A device and method for enhancing denitrification based on a magnetic field-modified polyurethane composite

Abstract

The application discloses a kind of based on magnetic field-modified polyurethane composite combined strengthening denitrification device and method, including water inlet area, gravel packing area, aeration zone, polyurethane packing tray area, sludge discharge area, water outlet area and PLC controller, nZVI is configured with gravel and strong magnet in gravel packing area @SiO2, under the action of strong magnetic field, anaerobic denitrification is carried out to slightly polluted water, and part of organic matter and nitrate is degraded;And in water inlet area, aeration tray is configured to backflush;In polyurethane packing tray area, modified polyurethane sponge packing tray is configured, and aerobic denitrification and microbial denitrification are carried out to aeration oxygenated water body, and sludge is generated and precipitated.The application solves the problems of unstable release speed of inorganic electron donor, poor synergistic effect with microorganisms and other problems, avoids the loss of bacterial flora, slows down the biofilm formation time in the later stage, promotes the biological activity of microorganisms, more effectively promotes the process of enhanced denitrification of water body, and realizes efficient denitrification of slightly polluted water body.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, specifically to a denitrification device and method based on the combined use of magnetic field and modified polyurethane composite materials. Background Technology

[0002] Nitrate pollution in water sources is a global problem. Excessive nitrates can lead to eutrophication and algal blooms in water bodies, thereby endangering human health. Current technologies employ physical, chemical, and biological methods, but these generally suffer from low treatment efficiency, high costs, and secondary pollution. Therefore, developing an efficient, environmentally friendly, and economical method for removing 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 key factors affecting the treatment effect. Faced with oligotrophic water sources with low organic matter content and insufficient electron donors, aerobic denitrifying bacteria have difficulty effectively removing nitrates to ensure the safety of the water source. Existing studies have enhanced denitrification by reducing inorganic substances (iron and manganese). However, existing inorganic electron donors still have some significant limitations in practical applications: (1) The release rate of inorganic electron donors is difficult to control, which often leads 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 inorganic electron donors and microorganisms, making it difficult to fully utilize the biocatalytic capacity of microorganisms, resulting in low overall denitrification efficiency.

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

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a nitrogen removal device and method based on a magnetic field-modified polyurethane composite material, thereby solving problems such as unstable release rates and poor synergistic effects with microorganisms in existing inorganic electron donors. Under the influence of a weak magnetic field, this invention promotes microbial metabolism and enhances microbial activity. By immobilizing aerobic denitrifying bacteria on the surface of the composite material, a synergistic system of inorganic materials and denitrifying organisms is constructed, preventing the loss of the bacterial population and slowing down the subsequent biofilm formation time. This invention is applicable to the field of nitrogen removal technology for slightly polluted water bodies with low C / N ratios.

[0006] The present invention is achieved through the following technical solution.

[0007] One aspect of the present invention provides a denitrification device based on a magnetic field-modified polyurethane composite material, comprising:

[0008] The inlet area, located at the bottom of the device, is used to control the inlet flow rate of slightly polluted water and is equipped with aeration discs for backwashing.

[0009] The gravel packing zone, located above the inlet zone, is equipped with nZVI@SiO2, gravel, and strong magnets. It is used to perform anaerobic denitrification of slightly polluted water under the action of a strong magnetic field, degrading some of the organic matter and nitrates.

[0010] The aeration zone, located above the gravel packing zone, is used to aerate and oxygenate the anaerobic denitrification water.

[0011] The polyurethane packing disc area, located above the aeration zone, is equipped with modified polyurethane sponge packing discs for aerobic denitrification and microbial denitrification of the aerated water, generating sludge sedimentation.

[0012] The sludge discharge zone, located in the middle of the aeration zone, gravel packing zone, and inlet zone below the polyurethane packing disc 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 from aerobic denitrification and microbial denitrification.

[0014] The PLC controller is connected to the water inlet area, the gravel packing area, and the polyurethane packing disc area, and is used to control water inlet, aeration, magnetic field strength, and system operation.

[0015] As a preferred option, the water inlet zone is connected to a slightly polluted water source via a water inlet pump and water inlet pipe. The water inlet zone is equipped with evenly distributed water distribution pipes and aeration discs connected to the aeration zone.

[0016] A preferred feature is that the gravel filling zone is filled with nZVI@SiO2 and gravel in a volume ratio of 1:(2-5), and a pressure detector and a strong magnet are provided on the top of the gravel filling zone.

[0017] As a preferred option, the aeration zone is equipped with aeration pipes, which are connected to the aeration discs and the aerator.

[0018] Preferably, the polyurethane packing disc area is equipped with a pollutant detection system and a strong magnet, as well as several modified polyurethane packing discs arranged in an array, which are mounted on a steel frame.

[0019] Preferably, the polyurethane packing disc 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 adhesive polyethylene in water at a volume ratio of 1:(10-50), then place it in a water bath and stir at a temperature of 60-80℃ to dissolve it, thus obtaining a glue-like polyvinyl alcohol.

[0022] c. Apply polyvinyl alcohol evenly to the hydrophilic polyurethane foam using a brush, distribute the adhesive within the polyurethane foam by squeezing, and squeeze out any excess adhesive.

[0023] d. According to the mass ratio (3~10):1, silica-coated nano-zero valent iron powder is dissolved in deoxygenated water, stirred and sonicated to prepare a silica-coated nano-zero valent iron suspension.

[0024] e, based on a volume of 1–2 ml / cm³ 3 Spray a suspension of nano-zero ferric oxide coated with silica onto each polyurethane sponge coated with polyvinyl alcohol, and then vacuum dry the polyurethane sponge.

[0025] f. Before use, soak the dried modified polyurethane sponge in 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, the polyurethane sponge is placed in a vacuum oven and dried at a temperature of 40-60℃ for 12-24 hours;

[0028] In step f, the dried modified polyurethane sponge is immersed in a solution with a concentration of 10... 9 ~10 10 Add aerobic denitrifying bacteria solution containing cells / mL for 2–4 hours.

[0029] Preferably, a sludge discharge pipe is provided at the bottom of the sludge discharge zone, and a water distribution plate is provided at the top of the sludge discharge zone and the bottom of the polyurethane packing disc zone. The sludge discharge zones on both sides of the water distribution plate are designed as arc-shaped transition surfaces.

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

[0031] Modified polyurethane packing discs are threaded through a steel frame in the polyurethane packing disc area;

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

[0033] The slightly polluted water first enters the gravel packing zone, where a uniformly mixed nZVI@SiO2 and gravel are filled; the magnetic field strength at the center of the control 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.

[0034] The slightly polluted water after degradation is aerated and oxygenated in the aeration zone, while the aeration discs in the inlet area are connected to the aeration zone for backwashing.

[0035] Under the combined action of aerobic denitrifying microorganisms and biofilm-forming denitrifying microorganisms in the polyurethane packing tray, as well as a strong magnetic field, the anaerobic denitrifying water undergoes microbial denitrification, generating sediment.

[0036] Water that has undergone enhanced denitrification is discharged through the effluent area; treated sludge is discharged through the sludge discharge area.

[0037] Preferably, the influent nitrate nitrogen concentration is controlled at 4.23–10.26 mg / L and the total nitrogen concentration is controlled at 5.36–12.03 mg / L; the influent flow rate is controlled at 12 L / h.

[0038] The magnetic field strength 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 residence time of the entire device is 8 to 10 hours.

[0041] The present invention, by adopting the above technical solution, has the following beneficial effects:

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

[0043] 2. The treated water is aerated in the aeration zone to provide the necessary dissolved oxygen for subsequent reactions. Then, the water flows into the polyurethane packing disc area, where microorganisms and a magnetic field stimulate the nitrate pollutants to be treated synergistically.

[0044] 3. The stimulating effect of the magnetic field plays a crucial role in the entire denitrification process. On the one hand, the magnetic field enhances the metabolic activity of denitrifying bacteria, thereby accelerating the denitrification reaction; on the other hand, the magnetic field improves the substrate transfer efficiency during denitrification, further promoting the reaction rate. This device achieves organic synergy by integrating the magnetic field, inorganic electron donors, and aerobic denitrifying bacteria, thus significantly improving the denitrification efficiency in each zone. The magnetic field in the polyurethane packing disc area can alter the microbial community structure, slowing down the cycle of forming a highly efficient biofilm on the modified polyurethane sponge. Simultaneously, the magnetic field can also promote the utilization of inorganic electrons on the modified polyurethane sponge by aerobic microorganisms, enhancing electron transfer efficiency and thus more effectively promoting the denitrification process in the water.

[0045] 4. The device of this invention is equipped with a pressure detector to monitor the pressure in the nZVI@SiO2 gravel packing zone. When the pressure exceeds the standard, the system will control the opening of the aeration disc and water distribution plate for backwashing via a signal, while simultaneously shutting off the inlet water pump. The backwash wastewater flows out from the sludge discharge zone. If the detected effluent water does not meet the standards, the inlet water pump will be shut off, and the polyurethane sponge packing disc will be replaced. Attached Figure Description

[0046] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0047] Figure 1 This is a front view schematic diagram of the enhanced denitrification device based on the combined use of magnetic field and modified polyurethane composite material proposed in this invention;

[0048] Figure 2 This is an AA cross-sectional view of the enhanced denitrification device based on the combined use of magnetic field and modified polyurethane composite material proposed in this invention;

[0049] Figure 3 This is a BB cross-sectional view of the enhanced denitrification device based on the combined use of magnetic field and modified polyurethane composite material proposed in this invention;

[0050] Figure 4 This is a CC cross-sectional view of the enhanced denitrification device based on the combined use of magnetic field and modified polyurethane composite material proposed in this invention.

[0051] Figure 5 This is a detailed drawing of the polyurethane packing disc of the enhanced denitrification device based on the combined use of magnetic field and modified polyurethane composite material proposed in this invention.

[0052] In the diagram: 1-Inlet pump; 2-Inlet pipe; 3-Inlet zone; 4-Gravel packing; 5-Aeration zone; 6-Strong magnet; 7-Polyurethane packing disc area; 8-Outlet pipe; 9-Pollutant detection system; 10-Modified polyurethane packing disc; 11-Steel frame; 12-Aeration pipe; 13-Pressure sensor; 14-PLC controller; 15-Sludge discharge zone; 16-Water distribution plate; 17-Sludge discharge pipe; 18-Aeration disc; 19-Water distribution pipe; 20-Aerator; 21-Solenoid valve. Detailed Implementation

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

[0054] like Figure 1 As shown, this embodiment of the invention provides a nitrogen removal device based on a magnetic field-modified polyurethane composite material, comprising an inlet zone 3, a gravel packing zone 4, an aeration zone 5, a polyurethane packing disc zone 7, a sludge discharge zone 15, and an outlet zone 8. The inlet zone 3, gravel packing zone 4, aeration zone 5, and polyurethane packing disc zone 7 are distributed sequentially from bottom to top. The sludge discharge zone 15 is located in the middle of the aeration zone 5, gravel packing zone 4, and inlet zone 3, below the polyurethane packing disc zone 7. The outlet zone 8 is located at the top of the device.

[0055] Slightly polluted water is connected to the inlet zone 3 via inlet pump 1 and inlet pipe 2. Inlet zone 3 is equipped with evenly distributed distribution pipes 19, and the inlet flow rate is controlled by inlet pump 1. Inlet zone 3 is also equipped with aeration discs 18 connected to aeration zone 5 for backwashing. The distribution of aeration discs 18 is shown in [details omitted]. Figure 4 As shown.

[0056] Above the water inlet zone 3 is the gravel packing zone 4, which is filled with nZVI@SiO2 and gravel in a volume ratio of 1:(2-5). A pressure detector 13 is installed at the top of the gravel packing zone 4 to monitor the pressure in real time.

[0057] Above the gravel packing area 4 is the aeration area 5, which is equipped with aeration pipes 12. These pipes 12 and aeration discs 18 are connected to an aerator 20 for oxygenation and aeration. A solenoid valve 21 is installed on the connecting pipes. The distribution of the aeration pipes 12 is shown in the diagram. Figure 3 As shown.

[0058] Above aeration zone 5 is polyurethane packing disc zone 7, which contains several modified polyurethane packing discs 10. These modified polyurethane packing discs 10 are mounted on a steel frame 11 and arranged in an array. The polyurethane packing discs are as follows: Figure 5 As shown, the outer perimeter is made of wire mesh, with holes for the steel frame to pass through in the middle. The structure of polyurethane packing tray area 7 is shown below. Figure 2 As shown.

[0059] The polyurethane filler tray 7 is also equipped with a contaminant detection system 9.

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

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

[0062] The bottom of the sludge discharge zone 15 is provided with a sludge discharge pipe 17, and the top of the sludge discharge zone 15 and the bottom of the polyurethane packing disc zone 7 are provided with a water distribution plate 16. The sludge discharge zones 15 on both sides of the water distribution plate 16 are set as arc-shaped transition surfaces.

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

[0064] The polyurethane packing tray is filled with 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 adhesive polyethylene in water at a volume ratio of 1:(10-50), then place it in a water bath and stir at a temperature of 60-80℃ to dissolve it, thus obtaining a glue-like polyvinyl alcohol.

[0067] Step 3: Use a brush to evenly apply polyvinyl alcohol to the hydrophilic polyurethane foam, and squeeze to distribute the adhesive within the polyurethane foam, and squeeze out any excess adhesive.

[0068] Step 4: Dissolve silica-coated nano-zero valent iron powder in deoxygenated water at a mass ratio of (3-10):1, stir and sonicate 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 onto a polyurethane sponge coated with polyvinyl alcohol. The volume of silica-coated nano-zero-valent iron suspension sprayed onto each polyurethane sponge surface is 1–2 ml / cm³. 3 Place the polyurethane foam in a vacuum oven and dry it at a temperature of 40-60℃ for 12-24 hours.

[0070] Step 6: Before use, soak the dried modified polyurethane sponge in a solution with a concentration of 10... 9 ~10 10Use after 2-4 hours in an aerobic denitrifying bacteria solution containing cells / mL, and then fill it into a polyurethane packing tray.

[0071] Each time the modified polyurethane packing disc needs to be replaced, turn off the inlet pump 1 and open the water distribution plate 16. The detached microbial film and residual sludge can be discharged through the sludge discharge pipe 17, which can also be used as an empty pipe.

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

[0073] Slightly polluted water first enters the gravel packing zone, where anaerobic denitrification occurs under the combined action of a magnetic field and slowly released inorganic electrons, degrading some organic matter and nitrates. Then, it enters the aeration zone where oxygen is introduced through aeration pipes before proceeding to the polyurethane packing disc zone. There, under the combined action of highly efficient aerobic denitrifying microorganisms fixed on the modified polyurethane sponge packing discs and denitrifying microorganisms formed by biofilm formation, the slowly released inorganic electrons from nZVI@SiO2 fixed on the polyurethane sponge are used by the microorganisms for denitrification, further removing organic matter and nitrates. 3+ It can also combine with phosphate to form precipitates, removing phosphate from slightly polluted water. Furthermore, under the influence of an external magnetic field, the field promotes the proliferation of aerobic denitrifying bacteria and alters the microbial community structure, making denitrification-promoting bacteria dominant. Simultaneously, the magnetic field enhances the metabolic activity of denitrifying bacteria, accelerating nitrate reduction and thus increasing the denitrification rate. If the pressure detector detects excessive pressure in the nZVI@SiO2 gravel packing zone, it will control the opening of the aeration discs and water distribution plate for backwashing, while simultaneously shutting off the inlet pump and opening the water distribution plate. The backwash wastewater flows out from the sludge discharge zone. If the effluent does not meet standards, the inlet pump is shut off, and the polyurethane sponge packing discs are replaced. The entire denitrification process takes place under the stimulation of a magnetic field, which enhances the metabolic activity of denitrifying bacteria, accelerates nitrate reduction, and affects the electron transport chain in microbial cells, influencing the rate constant of the chemical reaction during denitrification. This achieves organic synergy between the magnetic field, inorganic electron donors, and aerobic denitrifying bacteria, thereby improving the denitrification effect in each zone.

[0074] This invention also provides a method for enhanced denitrification using a magnetic field-modified polyurethane composite material-based enhanced denitrification device, comprising the following steps:

[0075] S101, modified polyurethane packing discs are threaded through the steel frame in the polyurethane packing disc area;

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

[0077] S103, the slightly polluted water first enters the gravel packing zone 4, where the uniformly mixed nZVI@SiO2 and gravel are filled in a volume ratio of 1:(2~5); the magnetic field strength at the center of the device is 18~20mT; 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 zone 4 and the slow-release inorganic electrons of nZVI@SiO2 in the gravel packing zone 4, degrading some of the organic matter and nitrates;

[0078] S104, the slightly polluted water after degradation enters the aeration zone 5, is oxygenated through the aeration pipe 12, and then enters the polyurethane packing disc zone 7; at the same time, the aeration disc 18 in the water inlet zone 3 is connected to the aeration zone 5 for backflushing; the aeration disc 18 is controlled by the PLC controller 14. When the pressure exceeds a certain value, the PLC controller controls the opening of the solenoid valve 21 to backflush through the aeration disc 18, and at the same time controls the water inlet pump to stop water intake;

[0079] S105, in the polyurethane packing area 7, the aerobic denitrifying microorganisms fixed on the modified polyurethane sponge packing disc 10 and the denitrifying microorganisms formed by biofilm formation, under the combined action of the strong magnetic field strength of the magnet 6, are fixed on the polyurethane sponge. The slow-release inorganic electrons of nZVI@SiO2 are used by the microorganisms for denitrification, further removing organic matter and nitrates. 3+ It can also combine with phosphate to form precipitates, removing phosphate from slightly polluted water; at the same time, under the action of a magnetic field, it can enhance the metabolic activity of denitrifying bacteria, accelerate the reduction of nitrate, and thus increase the denitrification rate.

[0080] S106, the hydraulic retention time of the entire device is 8-10 hours. When the nitrate level in the water after denitrification is not up to standard, the pollutant detection system 9 transmits a signal to PLC 14. The PLC shuts down the inlet pump and replaces the modified polyurethane packing disc 10. After replacing the modified polyurethane packing disc 10, the detached biofilm is discharged from the sludge discharge area 15 by opening the water distribution plate 16. The water after denitrification is discharged through the effluent pipe in the effluent area 8.

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

[0082] Example 1:

[0083] 1) Modified polyurethane packing discs are threaded through the steel frame in the polyurethane packing disc area.

[0084] Modified polyurethane packing discs are prepared according to the following steps:

[0085] Clean and dry the hydrophilic polyurethane sponge for later use;

[0086] The adhesive polyethylene was dissolved in water at a mass ratio of 1:30, and then placed in a water bath at a temperature of 80°C and stirred to dissolve, thus obtaining a glue-like polyvinyl alcohol.

[0087] Apply polyvinyl alcohol evenly to the hydrophilic polyurethane foam using a brush, distribute the adhesive within the polyurethane foam by squeezing, and squeeze out any excess adhesive.

[0088] A silica-coated nano-zero valent iron powder was dissolved in deoxygenated water at a mass ratio of 3:1, stirred and sonicated to prepare a silica-coated nano-zero valent iron suspension with a concentration of 0.4 mg / L.

[0089] A silica-coated nano-zero-valent iron suspension was sprayed onto a polyurethane sponge coated with polyvinyl alcohol. The volume of silica-coated nano-zero-valent iron suspension sprayed onto each polyurethane sponge surface was 2 ml / cm³. 3 The polyurethane sponge was placed in a vacuum oven and dried at 50°C for 18 hours.

[0090] Before use, soak the dried modified polyurethane sponge in a solution with a concentration of 10. 9 ~10 10 After being placed in an aerobic denitrifying bacteria solution containing cells / mL for a certain period of 3 hours, it is used and then filled into a polyurethane packing tray.

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

[0092] 3) In the gravel packing zone, the uniformly mixed nZVI@SiO2 and gravel are filled in a volume ratio of 1:3; the magnetic field strength at the center of the device is 18mT; the slightly polluted water body undergoes anaerobic denitrification in the gravel packing zone 4 to degrade some of the organic matter and nitrates.

[0093] 4) The water is oxygenated through the aeration pipe and then enters the polyurethane packing disc area; at the same time, the aeration disc in the inlet area is connected to the aeration zone for backwashing.

[0094] 5) The biological acclimatization time is 20 days, and the hydraulic residence time of the entire device is 8 hours.

[0095] In this embodiment, the nitrate nitrogen concentration in the effluent from 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) Modified polyurethane packing discs are threaded through the steel frame in the polyurethane packing disc area.

[0098] Modified polyurethane packing discs are prepared according to the following steps:

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

[0100] The adhesive polyethylene was dissolved in water at a mass ratio of 1:50, and then placed in a water bath at a temperature of 60°C and stirred to dissolve, thus obtaining a glue-like polyvinyl alcohol.

[0101] Apply polyvinyl alcohol evenly to the hydrophilic polyurethane foam using a brush, distribute the adhesive within the polyurethane foam by squeezing, and squeeze out any excess adhesive.

[0102] A silica-coated nano-zero valent iron powder was dissolved in deoxygenated water at a mass ratio of 10:1, stirred and sonicated to prepare a silica-coated nano-zero valent iron suspension with a concentration of 0.3 mg / L.

[0103] A silica-coated nano-zero-valent iron suspension was sprayed onto a polyurethane sponge coated with polyvinyl alcohol. The volume of silica-coated nano-zero-valent iron suspension sprayed onto each polyurethane sponge surface was 1 ml / cm³. 3 The polyurethane sponge was placed in a vacuum oven and dried at 60°C for 12 hours.

[0104] Before use, soak the dried modified polyurethane sponge in a solution with a concentration of 10. 9 ~10 10 After being placed in an aerobic denitrifying bacteria solution containing cells / mL for a certain period of 4 hours, it is used and then filled into a polyurethane packing tray.

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

[0106] 3) In the gravel packing zone, the uniformly mixed nZVI@SiO2 and gravel are filled in a volume ratio of 1:2; the magnetic field strength at the center of the device is 19mT; the slightly polluted water body undergoes anaerobic denitrification in the gravel packing zone 4 to degrade some of the organic matter and nitrates.

[0107] 4) The water is oxygenated through the aeration pipe and then enters the polyurethane packing disc area; at the same time, the aeration disc in the inlet area is connected to the aeration zone for backwashing.

[0108] 5) The biological acclimatization time is 20 days, and the hydraulic residence time of the entire device is 8 hours.

[0109] In this embodiment, the nitrate nitrogen concentration in the effluent from 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) Modified polyurethane packing discs are threaded through the steel frame in the polyurethane packing disc area.

[0112] Modified polyurethane packing discs are prepared according to the following steps:

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

[0114] The adhesive polyethylene was dissolved in water at a mass ratio of 1:10, and then placed in a water bath at a temperature of 70°C and stirred to dissolve, thus obtaining a glue-like polyvinyl alcohol.

[0115] Apply polyvinyl alcohol evenly to the hydrophilic polyurethane foam using a brush, distribute the adhesive within the polyurethane foam by squeezing, and squeeze out any excess adhesive.

[0116] A silica-coated nano-zero valent iron powder was dissolved in deoxygenated water at a mass ratio of 7:1, stirred and sonicated to prepare a silica-coated nano-zero valent iron suspension with a concentration of 0.5 mg / L.

[0117] A silica-coated nano-zero-valent iron suspension was sprayed onto polyurethane foam coated with polyvinyl alcohol. The volume of silica-coated nano-zero-valent iron suspension sprayed onto each polyurethane foam surface was 1.5 ml / cm³. 3 The polyurethane sponge was placed in a vacuum oven and dried at 40°C for 24 hours.

[0118] Before use, soak the dried modified polyurethane sponge in a solution with a concentration of 10. 9 ~10 10 After being placed in an aerobic denitrifying bacteria solution containing cells / mL for a certain period of 2 hours, it is used and then filled into a polyurethane packing tray.

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

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

[0121] 4) The water is oxygenated through the aeration pipe and then enters the polyurethane packing disc area; at the same time, the aeration disc in the inlet area is connected to the aeration zone for backwashing.

[0122] 5) The biological acclimatization time is 20 days, and the hydraulic residence time of the entire device is 8 hours.

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

[0124] As can be seen from the above embodiments, the enhanced denitrification device based on the combined use of magnetic field and modified polyurethane composite material of the present invention can achieve efficient removal of nitrate nitrogen and total nitrogen in slightly polluted water bodies. The effluent nitrate nitrogen concentration ranges from 0.45 to 2.93 mg / L, and the effluent total nitrogen concentration ranges from 1.79 to 4.65 mg / L. The average nitrate nitrogen removal rate is 71% to 95%, with a maximum of 95%; the average total nitrogen removal rate is 62% to 85%, with a maximum of 85%. This device has a significant denitrification effect, consumes no energy, has a long service life, and high stability. It is applicable to the field of efficient denitrification technology for slightly polluted water bodies.

[0125] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A denitrification device based on the combined use of magnetic field and modified polyurethane composite material, characterized in that, include The inlet area, located at the bottom of the device, is used to control the inlet flow rate of slightly polluted water and is equipped with aeration discs. The aeration discs are connected to the aeration zone for backwashing. The gravel packing zone, located above the inlet zone, is equipped with nZVI@SiO2, gravel, and strong magnets. It is used to perform anaerobic denitrification of slightly polluted water under the action of a strong magnetic field, degrading some of the organic matter and nitrates. The aeration zone, located above the gravel packing zone, is used to aerate and oxygenate the anaerobic denitrification water. The polyurethane packing disc area, located above the aeration zone, is equipped with modified polyurethane sponge packing discs for aerobic denitrification and microbial denitrification of the aerated water, generating sludge sedimentation. The modified polyurethane sponge is prepared by spraying a silica-coated nano-zero-valent iron suspension onto a polyurethane sponge coated with polyvinyl alcohol. The sludge discharge zone, located in the middle of the aeration zone, gravel packing zone, and inlet zone below the polyurethane packing disc zone, is used to discharge the generated sludge. The effluent zone, located at the top of the device, is used to store the effluent from aerobic denitrification and microbial denitrification. The PLC controller is connected to the water inlet area, the gravel packing area, and the polyurethane packing disc area, and is used to control water inlet, aeration, magnetic field strength, and system operation.

2. The denitrification device based on the combined use of magnetic field and modified polyurethane composite material as described in claim 1, characterized in that, The water intake zone is connected to a slightly polluted water source via a water intake pump and water intake pipe. The water intake zone is equipped with evenly distributed water distribution pipes and aeration discs that are connected to the aeration zone.

3. The denitrification device based on the combined use of magnetic field and modified polyurethane composite material as described in claim 1, characterized in that, The gravel packing zone is filled with nZVI@SiO2 and gravel in a volume ratio of 1:(2~5), and a pressure detector and a strong magnet are installed at the top of the gravel packing zone.

4. The denitrification device based on the combined use of magnetic field and modified polyurethane composite material as described in claim 1, characterized in that, The aeration zone is equipped with aeration pipes, and the aeration pipes and aeration discs are connected to the aerator.

5. The denitrification device based on the combined use of magnetic field and modified polyurethane composite material as described in claim 1, characterized in that, The polyurethane packing disc area is equipped with a pollutant detection system and a strong magnet, as well as several modified polyurethane packing discs arranged in an array, which are mounted on a steel frame.

6. The denitrification device based on the combined use of magnetic field and modified polyurethane composite material as described in claim 5, characterized in that, The modified polyurethane filling tray is filled with modified polyurethane sponge. The preparation and filling method includes the following steps: a. Clean and dry the hydrophilic polyurethane sponge for later use; b. Dissolve the adhesive polyvinyl alcohol in water at a volume ratio of 1:(10~50), then place it in a water bath and stir at a temperature of 60~80℃ to dissolve it, thus obtaining a glue-like polyvinyl alcohol. c. Apply polyvinyl alcohol evenly to the hydrophilic polyurethane foam using a brush, distribute the adhesive within the polyurethane foam by squeezing, and squeeze out any excess adhesive. d. Dissolve silica-coated nano-zero-valent iron powder in deoxygenated water at a mass ratio of (3~10):1, stir and sonicate to prepare a silica-coated nano-zero-valent iron suspension. e, 1-2 ml / cm by volume 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 the polyurethane packing tray.

7. The denitrification device based on the combined use of magnetic field and modified polyurethane composite material as described in claim 6, 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 and dried at a temperature of 40-60℃ for 12-24 hours; In step f, the dried modified polyurethane sponge is immersed in a solution with a concentration of 10... 9 ~10 10 Add aerobic denitrifying bacteria solution containing cells / mL for 2-4 hours.

8. The denitrification device based on the combined use of magnetic field and modified polyurethane composite material as described in claim 1, characterized in that, The bottom of the sludge discharge zone is equipped with a sludge discharge pipe, and the top of the sludge discharge zone and the bottom of the polyurethane packing disc zone are equipped with water distribution plates. The sludge discharge zones on both sides of the water distribution plates are designed with arc-shaped transition surfaces.

9. A method for enhanced denitrification based on a magnetic field-modified polyurethane composite material enhanced denitrification device as described in any one of claims 1-8, characterized in that, include: Modified polyurethane packing discs are threaded through a steel frame in the polyurethane packing disc area; Control the nitrate nitrogen concentration, total nitrogen concentration, and influent flow rate of the slightly polluted influent; The slightly polluted water first enters the gravel packing zone, where a uniformly mixed nZVI@SiO2 and gravel are filled; the magnetic field strength at the center of the control 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 slightly polluted water after degradation is aerated and oxygenated in the aeration zone, while the aeration discs in the inlet area are connected to the aeration zone for backwashing. Under the combined action of aerobic denitrifying microorganisms and biofilm-forming denitrifying microorganisms in the polyurethane packing tray, as well as a strong magnetic field, the anaerobic denitrifying water undergoes microbial denitrification, generating sediment. The water body, after enhanced denitrification, is discharged through the effluent area; The treated sludge is discharged through the sludge discharge area.

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

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