Combined enhanced denitrification device and method based on magnetic field-modified polyurethane composite material

Abstract

The invention discloses a combined enhanced denitrification device and method based on a magnetic field-modified polyurethane composite material, the device comprises a water inlet area, a gravel filler area, an aeration area, a polyurethane filler tray area, a sludge discharge area, a water outlet area and a PLC controller, nZVI-coated SiO2, gravel and a strong magnet are configured in the gravel filler area, anaerobic denitrification is carried out on micro-polluted water under the action of a strong magnetic field, and then the micro-polluted water is subjected to anaerobic denitrification under the action of the strong magnetic field; degrading part of organic matters and nitrate; an aeration disc is arranged in the water inlet area for back flushing; and a modified polyurethane sponge filler plate is arranged in the polyurethane filler plate area, and is used for carrying out aerobic denitrification and microbial denitrification on the aerated and oxygenated water body to generate sludge precipitate. The problems that an inorganic electron donor is unstable in release speed, poor in synergistic effect with microorganisms and the like are solved, flora loss is avoided, the later biofilm formation time is shortened, the biological activity of the microorganisms is promoted, the enhanced nitrogen removal process of the water body is more effectively promoted, and efficient nitrogen removal of the micro-polluted water body is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of water pollution control, and particularly to an enhanced denitrification device and method based on the combined use of magnetic field-modified polyurethane composite materials. Background Art

[0002] Nitrate pollution in water sources is a global problem. Excessive nitrates can lead to eutrophication of water source water bodies and algal blooms, which in turn endanger human health. In the prior art, physical, chemical, and biological methods have all been applied, but they generally suffer from problems such as low treatment efficiency, high cost, and secondary pollution. Therefore, developing an efficient, environmentally friendly, and economical method to remove nitrates from water sources is an urgent problem to be solved.

[0003] In recent years, aerobic denitrification has become an emerging treatment technology. Among them, the selection and use of electron donors are the key factors affecting the treatment effect. Facing eutrophic water source water bodies with low organic matter content and insufficient electron donors, it is difficult for aerobic denitrifying bacteria to effectively remove nitrates to ensure the safety of water source water bodies. Existing studies have enhanced their denitrification through reducing inorganic substances (iron and manganese). However, existing inorganic electron donors still have some significant limitations in actual application processes: (1) The release rate of inorganic electron donors is difficult to control, often leading to an excess or deficiency of electron donors, affecting the efficiency and effect of the denitrification reaction. (2) There is a lack of effective synergy between simple inorganic electron donors and microorganisms, making it difficult to fully utilize the biocatalytic ability of microorganisms, resulting in low overall denitrification efficiency.

[0004] Therefore, it is of great significance to develop a method and device for enhanced denitrification by combining a composite filler of an electron slow-release agent-aerobic denitrifying bacteria with a magnetic field. Summary of the Invention

[0005] To solve the above-mentioned defects in the prior art, the purpose of the present invention is to provide an enhanced denitrification device and method based on the combined use of magnetic field-modified polyurethane composite materials to solve the problems of unstable release rate and poor synergy with microorganisms existing in existing inorganic electron donors. Under the action of a weak magnetic field, the present invention can promote microbial metabolism and improve microbial activity. Fixing aerobic denitrifying bacteria on the surface of the composite material to construct a synergistic system of inorganic materials and denitrifying organisms, avoiding the loss of bacterial communities and at the same time slowing down the later film-forming time, and is applicable to the denitrification technical field of low carbon-nitrogen ratio slightly polluted water bodies.

[0006] The present invention is achieved by the following technical solutions.

[0007] One aspect of the present invention provides an enhanced denitrification device based on the combined use of magnetic field-modified polyurethane composite materials, including:

[0008] The influent zone, located at the bottom of the device, is used to control the influent flow rate of slightly polluted water and is equipped with an aeration disk for backwashing;

[0009] The grit packing zone, located above the influent zone, is equipped with nZVI@SiO2, grit and a strong magnet, and is used for anaerobic denitrification of slightly polluted water under the action of a strong magnetic field to degrade part of the organic matter and nitrate;

[0010] The aeration zone, located above the grit packing zone, is used for aeration and oxygenation of the water body undergoing anaerobic denitrification;

[0011] The polyurethane packing disk zone, located above the aeration zone, is equipped with modified polyurethane sponge packing disks and is used for aerobic denitrification and microbial nitrogen removal of the aerated and oxygenated water body to generate sludge precipitation;

[0012] The sludge discharge zone, located in the middle of the aeration zone, grit packing zone and influent zone below the polyurethane packing disk zone, is used to discharge the generated sludge;

[0013] The effluent zone, located at the top of the device, is used to store the effluent of the water body undergoing aerobic denitrification and microbial nitrogen removal;

[0014] The PLC controller is respectively connected to the influent zone, grit packing zone and polyurethane packing disk zone, and is used to control the influent, aeration, magnetic field intensity and system operation.

[0015] Preferably, the influent zone is connected to the slightly polluted water body source through a feed pump and a feed pipe. The influent zone is provided with uniformly distributed water distribution pipes and an aeration disk connected to the aeration zone.

[0016] Preferably, the grit packing zone is filled with nZVI@SiO2 and grit in a volume ratio of 1:(2 - 5). A pressure detector and a strong magnet are provided at the top of the grit packing zone.

[0017] Preferably, the aeration zone is provided with aeration pipes, and the aeration pipes are connected to the aeration disk through an aerator.

[0018] Preferably, a pollutant detection system and a strong magnet are provided in the polyurethane packing disk zone, and a number of modified polyurethane packing disks are arranged in an array. The modified polyurethane packing disks are mounted on a steel frame.

[0019] Preferably, the polyurethane packing disk is filled with a polyurethane composite carrier material, and the filling method includes the following steps:

[0020] a. Clean and dry the hydrophilic polyurethane sponge for later use;

[0021] b. Dissolve the binder polyvinyl alcohol in water in a volume ratio of 1:(10 - 50), and then place it in a water bath and stir to dissolve at a temperature of 60 - 80°C to obtain glue-like polyvinyl alcohol;

[0022] c. Apply polyvinyl alcohol evenly on the hydrophilic polyurethane sponge by brushing, and distribute the binder in the polyurethane sponge body by extrusion, and extrude the excess binder.

[0023] d. Dissolve the silica-coated nano zero-valent iron powder in deoxygenated water according to the mass ratio of (3 - 10):1, stir and ultrasonicate to prepare a silica-coated nano zero-valent iron suspension.

[0024] e. Sprinkle the silica-coated nano zero-valent iron suspension on each polyurethane sponge coated with polyvinyl alcohol, and vacuum-dry the polyurethane sponge. 3 Sprinkle the silica-coated nano zero-valent iron suspension on each polyurethane sponge coated with polyvinyl alcohol, and vacuum-dry the polyurethane sponge.

[0025] f. Before use, soak the dried modified polyurethane sponge in the aerobic denitrifying bacteria solution for a period of time, and then fill it into the polyurethane packing tray.

[0026] Preferably, in step d, the concentration of the silica-coated nano zero-valent iron suspension is 0.3 - 0.5 mg / L.

[0027] In step e, place the polyurethane sponge in a vacuum oven and dry it at a temperature of 40 - 60 °C for 12 - 24 h.

[0028] In step f, soak the dried modified polyurethane sponge in the aerobic denitrifying bacteria solution with a concentration of 10 9 ~10 10 cells / mL for 2 - 4 h.

[0029] Preferably, a sludge discharge pipe is provided at the bottom of the sludge discharge area, and water distribution plates are provided at the top of the sludge discharge area and the bottom of the polyurethane packing tray area. The sludge discharge areas on both sides of the water distribution plate are set as arc transition surfaces.

[0030] Another aspect of the present invention provides a method for enhanced denitrification of the enhanced denitrification device based on the combination of magnetic field - modified polyurethane composite material, including:

[0031] Thread the modified polyurethane packing trays on the steel frame in the polyurethane packing tray area;

[0032] Control the nitrate nitrogen concentration, total nitrogen concentration and influent flow rate of the slightly polluted influent;

[0033] The slightly polluted water body first enters the gravel packing area, and fill the mixed and uniform nZVI@SiO2 and gravel in the gravel packing area; control the magnetic field intensity at the center of the device; the slightly polluted water body undergoes anaerobic denitrification under the combined action of the magnetic field and the slow release of inorganic electrons by nZVI@SiO2.

[0034] The slightly polluted water after degradation is aerated and oxygenated in the aeration area, and at the same time, the aeration disc in the water inlet area is connected to the aeration area for backwashing;

[0035] Under the combined action of aerobic denitrifying microorganisms and denitrifying microorganisms formed by biofilm attachment in the polyurethane packing disc area, and the strong magnetic field, the anaerobic denitrifying water body undergoes microbial denitrification to generate precipitation;

[0036] The water body after enhanced denitrification by denitrification is discharged through the water outlet area; the treated sludge is discharged through the sludge discharge area.

[0037] Preferably, the concentration of nitrate nitrogen in the influent is controlled to be 4.23 - 10.26 mg / L, and the total nitrogen concentration is controlled to be 5.36 - 12.03 mg / L; the influent flow rate is controlled to be 12 L / h;

[0038] The magnetic field intensity at the center of the device is 18 - 20 mT;

[0039] nZVI@SiO2 and gravel are filled in a volume ratio of 1:(2 - 5);

[0040] The hydraulic retention time of the whole device is 8 - 10 hours.

[0041] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:

[0042] 1. In the enhanced denitrification device based on the combination of magnetic field - modified polyurethane composite provided by the present invention, slightly polluted water first flows into the nZVI@SiO2 gravel packing area, and anaerobic denitrification occurs under the combined action of the magnetic field and nZVI@SiO2 inorganic electrons. The presence of the magnetic field can accelerate the transfer efficiency of substrates, increase the concentration of nitrate and organic matter around microorganisms, and thus accelerate the rate of the denitrification reaction.

[0043] 2. The treated water body is oxygenated in the aeration area to provide necessary dissolved oxygen for subsequent reactions. Subsequently, the water body flows into the polyurethane packing disc area, and under the stimulation of microorganisms on the polyurethane sponge packing disc and the magnetic field, nitrate pollutants are co - treated.

[0044] 3. During the entire denitrification process, the stimulating effect of the magnetic field plays a crucial role. On the one hand, the magnetic field enhances the metabolic activities of denitrifying bacteria, thereby accelerating the denitrification reaction; on the other hand, the magnetic field improves the transfer efficiency of substrates during the denitrification process, thus further promoting the increase in the reaction rate. The device realizes organic synergy by integrating the magnetic field, inorganic electron donors, and aerobic denitrifying bacteria, thereby significantly enhancing the denitrification efficiency in each region. The magnetic field in the polyurethane packing disk area can change the microbial community structure, slow down the cycle of forming an efficient biofilm on the modified polyurethane sponge. At the same time, the magnetic field can also promote the utilization of inorganic electrons by aerobic microorganisms on the modified polyurethane sponge, enhance the electron transfer efficiency, and thus more effectively promote the nitrogen removal process of the water body.

[0045] 4. The device of the present invention is equipped with a pressure detector to monitor the pressure in the nZVI@SiO2 gravel packing area. When the detected pressure exceeds the standard, the system will control the opening of the aeration disk and the water distribution plate for backwashing through a signal, and at the same time, close the water inlet pump to stop water intake. The wastewater for backwashing flows out from the sludge discharge area. If the detected water quality of the effluent does not meet the standard, the water inlet pump will be closed, and the polyurethane sponge packing disk will be replaced. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute an improper limitation to the present invention. In the drawings:

[0047] Figure 1 is a front view schematic diagram of the enhanced nitrogen removal device based on the combined use of magnetic field-modified polyurethane composites proposed by the present invention;

[0048] Figure 2 is an A-A sectional view of the enhanced nitrogen removal device based on the combined use of magnetic field-modified polyurethane composites proposed by the present invention;

[0049] Figure 3 is a B-B sectional view of the enhanced nitrogen removal device based on the combined use of magnetic field-modified polyurethane composites proposed by the present invention;

[0050] Figure 4 is a C-C sectional view of the enhanced nitrogen removal device based on the combined use of magnetic field-modified polyurethane composites proposed by the present invention;

[0051] Figure 5 is a large-scale drawing of the polyurethane packing disk of the enhanced nitrogen removal device based on the combined use of magnetic field-modified polyurethane composites proposed by the present invention.

[0052] In the figure: 1 - inlet water pump; 2 - inlet water pipe; 3 - inlet water area; 4 - grit packing; 5 - aeration area; 6 - strong magnet; 7 - polyurethane packing disk area; 8 - outlet water pipe; 9 - pollutant detection system; 10 - modified polyurethane packing disk; 11 - steel frame; 12 - aeration pipe; 13 - pressure sensor; 14 - PLC controller; 15 - sludge discharge area; 16 - water distribution plate; 17 - sludge discharge pipe; 18 - aeration disk; 19 - water distribution pipe; 20 - aerator; 21 - electromagnetic valve. Specific embodiments

[0053] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Here, the illustrative embodiments of the present invention and the description are used to explain the present invention, but do not limit the present invention.

[0054] As Figure 1 shown, the embodiment of the present invention provides a device for enhancing denitrification by combining a magnetic field and a modified polyurethane composite material, including an inlet water area 3, a grit packing area 4, an aeration area 5, a polyurethane packing disk area 7, a sludge discharge area 15 and an outlet water area 8. The inlet water area 3, the grit packing area 4, the aeration area 5 and the polyurethane packing disk area 7 are distributed successively from bottom to top. The sludge discharge area 15 is located in the middle of the aeration area 5, the grit packing area 4 and the inlet water area 3 below the polyurethane packing disk area 7, and the outlet water area 8 is located at the top of the device.

[0055] The slightly polluted water is connected to the inlet water area 3 through the inlet water pump 1 and the inlet water pipe 2. The inlet water area 3 is provided with uniformly distributed water distribution pipes 19, and the inlet water flow is controlled by the inlet water pump 1. The inlet water area 3 is provided with aeration disks 18 connected to the aeration area 5 for backwashing. The distribution of the aeration disks 18 is shown in Figure 4 the figure.

[0056] Above the inlet water area 3 is the grit packing area 4, which is filled with nZVI@SiO2 and grit. The nZVI@SiO2 and grit are filled in a volume ratio of 1:(2 - 5). A pressure detector 13 is provided at the top of the grit packing area 4 for real-time pressure detection.

[0057] Above the grit packing area 4 is the aeration area 5, which is provided with aeration pipes 12. The aeration pipes 12 are connected to the aeration disks 18 through the aerator 20 for oxygen charging and gas charging, and an electromagnetic valve 21 is provided on the connecting pipeline. The distribution of the aeration pipes 12 is shown in Figure 3 the figure.

[0058] Above the aeration area 5 is the polyurethane packing disk area 7, in which there are several modified polyurethane packing disks 10. The modified polyurethane packing disks 10 are mounted on the steel frame 11 and are arranged in an array; the polyurethane packing disks are as shown in Figure 5 the figure, with a wire mesh on the periphery and holes for the steel frame to pass through in the middle. The structure of the polyurethane packing disk area 7 is shown in Figure 2 the figure.

[0059] A pollutant detection system 9 is also provided in the polyurethane filler panel area 7.

[0060] Strong magnets 6 are respectively arranged on the inner walls of the gravel filler area 4 and the polyurethane filler panel area 7. The strong magnets 6 are used to apply an external magnetic field to the device, and the magnetic field intensity at the center of the device is 18 - 20 mT.

[0061] The water outlet area 8 is located on the side wall of the device above the polyurethane filler panel area 7, and the treated water is discharged through the water outlet pipe.

[0062] A sludge discharge pipe 17 is provided at the bottom of the sludge discharge area 15. A water distribution plate 16 is provided at the top of the sludge discharge area 15 and the bottom of the polyurethane filler panel area 7. The sludge discharge areas 15 on both sides of the water distribution plate 16 are provided with arc-shaped transition surfaces.

[0063] It also includes a PLC controller 14 that is respectively connected to the pollutant detection system 9, the pressure detector 13, the water inlet pump 1, and the electromagnetic valve 21. The pressure detector 13, the electromagnetic valve 21, the pollutant detection system 9, and the water inlet pump 1 are controlled by the PLC controller 14.

[0064] Among them, the polyurethane filler panel is filled with a polyurethane composite carrier material, and the filling method includes the following steps:

[0065] Step 1: Clean and dry the hydrophilic polyurethane sponge for later use.

[0066] Step 2: Dissolve the binder polyethylene in water according to a volume ratio of 1:(10 - 50), and then place it in a water bath and stir and dissolve at a temperature of 60 - 80 °C to obtain glue-like polyvinyl alcohol.

[0067] Step 3: Use a brush to evenly apply the polyvinyl alcohol on the hydrophilic polyurethane sponge, and make the binder distribute in the polyurethane sponge body by extrusion, and extrude the excess binder.

[0068] Step 4: Dissolve the silica-coated nano-zero-valent iron powder in deoxygenated water according to a mass ratio of (3 - 10):1, stir and ultrasonicate to prepare a silica-coated nano-zero-valent iron suspension with a concentration of 0.3 - 0.5 mg / L.

[0069] Step 5: Spray the silica-coated nano-zero-valent iron suspension on the polyurethane sponge coated with polyvinyl alcohol. The volume of the silica-coated nano-zero-valent iron suspension sprayed on each polyurethane sponge is 1 - 2 ml / cm 3 ; Place the polyurethane sponge in a vacuum oven and dry it at a temperature of 40 - 60 °C for 12 - 24 h;

[0070] Step 6: Before use, soak the dried modified polyurethane sponge in a concentration of 10 9 ~10 10It is used after 2 - 4 hours in the aerobic denitrifying bacteria solution of cells / mL and filled into the polyurethane filler tray.

[0071] Each time when the modified polyurethane filler tray needs to be replaced, close the water inlet pump 1 and open the water distribution plate 16. The shed microbial film and the remaining sludge can be discharged through the sludge discharge pipe 17, and the sludge discharge pipe 17 can also be used as an emptying pipe.

[0072] The working principle of the device of the present invention is as follows:

[0073] The slightly polluted water body first enters the gravel filler area, and anaerobic denitrification occurs under the combined action of the magnetic field and the slow-release inorganic electrons, degrading part of the organic matter and nitrates. Then it enters the aeration area to oxygenate the water body through the aeration pipe, and then enters the polyurethane filler tray area. Under the combined action of the fixed high-efficiency aerobic denitrifying microorganisms on the modified polyurethane sponge filler tray and the denitrifying microorganisms formed by biofilm attachment, the nZVI@SiO2 fixed on the polyurethane sponge is a slow-release inorganic electron donor for microbial denitrification use, further removing organic matter and nitrates, and Fe 3+ It can also combine with phosphates to form precipitates to remove phosphates in the slightly polluted water. In addition, under the action of the external magnetic field, the magnetic field can promote the proliferation of aerobic denitrifying bacteria groups and change the microbial community structure, making the bacteria beneficial to denitrification dominant. At the same time, the magnetic field can enhance the metabolic activities of denitrifying bacteria, accelerate the reduction of nitrates, and thus improve the denitrification rate. If the pressure detector detects that the pressure in the nZVI@SiO2 gravel filler area exceeds the standard, it will control the opening of the aeration disk and the water distribution plate for backwashing through signals. At the same time, close the water inlet of the water inlet pump and open the water distribution plate, and the backwashing wastewater flows out from the sludge discharge area. If it is detected that the water body effluent does not meet the standard, close the water inlet pump and replace the polyurethane sponge filler tray. The entire denitrification process is carried out under the stimulation of the magnetic field, which can enhance the metabolic activities of denitrifying bacteria, accelerate the reduction of nitrates, and can also affect the electron transport chain in microbial cells, affecting the rate constant of chemical reactions in the denitrification process, realizing the organic coordination of the magnetic field, inorganic electron donors, and aerobic denitrifying bacteria, and thus improving the denitrification effect in each area.

[0074] The embodiment of the present invention also provides a method for enhanced denitrification using the device for enhanced denitrification based on the combination of magnetic field - modified polyurethane composite materials, including the following steps:

[0075] S101, thread the modified polyurethane filler trays on the steel frame in the polyurethane filler tray area;

[0076] S102, control the nitrate nitrogen concentration of the slightly polluted influent to be 4.23 - 10.26 mg / L and the total nitrogen concentration to be 5.36 - 12.03 mg / L; detect the hydraulic flow rate in the gravel filler area 4 through the pressure detector 13, and control the water inlet flow rate of the water inlet pump 1 to be 12 L / h;

[0077] S103. The slightly polluted water first enters the gravel packing area 4, where the uniformly mixed nZVI@SiO2 and gravel are filled in a volume ratio of 1:(2 - 5); the magnetic field intensity at the center of the device is 18 - 20 mT; the slightly polluted water undergoes anaerobic denitrification under the combined action of the magnetic field formed by the strong magnet 6 in the gravel packing area 4 and the slow-release inorganic electrons of nZVI@SiO2 in the gravel packing area 4, degrading part of the organic matter and nitrate;

[0078] S104. The slightly polluted water after degradation enters the aeration area 5, where the water is oxygenated through the aeration pipe 12 and then enters the polyurethane packing disk area 7; meanwhile, the aeration disk 18 in the water inlet area 3 is connected to the aeration area 5 for backwashing; the aeration disk 18 is controlled by the PLC controller 14. When the detected pressure exceeds a certain value, the electromagnetic valve 21 is controlled to open through the PLC controller for backwashing through the aeration disk 18, and at the same time, the water inlet pump is controlled to stop water intake;

[0079] S105. Under the combined action of the aerobic denitrifying microorganisms fixed on the modified polyurethane sponge packing disk 10 in the polyurethane packing disk area 7, the denitrifying microorganisms formed by biofilm attachment, and the magnetic field intensity of the strong magnet 6, the nZVI@SiO2 fixed on the polyurethane sponge slowly releases inorganic electrons for microbial denitrification, further removing organic matter and nitrate. Fe 3+ It can also combine with phosphate to form a precipitate to remove phosphate in the slightly polluted water; meanwhile, under the action of the magnetic field, it can enhance the metabolic activity of denitrifying bacteria, accelerate the reduction of nitrate, and thus improve the denitrification rate;

[0080] S106. The hydraulic retention time of the whole device is 8 - 10 hours. When the level of nitrate in the water after denitrification enhanced nitrogen removal is not up to standard detected by the pollutant detection system 9, a signal is transmitted to the PLC 14, and the PLC closes the water inlet pump and replaces the modified polyurethane packing disk 10; when replacing the modified polyurethane packing disk 10, the shed biofilm is discharged from the sludge discharge area 15 by opening the water distribution plate 16; the water after denitrification enhanced nitrogen removal is discharged through the water outlet pipe in the water outlet area 8.

[0081] The present invention will be further described below through different embodiments.

[0082] Example 1:

[0083] 1) In the polyurethane packing disk area, the modified polyurethane packing disks are threaded on the steel frame.

[0084] The modified polyurethane packing disk is prepared according to the following steps:

[0085] The hydrophilic polyurethane sponge is washed, dried, and reserved;

[0086] Dissolve the binder polyvinyl alcohol in water according to a mass ratio of 1:30, then place it in a water bath and stir to dissolve at a temperature of 80 °C to obtain glue-like polyvinyl alcohol;

[0087] Use a brush to evenly apply the polyvinyl alcohol on the hydrophilic polyurethane sponge, and distribute the binder in the polyurethane sponge body by extrusion, and extrude the excess binder;

[0088] Dissolve the silica-coated nano-zero-valent iron powder in deoxygenated water according to a mass ratio of 3:1, stir and ultrasonicate to prepare a silica-coated nano-zero-valent iron suspension with a concentration of 0.4 mg / L;

[0089] Spray the silica-coated nano-zero-valent iron suspension on the polyurethane sponge coated with polyvinyl alcohol. The volume of the silica-coated nano-zero-valent iron suspension sprayed on each polyurethane sponge is 2 ml / cm 3 ; Place the polyurethane sponge in a vacuum oven and dry it at a temperature of 50 °C for 18 h;

[0090] Before use, soak the dried modified polyurethane sponge in an aerobic denitrifying bacteria solution with a certain concentration of 10 9 ~10 10 cells / mL for 3 h and then use it, and fill it into the polyurethane packing tray.

[0091] 2) Control the influent nitrate nitrogen concentration to be 10.26 mg / L and the total nitrogen concentration to be 9.65 mg / L; the influent flow rate is 12 L / h;

[0092] 3) Fill the uniformly mixed nZVI@SiO2 and gravel in the gravel packing area according to a volume ratio of 1:3; the magnetic field strength at the center of the device is 18 mT; the slightly polluted water body undergoes anaerobic denitrification in the gravel packing area 4 to degrade part of the organic matter and nitrate;

[0093] 4) Aerate the water body through the aeration pipe and then enter the polyurethane packing tray area; at the same time, the aeration disk in the influent area is connected to the aeration area for backwashing;

[0094] 5) The biological domestication time is 20 days, and the hydraulic retention time of the whole device is 8 hours.

[0095] In this example, the nitrate nitrogen concentration in the effluent of the denitrification device is 0.45 mg / L, the total nitrogen concentration in the effluent is 1.79 mg / L, the average nitrate nitrogen removal rate can reach 95%, and the average total nitrogen removal rate can reach 85%.

[0096] Example 2:

[0097] 1) Thread the modified polyurethane packing trays on the steel frame in the polyurethane packing tray area.

[0098] The modified polyurethane filler disk is prepared according to the following steps:

[0099] Clean and dry the hydrophilic polyurethane sponge for later use;

[0100] Dissolve the binder polyvinyl alcohol in water according to a mass ratio of 1:50, and then place it in a water bath and stir to dissolve at a temperature of 60 °C to obtain glue-like polyvinyl alcohol;

[0101] Use a brush to evenly apply the polyvinyl alcohol on the hydrophilic polyurethane sponge, and make the binder distribute in the polyurethane sponge body by extrusion, and extrude the excess binder;

[0102] Dissolve the silica-coated nano zero-valent iron powder in deoxygenated water according to a mass ratio of 10:1, stir and ultrasonicate to prepare a silica-coated nano zero-valent iron suspension with a concentration of 0.3 mg / L;

[0103] Spray the silica-coated nano zero-valent iron suspension on the polyurethane sponge coated with polyvinyl alcohol. The volume of the silica-coated nano zero-valent iron suspension sprayed on each polyurethane sponge is 1 ml / cm 3 ; Place the polyurethane sponge in a vacuum oven and dry it at a temperature of 60 °C for 12 h;

[0104] Before use, soak the dried modified polyurethane sponge in an aerobic denitrifying bacteria solution with a certain concentration of 10 9 ~10 10 cells / mL for 4 h and then use it, and fill it into the polyurethane filler disk.

[0105] 2) Control the influent nitrate nitrogen concentration to be 6.16 mg / L and the total nitrogen concentration to be 12.03 mg / L; the influent flow rate is 12 L / h;

[0106] 3) Fill the uniformly mixed nZVI@SiO2 and gravel in the gravel filler area according to a volume ratio of 1:2; the magnetic field strength at the center of the device is 19 mT; the slightly polluted water body undergoes anaerobic denitrification in the gravel filler area 4 to degrade part of the organic matter and nitrate;

[0107] 4) Aerate the water body through the aeration pipe and then enter the polyurethane filler disk area; at the same time, the aeration disk in the influent area is connected to the aeration area for backwashing;

[0108] 5) The biological domestication time is 20 days, and the hydraulic retention time of the whole device is 8 hours.

[0109] In this embodiment, the nitrate nitrogen concentration in the effluent of the denitrification device is 2.93 mg / L, the total nitrogen concentration in the effluent is 4.56 mg / L, the average nitrate nitrogen removal rate can reach 71%, and the average total nitrogen removal rate can reach 62%.

[0110] Example 3:

[0111] 1) Connect and string modified polyurethane packing trays on the steel frame in the polyurethane packing tray area.

[0112] The modified polyurethane packing tray is prepared according to the following steps:

[0113] Clean and dry the hydrophilic polyurethane sponge for later use;

[0114] Dissolve the binder polyethylene in water according to a mass ratio of 1:10, and then place it in a water bath and stir to dissolve at a temperature of 70 °C to obtain glue-like polyvinyl alcohol;

[0115] Use a brush to evenly apply polyvinyl alcohol on the hydrophilic polyurethane sponge, and make the binder distribute in the polyurethane sponge body through extrusion, and extrude the excess binder;

[0116] Dissolve the silica-coated nano-zero-valent iron powder according to a mass ratio of 7:1 in deoxygenated water, stir and ultrasonicate to prepare a silica-coated nano-zero-valent iron suspension with a concentration of 0.5 mg / L;

[0117] Spray the silica-coated nano-zero-valent iron suspension on the polyurethane sponge coated with polyvinyl alcohol. The volume of the silica-coated nano-zero-valent iron suspension sprayed on each polyurethane sponge is 1.5 ml / cm 3 ; Place the polyurethane sponge in a vacuum oven and dry it at a temperature of 40 °C for 24 h;

[0118] Before use, soak the dried modified polyurethane sponge in an aerobic denitrifying bacteria solution with a certain concentration of 10 9 ~10 10 cells / mL for 2 h and then use it, and fill it into the polyurethane packing tray.

[0119] 2) Control the influent nitrate nitrogen concentration to be 4.23 mg / L and the total nitrogen concentration to be 5.36 mg / L; the influent flow rate is 12 L / h;

[0120] 3) In the gravel packing area, fill the uniformly mixed nZVI@SiO2 and gravel according to a volume ratio of 1:5; the magnetic field strength at the center of the device is 20 mT; the slightly polluted water body undergoes anaerobic denitrification in the gravel packing area 4 to degrade part of the organic matter and nitrate;

[0121] 4) Aerate the water body through the aeration pipe and then enter the polyurethane packing tray area; at the same time, the aeration disk in the influent area is connected to the aeration area for backwashing;

[0122] 5) The biological domestication time is 20 days, and the hydraulic retention time of the whole device is 8 hours.

[0123] In this embodiment, the nitrate nitrogen concentration in the effluent of the denitrification device is 1.82 mg / L, the total nitrogen concentration in the effluent is 3.01 mg / L, the average removal rate of nitrate nitrogen can reach 82%, and the average removal rate of total nitrogen can reach 75%.

[0124] As can be seen from the above embodiments, the enhanced denitrification device based on the combination of magnetic field and modified polyurethane composite material of the present invention can efficiently remove nitrate nitrogen and total nitrogen in slightly polluted water bodies. The nitrate nitrogen concentration range in the effluent of the denitrification device is 0.45 - 2.93 mg / L, the total nitrogen concentration range in the effluent is 1.79 - 4.65 mg / L, the average removal rate of nitrate nitrogen is 71 - 95%, up to 95% at most; the average removal rate of total nitrogen is 62 - 85%, up to 85% at most. The denitrification effect of this device is obvious, without energy consumption, long service life and high stability. It is applicable to the technical field of efficient denitrification of slightly polluted water bodies.

[0125] The present invention is not limited to the above embodiments. Based on the disclosed technical solutions of the present invention, those skilled in the art can make some substitutions and deformations to some technical features without creative labor according to the disclosed technical content, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A device for strengthening denitrification based on magnetic field-modified polyurethane composite material, characterized in that: include The water inlet area, located at the bottom of the device, is used to control the inlet flow of slightly polluted water and is equipped with an aeration disk for backwashing; The gravel filling area, located above the water inlet area, is equipped with nZVI@SiO2, gravel and strong magnets, which are used to perform anaerobic denitrification on slightly polluted water under the action of a strong magnetic field to degrade some organic matter and nitrates; The aeration zone, located above the gravel fill zone, is used to aerate and oxygenate the water body for anaerobic denitrification; The polyurethane filler plate area is located above the aeration zone and is equipped with a modified polyurethane sponge filler plate for aerobic denitrification and microbial denitrification of the aerated and oxygenated water body to generate sludge precipitation; The sludge discharge area is located in the middle of the aeration area, the gravel fill area and the water inlet area below the polyurethane filler plate area and is used to discharge the generated sludge; The effluent area is located at the top of the device and is used to store the effluent from the aerobic denitrification and microbial denitrification process; The PLC controller is connected to the water inlet area, the gravel filler area and the polyurethane filler plate area respectively, and is used to control the water inlet, aeration, magnetic field strength and system operation.

2. The device for strengthening denitrification based on magnetic field-modified polyurethane composite material according to claim 1 is characterized in that: The water inlet area is connected to a slightly polluted water source through a water inlet pump and a water inlet pipe. The water inlet area is provided with evenly distributed water distribution pipes and an aeration disk connected to the aeration area.

3. The device for strengthening denitrification based on magnetic field-modified polyurethane composite material according to claim 1 is characterized in that: The gravel filling area is filled with nZVI@SiO2 and gravel in a volume ratio of 1:(2-5), and a pressure detector and a strong magnet are arranged on the top of the gravel filling area.

4. The device for strengthening denitrification based on magnetic field-modified polyurethane composite material according to claim 1 is characterized in that: The aeration area is provided with aeration pipes, and the aeration pipes are connected to the aeration plates through the aerators.

5. The device for strengthening denitrification based on magnetic field-modified polyurethane composite material according to claim 1 is characterized in that: The polyurethane filler plate area is provided with a pollutant detection system and a strong magnet, as well as a plurality of modified polyurethane filler plates distributed in an array, and the modified polyurethane filler plates are mounted on a steel frame.

6. The device for strengthening denitrification based on magnetic field-modified polyurethane composite material according to claim 5 is characterized in that: The polyurethane filler tray is filled with a polyurethane composite carrier material, and the filling method comprises the following steps: a. Wash and dry the hydrophilic polyurethane sponge for later use; b. Dissolve the binder polyethylene in water at a volume ratio of 1:(10-50), and then place in a water bath at a temperature of 60-80° C. and stir to dissolve to obtain glue-like polyvinyl alcohol; c. Use a brush to evenly apply polyvinyl alcohol on the hydrophilic polyurethane sponge, distribute the adhesive in the polyurethane sponge by squeezing, and squeeze out the excess adhesive; d. dissolving the silica-coated nano-zero-valent iron powder in deoxygenated water at a mass ratio of (3-10):1, stirring and ultrasonicating to prepare a silica-coated nano-zero-valent iron suspension; e, according to the volume of 1 ~ 2ml / cm 3 Spray the silica-coated nano zero-valent iron suspension on each polyurethane sponge coated with polyvinyl alcohol, and vacuum dry the polyurethane sponge; f. Before use, soak the dried modified polyurethane sponge in aerobic denitrifying bacteria solution for a period of time and then fill it into a polyurethane filler tray.

7. The device for strengthening denitrification based on magnetic field-modified polyurethane composite material according to claim 6 is characterized in that: In step d, the concentration of the silica-coated nano-zero-valent iron suspension is 0.3-0.5 mg / L; In step e, the polyurethane sponge is placed in a vacuum oven at a temperature of 40-60° C. and dried for 12-24 hours; In step f, the dried modified polyurethane sponge is immersed in a solution having a concentration of 10 9 ~10 10 cells / mL of aerobic denitrifying bacteria solution for 2 to 4 hours.

8. The device for strengthening denitrification based on magnetic field-modified polyurethane composite material combination according to claim 1 is characterized in that: A mud discharge pipe is arranged at the bottom of the mud discharge area, a water distribution plate is arranged at the top of the mud discharge area and the bottom of the polyurethane filler plate area, and the mud discharge areas on both sides of the water distribution plate are arranged as arc-shaped transition surfaces.

9. An enhanced denitrification method based on a magnetic field-modified polyurethane composite material combined enhanced denitrification device as described in any one of claims 1 to 8, characterized in that: include: Inserting a modified polyurethane filler plate on a steel frame in the polyurethane filler plate area; Control the nitrate nitrogen concentration, total nitrogen concentration and inlet flow rate of micro-polluted influent; The slightly polluted water first enters the gravel filling area, where the nZVI@SiO2 and gravel are mixed evenly. The magnetic field strength at the center of the device is controlled. The slightly polluted water undergoes anaerobic denitrification under the combined action of the magnetic field and the slow-release inorganic electrons of nZVI@SiO2. The degraded micro-polluted water is aerated and oxygenated in the aeration zone, and the aeration plate in the water inlet area is connected to the aeration zone for backwashing; Under the combined action of aerobic denitrifying microorganisms and biofilm-forming denitrifying microorganisms in the polyurethane filler disc area, as well as the strong magnetic field, the anaerobic denitrifying water body undergoes microbial denitrification and generates precipitation. The water body after denitrification enhanced denitrification is discharged through the effluent area; The treated sludge is discharged through the sludge discharge area.

10. The method for strengthening denitrification based on magnetic field-modified polyurethane composite material according to claim 9, characterized in that: Control the influent nitrate nitrogen concentration to 4.23-10.26 mg / L and total nitrogen concentration to 5.36-12.03 mg / L; control the influent flow rate to 12 L / h; The magnetic field strength at the center of the device is 18 to 20 mT; nZVI@SiO2 and gravel are filled in a volume ratio of 1:(2-5); The hydraulic retention time of the whole device is 8 to 10 hours.

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