Sulfur autotrophic denitrification expanded bed and advanced sewage denitrification method thereof

Abstract

This invention relates to a sulfur autotrophic denitrification expanded bed and its deep denitrification method for wastewater, belonging to the field of deep wastewater treatment technology. It includes an inlet device, a reflux device inlet, a reflux device outlet, a first sampling port, a second sampling port, and a drain outlet. The interior of the device, from bottom to top, consists of a pebble layer, a packing layer, and a clear water layer. In this invention, a layered double hydroxide-bentonite composite material is used to reinforce the packing material. After being coated with elemental sulfur, it is combined with hydroxyl polyethylene glycol mercapto groups to obtain modified denitrification packing. The sulfur autotrophic denitrification expanded bed is filled with this modified packing. By optimizing the packing particle size and controlling the reflux ratio, the expansion rate is varied, reflecting that smaller particle size packing can effectively increase the denitrification rate and improve denitrification efficiency. The expanded bed process can effectively enhance the removal of nitrate nitrogen, ammonia nitrogen, and total phosphorus from wastewater, improving the denitrification performance of the sulfur autotrophic denitrification expanded bed.

Description

Technical Field

[0001] This invention relates to the field of advanced wastewater treatment technology, specifically to a sulfur autotrophic denitrification expanded bed and its advanced wastewater denitrification method. Background Technology

[0002] Nitrogen, as one of the main causes of eutrophication, has long been a major concern. Currently, the nitrogen capacity of most ecological water bodies is approaching saturation, teetering on the edge of eutrophication outbreaks. While the nutrient content (such as nitrate nitrogen, ammonia nitrogen, and phosphate) in the secondary treated effluent from wastewater treatment plants is relatively low, it is still sufficient to cause eutrophication in natural water bodies. Due to the limited self-purification capacity of water bodies, gradually increasing the total nitrogen emission limits of surrounding wastewater discharge units is a powerful measure to prevent further deterioration of water quality. Sulfur autotrophic denitrification technology is currently a highly regarded nitrogen removal technology, mainly due to the low cost of elemental sulfur and its outstanding advantages of acting as both an electron donor and a biological carrier. The main compatible processes for sulfur autotrophic denitrification technology are packed bed and fluidized bed processes. The limited nitrogen removal capacity of packed bed processes makes it difficult to meet increasingly stringent emission standards, while the high nitrogen removal capacity of fluidized bed processes may lead to resource waste under low-concentration influent conditions. Therefore, a low-cost, high-efficiency, and flexible sulfur autotrophic denitrification expanded bed process has been developed.

[0003] In existing technologies, the packing material in sulfur autotrophic denitrification expanded bed processes typically includes elemental sulfur and inorganic carbon sources. During the denitrification reaction, the low adhesion rate of denitrifying bacteria (such as denitrifying thiobacillus) to the packing surface leads to a low reaction rate. Furthermore, the insufficient strength of the packing material makes it prone to loss under the impact of water flow such as backwashing, increasing operating costs. In addition, elemental sulfur is poorly soluble in water, resulting in low solubility and thus a low mass transfer rate in the expanded bed system, which in turn affects the overall denitrification efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a sulfur autotrophic denitrification expanded bed and its deep denitrification method for wastewater. The method involves loading a layered double hydroxide-bentonite composite material onto a reinforcing packing, then coating it with elemental sulfur, and finally combining it with hydroxyl polyethylene glycol mercapto groups to obtain a modified denitrification packing. This modified packing is then filled into a sulfur autotrophic denitrification expanded bed to achieve deep denitrification of wastewater. The overall denitrification efficiency of the sulfur autotrophic denitrification expanded bed is improved, effectively increasing the removal efficiency of nitrate nitrogen, ammonia nitrogen, and total phosphorus in wastewater. Furthermore, it increases the adhesion rate of denitrifying bacteria on the surface of the modified denitrification packing, enhances the strength of the packing, reduces operating costs, and improves the overall performance of the sulfur autotrophic denitrification expanded bed.

[0005] The technical problem this invention aims to solve is as follows: In the prior art, the packing material in the sulfur autotrophic denitrification expanded bed process typically includes elemental sulfur and inorganic carbon sources. During the denitrification reaction, the low adhesion rate of denitrifying bacteria (such as denitrifying thiobacillus) on the surface of the packing material leads to a low reaction rate. Furthermore, the packing material is not strong enough and is easily damaged by water flow impacts such as backwashing, increasing operating costs. In addition, elemental sulfur is poorly soluble in water and has low solubility in water, resulting in a low mass transfer rate in the expanded bed system, which in turn affects the overall denitrification efficiency.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A sulfur autotrophic denitrification expanded bed includes an inlet device, a reflux device inlet, a reflux device outlet, a first sampling port, a second sampling port, and a drain outlet. The interior of the device consists of a pebble layer, a packing layer, and a clear water layer from bottom to top.

[0008] The packing layer is formed by filling with modified denitrification packing;

[0009] The preparation method of the modified denitrification packing includes the following steps:

[0010] S1: A composite material was obtained by loading the reinforcing filler with a layered double hydroxide-bentonite composite material;

[0011] S2: The composite material is coated with elemental sulfur to obtain denitrification filler;

[0012] S3: Combine denitrifying packing with hydroxyl polyethylene glycol mercapto groups to obtain modified denitrifying packing.

[0013] Furthermore, step S1 specifically includes:

[0014] The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed and stirred for 25-35 min. The mixture was then reacted at 115-125℃ for 11-13 h. After the reaction was completed, deionized water was added and the mixture was centrifuged for 5-10 min. The mixture was then filtered, washed with deionized water, and finally dried at 55-65℃ to obtain the composite material.

[0015] In the above reaction process, the layered double hydroxide-bentonite composite material has a high specific surface area and pore structure, which can provide a large number of adsorption sites. The reinforcing filler is loaded onto the layered double hydroxide-bentonite composite material through electrostatic adsorption or hydrogen bonding interaction, and finally the composite is obtained.

[0016] Furthermore, the mass ratio of the reinforcing filler, the layered double hydroxide-bentonite composite material, and the deionized water is 0.8-1.2:0.8-1.2:30-40.

[0017] Furthermore, the reinforcing filler is composed of iron powder, manganese dioxide and tourmaline powder mixed in a mass ratio of 1-1.2:0.5-0.6:0.3-0.4.

[0018] Furthermore, the preparation method of the layered double hydroxide-bentonite composite material includes the following steps:

[0019] Magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water were mixed evenly to obtain a mixed solution. Sodium-based bentonite was added to the mixed solution and stirred evenly. The mixture was then heated to 75-85℃, and sodium hydroxide solution was added to adjust the pH of the system to 10-11. The mixture was stirred for 1.5-2.5 hours and aged at 75-85℃ for 15-17 hours. The mixture was then filtered through a filter membrane, washed with deionized water, and finally dried at 75-85℃ to obtain a layered double hydroxide-bentonite composite material.

[0020] In the above reaction process, magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate and sodium chloride can be mixed to form layered double hydroxides. The layered double hydroxides and sodium-based bentonite are combined by in-situ co-precipitation to finally obtain a layered double hydroxide-bentonite composite material.

[0021] Furthermore, the mass ratio of magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water is 1.8-2.2:1.8-2.2:0.8-1.2:3.8-4.2:280-320.

[0022] Furthermore, the mass ratio of the sodium-based bentonite to the mixed solution is 2.5-3.5:6.5-7.5.

[0023] Furthermore, the filter membrane is a 0.45 μm polyethersulfone membrane.

[0024] Furthermore, step S2 specifically involves:

[0025] The composite, binder, and deionized water from step S1 are mixed evenly, then granulated to form spheres, dried at 95-105℃ for 1-2 hours, cooled to room temperature, and then heated to 200-220℃ under a nitrogen atmosphere and held for 1.5-2.5 hours to obtain component A. Elemental sulfur is heated under a nitrogen atmosphere and stirred for 25-35 minutes to obtain a molten sulfur solution. Component A is immersed in the molten sulfur solution for 25-35 minutes, removed, and cooled to room temperature to obtain the denitrification packing.

[0026] Furthermore, the mass ratio of the composite, the adhesive, and the deionized water is 0.8-1.2:0.04-0.06:50-60.

[0027] Furthermore, the granulation forms spheres of 1-2 mm in size.

[0028] Furthermore, the adhesive is sodium carboxymethyl cellulose.

[0029] Furthermore, the elemental sulfur is heated to 120-130°C under a nitrogen atmosphere.

[0030] Furthermore, the mass ratio of component A to the molten sulfur solution is 1:1.5.

[0031] Furthermore, step S3 specifically includes:

[0032] Hydroxyethylene glycol mercapto groups were added to anhydrous ethanol and stirred for 20-30 min. Then, the denitrification packing material from step S2 was added, and the mixture was stirred for 5-7 h under a nitrogen atmosphere and in a constant temperature water bath. After the reaction was completed, the mixture was filtered, washed with anhydrous ethanol and deionized water, and finally dried under vacuum at 50-60 °C to obtain the modified denitrification packing material.

[0033] In the above reaction process, the hydroxyl polyethylene glycol thiol group has thiol and hydroxyl groups, and the surface of the denitrification packing has sulfur atoms. The thiol group in the hydroxyl polyethylene glycol thiol group can form a disulfide bond with the sulfur atoms on the denitrification packing through oxidative coupling. The hydroxyl polyethylene glycol thiol group is grafted onto the surface of the denitrification packing, and finally the modified denitrification packing is obtained.

[0034] Furthermore, the mass ratio of the hydroxyl polyethylene glycol mercapto group, anhydrous ethanol, and denitrification filler is 0.8-1.2:20-30:1.8-2.2.

[0035] Furthermore, the temperature of the constant temperature water bath is 55-65℃.

[0036] A method for deep nitrogen removal from wastewater using a sulfur-autotrophic denitrification expanded bed includes the following steps:

[0037] A1. Start the sulfur autotrophic denitrification function: Start the water inlet device, close the inlet and outlet of the reflux device, and let the wastewater containing pollutants enter the sulfur autotrophic denitrification expanded bed. Control the water inlet flow rate to the empty bed residence time of the packing layer to be 0.5-1.5h.

[0038] A2. Start-up of the sulfur autotrophic denitrification expanded bed is completed: During the operation of the sulfur autotrophic denitrification expanded bed, the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent are sampled and tested until the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent reach a stable state, at which point the start-up of the sulfur autotrophic denitrification expanded bed is completed.

[0039] A3. After the sulfur autotrophic denitrification expanded bed is started, control the influent flow rate to ensure that the empty bed residence time of the packing layer is 0.5-1.5h. Open the inlet and outlet of the reflux device to allow the packing material in the packing layer of the sulfur autotrophic denitrification expanded bed to expand. Then, input the wastewater containing pollutants to be treated into the sulfur autotrophic denitrification expanded bed through the influent device. Take samples to test the concentration of nitrate nitrogen, ammonia nitrogen and total phosphorus in the effluent at the outlet.

[0040] Furthermore, in step A1, the wastewater containing pollutants is wastewater containing nitrate nitrogen, ammonia nitrogen, and total phosphorus.

[0041] Furthermore, the nitrate nitrogen concentration in the wastewater containing nitrate nitrogen, ammonia nitrogen, and total phosphorus is 20 mg / L, the ammonia nitrogen concentration is 1.5 mg / L, and the total phosphorus concentration is 2 mg / L.

[0042] Furthermore, in step A1, the pH value of the wastewater containing pollutants is controlled to be 7.4-7.6.

[0043] Furthermore, in step A3, the inlet and outlet of the reflux device are opened, and the reflux ratio of the reflux flow rate to the inlet flow rate in the sulfur autotrophic denitrification expanded bed is controlled to be 100%-5000%.

[0044] The beneficial effects of this invention are:

[0045] (1) In the technical solution of this invention, the reinforcing packing is loaded with a layered double hydroxide-bentonite composite material to obtain a composite. In the layered double hydroxide-bentonite composite material, both the layered double hydroxide and bentonite have a layered structure and a large specific surface area and pore structure, which can provide a large number of adsorption sites. The layered double hydroxide has good compositional stability, a positively charged surface, high chemical stability and excellent nitrate adsorption. Bentonite has the characteristics of low cost, large specific surface area and large cation exchange capacity, and also has good adsorption. Combining the layered double hydroxide and bentonite, the two play a synergistic role, which not only has good adsorption and enhances the removal efficiency of nitrogen and phosphorus, but also can better load the reinforcing packing and further improve the denitrification efficiency of the modified denitrification packing. The reinforcing packing is composed of iron powder, manganese dioxide and tourmaline powder. The three have It exhibits good synergistic effects, improving denitrification efficiency and enhancing the removal of nitrate nitrogen, ammonia nitrogen, and total phosphorus from wastewater. Iron powder can act as an electron donor, promoting the denitrification process. Manganese dioxide can directly participate in electron transfer during microbial denitrification, achieving nitrogen conversion and removal. The unique electrical properties of tourmaline powder can promote microbial enrichment and denitrification performance. Loading the reinforcing packing onto the layered double hydroxide-bentonite composite material increases its specific surface area and mechanical strength, further improving the denitrification efficiency of the modified denitrification packing. By coating the composite with elemental sulfur, a denitrification packing is obtained. Elemental sulfur can coat the surface of the composite, forming a sulfur shell with a porous structure, thus forming a porous core-shell structure. This structure helps improve the long-term stability of the sulfur autotrophic denitrification process, further enhancing the overall denitrification efficiency during denitrification.

[0046] (2) In the technical solution of the present invention, a modified denitrification packing is obtained by combining the denitrification packing with hydroxyl polyethylene glycol thiol. The hydroxyl polyethylene glycol thiol is grafted onto the surface of the denitrification packing through chemical action, which enhances its binding force. The hydroxyl polyethylene glycol thiol can not only increase the solubility of the sulfur shell on the surface of the denitrification packing in water and improve its hydrophilicity, but also facilitate the attachment of denitrifying bacteria on the surface of the packing. At the same time, it maintains the integrity of the porous structure and improves the strength of the denitrification packing, further enhancing the denitrification efficiency of the packing in the denitrification process. Filling the modified denitrification packing into the sulfur autotrophic denitrification expanded bed can effectively improve the removal effect of nitrate nitrogen, ammonia nitrogen and total phosphorus in wastewater, and enhance the denitrification efficiency of the sulfur autotrophic denitrification expanded bed.

[0047] (3) In the technical solution of the present invention, modified denitrification packing is filled into the sulfur autotrophic denitrification expanded bed. By optimizing the particle size of the packing and controlling the reflux ratio, the expansion rate can be changed. The particle size of the prepared modified denitrification packing is 1-2 mm. When it is filled into the sulfur autotrophic denitrification expanded bed, the removal effect of nitrate nitrogen, ammonia nitrogen and total phosphorus in wastewater can be improved. It can be seen that the smaller particle size of the packing can effectively increase the denitrification rate of the expanded bed and further improve its denitrification efficiency. At the same time, through the operation of the sulfur autotrophic denitrification expanded bed, the loss of packing can be effectively reduced, the operating cost can be reduced, and the overall performance of the sulfur autotrophic denitrification expanded bed can be further improved.

[0048] (4) In the technical solution of the present invention, the reinforcing packing is loaded with layered double hydroxide-bentonite composite material, then coated with elemental sulfur, and then combined with hydroxyl polyethylene glycol mercapto to obtain modified denitrification packing; the modified denitrification packing is filled into a sulfur autotrophic denitrification expanded bed to finally obtain a sulfur autotrophic denitrification expanded bed, which can achieve deep denitrification of wastewater; the overall removal efficiency of nitrate nitrogen, ammonia nitrogen and total phosphorus in wastewater is improved, the denitrification efficiency of sulfur autotrophic denitrification expanded bed is improved, and the adhesion rate of denitrifying bacteria on the surface of modified denitrification packing is increased, while the strength and stability of the packing are enhanced, and its overall comprehensive performance is good. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of the sulfur autotrophic denitrification expanded bed and its deep denitrification method for wastewater in this invention.

[0051] Figure reference numerals: 1. Water inlet device; 2. Water inlet of reflux device; 5. Water outlet of reflux device; 3. First sampling port; 4. Second sampling port; 6. Drainage outlet; 7. Gravel layer; 8. Packing layer; 9. Clear water layer. Detailed Implementation

[0052] The following will combine Figure 1 The technical solutions of the present invention have been clearly and completely described in the accompanying embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] The specific parameters of the raw materials used in this invention are as follows:

[0054] Iron powder, 200 mesh, provided by Gongyi Jinding Powder Metallurgy Co., Ltd.; Manganese dioxide, CAS No.: 1313-13-9, provided by Jiangsu Runfeng Synthetic Technology Co., Ltd.; Tourmaline powder, 10-20 mesh, provided by Lingshou Hengshuo Mineral Products Co., Ltd.; Sodium-based bentonite, provided by Xinyang Zhengheng New Building Materials Co., Ltd., washed with deionized water before use, dried at 80℃ for 10 hours, then ground and screened through a 100-mesh sieve; Hydroxyethylene glycol mercaptoyl groups, provided by Shaanxi Xingbei Aike Biotechnology Co., Ltd.

[0055] Example 1

[0056] The specific steps for preparing modified denitrification packing are as follows:

[0057] S1: The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed in a mass ratio of 0.8:0.8:30 and stirred for 25 min. The mixture was then reacted at 115℃ for 11 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 4500 rpm for 10 min. After filtration, the mixture was washed three times with deionized water (each time with 40% of the deionized water mass mentioned above). Finally, the mixture was dried at 55℃ for 24 h to obtain the composite material. The reinforcing filler was composed of iron powder, manganese dioxide, and tourmaline powder mixed in a mass ratio of 1:0.5:0.3.

[0058] The preparation method of layered double hydroxide-bentonite composite material includes the following steps:

[0059] Magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water were mixed evenly in a mass ratio of 1.8:1.8:0.8:3.8:280 to obtain a mixed solution. Sodium-based bentonite was added to the mixed solution in a mass ratio of 2.5:6.5 and stirred evenly. The mixture was then heated to 75°C, and a 3 mol / L sodium hydroxide solution was added to adjust the pH to 10. The mixture was stirred for 1.5 hours and aged at 75°C for 15 hours. The mixture was then filtered through a 0.45 μm polyethersulfone membrane and washed with deionized water (5% of the total deionized water mass). Finally, the mixture was dried at 75°C for 9 hours to obtain a layered double hydroxide-bentonite composite material.

[0060] S2: The complex, sodium carboxymethyl cellulose, and deionized water in step S1 are mixed evenly according to a mass ratio of 0.8:0.04:50. The mixture is then granulated to form 1 mm spheres (granulation speed is 30 rpm). The spheres are dried at 95°C for 1 h, cooled to room temperature, and then heated to 200°C under a nitrogen atmosphere and held for 1.5 h to obtain component A. Elemental sulfur is heated to 120°C under a nitrogen atmosphere and stirred at 200 rpm for 35 min to obtain a molten sulfur solution. Component A is immersed in the molten sulfur solution for 25 min according to a mass ratio of 1:1.5. The molten sulfur solution is then removed and cooled to room temperature to obtain the denitrification packing.

[0061] S3: The hydroxyl polyethylene glycol mercapto group, anhydrous ethanol, and denitrification packing were added to anhydrous ethanol at a mass ratio of 0.8:20:1.8 and stirred for 20 min. Then the denitrification packing from step S2 was added, and the mixture was stirred at 100 rpm for 7 h under a nitrogen atmosphere and in a constant temperature water bath at 55 °C. After the reaction was completed, the mixture was filtered and washed three times each with anhydrous ethanol and deionized water (each time the mass of anhydrous ethanol was 40% of the mass of the above anhydrous ethanol, and each time the mass of deionized water was 60% of the mass of the above anhydrous ethanol). Finally, the mixture was vacuum dried at 50 °C for 11 h to obtain the modified denitrification packing.

[0062] A sulfur autotrophic denitrification expanded bed includes an inlet device 1, a reflux device inlet 2, a reflux device outlet 5, a first sampling port 3, a second sampling port 4, and a drain outlet 6. The interior of the device consists of a pebble layer 7, a packing layer 8, and a clear water layer 9 from bottom to top. The inlet device 1 is connected to the pebble layer 7. The top of the pebble layer 7 is successively connected to the packing layer 8 and the clear water layer 9. One end of the reflux device outlet 5 is connected to the clear water layer 9. One end of the reflux device inlet 2 is connected to the bottom of the packing layer 8, and the reflux device inlet 2 is connected to the reflux device outlet 5. The drain outlet 6 is located above the clear water layer. The first sampling port 3 and the second sampling port 4 are located on one side of the middle section of the packing layer 8, and the second sampling port 4 is located above the first sampling port 3.

[0063] A method for deep nitrogen removal from wastewater using a sulfur-autotrophic denitrification expanded bed includes the following steps:

[0064] A1. Start the sulfur autotrophic denitrification function: Start the inlet device 1, close the inlet 2 and outlet 5 of the reflux device, and let the wastewater containing nitrate nitrogen, ammonia nitrogen and total phosphorus enter the sulfur autotrophic denitrification expanded bed. Control the inlet flow rate to the empty bed residence time of the packing layer 8 to be 0.5h. The concentration of nitrate nitrogen in the wastewater is 20mg / L, the concentration of ammonia nitrogen is 1.5mg / L, the concentration of total phosphorus is 2mg / L, and the pH value of the wastewater is controlled to be 7.4.

[0065] A2. Start-up of the sulfur autotrophic denitrification expanded bed is completed: During the operation of the sulfur autotrophic denitrification expanded bed, the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent from outlet 6 are sampled and tested every 24 hours. The start-up of the sulfur autotrophic denitrification expanded bed is completed when the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent decrease by 90% and there is no accumulation of nitrite nitrogen, and the concentrations remain stable for more than 48 hours.

[0066] A3. After the sulfur autotrophic denitrification expanded bed is started up, control the influent flow rate to ensure that the empty bed residence time of the packing layer 8 is 0.5h. Open the inlet 2 and outlet 5 of the reflux device, and control the reflux flow rate to influent flow rate ratio in the sulfur autotrophic denitrification expanded bed to be 1000%, so that the packing in the packing layer 8 of the sulfur autotrophic denitrification expanded bed expands. Then, input the wastewater containing nitrate nitrogen, ammonia nitrogen and total phosphorus to be treated into the sulfur autotrophic denitrification expanded bed through the influent device 1. Take samples every 24h to test the concentration of nitrate nitrogen, ammonia nitrogen and total phosphorus in the effluent of the outlet 6.

[0067] Example 2

[0068] The specific steps for preparing modified denitrification packing are as follows:

[0069] S1: The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed in a mass ratio of 1:1:35 and stirred for 30 min. The mixture was then reacted at 120℃ for 12 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5000 rpm for 8 min. After filtration, the mixture was washed three times with deionized water (each time with 40% of the deionized water mass mentioned above). Finally, the mixture was dried at 60℃ for 24 h to obtain the composite material. The reinforcing filler was composed of iron powder, manganese dioxide, and tourmaline powder in a mass ratio of 1.1:0.55:0.35.

[0070] The preparation method of layered double hydroxide-bentonite composite material includes the following steps:

[0071] Magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water were mixed evenly in a mass ratio of 2:2:1:4:300 to obtain a mixed solution. Sodium-based bentonite was added to the mixed solution in a mass ratio of 3:7 and stirred evenly. The mixture was then heated to 80°C, and a 3 mol / L sodium hydroxide solution was added to adjust the pH to 10.5. The mixture was stirred for 2 hours and aged at 80°C for 16 hours. The mixture was then filtered through a 0.45 μm polyethersulfone membrane and washed with deionized water (5% of the total deionized water mass). Finally, it was dried at 80°C for 10 hours to obtain a layered double hydroxide-bentonite composite material.

[0072] S2: The complex, sodium carboxymethyl cellulose, and deionized water in step S1 are mixed evenly according to a mass ratio of 1:0.05:55. The mixture is then granulated to form 1.5 mm spheres (granulation speed of 40 rpm). The spheres are dried at 100°C for 1.5 h, cooled to room temperature, and then heated to 210°C under a nitrogen atmosphere and held for 2 h to obtain component A. Elemental sulfur is heated to 125°C under a nitrogen atmosphere and stirred at 250 rpm for 30 min to obtain a molten sulfur solution. Component A is immersed in the molten sulfur solution for 30 min according to a mass ratio of 1:1.5. The molten sulfur solution is then removed and cooled to room temperature to obtain the denitrification packing.

[0073] S3: The hydroxyl polyethylene glycol mercapto group, anhydrous ethanol, and denitrification packing were added to anhydrous ethanol at a mass ratio of 1:25:2 and stirred for 25 min. Then, the denitrification packing from step S2 was added, and the mixture was stirred at 150 rpm for 6 h under a nitrogen atmosphere and in a constant temperature water bath at 60 °C. After the reaction was completed, the mixture was filtered and washed three times each with anhydrous ethanol and deionized water (each time the mass of anhydrous ethanol was 40% of the mass of the above anhydrous ethanol, and each time the mass of deionized water was 60% of the mass of the above anhydrous ethanol). Finally, the mixture was vacuum dried at 55 °C for 12 h to obtain the modified denitrification packing.

[0074] A sulfur autotrophic denitrification expanded bed includes an inlet device 1, a reflux device inlet 2, a reflux device outlet 5, a first sampling port 3, a second sampling port 4, and a drain outlet 6. The interior of the device consists of a pebble layer 7, a packing layer 8, and a clear water layer 9 from bottom to top. The inlet device 1 is connected to the pebble layer 7. The top of the pebble layer 7 is successively connected to the packing layer 8 and the clear water layer 9. One end of the reflux device outlet 5 is connected to the clear water layer 9. One end of the reflux device inlet 2 is connected to the bottom of the packing layer 8, and the reflux device inlet 2 is connected to the reflux device outlet 5. The drain outlet 6 is located above the clear water layer. The first sampling port 3 and the second sampling port 4 are located on one side of the middle section of the packing layer 8, and the second sampling port 4 is located above the first sampling port 3.

[0075] A method for deep nitrogen removal from wastewater using a sulfur-autotrophic denitrification expanded bed includes the following steps:

[0076] A1. Start the sulfur autotrophic denitrification function: Start the inlet device 1, close the inlet 2 and outlet 5 of the reflux device, and let the wastewater containing nitrate nitrogen, ammonia nitrogen and total phosphorus enter the sulfur autotrophic denitrification expanded bed. Control the inlet flow rate to the empty bed residence time of the packing layer 8 to 1 hour. The concentration of nitrate nitrogen in the wastewater is 20 mg / L, the concentration of ammonia nitrogen is 1.5 mg / L, the concentration of total phosphorus is 2 mg / L, and the pH value of the wastewater is controlled to be 7.5.

[0077] A2. Start-up of the sulfur autotrophic denitrification expanded bed is completed: During the operation of the sulfur autotrophic denitrification expanded bed, the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent from outlet 6 are sampled and tested every 24 hours. The start-up of the sulfur autotrophic denitrification expanded bed is completed when the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent decrease by 90% and there is no accumulation of nitrite nitrogen, and the concentrations remain stable for more than 48 hours.

[0078] A3. After the sulfur autotrophic denitrification expanded bed is started, control the influent flow rate to ensure that the empty bed residence time of the packing layer 8 is 1 hour. Open the inlet 2 and outlet 5 of the reflux device and control the reflux ratio of the reflux flow rate to the influent flow rate in the sulfur autotrophic denitrification expanded bed to be 1000%, so that the packing in the packing layer 8 of the sulfur autotrophic denitrification expanded bed expands. Then, input the wastewater containing nitrate nitrogen, ammonia nitrogen and total phosphorus to be treated into the sulfur autotrophic denitrification expanded bed through the influent device 1. Take samples every 24 hours to test the concentration of nitrate nitrogen, ammonia nitrogen and total phosphorus in the effluent of the outlet 6.

[0079] Example 3

[0080] The specific steps for preparing modified denitrification packing are as follows:

[0081] S1: The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed in a mass ratio of 1.2:1.2:40 and stirred for 35 min. The mixture was then reacted at 125℃ for 13 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5500 rpm for 5 min. After filtration, the mixture was washed three times with deionized water (each time with 40% of the deionized water mass mentioned above). Finally, the mixture was dried at 65℃ for 24 h to obtain the composite material. The reinforcing filler was composed of iron powder, manganese dioxide, and tourmaline powder in a mass ratio of 1.2:0.6:0.4.

[0082] The preparation method of layered double hydroxide-bentonite composite material includes the following steps:

[0083] The magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water were mixed evenly in a mass ratio of 2.2:2.2:1.2:4.2:320 to obtain a mixed solution. Sodium-based bentonite was added to the mixed solution in a mass ratio of 3.5:7.5 and stirred evenly. The mixture was then heated to 85°C, and a 3 mol / L sodium hydroxide solution was added to adjust the pH to 11. The mixture was stirred for 2.5 hours and aged at 85°C for 17 hours. The solution was then filtered through a 0.45 μm polyethersulfone membrane, washed with deionized water (5% of the total deionized water mass), and finally dried at 85°C for 11 hours to obtain a layered double hydroxide-bentonite composite material.

[0084] S2: The complex, sodium carboxymethyl cellulose, and deionized water in step S1 were mixed evenly according to a mass ratio of 1.2:0.06:60. The mixture was then granulated to form 2 mm spheres (granulation speed of 45 rpm). The spheres were dried at 105 °C for 2 h, cooled to room temperature, and then heated to 220 °C under a nitrogen atmosphere and held for 2.5 h to obtain component A. Elemental sulfur was heated to 130 °C under a nitrogen atmosphere and stirred at 300 rpm for 25 min to obtain a molten sulfur solution. Component A was immersed in the molten sulfur solution for 35 min according to a mass ratio of 1:1.5. The molten sulfur solution was then removed and cooled to room temperature to obtain the denitrification packing.

[0085] S3: The hydroxyl polyethylene glycol mercapto group, anhydrous ethanol, and denitrification packing were added to anhydrous ethanol at a mass ratio of 1.2:30:2.2 and stirred for 30 min. Then the denitrification packing from step S2 was added, and the mixture was stirred at 200 rpm for 5 h under a nitrogen atmosphere and in a constant temperature water bath at 65 °C. After the reaction was completed, the mixture was filtered and washed three times each with anhydrous ethanol and deionized water (each time the mass of anhydrous ethanol was 40% of the mass of the above anhydrous ethanol, and each time the mass of deionized water was 60% of the mass of the above anhydrous ethanol). Finally, the mixture was vacuum dried at 60 °C for 13 h to obtain the modified denitrification packing.

[0086] A sulfur autotrophic denitrification expanded bed includes an inlet device 1, a reflux device inlet 2, a reflux device outlet 5, a first sampling port 3, a second sampling port 4, and a drain outlet 6. The interior of the device consists of a pebble layer 7, a packing layer 8, and a clear water layer 9 from bottom to top. The inlet device 1 is connected to the pebble layer 7. The top of the pebble layer 7 is successively connected to the packing layer 8 and the clear water layer 9. One end of the reflux device outlet 5 is connected to the clear water layer 9. One end of the reflux device inlet 2 is connected to the bottom of the packing layer 8, and the reflux device inlet 2 is connected to the reflux device outlet 5. The drain outlet 6 is located above the clear water layer. The first sampling port 3 and the second sampling port 4 are located on one side of the middle section of the packing layer 8, and the second sampling port 4 is located above the first sampling port 3.

[0087] A method for deep nitrogen removal from wastewater using a sulfur-autotrophic denitrification expanded bed includes the following steps:

[0088] A1. Start the sulfur autotrophic denitrification function: Start the inlet device 1, close the inlet 2 and outlet 5 of the reflux device, and let the wastewater containing nitrate nitrogen, ammonia nitrogen and total phosphorus enter the sulfur autotrophic denitrification expanded bed. Control the inlet flow rate to the empty bed residence time of the packing layer 8 to 1.5h. The concentration of nitrate nitrogen in the wastewater is 20mg / L, the concentration of ammonia nitrogen is 1.5mg / L, the concentration of total phosphorus is 2mg / L, and the pH value of the wastewater is controlled to be 7.6.

[0089] A2. Start-up of the sulfur autotrophic denitrification expanded bed is completed: During the operation of the sulfur autotrophic denitrification expanded bed, the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent from outlet 6 are sampled and tested every 24 hours. The start-up of the sulfur autotrophic denitrification expanded bed is completed when the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent decrease by 90% and there is no accumulation of nitrite nitrogen, and the concentrations remain stable for more than 48 hours.

[0090] A3. After the sulfur autotrophic denitrification expanded bed is started, control the influent flow rate to ensure that the empty bed residence time of the packing layer 8 is 1.5 hours. Open the inlet 2 and outlet 5 of the reflux device and control the reflux ratio of the reflux flow rate to the influent flow rate in the sulfur autotrophic denitrification expanded bed to be 1000%, so that the packing in the packing layer 8 of the sulfur autotrophic denitrification expanded bed expands. Then, input the wastewater containing nitrate nitrogen, ammonia nitrogen and total phosphorus to be treated into the sulfur autotrophic denitrification expanded bed through the influent device 1. Take samples every 24 hours to test the concentration of nitrate nitrogen, ammonia nitrogen and total phosphorus in the effluent of the outlet 6.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 3 is that, in the preparation of the modified denitrification packing, the reinforcing packing in step S1 is composed of a mixture of iron powder and manganese dioxide, while the remaining steps and raw materials are the same as in Example 3.

[0093] S1: The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed in a mass ratio of 1.2:1.2:40 and stirred for 35 min. The mixture was then reacted at 125℃ for 13 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5500 rpm for 5 min. After filtration, the mixture was washed three times with deionized water (each time the mass of deionized water was 40% of the mass of the deionized water mentioned above). Finally, the mixture was dried at 65℃ for 24 h to obtain the composite material. The reinforcing filler was composed of iron powder and manganese dioxide mixed in a mass ratio of 1.2:1.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 3 is that, in the preparation of the modified denitrification packing, the reinforcing packing in step S1 is composed of a mixture of iron powder and tourmaline powder, while the remaining steps and raw materials are the same as in Example 3.

[0096] S1: The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed in a mass ratio of 1.2:1.2:40 and stirred for 35 min. The mixture was then reacted at 125℃ for 13 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5500 rpm for 5 min. After filtration, the mixture was washed three times with deionized water (each time with 40% of the deionized water mass mentioned above). Finally, the mixture was dried at 65℃ for 24 h to obtain the composite material. The reinforcing filler was composed of iron powder and tourmaline powder mixed in a mass ratio of 1.2:1.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 3 is that, in the preparation of the modified denitrification packing, the reinforcing packing in step S1 is composed of a mixture of manganese dioxide and tourmaline powder, while the remaining steps and raw materials are the same as in Example 3.

[0099] S1: The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed in a mass ratio of 1.2:1.2:40 and stirred for 35 min. The mixture was then reacted at 125℃ for 13 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5500 rpm for 5 min. After filtration, the mixture was washed three times with deionized water (each time the mass of deionized water was 40% of the mass of the deionized water mentioned above). Finally, the mixture was dried at 65℃ for 24 h to obtain the composite material. The reinforcing filler was composed of manganese dioxide and tourmaline powder mixed in a mass ratio of 1.2:1.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 3 is that, in the preparation of the modified denitrification packing, the layered double hydroxide-bentonite composite material in step S1 is replaced by an equal mass of layered double hydroxide, while the remaining steps and raw materials are the same as in Example 3.

[0102] S1: The reinforcing filler, layered double hydroxide, and deionized water were mixed in a mass ratio of 1.2:1.2:40 and stirred for 35 min. The mixture was then reacted at 125 °C for 13 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5500 rpm for 5 min. After filtration, the mixture was washed three times with deionized water (each time with 40% of the deionized water mass mentioned above). Finally, the mixture was dried at 65 °C for 24 h to obtain the composite. The reinforcing filler was composed of iron powder, manganese dioxide, and tourmaline powder in a mass ratio of 1.2:0.6:0.4.

[0103] The preparation method of layered double hydroxides includes the following steps:

[0104] The magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water were mixed evenly according to a mass ratio of 2.2:2.2:1.2:4.2:320. The mixture was stirred at room temperature for 2.5 hours, filtered, washed with deionized water (5% of the total mass of the deionized water), and finally dried at 85°C for 11 hours to obtain a layered double hydroxide.

[0105] Comparative Example 5

[0106] The difference between this comparative example and Example 3 is that, in preparing the modified denitrification filler, the layered double hydroxide-bentonite composite material in step S1 is replaced with sodium-based bentonite by an equal mass, and the original preparation method of the layered double hydroxide-bentonite composite material is deleted. The remaining steps and raw materials are the same as in Example 3.

[0107] S1: The reinforcing filler, sodium bentonite, and deionized water were mixed in a mass ratio of 1.2:1.2:40 and stirred for 35 min. The mixture was then reacted at 125℃ for 13 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5500 rpm for 5 min. After filtration, the mixture was washed three times with deionized water (each time the mass of deionized water was 40% of the mass of the deionized water mentioned above). Finally, the mixture was dried at 65℃ for 24 h to obtain the composite. The reinforcing filler was composed of iron powder, manganese dioxide, and tourmaline powder in a mass ratio of 1.2:0.6:0.4.

[0108] Comparative Example 6

[0109] The difference between this comparative example and Example 3 is that, in the preparation of the modified denitrification packing, the elemental sulfur in step S2 is directly mixed with the complex, while the remaining steps and raw materials are the same as in Example 3.

[0110] S2: The complex, sodium carboxymethyl cellulose, and deionized water in step S1 were mixed evenly according to a mass ratio of 1.2:0.06:60. The mixture was then granulated to form 2 mm spheres (granulation speed of 45 rpm). The spheres were dried at 105 °C for 2 h and cooled to room temperature to obtain component A. Component A and elemental sulfur were mixed for 35 min according to a mass ratio of 1:1.5 and cooled to room temperature to obtain denitrification packing.

[0111] Comparative Example 7

[0112] The difference between this comparative example and Example 3 is that, in the preparation of the modified denitrification packing, the hydroxyl polyethylene glycol mercapto group in step S3 is replaced with polyethylene glycol by mass, while the remaining steps and raw materials are the same as in Example 3.

[0113] S3: According to the mass ratio of polyethylene glycol, anhydrous ethanol, and denitrification packing material of 1.2:30:2.2, polyethylene glycol was added to anhydrous ethanol and stirred for 30 min. Then, the denitrification packing material from step S2 was added, and the mixture was stirred at 200 rpm for 5 h under a nitrogen atmosphere and in a constant temperature water bath at 65 °C. After the reaction was completed, the mixture was filtered and washed three times each with anhydrous ethanol and deionized water (each time the mass of anhydrous ethanol was 40% of the mass of the above anhydrous ethanol, and each time the mass of deionized water was 60% of the mass of the above anhydrous ethanol). Finally, the mixture was vacuum dried at 60 °C for 13 h to obtain the modified denitrification packing material.

[0114] Comparative Example 8

[0115] The difference between this comparative example and Example 3 is that, in the preparation of the modified denitrification packing, the complex in step S1 is directly combined with the hydroxyl polyethylene glycol thiol group in step S3, and the original step S2 is deleted. The remaining steps and raw materials are the same as in Example 3.

[0116] The specific steps for preparing modified denitrification packing are as follows:

[0117] S1: The reinforcing filler, layered double hydroxide-bentonite composite material, and deionized water were mixed in a mass ratio of 1.2:1.2:40 and stirred for 35 min. The mixture was then reacted at 125℃ for 13 h. After the reaction was completed, deionized water (with the same mass as the deionized water mentioned above) was added, and the mixture was centrifuged at 5500 rpm for 5 min. After filtration, the mixture was washed three times with deionized water (each time with 40% of the deionized water mass mentioned above). Finally, the mixture was dried at 65℃ for 24 h to obtain the composite material. The reinforcing filler was composed of iron powder, manganese dioxide, and tourmaline powder in a mass ratio of 1.2:0.6:0.4.

[0118] The preparation method of layered double hydroxide-bentonite composite material includes the following steps:

[0119] The magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water were mixed evenly in a mass ratio of 2.2:2.2:1.2:4.2:320 to obtain a mixed solution. Sodium-based bentonite was added to the mixed solution in a mass ratio of 3.5:7.5 and stirred evenly. The mixture was then heated to 85°C, and a 3 mol / L sodium hydroxide solution was added to adjust the pH to 11. The mixture was stirred for 2.5 hours and aged at 85°C for 17 hours. The solution was then filtered through a 0.45 μm polyethersulfone membrane, washed with deionized water (5% of the total deionized water mass), and finally dried at 85°C for 11 hours to obtain a layered double hydroxide-bentonite composite material.

[0120] S2: The hydroxyl polyethylene glycol mercapto group, anhydrous ethanol, and the composite were added to anhydrous ethanol at a mass ratio of 1.2:30:2.2 and stirred for 30 min. Then the composite from step S1 was added, and the mixture was stirred at 200 rpm for 5 h under a nitrogen atmosphere and in a constant temperature water bath at 65 °C. After the reaction was completed, the mixture was filtered and washed three times each with anhydrous ethanol and deionized water (each time the mass of anhydrous ethanol was 40% of the mass of the above anhydrous ethanol, and each time the mass of deionized water was 60% of the mass of the above anhydrous ethanol). Finally, the mixture was vacuum dried at 60 °C for 13 h to obtain the modified denitrification packing.

[0121] The performance of the sulfur autotrophic denitrification expanded beds prepared in Examples 1-3 and Comparative Examples 1-8 was tested. The test method was as follows: Based on the sulfur autotrophic denitrification expanded beds provided in Examples 1-3 and Comparative Examples 1-8, the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the wastewater before treatment were measured. After the wastewater was treated in the system for 10 days, the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the treated wastewater were measured. Then, the removal rates of nitrogen and phosphorus were calculated as follows: Removal rate = (Concentration before treatment - Concentration after treatment) / Concentration before treatment × 100%. Nitrate nitrogen was determined using spectrophotometry, and the concentration of nitrate nitrogen in the wastewater before treatment was 20 mg / L. Ammonia nitrogen was determined using Nessler's reagent colorimetry after distillation, and the concentration of ammonia nitrogen in the wastewater before treatment was 1.5 mg / L. Total phosphorus was determined using ammonium molybdate spectrophotometry, and the concentration of total phosphorus in the wastewater before treatment was 2 mg / L.

[0122] The test results are shown in Table 1 below:

[0123] Table 1 Performance parameters of the sulfur autotrophic denitrification expanded beds prepared in Examples 1-3 and Comparative Examples 1-8

[0124]

[0125] As shown in Table 1 above, and comparing Comparative Examples 1-3 and Example 3, the test results of the sulfur autotrophic denitrification expanded bed prepared by using a reinforcing packing material composed of iron powder and manganese dioxide, or a mixture of iron powder and tourmaline powder, or a mixture of manganese dioxide and tourmaline powder, are worse than those of Example 3. This indicates that the reinforcing packing material composed of iron powder, manganese dioxide, and tourmaline powder can have a synergistic effect, effectively improving the denitrification efficiency in the sulfur autotrophic denitrification process and enhancing the removal effect of nitrate nitrogen, ammonia nitrogen, and total phosphorus in wastewater.

[0126] Comparing Comparative Examples 4-6 and Example 3, it can be seen that replacing the layered double hydroxide-bentonite composite material in step S1 with layered double hydroxide or sodium-based bentonite by the same mass, or directly mixing elemental sulfur with the composite in step S2, and finally preparing a sulfur autotrophic denitrification expanded bed, the test results are worse than those of Example 3. This indicates that combining layered double hydroxide and sodium-based bentonite through in-situ co-precipitation can effectively enhance the bonding force between the two. Moreover, the layered double hydroxide-bentonite composite material formed by the combination of the two can not only support and reinforce the packing, but also provide a large number of adsorption sites, which have good adsorption properties, further improving the denitrification efficiency of the modified denitrification packing. Coating elemental sulfur on the surface of the composite can form a porous core-shell structure, which can not only enhance the strength of the packing, but also improve the stability of the packing, effectively enhancing the removal efficiency of nitrate nitrogen, ammonia nitrogen and total phosphorus in wastewater.

[0127] Comparing Comparative Examples 7-8 and Example 3, it can be seen that replacing the hydroxyl polyethylene glycol thiol groups in step S3 with polyethylene glycol by an equal mass, or directly combining the complex in step S1 with the hydroxyl polyethylene glycol thiol groups in step S3, to prepare a sulfur autotrophic denitrification expanded bed, the test results are worse than those of Example 3. This indicates that coating the complex with elemental sulfur before combining it with hydroxyl polyethylene glycol thiol groups not only improves the strength and stability of the packing material but also increases the binding force between the hydroxyl polyethylene glycol thiol groups and the denitrification packing material. At the same time, the hydroxyl polyethylene glycol thiol groups can effectively improve the solubility of the packing material in water, which is beneficial for the attachment of denitrifying bacteria on the surface of the packing material, further enhancing the nitrogen removal efficiency in the sulfur autotrophic denitrification process and effectively improving the removal effect of nitrate nitrogen, ammonia nitrogen, and total phosphorus in wastewater.

[0128] As shown in Table 1 above, the sulfur autotrophic denitrification expanded beds prepared in Examples 1-3, compared to those prepared in Comparative Examples 1-8, utilize layered double hydroxide-bentonite composite materials to load the reinforcing packing, followed by coating with elemental sulfur and then combining with hydroxyl polyethylene glycol mercapto groups to obtain modified denitrification packing. When this modified packing is filled into the sulfur autotrophic denitrification expanded bed, a deep denitrification of wastewater is achieved, meeting the performance requirements. In contrast, the sulfur autotrophic denitrification expanded beds prepared in Comparative Examples 1-8 did not meet the performance requirements. This indicates that the sulfur autotrophic denitrification expanded bed prepared in this invention can effectively improve the removal efficiency of nitrate nitrogen, ammonia nitrogen, and total phosphorus in wastewater, enhance the denitrification efficiency during the sulfur autotrophic denitrification process, increase the strength and stability of the packing, reduce operating costs, and exhibit better overall performance.

[0129] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0130] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined by the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A sulfur-autotrophic denitrification expanded bed, characterized in that, It includes a water inlet device, a reflux device inlet, a reflux device outlet, a first sampling port, a second sampling port, and a drain outlet. The interior of the device consists of a pebble layer, a packing layer, and a clear water layer from bottom to top. The packing layer is formed by filling with modified denitrification packing; The preparation method of the modified denitrification packing includes the following steps: S1: A composite material was obtained by loading the reinforcing filler with a layered double hydroxide-bentonite composite material; S2: The composite material is coated with elemental sulfur to obtain denitrification filler; S3: Combine denitrification packing with hydroxyl polyethylene glycol mercapto groups to obtain modified denitrification packing; Step S1 is as follows: The reinforcing filler, layered double hydroxide-bentonite composite material and deionized water were mixed and stirred for 25-35 min. Then, the mixture was reacted at 115-125℃ for 11-13 h. After the reaction was completed, deionized water was added and the mixture was centrifuged for 5-10 min. After filtration, the mixture was washed with deionized water and finally dried at 55-65℃ to obtain the composite material. The reinforcing filler is composed of iron powder, manganese dioxide and tourmaline powder mixed in a mass ratio of 1-1.2:0.5-0.6:0.3-0.4; Step S2 is as follows: The composite, binder, and deionized water in step S1 are mixed evenly, then granulated to form spheres, dried at 95-105℃ for 1-2 hours, cooled to room temperature, and heated to 200-220℃ under a nitrogen atmosphere and held for 1.5-2.5 hours to obtain component A. Elemental sulfur is heated under a nitrogen atmosphere and stirred for 25-35 minutes to obtain a molten sulfur solution. Component A is immersed in the molten sulfur solution for 25-35 minutes, removed, and cooled to room temperature to obtain denitrification packing. Step S3 is as follows: Hydroxyethylene glycol mercapto groups were added to anhydrous ethanol and stirred for 20-30 min. Then, the denitrification packing material from step S2 was added, and the mixture was stirred for 5-7 h under a nitrogen atmosphere and in a constant temperature water bath. After the reaction was completed, the mixture was filtered, washed with anhydrous ethanol and deionized water, and finally dried under vacuum at 50-60 °C to obtain the modified denitrification packing material.

2. The sulfur autotrophic denitrification expanded bed according to claim 1, characterized in that, The preparation method of the layered double hydroxide-bentonite composite material includes the following steps: Magnesium chloride hexahydrate, zinc chloride, aluminum chloride hexahydrate, sodium chloride, and deionized water were mixed evenly to obtain a mixed solution. Sodium-based bentonite was added to the mixed solution and stirred evenly. The mixture was then heated to 75-85℃, and sodium hydroxide solution was added to adjust the pH of the system to 10-11. The mixture was stirred for 1.5-2.5 hours and aged at 75-85℃ for 15-17 hours. The mixture was then filtered through a filter membrane, washed with deionized water, and finally dried at 75-85℃ to obtain a layered double hydroxide-bentonite composite material.

3. The sulfur autotrophic denitrification expanded bed according to claim 1, characterized in that, The elemental sulfur is heated to 120-130°C under a nitrogen atmosphere.

4. The sulfur-autotrophic denitrification expanded bed according to claim 1, characterized in that, The temperature of the constant temperature water bath is 55-65℃.

5. A method for deep nitrogen removal from wastewater using a sulfur-autotrophic denitrification expanded bed as described in any one of claims 1-4, characterized in that, Includes the following steps: A1. Start the sulfur autotrophic denitrification function: Start the water inlet device, close the inlet and outlet of the reflux device, and let the wastewater containing pollutants enter the sulfur autotrophic denitrification expanded bed. Control the water inlet flow rate to the empty bed residence time of the packing layer to be 0.5-1.5h. A2. Start-up of the sulfur autotrophic denitrification expanded bed is completed: During the operation of the sulfur autotrophic denitrification expanded bed, the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent are sampled and tested until the concentrations of nitrate nitrogen, ammonia nitrogen, and total phosphorus in the effluent reach a stable state, at which point the start-up of the sulfur autotrophic denitrification expanded bed is completed. A3. After the sulfur autotrophic denitrification expanded bed is started, control the influent flow rate to ensure that the empty bed residence time of the packing layer is 0.5-1.5h. Open the inlet and outlet of the reflux device to allow the packing material in the packing layer of the sulfur autotrophic denitrification expanded bed to expand. Then, input the wastewater containing pollutants to be treated into the sulfur autotrophic denitrification expanded bed through the influent device. Take samples to test the concentration of nitrate nitrogen, ammonia nitrogen and total phosphorus in the effluent at the outlet.

6. The method for deep nitrogen removal from wastewater using a sulfur-autotrophic denitrification expanded bed according to claim 5, characterized in that, In step A1, the pH value of the wastewater containing pollutants is controlled to be 7.4-7.6.

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