Denitrification biological carriers, their preparation methods and applications

Abstract

This invention discloses a denitrification biological carrier, its preparation method, and its application. The raw materials for preparing the denitrification biological carrier include an iron agent, modified activated carbon, polycaprolactone, sodium dodecyl sulfate, and a hydrogel binder. The modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride-modified activated carbon. The iron agent not only removes dissolved oxygen from water but also reduces total nitrogen in wastewater. The modified activated carbon improves its adsorption affinity for nitrogen-containing compounds. Polycaprolactone serves as a slow-release carbon source for denitrification, exhibiting high carbon source utilization. Sodium dodecyl sulfate, through its foaming properties, together with the modified activated carbon, iron agent, and polycaprolactone, forms a high-mechanical-strength, rough, and porous biological carrier structure, providing excellent attachment conditions for heterotrophic denitrifying bacteria. Therefore, applying the denitrification biological carrier of this invention to wastewater treatment systems can achieve good nitrogen removal efficiency and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and particularly relates to a denitrification biological carrier, its preparation method, and its application. Background Technology

[0002] With the intensification of socio-economic activities, the discharge of nutrients such as nitrogen and phosphorus has continued to increase, leading to prominent eutrophication problems in water bodies. Nitrogen pollutants are one of the key factors causing eutrophication, therefore, reducing the nitrogen content in wastewater is of great significance for environmental protection. Regarding the treatment of nitrogen-containing wastewater, wastewater treatment plants generally implement the Class A standard in the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002), in which the TN concentration shall not exceed 15 mg / L.

[0003] Secondary effluent from wastewater treatment plants typically exhibits a low C / N ratio, making nitrogen removal by heterotrophic microorganisms alone insufficient to achieve the desired effect. To enhance nitrogen removal in secondary effluent, favorable environmental conditions are necessary for heterotrophic microorganisms. According to relevant research, environmental factors influencing the denitrification rate of heterotrophic microorganisms include temperature, dissolved oxygen, pH, and carbon source organic matter. Currently, the most common method for adding carbon source organic matter is in liquid form, but this method suffers from high consumption and easy depletion, resulting in low carbon source utilization. Furthermore, under normal circumstances, the dissolved oxygen in the effluent from the secondary sedimentation tank is generally 2–5 mg / L, while the ideal denitrification environment requires a dissolved oxygen concentration below 0.5 mg / L. To initiate denitrification, current technologies often require increasing the reflux ratio or the volume of the denitrification tank to reduce dissolved oxygen levels. However, this not only increases energy consumption and the footprint of the nitrification tank but also results in unsatisfactory nitrogen removal. In addition, existing denitrification biological carriers suffer from unstable microbial attachment.

[0004] Therefore, there is an urgent need for a denitrification biological carrier, its preparation method, and its application to solve the problems encountered in the existing denitrification process, such as low carbon source utilization, difficulty in reducing dissolved oxygen, unstable microbial attachment, and unsatisfactory denitrification effect. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a denitrification biological carrier, its preparation method and application, which can slowly release solid carbon sources, reduce dissolved oxygen in wastewater, provide good attachment for microorganisms, and have good adsorption affinity for nitrogen.

[0006] To achieve the above objectives, the first aspect of the present invention provides a denitrification biological carrier, the raw materials for which include an iron agent, modified activated carbon, polycaprolactone, sodium dodecyl sulfonate, and a hydrogel binder, wherein the modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon.

[0007] Compared with existing technologies, the raw materials for preparing the denitrification biological carrier of the present invention include iron, 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon, polycaprolactone, and sodium dodecyl sulfonate. The iron not only removes dissolved oxygen from the water, thus providing an anaerobic environment for denitrifying bacteria, but also gradually transforms into iron salt flocculants during its oxidation process, thereby further reducing total phosphorus and other pollutants in wastewater. The surface of the 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon has positively charged quaternary ammonium groups, which can react with negatively charged NO3- in the water. - PO4 3- The strong electrostatic interactions between ions enhance the adsorption affinity of activated carbon for nitrogen- and phosphorus-containing compounds. Polycaprolactone, as a carbon source in the denitrification process, exists in solid form compared to water-soluble liquid carbon sources (such as glucose). Its dissolution and diffusion rates in water are slower, reducing carbon source loss. Furthermore, the relatively slow and controllable degradation rate of polycaprolactone allows for a more uniform and sustained supply of organic carbon, thus improving carbon source utilization and contributing to higher total nitrogen removal rates. In addition, sodium dodecyl sulfate, an anionic surfactant with excellent foaming properties, forms a high-mechanical-strength, rough, and porous biological carrier structure with modified activated carbon, iron agents, and polycaprolactone. This provides excellent attachment conditions for heterotrophic denitrifying bacteria, helping to maintain microbial biomass and activity, thereby improving denitrification efficiency and the removal of other pollutants. Therefore, the denitrification biological carrier of the present invention can slowly release solid carbon sources, reduce dissolved oxygen in wastewater, provide good attachment for microorganisms, and have good adsorption affinity for nitrogen. Thus, applying the denitrification biological carrier of the present invention to wastewater treatment systems can achieve good denitrification effect and economy.

[0008] Further, the raw materials for preparation of the present invention, by weight, include 20-50 parts of iron agent, 20-50 parts of modified activated carbon, 10-30 parts of polycaprolactone, 5-10 parts of sodium dodecyl sulfate, and 65-130 parts of hydrogel binder. Specifically, the iron agent may be, but is not limited to, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, or 50 parts; the modified activated carbon may be, but is not limited to, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, or 50 parts; the polycaprolactone may be, but is not limited to, 10 parts, 15 parts, 20 parts, 25 parts, or 30 parts; the sodium dodecyl sulfate may be, but is not limited to, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts; and the hydrogel binder may be, but is not limited to, 65 parts, 75 parts, 85 parts, 95 parts, 110 parts, 120 parts, or 130 parts.

[0009] Further, the hydrogel binder of the present invention comprises 10-20 parts by weight of polyvinyl alcohol, 5-10 parts by weight of sodium alginate, and 50-100 parts by weight of water. The polyvinyl alcohol may be, but is not limited to, 10 parts, 12 parts, 15 parts, 18 parts, or 20 parts; the sodium alginate may be, but is not limited to, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts; and the water may be, but is not limited to, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, or 100 parts.

[0010] Furthermore, the preparation of the hydrogel adhesive of the present invention includes mixing polyvinyl alcohol, sodium alginate and water, and dissolving them by heating in a water bath at 80-100°C.

[0011] Furthermore, the iron agent of the present invention includes at least one of sponge iron, zero-valent iron, and iron powder. Sponge iron is metallic iron produced by reducing hematite with carbon monoxide at high temperature. Sponge iron has a porous structure, varying particle sizes, and a large specific surface area, thus exhibiting excellent adsorption properties. Therefore, sponge iron is preferably used as the iron agent of the present invention.

[0012] Further, the preparation of the modified activated carbon of the present invention includes: mixing activated carbon, 3-chloro-2-hydroxypropyltrimethylammonium chloride and water, heating and reacting in a water bath at 40-50°C, and then sequentially filtering, washing, drying, grinding, and sieving. Specifically, the water bath heating reaction at 40-50°C includes: shaking the reaction in a water bath shaker at 100-400 r / min for 10-15 h at 40-50°C; washing includes washing at least 3 times with a 25% ethanol solution, followed by washing at least 3 times with water; drying includes drying at 38-42°C; and sieving includes sieving through a 60-mesh sieve. 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) is a commonly used quaternizing agent containing a positively charged quaternary ammonium group (N). + The CHPTAC molecule has a side chain with a reactive hydroxyl group (-OH). The hydroxyl group in the CHPTAC molecule undergoes esterification or etherification with oxygen-containing functional groups (such as carboxyl, phenolic, hydroxyl groups, etc.) on the surface of activated carbon under water bath heating to form covalent bonds, thus obtaining modified activated carbon.

[0013] Further, by mass parts, it includes 20 to 50 parts activated carbon, 40 to 80 parts 3-chloro-2-hydroxypropyltrimethylammonium chloride, and 50 to 120 parts water.

[0014] Accordingly, a second aspect of the present invention provides a method for preparing a denitrification biological carrier, comprising the following steps:

[0015] (1) Mix the iron agent, modified activated carbon, polycaprolactone, sodium dodecyl sulfonate and hydrogel binder.

[0016] (2) The mixture obtained after step (1) is dried, ground and sieved in sequence;

[0017] (3) Mix the product obtained after step (2) with a saturated aluminum chloride solution and then shake in a water bath;

[0018] (4) The product obtained after step (3) is washed and dried in sequence.

[0019] Furthermore, the drying in steps (2) and (4) of the present invention includes drying at 38 to 42°C.

[0020] Furthermore, in step (2) of the present invention, sieving includes sieving using a 60-mesh sieve.

[0021] Furthermore, in step (3) of the present invention, the temperature of the water bath oscillation is room temperature, and the time is 20-30 hours.

[0022] Accordingly, the third aspect of the present invention also provides the application of the aforementioned denitrifying biological carrier or the denitrifying biological carrier prepared by the aforementioned method in a wastewater treatment system.

[0023] Compared with the prior art, the denitrification biological carrier of the present invention can reduce dissolved oxygen in wastewater, provide good attachment for microorganisms, and have good adsorption affinity for nitrogen. Therefore, applying the denitrification biological carrier of the present invention to the wastewater treatment system can ensure that the wastewater treatment system has a good denitrification effect. At the same time, the denitrification biological carrier of the present invention can slowly release solid carbon source, thus reducing the loss of denitrification biological carrier and significantly improving the economy of wastewater treatment system. Detailed Implementation

[0024] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0025] Example 1

[0026] This embodiment provides a denitrification biological carrier, which, by weight, comprises 25 parts sponge iron, 35 parts modified activated carbon, 25 parts polycaprolactone, 5 parts sodium dodecyl sulfonate, and 100 parts hydrogel binder. The hydrogel binder comprises 15 parts polyvinyl alcohol, 5 parts sodium alginate, and 80 parts water. The modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon.

[0027] The preparation of the hydrogel adhesive includes: mixing polyvinyl alcohol, sodium alginate and water, and dissolving them by heating in a water bath at 90°C;

[0028] The preparation of modified activated carbon includes: mixing 20 parts of activated carbon, 60 parts of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 100 parts of water, and shaking the mixture in a water bath shaker at 45°C at a speed of 200 r / min for 12 h, then washing it three times with 25% ethanol solution, washing it three times with water, drying it at 40°C, grinding it, and passing it through a 60-mesh sieve.

[0029] This embodiment provides a method for preparing a denitrification biological carrier, including the following steps:

[0030] (1) Mix the sponge iron, modified activated carbon, polycaprolactone, sodium dodecyl sulfonate and hydrogel binder.

[0031] (2) The mixture obtained after step (1) is dried, ground and passed through a 60-mesh sieve at 40°C in sequence;

[0032] (3) The product obtained after step (2) is mixed with a saturated aluminum chloride solution and then shaken in a water bath at room temperature for 24 hours;

[0033] (4) The product obtained after step (3) is washed with water three times and dried at 38°C to obtain a denitrification biological carrier.

[0034] Example 2

[0035] This embodiment provides a denitrification biological carrier. By weight, the raw materials include 35 parts sponge iron, 45 parts modified activated carbon, 15 parts polycaprolactone, 7 parts sodium dodecyl sulfonate, and 116 parts hydrogel binder. The hydrogel binder includes 18 parts polyvinyl alcohol, 8 parts sodium alginate, and 90 parts water. The modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon.

[0036] The preparation of the hydrogel adhesive includes: mixing polyvinyl alcohol, sodium alginate and water, and dissolving them by heating in a water bath at 97°C;

[0037] The preparation of modified activated carbon includes: mixing 30 parts of activated carbon, 70 parts of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 110 parts of water, and shaking the mixture in a 50°C water bath shaker at a speed of 300 r / min for 14 h. Then, the mixture is washed 4 times with 25% ethanol solution, washed 3 times with water, dried at 40°C, ground, and passed through a 60-mesh sieve.

[0038] This embodiment provides a method for preparing a denitrification biological carrier, including the following steps:

[0039] (1) Mix the iron agent, modified activated carbon, polycaprolactone, sodium dodecyl sulfonate and hydrogel binder.

[0040] (2) The mixture obtained after step (1) is dried, ground and passed through a 60-mesh sieve at 38°C in sequence;

[0041] (3) The product obtained after step (2) is mixed with a saturated aluminum chloride solution and then shaken in a water bath at room temperature for 27 hours;

[0042] (4) The product obtained after step (3) is washed with water three times and dried at 40°C to obtain a denitrification biological carrier.

[0043] Example 3

[0044] This embodiment provides a denitrification biological carrier, which, by weight, comprises 45 parts sponge iron, 50 parts modified activated carbon, 20 parts polycaprolactone, 9 parts sodium dodecyl sulfonate, and 95 parts hydrogel binder. The hydrogel binder comprises 12 parts polyvinyl alcohol, 8 parts sodium alginate, and 75 parts water. The modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon.

[0045] The preparation of the hydrogel adhesive includes: mixing polyvinyl alcohol, sodium alginate and water, and dissolving them by heating in a water bath at 85°C;

[0046] The preparation of modified activated carbon includes: mixing 35 parts of activated carbon, 70 parts of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 115 parts of water, and reacting them in a water bath shaker at 46℃ with a rotation speed of 300 r / min for 11 h. Then, the mixture is washed 4 times with 25% ethanol solution, washed 4 times with water, dried at 40℃, ground, and passed through a 60-mesh sieve.

[0047] This embodiment provides a method for preparing a denitrification biological carrier, including the following steps:

[0048] (1) Mix the iron agent, modified activated carbon, polycaprolactone, sodium dodecyl sulfonate and hydrogel binder.

[0049] (2) The mixture obtained after step (1) is dried, ground and passed through a 60-mesh sieve at 41°C in sequence;

[0050] (3) The product obtained after step (2) is mixed with a saturated aluminum chloride solution and then shaken in a water bath at room temperature for 23 hours;

[0051] (4) The product obtained after step (3) is washed with water three times and dried at 40°C to obtain a denitrification biological carrier.

[0052] Comparative Example 1

[0053] This comparative example provides a denitrification biological carrier, which, by weight, comprises 25 parts sponge iron, 35 parts activated carbon, 25 parts polycaprolactone, 5 parts sodium dodecyl sulfonate, and 100 parts hydrogel binder, which comprises 15 parts polyvinyl alcohol, 5 parts sodium alginate, and 80 parts water.

[0054] The preparation of the hydrogel adhesive includes mixing polyvinyl alcohol, sodium alginate and water, and then heating and dissolving them in a water bath at 90°C.

[0055] This comparative example provides a method for preparing a denitrification biological carrier, including the following steps:

[0056] (1) Mix the sponge iron, activated carbon, polycaprolactone, sodium dodecyl sulfonate and hydrogel binder.

[0057] (2) The mixture obtained after step (1) is dried, ground and passed through a 60-mesh sieve at 40°C in sequence;

[0058] (3) The product obtained after step (2) is mixed with a saturated aluminum chloride solution and then shaken in a water bath at room temperature for 24 hours;

[0059] (4) The product obtained after step (3) is washed with water three times and dried at 38°C to obtain a denitrification biological carrier.

[0060] Comparative Example 2

[0061] This comparative example provides a denitrification biological carrier, which, by weight, comprises 35 parts modified activated carbon, 25 parts polycaprolactone, 5 parts sodium dodecyl sulfonate, and 100 parts hydrogel binder. The hydrogel binder comprises 15 parts polyvinyl alcohol, 5 parts sodium alginate, and 80 parts water. The modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon.

[0062] The preparation of the hydrogel adhesive includes: mixing polyvinyl alcohol, sodium alginate and water, and dissolving them by heating in a water bath at 90°C;

[0063] The preparation of modified activated carbon includes: mixing 20 parts of activated carbon, 60 parts of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 100 parts of water, and shaking the mixture in a water bath shaker at 45°C at a speed of 200 r / min for 12 h, then washing it three times with 25% ethanol solution, washing it three times with water, drying it at 40°C, grinding it, and passing it through a 60-mesh sieve.

[0064] This comparative example provides a method for preparing a denitrification biological carrier, including the following steps:

[0065] (1) Mix the modified activated carbon, polycaprolactone, sodium dodecyl sulfonate and hydrogel binder.

[0066] (2) The mixture obtained after step (1) is dried, ground and passed through a 60-mesh sieve at 40°C in sequence;

[0067] (3) The product obtained after step (2) is mixed with a saturated aluminum chloride solution and then shaken in a water bath at room temperature for 24 hours;

[0068] (4) The product obtained after step (3) is washed with water three times and dried at 38°C to obtain a denitrification biological carrier.

[0069] Comparative Example 3

[0070] This comparative example provides a denitrification biological carrier. By weight, the raw materials include 25 parts sponge iron, 25 parts polycaprolactone, 5 parts sodium dodecyl sulfonate, and 100 parts hydrogel binder. The hydrogel binder includes 15 parts polyvinyl alcohol, 5 parts sodium alginate, and 80 parts water. The modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon.

[0071] The preparation of the hydrogel adhesive includes: mixing polyvinyl alcohol, sodium alginate and water, and dissolving them by heating in a water bath at 90°C;

[0072] This comparative example provides a method for preparing a denitrification biological carrier, including the following steps:

[0073] (1) Mix the sponge iron, polycaprolactone, sodium dodecyl sulfate and hydrogel binder.

[0074] (2) The mixture obtained after step (1) is dried, ground and passed through a 60-mesh sieve at 40°C in sequence;

[0075] (3) The product obtained after step (2) is mixed with a saturated aluminum chloride solution and then shaken in a water bath at room temperature for 24 hours;

[0076] (4) The product obtained after step (3) is washed with water three times and dried at 38°C to obtain a denitrification biological carrier.

[0077] Comparative Example 4

[0078] This comparative example provides a denitrification biological carrier. By weight, the raw materials include 25 parts sponge iron, 35 parts modified activated carbon, 25 parts glucose, 5 parts sodium dodecyl sulfonate, and 100 parts hydrogel binder. The hydrogel binder includes 15 parts polyvinyl alcohol, 5 parts sodium alginate, and 80 parts water. The modified activated carbon is 3-chloro-2-hydroxypropyltrimethylammonium chloride modified activated carbon.

[0079] The preparation of the hydrogel adhesive includes: mixing polyvinyl alcohol, sodium alginate and water, and dissolving them by heating in a water bath at 90°C;

[0080] The preparation of modified activated carbon includes: mixing 20 parts of activated carbon, 60 parts of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 100 parts of water, and shaking the mixture in a water bath shaker at 45°C at a speed of 200 r / min for 12 h, then washing it three times with 25% ethanol solution, washing it three times with water, drying it at 40°C, grinding it, and passing it through a 60-mesh sieve.

[0081] This comparative example provides a method for preparing a denitrification biological carrier, including the following steps:

[0082] (1) Mix sponge iron, modified activated carbon, glucose, sodium dodecyl sulfonate and hydrogel binder.

[0083] (2) The mixture obtained after step (1) is dried, ground and passed through a 60-mesh sieve at 40°C in sequence;

[0084] (3) The product obtained after step (2) is mixed with a saturated aluminum chloride solution and then shaken in a water bath at room temperature for 24 hours;

[0085] (4) The product obtained after step (3) is washed with water three times and dried at 38°C to obtain a denitrification biological carrier.

[0086] The denitrifying biological carriers prepared in Examples 1-3 and Comparative Examples 1-4 were simulated in a denitrification tank system. Denitrification tanks are well known to those skilled in the art, including denitrification tanks with a retention time of 3 hours and a surface loading rate of 6 m³ / h. 3 / (m 2 The system includes a sedimentation tank, effluent channel, mixer, dosing pump, and electrical control cabinet (h). In the denitrification system, wastewater is pumped from the secondary sedimentation tank outlet to the denitrification tank system via a lift pump. A denitrifying biological carrier is added to the denitrification tank at a dosage of 50 mg / L. After 3 hours of operation, the wastewater settles in the sedimentation tank, and the supernatant is discharged to the next treatment unit via the effluent channel. The concentration of the supernatant effluent is tested. The removal rates of ammonia nitrogen (NH3-N) and total nitrogen (TN) are calculated as follows: Removal rate (%) = [(Influent concentration - Effluent concentration) / Influent concentration] × 100%. The results are shown in Table 1.

[0087] Table 1

[0088]

[0089] As shown in Table 1, the ammonia nitrogen removal rate of the wastewater in Examples 1-3 after treatment with the denitrification biological carrier of the present invention is much higher than that of the wastewater in Comparative Examples 1-4. This is because the ordinary activated carbon used in Comparative Example 1 has poor adsorption affinity for nitrogen and phosphorus compounds; the removal of iron in Comparative Example 2 resulted in the inability to reduce the dissolved oxygen concentration in the wastewater, and the anoxic environment for denitrifying bacteria could not be guaranteed, thus affecting the removal rate of total nitrogen and ammonia nitrogen in the wastewater; the removal of modified activated carbon in Comparative Example 3 resulted in the inability to adsorb nitrogen and phosphorus compounds in the wastewater, thus affecting the removal rate of total nitrogen and ammonia nitrogen; and the replacement of solid carbon source polycaprolactone with liquid carbon source glucose in Comparative Example 4 resulted in a faster dissolution and diffusion rate of liquid carbon source glucose in water, leading to a greater loss of carbon source, which in turn affected the removal rate of total nitrogen and ammonia nitrogen. Furthermore, comparing Example 1 with Comparative Examples 1-4, it can be seen that removing any one of the modified activated carbon, iron agent, or polycaprolactone, or adjusting the type of any one of the modified activated carbon, iron agent, or polycaprolactone, cannot form a biocarrier structure with high mechanical strength and a rough, porous structure. This affects the attachment of heterotrophic denitrifying bacteria, is not conducive to maintaining microbial biomass and activity, and thus leads to a decrease in denitrification efficiency. This also shows that the denitrification biocarrier of the present invention can significantly improve denitrification efficiency through the synergistic effect between modified activated carbon, iron agent, and polycaprolactone.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A denitrifying bio-carrier, characterized in that, The preparation raw materials include iron agent, modified activated carbon, polycaprolactone, sodium dodecyl sulfonate, hydrogel binder, the modified activated carbon is 3-chloro-2-hydroxypropyl trimethyl ammonium chloride modified activated carbon, and the iron agent is sponge iron.

2. The denitrifying bio-carriers of claim 1, wherein The preparation raw materials include 20-50 parts of the iron agent, 20-50 parts of the modified activated carbon, 10-30 parts of the polycaprolactone, 5-10 parts of the sodium dodecyl sulfonate, and 65-130 parts of the hydrogel binder.

3. The denitrifying bio-carriers of claim 1, wherein, The hydrogel binder includes 10-20 parts of polyvinyl alcohol, 5-10 parts of sodium alginate, and 50-100 parts of water.

4. The denitrifying bio-carriers of claim 3, wherein, The preparation of the hydrogel binder includes mixing the polyvinyl alcohol, the sodium alginate, and the water, and dissolving by water bath heating at 80-100 DEG C.

5. The denitrifying bio-carriers of claim 1, wherein, The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving.

6. The denitrifying bio-carriers of claim 5, wherein, The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving.

7. The method of producing a denitrifying bio-carrier according to any one of claims 1 to 6, wherein The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving.

8. The method for preparing a denitrifying bio-carrier of claim 7, wherein the step of immobilizing the denitrifying bacteria on the carrier is performed by mixing the carrier with the denitrifying bacteria in a culture medium and then culturing the mixture in a bioreactor. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, and water, and reacting by water bath heating at 40-50 DEG C, and then sequentially filtering, washing, drying, grinding, and sieving. The preparation of the modified activated carbon includes mixing activated carbon,

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