Preparation method and application of water body sediment-based filler

Abstract

The present application relates to a kind of water body bottom mud base filler preparation method and application, belong to water environment remediation field.The preparation method includes the following steps: first, the dredged mud with high water content is dried, grinded and then passed through 100 mesh screen;Second, the mud obtained by the first step, zeolite powder, starch are proportionally stirred and mixed uniformly, while adding distilled water and stirring, until a certain viscosity and no flowability mud ball is stopped;Third, the mud ball is taken out and placed in mud pellet machine, and spherical ceramsite sample with uniform particles is made, and the weight of each sample is controlled to be 10±0.2 g;Fourth, the sample is placed in oven and dried;Then placed in muffle furnace and calcined at high temperature to obtain water body bottom mud base filler.The present application can realize the resource utilization of water body bottom mud, effectively replace the natural filler of artificial wetland, promote the further removal of pollutants in sewage plant, and provide a useful reference for the preparation of water body bottom mud base filler and its application in artificial wetland for treating tail water of sewage plant.

Description

Technical Field

[0001] This invention belongs to the field of water environment restoration and management, specifically relating to a method for preparing sediment-based filler material for water bodies and its application in the treatment of wastewater effluent from constructed wetlands. Background Technology

[0002] River and lake sediments are an important component of river and lake ecosystems. Nitrogen, phosphorus, heavy metals, and organic pollutants migrate repeatedly between the sediment and the overlying water. The release of sediment pollutants into the overlying water through endogenous sources is a significant cause of water quality deterioration and recurring black and odorous conditions. Therefore, the remediation of river and lake sediments has become a key challenge in urban water environment management. Even after external pollution sources in rivers are controlled, sediment pollution in black and odorous water bodies becomes a limiting factor for water quality. Sediment dredging technology directly removes riverbed sediment by dredging, eliminating endogenous pollution in the water and preventing the migration of sediment pollutants into the water body.

[0003] River and lake dredging generates a large amount of sediment. Stabilizing, rendering harmless, and reducing the volume of dredged sediment for resource utilization has become a trend. When dredged sediment has a high organic matter content and low salt content, it is suitable for application to agricultural land after simple modification. When the organic matter content of dredged sediment is low, it can be used to produce bricks and tiles using a non-fired process. For sediment heavily polluted with toxic organic matter and heavy metals, it can be dried, modified with the addition of concrete materials, and then used as backfill for road filling. Summary of the Invention

[0004] To reduce the environmental risks associated with the application of aquatic sediment materials and improve the resource recycling rate of sediment, this invention innovatively proposes a method for preparing aquatic sediment-based filler and its application in constructed wetlands for treating wastewater effluent. This invention achieves the goals of resource utilization of aquatic sediment, effectively replacing natural fillers in constructed wetlands, and promoting further removal of pollutants from wastewater treatment plants, providing a valuable reference for the preparation of aquatic sediment-based fillers and their application in constructed wetlands for treating wastewater effluent.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a sediment-based filler for aquatic bodies includes the following steps:

[0007] The first step is to place the dredged sediment with high water content in a 105℃ oven for 24 hours. After drying, the sediment will have a blocky structure. Remove the impurities, grind it in a mortar and pestle, and then pass it through a 100-mesh sieve.

[0008] The second step is to mix the bottom mud, zeolite powder, and starch obtained in the first step in a certain proportion, while adding distilled water and stirring until the mixture has a certain viscosity and no fluidity.

[0009] The third step is to take out the mud ball and put it into a mud pellet making machine to make spherical ceramic pellet samples with uniform particle size, and control the weight of each sample to be 10±0.2 g.

[0010] The fourth step is to place the sample in an oven and dry it at 105℃ for 2 hours; then place the dried sample in a muffle furnace for high-temperature calcination to obtain the bottom sediment-based filler.

[0011] In the above scheme, the water content of the bottom sediment in the first step is 69.75-93.34%.

[0012] In the above scheme, the mass ratio of bottom mud, zeolite powder and starch in the second step is 1:0-1:0.075-0.15.

[0013] In the above scheme, the mass ratio of bottom mud, zeolite powder, and starch in the second step is 1:1:0.15, 1:0.667:0.125, 1:0.429:0.107, 1:0.25:0.094, 1:0.087:0.083, or 1:0:0.075.

[0014] In the above scheme, the heating procedure for the fourth step of high-temperature roasting is as follows: heating rate 7℃ / min, from room temperature to 400℃, holding at 400℃ for 20min; continue heating to 800-900℃, holding for 30min.

[0015] In the above scheme, the sample prepared in the third step contains a large amount of moisture. If it is directly placed into the muffle furnace for firing, the moisture inside the sphere will evaporate, causing the surface of the sphere to crack and disintegrate. Therefore, it is necessary to dry it before firing.

[0016] In the above scheme, sediment and zeolite powder serve as the solid components of the novel filler. Starch, after high-temperature calcination, vaporizes inside the filler to form pores. The material ratio used in this invention achieves the maximum specific surface area of ​​the novel filler. The filler prepared by the above method has a maximum specific surface area and total pore volume of 8.98 m². 2 / g, 0.05cm 3 / g.

[0017] An application of a sediment-based filler material for treating wastewater effluent from a constructed wetland includes the following steps:

[0018] (1) Construct a two-stage vertical flow constructed wetland of aeration nitrification and denitrification;

[0019] (2) Start the two-stage vertical flow constructed wetland of aeration nitrification-denitrification, and use the sludge from the secondary sedimentation tank of the sewage treatment plant for microbial biofilm formation;

[0020] (3) The wastewater effluent from the wastewater treatment plant is pumped into the two-stage vertical flow constructed wetland of aeration nitrification and denitrification. At the same time, the aeration pump is turned on to provide oxygen to the aeration nitrification vertical flow wetland unit through the aeration disc. After being treated by the aeration nitrification vertical flow wetland unit, the wastewater effluent from the wastewater treatment plant enters the intermediate water tank, and then enters the denitrification vertical flow constructed wetland through the inlet pump. Finally, it is discharged after treatment.

[0021] In the above scheme, the two-stage vertical flow constructed wetland of aeration nitrification-denitrification in step (1) includes an aeration nitrification vertical flow wetland unit and a denitrification vertical flow constructed wetland unit. The bottom of the aeration nitrification vertical flow wetland unit is connected to an inlet tank through an inlet pump. An aeration disc is set at the bottom of the aeration nitrification vertical flow wetland unit. The aeration disc is connected to an aeration pump. Above the aeration disc, a support tray, a volcanic rock layer, a packing layer, a quartz sand layer, and aquatic plants are arranged in sequence. The outlet of the quartz sand layer in the aeration nitrification vertical flow wetland unit transports water to the denitrification vertical flow constructed wetland unit through an intermediate water tank and an aeration pump. The first denitrification vertical flow constructed wetland unit consists of a volcanic rock layer, a packing layer, a quartz sand layer, and aquatic plants from bottom to top.

[0022] In the above scheme, the height of the volcanic rock layer, the filler layer, and the quartz sand layer of the aerated nitrification vertical flow wetland unit and the denitrification vertical flow constructed wetland unit in step (1) is 15cm. An outlet is set at the top of the volcanic rock layer, the filler layer, and the quartz sand layer. The treated water is discharged from the outlet at the top of the quartz sand layer of the denitrification vertical flow constructed wetland unit.

[0023] In the above scheme, the aquatic plant is one of the following: calamus, cattail, and iris.

[0024] In the above scheme, when the microbial biofilm is formed in step (2), the concentration of pollutants in the influent is set to COD=300mg / L and NH4+=300mg / L. + -N=25mg / L, NO3 - With N=15mg / L and TP=1mg / L, the influent and effluent are operated in a circulating reflux mode. After 26 days of operation, the biofilm in the system successfully formed.

[0025] In the above scheme, step (3) sets the hydraulic retention time of the aerated nitrification vertical flow wetland unit to 6-36h, the aeration rate to 2-4L / min, the hydraulic retention time of the denitrification vertical flow wetland unit to 6-36h, the carbon-nitrogen ratio to 3-9:1, and the temperature to 25-40℃.

[0026] In the above scheme, step (3) can be set to a hydraulic retention time of 6, 12, 24, 36 h, an aeration rate of 2, 3, 3.5, 4 L / min for the aerated nitrification vertical flow wetland unit, a hydraulic retention time of 6, 12, 24, 36 h, a carbon-nitrogen ratio of 3:1, 5:1, 7:1, 9:1, and a temperature of 25, 30, 35, 40℃ for the denitrification vertical flow wetland unit.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. Bottom sediment dredging is a direct means of removing pollutants accumulated inside water bodies. Its own composition and properties are suitable for making a kind of artificial wetland filler, which can replace the raw materials of artificial wetlands and be used in artificial wetland systems. This not only realizes the reuse of waste and reduces the waste of land resources, but also deeply implements the environmental protection concept of "turning waste into treasure" and finds a new way to reuse bottom sediment dredged from water bodies.

[0029] 2. A two-stage vertical flow constructed wetland based on sediment-based filler is used for advanced treatment of wastewater effluent from a wastewater treatment plant. The influent COD is 50 mg / L, and NH4+ is... + -N=5mg / L, NO3 - -N=10mg / L, TP=0.5mg / L, COD, NH4 + -N, NO3 - The average removal efficiencies of -N and TP were 50.54%, 93%, 97.7%, and 76.8%, respectively. This invention provides a scientific basis for the optimization and stable operation of constructed wetlands based on sediment-based fillers in water bodies, and achieves the goal of "treating waste with waste" for dredged sediment. Attached Figure Description

[0030] Figure 1 This is a structural diagram of the two-stage vertical flow constructed wetland of aeration nitrification-denitrification according to the present invention;

[0031] The components include: 1. Aerated nitrification vertical flow wetland unit; 2. Denitrification vertical flow constructed wetland unit; 3. Inlet pump; 4. Inlet tank; 5. Aeration disc; 6. Aeration pump; 7. Support tray; 8. Volcanic rock layer; 9. Packing layer; 10. Quartz sand layer; 11. Aquatic plants; 12. Outlet; and 13. Intermediate water tank. Detailed Implementation

[0032] The technical solution and effects of the present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0033] The sediment of this invention is derived from a dredged water body, wherein the mass fractions of SiO2, Al2O3, CaO and Fe2O3 are 64.73%, 11.92%, 8.64% and 5.51%, respectively. Comparative Example

[0034] The preparation method of the sediment-based filler material in this comparative example includes the following steps:

[0035] The first step is to place the dredged sediment with a moisture content of 74.85% in a 105℃ oven for 24 hours. After drying, the sediment will have a blocky structure. Remove impurities such as animal and plant remains, bricks, and leaves. Grind the sediment in a mortar and pestle and then pass it through a 100-mesh sieve.

[0036] The second step is to mix the bottom mud and zeolite powder obtained in the first step at a mass ratio of 1:0.075, while adding distilled water and stirring until the mixture has a certain viscosity and no flowable mud.

[0037] The third step is to take out the mud ball and put it into a mud pellet making machine to make spherical ceramic pellet samples with uniform particle size, and control the weight of each sample to be 10±0.2 g.

[0038] The fourth step is to place the sample in an oven and dry it at 105℃ for 2 hours. After drying, the sample is placed in a muffle furnace for high-temperature calcination. The high-temperature calcination temperature rise program is as follows: the temperature rise rate is 7℃ / min, from room temperature to 400℃, and the temperature is held at 400℃ for 20 minutes. The temperature is then raised to 800℃ and held for 30 minutes. After the temperature rises, the sample is allowed to cool naturally to room temperature to obtain the water body bottom sediment-based filler.

[0039] The filler prepared by the above method has a specific surface area and total pore volume of 3.43 m². 2 / g, 0.024cm 3 / g, the median pore size of the BJH packing is 2.24 nm. Example 1

[0040] The method for preparing the sediment-based filler material in this embodiment includes the following steps:

[0041] The first step is to place the dredged sediment with a moisture content of 74.85% in a 105℃ oven for 24 hours. After drying, the sediment will have a blocky structure. Remove impurities such as animal and plant remains, bricks, and leaves. Grind the sediment in a mortar and pestle and then pass it through a 100-mesh sieve.

[0042] The second step is to mix the bottom mud, zeolite powder, and starch obtained in the first step at a mass ratio of 1:1:0.15, while adding distilled water and stirring until the mixture has a certain viscosity and no flowable mud.

[0043] The third step is to take out the mud ball and put it into a mud pellet making machine to make spherical ceramic pellet samples with uniform particle size, and control the weight of each sample to be 10±0.2 g.

[0044] The fourth step is to place the sample in an oven and dry it at 105℃ for 2 hours. After drying, the sample is placed in a muffle furnace for high-temperature calcination. The high-temperature calcination temperature rise program is as follows: the temperature rise rate is 7℃ / min, from room temperature to 400℃, and the temperature is held at 400℃ for 20 minutes. The temperature is then raised to 800℃ and held for 30 minutes. After the temperature rises, the sample is allowed to cool naturally to room temperature to obtain the water body bottom sediment-based filler.

[0045] The filler prepared by the above method has a specific surface area and total pore volume of 8.92 m². 2 / g, 0.05cm 3 / g, the median pore size of the BJH packing is 2.05 nm. Example 2

[0046] The method for preparing the sediment-based filler material in this embodiment includes the following steps:

[0047] The first step is to place the dredged sediment with a moisture content of 74.85% in a 105℃ oven for 24 hours. After drying, the sediment will have a blocky structure. Remove impurities such as animal and plant remains, bricks, and leaves. Grind the sediment in a mortar and pestle and then pass it through a 100-mesh sieve.

[0048] The second step is to mix the bottom mud, zeolite powder, and starch obtained in the first step at a mass ratio of 1:1:0.15, while adding distilled water and stirring until the mixture has a certain viscosity and no flowable mud.

[0049] The third step is to take out the mud ball and put it into a mud pellet making machine to make spherical ceramic pellet samples with uniform particle size, and control the weight of each sample to be 10±0.2 g.

[0050] The fourth step is to place the sample in an oven and dry it at 105℃ for 2 hours. After drying, the sample is placed in a muffle furnace for high-temperature calcination. The high-temperature calcination temperature rise program is as follows: the temperature rise rate is 7℃ / min, from room temperature to 400℃, and the temperature is held at 400℃ for 20 minutes. The temperature is then raised to 900℃ and held for 30 minutes. After the temperature rises, the sample is allowed to cool naturally to room temperature to obtain the water body bottom sediment-based filler.

[0051] The filler prepared by the above method has a specific surface area and total pore volume of 1.49 m². 2 / g, 0.012cm 3 / g, the median pore size of the BJH packing material is 2.87 nm. Example 3

[0052] The method for preparing the sediment-based filler material in this embodiment includes the following steps:

[0053] The first step is to place the dredged sediment with a moisture content of 74.85% in a 105℃ oven for 24 hours. After drying, the sediment will have a blocky structure. Remove impurities such as animal and plant remains, bricks, and leaves. Grind the sediment in a mortar and pestle and then pass it through a 100-mesh sieve.

[0054] The second step is to mix the bottom mud, zeolite powder, and starch obtained in the first step at a mass ratio of 1:0.667:0.125, while adding distilled water and stirring until the mixture has a certain viscosity and no flowable mud.

[0055] The third step is to take out the mud ball and put it into a mud pellet making machine to make spherical ceramic pellet samples with uniform particle size, and control the weight of each sample to be 10±0.2 g.

[0056] The fourth step is to place the sample in an oven and dry it at 105℃ for 2 hours. After drying, the sample is placed in a muffle furnace for high-temperature calcination. The high-temperature calcination temperature rise program is as follows: the temperature rise rate is 7℃ / min, from room temperature to 400℃, and the temperature is held at 400℃ for 20 minutes. The temperature is then raised to 800℃ and held for 30 minutes. After the temperature rises, the sample is allowed to cool naturally to room temperature to obtain the water body bottom sediment-based filler.

[0057] The filler prepared by the above method has a specific surface area and total pore volume of 3.89 m². 2 / g, 0.032cm 3 / g, the median pore size of the BJH packing is 2.06 nm.

[0058] Application examples

[0059] The sediment-based filler prepared in Example 1 was applied to the treatment of effluent from a wastewater treatment plant in Zhengzhou City using an artificial wetland, including the following steps:

[0060] (1) Construct a two-stage vertical flow constructed wetland of aeration nitrification and denitrification, such as Figure 1As shown, the constructed wetland includes an aerated nitrification vertical flow wetland unit 1 and a denitrification vertical flow constructed wetland unit 2. In this application example, the effective height of the aerated nitrification vertical flow wetland unit 1 and the denitrification vertical flow constructed wetland unit 2 is 48cm, the diameter is 20cm, and the effective volume is 6L. The main body is cylindrical and made of plexiglass. The bottom of the aerated nitrification vertical flow wetland unit 1 is connected to the inlet tank 4 through the inlet pump 3. An aeration disc 5 is set at the bottom of the aerated nitrification vertical flow wetland unit 1, which is connected to the aeration pump 6. Above the aeration disc 5, a support tray 7, a volcanic rock layer 8, a packing layer 9, a quartz sand layer 10, and aquatic plants 11 are arranged in sequence. In step (1), the outlet 12 of the quartz sand layer 10 transports water to the denitrification vertical flow constructed wetland unit 2 through the intermediate water tank 13 and the inlet pump 3. The denitrification vertical flow constructed wetland unit 2 consists of a volcanic rock layer 8, a packing layer 9, a quartz sand layer 10, and aquatic plants 11 from bottom to top. In step (1), the height of the volcanic rock layer 8, the packing layer 9, and the quartz sand layer 10 of the aerated nitrification vertical flow wetland unit 1 and the denitrification vertical flow constructed wetland unit 2 is 15cm. An outlet 12 is set at the top of each of the volcanic rock layer 8, the packing layer 9, and the quartz sand layer 10. The treated water is discharged from the outlet 12 at the top of the quartz sand layer 10 of the denitrification vertical flow constructed wetland unit 2.

[0061] (2) Start the two-stage vertical flow constructed wetland of aeration nitrification-denitrification, and use sludge from the secondary sedimentation tank of the sewage treatment plant for microbial biofilm formation; when carrying out microbial biofilm formation, the influent pollutant concentration is set to COD=300mg / L and NH4+=300mg / L. + -N=25mg / L, NO3 - With N=15mg / L and TP=1mg / L, the influent and effluent are operated in a circulating reflux mode. After 26 days of operation, the biofilm formation in the system was successful.

[0062] (3) Wastewater treatment plant effluent (COD, NH4) + -N, NO3 - The concentrations of nitrogen (N) and total phosphorus (TP) are 50 mg / L, 5 mg / L, 10 mg / L, and 0.5 mg / L, respectively. These are pumped into a two-stage vertical flow constructed wetland for aeration and denitrification. Simultaneously, aeration pump 6 is activated to supply oxygen to the aeration and nitrification vertical flow wetland unit 1 via aeration discs 5. Wastewater effluent from the wastewater treatment plant, after treatment in the aeration and nitrification vertical flow wetland unit 1, enters the intermediate water tank 13, and then is pumped by inlet pump 3 into the denitrification vertical flow constructed wetland 2. Finally, the treated effluent is discharged. The hydraulic retention time of the aeration and nitrification vertical flow wetland unit is 12 h, and the aeration rate is 3.5 L / min. The hydraulic retention time of the denitrification vertical flow wetland unit is 24 h, the carbon-to-nitrogen ratio is 9:1, and the temperature is 30℃.

[0063] In the above scheme, the volcanic rock layer 8, filler layer 9, quartz sand layer 10, and aquatic plant 11 in the aerated nitrification vertical flow wetland unit 1 and the denitrification vertical flow constructed wetland unit 2 are the same. Among them, the volcanic rock in the volcanic rock layer 8 is 15 cm thick and the particle size is 8~15 mm. The quartz sand in the quartz sand layer 10 is 15 cm thick and the particle size is 2~4 mm. The aquatic plant is calamus. Four plants are planted in each of the aerated nitrification vertical flow wetland unit 1 and the denitrification vertical flow constructed wetland unit 2.

[0064] COD and NH4 in the effluent + -N, NO3 - The concentrations of -N, TN, and TP were 24.73 mg / L, 0.35 mg / L, 0.23 mg / L, and 0.116 mg / L, respectively, with removal efficiencies of 50.54%, 93%, 97.7%, and 76.8%.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. The application of bottom sediment in the advanced treatment of effluent from wastewater treatment plants, characterized in that, Wastewater COD = 50 mg / L, NH4 + -N=5mg / L, NO3 - -N=10mg / L, TP=0.5mg / L; COD and NH4+ in the water after advanced treatment + -N, NO3 - The concentrations of -N and TP were 24.73 mg / L, 0.35 mg / L, 0.23 mg / L, and 0.116 mg / L, with removal efficiencies of 50.54%, 93%, 97.7%, and 76.8%, respectively. The application specifically includes the following steps: (1) Preparation of packing material: The first step is to place the dredged sediment with high water content in a 105℃ oven for 24 hours. After drying, the sediment will have a blocky structure. Remove the impurities, grind it in a mortar and pestle, and then pass it through a 100-mesh sieve. The second step is to mix the bottom mud, zeolite powder, and starch obtained in the first step in a certain proportion, while adding distilled water and stirring until the mixture has a certain viscosity and no fluidity. The third step is to take out the mud ball and put it into a mud pellet making machine to make spherical ceramic pellet samples with uniform particle size, and control the weight of each sample to be 10±0.2 g. The fourth step is to place the sample in an oven and dry it at 105℃ for 2 hours; then place the dried sample in a muffle furnace for high-temperature calcination to obtain the water body bottom sediment-based filler. In the first step, the bottom sediment had a water content of 74.85%, and the mass fractions of SiO2, Al2O3, CaO, and Fe2O3 were 64.73%, 11.92%, 8.64%, and 5.51%, respectively. In the second step, the mass ratio of bottom mud, zeolite powder, and starch is 1:1:0.15; The heating procedure for the fourth step of high-temperature roasting is as follows: heating rate 7℃ / min, from room temperature to 400℃, hold at 400℃ for 20min; continue heating to 800℃, hold for 30min; The specific surface area and total pore volume of the sediment-based filler prepared by the method were 8.92 m². 2 / g, 0.05cm 3 / g, the median pore size of the BJH packing material is 2.05 nm; (2) Construct a two-stage vertical flow constructed wetland of aeration nitrification and denitrification; (3) Start the two-stage vertical flow constructed wetland of aeration nitrification-denitrification, and use the sludge from the secondary sedimentation tank of the sewage treatment plant for microbial biofilm formation; (4) The wastewater effluent from the wastewater treatment plant is pumped into the two-stage vertical flow constructed wetland of aeration nitrification and denitrification. At the same time, the aeration pump is turned on to provide oxygen to the aeration nitrification vertical flow wetland unit through the aeration disc. After being treated by the aeration nitrification vertical flow wetland unit, the wastewater effluent from the wastewater treatment plant enters the intermediate water tank, and then enters the denitrification vertical flow constructed wetland through the inlet pump. Finally, the treated effluent is discharged. The two-stage vertical flow constructed wetland of aeration nitrification-denitrification in step (2) includes an aeration nitrification vertical flow wetland unit and a denitrification vertical flow constructed wetland unit. The bottom of the aeration nitrification vertical flow wetland unit is connected to an inlet tank via an inlet pump. An aeration disc is set at the bottom of the aeration nitrification vertical flow wetland unit, which is connected to an aeration pump. Above the aeration disc, a support tray, a volcanic rock layer, a packing layer, a quartz sand layer, and aquatic plants are arranged in sequence. The outlet of the quartz sand layer in the aeration nitrification vertical flow wetland unit transports water to the denitrification vertical flow constructed wetland unit through an intermediate water tank and an aeration pump. The denitrification vertical flow constructed wetland unit consists of a volcanic rock layer, a packing layer, a quartz sand layer, and aquatic plants from bottom to top. The volcanic rock layer, packing layer, quartz sand layer, and aquatic plants in the aeration nitrification vertical flow wetland unit and the denitrification vertical flow constructed wetland unit are the same. Among them, the volcanic rock in the volcanic rock layer is 15 cm thick and has a particle size of 8~15 cm. mm, the quartz sand layer is 15 cm thick with a particle size of 2-4 mm, the aquatic plant is sweet flag, and 4 plants are planted in each of the aerated nitrification vertical flow wetland unit and the denitrification vertical flow constructed wetland unit. In step (2), the height of the volcanic rock layer, the filler layer, and the quartz sand layer of the aerated nitrification vertical flow wetland unit and the denitrification vertical flow constructed wetland unit is 15cm. An outlet is set at the top of the volcanic rock layer, the filler layer, and the quartz sand layer. The treated water is discharged from the outlet at the top of the quartz sand layer of the denitrification vertical flow constructed wetland unit. In step (3), when the microbial biofilm is formed, the concentration of pollutants in the influent is set to COD=300mg / L and NH4+=300mg / L. + -N=25mg / L, NO3 - With N=15mg / L and TP=1mg / L, the influent and effluent are operated in a circulating reflux mode. After 26 days of operation, the biofilm formation in the system was successful. In step (4), the hydraulic retention time of the aerated nitrification vertical flow wetland unit is set to 12h, the aeration rate is 3.5L / min, the hydraulic retention time of the denitrification vertical flow wetland unit is set to 24h, the carbon-nitrogen ratio is 9:1, and the temperature is 30℃.

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