Magnetic coagulation magnetic seed recovery system and method for sewage treatment

Abstract

The invention relates to a magnetic coagulation magnetic seed recovery system for sewage treatment and a method thereof. The recycling system comprises a coagulating basin, a sedimentation basin, a hydrolysis acidification pool, a shearing machine and a magnetic powder separator, an outlet of the coagulating basin is connected into the sedimentation basin through a pipeline, a sedimentation area at the bottom of the sedimentation basin is communicated with the hydrolysis acidification pool through a sludge conveying pump, and a top opening of the sedimentation basin is connected into a subsequent treatment unit through a water pump. A bottom opening of the hydrolysis acidification pool is connected into the shearing machine through a sludge conveying pump, a top opening of the hydrolysis acidification pool is connected into a follow-up treatment unit through a water pump, an outlet of the shearing machine is connected into the magnetic powder separator through the sludge conveying pump, and a magnetic seed outlet of the magnetic powder separator is connected into the coagulation pool through a water pump. A sludge outlet of the magnetic powder separator is connected with a sludge branch and a carbon source recovery branch, the sludge branch is connected to a sludge treatment unit through a sludge conveying pump, and the carbon source recovery branch is connected to a subsequent treatment unit through a sludge conveying pump. The recovery system can realize efficient recovery of magnetic seeds and reduce energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a magnetic coagulation magnetic seed recovery system for sewage treatment, and a magnetic coagulation magnetic seed recovery method for sewage treatment using the system. Background Art

[0002] Magnetic enhanced separation technology is an innovative development based on traditional coagulation and sedimentation technology. It forms high-density flocs with magnetic properties by adding recyclable magnetic seeds during the chemical flocculation reaction, and quickly separates them from water by gravity sedimentation or external magnetic field, greatly shortening the treatment cycle, thereby greatly improving the treatment capacity per unit area and the effluent quality. Therefore, magnetic enhanced separation technology has been widely used in sewage treatment plant upgrading and overflow pollution control projects.

[0003] The recycling of magnetic seeds is the key to ensuring the treatment efficiency of magnetic enhanced separation technology. Currently, the high-speed operation of the shearing machine is mainly used to break up the magnetic seed sludge, achieve the crushing and deflocculence of the magnetic flocs, and then the magnetic seeds and sludge are separated by a magnetic powder separator. The separated magnetic seeds enter the coagulation tank for recycling, and the sludge enters the subsequent disposal process.

[0004] However, the sludge containing magnetic seeds causes serious wear and tear on shearing machines, sludge conveying pumps and other equipment, which increases the equipment maintenance cost. In addition, the use of shearing machines to break up the sludge containing magnetic seeds not only leads to high energy consumption of the shearing machines, but also has a poor breaking effect and is prone to magnetic seed loss. Especially when magnetic enhanced separation technology is used for biofilm process effluent, the magnetic seed recovery rate is low due to the tight binding of magnetic flocculants. At the same time, magnetic coagulation sludge contains certain organic matter, which can provide a carbon source for subsequent treatment links, but the influent concentration of some sewage treatment plants is low, and the internal carbon source is insufficiently utilized. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a magnetic coagulation magnetic seed recovery system for sewage treatment, which can achieve efficient recovery of magnetic seeds and reduce energy consumption.

[0006] The present invention adopts the following technical solution:

[0007] The invention provides a magnetic coagulation and magnetic seed recovery system for sewage treatment, comprising a coagulation tank, a sedimentation tank, a hydrolysis acidification tank, a shearing machine and a magnetic powder separator, wherein the outlet of the coagulation tank is connected to the sedimentation tank through a pipeline, the sedimentation area at the bottom of the sedimentation tank is connected to the hydrolysis acidification tank through a sludge conveying pump, the top opening of the sedimentation tank is connected to a subsequent treatment unit through a water pump, the bottom opening of the hydrolysis acidification tank is connected to the shearing machine through a sludge conveying pump, the top opening of the hydrolysis acidification tank is connected to the subsequent treatment unit through a water pump, the outlet of the shearing machine is connected to the magnetic powder separator through the sludge conveying pump, the magnetic seed outlet of the magnetic powder separator is connected to the coagulation tank through the water pump, the sludge outlet of the magnetic powder separator is connected to a sludge branch and a carbon source recovery branch, the sludge branch is connected to the sludge treatment unit through the sludge conveying pump, and the carbon source recovery branch is connected to the subsequent treatment unit through the sludge conveying pump.

[0008] Preferably, the ratio of the inner diameter of the hydrolysis acidification tank to the tank depth is 1:1.5 to 1:2, the rotation speed of the stirring device at the top of the hydrolysis acidification tank is 60 to 600 r / min, and the sludge concentration entering the hydrolysis acidification tank is 10 g / L to 20 g / L.

[0009] Preferably, the hydrolysis acidification tank is an anaerobic hydrolysis acidification tank.

[0010] Preferably, the magnetic powder separator includes a magnetic drum, a guide plate, a rubber pressure roller, a reduction motor, a scraper and a shell. The guide plate, the rubber pressure roller, the reduction motor and the scraper are all arranged in the shell. One end of the guide plate is located at the inlet of the shell, and the other end extends obliquely downward to the lower half of the magnetic drum. The rubber pressure roller is arranged close to the upper half of the magnetic drum, and the roller axis of the rubber pressure roller is parallel to the roller axis of the magnetic drum. The reduction motor drives the magnetic drum and the rubber pressure roller to rotate synchronously, and the rotation direction of the rubber pressure roller is opposite to the rotation direction of the magnetic drum. One end of the scraper is located at the upper half of the magnetic drum, and the other end extends obliquely downward to the magnetic seed outlet of the shell. The sludge outlet of the shell is located directly below the magnetic drum.

[0011] Preferably, a wetting water pool is installed just below the magnetic seed outlet of the shell, and the wetting water pool is connected to the coagulation tank through a water pump.

[0012] Preferably, the magnetic field strength of the magnetic drum is 3000-5000 Gs, and the rotation speed of the magnetic drum is 60-120 rad / min.

[0013] Preferably, three coagulation tanks are arranged in succession, the frontmost coagulation tank is connected to the middle coagulation tank through the top outlet, the middle coagulation tank is connected to the endmost coagulation tank through the bottom outlet, the endmost coagulation tank is connected to the sedimentation tank through a pipeline, and the magnetic seed outlet of the magnetic powder separator is connected to the middle coagulation tank through a water pump.

[0014] The present invention also provides a method for recovering magnetic seeds by magnetic coagulation for sewage treatment, which adopts any of the above-mentioned magnetic coagulation magnetic seeds recovery systems for sewage treatment and comprises the following steps:

[0015] S1: The magnetic seed sludge in the sedimentation area at the bottom of the sedimentation tank is fed into the hydrolysis acidification tank through a sludge delivery pump, so that the magnetic floccules are initially broken and initially deflocculed in the hydrolysis acidification tank, and the organic matter in the magnetic floccules is decomposed at the same time, so as to facilitate the use of microorganisms in the subsequent treatment unit;

[0016] S2: The magnetic seed sludge at the bottom of the hydrolysis and acidification tank is fed into the shearing machine through the sludge delivery pump, so that the magnetic floccules are further broken and deflocculated under the rotation of the shearing machine, and the supernatant in the hydrolysis and acidification tank is connected to the subsequent treatment unit through the water pump;

[0017] S3: The magnetic seed sludge in the shearing machine is input into the magnetic powder separator through the sludge conveying pump to separate the magnetic powder from the sludge. The separated magnetic powder is discharged through the magnetic seed outlet and returned to the coagulation tank through the water pump. The separated sludge is discharged through the sludge outlet, and part of the sludge enters the sludge branch and is discharged into the sludge treatment unit through the sludge conveying pump to wait for subsequent treatment, and the other part of the sludge enters the carbon source recovery branch as a supplementary carbon source and is input into the subsequent treatment unit through the sludge conveying pump.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The magnetic coagulation magnetic seed recovery system for sewage treatment of the present invention continuously arranges a hydrolysis acidification tank, a shearing machine and a magnetic powder separator after the sedimentation tank, so that the hydrolysis bacteria and acidification bacteria in the hydrolysis acidification tank can perform preliminary crushing and deflocculation on the magnetic floccules, and then enter the shearing machine for secondary crushing and deflocculation of the magnetic floccules, and finally the magnetic powder separator separates the magnetic seeds from the sludge, and the separated magnetic seeds re-enter the coagulation tank for recycling. Since the hydrolysis acidification tank and the shearing machine can both crush and deflocculate the magnetic floccules during the whole process, the efficient recovery of the magnetic seeds is achieved; and the shearing machine is only used for secondary crushing and deflocculation of the magnetic floccules, which can also reduce the energy consumption of the shearing machine.

[0020] The magnetic coagulation magnetic seed recovery method for sewage treatment of the present invention utilizes the above-mentioned magnetic coagulation magnetic seed recovery system for sewage treatment, which can not only improve the efficient recovery of magnetic seeds and reduce the energy consumption of the shearing machine through the combined action of the hydrolysis acidification tank and the shearing machine, but also decompose the organic matter in the magnetic flocculent body into small molecular organic matter that is easy for subsequent microorganisms to utilize, thereby improving the utilization efficiency of the carbon source in the sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of a magnetic coagulation and magnetic seed recovery system for sewage treatment in an embodiment of the present invention.

[0022] The reference numerals are described as follows:

[0023] 1. Coagulation tank

[0024] 2. Sedimentation tank

[0025] 3. Hydrolysis acidification tank

[0026] 4. Shearing machine

[0027] 5. Magnetic Powder Separator

[0028] 6. Sludge branch

[0029] 7. Carbon source recovery branch DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions 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 orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0034] See also Figure 1The present embodiment provides a magnetic coagulation and magnetic seed recovery system for sewage treatment, comprising a coagulation tank 1, a sedimentation tank 2, a hydrolysis and acidification tank 3, a shearing machine 4 and a magnetic powder separator 5. The outlet of the coagulation tank 1 is connected to the sedimentation tank 2 through a pipeline, and the sedimentation area at the bottom of the sedimentation tank 2 is connected to the hydrolysis and acidification tank 3 through a sludge conveying pump. The top opening of the sedimentation tank 2 is connected to a subsequent treatment unit through a water pump, and the bottom opening of the hydrolysis and acidification tank 3 is connected to the shearing machine 4 through a sludge conveying pump. The top opening of the hydrolysis and acidification tank 3 is connected to the subsequent treatment unit through a water pump, and the outlet of the shearing machine 4 is connected to the magnetic powder separator 5 through a sludge conveying pump. The magnetic seed outlet of the magnetic powder separator 5 is connected to the coagulation tank 1 through a water pump. The sludge outlet of the magnetic powder separator 5 is connected to a sludge branch 6 and a carbon source recovery branch 7. The sludge branch 6 is connected to the sludge treatment unit through a sludge conveying pump, and the carbon source recovery branch 7 is connected to the subsequent treatment unit through a sludge conveying pump.

[0035] The magnetic coagulation magnetic seed recovery system for sewage treatment of this embodiment is configured by continuously arranging a hydrolysis acidification tank 3, a shearing machine 4 and a magnetic powder separator 5 after the sedimentation tank 2, so that the hydrolysis bacteria and acidification bacteria in the hydrolysis acidification tank 3 can perform preliminary crushing and deflocculation on the magnetic floccules, and then enter the shearing machine 4 for secondary crushing and deflocculation of the magnetic floccules, and finally the magnetic powder separator 5 separates the magnetic seeds from the sludge, and the separated magnetic seeds re-enter the coagulation tank 1 for recycling. Since the hydrolysis acidification tank 3 and the shearing machine 4 can both crush and deflocculate the magnetic floccules during the whole process, the efficient recovery of the magnetic seeds is achieved; and the shearing machine 4 is only used for secondary crushing and deflocculation of the magnetic floccules, which can also reduce the energy consumption of the shearing machine 4.

[0036] In addition, by connecting the sludge branch 6 and the carbon source recovery branch 7 at the sludge outlet of the magnetic powder separator 5, a part of the sludge can be recovered as a carbon source through the carbon source recovery branch 7, and the remaining sludge is discharged to the sludge treatment unit.

[0037] It should be noted that the magnetic coagulation and magnetic seed recovery system for sewage treatment in this embodiment is built on the basis of the original sewage treatment system. In the original sewage treatment system, the inlet of the coagulation tank 1 is connected to the sewage, and the outlet is connected to the sedimentation tank 2 through a pipeline, and a coagulant is added to the coagulation tank 1. After the sewage with the coagulant enters the sedimentation tank 2, the magnetic flocculants and sludge are deposited in the sedimentation area at the bottom of the sedimentation tank 2, and the purified sewage is connected to the subsequent treatment unit through a water pump from the top opening of the sedimentation tank 2.

[0038] Preferably, in this embodiment, the outlet of the coagulation tank 1 is connected to a water distributor located in the sedimentation tank 2 through a pipeline.

[0039] Preferably, the ratio of the inner diameter of the hydrolysis acidification tank 3 to the depth of the tank body is 1:1.5 to 1:2, the rotation speed of the stirring device at the top of the tank inlet of the hydrolysis acidification tank 3 is 60 to 600 r / min, and the concentration of the sludge introduced into the hydrolysis acidification tank 3 is 10 g / L to 20 g / L. The stirring device at the top of the tank inlet of the hydrolysis acidification tank 3 is used to mix the sludge in the hydrolysis acidification tank 3, and the ratio of the inner diameter of the hydrolysis acidification tank 3 to the depth of the tank body, the rotation speed of the stirring device at the top of the tank inlet of the hydrolysis acidification tank 3, and the concentration of the sludge introduced into the hydrolysis acidification tank 3 adopt the above parameters, which is conducive to ensuring the crushing and deflocculation effect of the magnetic flocculants in the hydrolysis acidification tank 3.

[0040] Preferably, the hydrolysis and acidification tank 3 is an anaerobic hydrolysis and acidification tank, so that the presence of magnetic powder in the magnetic flocculant can promote the anaerobic hydrolysis and acidification of the sludge, further utilize the carbon source in the sewage, and reduce the amount of external carbon source added; at the same time, it can also inhibit the gas production stage of sludge digestion, avoid carbon source loss, and improve the recovery efficiency of internal carbon source.

[0041] Preferably, the magnetic powder separator 5 includes a magnetic drum, a guide plate, a rubber pressure roller, a reduction motor, a scraper and a shell. The guide plate, the rubber pressure roller, the reduction motor and the scraper are all arranged in the shell. One end of the guide plate is located at the inlet of the shell, and the other end extends obliquely downward to the lower half of the magnetic drum. The rubber pressure roller is arranged close to the upper half of the magnetic drum, and the roller axis of the rubber pressure roller is parallel to the roller axis of the magnetic drum. The reduction motor drives the magnetic drum and the rubber pressure roller to rotate synchronously, and the rotation direction of the rubber pressure roller is opposite to the rotation direction of the magnetic drum. One end of the scraper is located at the upper half of the magnetic drum, and the other end extends obliquely downward to the magnetic seed outlet of the shell. The sludge outlet of the shell is located directly below the magnetic drum.

[0042] The sludge containing magnetic seeds enters the inlet of the upper shell of the magnetic powder separator 5 from the shearing machine 4 after being transported by the sludge transport pump. The sludge entering the shell is drained to the magnetic drum through the guide plate. The magnetic drum continuously absorbs magnetic powder from the sludge while rotating, and the rubber pressure roller is used to squeeze out the moisture of the magnetic powder absorbed on the magnetic drum. The magnetic powder with moisture squeezed out contacts the scraper as the magnetic drum rotates, and then the magnetic powder absorbed on the outer peripheral surface of the magnetic drum is scraped off by the scraper, and the scraped magnetic powder is discharged from the magnetic seed outlet of the shell.

[0043] Preferably, a wetting water pool is installed just below the magnetic seed outlet of the shell, and the wetting water pool is connected to the coagulation tank 1 through a water pump. The magnetic powder discharged from the magnetic seed outlet of the shell falls into the wetting water pool and mixes with the clean water in the wetting water pool, and then the separated magnetic powder is returned to the coagulation tank 1 through the water pump.

[0044] Preferably, the magnetic field strength of the magnetic drum is 3000-5000 Gs, and the rotation speed of the magnetic drum is 60-120 rad / min, so as to ensure the magnetic seed recovery amount and recovery efficiency of the magnetic powder separator 5 .

[0045] Preferably, see Figure 1 There are three coagulation tanks 1 arranged in succession, the frontmost coagulation tank 1 is connected to the middle coagulation tank 1 through the top outlet, the middle coagulation tank 1 is connected to the endmost coagulation tank 1 through the bottom outlet, the endmost coagulation tank 1 is connected to the sedimentation tank 2 through a pipeline, and the magnetic seed outlet of the magnetic powder separator 5 is connected to the middle coagulation tank 1 through a water pump, thereby ensuring the magnetically enhanced separation effect of the magnetic powder.

[0046] This embodiment also provides a method for recovering magnetic seeds by magnetic coagulation for sewage treatment. Figure 1 , using the above-mentioned magnetic coagulation magnetic seed recovery system for sewage treatment, and including the following steps:

[0047] S1: The magnetic seed sludge in the sedimentation area at the bottom of the sedimentation tank 2 is fed into the hydrolysis acidification tank 3 through a sludge delivery pump, so that the magnetic flocs are initially broken and initially deflocculed in the hydrolysis acidification tank 3, and the organic matter in the magnetic flocs is decomposed at the same time, so as to facilitate the use of microorganisms in the subsequent treatment unit;

[0048] S2: The magnetic seed sludge at the bottom of the hydrolysis and acidification tank 3 is fed into the shearing machine 4 through the sludge delivery pump, so that the magnetic floccules are further broken and deflocculated under the rotation of the shearing machine 4, and the supernatant in the hydrolysis and acidification tank 3 is connected to the subsequent treatment unit through the water pump;

[0049] S3: The magnetic seed sludge in the shearing machine 4 is input into the magnetic powder separator 5 through the sludge conveying pump to separate the magnetic powder from the sludge. The separated magnetic powder is discharged through the magnetic seed outlet and returned to the coagulation tank 1 through the water pump. The separated sludge is discharged through the sludge outlet, and part of the sludge enters the sludge branch 6 and is discharged into the sludge treatment unit through the sludge conveying pump to wait for subsequent treatment, and the other part of the sludge enters the carbon source recovery branch 7 as a supplementary carbon source and is input into the subsequent treatment unit through the sludge conveying pump.

[0050] The magnetic coagulation magnetic seed recovery method for sewage treatment of this embodiment utilizes the above-mentioned magnetic coagulation magnetic seed recovery system for sewage treatment, which can not only improve the efficient recovery of magnetic seeds and reduce the energy consumption of the shearing machine 4 through the combined action of the hydrolysis acidification tank 3 and the shearing machine 4, but also decompose the organic matter in the magnetic flocculent body into small molecular organic matter that is easy for subsequent microorganisms to utilize, thereby improving the utilization efficiency of carbon sources in sewage.

[0051] The following are two specific examples of municipal sewage treatment using the above-mentioned magnetic coagulation and magnetic seed recovery method:

[0052] Embodiment 1

[0053] The sewage to be treated is municipal sewage from a certain area in the north. The conventional water quality indicators are: COD (chemical oxygen demand) = 200-300 mg / L, SS (suspended solids) concentration is 180-230 mg / L, NH4 + -N (ammonia nitrogen) concentration is 30-50 mg / L, TN (total nitrogen) concentration is 40-60 mg / L, and TP (total phosphorus) concentration is 3-7 mg / L.

[0054] When the conventional magnetic enhanced separation-mud membrane composite process (this process is still the combined separation of the shearing machine and the magnetic powder separator in the background technology) is used to treat the original sewage treatment system, the effluent COD of the magnetic powder separator is 126±25 mg / L, the magnetic seed recovery rate is 75%, and the shearing machine speed is 300r / min; after adopting the above-mentioned magnetic coagulation and magnetic seed recovery method for sewage treatment, the SRT (average residence time of sludge in the system) is 3d, the effluent COD of the supernatant of the hydrolysis acidification tank is 400±35 mg / L, the shearing machine speed is 260r / min, and the magnetic seed recovery rate is 85%.

[0055] Obviously, compared with the conventional magnetic enhanced separation-mud membrane composite process, the magnetic coagulation and magnetic seed recovery method for sewage treatment of this embodiment can better achieve the standard treatment of municipal sewage in a certain northern region, and the shearing machine has low energy consumption and high magnetic seed recovery rate.

[0056] Embodiment 2

[0057] The sewage to be treated is municipal sewage from a certain area in the south. The conventional water quality indicators are: COD (chemical oxygen demand) = 200-300 mg / L, SS (suspended solids) concentration is 120-180 mg / L, NH4 + -N (ammonia nitrogen) concentration is 20-35 mg / L, TN (total nitrogen) concentration is 40-50 mg / L, and TP (total phosphorus) concentration is 4-8 mg / L.

[0058] When the conventional pure membrane MBBR-magnetic coagulation sedimentation process (this process is still the coordinated separation of the shearing machine and the magnetic particle separator in the background technology) is used to treat the original sewage treatment system, the effluent COD of the magnetic particle separator is 40±4 mg / L, the magnetic seed recovery rate is 80%, and the shearing machine speed is 300r / min; after adopting the above-mentioned magnetic coagulation magnetic seed recovery method for sewage treatment, the SRT (average residence time of sludge in the system) is 3d, the effluent COD of the supernatant of the hydrolysis acidification tank is 350±35 mg / L, the shearing machine speed is 250r / min, and the magnetic seed recovery rate is 86%.

[0059] Obviously, compared with the conventional pure membrane MBBR-magnetic coagulation sedimentation process, the magnetic coagulation magnetic seed recovery method for sewage treatment in this embodiment can better achieve the standard treatment of municipal sewage in a certain area in the south, and the shearing machine has low energy consumption and high magnetic seed recovery rate.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A magnetic coagulation and magnetic seed recovery system for sewage treatment, characterized in that: The invention comprises a coagulation tank (1), a sedimentation tank (2), a hydrolysis acidification tank (3), a shearing machine (4) and a magnetic powder separator (5), wherein the outlet of the coagulation tank (1) is connected to the sedimentation tank (2) through a pipeline, the sedimentation area at the bottom of the sedimentation tank (2) is connected to the hydrolysis acidification tank (3) through a sludge delivery pump, the top opening of the sedimentation tank (2) is connected to a subsequent treatment unit through a water pump, the bottom opening of the hydrolysis acidification tank (3) is connected to the shearing machine (4) through a sludge delivery pump, and the hydrolysis acidification tank (5) is connected to the shearing machine (4) through a sludge delivery pump. 3) is connected to a subsequent treatment unit through a water pump, the outlet of the shearing machine (4) is connected to the magnetic powder separator (5) through a sludge conveying pump, the magnetic seed outlet of the magnetic powder separator (5) is connected to the coagulation tank (1) through a water pump, the sludge outlet of the magnetic powder separator (5) is connected to a sludge branch (6) and a carbon source recovery branch (7), the sludge branch (6) is connected to the sludge treatment unit through a sludge conveying pump, and the carbon source recovery branch (7) is connected to the subsequent treatment unit through a sludge conveying pump.

2. The magnetic coagulation and magnetic seed recovery system for sewage treatment according to claim 1, characterized in that: The ratio of the inner diameter of the hydrolysis acidification tank (3) to the depth of the tank is 1:1.5 to 1:2, the rotation speed of the stirring device at the top of the hydrolysis acidification tank (3) is 60 to 600 r / min, and the concentration of the sludge introduced into the hydrolysis acidification tank (3) is 10 g / L to 20 g / L.

3. The magnetic coagulation and magnetic seed recovery system for sewage treatment according to claim 1, characterized in that: The hydrolysis acidification tank (3) is an anaerobic hydrolysis acidification tank.

4. The magnetic coagulation and magnetic seed recovery system for sewage treatment according to claim 1, characterized in that: The magnetic powder separator (5) comprises a magnetic drum, a guide plate, a rubber pressure roller, a reduction motor, a scraper and a shell. The guide plate, the rubber pressure roller, the reduction motor and the scraper are all arranged in the shell. One end of the guide plate is located at the inlet of the shell, and the other end extends downwardly at an angle to the lower half of the magnetic drum. The rubber pressure roller is arranged close to the upper half of the magnetic drum, and the roller axis of the rubber pressure roller is parallel to the roller axis of the magnetic drum. The reduction motor drives the magnetic drum and the rubber pressure roller to rotate synchronously, and the rotation direction of the rubber pressure roller is opposite to the rotation direction of the magnetic drum. One end of the scraper is located at the upper half of the magnetic drum, and the other end extends downwardly at an angle to the magnetic seed outlet of the shell. The sludge outlet of the shell is located directly below the magnetic drum.

5. The magnetic coagulation and magnetic seed recovery system for sewage treatment according to claim 4, characterized in that: A wetting water pool is installed directly below the magnetic seed outlet of the shell, and the wetting water pool is connected to the coagulation tank (1) through a water pump.

6. The magnetic coagulation and magnetic seed recovery system for sewage treatment according to claim 4, characterized in that: The magnetic field strength of the magnetic drum is 3000-5000 Gs, and the rotation speed of the magnetic drum is 60-120 rad / min.

7. The magnetic coagulation and magnetic seed recovery system for sewage treatment according to claim 1, characterized in that: The coagulation tanks (1) are arranged in three consecutive parts, the frontmost coagulation tank (1) is connected to the middle coagulation tank (1) via the top outlet, the middle coagulation tank (1) is connected to the rearmost coagulation tank (1) via the bottom outlet, the rearmost coagulation tank (1) is connected to the sedimentation tank (2) via a pipeline, and the magnetic seed outlet of the magnetic powder separator (5) is connected to the middle coagulation tank (1) via a water pump.

8. A method for recovering magnetic seeds by magnetic coagulation for sewage treatment, characterized in that: The magnetic coagulation and magnetic seed recovery system for sewage treatment according to any one of claims 1 to 7 is used, and comprises the following steps: S1: The magnetic seed sludge in the sedimentation area at the bottom of the sedimentation tank (2) is fed into the hydrolysis acidification tank (3) by a sludge delivery pump, so that the magnetic floccules are initially broken and initially deflocculed in the hydrolysis acidification tank (3), and the organic matter in the magnetic floccules is decomposed at the same time, so as to facilitate the use of microorganisms in the subsequent treatment unit; S2: The magnetic seed sludge at the bottom of the hydrolysis and acidification tank (3) is fed into the shearing machine (4) through a sludge delivery pump, so that the magnetic floccules are further broken and deflocculated under the rotation of the shearing machine (4), and the supernatant in the hydrolysis and acidification tank (3) is connected to a subsequent treatment unit through a water pump; S3: The magnetic seed sludge in the shearing machine (4) is input into the magnetic powder separator (5) through a sludge conveying pump, so that the magnetic powder is separated from the sludge. The separated magnetic powder is discharged through the magnetic seed outlet and returned to the coagulation tank (1) through a water pump. The separated sludge is discharged through the sludge outlet, and a part of the sludge enters the sludge branch (6) and is discharged into the sludge treatment unit through a sludge conveying pump to wait for subsequent treatment, while the other part of the sludge enters the carbon source recovery branch (7) as a supplementary carbon source and is input into the subsequent treatment unit through a sludge conveying pump.

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