A sewage denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler and its application method

Abstract

The present invention relates to the field of wastewater treatment technology, and specifically to a sewage denitrification and phosphorus removal treatment system based on sponge sulfide iron composite filler and an application method thereof. The sewage treatment units of this system are, in order, a primary sedimentation tank, a biological sulfate reduction unit with sponge hydroxyl iron oxide as filler, an aerobic membrane bioreactor, and an autotrophic denitrification unit with sponge sulfide hydroxyl iron oxide as filler. The filter in this system is constructed with a mixed bacterial community with sulfate-reducing bacteria and sulfur autotrophic denitrifying bacteria as the main body, which can be used for the synthesis and regeneration of sponge sulfide hydroxyl iron oxide, and can also be used for autotrophic denitrification; by changing the order of the filter, the filler regeneration cycle is realized, which not only reduces the cost of the process, but also enables the process to have the ability to operate continuously for a long time. The denitrification and phosphorus removal system constructed by the present invention realizes the efficient and coordinated removal of nitrogen, phosphorus, and organic matter in sewage without the need for additional addition of carbon sources, and effectively recycles sulfate in sewage.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a sewage denitrification and dephosphorization treatment system based on sponge ferrosulfur composite filler and an application method thereof. Background Art

[0002] With the continuous development of human industry, the nitrogen and phosphorus environment of natural water bodies has been severely damaged. Excessive nitrogen and phosphate discharge into natural water bodies will cause a series of serious damage to the ecosystem and human health. Excessive nitrogen and phosphorus enrichment in water will lead to eutrophication of water bodies, produce algal blooms, suffocate fish and aquatic organisms, and cause serious environmental problems. At present, sewage denitrification and phosphorus removal are mainly achieved through biological denitrification. This is because the advantages of biological treatment technology are mild reaction conditions, cheap and easy to obtain raw materials, significant effects, and low investment, so it has become the mainstream method of denitrification and phosphorus removal. However, at present, urban sewage in my country often presents the characteristics of low carbon nitrogen ratio (C / N) during deep treatment. In order to meet the strict nitrogen and phosphorus emission requirements, traditional sewage treatment processes need to add additional carbon sources or use chemical reagents to achieve enhanced denitrification and phosphorus removal. High energy consumption, high cost, large area, substandard nitrogen and phosphorus removal effects, and unstable effluent water quality have become problems that need to be urgently solved in urban sewage treatment.

[0003] Recently, more and more studies have shown that enhanced nitrogen and phosphorus removal processes based on natural sulfide iron compounds can effectively solve the above problems. This method is based on the traditional activated sludge method, introduces nitrogen and phosphorus removal to the tail end of secondary treatment, uses sulfide iron compounds as electron donors, and utilizes the sulfur autotrophic denitrification process to achieve biological nitrogen removal without the need for a carbon source. At the same time, chemical enhanced phosphorus removal is achieved through the interaction precipitation between iron and phosphorus. However, this method still has some urgent problems to be solved: (1) Due to the low activity of natural pyrite, the rate of autotrophic denitrification by microorganisms using it is extremely low, and often requires a hydraulic retention time of more than one day. If the denitrification efficiency of natural pyrite is to be improved, it is necessary to reduce the size of the filler, modify the surface, etc., which increases the cost of the overall process, so it is extremely unrealistic to apply it in sewage treatment projects; (2) Natural pyrite as a filler is gradually oxidized during denitrification, and its denitrification efficiency gradually decreases. It is necessary to continuously add new fillers to the reactor to replace the old fillers to maintain the denitrification effect, and this requires detailed determination of the filler composition at various locations in the reactor, which will also lead to an increase in the cost of process operation and increase the difficulty of actual process operation; (3) With the replacement of fillers, the denitrification microorganisms attached to the fillers will also be lost. After multiple operations, they need to be re-tamed to produce biofilm on the fillers, which will cause the process to be unable to operate continuously for a long time. Therefore, it is necessary to develop a cyclic denitrification and phosphorus removal process based on sulfide iron compounds. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a sewage denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler. The system couples biological sulfate reduction, sulfur autotrophic denitrification and chemical enhanced phosphorus removal to the existing secondary biological treatment process to achieve enhanced denitrification and phosphorus removal without the need for carbon sources and chemical reagents. The operation is simple and the denitrification rate is improved while maintaining low costs. In addition, by constructing a mixed functional bacterial community in the system, the filter can be used for filler and synthesis and regeneration, as well as for autotrophic denitrification. By recycling the filter and the sponge sulfide-iron composite filler, the cost of the process is reduced, and the process has the ability to operate continuously for a long time, and has good application prospects.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention provides a sewage denitrification and phosphorus removal treatment system based on a sponge-sulfur-iron composite filler, characterized in that the sewage denitrification and phosphorus removal treatment system comprises a primary sedimentation tank (5), a biological sulfate reduction unit, an aerobic membrane biological treatment unit (4), and a sulfur autotrophic denitrification treatment unit; the primary sedimentation tank (5) adopts an advection sedimentation tank for removing suspended particles and other insoluble and insoluble solid impurities in water; the biological sulfate reduction unit is a biological filter tank I (1); the aerobic membrane biological treatment unit (4) is provided with an air inlet at the bottom, the air inlet is connected to an exhaust pipe of an aeration pump (3); the sulfur autotrophic denitrification treatment unit is a biological filter tank II (2);

[0007] The biological filter tank I (1) is filled with sponge oxyhydroxy iron and mixed functional bacterial sludge, wherein the mixed functional bacterial sludge contains a mixed bacterial community mainly composed of sulfate-reducing bacteria and sulfur-autotrophic denitrifying bacteria;

[0008] The aerobic membrane biological treatment unit (4) is a built-in membrane bioreactor;

[0009] The biological filter II (2) is filled with sponge sulfidized hydroxyl iron oxide and mixed functional bacterial sludge, wherein the mixed functional bacterial sludge contains a mixed bacterial community mainly composed of sulfate-reducing bacteria and sulfur-autotrophic denitrifying bacteria;

[0010] The biofilter tank I (1) and the biofilter tank II (2) are respectively connected to the primary sedimentation tank (5) and the aerobic membrane biological treatment unit (4).

[0011] Preferably, the aerobic membrane biological treatment unit (4) is a built-in membrane bioreactor, wherein the membrane assembly adopts a plate-and-frame flat membrane, the membrane material is a polyvinylidene fluoride membrane material, and the supporting material is a stainless steel membrane.

[0012] Preferably, the particle size of the sponge hydroxyl iron oxide is 0.075-2.0 mm, and the filling rate of the sponge hydroxyl iron oxide and the mixed functional bacterial sludge in the biofilter tank I (1) is 80-90%; the particle size of the sponge sulfide hydroxyl iron oxide is 0.075-2.0 mm, and the filling rate of the sponge sulfide hydroxyl iron oxide and the mixed functional bacterial sludge in the biofilter tank II (2) is 80-90%.

[0013] Preferably, the sponge iron oxyhydroxide is sponge-state FeOOH powder.

[0014] Preferably, the method for preparing the sponge hydroxyl iron oxide is: co-culturing the sponge hydroxyl iron oxide and sulfate-reducing bacteria under sulfate-rich conditions and neutral pH, and controlling the temperature at 26° C. to synthesize the sponge sulfide hydroxyl iron oxide.

[0015] Preferably, the method for acclimating the mixed functional bacteria sludge is: periodically and alternately injecting nitrate-containing culture solution and sulfate-containing culture solution into the aerobic tank sludge to obtain a mixed functional bacterial community after acclimation.

[0016] The present invention also provides a method for treating wastewater using a sewage denitrification and phosphorus removal treatment system based on a sponge sulfide-iron composite filler, wherein the sewage denitrification and phosphorus removal treatment system based on a sponge sulfide-iron composite filler is used to perform deep denitrification and phosphorus removal treatment on the wastewater, and the specific steps are as follows:

[0017] S1. The order in which sewage flows through the treatment units is primary sedimentation tank (5) → biological filter I (1) → aerobic membrane biological treatment unit (4) → biological filter II (2). The specific process is as follows:

[0018] S1.1. Add wastewater with low nitrogen and phosphorus content to the treatment system, and first pass through the primary sedimentation tank (5) to remove suspended solid particles in the water. The water flowing out of the primary sedimentation tank (5) then enters the biological filter I (1). In this stage, the biological filter I (1) serves as a biological sulfate reduction unit. The wastewater undergoes sulfate reduction reaction under the action of sulfate-reducing bacteria, continuously synthesizing sponge sulfhydryl iron oxide filler, and consuming organic matter and phosphate in the sewage.

[0019] S1.2, the effluent treated by the biofilter I (1) enters the aerobic membrane biological treatment unit (4), and the ammonia nitrogen in the effluent of the biofilter I (1) is oxidized into nitrate nitrogen under aeration and low load conditions;

[0020] S1.3, the effluent of the aerobic membrane biological treatment unit (4) enters the biofilter II (2). In this stage, the biofilter II (2) serves as a sulfur autotrophic denitrification treatment unit. Under the action of sulfur autotrophic denitrifying bacteria, the reduced sulfur in the filler is consumed and oxidized into sulfate, while the nitrate is reduced to N 2 , to remove nitrates and consume residual phosphates;

[0021] S2. When a large amount of sponge hydroxyl iron carriers in biofilter I (1) are converted into sponge sulfide hydroxyl iron carriers, and a large amount of sponge sulfide hydroxyl iron carriers in biofilter II (2) are consumed as sponge hydroxyl iron carriers, the order of sewage flowing through the treatment units is changed to primary sedimentation tank (5) → biofilter II (2) → aerobic membrane biological treatment unit (4) → biofilter I (1). In the next stage, biofilter II (2) is used as a biological sulfate reduction unit, and biofilter I (1) is used as a sulfur autotrophic denitrification treatment unit, and so on to treat the wastewater in a reciprocating cycle.

[0022] Preferably, the step S2 uses valve control to change the order in which the sewage flows through the treatment units.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The system of the present invention comprises a primary sedimentation tank, a biological sulfate reduction unit, an aerobic membrane biological treatment unit and a sulfur autotrophic denitrification treatment unit. Sulfur autotrophic denitrification is used for denitrification. In the context of low C / N ratio in urban sewage today, compared with the traditional biological denitrification method, no additional organic carbon source is required as an electron donor. The filler in the biological filter of the present invention itself has a phosphorus removal function, and no additional chemical reagent is required for phosphorus removal. In addition, the application of autotrophic denitrification and membrane biological treatment reduces the sludge production, avoids the cost increase caused by the treatment and disposal of a large amount of excess sludge, and the overall process operation cost and energy consumption are low.

[0025] (2) The sponge pyrite composite filler in the present invention is prepared by a biochemical synthesis method based on sulfur reduction, and has high porosity, high specific surface area and amorphous structure, which improves the biochemical reaction rate of sulfur autotrophic denitrification, solves the problem of low activity of natural pyrite and long hydraulic retention time, and improves the treatment efficiency of sewage. The biochemical synthesis method does not require the use of chemical reagents such as strong acids and strong bases and high temperature and high pressure operating environment, and is simple and safe to operate, environmentally friendly and reliable, and low cost.

[0026] (3) The sponge sulfide-iron composite filler used in the present invention is renewable. After the reduced sulfur in the filler is oxidized and consumed, the sulfide-iron can be loaded onto the filler surface again by sulfate-reducing bacteria, and the filler can be recycled, thereby reducing the cost of adding chemical agents. In addition, since the specially domesticated mixed functional bacterial community used in the present invention contains both sulfate-reducing bacteria and sulfur autotrophic denitrifying bacteria, the biofilter I and biofilter II have the functions of both biological sulfate reduction unit and sulfur autotrophic denitrification unit. At the same time, a membrane bioreactor is used instead of a traditional secondary sedimentation tank for mud-water separation, which improves the utilization efficiency of the reactor and saves the land cost of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of a sewage denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler;

[0028] Figure 2 Among them, 1-biofilter I, 2-biofilter II, 3-aeration pump, 4-aerobic membrane biological treatment unit, 5-primary sedimentation tank, 11-valve, 12-valve, 13-valve, 14-valve, 21-valve, 22-valve, 23-valve, 24-valve;

[0029] Figure 3 The SO in the six cycles after the functional bacterial flora was domesticated and stabilized 4 2- and NO 3 - Inlet and outlet water concentration;

[0030] Figure 4 This is a diagram showing the effect of continuous autotrophic denitrification based on renewable iron-sulfur composite filler;

[0031] Figure 5 This is a graph showing the enhanced phosphorus removal effect within 15 hours based on renewable ferrous sulfur composite filler. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0034] Example 1 A sewage denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler

[0035] 1. Domestication of mixed functional flora

[0036] The nitrate-containing wastewater and sulfate-containing wastewater were periodically injected into the reactor inoculated with the aerobic pool sludge of the multi-stage AO process of Shenzhen Futian Water Purification Plant. The reactor was stirred and cultured at room temperature and neutral pH. The hydraulic retention time of the two stages was set to 48 h. The domesticated mixed functional bacterial community was obtained, in which the nitrate wastewater contained 0.455 g / L PO 4 3- -P, 0.277 g / L NO 3 --N, 1.29 g / LS 2 O 3 2- -S; sulfate wastewater contains 0.666 g / L SO 4 2- -S, 0.089 g / LHPO 4 2- -P, 0.262 g / L NH 4 + -N. SO within 6 cycles after the mixed functional bacterial flora was domesticated and stabilized 4 2- and NO 3 - Inlet and outlet water concentrations Figure 2 As shown in the figure, the hydraulic retention time of each cycle is 4 days, during which the mixed bacterial community can not only completely degrade NO-3-N but also remove the generated SO 4 2- Completely restore and remove.

[0037] 2. Wastewater denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler

[0038] like Figure 1 The sewage denitrification and phosphorus removal treatment system based on sponge sulfur-iron composite filler shown in the figure comprises a primary sedimentation tank 5, a biological sulfate reduction unit, an aerobic membrane biological treatment unit 4, and a sulfur autotrophic denitrification treatment unit; the primary sedimentation tank 5 adopts a horizontal flow sedimentation tank for removing suspended particles and other insoluble and insoluble solid impurities in the water, the biological sulfate reduction unit is a biological filter tank Ⅰ 1, the aerobic membrane biological treatment unit 4 is provided with an air inlet at the bottom, and the air inlet is connected to the exhaust pipe of the aeration pump 3, and the sulfur autotrophic denitrification treatment unit is a biological filter tank Ⅱ 2.

[0039] The primary sedimentation tank 5 is provided with a first and a second water outlet at the lower end thereof, which are respectively connected to the lower water inlets of the biofilter tank Ⅰ 1 and the biofilter tank Ⅱ 2, and are respectively connected to the valve 11 and the valve 21 on the pipeline; the biofilter tank Ⅰ 1 is provided with a first and a second water outlet at the upper end thereof, which are respectively connected to the water inlet of the aerobic membrane biological treatment unit 4 and the first water outlet at the end of the pipeline, and are respectively connected to the valve 12 and the valve 24 on the pipeline; the aerobic membrane biological treatment unit 4 is provided with a first and a second water outlet, which are respectively connected to the lower water inlet of the biofilter tank Ⅰ 1 and the lower water inlet of the biofilter tank Ⅱ 2, and are respectively connected to the valve 13 and the valve 23 on the pipeline; the biofilter tank Ⅱ 2 is provided with a first and a second water outlet at the upper end thereof, which are respectively connected to the water inlet of the aerobic membrane biological treatment unit and the second water outlet at the end of the pipeline, and are respectively connected to the valve 22 and the valve 14 on the pipeline.

[0040] The biological filter tank Ⅰ 1 is filled with sponge ferric hydroxide and the mixed functional bacteria sludge; the sponge ferric hydroxide is sponge FeOOH powder with a particle size of 0.075-2.0 mm, the mass volume ratio of sponge ferric hydroxide to sludge is 6-7 g / L, and the filling rate is 85% of the total volume of the biological filter tank Ⅰ 1;

[0041] The aerobic membrane biological treatment unit 4 is based on the traditional sewage secondary treatment process, and uses activated sludge to convert the residual organic matter in the sewage into biomass or carbon dioxide, and convert ammonia nitrogen into nitrate nitrogen under the conditions of an aerated environment and low organic matter load; the process uses a built-in membrane bioreactor with less energy consumption and smaller footprint, and the membrane component uses a plate-and-frame flat membrane with a small transmembrane pressure difference. The membrane material is PVDF polyvinylidene fluoride membrane material with good oxidation resistance and strong corrosion resistance, and the supporting material is a stainless steel membrane; the setting of the membrane component can strengthen the solid-liquid separation in the treatment unit, and prevent the solid suspended matter in the treatment unit from entering the subsequent treatment unit, thereby causing interference; in addition, the use of the membrane bioreactor can also reduce the sludge production.

[0042] The biological filter tank II 2 is filled with sponge sulfide hydroxyl iron oxide and the above-mentioned mixed functional bacteria sludge; the preparation method of the sponge sulfide hydroxyl iron oxide is to co-cultivate the sponge sulfide hydroxyl iron oxide and sulfate-reducing bacteria under sulfate-rich conditions and neutral pH, and control the temperature at 26°C to synthesize sulfide hydroxyl iron oxide; the particle size of the sponge sulfide hydroxyl iron oxide is 0.075-2.0 mm, the mass volume ratio of the sponge sulfide hydroxyl iron oxide to the sludge is 6-7g / L, and the filling rate is 85% of the total volume of the biological filter tank II 2.

[0043] 3. The application method of the sewage denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler is:

[0044] S1. The order of sewage flowing through the treatment units is primary sedimentation tank 5 → biological filter Ⅰ 1 → aerobic membrane biological treatment unit 4 → biological filter Ⅱ 2. The specific process is as follows:

[0045] S1.1. Open valves 11, 12, 13 and 14, close valves 21, 22, 23 and 24, add low nitrogen and phosphorus content wastewater into the treatment system, first pass through the primary sedimentation tank 5 to settle and remove the suspended solid particles in the water, and then the water flowing out of the primary sedimentation tank 5 enters the biological filter Ⅰ 1. In this stage, the biological filter Ⅰ 1 serves as a biological sulfate reduction unit. The filter uses sponge hydroxyl iron as a carrier, and the functional bacteria in the filter are sulfate-reducing bacteria in the mixed bacterial community. The sulfate and organic matter in the water are used as electron acceptors and electron donors to initially remove the organic matter and reduce the sulfate to S 2-, a sulfide-iron composite layer is formed on the surface of the sponge oxyhydroxide iron, gradually forming a sponge sulfide oxyhydroxide iron; in addition, iron ions are released and interact with phosphate in the sewage to form an iron-phosphorus composite precipitate that is deposited on the carrier, thereby consuming phosphate;

[0046] S1.2, the effluent after treatment in biofilter Ⅰ 1 enters aerobic membrane biological treatment unit 4, and the ammonia nitrogen in the effluent of biofilter Ⅰ 1 is oxidized into nitrate nitrogen under aeration and low load conditions, and the air-water ratio in aeration is 2:1;

[0047] S1.3, the effluent after the treatment of aerobic membrane biological treatment unit 4 enters biofilter II 2. In this stage, biofilter II 2 is used as a sulfur autotrophic denitrification treatment unit. The filter uses sponge sulfhydryl iron oxide, and the functional bacteria in the filter are sulfur autotrophic denitrifying bacteria in the mixed bacterial community. The nitrate in the water and sponge sulfhydryl iron oxide are used as electron acceptors and electron donors to consume and oxidize the reduced sulfur in the filler into sulfate, and at the same time reduce the nitrate to N 2 , to remove nitrates; in addition, the residual phosphates in the water will interact with the released iron ions to form iron-phosphorus composite precipitates that are deposited on the carrier to achieve the effect of enhanced phosphorus removal; the sewage treated in the biological filter II 2 is discharged from the second outlet at the end of the pipeline, completing the deep denitrification and phosphorus removal treatment of the wastewater;

[0048] S2. When a large amount of sponge hydroxyl iron carriers in biofilter Ⅰ 1 are converted into sponge sulfide hydroxyl iron carriers, and a large amount of sponge sulfide hydroxyl iron carriers in biofilter Ⅱ 2 are consumed as sponge hydroxyl iron carriers, the order of sewage flowing through the treatment units is changed to primary sedimentation tank 5 → biofilter Ⅱ 2 → aerobic membrane biological treatment unit 4 → biofilter Ⅰ 1, valves 21, 22, 23 and 24 are opened, and valves 11, 12, 13 and 14 are closed. In this stage, biofilter Ⅱ 2 serves as a biological sulfate reduction unit, and biofilter Ⅰ 1 serves as a sulfur autotrophic denitrification treatment unit. Finally, the effluent is discharged from the first outlet at the end of the pipeline, and the wastewater is treated in this cycle.

[0049] Experimental Example 1 Simulated nitrate wastewater treatment experiment

[0050] The simulated nitrate wastewater to be treated in this experiment contains 30 mg / L NO 3 - -N, 1 mg / L NH 4 + -N, 4 mg / L PO 4 3- -P; the added mixed functional bacteria sludge MLVSS is about 3g / L;

[0051] The above-mentioned sewage denitrification and phosphorus removal treatment system based on sponge sulfur-iron composite filler was used to carry out autotrophic denitrification of simulated nitrate wastewater for 40 consecutive days. Figure 3 As shown in the figure, the total nitrogen concentration in the effluent is below 5 mg. This method can meet the requirements of efficient denitrification. Moreover, as the reaction cycle proceeds, the denitrification sustainability of the sulfidohydroxy iron oxide filler gradually increases. This also shows that the filler has good regeneration ability under long-term operation of the system, and the filler can be recycled, reducing the cost of chemical agent addition.

[0052] Experimental Example 2 Simulated nitrate and phosphate wastewater treatment experiment

[0053] The simulated nitrate and phosphate wastewater components to be treated in this experiment are 68.5 mg / L NO 3 - -N, 32.7mg / L NH 4 + -N, 160 mg / L PO 4 3- -P; the MLVSS of the added mixed functional bacteria sludge were 0.4, 0.8, 1.2, 1.6 and 2 g / L respectively;

[0054] The above-mentioned sewage denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler was used to carry out enhanced phosphorus removal for 15 hours on the simulated nitrate and phosphate wastewater. The effects of enhanced denitrification and phosphorus removal by filler were as follows: Figure 4 , Figure 5 As shown in the experimental results, after the system treatment, the effluent PO 4 3- -P concentration dropped to below 40 mg / L, and at a suitable sludge concentration, NO 3 - -N can also be fully removed within 15 hours. Filler phosphorus removal is mainly based on chemical precipitation. Under the background of low phosphorus content in municipal sewage, this method can meet the requirements of continuous enhanced phosphorus removal over a long period of time.

[0055] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A sewage denitrification and phosphorus removal treatment system based on sponge sulfide-iron composite filler, It is characterized in that The sewage denitrification and phosphorus removal treatment system comprises a primary sedimentation tank (5), a biological sulfate reduction unit, an aerobic membrane biological treatment unit (4), and a sulfur autotrophic denitrification treatment unit; the primary sedimentation tank (5) adopts a horizontal flow sedimentation tank for removing suspended particles and other insoluble and insoluble solid impurities in water; the biological sulfate reduction unit is a biological filter tank I (1); the aerobic membrane biological treatment unit (4) is provided with an air inlet at the bottom, the air inlet is connected to the exhaust pipe of the aeration pump (3); the sulfur autotrophic denitrification treatment unit is a biological filter tank II (2); The biological filter tank I (1) is filled with sponge oxyhydroxy iron and mixed functional bacterial sludge, wherein the mixed functional bacterial sludge contains a mixed bacterial community mainly composed of sulfate-reducing bacteria and sulfur-autotrophic denitrifying bacteria; The aerobic membrane biological treatment unit (4) is a built-in membrane bioreactor; The biological filter II (2) is filled with sponge sulfidized hydroxyl iron oxide and mixed functional bacterial sludge, wherein the mixed functional bacterial sludge contains a mixed bacterial community mainly composed of sulfate-reducing bacteria and sulfur-autotrophic denitrifying bacteria; The biofilter tank I (1) and the biofilter tank II (2) are respectively connected to the primary sedimentation tank (5) and the aerobic membrane biological treatment unit (4), and the biofilter tank I (1) and the biofilter tank II (2) are respectively connected to the first water outlet at the end of the pipeline and the second water outlet at the end of the pipeline; The sponge ferric oxyhydroxide is sponge-state FeOOH powder; The preparation method of the sponge sulfidized hydroxyl iron oxide is as follows: co-culturing the sponge sulfidized hydroxyl iron oxide and sulfate-reducing bacteria under sulfate-rich conditions and neutral pH, and controlling the temperature at 26° C. to synthesize the sponge sulfidized hydroxyl iron oxide; The method for taming the mixed functional bacteria sludge is as follows: periodically and alternately injecting a nitrate-containing culture solution and a sulfate-containing culture solution into the aerobic pool sludge to obtain a mixed functional bacterial community after taming.

2. A sewage denitrification and dephosphorization treatment system based on sponge sulfide-iron composite filler according to claim 1, It is characterized in that The aerobic membrane biological treatment unit (4) is a built-in membrane bioreactor, wherein the membrane assembly adopts a plate-and-frame flat membrane, the membrane material is a polyvinylidene fluoride membrane material, and the supporting material is a stainless steel membrane.

3. A sewage denitrification and dephosphorization treatment system based on sponge sulfide-iron composite filler according to claim 1, It is characterized in that The particle size of the sponge hydroxyl iron oxide is 0.075-2.0 mm, and the filling rate of the sponge hydroxyl iron oxide and the mixed functional bacteria sludge in the biofilter tank I (1) is 80-90%; the particle size of the sponge sulfide hydroxyl iron oxide is 0.075-2.0 mm, and the filling rate of the sponge sulfide hydroxyl iron oxide and the mixed functional bacteria sludge in the biofilter tank II (2) is 80-90%.

4. A method for treating wastewater using a sewage denitrification and dephosphorization treatment system based on a sponge sulfide-iron composite filler, It is characterized in that The wastewater is subjected to deep denitrification and dephosphorization treatment by using a sewage denitrification and dephosphorization treatment system based on a sponge sulfide-iron composite filler as described in any one of claims 1 to 3, and the specific steps are as follows: S1. The order in which sewage flows through the treatment units is primary sedimentation tank (5) → biological filter I (1) → aerobic membrane biological treatment unit (4) → biological filter II (2). The specific process is as follows: S1.

1. Add wastewater with low nitrogen and phosphorus content to the treatment system, and first pass through the primary sedimentation tank (5) to remove suspended solid particles in the water. The water flowing out of the primary sedimentation tank (5) then enters the biological filter I (1). In this stage, the biological filter I (1) serves as a biological sulfate reduction unit. The wastewater undergoes sulfate reduction reaction under the action of sulfate-reducing bacteria, continuously synthesizing sponge sulfhydryl iron oxide filler, and consuming organic matter and phosphate in the sewage. S1.2, the effluent treated by the biofilter I (1) enters the aerobic membrane biological treatment unit (4), and the ammonia nitrogen in the effluent of the biofilter I (1) is oxidized into nitrate nitrogen under aeration and low load conditions; S1.3, the effluent of the aerobic membrane biological treatment unit (4) enters the biofilter II (2). In this stage, the biofilter II (2) serves as a sulfur autotrophic denitrification treatment unit. Under the action of sulfur autotrophic denitrifying bacteria, the reduced sulfur in the filler is consumed and oxidized into sulfate, while the nitrate is reduced to N 2 , to remove nitrates and consume residual phosphates; S2. When a large amount of sponge hydroxyl iron carriers in biofilter I (1) are converted into sponge sulfide hydroxyl iron carriers, and a large amount of sponge sulfide hydroxyl iron carriers in biofilter II (2) are consumed as sponge hydroxyl iron carriers, the order of sewage flowing through the treatment units is changed to primary sedimentation tank (5) → biofilter II (2) → aerobic membrane biological treatment unit (4) → biofilter I (1). In the next stage, biofilter II (2) is used as a biological sulfate reduction unit, and biofilter I (1) is used as a sulfur autotrophic denitrification treatment unit, and so on to treat the wastewater in a reciprocating cycle.

5. A method for treating wastewater by a sewage denitrification and dephosphorization treatment system based on sponge sulfide-iron composite filler according to claim 4, It is characterized in that The step S2 uses valve control to change the order in which the sewage flows through the treatment units.

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