for capturing oxygen generated from the anode of the electrodes.

Therefore, oxygen generated by electrolysis can be collected and used.

(10) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that oxygen is used for aeration treatment of the difficult-to-purify liquid.

Therefore, oxygen generated by electrolysis can be used for aeration.

(11) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that the difficult-to-purify liquid has a BOD or COD of more than 1000.

Therefore, it is possible to treat substances having a BOD or COD of more than 1000 and which are difficult to purify by microorganisms or the like.

(12) The difficult-to-purify liquid treatment apparatus according to the present invention is characterized in that the difficult-to-purify liquid is any one of digestive liquid of a biogas plant, manure from a slurry store, and wastewater from a milking facility.

Therefore, it is possible to treat digestive juices of biogas plants, manure from slurry stores, and wastewater from milking facilities, which are difficult to purify by microorganisms.

It is a configuration of a digestive juice purification system according to an embodiment of the present invention. 2A is a plan view of the electrolytic cell 4, and FIG. 2B is a cross-sectional view of the electrolytic cell 4. 3A, 3B, and 3C are plan views of the positive electrode 6a and the negative electrode 6b. FIG. 4 is an experimental result showing a change in the SS removal rate when the combination of the materials of the positive electrode 6a and the negative electrode 6b is changed. FIG. 5 is a side sectional view for showing the configuration of the conveyor 8. FIG. 6 is a plan view of the conveyor 8. FIG. 7 is a diagram showing the configuration of the filtration tank 10. 8A and 8B are diagrams showing the configuration of electrodes according to other embodiments. FIG. 9 is a diagram showing electrodes having a network structure (positive electrode 6a, negative electrode 6b) according to another embodiment. FIG. 10 is a cross-sectional view showing a structure for recovering oxygen and hydrogen generated during electrolysis. FIG. 11 is a vertical sectional view showing a structure for recovering oxygen and hydrogen generated during electrolysis. FIG. 12 is a diagram showing another scooping means.

1. 1. Basic Configuration and Operation FIG. 1 shows the overall configuration of a digestive juice purification system according to an embodiment of the present invention. Digestive juice from a biopower plant or the like is introduced into the flow rate adjusting tank 2. An electrolyte (for example, magnesium chloride) is introduced into the flow rate adjusting tank 2 together with the digested liquid. In this embodiment, the electrolyte is added so as to have a concentration of 0.5% by weight.

The flow rate adjusting tank 2 is for keeping the flow rate flowing out to the electrolytic cell 4, which is a digestive liquid treatment device, constant even if the amount of digestive liquid received is changed. The digestive juice guided to the electrolytic cell 4 is electrolyzed through the space between the electrodes 6, SS is removed, and solid-liquid separation is performed. At the same time, phosphorus is separated and nitrogen and ammonia are decomposed.

The floating solid (SS) is scooped up by the conveyor 8 and guided to the disposal tank 14. The digestive juice from which SS has been removed is exposed to oxygen in the aeration tank 12 and purified. The purified digestive juice passes through the filtration tank 10 and is discharged into a river or the like as drainage.

FIG. 2 shows the details of the electrolytic cell 4. 2A is a plan view and FIG. 2B is a side sectional view. The housing 42 is made of stainless steel. As shown in FIG. 2A, the width of the housing 42 narrows from the upstream portion (about 3 m to 5 m in this embodiment) toward the downstream portion (about 1 m in this embodiment).

As shown in FIG. 2B, stainless steel bottom plates 44 and 46 inclined from upstream to downstream are provided inside the housing 42. In this embodiment, the inclination angle of the bottom plate 44 is about 45 degrees, and the inclination angle of the bottom plate 46 is 3 to 5%.

A plurality of positive electrodes 6a and a plurality of negative electrodes 6b are alternately provided on the bottom plate 46, and a plurality of flow paths are formed. A DC voltage (30 V in this embodiment) is applied between the positive electrode 6a and the negative electrode 6b. As a result, the digestive juice flowing through the flow path formed by the positive electrode 6a and the negative electrode 6b is electrolyzed.

In this embodiment, an aluminum material was used for the positive electrode 6a, and iron was used for the negative electrode 6b. Aluminum material or copper may be used for the negative electrode 6b. FIG. 4 shows the experimental data of the SS removal rate when some materials are used for the positive electrode 6a and the negative electrode 6b.

In the experiment, sodium chloride or magnesium chloride was added as an electrolyte in a 10-fold diluted bioplant fire extinguishing solution (500 ml) in a predetermined weight% (for example, 0.1% by weight to 20% by weight), and the electrode rods of the anode were made of aluminum and magnesium. The electrode rod of the cathode was either magnesium, iron, aluminum, or copper. A DC voltage was applied for 10 minutes or 20 minutes, and the SS removal rate and COD removal rate were confirmed.

As long as the content of the electrolyte does not pose a problem as wastewater, the larger the content of the electrolyte, the less power is required for electrolysis. Magnesium chloride is a preferable electrolyte because there are few problems even if it is contained in wastewater.

As is clear from FIG. 4, the removal rate of SS was high when magnesium was used as the anode or when the combination of aluminum-iron, aluminum-aluminum, and aluminum-copper was used. As the cathode, any material may be used as long as it is the same as the anode or has a lower ionization tendency than the anode.

Therefore, it is preferable to determine the electrode material by any combination of the above. In the above experiment, the digestive juice is diluted 50 times, but in the system of the embodiment, the digestive juice is treated without being diluted.

When magnesium is used for the anode, Mg (OH) ₂ is discharged by the following reaction.

Mg ＋ 2H ₂ O → Mg (OH) ₂ ＋ H ₂
On the other hand, when aluminum is used for the anode, 2Al (OH) ₃ is discharged by the following reaction.

2Al ＋ 6H ₂ O → 2Al (OH) ₃ ＋ 3H ₂
Mg (OH) ₂ is harmless to plants and animals, but 2Al (OH) ₃ is harmful and should be removed before drainage. By exchanging the anode and cathode and applying an electric potential to electrolyze, 2Al (OH) ₃ can be captured by the electrode and removed from the wastewater.

Returning to FIG. 2, when the digestive juice flows through the flow path formed by the positive electrode 6a and the negative electrode 6b, the digestive juice is electrolyzed. By this electrolysis, SS is removed, phosphorus is separated, and nitrogen and ammonia are decomposed. The longer the digestive juice stays in the flow path between the positive electrode 6a and the negative electrode 6b, the greater the degree of electrolysis.

In this embodiment, the positive electrode 6a and the negative electrode 6b are formed in an uneven shape as shown in FIG. 2A so that the digestive juice is in contact with the positive electrode 6a and the negative electrode 6b for a long time. The details of a part thereof are shown in FIG. 3C. The positive electrode 6a is configured in a zigzag shape with a straight side bent. Similarly, the adjacent negative electrode 6b is also configured in a zigzag shape with the straight side bent. Therefore, the digestive juice will meander and flow between the positive electrode 6a and the negative electrode 6b.

When the digestive juice is not diluted (or the degree of dilution is small), the degree of removal of SS etc. is smaller when the electrodes of the same length are used than when the degree of dilution is high (the fire extinguishing liquid is thin). Become. Therefore, when the digestive juice is not diluted (or the degree of dilution is small), it is necessary to lengthen the electrode or return the digestive juice after electrolysis and repeat the electrolysis treatment. There is a problem that the device becomes large when the electrode is lengthened, and there is a problem that the processing time becomes long when the electrolysis processing is repeated.

On the other hand, if the degree of dilution of the digestive juice is increased, the degree of removal of SS and the like by electrolysis increases. Therefore, it is not necessary to lengthen the electrodes, and the device can be miniaturized. However, since the degree of dilution of the digestive juice is high, the amount of the diluted digestive juice that must be processed increases, which means that the treatment time is required.

Therefore, it is preferable to select an appropriate degree of dilution of the digestive juice according to the miniaturization of the apparatus and the shortening of the processing time. Generally, it seems preferable to dilute 3 to 5 times. In some cases, the treatment may be performed without dilution, or may be diluted 5 times or more (for example, 10 times).

In FIG. 3C, only one positive electrode 6a and one negative electrode 6b are shown, but as shown in FIG. 2A, a plurality of positive electrodes 6a and negative electrodes 6b are alternately arranged. As a result, flow paths for performing electrolysis can be formed on both sides of each electrode to provide a plurality of flow paths, and electrolysis can be efficiently performed on the planar area of the electrode arrangement.

In addition, as shown in FIG. 3C, by arranging the positions of the unevenness of the adjacent electrodes so as to correspond to each other (by moving horizontally in the direction perpendicular to the electrode arrangement direction so that the shapes of the unevenness overlap). , A flow path having a constant distance D in the direction perpendicular to the electrode arrangement direction of the adjacent electrodes is formed. Since it has a zigzag shape, the vertical distance E between the electrodes is also constant, and the flow of the electrolytic solution is smooth. The distance between the electrodes is preferably constant (parallel), but it is practical even if it is not constant. For example, the structure may be such that the width between the electrodes gradually narrows from the upstream to the downstream.

Returning to FIG. 2, the electrolyzed digestive juice is guided to a conveyor 8 provided downstream of the electrolytic cell 4. Most of the SS in the digestive juice is removed by electrolysis, but the remaining SS will float on the surface of the digestive juice. The conveyor 8 scoops up this floating SS.

5 and 6 show details of the vicinity of the conveyor 8. FIG. 5 is a side sectional view, and FIG. 6 is a plan view. As shown in FIG. 5, the conveyor 8 is configured by winding a cloth belt 82 between the rotating shafts 84 and 86. As shown in FIG. 6, the width of the belt 82 is formed to be substantially equal to the width of the housing 42 of the electrolytic cell 4. The rotary shaft 84 is rotatably supported by a bearing (not shown) provided in the housing 42 so that the digestive juice in the housing does not leak out by a sealing material (not shown). The rotating shaft 84 is rotated by a motor (not shown) provided outside the housing 42.

The rotary shaft 86 is rotatably supported by a bearing (not shown) provided in the housing 42. Since the belt 82 is wound between the rotary shaft 84 and the rotary shaft 86, the upper belt 82 moves in the direction of the arrow A due to the rotation of the rotary shaft 84.

As shown in FIG. 5, the upstream side of the belt 82 is submerged in the digestive juice 5. Therefore, the SS that has flowed in is scooped up by the belt 82. Then, it is transferred in the direction of the arrow A, falls at the tip end portion (rotary shaft 86 side) of the conveyor 8, and is guided to the SS recovery passage 6. The SS recovery passage 9 is inclined so as to go down to the back side of the paper surface. As shown in FIG. 6, the SS that has fallen into the SS recovery passage 9 moves in the SS recovery passage 9 in the direction of arrow B and is guided to the disposal tank 14. Therefore, SS will be accumulated in the waste layer 14.

The material of the belt 82 is cloth. This makes it possible to permeate the digestive juice, which is a liquid, and scoop up SS7, which is a solid. In addition to cloth, a material (net, drainboard, porous member, etc.) that allows liquid to permeate and capture solid can be used.

Returning to FIG. 1, the digested liquid 5 from which SS7 has been removed by the conveyor 8 is sent to the aeration tank 12. In the aeration tank 12, oxygen is sent from the lower part of the digestive juice 5 by a blower (not shown) to supply oxygen to the digestive juice 5 to purify the digestive juice 5. The purified digestive liquid 5 is sent to the filtration tank 10.

FIG. 7 shows the configuration of the filtration tank 10. An aeration unit 92 for aeration is provided at the lowermost part. Oxygen is supplied to the aeration unit 92 from a blower (not shown) to aerate. A submersible membrane unit 90 is provided on the aeration unit 92.

The digestive liquid 5 introduced into the filtration tank 10 by the introduction pipe 98 is accumulated in the filtration tank 10. Suction is performed from the submersible membrane unit 90 by the suction pipe 96. As a result, the digestive liquid 5 filtered by the submersible membrane unit 90 is sucked from the suction pipe 96. The filtrate is discharged into rivers and the like.

As the filtration tank 10, an MBR immersion membrane unit (for example, manufactured by Awa Paper Co., Ltd.), a flat membrane, a reverse osmosis membrane, or the like can be used.

2. 2. Other embodiments
(1) In the above embodiment, as shown in FIG. 3, each electrode has an uneven shape, and when the electrodes are moved in a direction perpendicular to the electrode arrangement direction (upstream to downstream), the positions where the irregularities of the electrodes overlap. Each electrode is arranged in. Any irregular shape may be used, and for example, the shape (corrugated shape or the like) as shown in FIGS. 3A, 3B, and 3C can be used.

When the zigzag shape is formed as shown in FIG. 3C, the vertical distance E between the electrodes is constant in such an arrangement. However, if the electrode has a sharp portion as shown in FIGS. 3B and 3C, electrolysis may be concentrated and electrolysis may not be performed evenly. Therefore, it is preferable to have a shape such as 3A.

In the case of FIGS. 3A and 3B, the vertical distance E between the electrodes may not be constant, and the flow of digestive juice may not be smooth.

Therefore, instead of the structure of FIG. 3A, as shown in FIG. 8A, the vertical distance E between the electrodes can be made constant (or not changed so much) by making the arc portion concentric. However, in this case, as shown in FIG. 8A, the negative electrode 6b needs to have a double structure. The positive electrode 6a may have a double structure.

Further, instead of the structure of FIG. 3B, as shown in FIG. 8B, the vertical distance E between the electrodes can be made constant (or not changed so much) by changing the size of the unevenness. In this case as well, either the positive electrode 6a or the negative electrode 6b may have a double structure.

(2) In the above embodiment, sodium chloride water is added to the digestive juice to facilitate electrolysis. However, electrolysis may be performed without adding sodium chloride water.

(3) In the above embodiment, the electrode has an uneven structure. However, as shown in FIG. 9, a mesh structure (or a plate structure with holes) may be used. By making the mesh finer, the surface area of the electrode can be substantially increased and the electrolysis capacity can be increased. Both the positive electrode 6a and the negative electrode 6b may have a mesh structure, or only one of them may have a mesh structure and the other may have a plate shape.

Further, a flat mesh structure may be used, but an uneven shape as shown in FIGS. 3 and 8 may be used.

(4) During electrolysis by the electrolytic layer 6, oxygen is generated from the positive electrode 6a and hydrogen is generated from the negative electrode 6b. Therefore, as shown in FIG. 10, hoods 52 and 56 may be provided on each electrode to collect oxygen and hydrogen. The side sectional view of the hood 52 is as shown in FIG. The hood 56 has the same configuration.

The oxygen collected by the hood 52 is collected and transferred to the collection pipe 54. Similarly, the hydrogen collected by the hood 56 is collected and transferred to the collection pipe 58.

The hydrogen thus obtained can be used, for example, to drive a hydrogen gas engine to generate electricity. The obtained electricity can be used as electric power for the electrolytic cell 6. It can also be used as fuel for hydrogen engines. The obtained oxygen can be the oxygen used in the aeration tank 12.

In the above, both oxygen and hydrogen are recovered, but only one of them may be recovered.

(5) In the above embodiment, the conveyor 8 is used as the scooping means. However, the configuration as shown in FIG. 12 may be used. A rectangular frame 17 is provided, and a cloth 19 (or a net or the like) is stretched in the frame 17. Support rods 15 that move up and down by hydraulic cylinders (not shown) are connected to the four corners of the rectangular frame 17 via universal joints. Therefore, the frame 17 can be moved up and down by controlling the hydraulic cylinder (arrows E and F).

At predetermined time intervals, the frame 17 is moved in the direction of the arrow E and rises to the position indicated by the broken line. At this time, the SS7 can be scooped up by the cloth 19. Further, it is possible to control the vertical movement of the four hydraulic cylinders, tilt the cloth 19, and move the SS7 scooped up in the tilted direction.

(6) In the above embodiment, the electrolyzed digestive juice is drained through the aeration tank 12 and the filtration tank 10. However, if the purification is insufficient, the digestive juice after the aeration tank 12 and the digestive juice after the filtration tank 10 are returned to the front of the electrolytic cell 4 and the flow rate adjusting tank 2 to perform electrolysis again. You may.

(7) In the above embodiment, the digestive juice of the biogas plant is treated as a difficult-to-purify liquid. However, all liquids that are difficult to purify by microorganisms (for example, liquids having a biological oxygen demand (BOD) or chemical oxygen demand (COD) exceeding 1000 (particularly liquids exceeding 10,000)) are to be treated. Can be. Specifically, manure from slurry stores, wastewater from milking facilities such as parlors, wastewater from artificial milk factories, wastewater from fishery processing plants, etc. can also be treated.

Claims (11)

It is a device for treating difficult-to-purify liquids.
The flow path for flowing the difficult-to-purify liquid and
At least a pair of electrodes provided in the flow path and arranged in the direction in which the difficult-to-purify liquid flows,
It is equipped with a power supply that supplies electric power to the electrodes.
The electrodes are configured to have an uneven shape with respect to the flow of the difficult-to-purify liquid, and the difficult-to-purify liquid meanders and flows between the at least a pair of electrodes.
The anode of the electrode is made of aluminum and the cathode is made of iron.
Further provided with a supplementary means for supplementing oxygen generated from the anode of the electrodes,
A difficult-to-purify liquid treatment apparatus, characterized in that the oxygen is used for aeration treatment of the difficult-to-purify liquid. It is a device for treating difficult-to-purify liquids.
The flow path for flowing the difficult-to-purify liquid and
At least a pair of electrodes provided in the flow path and arranged in the direction in which the difficult-to-purify liquid flows,
It is equipped with a power supply that supplies electric power to the electrodes.
The electrodes are configured in a mesh pattern.
The anode of the electrode is made of aluminum and the cathode is made of iron.
Further provided with a supplementary means for supplementing oxygen generated from the anode of the electrodes,
A difficult-to-purify liquid treatment apparatus, characterized in that the oxygen is used for aeration treatment of the difficult-to-purify liquid. It is a device for treating difficult-to-purify liquids.
The flow path for flowing the difficult-to-purify liquid and
At least a pair of electrodes provided in the flow path and arranged in the direction in which the difficult-to-purify liquid flows,
It is equipped with a power supply that supplies electric power to the electrodes.
The electrodes are configured to have an uneven shape with respect to the flow of the difficult-to-purify liquid, and the difficult-to-purify liquid meanders and flows between the at least a pair of electrodes.
The anode of the electrode is made of magnesium.
Further provided with a supplementary means for supplementing oxygen generated from the anode of the electrodes,
A difficult-to-purify liquid treatment apparatus, characterized in that the oxygen is used for aeration treatment of the difficult-to-purify liquid. It is a device for treating difficult-to-purify liquids.
The flow path for flowing the difficult-to-purify liquid and
At least a pair of electrodes provided in the flow path and arranged in the direction in which the difficult-to-purify liquid flows,
It is equipped with a power supply that supplies electric power to the electrodes.
The electrodes are configured in a mesh pattern.
The anode of the electrode is made of magnesium.
Further provided with a supplementary means for supplementing oxygen generated from the anode of the electrodes,
A difficult-to-purify liquid treatment apparatus, characterized in that the oxygen is used for aeration treatment of the difficult-to-purify liquid. In the difficult-to-purify liquid treatment apparatus according to any one of claims 1 to 4.
A scooping means for scooping up the solid remaining after being electrolyzed by the electrode is provided downstream of the electrode.
The scooping means is a difficult-to-purify liquid treatment apparatus, which is composed of a material that permeates a liquid and captures a solid, and at least a part of the scooping means is immersed in a flow path. In the difficult-to-purify liquid treatment apparatus according to any one of claims 1 to 5.
The electrode is a difficult-to-purify liquid treatment apparatus characterized in that a plurality of positive electrodes and a plurality of negative electrodes are alternately arranged. In the difficult-to-purify liquid treatment apparatus according to any one of claims 1 to 6.
A difficult-to-purify liquid treatment device characterized in that the bottom of the flow path is lowered toward the downstream. In the difficult-to-purify liquid treatment apparatus according to any one of claims 1 to 7.
A difficult-to-purify liquid treatment apparatus, characterized in that an electrolyte is added to the difficult-to-purify liquid before passing through the electrode. In the difficult-to-purify liquid treatment apparatus according to any one of claims 1 to 8.
A difficult-to-purify liquid treatment apparatus further comprising a trapping means for capturing hydrogen generated from a cathode among the electrodes. In the difficult-to-purify liquid treatment apparatus according to any one of claims 1 to 9.
The difficult-to-purify liquid is a difficult-to-purify liquid treatment apparatus having a BOD or COD of more than 1000 mg / l. In the difficult-to-purify liquid treatment apparatus according to any one of claims 1 to 10.
The difficult-to-purify liquid is one of digestive liquid of a biogas plant, manure from a slurry store, wastewater from a milking facility, wastewater from an artificial milk factory, and wastewater from a fishery processing plant.

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