Artificial wetland treatment of nitrate nitrogen sewage system and method

Abstract

The present invention discloses a system and method for treating nitrate nitrogen sewage in an artificial wetland. The system comprises a wetland pool, a wetland matrix, a water distribution device, a water outlet device and plants. The wetland matrix is ​​filled in the wetland pool, the wetland matrix comprises pyrite, volcanic rock and biochar, the water distribution device is located at the top of the wetland pool for distributing water into the wetland pool, the water outlet device is located at the bottom of the wetland pool to collect treated sewage, the plants are planted in the wetland matrix, and the dissolved oxygen concentration of the autotrophic denitrification type surface subsurface flow artificial wetland treating nitrate nitrogen sewage system is maintained at 1.2 to 2.8 mg / L. The above system can efficiently degrade pollutants, is simple to operate, is easy to implement, does not require power and an external carbon source, has no strict requirements on operating conditions, and can achieve sulfur autotrophic denitrification reaction under set conditions.

Description

Technical Field

[0001] The invention relates to the technical field of water environment treatment, and in particular to a system and method for treating nitrate nitrogen sewage using an autotrophic denitrification type surface subsurface flow artificial wetland. Background Art

[0002] As a new type of sewage treatment process, artificial wetlands mainly degrade pollutants through biodegradation, physical adsorption, and chemical conversion. Generally speaking, artificial wetlands are divided into three categories: vertical flow artificial wetlands, horizontal surface subsurface flow artificial wetlands, and horizontal subsurface flow artificial wetlands. The above three methods can purify water from different sources in a coordinated or separate manner. For sewage rich in nitrate nitrogen, the above three methods cannot achieve good treatment effects. On the one hand, because traditional artificial wetlands mainly rely on anaerobic heterotrophic denitrification processes to completely reduce nitrogen oxides, especially nitrate nitrogen, in sewage to nitrogen gas, this process requires the addition of organic carbon sources as electron donors to strengthen anaerobic heterotrophic denitrification reactions to solve the problem of insufficient carbon sources for heterotrophic anaerobic denitrification reactions in traditional artificial wetlands; on the other hand, the nitrate nitrogen content in sewage is much higher than that of ammonia nitrogen and nitrite nitrogen, which increases the dependence on heterotrophic anaerobic denitrification processes; at the same time, other heterotrophic bacteria compete with heterotrophic denitrifying bacteria for organic matter as a carbon source, making it more difficult for nitrate nitrogen to be completely reduced to nitrogen gas through heterotrophic denitrification processes. Based on the above, the purification effect of artificial wetlands on sewage rich in nitrate nitrogen depends on the supply of organic carbon sources. In addition, plant residues or physically trapped particulate matter will accumulate on the surface and inside the pores of artificial wetland fillers. If they are not treated during long-term operation, they will lead to a local anaerobic microenvironment, reduce the infiltration capacity of artificial wetlands, and with the accumulation of extracellular polymers, large particulate matter will condense and adsorb, accelerating the blockage of matrix pores. Summary of the invention

[0003] Based on this, plant residues will accumulate on the surface and inside the pores of artificial wetland fillers in traditional sewage treatment processes, and long-term operation will lead to a local anaerobic microenvironment, reducing the infiltration capacity of artificial wetlands. More importantly, for the treatment of sewage or tail water containing nitrate nitrogen, the lack of an organic carbon source will hinder the complete reduction of nitrate nitrogen to nitrogen gas. However, the addition of an organic carbon source will accelerate the secretion of extracellular polymers, allowing them to adsorb and intercept large particles, further accelerating the clogging of matrix pores. In response to this problem, this patent provides an autotrophic denitrification type surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage. The autotrophic denitrification type surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage of the present invention does not rely on anaerobic heterotrophic denitrification reactions to remove nitrate nitrogen, ensuring the nitrate nitrogen purification effect while operating efficiently for a long time.

[0004] An embodiment of the present application provides an autotrophic denitrification type surface subsurface flow artificial wetland system for treating nitrate-nitrogen wastewater.

[0005] A system and method for treating nitrate-nitrogen sewage using an autotrophic denitrification type surface subsurface flow artificial wetland, the system comprising a wetland pool, a wetland matrix, a water distribution device, a water outlet device and wetland plants; the wetland matrix is ​​filled in the wetland pool, the wetland matrix comprises pyrite, volcanic rock and biochar; the water distribution device is located on the matrix surface of the wetland pool, the incoming water enters the pool through the water distribution device and is discharged in a gravity flow manner; the water outlet device is located in the wetland pool. the bottom of the pool; the wetland plants are planted in the wetland matrix; the dissolved oxygen concentration of the autotrophic denitrification surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage is maintained at 1.2-2.8 mg / L to construct a dissolved oxygen environment that is beneficial to the growth and metabolism of autotrophic denitrifying bacteria but not conducive to the growth of heterotrophic anaerobic denitrifying bacteria; when the autotrophic denitrification surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage is in operation, the hydraulic retention time is controlled to ensure that the nitrate nitrogen in the influent is fully in contact with the autotrophic denitrifying bacteria and reduced to nitrogen gas.

[0006] In some embodiments, the autotrophic denitrification surface subsurface flow artificial wetland system for treating nitrate-nitrogen sewage also includes a filtration device, which includes a gravel filter layer and a Y-type filter. The gravel filter layer is laid on the surface of the wetland matrix, and the thickness of the gravel filter layer is 2 to 5 cm. The Y-type filter is installed on the water outlet device.

[0007] In some of the embodiments, the volume ratio of the pyrite, the volcanic rock and the biochar is (1-5):(1-5):(1-5).

[0008] In some of the embodiments, the volume ratio of the pyrite, the volcanic rock and the biochar is 1:1:1.

[0009] In some embodiments, the water distribution device includes a plurality of water distribution pipes, the plurality of water distribution pipes are distributed at intervals, and the water distribution pipes have a plurality of water distribution holes.

[0010] In some of the embodiments, at least one of the following technical features is also included:

[0011] The interval between adjacent water distribution pipes is 0.1 to 0.3 m;

[0012] The length of the water distribution pipe is 0.5 to 1 m;

[0013] The distance between adjacent water distribution holes is 5 to 8 cm, and the diameter of the water distribution holes is 1 to 2 cm.

[0014] In some of the embodiments, at least one of the following technical features is also included:

[0015] The height of the wetland substrate is 25 to 35 cm;

[0016] The height of the wetland pool is 35 to 45 cm;

[0017] The particle size of the wetland matrix is ​​1 to 3 cm.

[0018] In some of the embodiments, at least one of the following technical features is also included:

[0019] The planting density of the plants is 16 to 20 plants / m 2 ;

[0020] The plants are selected from one or more of canna, reed, iris and windmill grass.

[0021] In some embodiments, the method for preparing the wetland substrate comprises the following steps:

[0022] preparing biochar;

[0023] The pyrite raw material is treated by soaking in 1 mol hydrochloric acid for 1 to 2 hours, and then placed in a cool place for air drying, and the matrix particle size is screened to obtain pyrite;

[0024] The volcanic rock raw material is soaked in 1 mol hydrochloric acid for 1 to 2 hours, placed in a cool place for air drying, and the matrix particle size is screened to obtain the volcanic rock.

[0025] In some embodiments, the preparation of biochar includes the following steps: roasting one or more of bamboo, reed, and iris in a muffle furnace at 300° C. to 400° C., and crushing after cooling to form the biochar;

[0026] And / or, the matrix particle sizes of the pyrite, the volcanic rock, and the biochar are each independently controlled within the range of 1 to 3 cm to increase the specific surface area.

[0027] Another embodiment of the present application provides a method for treating nitrate-nitrogen wastewater using an autotrophic denitrification subsurface artificial wetland.

[0028] A system and method for treating nitrate nitrogen wastewater using the autotrophic denitrification subsurface flow constructed wetland comprises the following steps:

[0029] Providing a dissolved oxygen environment for the autotrophic denitrification subsurface flow artificial wetland to treat nitrate nitrogen sewage system through plants;

[0030] The sewage is added into the wetland pool through the water distribution device, and the nitrate nitrogen in the sewage is reduced to nitrogen gas by Thiobacillus;

[0031] Ammonia nitrogen in sewage is oxidized to generate nitrite nitrogen and nitrate nitrogen. Pyrite and volcanic rock provide divalent iron ions to react with nitrite nitrogen to generate nitrogen gas. Pyrite and volcanic rock provide sulfide to promote the growth of sulfur-reducing bacteria Desulfovibrio, Desulfobulbus and Thiobacillus. Among them, sulfur-reducing bacteria Desulfovibrio and Desulfobulbus can reduce nitrate nitrogen through sulfide and / or organic matter as electron donors, and the reduction product ammonia nitrogen can be re-oxidized to nitrite nitrogen and nitrate nitrogen, while Thiobacillus can use sulfur as an electron donor to completely reduce nitrate nitrogen to nitrogen gas, or reduce part of nitrate nitrogen to ammonia nitrogen.

[0032] Biochar can enhance interspecies electron transfer, promote the growth and metabolism of sulfur-reducing bacteria Desulfovibrio and Desulfobulbus, and promote Thiobacillus to reduce nitrate nitrogen to nitrogen gas. Biochar can also improve the growth and metabolism of Geobacter, increase the intensity of the reaction of heterologous nitrate nitrogen reduction to ammonia nitrogen, and competitively inhibit the anaerobic heterotrophic denitrification process.

[0033] In some of the embodiments, the total nitrogen concentration of the sewage is no more than 30 mg / L, the hydraulic retention time is 2 to 6 hours, and the temperature is controlled to be greater than 10°C.

[0034] In some of the embodiments, the dissolved oxygen concentration of the autotrophic denitrification subsurface flow constructed wetland system for treating nitrate-nitrogen wastewater is controlled to be maintained at 1.2-2.8 mg / L.

[0035] The above-mentioned autotrophic denitrification surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage can improve the metabolism of autotrophic denitrifying bacteria while obtaining autotrophic denitrifying bacteria by controlling the structure of the artificial wetland pool and the composition of the matrix, strengthen the chemical reaction between divalent iron ions and nitrite nitrogen, and inhibit the metabolism of potential heterotrophic denitrifying bacteria, so that nitrogen oxides entering the autotrophic denitrification surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage can be reduced to nitrogen gas by autotrophic denitrifying bacteria and pure chemical reaction and enter the environment. The present invention can efficiently degrade pollutants, is simple to operate, easy to implement, does not require power and external carbon source, has no strict requirements on operating conditions, and can realize sulfur autotrophic denitrification reaction under set conditions; the redox reaction of divalent iron and nitrite nitrogen, and the competitive inhibition of Geobacter on anaerobic heterotrophic denitrifying bacteria, realize the biological denitrification process dominated by autotrophic denitrification in the surface subsurface flow artificial wetland, and can be used to remove nitrate nitrogen in the tail water of sewage treatment plants without the need to supplement organic carbon and additional power. In addition, the present invention can be used in wetland parks to purify rainwater and landscape water, bringing more ecological benefits and providing a place for rest for the public.

[0036] The above-mentioned autotrophic denitrification surface subsurface flow artificial wetland treatment nitrate nitrogen sewage system, based on the existing surface subsurface flow artificial wetland, controls the substrate height, pool height, substrate composition and ratio of the surface subsurface flow artificial wetland to promote the growth and metabolism of sulfur autotrophic denitrifying bacteria, and utilizes the competitive advantage of Geobacter to heterotrophic anaerobic denitrifying bacteria to inhibit the growth of anaerobic heterotrophic denitrifying bacteria, so that nitrate nitrogen is not reduced through the heterotrophic denitrification process, thereby promoting the growth of autotrophic denitrifying bacteria; at the same time, the ammonia nitrogen generated by the reduction of nitrate nitrogen by Geobacter can be re-oxidized to nitrate nitrogen due to the high dissolved oxygen concentration (1.2-2.8 mg / L) of this artificial wetland system, and further reduced to nitrogen gas by autotrophic denitrifying bacteria. In addition, the rich divalent iron in the substrate gradation can strengthen the reduction reaction of divalent iron and nitrite nitrogen, and further directly reduce nitrite nitrogen to nitrogen gas through chemical reaction. Through the above measures: sulfur autotrophic denitrifying bacteria and Geobacter are obtained by in situ culture. The former carries out autotrophic denitrification, while the latter inhibits the growth and metabolism of heterotrophic denitrifying bacteria and indirectly provides nitrate nitrogen for the former; chemical reduction reaction of divalent iron and nitrite nitrogen can also be carried out to further reduce nitrogen oxides to nitrogen gas; in addition, by maintaining a high dissolved oxygen concentration, organic matter accumulation is reduced, wetland porosity is increased, and the service life of the wetland is extended.

[0037] In the present invention, for sewage types with a nitrate nitrogen concentration of no more than 30 mg / L, such as sewage plant tail water mainly composed of nitrate nitrogen, the present invention can adapt to the flow change and efficiently reduce the nitrate nitrogen to nitrogen gas, so as to achieve the following beneficial effects: (1) competitive inhibition of heterotrophic denitrifying bacteria by Geobacter; (2) nitrate nitrogen reduction mainly by sulfur autotrophic denitrifying bacteria, so that the system maintains a high nitrate nitrogen removal effect; (3) chemical reduction reaction of divalent iron and nitrite nitrogen, with divalent iron as an electron donor, without the participation of microorganisms; (4) in situ enrichment culture to obtain microbial genera such as Geobacter and sulfur autotrophic denitrifying bacteria. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0039] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings. In the following description, the same reference numerals represent the same parts.

[0040] Figure 1This is a schematic diagram of a system for treating nitrate-nitrogen wastewater using an autotrophic denitrifying subsurface flow constructed wetland according to an embodiment of the present invention.

[0041] Description of Reference Numerals

[0042] 10. Autotrophic denitrification subsurface flow artificial wetland system for treating nitrate-nitrogen wastewater; 100. Wetland pool; 200. Wetland matrix; 300. Water distribution device; 400. Water outlet device; 500. Plants; 610. Gravel filter layer; 620. Y-type filter. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0045] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0046] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0049] The embodiment of the present application provides an autotrophic denitrification type surface subsurface flow artificial wetland treatment nitrate nitrogen sewage system 10 to solve the problem that in the traditional sewage treatment process, plant 500 residues or physically trapped particulate matter will accumulate on the surface and inside the pores of the artificial wetland filler, and long-term operation will lead to a local anaerobic microenvironment, reduce the infiltration capacity of the artificial wetland, and with the accumulation of extracellular polymers, condense and adsorb large particulate matter, accelerating the blockage of the matrix pores. The following will be explained in conjunction with the accompanying drawings.

[0050] The autotrophic denitrification surface subsurface flow constructed wetland system 10 for treating nitrate nitrogen wastewater provided in the present application is exemplary, see Figure 1 As shown, Figure 1 The schematic diagram of the structure of the autotrophic denitrification subsurface artificial wetland system 10 for treating nitrate-nitrogen wastewater provided in the embodiment of the present application is as follows: The autotrophic denitrification subsurface artificial wetland system 10 for treating nitrate-nitrogen wastewater of the present application can be used for treating wastewater rich in nitrate-nitrogen.

[0051] In order to more clearly illustrate the structure of the autotrophic denitrification type surface subsurface flow constructed wetland system for treating nitrate-nitrogen wastewater 10, the autotrophic denitrification type surface subsurface flow constructed wetland system for treating nitrate-nitrogen wastewater 10 will be introduced below in conjunction with the accompanying drawings.

[0052] For example, see Figure 1 As shown, Figure 1 The schematic diagram of the structure of the autotrophic denitrification type surface subsurface flow constructed wetland system 10 for treating nitrate nitrogen wastewater provided in the embodiment of the present application. The autotrophic denitrification type surface subsurface flow constructed wetland system 10 for treating nitrate nitrogen wastewater comprises a wetland pool 100, a wetland matrix 200, a water distribution device 300, a water outlet device 400 and plants 500.

[0053] The wetland matrix 200 is filled in the wetland pool 100. The wetland matrix 200 includes pyrite, volcanic rock and biochar. The water distribution device 300 is laid on the surface of the wetland matrix 200 to distribute water into the wetland pool 100. The water entering the wetland pool 100 through the water distribution device 300 enters the wetland pool 100 and flows by gravity. The water outlet device 400 is located at the bottom of the wetland pool 100, which is used to collect the treated sewage and discharge it centrally. Plants 500 are planted in the wetland matrix 200. The dissolved oxygen concentration of the autotrophic denitrification surface subsurface artificial wetland system 10 for treating nitrate nitrogen wastewater is maintained at 1.2-2.8 mg / L to construct a dissolved oxygen environment that is beneficial to the growth of autotrophic denitrifying bacteria and unfavorable to the growth of heterotrophic anaerobic denitrifying bacteria. When the autotrophic denitrification surface subsurface artificial wetland system for treating nitrate nitrogen wastewater is in operation, the hydraulic retention time is controlled to ensure that the nitrate nitrogen in the influent is fully in contact with the autotrophic denitrifying bacteria and reduced to nitrogen gas.

[0054] In the present invention, ammonia nitrogen in sewage is oxidized to generate nitrite nitrogen and nitrate nitrogen, pyrite and volcanic rock provide divalent iron ions to react with nitrite nitrogen to generate nitrogen gas, and pyrite and volcanic rock provide sulfide to promote the growth of sulfur-reducing bacteria Desulfovibrio, Desulfobulbus and Thiobacillus. Among them, sulfur-reducing bacteria Desulfovibrio and Desulfobulbus can reduce nitrate nitrogen by using sulfide and / or organic matter as electron donors, and the reduced ammonia nitrogen can be reoxidized to nitrite nitrogen and nitrate nitrogen, while Thiobacillus can use sulfur as an electron donor to completely reduce nitrate nitrogen to nitrogen gas, or reduce part of nitrate nitrogen to ammonia nitrogen; biochar can enhance interspecies electron transfer, promote the growth and metabolism of sulfur-reducing bacteria Desulfovibrio and Desulfobulbus, and promote Thiobacillus to reduce nitrate nitrogen to nitrogen gas. Biochar can also improve the growth and metabolism of Geobacter, increase the intensity of the reaction of heterologous nitrate nitrogen reduction to ammonia nitrogen, and competitively inhibit the anaerobic heterotrophic denitrification process. Therefore, the biological reduction process of nitrogen oxides does not depend on anaerobic heterotrophic denitrifying bacteria, so there is no need to add additional organic carbon as an electron donor.

[0055] In some embodiments, the autotrophic denitrification surface subsurface flow artificial wetland nitrate nitrogen sewage treatment system 10 also includes a filtering device. The filtering device includes a gravel filter layer 610 and a Y-type filter 620. The gravel filter layer 610 is laid on the surface of the wetland matrix 200. The thickness of the gravel filter layer 610 is 2 to 5 cm. The Y-type filter 620 is installed on the water outlet device 400. Specifically, the Y-type filter 620 can be selected from the Y-type filter 620. The gravel filter layer 610 can be replaced regularly to prevent surface clogging.

[0056] In some embodiments, the volume ratio of pyrite, volcanic rock and biochar is (1-5):(1-5):(1-5);

[0057] Preferably, in one embodiment, the volume ratio of pyrite, volcanic rock and biochar is 1:1:1.

[0058] In some embodiments, the water distribution device 300 includes a plurality of water distribution pipes. The plurality of water distribution pipes are spaced apart, the interval between adjacent water distribution pipes is 0.1 to 0.3 m, the length of the water distribution pipes is 0.5 to 1 m, and the water distribution pipes are provided with a plurality of water distribution holes, the interval between adjacent water distribution holes is 5 to 8 cm, and the aperture of the water distribution holes is 1 to 2 cm. When the water distribution pipes are in use, the water inlet temperature is controlled to be higher than 10°C.

[0059] In some embodiments, the water outlet device 400 may be a water outlet pipe. The length of the water outlet pipe may be set according to the length of the water distribution pipe.

[0060] In some embodiments, the water distribution pipe may be a DN75 water distribution pipe. The water outlet pipe may be selected from a DN50 water outlet collection pipe. The water distribution pipe and the water outlet pipe generally have a diameter range of DN50 to DN175, which may be selected specifically according to the actual hydraulic load.

[0061] In some embodiments, the height of the wetland substrate 200 is 25-35 cm. For example, in one specific example, the height of the wetland substrate 200 is 25 cm; in another specific example, the height of the wetland substrate 200 is 35 cm.

[0062] In some embodiments, the height of the wetland pool body 100 is 35-45 cm. For example, in one specific example, the height of the wetland pool body 100 is 35 cm. In another specific example, the height of the wetland pool body 100 is 45 cm.

[0063] In some embodiments, the particle size of the wetland substrate 200 is 1 to 3 cm. For example, in one specific example, the particle size of the wetland substrate 200 is 1 cm; in another specific example, the particle size of the wetland substrate 200 is 3 cm.

[0064] In some embodiments, the planting density of the plants 500 is 16 to 20 plants / m 2 The planting density of the plant 500 can be set as needed. For example, in a specific embodiment, the planting density of the plant 500 is 16 plants / m 2 In another specific embodiment, the planting density of the plants 500 is 20 plants / m 2 .

[0065] In some embodiments, the plant 500 is selected from one or more of canna, reed, iris and windmill grass.

[0066] In some embodiments, the method for preparing the wetland substrate 200 includes the following steps:

[0067] One or more of bamboo, reed and iris are roasted in a muffle furnace at 300-400° C., and then crushed after cooling to form biochar.

[0068] In some of the embodiments, the matrix particle sizes of pyrite, volcanic rock, and biochar are each independently controlled within the range of 1 to 3 cm to increase the specific surface area.

[0069] The pyrite raw material is treated by soaking in 1 mol hydrochloric acid for 1 to 2 hours, and then placed in a cool place for air drying, and the matrix particle size is screened to obtain pyrite.

[0070] The volcanic rock raw material is soaked in 1 mol hydrochloric acid for 1 to 2 hours, placed in a cool place for air drying, and the matrix particle size is screened to obtain the volcanic rock.

[0071] The above-mentioned autotrophic denitrification surface subsurface flow constructed wetland system 10 for treating nitrate nitrogen sewage, by controlling the structure of the artificial wetland pool 100 and the matrix composition, obtains autotrophic denitrifying bacteria in situ culture, improves the metabolism of autotrophic denitrifying bacteria, strengthens the chemical reaction between divalent iron and nitrite nitrogen, and inhibits the metabolism of potential heterotrophic denitrifying bacteria, so that the nitrogen oxides entering the autotrophic denitrification surface subsurface flow constructed wetland system 10 for treating nitrate nitrogen are reduced to nitrogen gas by autotrophic denitrifying bacteria and chemical reaction and enter the environment. The present invention can efficiently degrade pollutants, is simple to operate, easy to implement, does not require power and external carbon source, has no strict requirements on operating conditions, and can realize sulfur autotrophic denitrification reaction under set conditions; the redox reaction of divalent iron and nitrite nitrogen, and the competitive inhibition of Geobacter on anaerobic heterotrophic denitrifying bacteria, realize the biological denitrification process dominated by autotrophic denitrification in the surface subsurface flow constructed wetland, and can be used to remove nitrate nitrogen in the tail water of sewage treatment plants without the need to supplement organic carbon and additional power. In addition, the present invention can be used in wetland parks to purify rainwater and landscape water, bringing more ecological benefits and providing a place for rest for the public.

[0072] Another embodiment of the present application provides a method for treating nitrate-nitrogen wastewater using an autotrophic denitrification subsurface artificial wetland.

[0073] A method for treating nitrate nitrogen wastewater using an autotrophic denitrification subsurface artificial wetland comprises the following steps:

[0074] Providing an oxygen environment for the autotrophic denitrification type surface subsurface flow constructed wetland treatment of nitrate nitrogen sewage system 10 through plants 500;

[0075] The sewage enters the wetland pool 100 through the water distribution device 300, and the nitrate nitrogen in the sewage is reduced to nitrogen gas by the Thiobacillus genus. The Thiobacillus genus also reduces part of the nitrate nitrogen to nitrite nitrogen and ammonia nitrogen.

[0076] Ammonia nitrogen in sewage is oxidized to nitrite nitrogen and nitrate nitrogen. Pyrite and volcanic rock provide divalent iron ions to react with nitrite nitrogen to generate nitrogen gas. Pyrite and volcanic rock provide sulfide to promote the growth of sulfur-reducing bacteria Desulfovibrio, Desulfobulbus and Thiobacillus. Among them, sulfur-reducing bacteria Desulfovibrio and Desulfobulbus can reduce nitrate nitrogen through sulfide and / or organic matter as electron donors, and their reduction product ammonia nitrogen can be re-oxidized to nitrite nitrogen and nitrate nitrogen, while Thiobacillus can use sulfur as an electron donor to completely reduce nitrate nitrogen to nitrogen gas, or reduce part of nitrate nitrogen to ammonia nitrogen.

[0077] Biochar can enhance interspecies electron transfer, promote the growth and metabolism of sulfur-reducing bacteria Desulfovibrio and Desulfobulbus, and promote Thiobacillus to reduce nitrate nitrogen to nitrogen gas. Biochar can also improve the growth and metabolism of Geobacter, increase the intensity of the reaction of heterologous nitrate nitrogen reduction to ammonia nitrogen, and competitively inhibit the anaerobic heterotrophic denitrification process.

[0078] In some embodiments, the total nitrogen concentration of sewage is not greater than 30 mg / L, the hydraulic retention time is 2 to 6 hours, and the temperature is controlled to be greater than 10° C. The entire operation process of the system of the present invention does not require power drive, and the fluid flows from the water distribution pipe to the outlet pipe through gravity flow. In addition, sulfur-reducing bacteria Thiobacillus, Desulfovibrio, and Desulfobulbus have good adaptability to dissolved oxygen concentration, and can enhance dissolved oxygen concentration by changing saturated / dry and wet conditions, alleviate surface blockage, and extend the service life of the autotrophic denitrification surface subsurface flow artificial wetland. In the present invention, for sewage types with a nitrate nitrogen concentration of no more than 30 mg / L, such as sewage plant tail water mainly composed of nitrate nitrogen, the present invention can adapt to the flow change and efficiently reduce the nitrate nitrogen to nitrogen gas, so as to achieve the following beneficial effects: (1) competitive inhibition of heterotrophic denitrifying bacteria by Geobacter; (2) nitrate nitrogen reduction mainly by sulfur autotrophic denitrifying bacteria, so that the system maintains a high nitrate nitrogen removal effect; (3) chemical reduction reaction of divalent iron and nitrite nitrogen, with divalent iron as an electron donor, without the participation of microorganisms; (4) in situ enrichment culture to obtain microbial genera such as Geobacter and sulfur autotrophic denitrifying bacteria.

[0079] In some of the embodiments, the dissolved oxygen concentration of the autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen in sewage 10 is controlled to be maintained at 1.2-2.8 mg / L.

[0080] Example 1

[0081] The present embodiment provides a method for treating nitrate nitrogen wastewater by using an autotrophic denitrification type surface subsurface flow artificial wetland. The object of treatment in the present embodiment is Dinggang Lake in Shenzhen City, Guangdong Province. The tail water of the sewage treatment plant is used as the main water replenishment. The chemical oxygen demand in the influent is 20.4-30.6 mg / L, nitrate nitrogen is 9.3-11.3 mg / L, and total phosphorus is 4.2-4.6 mg / L. An autotrophic denitrification type surface subsurface flow artificial wetland system 10 for treating nitrate nitrogen wastewater is set at the tail water inlet of Dinggang Lake.

[0082] The autotrophic denitrification type surface subsurface flow artificial wetland treatment nitrate nitrogen sewage system 10 includes a wetland pool body 100, a wetland matrix 200, a water distribution device 300, a water outlet device 400, a filtering device and a plant 500. The wetland matrix 200 is filled in the wetland pool body 100. The height of the wetland pool body 100 is 40 cm, the length is 1 m, and the width is 2 m. The wetland matrix 200 includes pyrite, volcanic stone and biochar. One or more of bamboo, reed bamboo and iris are roasted at 350°C in a muffle furnace, and then crushed to form biochar after cooling. The matrix particle size of pyrite, volcanic stone and biochar is independently controlled within the range of 2 cm to increase the specific surface area. After the pyrite raw material is soaked in 1 mol of hydrochloric acid for 1 hour, it is placed in a cool place to air dry, and the matrix particle size is screened to obtain pyrite. The volcanic rock raw material was soaked in 1 mol of hydrochloric acid for 1 hour, placed in a cool place to air-dry, and the matrix particle size was screened to obtain volcanic rock. The particle size of the wetland matrix 200 was 2 cm; pyrite, volcanic rock and biochar were mixed in a volume ratio of 1:1:1 and filled into the wetland pool 100 until the height of the wetland matrix 200 was 30 cm.

[0083] The water distribution device 300 is located at the top of the wetland pool body 100 to distribute water into the wetland pool body 100. The water outlet device 400 is located at the bottom of the wetland pool body 100 to collect treated sewage. The water distribution device 300 includes a plurality of water distribution pipes, which are spaced apart, and the interval between adjacent water distribution pipes is 0.2m. The length of the water distribution pipe is 0.5m. The water distribution pipe is provided with a plurality of water distribution holes, and the spacing between adjacent water distribution holes is 5cm. The aperture of the water distribution hole is 1cm. When the water distribution pipe is in use, the inlet water temperature is controlled to be higher than 10°C. The water distribution pipe is a DN75 water distribution pipe. The outlet pipe is a DN50 outlet collection pipe.

[0084] Plant 500 windmill grass is planted in the wetland matrix 200, and the planting density of plant 500 is 16 plants / m 2 .

[0085] The gravel filter layer 610 is laid on the surface of the wetland matrix 200 , the thickness of the gravel filter layer 610 is 3 cm, the Y-type filter 620 is installed on the water outlet device 400 , and the Y-type filter 620 is selected from the Y-type filter 620 .

[0086] The hydraulic retention time of this embodiment is set to 4 hours, the total nitrogen concentration of the sewage is not greater than 30 mg / L, and the temperature is controlled to be greater than 10°C.

[0087] The method for treating nitrate nitrogen wastewater using an autotrophic denitrification subsurface artificial wetland comprises the following steps:

[0088] Providing an oxygen environment for the autotrophic denitrification type surface subsurface flow constructed wetland treatment of nitrate nitrogen sewage system 10 through plants 500;

[0089] The sewage is added into the wetland pool 100 through the water distribution device 300, and the nitrate nitrogen in the sewage is reduced to nitrogen gas by Thiobacillus;

[0090] Ammonia nitrogen in sewage is oxidized to nitrite nitrogen and nitrate nitrogen. Pyrite and volcanic rock provide divalent iron ions to react with nitrite nitrogen to generate nitrogen gas. Pyrite and volcanic rock provide sulfide to promote the growth of sulfur-reducing bacteria Desulfovibrio, Desulfobulbus and Thiobacillus. Among them, sulfur-reducing bacteria Desulfovibrio and Desulfobulbus can reduce nitrate nitrogen through sulfide and / or organic matter as electron donors, and their reduction product ammonia nitrogen can be re-oxidized to nitrite nitrogen and nitrate nitrogen, while Thiobacillus can use sulfur as an electron donor to completely reduce nitrate nitrogen to nitrogen gas, or reduce part of nitrate nitrogen to ammonia nitrogen.

[0091] Biochar can enhance interspecies electron transfer, promote the growth and metabolism of sulfur-reducing bacteria Desulfovibrio and Desulfobulbus, and promote Thiobacillus to reduce nitrate nitrogen to nitrogen gas. Biochar can also improve the growth and metabolism of Geobacter, increase the intensity of the reaction of heterologous nitrate nitrogen reduction to ammonia nitrogen, and competitively inhibit the anaerobic heterotrophic denitrification process.

[0092] After a period of operation, the relative abundance of Thiobacillus fluctuated between 2.66% and 4.36%, the relative abundance of Desulfobulbus changed between 0.753% and 1.01%, the relative abundance of Desulfovibrio changed between 0.615% and 1.43%, and the relative abundance of Geobacter was between 1.06% and 1.54%, and the relative abundance of the main denitrifying bacteria Thauera was between 0.71% and 1.43%, which means that the sulfur autotrophic denitrification process is the main nitrate nitrogen removal mechanism. After 120 days of operation monitoring, the nitrate nitrogen removal rate was between 52.3% and 78.9%, the total phosphorus removal efficiency was between 43.2% and 82.6%, and the total chemical oxygen demand removal rate was between 47.3% and 73.6%.

[0093] Example 2

[0094] This embodiment sets up a laboratory simulation autotrophic denitrification type surface subsurface flow artificial wetland treatment nitrate nitrogen sewage system 10. The autotrophic denitrification type surface subsurface flow artificial wetland treatment nitrate nitrogen sewage system 10 of this embodiment is basically the same as that of Example 1, except that the height of the wetland pool 100 is 40 cm, the length is 20 cm, the width is 40 cm, and the volume ratio of volcanic rock: pyrite: biochar is 2:2:1. The hydraulic retention time is set to 24 hours, the water inlet conditions are set to total chemical oxygen demand 3 mg / L, ammonia nitrogen 15 mg / L, nitrate nitrogen 10 mg / L, and other process parameters are the same as those of Example 1.

[0095] During the whole test period, water samples were taken every 7 days to measure the total nitrogen, ammonia nitrogen and chemical oxygen demand content, and the corresponding effluent water quality could reach the fourth category standard of surface water environmental quality (GB 3838-2002). In addition, the relative abundance of sulfur autotrophic denitrifying bacteria Thiobacillus, Desulfovibrio, and Desulfobulbus in the microbial community was 2.4% to 4.3%, 1.12% to 2.17%, and 1.67% to 2.46%, the relative abundance of Geobacter was 0.4% to 1.1%, and the relative abundance of the main anaerobic denitrifying bacteria Thauera was 0.7% to 1.2%. The laboratory simulated miniaturized autotrophic denitrifying surface subsurface flow artificial wetland nitrate nitrogen sewage treatment system 10 of this embodiment 2 can meet the requirements of treating nitrate nitrogen sewage.

[0096] Example 3

[0097] This embodiment sets up a laboratory simulation autotrophic denitrification type surface subsurface flow artificial wetland treatment nitrate nitrogen sewage system 10. The autotrophic denitrification type surface subsurface flow artificial wetland treatment nitrate nitrogen sewage system 10 of this embodiment is basically the same as that of Example 1, except that the height of the wetland pool 100 is 40 cm, the length is 20 cm, the width is 40 cm, and the volume ratio of volcanic rock: pyrite: biochar is 2:2:1. The hydraulic retention time is set to 24 hours, and the inlet conditions are set to 3 mg / L total chemical oxygen demand, 35 mg / L ammonia nitrogen, and 10 mg / L nitrate. Other process parameters are the same as those of Example 1.

[0098] During the 120-day test period, water samples were taken every 7 days to measure the total nitrogen, ammonia nitrogen and chemical oxygen demand in the effluent. The corresponding water quality can meet the fourth category standard of surface water environmental quality (GB 3838-2002). The relative abundance of sulfur autotrophic denitrifying bacteria Thiobacillus, Desulfovibrio and Desulfobulbus in the microbial community is 0.7% to 4.37%, 0.0582% to 1.43% and 0.0514% to 1.02%, while the relative abundance of Geobacter is 0.3% to 0.9%, and the relative abundance of the main anaerobic denitrifying bacteria Thauera is 0.161% to 1.53%. The laboratory simulated miniaturized autotrophic denitrification surface subsurface flow artificial wetland nitrate nitrogen sewage treatment system 10 of this embodiment 3 can meet the requirements of treating nitrate nitrogen sewage.

[0099] In summary, the above-mentioned method for treating nitrate nitrogen sewage by using an autotrophic denitrifying surface subsurface flow constructed wetland is based on the existing surface subsurface flow constructed wetland. By controlling the substrate height, pool height, substrate composition and ratio of the surface subsurface flow constructed wetland, the growth and metabolism of sulfur autotrophic denitrifying bacteria are promoted, and the competitive advantage of Geobacter over heterotrophic anaerobic denitrifying bacteria is utilized to inhibit the growth of anaerobic heterotrophic denitrifying bacteria, so that nitrate nitrogen is not reduced through the heterotrophic denitrification process, thereby promoting the growth of autotrophic denitrifying bacteria; at the same time, the ammonia nitrogen generated by the reduction of nitrate nitrogen by Geobacter is re-oxidized to nitrate nitrogen due to the high dissolved oxygen concentration (1.2-2.8 mg / L) of this artificial wetland system, and is further reduced to nitrogen gas by autotrophic denitrifying bacteria. In addition, the rich divalent iron in the substrate gradation can strengthen the reduction reaction of divalent iron and nitrite nitrogen, and further directly reduce nitrite nitrogen to nitrogen gas through chemical reaction. Through the above measures, sulfur autotrophic denitrifying bacteria and Geobacter are obtained by in situ culture. The sulfur autotrophic denitrifying bacteria carry out autotrophic denitrification, and Geobacter inhibits the growth and metabolism of heterotrophic denitrifying bacteria and indirectly provides nitrate nitrogen for the former. It can also carry out chemical reduction reaction of divalent iron and nitrite nitrogen to further reduce nitrogen oxides to nitrogen gas. In addition, the present invention reduces organic matter accumulation, improves wetland porosity and extends wetland service life by maintaining a relatively high dissolved oxygen concentration (1.2-2.8 mg / L).

[0100] Compared with the traditional technology, the present invention has the following beneficial effects:

[0101] (1) By controlling the height of the wetland pool 100 and the wetland matrix 200, planting plants 500 at a higher density, and strengthening the oxygen exchange process between the interface of the wetland matrix 200 and the air, as well as the oxygen secretion of the roots of the plants 500, the reoxygenation level of the entire surface subsurface flow artificial wetland process is improved.

[0102] (2) A good denitrification effect is achieved, with a denitrification rate of 50% to 80%, and there is no need to add organic matter as an electron donor. The ammonia nitrogen entering the system of the present invention is converted into nitrite nitrogen and nitrate nitrogen through nitrification. Nitrite nitrogen can be reduced to nitrogen gas by reacting with divalent iron, and nitrate nitrogen is reduced to nitrogen gas by autotrophic denitrifying bacteria. Due to the competitive advantage of Geobacter, anaerobic heterotrophic denitrifying bacteria are difficult to obtain the nitrate nitrogen required for growth, and nitrogen oxides are mostly reduced to nitrogen gas by autotrophic denitrifying Thiobacillus.

[0103] (3) The matrix gradation plays a key role in the in-situ cultivation of autotrophic denitrifying Thiobacillus and Geobacter. The treated pyrite and volcanic rock can provide elemental sulfur as an electron donor to promote the growth of sulfur autotrophic denitrifying bacteria, and provide iron to promote the reaction of divalent iron with nitrite nitrogen. More importantly, the two act synergistically with biochar to significantly promote the reduction reaction of heterologous nitrate nitrogen and increase the number of Geobacter colonies (increase by about 30% to 60%). The three matrices are matched according to a certain gradation, and the reoxygenation level of the process itself can make the autotrophic denitrifying bacteria and Geobacter the dominant species in the microbial community (relative abundance of microbial community 5% to 8%), which is also the key to the removal of nitrate nitrogen by autotrophic denitrification.

[0104] (4) Based on the principle of aerobic phosphorus absorption and anaerobic phosphorus release, the present invention adopts a relatively high reoxygenation level to maintain the activity of the polyphosphate bacteria in this process, that is, it can remove the phosphorus element entering the pool through the biological phosphorus removal process; in addition, it is also beneficial to the oxidative decomposition of organic matter, reducing the blockage that may be formed in the wetland matrix (reduction rate of 20% to 40%), and improving the permeability of the artificial wetland, thereby extending the service life of the artificial wetland and creating greater engineering and environmental value.

[0105] (5) The autotrophic denitrification subsurface flow constructed wetland changes the anaerobic habitat required for the normal metabolism of methanogens by maintaining a high reoxygenation level, inhibits the metabolism of methanogens (depending on the dissolved oxygen concentration), and reduces the methane produced in the process of water purification, thereby achieving the purpose of reducing greenhouse gas methane emissions. In addition, the reduction of nitrate nitrogen by autotrophic denitrification and nitrite nitrogen by divalent iron reduces the generation of greenhouse gas nitrous oxide during heterotrophic denitrification.

[0106] (6) The method of the present invention can completely solve the problems in traditional artificial wetlands that are not suitable for large-scale wetlands, or cannot guarantee good engineering effects, and have high maintenance costs and difficult processes. This method is not only suitable for treating nitrate nitrogen wastewater, such as sewage plant tail water, but can also be used in wetland parks and other environments to treat rainwater, reclaimed water and other wastewater containing nitrogen oxides. By changing the operating conditions, good purification effects can also be achieved.

[0107] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0108] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An autotrophic denitrification type surface subsurface flow artificial wetland system for treating nitrate nitrogen wastewater, characterized in that: The autotrophic denitrification type surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage comprises a wetland pool, a wetland matrix, a water distribution device, a water outlet device and wetland plants; the wetland matrix is ​​filled in the wetland pool, and the wetland matrix comprises pyrite, volcanic rock and biochar, wherein the preparation method of the wetland matrix comprises the following steps: preparing biochar, soaking the pyrite raw material with 1 mol of hydrochloric acid for 1 to 2 hours, placing it in a cool place to air dry, screening the matrix particle size to obtain pyrite, soaking the volcanic rock raw material with 1 mol of hydrochloric acid for 1 to 2 hours, placing it in a cool place to air dry, screening the matrix particle size to obtain volcanic rock; the water distribution device is located on the matrix surface of the wetland pool, and the incoming water enters the pool through the water distribution device and is discharged in a gravity flow manner; the water outlet device is located at the bottom of the wetland pool; the wetland plants are planted in the wetland matrix; the dissolved oxygen concentration of the autotrophic denitrification type surface subsurface flow artificial wetland system for treating nitrate nitrogen sewage is maintained at 1.2~2.8 mg / L, in order to create a dissolved oxygen environment that is conducive to the growth and metabolism of autotrophic denitrifying bacteria, but not conducive to the growth of heterotrophic anaerobic denitrifying bacteria, using Geobacter Geobacter The competitive advantage of heterotrophic anaerobic denitrifying bacteria inhibits the growth of anaerobic heterotrophic denitrifying bacteria, so that nitrate nitrogen is not reduced through heterotrophic denitrification, thereby promoting the growth of autotrophic denitrifying bacteria, using sulfur-reducing bacteria Desulfovibrio and Desulfobulbus to reduce nitrate nitrogen through sulfide and / or organic matter as electron donors, and using Geobacter Geobacter Ammonia nitrogen generated by reducing nitrate nitrogen; when the autotrophic denitrifying surface subsurface flow constructed wetland system for treating nitrate nitrogen sewage is in operation, the hydraulic retention time is controlled to ensure that the nitrate nitrogen in the influent is fully in contact with the autotrophic denitrifying bacteria Thiobacillus and reduced to nitrogen gas.

2. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater according to claim 1, characterized in that: The autotrophic denitrification surface subsurface flow artificial wetland system for treating nitrate-nitrogen sewage also includes a filtering device, which includes a gravel filter layer and a Y-type filter. The gravel filter layer is laid on the surface of the wetland matrix, the thickness of the gravel filter layer is 2 to 5 cm, and the Y-type filter is installed on the water outlet device.

3. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater according to claim 1, characterized in that: The volume ratio of the pyrite, the volcanic rock and the biochar is (1 ~ 5): (1 ~ 5): (1 ~ 5).

4. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater according to claim 3, characterized in that: The volume ratio of the pyrite, the volcanic rock and the biochar is 1:1:

1.

5. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater according to claim 1, characterized in that: The water distribution device comprises a plurality of water distribution pipes, the plurality of water distribution pipes are distributed at intervals, and the water distribution pipes are provided with a plurality of water distribution holes.

6. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater according to claim 5, characterized in that: Also includes at least one of the following technical features: The interval between adjacent water distribution pipes is 0.1 to 0.3 m; The length of the water distribution pipe is 0.5 to 1 m; The spacing between adjacent water distribution holes is 5 to 8 cm, and the aperture of the water distribution holes is 1 to 2 cm.

7. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater according to any one of claims 1 to 6, characterized in that: Also includes at least one of the following technical features: The height of the wetland substrate is 25 to 35 cm; The height of the wetland pool is 35 to 45 cm; The particle size of the wetland matrix is ​​1 to 3 cm.

8. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate-nitrogen wastewater according to any one of claims 1 to 6, characterized in that: Also includes at least one of the following technical features: The planting density of the plants is 16 to 20 plants / m 2 ; The plants are selected from one or more of canna, reed, iris and windmill grass.

9. The autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater according to any one of claims 1 to 6, characterized in that: The preparation of biochar comprises the following steps: roasting one or more of bamboo, reed, and iris in a muffle furnace at 300° C. to 400° C., and then crushing the mixture after cooling to form the biochar; And / or, the matrix particle sizes of the pyrite, the volcanic rock, and the biochar are each independently controlled within the range of 1 to 3 cm to increase the specific surface area.

10. A method for treating a nitrate nitrogen wastewater system using the autotrophic denitrification subsurface flow constructed wetland according to any one of claims 1 to 9, characterized in that: The steps include: Providing a dissolved oxygen environment for the autotrophic denitrification subsurface flow artificial wetland to treat nitrate nitrogen sewage system through plants; The sewage is added to the wetland pool through the water distribution device, and the sulphobacillus Thiobacillus Reducing nitrate nitrogen in sewage to nitrogen gas; Ammonia nitrogen in sewage is oxidized to generate nitrite nitrogen and nitrate nitrogen. Pyrite and volcanic rock provide divalent iron ions to react with nitrite nitrogen to generate nitrogen gas. Pyrite and volcanic rock provide sulfide to promote sulfur-reducing bacteria. Desulfovibrio, Desulfobulbus and Thiobacillus Growth; among them, sulfur-reducing bacteria Desulfovibrio, Desulfobulbus Nitrate nitrogen can be reduced by sulfide and / or organic matter as electron donors, and the reduced product ammonia nitrogen can be reoxidized to nitrite nitrogen and nitrate nitrogen. Thiobacillus Sulfur can be used as an electron donor to completely reduce nitrate nitrogen to nitrogen gas, or partially reduce nitrate nitrogen to ammonia nitrogen; Enhanced interspecific electron transfer by biochar promotes the growth of sulfur-reducing bacteria Desulfovibrio , Desulfobulbus growth metabolism, while promoting Thiobacillus Thiobacillus Reducing nitrate to nitrogen gas, biochar can also increase the activity of Geobacter Geobacter growth metabolism, increase the intensity of the reaction of heterologous nitrate nitrogen reduction to ammonia nitrogen, and competitively inhibit the anaerobic heterotrophic denitrification process.

11. The method for treating nitrate nitrogen wastewater system using an autotrophic denitrification subsurface artificial wetland according to claim 10, characterized in that: The total nitrogen concentration of sewage is no more than 30 mg / L, the hydraulic retention time is 2 to 6 hours, and the temperature is controlled to be greater than 10°C.

12. The method for treating nitrate nitrogen wastewater system using an autotrophic denitrification subsurface flow constructed wetland according to claim 10, characterized in that: The dissolved oxygen concentration of the autotrophic denitrification subsurface flow constructed wetland system for treating nitrate nitrogen wastewater is controlled to be maintained at 1.2 to 2.8 mg / L.

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