A deep treatment process for pulp mill wastewater

Abstract

The present application provides a kind of pulping wastewater advanced treatment process, which comprises: S100, the pulping wastewater is transported to pretreatment device for pretreatment, and the first-stage treatment water is obtained;S200, the first-stage treatment water is transported to biochemical treatment device for biochemical degradation treatment, and the secondary treatment water is obtained;S300, the secondary treatment water is transported to flocculation device and is treated by flocculation reaction, and the third-stage treatment water is obtained;S400, the third-stage treatment water is transported to fenton reaction device and is treated by fenton reaction, and the discharge standard is reached after treatment.The process can effectively reduce fenton treatment load and reagent usage while achieving pulping wastewater advanced treatment, greatly reducing reagent cost and sludge treatment cost.

Description

Technical Field

[0001] This invention belongs to the field of pulp and paper wastewater treatment technology, specifically relating to a deep treatment process for pulp wastewater. Background Technology

[0002] The pulp and paper industry is one of the most polluting industries, producing large volumes of complex wastewater. Pulping wastewater mainly contains organic and inorganic substances such as lignin, cellulose, hemicellulose, resin, pigments, surfactants, and fillers. Traditional pulping wastewater treatment processes typically involve primary pretreatment, secondary biological treatment, and tertiary Fenton treatment. While this traditional process is relatively simple and has a short treatment cycle, it suffers from extremely high reagent consumption, especially under high production loads, leading to high wastewater treatment costs. Furthermore, this process generates a large amount of sludge, resulting in a heavy workload for sludge treatment, and the presence of reagents in the sludge hinders dewatering and reuse. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a deep treatment process for pulping wastewater. This process can effectively reduce the load of Fenton treatment and the amount of reagents used while achieving deep treatment of pulping wastewater, and greatly reduce the cost of reagents and sludge treatment.

[0004] To achieve the above objectives, the technical effects of this invention are as follows:

[0005] A process for advanced treatment of pulping wastewater includes the following steps:

[0006] S100, the pulping wastewater is transported to the pretreatment unit for pretreatment to obtain primary treated water;

[0007] S200, the primary treated water is transported to a biochemical treatment device for biochemical degradation treatment to obtain secondary treated water;

[0008] S300, the secondary treated water is transported to the flocculation device for flocculation reaction treatment to obtain tertiary treated water;

[0009] S400, the tertiary treated water is transported to the Fenton reactor for Fenton reaction treatment, and discharged after treatment in compliance with standards.

[0010] In one embodiment of this application, in step S300, the secondary treated water is subjected to ultrasonic treatment in the flocculation device and then undergoes natural sedimentation treatment. After natural sedimentation, the upper water body and the lower water body are separated. The upper water body enters the Fenton reaction device; the lower water body reacts with the flocculant, and after the reaction, the sediment is separated and the supernatant enters the Fenton reaction device.

[0011] In one embodiment of the present application, the volume ratio of the upper water body to the lower water body separated after natural sedimentation in step S300 is 1-6:1.

[0012] In one embodiment of the present application, the flocculation device comprises a flocculation reactor and a plurality of separation tanks arranged in parallel; the water inlets of the separation tanks are connected to the water outlet of the biochemical treatment device, the lower water outlets of the separation tanks are connected to the water inlet of the flocculation reactor, and the upper water outlets of the separation tanks and the water outlet of the flocculation reactor are connected to the Fenton reaction device.

[0013] In one embodiment of the present application, the separation tank comprises a vertically arranged tank body, a sloping plate part is arranged in the lower part of the tank body, the water inlet of the separation tank is arranged below the sloping plate part, the lower water outlet is arranged at the bottom of the tank body, the upper water outlet is arranged above the maximum liquid level at the upper part of the tank body, and the upper water outlet is provided with an adjustable drain pipe; the separation tank further comprises an ultrasonic wave emitter arranged on the side wall of the tank body.

[0014] In one embodiment of the present application, step S300 comprises:

[0015] S310, the secondary treated water is transported to a separation tank, water is stopped from being fed to the separation tank when the set liquid level is reached, and water is fed to the next separation tank;

[0016] S320, the separation tank filled with the secondary treated water at the set liquid level is subjected to ultrasonic wave treatment for 5-25 min, and the separation tank is subjected to natural sedimentation for 30-150 min after the ultrasonic wave treatment;

[0017] S330, after natural sedimentation, the upper water body is discharged to the Fenton reaction device, and the lower water body is discharged to the flocculation reactor;

[0018] S340, a flocculating agent is added to the flocculation reactor, the flocculation reaction is stirred, and the water body after separation and flocculation of sludge is discharged to the Fenton reaction device.

[0019] In one embodiment of the present application, the pretreatment device comprises a grid pool, a water collecting pool and an inclined screen arranged in sequence.

[0020] The biochemical treatment device comprises a regulating pool, an aeration pool and a secondary sedimentation tank arranged in sequence, the water inlet end of the regulating pool is connected to the water outlet of the inclined screen, the water outlet end of the secondary sedimentation tank is connected to the water inlets of the separation tanks, and the secondary sedimentation tank and the flocculation reactor are connected to a sludge concentration pool through a sludge pipe.

[0021] In an embodiment of the present application, the secondary sedimentation tank is connected to the water inlet end of the adjusting tank through a sludge return pipe, and the upper water outlet of each separation tank is connected to the water inlet end of the adjusting tank through a backwater pipe.

[0022] In an embodiment of the present application, the flocculation device further comprises a mixing tank, the water inlet end of the mixing tank is connected to the upper water outlet of the separation tank and the water outlet of the flocculation reactor, and the water outlet end of the mixing tank is connected to the water inlet of the Fenton reaction device.

[0023] In an embodiment of the present application, a neutralization tank, a tertiary sedimentation tank and a sand filter tank are sequentially arranged after the Fenton reaction device.

[0024] and / or,

[0025] In step S400, the tertiary treated water is adjusted to neutral pH after Fenton reaction treatment, and is sequentially subjected to gravity sedimentation and sand filter treatment.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The pulp mill wastewater advanced treatment process of the present application, after biochemical treatment and before Fenton treatment, adds a flocculant for flocculation treatment, effectively removes fine suspended solids and colloidal particles in the wastewater (secondary treated water), effectively reduces the turbidity and organic matter content of the wastewater, and reduces the load of subsequent Fenton treatment; the process steps are relatively simple, can realize the advanced treatment of pulp mill wastewater while reducing the load of Fenton treatment, greatly reduces the use amount of reagents (hydrogen peroxide and ferrous sulfate) in the Fenton treatment process, saves reagent cost, effectively reduces the amount of iron sludge (the amount of iron sludge can be reduced by about 40%~75%), reduces the difficulty of sludge treatment, is more conducive to sludge dewatering and secondary utilization of sludge, and the process can meet the advanced treatment requirements of wastewater with larger production load.

[0028] 2. In the pulp mill wastewater advanced treatment process of the present application, the secondary treated water is first subjected to ultrasonic treatment and natural sedimentation treatment for separation in the flocculation device, the upper water body after separation is directly subjected to Fenton treatment, and the lower water body is subjected to flocculation reaction with a flocculant and then enters the Fenton reaction device for Fenton treatment, which can effectively reduce the amount of flocculant, speed up the flocculation treatment time, and at the same time ensure that the water body (tertiary treated water) entering the Fenton reaction device has reduced refractory organic matter, greatly reducing the load of Fenton treatment. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0030] Figure 1 It is a process schematic diagram of the pulp wastewater advanced treatment process of the present application.

[0031] Figure 2 It is a structural schematic diagram of the flocculation device in the present application.

[0032] Figure 3 It is a structural schematic diagram of the separation tank in the present application.

[0033] Reference signs:

[0034] 1, pretreatment device;

[0035] 2, biochemical treatment device;

[0036] 3, flocculation device; 31, separation tank; 311, inclined plate part; 312, ultrasonic wave emitter; 32, flocculation reactor; 33, mixing pool;

[0037] 4, Fenton reaction device. DETAILED DESCRIPTION

[0038] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and description are considered to be exemplary in nature rather than limiting.

[0039] In the description of the present application, it is understood that the terms "vertical", "upper", "lower", "front", "rear", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0040] In the present application, unless specifically defined and limited otherwise, the terms "mounting", "connected", "connecting", "fixed", and the like should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection, and can also be communication; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0041] In the present application, unless specifically defined and limited otherwise, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "under", "below" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0042] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and arrangements of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application.

[0043] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0044] As Figure 1 shown, the embodiment of the present application provides a pulp wastewater advanced treatment process, which is suitable for advanced treatment of wastewater generated in pulp and papermaking. The process comprises the following steps:

[0045] S100, the pulp wastewater to be treated is transported to a pretreatment device 1 for pretreatment, and a first treatment water after pretreatment is obtained. The pretreatment device 1 mainly removes large particle suspended solids, impurities and part of organic matter in the wastewater by physical method, so as to reduce the load of the wastewater and ensure the efficient and normal operation of the subsequent process.

[0046] S200, the first treatment water after pretreatment is transported to a biochemical treatment device 2 for biochemical degradation treatment, under the action of microorganisms, the organic pollutants in the wastewater are degraded, and the second treatment water is obtained after biochemical degradation treatment.

[0047] S300, the secondary treatment water after biochemical treatment is transported to the flocculation device 3, and flocculation reaction treatment is carried out by adding the oxidizing flocculant, and the tertiary treatment water is obtained after treatment. The secondary treatment water and the oxidizing flocculant have flocculation reaction, which can make the fine suspended solids and colloidal particles in the wastewater oxidize and coagulate into larger particles and be separated out, so as to effectively reduce the turbidity and organic matter content of the wastewater, thereby reducing the load of the subsequent Fenton treatment.

[0048] S400, the tertiary treatment water after flocculation reaction treatment is transported to the Fenton reaction device 4 for Fenton reaction treatment, and the treated water is discharged after reaching the standard. The Fenton reagent (hydrogen peroxide and ferrous ion) is added to the wastewater during the Fenton reaction treatment, and the hydroxyl radicals generated by the Fenton reaction oxidize and decompose the refractory organic matter in the water body. The deep treatment of the pulp wastewater can be effectively ensured.

[0049] Preferably, in step S300, the secondary treatment water is first subjected to ultrasonic treatment and then natural sedimentation treatment in the flocculation device 3, and after natural sedimentation, the upper water body and the lower water body are separated. The separated upper water body is directly subjected to Fenton treatment in the Fenton reaction device 4; the lower water body is mixed with the flocculant for flocculation reaction, and after the flocculation reaction, the flocculation sludge is separated and precipitated, and the supernatant is subjected to Fenton treatment in the Fenton reaction device 4.

[0050] By combining ultrasonic treatment and natural sedimentation treatment, the fine suspended solids and colloidal particles in the secondary treatment water can be effectively collided and aggregated, and the sedimentation to the lower water body (lower water body) is accelerated, so that the turbidity of the upper water body (upper water body) is reduced, and the content of fine suspended solids and colloidal particles is extremely low, so that the subsequent Fenton treatment can be directly carried out, which can effectively reduce the load and the amount of reagent used in the Fenton treatment; the lower water body (lower water body) containing fine suspended solids and colloidal particle aggregates is subjected to flocculation reaction with the oxidizing flocculant, which can quickly and efficiently form flocs to remove fine suspended solids and colloidal particles, and obtain water body with low turbidity and low organic matter content, which can effectively reduce the load and the amount of Fenton reagent used in the subsequent Fenton treatment. Moreover, only the lower water body is subjected to flocculation treatment, so the amount of flocculant used is less, and the load of flocculation treatment is lower. The combination of ultrasonic treatment and natural sedimentation can greatly shorten the sedimentation and separation time and improve the separation efficiency.

[0051] Further, in the deep treatment of pulp wastewater, the upper water body and the lower water body are separated after ultrasonic treatment and natural sedimentation treatment, and the volume ratio of the upper water body to the lower water body is preferably controlled to be 1-6:1, and more preferably controlled to be 1.5-3:1, which can better remove the fine suspended solids and colloidal particles in the secondary treatment water, reduce the load of the subsequent Fenton treatment, and at the same time control the amount of the lower water body subjected to flocculation treatment to be relatively small.

[0052] AsFigures 1 to 3 As shown, in one embodiment, the flocculation device 3 includes a flocculation reactor 32 and several parallel-connected separation tanks 31. The inlets of all parallel-connected separation tanks 31 are connected to the outlet of the biochemical treatment device 2, allowing the secondary treated water after biochemical treatment to enter the separation tanks 31. Each parallel-connected separation tank 31 has a lower drain outlet and an upper drain outlet. The lower drain outlets are connected to the inlet of the flocculation reactor 32 to transport the lower water to the flocculation reactor 32. The upper drain outlets of all parallel-connected separation tanks 31 are connected to the inlet of the Fenton reactor 4, and the outlet of the flocculation reactor 32 is also connected to the inlet of the Fenton reactor 4, allowing the upper water and the supernatant after flocculation to be transported to the Fenton reactor 4 for Fenton treatment. The several separation tanks 31 can operate independently or in combination, allowing the system to adapt to different operating loads while ensuring continuous and stable operation.

[0053] like Figure 3 As shown, in a further preferred embodiment, the separation tank 31 includes a vertically arranged tank body. An inclined plate 311 is provided in the lower part of the tank body, dividing the tank body into upper and lower sections. The water inlet of the separation tank 31 is located below the inclined plate 311, i.e., it communicates with the tank body below the inclined plate 311. The lower drain outlet of the separation tank 31 is located at the bottom of the tank body, preferably with an inverted conical bottom, and the lower drain outlet is located in the middle of the inverted conical bottom. The upper drain outlet of the separation tank 31 is located at the upper part of the tank body and is situated above the maximum liquid level position during operation. An adjustable drain pipe is provided inside the upper drain outlet, and the discharge rate of the upper water body can be controlled by adjusting the position of the adjustable drain pipe. An ultrasonic transmitter 312 is provided on the side wall of the separation tank 31, which can emit ultrasonic waves into the tank body of the separation tank 31.

[0054] The inclined plate section 311, with the inlet located below it, can obstruct the flow of secondary treated water entering the tank, preventing suspended solids and impurities from moving upwards and facilitating better separation and sedimentation. The ultrasonic transmitter 312 can treat the water with ultrasound, causing suspended solids and impurities to collide and agglomerate, thus accelerating sedimentation. It can also act on the inclined plate section 311, causing the sediment deposited on the inclined plate section 311 to fall into the lower cavity. In addition, the inclined plate section 311 can also prevent sediment from the lower water from being discharged from the upper part when separating the upper water, making the separation more effective.

[0055] In a preferred embodiment, step S300 specifically includes:

[0056] S310, the secondary treatment water is sequentially delivered to one or more separation tanks 31, and when the liquid level in the one or more separation tanks 31 reaches a set liquid level, the water feeding to the one or more separation tanks 31 is stopped, and the water feeding to the next one or more separation tanks 31 is started.

[0057] S320, the one or more separation tanks 31 filled with the secondary treatment water with the set liquid level are subjected to ultrasonic treatment by starting the ultrasonic transmitter 312, and the ultrasonic treatment is preferably performed for 5-25 minutes; after the ultrasonic treatment, the natural sedimentation is performed for 30-150 minutes, and more preferably for 35-80 minutes, so that the sedimentation and separation effect can be achieved.

[0058] S330, after the natural sedimentation, the upper water body is discharged / extracted from the upper water outlet through the adjustable drain pipe, and is fed to the Fenton reaction device 4 for Fenton treatment; the lower water body is discharged from the lower water outlet to the flocculation reactor 32.

[0059] S340, the flocculant is added to the flocculation reactor 32, and the flocculation reaction is performed by stirring and mixing, and after the flocculation reaction, the flocculation sludge is separated and discharged, and the separated water body (i.e. supernatant) is discharged to the Fenton reaction device 4 for Fenton reaction.

[0060] A plurality of separation tanks 31 are connected in parallel and can be operated respectively or simultaneously, so that the whole system of the separation tanks 31 can simultaneously perform the water feeding operation, ultrasonic treatment, natural sedimentation treatment and water discharge treatment, so that the system can be continuously and stably operated, and can meet different operation loads.

[0061] Further, as shown in Figure 1 The pretreatment device 1 of the pulp mill wastewater advanced treatment process includes a grid pool, a water collecting pool and an inclined screen arranged in sequence. The grid pool and the inclined screen mainly remove large particle suspended solids, impurities and part of organic matters in the wastewater by physical methods, so as to reduce the load of the wastewater. The water collecting pool is arranged to store the wastewater, so as to provide buffering and uniform water quality and quantity, to ensure that the wastewater treatment system can be operated stably, and to avoid the occurrence of overloading, overloading and the like.

[0062] The biochemical treatment device 2 includes a regulating pool, an aeration tank and a secondary sedimentation tank arranged in sequence. The regulating pool is connected with the water outlet end of the inclined screen, and the water outlet end of the secondary sedimentation tank is connected with the water inlet of the plurality of separation tanks 31. The aeration tank is provided with a fan, and the pretreated wastewater enters the aeration tank, and under the action of aerobic bacteria, the organic matters are degraded, and the pollutants such as ammonia nitrogen are effectively removed. The bottom sludge discharge ports of the secondary sedimentation tank and the flocculation reactor 32 are connected to the sludge thickening pool through a sludge pipe, and the sludge generated by the secondary sedimentation tank and the flocculation reactor 32 is collected in the sludge thickening pool, and then anionic polyacrylamide APAM is added for conditioning and dewatering, and the sludge is obtained by plate and frame filter pressing.

[0063] Further, the secondary sedimentation tank is also provided with a sludge return pipe connected to the water inlet end of the adjusting tank to supplement the adjusting tank with activated sludge. The upper drainage port of the separation tank 31 is provided with a backwater pipe connected to the water inlet end of the adjusting tank, so that the water discharged from the upper part of the separation tank 31 can be used to adjust the concentration of the front-end wastewater, so that the adjusting tank can provide relatively stable wastewater for the aeration tank, thereby avoiding the impact of overload on the effect of advanced treatment of wastewater.

[0064] The flocculation device further comprises a mixing tank 33 arranged at the end of the flocculation device 3. The water inlet end of the mixing tank is connected to the upper drainage ports of all the separation tanks 31 and the water outlet of the flocculation reactor 32, and the water outlet end of the mixing tank is connected to the water inlet of the Fenton reaction device 4. That is, the supernatant separated by the separation tank 31 and the water treated by flocculation in the flocculation reactor 32 are mixed in the mixing tank 33 (i.e., the three-stage treated water), and then enter the Fenton reaction device 4 after mixing, so that the water entering the Fenton reaction device 4 has relatively stable water quality, which can effectively avoid the impact of water quality fluctuations on the Fenton treatment effect.

[0065] The Fenton reaction device 4 is further provided with a neutralization tank, a secondary sedimentation tank and a sand filter tank arranged in sequence. The three-stage treated water treated by the flocculation device 3 enters the Fenton reaction device 4 for Fenton reaction treatment, the water treated by Fenton reaction enters the neutralization tank, a neutralizing agent is added to adjust the pH value of the water to neutral, and the water is stirred and degassed; then the water enters the secondary sedimentation tank, and the solid particles such as iron mud in the water are removed by gravity sedimentation, and the iron mud produced by the secondary sedimentation tank is separately treated; finally, the water is filtered by the sand filter tank and discharged or reused.

Claims

1. A deep treatment process for pulping wastewater, characterized in that, Includes the following steps: S100, the pulping wastewater is transported to the pretreatment unit for pretreatment to obtain primary treated water; S200, the primary treated water is transported to a biochemical treatment device for biochemical degradation treatment to obtain secondary treated water; S300, the secondary treated water is transported to the flocculation device for flocculation reaction treatment to obtain tertiary treated water; S400, the tertiary treated water is transported to the Fenton reactor for Fenton reaction treatment, and discharged after treatment to meet the standards; In step S300, the secondary treated water is treated with ultrasound in the flocculation device and then naturally settled. After natural settling, the upper water body and the lower water body are separated. The upper water body enters the Fenton reaction device; the lower water body reacts with the flocculant, and after the reaction, the sediment is separated and the supernatant enters the Fenton reaction device. The flocculation device includes a flocculation reactor and several parallel-connected separation tanks; the inlets of the several separation tanks are all connected to the outlet of the biochemical treatment device, the lower outlets of the several separation tanks are all connected to the inlet of the flocculation reactor, and the upper outlets of the several separation tanks and the outlet of the flocculation reactor are all connected to the Fenton reaction device. The separation tank includes a vertically arranged tank body with an inclined plate in the lower part of the tank body. The water inlet of the separation tank is located below the inclined plate. The lower drain outlet is located at the bottom of the tank body, and the upper drain outlet is located at the upper part of the tank body, above the maximum liquid level. The upper drain outlet is equipped with an adjustable drain pipe. It also includes an ultrasonic transmitter, which is located on the side wall of the tank body. The flocculation device also includes a mixing tank, the inlet of which is connected to the upper drain of the separation tank and the outlet of the flocculation reactor, and the outlet of which is connected to the inlet of the Fenton reaction device.

2. The advanced treatment process for pulping wastewater according to claim 1, characterized in that, In step S300, the volume ratio of the upper water body to the lower water body after natural sedimentation is 1~6:

1.

3. The advanced treatment process for pulping wastewater according to claim 1 or 2, characterized in that, Step S300 includes: S310. The secondary treated water is transported to the separation tank. After the set liquid level is reached, the water supply to the separation tank is stopped, and the water supply to the next separation tank is started. S320. The separation tank containing secondary treated water at a set liquid level is subjected to ultrasonic treatment for 5 to 25 minutes, followed by natural settling for 30 to 150 minutes. S330. After natural settling, the upper water body is discharged to the Fenton reactor and the lower water body is discharged to the flocculation reactor. S340. Add flocculant to the flocculation reactor, stir and flocculate, and discharge the water after separating the flocculated sludge to the Fenton reactor.

4. The advanced treatment process for pulping wastewater according to claim 1 or 2, characterized in that: The pretreatment device includes a bar screen, a water collection tank, and an inclined screen arranged in sequence. The biochemical treatment device includes an equalization tank, an aeration tank, and a secondary sedimentation tank arranged in sequence. The inlet of the equalization tank is connected to the outlet of the inclined screen, and the outlet of the secondary sedimentation tank is connected to the inlet of several separation storage tanks. The secondary sedimentation tank and the flocculation reactor are connected to a sludge thickening tank via sludge pipes.

5. The advanced treatment process for pulping wastewater according to claim 4, characterized in that, The secondary sedimentation tank is equipped with a sludge return pipe connected to the inlet of the equalization tank, and the upper drainage outlets of several of the separation tanks are equipped with return pipes connected to the inlet of the equalization tank.

6. The advanced treatment process for pulping wastewater according to claim 5, characterized in that: It also includes a neutralization tank, a tertiary sedimentation tank, and a sand filter tank, which are arranged sequentially after the Fenton reactor; And / or, In step S400, the tertiary treated water is treated by the Fenton reaction and then the pH of the water body is adjusted to neutral. It is then subjected to gravity sedimentation and sand filtration in sequence.

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