Organic phosphorus-containing wastewater treatment system

Abstract

The utility model provides an organophosphorus-containing wastewater treatment system. The organophosphorus-containing wastewater treatment system comprises an adjusting tank, an oxidation unit, a physicochemical treatment unit and a biological reaction unit which are connected in sequence, wherein the adjusting tank is provided with an acid-base medicament feeding port; the oxidation unit is provided with an oxidant feeding port; the physicochemical treatment unit comprises a coagulation zone, a flocculation zone and a sedimentation zone which are connected in sequence; the coagulation area is provided with a coagulant feeding port, the flocculation area is provided with a flocculant feeding port, the bottom surface of the coagulation area is communicated with the bottom surface of the flocculation area through a pipeline, and the bottom surface of the coagulation area is higher than the bottom surface of the flocculation area; a biochar layer is arranged in the biological reaction unit and is suitable for degrading organic phosphorus-containing wastewater. The organophosphorus-containing wastewater treatment system disclosed by the utility model can realize efficient treatment of the organophosphorus-containing wastewater.

Description

Technical Field

[0001] The utility model relates to the technical field of wastewater treatment, in particular to a system for treating wastewater containing organic phosphorus. Background Art

[0002] Phosphorus-containing wastewater is one of the important causes of eutrophication of water bodies, which has a great adverse impact on the protection of water environment and the maintenance of ecological balance. The phosphorus-containing wastewater generated by the petrochemical industry mainly comes from circulating sewage. After evaporation and concentration, the sewage has the characteristics of high organic phosphorus concentration and difficulty in biodegradation.

[0003] At present, the phosphorus removal processes commonly used in sewage treatment mainly include physicochemical phosphorus removal and biological phosphorus removal. Among them, physicochemical phosphorus removal mainly achieves the purpose of phosphorus removal by adding agents to induce flocculation of phosphorus in the water, and then achieves the purpose of phosphorus removal by precipitation or filtration. Biological phosphorus removal mainly relies on the metabolism of organisms. After the biological bacteria absorb and release phosphorus, the phosphorus compounds are separated from the wastewater to achieve the purpose of phosphorus removal. However, physicochemical phosphorus removal is more suitable for the removal of inorganic phosphorus, and the removal effect on organic phosphorus is poor; biological phosphorus removal has the problem of low efficiency in organic phosphorus treatment, and the treatment indicators are difficult to meet the requirements of effluent indicators. The above-mentioned processes are difficult to meet the total phosphorus emission indicators for the treatment of circulating wastewater in petrochemical industry.

[0004] In view of this, there is an urgent need to propose a wastewater treatment system containing organic phosphorus to treat the circulating wastewater of petrochemical industry with high organic phosphorus concentration. Utility Model Content

[0005] The utility model aims to provide a system for treating wastewater containing organic phosphorus, so as to solve the problem that the existing wastewater treatment system is difficult to efficiently treat circulating wastewater of petrochemical industry with high organic phosphorus concentration.

[0006] In order to solve the above technical problems, the technical solution of the utility model is as follows:

[0007] A system for treating wastewater containing organic phosphorus, comprising a regulating tank, an oxidation unit, a physicochemical treatment unit, and a biological reaction unit connected in sequence:

[0008] The regulating tank is provided with an acid and alkali reagent input port, which is suitable for adjusting the pH value of the wastewater containing organic phosphorus;

[0009] The oxidation unit is provided with an oxidant inlet, suitable for reacting the organic phosphorus-containing wastewater with the oxidant;

[0010] The physicochemical treatment unit is suitable for reacting the wastewater containing organic phosphorus with a coagulant and a flocculant respectively, and removing the reaction precipitate, and comprises a coagulation zone, a flocculation zone, and a sedimentation zone connected in sequence; the coagulation zone is provided with a coagulant inlet, the flocculation zone is provided with a flocculant inlet, the bottom surface of the coagulation zone is connected with the bottom surface of the flocculation zone through a pipeline, and the bottom surface of the coagulation zone is higher than the bottom surface of the flocculation zone;

[0011] The biological reaction unit is provided with a biochar layer, which is suitable for degrading wastewater containing organic phosphorus.

[0012] Preferably, the organic phosphorus-containing wastewater treatment system further comprises a hardness removal unit, and the hardness removal unit is located between the oxidation unit and the physicochemical treatment unit.

[0013] Preferably, a de-hardening agent inlet is provided on the top of the de-hardening unit, and a stirring device is provided inside.

[0014] Preferably, a pneumatic stirring device is provided at the bottom of the regulating tank and / or the oxidation unit.

[0015] Preferably, the pneumatic stirring device comprises an exhaust pipe connected to an air source; and an air hole is provided on the exhaust pipe.

[0016] Preferably, a stirring device is provided inside the coagulation zone and / or the flocculation zone.

[0017] Preferably, an inclined pipe and a mud scraping device are provided in the sedimentation area.

[0018] Preferably, the mud scraping device comprises:

[0019] A motor, wherein the motor is located above the precipitation area;

[0020] A rotating shaft, the rotating shaft is connected to the output shaft of the motor, passes through the inclined tube, and is located at the center of the precipitation area;

[0021] A mounting frame, the mounting frame is located at an end of the rotating shaft and at the bottom of the precipitation area;

[0022] A scraper blade, the scraper blade is fixed on the mounting frame and is parallel to the bottom surface of the sedimentation area;

[0023] A guide plate, the guide plate is located below the rotating shaft, one end of the guide plate is connected to the scraper plate, and the other end extends downward;

[0024] The mud bucket is located below the sedimentation area and is in the shape of an inverted truncated cone, suitable for accommodating the guide plate.

[0025] Preferably, the mud bucket is provided with a mud discharge port and a return port;

[0026] The return port is located above the mud discharge port; the end of the guide plate extends to the return port.

[0027] Preferably, an aeration pipe and a backwashing pipe are provided below the biochar layer of the biological reaction unit.

[0028] The above solution of the utility model includes at least the following beneficial effects:

[0029] The organic phosphorus wastewater treatment system described in the utility model comprises a regulating tank, an oxidation unit, a physicochemical treatment unit and a biological reaction unit connected in sequence: the regulating tank is provided with an acid and alkali agent inlet, which is suitable for adjusting the pH value of the organic phosphorus wastewater; the oxidation unit is provided with an oxidant inlet, which is suitable for making the organic phosphorus wastewater react with the oxidant; the physicochemical treatment unit is suitable for making the organic phosphorus wastewater react with a coagulant and a flocculant respectively, and removing the reaction precipitate, and comprises a coagulation zone, a flocculation zone and a precipitation zone connected in sequence; the coagulation zone is provided with a coagulant inlet, the flocculation zone is provided with a flocculant inlet, the bottom surface of the coagulation zone is connected to the bottom surface of the flocculation zone through a pipeline, and the bottom surface of the coagulation zone is higher than the bottom surface of the flocculation zone; the biological reaction unit is provided with a biochar layer, which is suitable for degrading the organic phosphorus wastewater. The organic phosphorus wastewater treatment system described in the utility model first converts organic phosphorus into inorganic phosphorus and small-molecule organic phosphorus through the regulating tank and oxidation unit, then effectively removes inorganic phosphorus through the physicochemical treatment unit, and removes the remaining small-molecule organic phosphorus through the biological reaction unit, thereby realizing efficient treatment of organic phosphorus wastewater, which is conducive to achieving the total phosphorus emission index, and is particularly suitable for treating circulating wastewater from petrochemical industry with high organic phosphorus concentration.

[0030] Specifically, the pH value of the wastewater containing organic phosphorus is first adjusted through the regulating tank to make the pH value of the wastewater containing organic phosphorus under the suitable reaction conditions of the oxidant, and then the wastewater containing organic phosphorus is oxidized by the oxidation unit to destroy the chemical structure of organic phosphorus, so that most of it is decomposed into inorganic phosphorus, and a small part is converted into small molecular organic phosphorus. Then, the inorganic phosphorus or small molecular organic phosphorus is coagulated, flocculated, and precipitated through the physicochemical treatment unit. The physicochemical treatment unit can effectively remove inorganic phosphorus and can also remove small molecular organic phosphorus to a certain extent. Finally, the biological reaction unit only needs to remove a small amount of remaining small molecular organic phosphorus, so as to achieve efficient phosphorus removal treatment of the wastewater containing organic phosphorus and achieve the emission index of total phosphorus. Compared with the physical and chemical method, it solves the problem that organic phosphorus cannot be coagulated, flocculated and settled in large quantities; compared with the biological method, the organic phosphorus wastewater treatment system first converts organic phosphorus into inorganic phosphorus, and then performs physical and chemical treatment to remove most of the phosphorus. The biological reaction unit only needs to process a small amount of small molecule organic phosphorus to achieve a good phosphorus removal effect, solving the problem of low efficiency and difficulty in meeting standards in biological treatment.

[0031] In addition, since the bottom surface of the coagulation zone is higher than the bottom surface of the flocculation zone, there is a height difference between the bottom surfaces of the coagulation zone and the flocculation zone, so that there is a liquid level difference between the coagulation zone and the flocculation zone after feeding, so that the organic phosphorus-containing wastewater can flow from the pipeline at the bottom of the coagulation zone to the flocculation zone. There is a large amount of sedimentation in the organic phosphorus-containing wastewater flowing out of the coagulation zone, and the feed liquid is transported by the liquid level difference, which not only saves transportation energy consumption, but also reduces the accumulation of sedimentation in the coagulation zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the organic phosphorus wastewater treatment system of the utility model;

[0033] Figure 2 It is a structural schematic diagram of the coagulation zone and flocculation zone of the organic phosphorus wastewater treatment system of the utility model;

[0034] Figure 3 It is a partial structural schematic diagram of the sedimentation zone of the organic phosphorus wastewater treatment system of the utility model.

[0035] Among them, 1. regulating tank; 11. acid and alkali reagent inlet; 2. oxidation unit; 21. oxidant inlet; 3. physicochemical treatment unit; 31. coagulation zone; 32. flocculation zone; 33. sedimentation zone; 331. inclined pipe; 332. motor; 333. rotating shaft; 334. mounting frame; 335. scraper; 336. guide plate; 337. mud bucket; 338. mud outlet; 339. reflux port; 34. coagulant inlet; 35. flocculant inlet; 4. biological reaction unit; 41. biochar layer; 42. aeration pipe; 43. backwash air pipe; 5. hardness removal unit; 51. hardness removal agent inlet; 6. stirring device; 7. exhaust pipe; 8. pump. DETAILED DESCRIPTION

[0036] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0037] The embodiment of the utility model provides a system for treating wastewater containing organic phosphorus, such as Figure 1-3 As shown, it includes a regulating tank 1, an oxidation unit 2, a physicochemical treatment unit 3, and a biological reaction unit 4 connected in sequence:

[0038] The regulating tank 1 is provided with an acid and alkali agent inlet 11, which is suitable for adjusting the pH value of the organic phosphorus wastewater; the oxidation unit 2 is provided with an oxidant inlet 21, which is suitable for making the organic phosphorus wastewater react with the oxidant; the physicochemical treatment unit 3 is suitable for making the organic phosphorus wastewater react with the coagulant and the flocculant respectively, and removing the reaction precipitate, including a coagulation zone 31, a flocculation zone 32, and a sedimentation zone 33 connected in sequence; the coagulation zone 31 is provided with a coagulant inlet 34, and the flocculation zone 32 is provided with a flocculant inlet 35, the bottom surface of the coagulation zone 31 is connected to the bottom surface of the flocculation zone 32 through a pipeline, and the bottom surface of the coagulation zone 31 is higher than the bottom surface of the flocculation zone 32; the biological reaction unit 4 is provided with a biochar layer 41, which is suitable for degrading the organic phosphorus wastewater.

[0039] For the purpose of achieving the purpose of the utility model, the reagents added into the acid-base reagent inlet 11, the oxidant inlet 21, the coagulant inlet 34, and the flocculant inlet 35 are not unique, and those skilled in the art can select them according to actual conditions. In this embodiment, the reagents added through the acid-base reagent inlet 11 can be sodium hydroxide, potassium hydroxide, hydrochloric acid, etc., and those skilled in the art can also select other acids or bases according to actual conditions to adjust the pH value of organic phosphorus wastewater. The oxidant added through the oxidant inlet 21 can be substances with oxidation functions such as ozone, hypochlorous acid, sodium hypochlorite, potassium hypochlorite, and calcium hypochlorite, and those skilled in the art can also select other oxidants according to actual conditions. The reagent added through the coagulant inlet 34 can be polyaluminum chloride (PAC), and the reagent added through the flocculant inlet 35 can be polyacrylamide (PAM), and those skilled in the art can also select other coagulants and flocculants according to actual conditions. In addition, the biochar layer 41 is distributed with microorganisms, and the microorganisms can select bacteria with degradation performance to degrade pollutants such as organic phosphorus through synergistic and co-metabolism performance. Those skilled in the art may also select other microorganisms capable of degrading organic phosphorus according to actual conditions, and distribute them in the biochar layer 41 .

[0040] It should be noted that wastewater containing organic phosphorus may have complex components. The wastewater treatment system containing organic phosphorus can achieve a good treatment effect on organic phosphorus, and can also achieve the effects of degrading COD and removing ammonia nitrogen to a certain extent.

[0041] Since phosphorus-containing wastewater may have complex components, in order to prevent calcium ions and magnesium ions in the wastewater from scaling in the physicochemical treatment unit 3 and the biochemical reaction unit 4, especially clogging the biochar layer 41 after scaling in the biochemical reaction unit 4, the organic phosphorus-containing wastewater treatment system also includes a hardness removal unit 5, which is located between the oxidation unit 2 and the physicochemical treatment unit 3.

[0042] As a preferred implementation of this embodiment, the top of the de-hardening unit 5 is provided with a de-hardening agent inlet 51, and a stirring device 6 is provided inside. The de-hardening agent introduced through the de-hardening agent inlet 51 can be sodium hydroxide and sodium carbonate, and the sodium hydroxide and sodium carbonate can form precipitation with calcium ions and magnesium ions to remove calcium ions and magnesium ions. The stirring device 6 can include a stirring paddle, which is powered by a motor to rotate to stir the liquid in the de-hardening unit 5.

[0043] After the acid / alkali solution is added to the regulating tank 1, a pneumatic stirring device is provided at the bottom of the regulating tank 1 to allow the organic phosphorus wastewater to fully react with the acid / alkali solution. Similarly, after the oxidant is added to the oxidation unit 2, a pneumatic stirring device is provided at the bottom of the oxidation unit 2 to allow the organic phosphorus wastewater to fully react with the oxidant. The provision of the pneumatic stirring device can achieve rapid and uniform mixing, increase the reaction rate, and shorten the reaction time.

[0044] The pneumatic stirring device of this embodiment includes an exhaust pipe 7 connected to an air source; the exhaust pipe 7 is provided with an air hole. The pneumatic stirring device delivers gas to the exhaust pipe 7 through an air source (such as a fan), and the gas is discharged from the air hole to achieve stirring of the liquid. Since the acid / alkali solution and the oxidant have a corrosive effect on the stirring device, avoiding the use of a stirring paddle for stirring can greatly save equipment costs and maintenance costs.

[0045] After the coagulant and flocculant are added to the physicochemical treatment unit 3, in order to allow the organic phosphorus-containing wastewater to fully react with the coagulant and flocculant, a stirring device 6 is provided inside the coagulation zone 31 and the flocculation zone 32. The stirring device 6 may include a stirring paddle, which is powered by a motor to rotate to stir the feed liquid.

[0046] The settling area 33 is provided with an inclined pipe 331 and a mud scraping device. The inclined pipe 331 utilizes the shallow sedimentation theory to improve the sedimentation efficiency of the sedimentation tank and shorten the sedimentation time.

[0047] In order to achieve a better scraping effect, the scraping device includes: a motor 332, a rotating shaft 333, a mounting frame 334, a scraping plate 335, a guide plate 336, and a mud bucket 337;

[0048] The motor 332 is located above the sedimentation area 33; the rotating shaft 333 is connected to the output shaft of the motor 332, passes through the inclined tube 331, and is located at the center of the sedimentation area 33; the mounting frame 334 is located at the end of the rotating shaft 333 and at the bottom of the sedimentation area 33; the scraper 335 is fixed on the mounting frame 334 and is parallel to the bottom surface of the sedimentation area 33; the guide plate 336 is located below the rotating shaft 333, one end of which is connected to the scraper 335 and the other end extends downward; the mud bucket 337 is located below the sedimentation area 33, and is in the shape of an inverted truncated cone, suitable for accommodating the guide plate 336.

[0049] To achieve more effective solid-liquid separation, Figure 3 As shown, the mud bucket 337 is provided with a mud discharge port 338 and a return port 339; the return port 339 is located above the mud discharge port 338; the end of the guide plate 336 extends to the return port 339. As a preferred implementation of this embodiment, the return port 339 is connected to the flocculation zone 32 through a pipeline.

[0050] The working process of the scraper device is as follows: after the motor 332 is started, it drives the rotating shaft 333 to rotate, so that the mounting frame 334 connected to the end of the rotating shaft 333 rotates, and then the scraper blade 335 fixed on the mounting frame 334 scrapes the bottom surface of the sedimentation area 33 in a rotating manner to prevent sediment from being deposited on the bottom surface of the sediment 33, and the sediment falls into the mud bucket 337 through the guide plate 336. Since the guide plate 336 rotates with the rotation of the scraper blade 335 and extends to the reflux port 339, it can prevent the sediment from blocking the reflux port 339 and reduce the sediment in the reflux liquid discharged from the reflux port 339. The sediment deposited at the mud discharge port 338 of the mud bucket 337 can be discharged through the pump 8.

[0051] For achieving the purpose of the present invention, the design of the biological reaction unit 4 is not unique, as long as it can provide a container for the reaction between the microorganisms distributed on the biochar layer 41 and the organic phosphorus in the organic phosphorus-containing wastewater. In this embodiment, an aeration pipe 42 and a backwashing air pipe 43 are provided below the biochar layer 41 of the biological reaction unit 4.

[0052] In order to realize the gravity conveying of the slurry of the organic phosphorus wastewater treatment system, the regulating tank 1 is provided with a water inlet at the bottom and a water outlet at the top; the oxidation unit 2 is provided with a water inlet at the top and connected to the water outlet of the regulating tank 1, and the oxidation unit 2 is provided with a water outlet at the bottom; the hardness removal unit 5 is provided with a water inlet at the bottom and connected to the water outlet of the oxidation unit 2, and the hardness removal unit 5 is provided with a water outlet at the top; the coagulation zone 31 is provided with a water inlet at the top and connected to the water outlet of the oxidation unit 2, the coagulation zone 31 is provided with a water outlet at the bottom and connected to the water inlet at the bottom of the flocculation zone 32, the flocculation zone 33 is provided with a water outlet in the middle and connected to the middle water inlet of the sedimentation zone 33; after the organic phosphorus wastewater enters the sedimentation zone 33, the sediment is discharged through the mud hopper 337, and the treated organic phosphorus wastewater flows out through the water outlet at the top, enters the biochemical reaction unit 4, and flows out after biochemical reaction.

[0053] The organic phosphorus wastewater treatment system described in this embodiment has the following working process: after the organic phosphorus wastewater enters the regulating tank 1, acid / alkali solution is added through the acid-base agent inlet 11, and stirred to adjust the pH value of the organic phosphorus wastewater; the organic phosphorus wastewater flowing out of the regulating tank 1 flows into the oxidation unit 2, and oxidant is added through the oxidant inlet 21, and stirred to make the organic phosphorus in the organic phosphorus wastewater react with the oxidant and be converted into inorganic phosphorus and small molecule organic phosphorus; the organic phosphorus wastewater flowing out of the oxidation unit 2 enters the de-hardening unit 5, and de-hardening agent is added through the de-hardening agent inlet 51, and stirred to make the calcium ions and magnesium ions in the organic phosphorus wastewater react with the de-hardening agent and be converted into inorganic phosphorus and small molecule organic phosphorus. into sediment; the organic phosphorus wastewater flowing out of the hardness removal unit 5 enters the physicochemical treatment unit 3, first flows into the coagulation zone 31, adds coagulant through the coagulant inlet 34, and stirs to make the organic phosphorus wastewater react with the coagulant, and then flows into the flocculation zone 32, adds flocculant through the flocculant inlet 35, and stirs to make the organic phosphorus wastewater react with the flocculant. At this time, the inorganic phosphorus and a small amount of small molecular organic phosphorus in the wastewater form sediment after coagulation and flocculation, and then flows into the sedimentation zone 33 for sedimentation, and removes the sediment; the organic phosphorus wastewater flowing out of the sedimentation zone 33 enters the biochemical reaction unit 4, and flows out after being degraded by the microorganisms of the biochar layer 41.

[0054] The above is a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A system for treating wastewater containing organic phosphorus, characterized in that: It comprises a regulating tank (1), an oxidation unit (2), a physicochemical treatment unit (3), and a biological reaction unit (4) which are connected in sequence: The regulating tank (1) is provided with an acid and alkali reagent inlet (11) suitable for regulating the pH value of wastewater containing organic phosphorus; The oxidation unit (2) is provided with an oxidant inlet (21) suitable for reacting the wastewater containing organic phosphorus with the oxidant; The physicochemical treatment unit (3) is suitable for allowing the wastewater containing organic phosphorus to react with a coagulant and a flocculant respectively, and removing the reaction precipitate, and comprises a coagulation zone (31), a flocculation zone (32), and a sedimentation zone (33) connected in sequence; the coagulation zone (31) is provided with a coagulant inlet (34), and the flocculation zone (32) is provided with a flocculant inlet (35); the bottom surface of the coagulation zone (31) is connected to the bottom surface of the flocculation zone (32) through a pipeline, and the bottom surface of the coagulation zone (31) is higher than the bottom surface of the flocculation zone (32); The biological reaction unit (4) is provided with a biochar layer (41) suitable for degrading wastewater containing organic phosphorus.

2. The organic phosphorus wastewater treatment system according to claim 1, characterized in that: It also includes a hardness removal unit (5), which is located between the oxidation unit (2) and the physicochemical treatment unit (3).

3. The organic phosphorus wastewater treatment system according to claim 2, characterized in that: The top of the de-hardening unit (5) is provided with a de-hardening agent input port (51), and a stirring device (6) is provided inside.

4. The organic phosphorus wastewater treatment system according to claim 1, characterized in that: A pneumatic stirring device is provided at the bottom of the regulating tank (1) and / or the oxidation unit (2).

5. The organic phosphorus wastewater treatment system according to claim 4, characterized in that: The pneumatic stirring device comprises an exhaust pipe (7) connected to an air source; the exhaust pipe (7) is provided with air holes.

6. The organic phosphorus wastewater treatment system according to claim 1, characterized in that: A stirring device (6) is provided inside the coagulation zone (31) and / or the flocculation zone (32).

7. The organic phosphorus wastewater treatment system according to claim 1, characterized in that: An inclined pipe (331) and a mud scraping device are provided in the sedimentation area (33).

8. The organic phosphorus wastewater treatment system according to claim 7, characterized in that: The scraper device comprises: A motor (332), wherein the motor (332) is located above the precipitation area (33); A rotating shaft (333), the rotating shaft (333) is connected to the output shaft of the motor (332), passes through the inclined tube (331), and is located at the center of the sedimentation area (33); A mounting frame (334), the mounting frame (334) being located at an end of the rotating shaft (333) and at the bottom of the precipitation area (33); a scraper blade (335), the scraper blade (335) being fixed on the mounting frame (334) and parallel to the bottom surface of the sedimentation area (33); A guide plate (336), the guide plate (336) is located below the rotating shaft (333), one end of the guide plate is connected to the scraper plate (335), and the other end extends downward; A mud bucket (337), the mud bucket (337) is located below the sedimentation area (33), is in the shape of an inverted truncated cone, and is suitable for accommodating the guide plate (336).

9. The organic phosphorus wastewater treatment system according to claim 8, characterized in that: The mud bucket (337) is provided with a mud discharge port (338) and a return port (339); The return port (339) is located above the mud discharge port (338); and the end of the guide plate (336) extends to the return port (339).

10. The organic phosphorus wastewater treatment system according to any one of claims 1 to 9, characterized in that: An aeration pipe (42) and a backwashing pipe (43) are provided below the biochar layer (41) of the biological reaction unit (4).

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