A softening device for dtro concentrate

Abstract

The application discloses a softening device for DTRO concentrate, and belongs to the technical field of DTRO concentrate treatment, which comprises a ladder-shaped lifting frame, a first reaction tank is fixedly installed at the top end of the ladder-shaped lifting frame, a second reaction tank is fixedly installed at the top of the ladder-shaped lifting frame, a sedimentation tank is fixedly installed on one side of the ladder-shaped lifting frame, an inclined pipe separation device is installed in the sedimentation tank, the first reaction tank, the second reaction tank and the sedimentation tank are arranged in a ladder shape, a drain pipe is installed at the bottom of each of the first reaction tank and the second reaction tank, a first stirring mechanism and a dosing mechanism are arranged in the ladder-shaped lifting frame, a second stirring mechanism is arranged in the second reaction tank, a filtrate tank is placed on one side of the sedimentation tank, and an intermediate tank is in communication between the sedimentation tank and the filtrate tank; the application can effectively remove hardness ions in the DTRO concentrate, and can soften the DTRO concentrate, thereby being beneficial to stable operation of a subsequent treatment process of the DTRO concentrate.

Description

Technical Field

[0001] This application relates to the field of DTRO concentrate treatment technology, and more particularly to a softening device for DTRO concentrate. Background Technology

[0002] DTRO concentrate is a high-concentration residual liquid from landfill leachate or industrial wastewater after membrane treatment. It contains high concentrations of hardening components such as calcium and magnesium ions and sulfates.

[0003] Existing technologies do not soften the DTRO concentrate in the DTRO concentrate. High concentrations of calcium and magnesium ions will form stubborn scale during subsequent membrane treatment or evaporation, causing membrane pore blockage and affecting subsequent treatment processes.

[0004] Therefore, a softening device for DTRO concentrate is provided. Utility Model Content

[0005] To address the shortcomings of existing technologies, this application provides a softening device for DTRO concentrate, which overcomes the deficiencies of existing technologies and aims to solve the problem that existing technologies do not perform softening treatment on DTRO concentrate, resulting in high concentrations of calcium and magnesium ions forming stubborn scale during subsequent membrane treatment or evaporation, leading to membrane pore blockage and affecting subsequent treatment processes.

[0006] To achieve the above objectives, this application provides the following technical solution: a softening device for DTRO concentrate, comprising a ladder-shaped lifting frame, a first reaction tank fixedly installed at the top of the ladder-shaped lifting frame, a second reaction tank fixedly installed at the top of the ladder-shaped lifting frame, a settling tank fixedly installed on one side of the ladder-shaped lifting frame, an inclined tube separation device installed inside the settling tank, the first reaction tank, the second reaction tank, and the settling tank being arranged in a stepped manner, a drain pipe installed at the bottom of both the first reaction tank and the second reaction tank, a first stirring mechanism and a dosing mechanism being provided inside the ladder-shaped lifting frame, a second stirring mechanism being provided inside the second reaction tank, a filtrate tank being placed on one side of the settling tank, and an intermediate tank connecting the settling tank and the filtrate tank.

[0007] By adopting the above technical solution, DTRO concentrate is first added to the first reaction tank. Sodium hydroxide and sodium carbonate solutions are added to the first reaction tank through a dosing mechanism to conduct a preliminary chemical reaction with the DTRO concentrate. The DTRO concentrate and reagents are then thoroughly stirred by a first stirring mechanism. The fully stirred liquid in the first reaction tank flows into the second reaction tank through a drain pipe connected to the first reaction tank. The first reaction tank, the second reaction tank, and the settling tank are arranged in a stepped manner to facilitate gravity flow of the liquid. The liquid in the second reaction tank is stirred again by a second stirring mechanism to ensure that calcium, magnesium, and silicon ions in the wastewater react fully with carbonate and hydroxide ions. By extending the reaction time, precipitates are fully formed, resulting in solid precipitates. Then, the mud-water mixture in the second reaction tank flows into the settling tank through a drain pipe connected to the second reaction tank. Solid-liquid separation is achieved through an inclined tube separator. The supernatant flows into the intermediate filtrate tank through an intermediate tank. The filtrate tank stores the purified final product water, thereby effectively removing hardness ions from the DTRO concentrate and softening it, which is beneficial to the stable operation of subsequent DTRO concentrate treatment processes.

[0008] As a preferred technical solution of this application, a sludge tank is installed inside the trapezoidal raised frame, and a sludge conveying pump is fixedly installed inside the trapezoidal raised frame on one side of the sludge tank. The extraction end of the sludge conveying pump is connected to the bottom of the settling tank by a sludge suction pipe, and the discharge end of the sludge conveying pump is connected to the top of the sludge tank by a conveying pipe.

[0009] By adopting the above technical solution, solid-liquid separation in the settling tank is achieved through an inclined tube separation device. The supernatant flows into the intermediate tank of the filtrate tank, while the bottom solids are pumped into the sludge tank by a sludge transfer pump, thereby automatically collecting the sludge in the sludge tank for unified sludge treatment.

[0010] As a preferred technical solution of this application, both sets of drainage pipes are fixedly equipped with an electrically controlled valve.

[0011] By adopting the above technical solution, the opening and closing of the drain pipe can be easily controlled by the second electric control valve, which improves the practicality during use.

[0012] As a preferred technical solution of this application, the first stirring mechanism includes a horizontal plate, which is fixedly installed at the top of the first reaction tank. A rotating shaft is rotatably connected to the top of the horizontal plate, and a plurality of stirring shafts are fixedly installed on the outer surface of the rotating shaft. A motor is fixedly installed at the top of the horizontal plate, and the output end of the motor is fixedly installed with the rotating shaft.

[0013] By adopting the above technical solution, the DTRO concentrate and the reagent are stirred by the motor driving the rotating shaft and the stirring shaft, which improves the thoroughness of the mixing between the reagent and the concentrate.

[0014] As a preferred technical solution of this application, the drug delivery mechanism includes a drug storage tank, which is fixedly installed at the top of the horizontal plate, and a feeding pipe is fixedly installed at the bottom of the horizontal plate, which is connected to the drug storage tank. A drug inlet pipe is fixedly installed at the top of the drug storage tank.

[0015] By adopting the above technical solution, the agent is added into the storage tank through the storage tank, the storage tank stores the agent, and the agent in the storage tank is added to the first reaction tank through the feeding pipe, thereby achieving the effect of automatic drug dosing in the first reaction tank.

[0016] As a preferred embodiment of this application, the second stirring mechanism includes a second horizontal plate, which is fixedly installed at the top of the second reaction tank. A bracket is fixedly installed at the top of the second horizontal plate, and a forward rotating shaft is rotatably installed at the top of the second horizontal plate. A reverse rotating shaft is rotatably connected inside the forward rotating shaft, and the top of the reverse rotating shaft is rotatably connected to the bracket. Two sets of stirring blades are fixedly installed on the outer surfaces of both the forward and reverse rotating shafts. A driven bevel gear two is fixedly installed at the top of the forward rotating shaft, and a driven bevel gear one is fixedly installed at the top of the reverse rotating shaft. A second motor is fixedly installed at the top of the second horizontal plate, and a driving bevel gear is fixedly installed at the output end of the second motor. The driving bevel gear meshes with both the driven bevel gear one and the driven bevel gear two. Several sets of guide holes are opened on the outer surface of the reverse rotating shaft.

[0017] By adopting the above technical solution, the active bevel gear is driven to rotate by the second motor. The active bevel gear is linked with the driven bevel gear one and the driven bevel gear two to rotate synchronously. The driven bevel gear one and the driven bevel gear two rotate in opposite directions, thereby driving the stirring blades on the forward rotating shaft and the reverse rotating shaft to rotate in opposite directions, which improves the stirring efficiency of the liquid in the second reaction tank. With the help of several sets of guide holes, the stirring efficiency is further improved.

[0018] As a preferred technical solution of this application, a pH monitor is fixedly installed on the inner wall of the first reaction tank, a controller is fixedly installed at the top of the first reaction tank on one side of the drug storage tank, an electric control valve is fixedly installed inside the feeding pipe, and the electric control valve, the pH monitor, and the electric control valve are all electrically connected to the controller.

[0019] By adopting the above technical solution, the pH of the liquid in the first reaction tank is automatically monitored by a pH monitor. The controller controls the first and second electrically controlled valves based on the data from the pH monitor, thereby achieving precise dosing of reagents and control of liquid level in the first reaction tank, which improves the automation level of the process.

[0020] As a preferred technical solution of this application, a filter press is installed on the top of the sludge tank, and a liquid extraction pipe is connected between the bottom of the sludge tank and the first reaction tank.

[0021] By adopting the above technical solution, the sludge in the sludge tank is dewatered by a filter press, and the filtrate is returned to the first reaction tank for recycling through a suction pipe, which improves the practicality of use.

[0022] The beneficial effects of this application are:

[0023] 1. First, DTRO concentrate is added to the first reaction tank. Sodium hydroxide and sodium carbonate solutions are added to the first reaction tank through the dosing mechanism to initiate a preliminary chemical reaction with the DTRO concentrate. The first stirring mechanism thoroughly stirs the DTRO concentrate and reagents. The thoroughly stirred liquid in the first reaction tank flows into the second reaction tank through the drain pipe connected to the first reaction tank. The first reaction tank, second reaction tank, and settling tank are arranged in a stepped manner to facilitate gravity flow of the liquid. The second stirring mechanism thoroughly stirs the liquid in the second reaction tank again, allowing calcium, magnesium, and silicon ions in the wastewater to fully react with carbonate and hydroxide ions. By extending the reaction time, precipitates are fully formed, resulting in solid precipitates. Then, the mud-water mixture in the second reaction tank flows into the settling tank through the drain pipe connected to the second reaction tank. Solid-liquid separation is achieved through an inclined tube separator. The supernatant flows into the filtrate tank through the intermediate tank. The filtrate tank stores the purified final product water, thereby effectively removing hardness ions from the DTRO concentrate and softening it, which is beneficial to the stable operation of subsequent DTRO concentrate treatment processes.

[0024] 2. Solid-liquid separation in the settling tank is achieved through an inclined tube separation device. The supernatant flows into the intermediate tank of the filtrate tank through the intermediate tank, while the bottom solids are pumped into the sludge tank by a sludge transfer pump, thereby automatically collecting the sludge in the sludge tank for unified treatment. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of this application;

[0026] Figure 2 This is a schematic diagram of the internal structure of this application;

[0027] Figure 3 for Figure 2 Enlarged structural diagram at point A in the middle;

[0028] Figure 4 for Figure 2 Enlarged structural diagram at point B.

[0029] In the diagram: 1. Ladder-shaped lifting frame; 2. First reaction tank; 3. Second reaction tank; 4. Settling tank; 5. Intermediate tank; 6. Filtration tank; 7. First stirring mechanism; 701. Horizontal plate one; 702. Rotating shaft; 703. Stirring shaft; 704. Motor one; 8. Second stirring mechanism; 801. Horizontal plate two; 802. Forward rotating shaft; 803. Stirring blade; 804. Reverse rotating shaft; 805. Driven bevel gear one; 806. Driven bevel gear two; 80 7. Motor II; 808. Drive bevel gear; 809. Support frame; 9. Dosing mechanism; 901. Storage tank; 902. Feeding pipe; 903. Inlet pipe; 10. pH monitor; 11. Controller; 12. Electrically controlled valve I; 13. Sludge tank; 14. Sludge transfer pump; 15. Sludge suction pipe; 16. Transfer pipe; 17. Drain pipe; 18. Electrically controlled valve II; 19. Filter press; 20. Suction pipe; 21. Inclined tube separator; 22. Guide hole. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Reference Figure 1-4 A softening device for DTRO concentrate includes a ladder-shaped lifting frame 1. A first reaction tank 2 is fixedly installed at the top of the ladder-shaped lifting frame 1, and a second reaction tank 3 is fixedly installed at the top of the ladder-shaped lifting frame 1. A settling tank 4 is fixedly installed on one side of the ladder-shaped lifting frame 1. An inclined tube separation device 21 is installed inside the settling tank 4. The first reaction tank 2, the second reaction tank 3, and the settling tank 4 are arranged in a stepped manner. Drain pipes 17 are installed at the bottom of both the first reaction tank 2 and the second reaction tank 3. A first stirring mechanism 7 and a dosing mechanism 9 are provided inside the ladder-shaped lifting frame 1. A second stirring mechanism 8 is provided inside the second reaction tank 3. A filtrate tank 6 is placed on one side of the settling tank 4. An intermediate tank 5 connects the settling tank 4 and the filtrate tank 6. An electrically controlled valve 18 is fixedly installed inside both sets of drain pipes 17.

[0032] First, DTRO concentrate is added to the first reaction tank 2. Sodium hydroxide and sodium carbonate solutions are then added to the first reaction tank 2 via the dosing mechanism 9 to initiate a preliminary chemical reaction with the DTRO concentrate. The first stirring mechanism 7 thoroughly stirs the DTRO concentrate and reagents. The thoroughly stirred liquid in the first reaction tank 2 flows into the second reaction tank 3 through the drain pipe 17 connected to the first reaction tank 2. The first reaction tank 2, second reaction tank 3, and settling tank 4 are arranged in a stepped manner to facilitate gravity flow. The second stirring mechanism 8 further thoroughly stirs the liquid in the second reaction tank 3, allowing calcium, magnesium, and silicon ions in the wastewater to react with carbonate and hydroxide ions. The reaction is fully completed, and the reaction time is extended to allow the precipitate to fully form, resulting in a solid precipitate. Then, the mud-water mixture in the second reaction tank 3 flows into the settling tank 4 through the drain pipe 17 connected to the second reaction tank 3. Solid-liquid separation is achieved through the inclined tube separation device 21. The supernatant flows into the filtrate tank 6 through the intermediate tank 5. The filtrate tank 6 stores the purified final product water, thereby effectively removing hardness ions from the DTRO concentrate and softening the DTRO concentrate, which is beneficial to the stable operation of subsequent DTRO concentrate treatment processes. The opening and closing of the drain pipe 17 can be easily controlled by the electronically controlled valve 18, which improves the practicality of use.

[0033] Reference Figure 1-3 The ladder-shaped lifting frame 1 houses a sludge tank 13. A sludge conveying pump 14 is fixedly installed inside the ladder-shaped lifting frame 1 on one side of the sludge tank 13. The extraction end of the sludge conveying pump 14 is connected to the bottom of the settling tank 4 via a sludge suction pipe 15. The discharge end of the sludge conveying pump 14 is connected to the top of the sludge tank 13 via a conveying pipe 16. The first stirring mechanism 7 includes a horizontal plate 701, which is fixedly installed at the top of the first reaction tank 2. A rotating shaft 702 is rotatably connected to the top of the horizontal plate 701. Several sets of stirring shafts 703 are fixedly installed on the outer surface of the rotating shaft 702. A motor 704 is fixedly installed at the top of the horizontal plate 701. The output end of the motor 704 is fixedly installed to the rotating shaft 702.

[0034] Solid-liquid separation is achieved in the sedimentation tank 4 by the inclined tube separation device 21. The supernatant flows into the intermediate tank 6 through the intermediate tank 5, and the bottom solids are pumped into the sludge tank 13 by the sludge transfer pump 14, so that the sludge is automatically collected in the sludge tank 13 for unified treatment. The DTRO concentrate and the reagent are stirred by the motor 704 driving the rotating shaft 702 and the stirring shaft 703, which improves the fullness of mixing between the reagent and the concentrate.

[0035] Reference Figure 2-4The dosing mechanism 9 includes a storage tank 901, which is fixedly installed at the top of a horizontal plate 701. A feeding pipe 902 is fixedly installed at the bottom of the horizontal plate 701 and is connected to the storage tank 901. An inlet pipe 903 is fixedly installed at the top of the storage tank 901. A pH monitor 10 is fixedly installed on the inner wall of the first reaction tank 2. A controller 11 is fixedly installed at the top of the first reaction tank 2 on one side of the storage tank 901. An electric control valve 12 is fixedly installed inside the feeding pipe 902. The electric control valve 12, pH monitor 10, and electric control valve 18 are connected to each other. All are electrically connected to the controller 11; the agent is added to the storage tank 901 through the storage tank 901, the storage tank 901 stores the agent, and the agent in the storage tank 901 is added to the first reaction tank 2 through the feeding pipe 902, so as to achieve the effect of automatic dosing of the agent in the first reaction tank 2; the pH monitor 10 automatically monitors the pH of the liquid in the first reaction tank 2, and the controller 11 controls the electric control valve 12 and the electric control valve 18 through the data of the pH monitor 10, so as to achieve precise dosing of the agent and liquid level control in the first reaction tank 2, thereby improving the automation level of the process.

[0036] Reference Figure 2-4 The second stirring mechanism 8 includes a second horizontal plate 801, which is fixedly installed at the top of the second reaction tank 3. A bracket 809 is fixedly installed at the top of the second horizontal plate 801. A forward rotating shaft 802 is rotatably installed at the top of the second horizontal plate 801. A reverse rotating shaft 804 is rotatably connected inside the forward rotating shaft 802. The top of the reverse rotating shaft 804 is rotatably connected to the bracket 809. Two sets of stirring blades 803 are fixedly installed on the outer surfaces of both the forward rotating shaft 802 and the reverse rotating shaft 804. A driven bevel gear 806 is fixedly installed at the top of the forward rotating shaft 802, and a driven bevel gear 805 is fixedly installed at the top of the reverse rotating shaft 804. A second motor 807 is fixedly installed at the top of the second horizontal plate 801. A driving bevel gear 808 is fixedly installed at the output end of the second motor 807. The driving bevel gear 808 meshes with both the driven bevel gear 805 and the driven bevel gear 806. The outer surface of the reverse rotating shaft 804 is provided with several sets of guide holes 22; a filter press 19 is installed on the top of the sludge tank 13, and a liquid extraction pipe 20 is connected between the bottom of the sludge tank 13 and the first reaction tank 2; the motor 2 drives the active bevel gear 808 to rotate, and the active bevel gear 808 drives the driven bevel gear 1 805 and driven bevel gear 2 806 to rotate synchronously, and the driven bevel gear 1 805 and driven bevel gear 2 806 rotate in opposite directions, thereby driving the stirring blades 803 on the forward rotating shaft 802 and the reverse rotating shaft 804 to rotate in opposite directions, which improves the stirring efficiency of the liquid in the second reaction tank 3. With the help of several sets of guide holes 22, the stirring efficiency is further improved; the sludge in the sludge tank 13 is dewatered by the filter press 19, and the filtrate is returned to the first reaction tank 2 for circulation treatment through the liquid extraction pipe 20, which improves the practicality during use.

[0037] Working principle: First, DTRO concentrate is added to the first reaction tank 2. Sodium hydroxide and sodium carbonate solutions are added to the first reaction tank 2 via the dosing mechanism 9 to initiate a preliminary chemical reaction with the DTRO concentrate. The first stirring mechanism 7 thoroughly stirs the DTRO concentrate and reagents. The thoroughly stirred liquid in the first reaction tank 2 flows into the second reaction tank 3 through the drain pipe 17 connected to the first reaction tank 2. The first reaction tank 2, second reaction tank 3, and settling tank 4 are arranged in a stepped manner to facilitate gravity flow. The second stirring mechanism 8 further thoroughly stirs the liquid in the second reaction tank 3, allowing the calcium in the wastewater to be fully dissolved. Magnesium and silicon ions react fully with carbonate and hydroxide ions. By extending the reaction time, precipitates are fully formed, resulting in solid precipitates. The mud-water mixture in the second reaction tank 3 then flows into the settling tank 4 through the drain pipe 17 connected to the second reaction tank 3. Solid-liquid separation is achieved through the inclined tube separator 21. The supernatant flows into the filtrate tank 6 through the intermediate tank 5. The filtrate tank 6 stores the purified final product water. Solid-liquid separation is achieved in the settling tank 4 through the inclined tube separator 21. The supernatant flows into the filtrate tank 6 through the intermediate tank 5. The bottom solid matter is pumped into the sludge tank 13 by the sludge transfer pump 14.

[0038] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A softening device for DTRO concentrate comprising a ladder-like elevated frame (1), characterized in that, The top of the ladder-shaped lifting frame (1) is fixedly installed with a first reaction tank (2), the top of the ladder-shaped lifting frame (1) is fixedly installed with a second reaction tank (3), a sedimentation tank (4) is fixedly installed on one side of the ladder-shaped lifting frame (1), and an inclined tube separation device (21) is installed inside the sedimentation tank (4). The first reaction tank (2), the second reaction tank (3), and the sedimentation tank (4) are arranged in a stepped manner. The bottom of the first reaction tank (2) and the second reaction tank (3) are both equipped with a drain pipe (17). The ladder-shaped lifting frame (1) is equipped with a first stirring mechanism (7) and a dosing mechanism (9). The second reaction tank (3) is equipped with a second stirring mechanism (8). A filtrate tank (6) is placed on one side of the sedimentation tank (4). An intermediate tank (5) is connected between the sedimentation tank (4) and the filtrate tank (6).

2. The softening device for DTRO concentrate according to claim 1, characterized in that, The inside of the ladder-shaped lifting frame (1) is a sludge tank (13). A sludge conveying pump (14) is fixedly installed inside the ladder-shaped lifting frame (1) on one side of the sludge tank (13). The extraction end of the sludge conveying pump (14) is connected to the bottom of the sedimentation tank (4) by a sludge suction pipe (15). The discharge end of the sludge conveying pump (14) is connected to the top of the sludge tank (13) by a conveying pipe (16).

3. The softening device for DTRO concentrate according to claim 1, characterized in that, Both sets of drain pipes (17) are equipped with electrically controlled valves (18).

4. The softening device for DTRO concentrate according to claim 1, characterized in that, The first stirring mechanism (7) includes a horizontal plate (701), which is fixedly installed at the top of the first reaction tank (2). A rotating shaft (702) is rotatably connected to the top of the horizontal plate (701). Several sets of stirring shafts (703) are fixedly installed on the outer surface of the rotating shaft (702). A motor (704) is fixedly installed at the top of the horizontal plate (701). The output end of the motor (704) is fixedly installed with the rotating shaft (702).

5. A softening device for DTRO concentrate according to claim 4, characterized in that, The dosing mechanism (9) includes a medicine storage tank (901), which is fixedly installed at the top of the horizontal plate (701). A feeding pipe (902) is fixedly installed at the bottom of the horizontal plate (701), and the feeding pipe (902) is connected to the medicine storage tank (901). A medicine inlet pipe (903) is fixedly installed at the top of the medicine storage tank (901).

6. A softening device for DTRO concentrate according to claim 1, characterized in that, The second stirring mechanism (8) includes a second horizontal plate (801), which is fixedly installed at the top of the second reaction tank (3). A bracket (809) is fixedly installed at the top of the second horizontal plate (801). A forward rotating shaft (802) is rotatably installed at the top of the second horizontal plate (801). A reverse rotating shaft (804) is rotatably connected inside the forward rotating shaft (802). The top of the reverse rotating shaft (804) is rotatably connected to the bracket (809). Two sets of stirring rods are fixedly installed on the outer surfaces of both the forward rotating shaft (802) and the reverse rotating shaft (804). Leaf (803), the top of the forward rotating shaft (802) is fixedly installed with a driven bevel gear two (806), the top of the reverse rotating shaft (804) is fixedly installed with a driven bevel gear one (805), the top of the horizontal plate two (801) is fixedly installed with a motor two (807), the output end of the motor two (807) is fixedly installed with a driving bevel gear (808), the driving bevel gear (808) meshes with the driven bevel gear one (805) and the driven bevel gear two (806), and the outer surface of the reverse rotating shaft (804) is provided with several sets of guide holes (22).

7. A softening device for DTRO concentrate according to claim 5, characterized in that, A pH monitor (10) is fixedly installed on the inner wall of the first reaction tank (2). A controller (11) is fixedly installed on the top of the first reaction tank (2) on one side of the drug storage tank (901). An electric control valve (12) is fixedly installed inside the feeding pipe (902). The electric control valve (12), pH monitor (10), and electric control valve (18) are all electrically connected to the controller (11).

8. A softening device for DTRO concentrate according to claim 2, characterized in that, A filter press (19) is installed on the top of the sludge tank (13), and a liquid extraction pipe (20) is connected between the bottom of the sludge tank (13) and the first reaction tank (2).

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