Treatment system for strong-flavor liquor brewing wastewater condensate

Abstract

The invention belongs to the field of wastewater treatment and resource utilization, and provides a Luzhou-flavor liquor brewing wastewater condensate treatment system, which comprises: an adjusting tank, which is internally provided with an adjusting water pump; a water inlet of the anaerobic reactor is communicated with an outlet of the adjusting water pump; a water inlet of the aerobic tank is communicated with a water outlet of the anaerobic reactor; a water inlet of the sedimentation tank is communicated with a water outlet of the aerobic tank, and an overflow weir is arranged in the sedimentation tank; a water inlet of the external drainage tank is communicated with the overflow weir; the medicine dissolving tank is used for dissolving nutritive salt and is communicated with the adjusting tank through a metering pump; and the detection device is used for detecting the water quality in the external drainage pool. Aiming at the characteristics of high COD (Chemical Oxygen Demand) value, excellent biodegradability, almost no suspended matters and the like of condensate after evaporation and concentration of the wine brewing wastewater, the treatment system effectively degrades the wine brewing wastewater by utilizing an efficient and simple system, so that the effluent quality reaches the discharge standard. And resource utilization is realized to a certain extent, and production energy consumption can be reduced.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment and resource utilization, and particularly relates to a treatment system for condensate of wastewater from brewing Luzhou-flavor liquor. Background Art

[0002] Luzhou-aroma liquor is one of the traditional Chinese liquors, and its production process includes fermentation, dregs stacking, distillation and other steps.

[0003] During the entire production process of liquor, a large amount of brewing wastewater is generated, such as lees percolate, bottom liquid, yellow water, etc. These wastewaters usually contain a large amount of organic matter and volatile substances with strong odor. In addition, under the fermentation of brewer's yeast, many soluble organic substances with high nutritional value such as proteins, organic acids, and polypeptides are produced during the liquor brewing process and remain in the lees and brewing wastewater.

[0004] In order to recover the nutrients in brewery wastewater, the commonly used treatment method is to evaporate and concentrate the brewery wastewater to significantly reduce the amount of water and increase the recovery concentration. However, the condensate produced after evaporation still contains a large amount of small molecular organic matter and volatile substances, and its COD can usually reach 20,000 mg / L or above, and further treatment is still required to meet the discharge standards.

[0005] Therefore, it is of great significance to develop a system that can efficiently treat the condensate after evaporation and concentration of brewing wastewater, which can not only further reduce the environmental burden, but also improve the efficiency of the entire brewing wastewater treatment. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a treatment system for condensate of Luzhou-flavor liquor brewing wastewater, which can efficiently treat the condensate after evaporation and concentration of Luzhou-flavor liquor brewing wastewater to meet the emission standards and realize resource utilization to a certain extent, thereby reducing production energy consumption.

[0007] To achieve the above object, the present invention adopts the following technical scheme: a system for treating condensate from wastewater of Luzhou-flavor liquor brewing, comprising:

[0008] A regulating tank, in which a regulating water pump is arranged;

[0009] An anaerobic reactor, whose water inlet is connected to the outlet of the regulating water pump;

[0010] an aerobic tank, the water inlet of which is connected to the water outlet of the anaerobic reactor;

[0011] A sedimentation tank, whose water inlet is connected to the water outlet of the aerobic tank, and an overflow weir is provided in the sedimentation tank;

[0012] an external drainage pool, the water inlet of which is connected to the overflow weir;

[0013] A medicine dissolving tank, used for dissolving nutrient salts, the medicine dissolving tank is connected with the regulating tank via a metering pump;

[0014] The detection device is used to detect the water quality in the external drainage pool.

[0015] Preferably, a sludge conditioning tank is further included, and the sludge discharge port of the anaerobic reactor is connected to the sludge conditioning tank.

[0016] Preferably, a sludge pump is provided in the sedimentation tank, the sludge pump outlet is connected to the sludge conditioning tank via a sludge discharge pipe, and the sludge discharge pipe is connected to the aerobic tank via a sludge return pipe.

[0017] Preferably, a dosing device is also included, and the dosing device is connected to the sludge conditioning tank through a metering pump.

[0018] Preferably, a plate and frame filter press is further included, a plunger pump is provided in the sludge conditioning tank, the plunger pump outlet is connected to the plate and frame filter press inlet, and the filtrate outlet of the plate and frame filter press is connected to the regulating tank.

[0019] Preferably, it further comprises a purification storage device and a steam generator, wherein the gas outlet of the anaerobic reactor is communicated with the inlet of the purification storage device, and the outlet of the purification storage device is communicated with the inlet of the steam generator.

[0020] Preferably, the aerobic pool is provided with a hanging filler and a dissolved oxygen detector, and the aerobic pool is provided with an aeration pipe, which is connected to a fan.

[0021] Preferably, a thermometer, a pH meter and an ultrasonic level meter are provided in the regulating tank.

[0022] Preferably, the sedimentation tank is a radial flow sedimentation tank.

[0023] Preferably, a sludge scraper is provided in the sedimentation tank.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The invention provides a treatment system for the condensate of brewing wastewater of Luzhou-flavor liquor. The condensate after evaporation and concentration of brewing wastewater has high COD value, excellent biodegradability, and almost no suspended matter. The system uses an efficient and simple system to effectively degrade the condensate, so that the effluent quality meets the discharge standard. It also realizes resource utilization to a certain extent, and can reduce production energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the principle of a system for treating condensate from brewing wastewater of Luzhou-flavor liquor provided in an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of the connection structure of a system for treating condensate from brewing wastewater of Luzhou-flavor liquor provided in an embodiment of the present invention;

[0028] Figure 3 A schematic diagram of the connection structure of a system for treating condensate from brewing wastewater of Luzhou-flavor liquor provided in an embodiment of the present invention;

[0029] Figure 4 A front view structural schematic diagram of a scraper and related parts of a system for treating condensate from wastewater of Luzhou-flavor liquor brewing provided by an embodiment of the present invention;

[0030] Figure 5 A partial front view structural schematic diagram of a sludge scraper of a system for treating condensate from wastewater of Luzhou-flavor liquor brewing provided by an embodiment of the present invention;

[0031] Figure 6 A schematic diagram of the three-dimensional structure of a scraper and a mud-breaking part of a system for treating condensate from wastewater of Luzhou-flavor liquor brewing provided by an embodiment of the present invention;

[0032] Figure 7 A schematic diagram of the top view of the structure of a scraper blade and related parts of a system for treating condensate from brewing wastewater of Luzhou-flavor liquor provided in an embodiment of the present invention;

[0033] Figure 8 A schematic diagram of the top structure of a system for treating condensate from brewing wastewater of Luzhou-flavor liquor provided in an embodiment of the present invention, showing a compressed elastic connector.

[0034] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0035] 1. Regulating tank; 2. Anaerobic reactor; 3. Aerobic tank; 4. Sedimentation tank; 5. External drainage tank; 6. Dissolving tank; 7. Detection device; 8. Regulating water pump; 9. Sludge conditioning tank; 10. Sludge pump; 11. Sludge discharge pipe; 12. Sludge return pipe; 13. Dosing device; 14. Plate and frame filter press; 15. Sludge scraper frame; 16. Sludge scraper plate; 17. Sludge breaking part; 18. Support frame; 19. Elastic connector; 20. Connecting rod. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0037] It should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integrally formed structure. For ordinary technicians in this field, the specific meaning of such terms in this patent can be understood according to specific circumstances.

[0038] Example 1

[0039] The condensate produced by the traditional evaporation and concentration process of brewing wastewater has a temperature of about 40°C and a COD of 30,000 mg / L. It contains very little nitrogen and phosphorus, and its main components are small molecule organic acids and small molecule esters.

[0040] In view of the above characteristics, this embodiment provides a system for treating condensate from wastewater of Luzhou-flavor liquor brewing. Figure 1-2 ,include:

[0041] The regulating tank 1 is provided with a regulating water pump 8, a thermometer, a pH meter, and an ultrasonic level meter. The thermometer can detect the temperature of the liquid in the regulating tank 1, the pH meter is used to detect the pH value, and the ultrasonic level meter is used to detect the height of the liquid level in the regulating tank 1. The regulating tank 1 is also equipped with a circulating pump system for mixing the liquid therein uniformly;

[0042] The anaerobic reactor 2 may be an anaerobic tank, whose water inlet is connected to the outlet of the regulating water pump 8 through a pipeline, and a water distributor is provided at the bottom thereof, and the water distributor is connected to the water inlet of the anaerobic reactor 2. The anaerobic reactor 2 is a prior art, and is also equipped with a circulation pipeline, a three-phase separator and other components;

[0043] The aerobic tank 3 has a water inlet connected to the water outlet of the anaerobic reactor 2 through a pipeline. The aerobic tank 3 is provided with a hanging filler and a dissolved oxygen detector. The bottom of the aerobic tank 3 is provided with an aeration pipe, which is connected to a Roots blower.

[0044] The sedimentation tank 4 has a water inlet connected to the water outlet of the aerobic tank 3 through a pipe, and an overflow weir is provided in the sedimentation tank 4. For example, the sedimentation tank 4 can be a mud bucket type radial flow sedimentation tank, and the central water inlet pipe is connected to the water outlet of the aerobic tank 3 through a pipe. The sedimentation tank 4 is also provided with a sludge scraper for scraping sludge on the bottom wall of the tank;

[0045] An external drainage tank 5, whose water inlet is connected to the overflow weir of the sedimentation tank 4 through a pipeline;

[0046] The medicine dissolving tank 6 is used to dissolve nutrient salts. The medicine dissolving tank 6 is connected to the regulating tank 1 through a metering pump to replenish nutrients such as N and P;

[0047] The detection device 7 is used to detect the water quality in the external drainage pool 5.

[0048] Based on the above structure, the condensate generated during the evaporation and concentration of brewing wastewater is pumped to the regulating tank 1 for heat preservation and storage in advance, and the thermometer, pH meter and ultrasonic level meter are used for online monitoring, so that the initial parameter index of the condensate can be monitored in real time, and the initial parameter index is transmitted to the control center and recorded. At the same time, nutrient salts such as nitrogen salts and phosphate salts are dissolved in the dissolving tank 6, and the dosage is calculated and set according to the inlet water quality conditions, added to the regulating tank 1 through the metering pump, and fully mixed through the circulating pump system equipped with the regulating tank 1.

[0049] The condensate after adding nutrient salts is pumped to the water inlet of the anaerobic reactor 2 by adjusting the water pump 8, and then evenly enters the first reaction zone through the water distributor, is fully mixed and contacted with the microorganisms in the sludge bed and the sludge suspension layer, and undergoes anaerobically decomposed to degrade most of the organic matter and produce a large amount of biogas. Subsequently, the condensate treated in the first reaction zone enters the second reaction zone through the three-phase separator for reaction, and solid-liquid separation is performed after the reaction. Part of the effluent from the solid-liquid separation is used as the circulating water of the anaerobic reactor 2 for circulating reaction, and the other part flows into the subsequent aerobic tank 3 through the outlet of the anaerobic reactor 2.

[0050] The aerobic tank 3 is in the form of a contact oxidation tank, and aerobic aeration is performed through a Roots blower and an aeration pipe, so that the condensate inside is fully in contact with the biofilm fixed on the surface of the filler, and the remaining organic matter in the condensate is further removed through biodegradation.

[0051] The effluent from the aerobic pool 3 enters the pool through the central water inlet pipe of the sedimentation pool 4, and then flows radially around the pool to separate solids and liquids. After the effluent overflows to the effluent weir, it enters the external drainage pool 5 for temporary storage, and is sampled and monitored by the detection device 7. After confirming that the water quality meets the standard, it is discharged into the municipal sewage network. Among them, the detection device 7 is a prior art. For example, the detection device 7 can automatically collect wastewater in the external drainage pool 5, detect the SS content in the wastewater, and then feed back the information to the control center for the staff to judge.

[0052] In summary, the treatment system provided in this embodiment uses an efficient and simple system to effectively degrade the condensate after evaporation and concentration of brewing wastewater, which has high COD value, excellent biodegradability, and almost no suspended matter, so that the effluent water quality meets the discharge standard. It also realizes resource utilization to a certain extent, which can reduce production energy consumption.

[0053] See also Figure 3 The treatment system provided in this embodiment further includes a sludge conditioning tank 9, and the sludge discharge port of the anaerobic reactor 2 is connected to the sludge conditioning tank 9. In this way, the sludge discharged from the anaerobic reactor 2 can enter the sludge conditioning tank 9 through the sludge discharge port.

[0054] A sludge pump 10 is provided in the sedimentation tank 4, and the outlet of the sludge pump 10 is connected to the sludge conditioning tank 9 through a sludge discharge pipe 11, and the sludge discharge pipe 11 is connected to the aerobic tank 3 through a sludge return pipe 12. The sludge in the sedimentation tank 4 can be scraped to the bottom of the sludge hopper by a sludge scraper, and then sent to the sludge discharge pipe 11 by the sludge pump 10, a part of which is returned to the aerobic tank 3 through the sludge return pipe 12, and the other part is sent to the sludge conditioning tank 9.

[0055] The treatment system provided in this embodiment further includes a dosing device 13, which is connected to the sludge conditioning tank 9 through a metering pump. The dosing device 13 is a prior art device used to add chemicals to condition the sludge.

[0056] The treatment system provided in this embodiment further includes a plate-frame filter press 14, a plunger pump is provided in the sludge conditioning tank 9, the plunger pump outlet is connected to the plate-frame filter press 14 inlet, and the filtrate outlet of the plate-frame filter press 14 is connected to the regulating tank 1. A sludge scraper may be provided in the sludge conditioning tank 9.

[0057] Specifically, after PAM (polyacrylamide) is dissolved in the dosing device 13, it is added to the sludge conditioning tank 9 through a metering pump, stirred and mixed evenly. Then it is sent to the plate and frame filter press 14 through a plunger pump for pressure filtration and dehydration, and the moisture content of the output mud cake reaches 70% or less. The generated filtrate is pumped back to the regulating tank 1, and the mud cake is transported out for disposal.

[0058] In this embodiment, the amount of biogas produced by anaerobic fermentation of condensate is large and the composition is clean, so the utilization value is high. In order to make full use of this part of biogas, the treatment system provided in this embodiment also includes a purification storage device and a steam generator, the gas outlet of the anaerobic reactor 2 is connected to the inlet of the purification storage device, and the outlet of the purification storage device is connected to the inlet of the steam generator.

[0059] Among them, the purification and storage device includes a biogas dehydration tank and a gas holder. The biogas generated by the anaerobic reactor 2 can enter the biogas dehydration tank through the gas-liquid separator on the top, and be sent to the gas holder for storage after dehydration, and then converted through the biogas steam generator. The generated steam can be used for production and life in the factory area as needed. Thereby realizing the resource reuse of biogas and reducing production costs. It should be noted that the working principle of the biogas steam generator is to convert the chemical energy of biogas into a continuous and stable steam heat source system. The heat generated by burning biogas is used to heat the water in the boiler and vaporize it into steam.

[0060] The treatment system provided in this embodiment also includes a flare emergency system. When the generated biogas cannot be used, it is directly burned through the exhaust port of the flare emergency system without the need for storage.

[0061] Example 2

[0062] Based on Example 1, see Figure 4 The scraper can include a scraper frame 15, a scraper blade 16 disposed at the bottom of the scraper frame 15, and a driving mechanism for driving the scraper frame 15 to rotate. The scraper frame 15 is adapted to the bottom wall of the pool so that the bottom end of the scraper blade 16 can contact the bottom wall of the pool.

[0063] Specifically, the scraper includes two scraper frames 15, and the bottom ends of the two scraper frames 15 are provided with a plurality of scraper blades 16 spaced apart along the length direction, and the scraper blades 16 at the bottom ends of the two scraper frames 15 are complementary. Figure 5 Four scraper plates 16 are provided at the bottom of the left scraper frame 15, and three scraper plates 16 are provided at the bottom of the right scraper frame 15. When the right scraper frame 15 rotates to the original position of the left scraper frame 15, the three scraper plates 16 at the bottom of the right scraper frame 15 are just located between the gaps of the four scraper plates 16 at the bottom of the left scraper frame 15.

[0064] In this way, when the two scraper racks 15 rotate one circle, the entire bottom wall of the pool can be scraped and swept without missing anything. In addition, the multiple scraper blades 16 at the bottom of the same scraper rack 15 are arranged at intervals, and the scraped sludge can pass through the gaps between the scraper blades 16, thereby reducing the resistance of the scraper blades 16 when rotating. This is because if the scraper blades 16 are arranged continuously, the scraper blades 16 will inevitably encounter greater resistance when rotating.

[0065] See also Figure 6 The scraper blade 16 is similar to a triangular prism structure and is arranged radially along the bottom wall of the pool. The scraper blade 16 is formed with a first end face at one end near the center of the bottom wall of the pool, and the first end face is a right-angled triangle structure. The scraper blade 16 is formed with a second end face at the other end, and the second end face is also a right-angled triangle structure. The height of the second end face is the same as that of the first end face, and the long side of the second end face is greater than the long side of the first end face, so that the second end face is more convex than the first end face.

[0066] Since the first end face and the second end face are both right-angled triangle structures, the resistance of the sludge to the scraper blade 16 is small during the rotation process, and at the same time, an upward thrust is generated on the sludge, so that the sludge is separated from the bottom wall of the pool. In addition, during the rotation process of the scraper blade 16, the second end face of the scraper blade 16 (the end away from the center of the bottom wall of the pool) is more protruding, which will preferentially scrape up the sludge attached to the bottom wall of the pool, and generate a radial thrust on the sludge, so that the sludge moves toward the center of the bottom wall of the pool after being scraped up, thereby accelerating the sludge collection efficiency and preventing the sludge from falling again and attaching to the bottom wall of the pool after being scraped up.

[0067] See also Figure 6-8In this embodiment, the scraper blade 16 is fixedly connected with the mud breaking part 17, the bottom end of the scraper frame 15 is fixed with a support frame 18, a connecting rod 20 is fixed on the support frame 18, the mud breaking part 17 is hinged with the connecting rod 20, and the scraper blade 16 is elastically connected with the support frame 18 through an elastic connector 19. When the elastic connector 19 is in a natural state, the scraper blade 16 maintains a radial arrangement.

[0068] The mud breaking portion 17 is fixed to the second end face of the scraper plate 16 (the end away from the center of the bottom wall of the pool). The mud breaking portion 17 is a triangular structure. The end of the mud breaking portion 17 close to the scraper plate 16 is adapted to the second end face of the scraper plate 16, and the end of the mud breaking portion 17 close to the scraper plate 16 is fitted and fixed to the second end face of the scraper plate 16.

[0069] In this way, during the rotation of the scraper 16, the scraper 16 will be subjected to the resistance of the sludge. Since the end of the scraper 16 near the center of the pool bottom wall is elastically connected to the support frame 18 through the elastic connector 19, the end of the scraper 16 near the center of the pool bottom wall is pressed to swing backward, that is, the elastic connector 19 is compressed, and the first end face of the scraper 16 gradually approaches the support frame 18. After the elastic connector 19 is compressed, an elastic force is generated, which acts on the scraped sludge through the scraper 16, generating a force on the sludge toward the center of the pool bottom wall, thereby improving the efficiency of collecting the sludge to the center of the pool bottom wall.

[0070] For example, when the scraper blade 16 scrapes a sludge pile, the elastic connector 19 is compressed, and the scraper blade 16 can first scrape up the sludge pile, so that the sludge pile is separated from the bottom wall of the pool. At the same time, due to the action of the elastic connector 19, the scraper blade 16 generates a force toward the center of the bottom wall of the pool on the sludge pile, so that the sludge pile moves quickly toward the center of the bottom wall of the pool, thereby improving the efficiency of collecting sludge to the center of the bottom wall of the pool. For sedimentation tanks with more sludge piles, the sludge collection efficiency is excellent.

[0071] In addition, when the first end of the scraper blade 16 approaches the support frame 18, due to the arrangement of the mud breaking portion 17, the mud resistance experienced by the scraper blade 16 is still relatively small, thereby improving the sludge collection efficiency.

[0072] The mechanisms, components and parts not specifically described in the present invention are all existing structures in the prior art and can be directly purchased from the market.

[0073] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, and a specific direction structure and operation, and therefore, cannot be understood as a limitation on the present invention. In addition, "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0074] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for treating condensate from wastewater from brewing Luzhou-flavor liquor, characterized in that: include: A regulating tank (1) having a regulating water pump (8) disposed therein; The water inlet of the anaerobic reactor (2) is connected to the outlet of the regulating water pump (8); an aerobic tank (3), the water inlet of which is connected to the water outlet of the anaerobic reactor (2); A sedimentation tank (4), the water inlet of which is connected to the water outlet of the aerobic tank (3), and an overflow weir is provided in the sedimentation tank (4); an external drainage pool (5), the water inlet of which is connected to the overflow weir; A drug dissolving tank (6) is used to dissolve nutrient salts, and the drug dissolving tank (6) is connected to the regulating tank (1) via a metering pump; A detection device (7) is used to detect the water quality in the external drainage pool (5).

2. A system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 1, characterized in that: It also comprises a sludge conditioning tank (9), and the sludge discharge port of the anaerobic reactor (2) is connected to the sludge conditioning tank (9).

3. A system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 2, characterized in that: A sludge pump (10) is provided in the sedimentation tank (4); the outlet of the sludge pump (10) is connected to the sludge conditioning tank (9) via a sludge discharge pipe (11); and the sludge discharge pipe (11) is connected to the aerobic tank (3) via a sludge return pipe (12).

4. A system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 3, characterized in that: It also includes a dosing device (13), and the dosing device (13) is connected to the sludge conditioning tank (9) via a metering pump.

5. A system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 4, characterized in that: It also includes a plate and frame filter press (14), a plunger pump is provided in the sludge conditioning tank (9), the outlet of the plunger pump is connected to the inlet of the plate and frame filter press (14), and the filtrate outlet of the plate and frame filter press (14) is connected to the regulating tank (1).

6. A system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 1, characterized in that: It also comprises a purification storage device and a steam generator, wherein the gas outlet of the anaerobic reactor (2) is connected to the inlet of the purification storage device, and the outlet of the purification storage device is connected to the inlet of the steam generator.

7. A system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 1, characterized in that: The aerobic pool (3) is provided with a hanging filler and a dissolved oxygen detector, and the aerobic pool (3) is provided with an aeration pipe, and the aeration pipe is connected to a fan.

8. The system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 1, characterized in that: The regulating tank (1) is provided with a thermometer, a pH meter and an ultrasonic liquid level meter.

9. The system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 1, characterized in that: The sedimentation tank (4) is a radial flow sedimentation tank.

10. The system for treating condensate from brewing wastewater of Luzhou-flavor liquor according to claim 1, characterized in that: A mud scraper is provided in the sedimentation tank (4).

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