An artificial wetland sewage treatment system for enhancing nitrogen and phosphorus removal in wetland matrix and its application

Abstract

The present invention proposes an artificial wetland sewage treatment system and application for strengthening the denitrification and phosphorus removal of wetland matrix, and belongs to the technical field of sewage treatment. The artificial wetland sewage treatment system for strengthening the denitrification and phosphorus removal of wetland matrix of the present invention comprises an artificial wetland reaction zone, and the artificial wetland reaction zone is a left-right segmented structure, and is filled with limestone, zeolite and modified ceramsite matrix from front to back along the water flow direction according to a filling mode of x:y:z by volume, wherein (x+y):z=3:1. By changing the mixing ratio and filling mode of the wetland matrix, the present invention can carry out targeted decontamination and quality improvement for water with different characteristics, and can also effectively alleviate the adsorption saturation of the wetland matrix and reduce the number of times the wetland matrix is ​​cleaned or replaced.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to an artificial wetland sewage treatment system for strengthening nitrogen and phosphorus removal in a wetland matrix and its application. Background Art

[0002] With the rapid development of modernization, the scale of sewage treatment has increased. Although a series of measures such as oxidation ditch and activated sludge method have made great progress in sewage treatment, the current water environment quality is still not optimistic and the situation of water pollution prevention and control is severe. As an environmentally friendly sewage treatment technology with low investment, low energy consumption, strong impact resistance and simple operation and management, artificial wetlands have been widely used in water quality improvement and ecological function restoration. Different artificial wetland matrices have different removal capabilities for the same pollutants. Proportioning, combining and filling different matrices is conducive to enhancing the synergistic effect between matrices.

[0003] At present, there are many types of fillers in wetlands, which can be divided into three categories according to their sources and applications: natural materials, industrial and agricultural byproducts, and artificial synthetic matrix materials. Studies have shown that artificial wetland systems using a single matrix can no longer meet the needs of sewage purification. At the same time, a single type of matrix is ​​very likely to cause blockage, making it difficult to maintain the sustainable operation of artificial wetlands. Proportioning and combining different matrices is conducive to enhancing the synergistic effect between matrices.

[0004] The prior art usually adopts a combination of physical conditioning and chemical conditioning. For example, the patent with application number CN202410158914.4 discloses an enzyme biofuel cell artificial wetland sewage treatment system, which includes a pre-filter tank, an artificial wetland reaction zone and a post-filter tank. The sewage is input from the pre-filter tank to the artificial wetland reaction zone through the sewage propulsion pump. The artificial wetland reaction zone is an upper and lower stacked structure, including: a gravel filter layer; a first fine sand filter layer; an anode composite reaction layer; a second fine sand filter layer; a porous expanded clay shaping layer; a cathode composite reaction layer; the anode composite reaction layer and the cathode composite reaction layer are electrically connected by a wire. This technology adapts to the growth needs of aquatic plants at different depths and enriches the biodiversity of artificial humidity. Aeration components, enzyme supply components and ultrasonic vibration devices are specifically arranged near the roots of aquatic plants to effectively improve the reaction efficiency of organisms. However, this technology requires electricity to improve the effect of sewage treatment, which increases the treatment cost and has low feasibility in field practice. The upper and lower filling modes can easily cause blockage of the wetland reactor, increasing the frequency and difficulty of substrate replacement and flushing, making it difficult to maintain the sustainable operation of the artificial wetland reactor.

[0005] Because the sewage conditions in different places are different, the matrix filling method will affect the unsaturated flow of water in the artificial wetland, the DO distribution after aeration, plant absorption and microbial activity, and thus affect the nitrification and denitrification process in the sewage, affecting the sewage treatment effect. In combination with the actual situation, factors that affect the matrix treatment effect, such as particle size, material, denitrification and phosphorus removal effects, should be fully considered to select the appropriate matrix type, mixing ratio and filling mode. In view of this, how to provide a technology that uses matrix ratios and filling modes to improve the efficiency of sewage denitrification and phosphorus removal is a technical problem that people in this field urgently need to solve. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes an artificial wetland sewage treatment system and application for strengthening nitrogen and phosphorus removal in wetland matrix.

[0007] To achieve the above-mentioned purpose, the present invention provides an artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal, including an artificial wetland reaction zone, wherein the artificial wetland reaction zone is a left-right segmented structure, and is filled with limestone, zeolite and modified ceramsite matrix from front to back along the water flow direction according to a filling pattern of x:y:z in a volume ratio, wherein (x+y):z=3:1.

[0008] Beneficial effects: The present invention can reduce the blockage of the wetland bed and maximize the hydraulic conductivity by arranging different types of substrates at different positions, and maximize the advantages of each section of the substrate. Since phosphorus in sewage is mainly removed by physical adsorption of the substrate, microorganisms and plants have little effect on its removal. Specifically:

[0009] (1) Limestone is a "pioneer". Its small particle size can effectively intercept suspended solids, reduce the concentration of SS (suspended solids), and ensure the uniform distribution of pollutants. It contains active substances such as iron, aluminum, calcium and magnesium. 3+ 、Al 3+ , Ca 2+ and Mg 2+ Metal ions, metal oxides and hydroxides, and clay minerals react with phosphates in water to form insoluble Ca-P precipitates through coordination exchange, which are discharged from the reactor with water or absorbed by plants and microorganisms, thereby reducing the impact of phosphorus pollutants on nitrogen removal and organic matter removal from the matrix. This reaction will produce a large amount of -OH, which will increase the overall pH, which is conducive to providing the most suitable growth environment for nitrifying and denitrifying bacteria, and lay the foundation for the subsequent removal of ammonia nitrogen and organic matter by zeolite and modified ceramsite in sewage.

[0010] (2) Zeolite, as the "main force", not only has a very obvious effect on the removal of ammonia nitrogen, but also has a low cost. In the previous stage, microorganisms absorb substances such as Ca-P, which enhances the activity of microorganisms. Zeolite and microorganisms can achieve synergistic nitrogen removal. At the same time, the porosity and specific surface area of ​​limestone and zeolite are greatly different. The difference in dissolved oxygen content between the two stages significantly improves the denitrification efficiency, promotes aerobic nitrification-denitrification and anaerobic ammonia oxidation, and thus improves the denitrification efficiency of the system. On the contrary, when passing through zeolite first and then limestone, the total phosphorus removal rate will decrease because the metal cations on the tetrahedral framework of zeolite are not tightly bound to aluminosilicate. Under the osmotic action of the solution, the metal oxides of zeolite will dissolve in the water and undergo ion exchange reactions with free ammonium ions. However, since it cannot form a stable precipitate like limestone, it may enter the interior of the limestone, reducing its steric hindrance, thereby affecting the adsorption and ion exchange performance, resulting in a decrease in phosphorus removal efficiency.

[0011] (3) As the "core", modified ceramsite has a large particle size and pores. Not only is it easy to adsorb nitrogen and phosphorus pollutants on the surface, but the algae growing on the surface layer will also adsorb nitrogen and phosphorus elements in the sewage. It can also release oxygen. Its pores are large, and the corresponding oxygen flow rate is large, which is conducive to the rapid recovery of dissolved oxygen and promotes the aerobic decomposition of organic matter by microorganisms. While improving the nitrification effect, the high oxygen environment is also very conducive to the growth and metabolic activity of Pseudomonas, accelerating the degradation of tetracycline in wastewater. Pseudomonas can use a specific enzyme system to oxidize and reduce tetracycline to produce non-toxic compounds. Therefore, using modified ceramsite as the last link can make a deeper treatment of the previous adsorption results. The generated non-toxic compounds will also flow out of the reactor with the water flow, reducing the adsorption of ammonia nitrogen, total phosphorus and organic matter. The reoxygenation speed is fast, which is conducive to stabilizing the effluent water quality. On the contrary, placing modified ceramsite in the front stage of the reaction will reduce oxygen activity, which is not conducive to the growth of Pseudomonas, thereby limiting the removal of tetracycline and the discharge of non-toxic compounds.

[0012] Furthermore, when the mass ratio of nitrogen and phosphorus in the influent water is 60 or above, x:y=1:2; when the mass ratio of nitrogen and phosphorus in the influent water is between 40-60 (excluding 40 and 60), x:y=1:1; when the mass ratio of nitrogen and phosphorus in the influent water is 40 or below, x:y=2:1.

[0013] Beneficial effect: The volume ratio of the filling matrix in the present invention can be used to remove pollutants in a targeted manner according to the characteristics of the sewage water quality. For example, when treating sewage water with serious excess of total phosphorus, the filling ratio of limestone can be increased.

[0014] The more serious the pollution, the greater the proportion (x); similarly, when treating sewage with serious ammonia nitrogen exceeding the standard, the filling ratio of zeolite can be increased. The more serious the pollution, the greater the proportion (y). This ratio is conducive to the rapid formation of biofilm and helps to remove conventional and new pollutants. The decontamination capacity of the artificial wetland matrix layer can be improved as a whole through the complementary effect, so that different matrices can play different treatment effects, and the combined matrix can be used to achieve the effect of comprehensively purifying various pollutants in sewage.

[0015] Furthermore, the pore sizes of the limestone, zeolite and modified ceramsite matrix are all 1 μm-100 μm.

[0016] Beneficial effects: The wetland matrix with a pore size of 1 μm-100 μm used in the present invention has the characteristics of high specific surface area, durability, high porosity, etc., moderate density, high matrix permeability coefficient, and can effectively intercept microorganisms and form a stable biofilm structure to protect microorganisms from external scouring. It increases the sewage retention time and the removal efficiency of conventional and new pollutants, and selects an optimal balance between purification effect and prevention of clogging.

[0017] Furthermore, the ratio of the filling volume of the matrix to the working volume of the artificial wetland reaction zone reactor is (60-70):100, and the effective filling height is 0.6-1.0m.

[0018] Beneficial effects: The use of a wetland matrix dosage of 60-70% in the present invention can significantly promote the efficient removal of pollutants, especially new pollutants such as tetracycline in sewage. If the wetland matrix dosage exceeds 70%, it will not have much effect on improving the removal efficiency.

[0019] Furthermore, the modified ceramsite is prepared by soaking the biological ceramsite in 3-6 mol / L NaOH solution and 2-5 mol / L AlCl3 solution for 48 hours.

[0020] Beneficial effects: The modified ceramsite in the wetland matrix has a pore size of 1μm-100μm after modification, which is 3-4 times the specific surface area of ​​the unmodified biological ceramsite, and the porosity is increased by 57%. Its particle size is large, the porosity is high, and the nitrogen and phosphorus elements are adsorbed on the surface, so the algae can grow in a coupled manner on its surface layer. During the growth of the algae, it not only adsorbs the nitrogen and phosphorus elements in the sewage, but also releases oxygen to improve the nitrification effect, laying the foundation for entering the subsequent anoxic area to achieve efficient denitrification. The modified ceramsite uses Ca-P and Al-P as the main forms of precipitated phosphorus. The modified biological ceramsite increases the removal rate of tetracycline by 66%, mostly by utilizing the metabolic activity of algae and Pseudomonas to accelerate the degradation of tetracycline in wastewater. Because it has a specific enzyme system for decomposing tetracycline molecules, it can decompose tetracycline into non-toxic compounds through redox reactions.

[0021] Furthermore, it also includes a front water distribution area and a rear water collection area. The sewage enters the treatment system through the front water distribution area. The water inlet end of the artificial wetland reaction area is connected to the front water distribution area, and the water outlet end of the artificial wetland reaction area is connected to the rear water collection area.

[0022] Furthermore, a water inlet baffle is provided between the water inlet end of the artificial wetland reaction zone and the front water distribution interval, and a water collection baffle is provided between the water outlet end of the artificial wetland reaction zone and the rear water collection interval. The water inlet baffle and the water collection baffle are both transparent acrylic plates, and the use of the baffle can prevent the matrix from being dispersed by water and allow water to pass through.

[0023] Furthermore, the artificial wetland sewage treatment system is also provided with an overflow device, and the overflow water is directly discharged back to the clear water tank of the sewage treatment station through a hose.

[0024] Beneficial effects: By setting up an overflow device, a stable dynamic continuity can be formed, the uniformity of the flow field of the artificial wetland matrix layer can be improved, the dead water area can be effectively reduced, short-circuit phenomenon can be avoided, the blockage of the wetland bed can be reduced, and the sewage retention time and microbial biomass as well as the removal efficiency of conventional and new pollutants can be increased.

[0025] The present invention also proposes the application of the artificial wetland sewage treatment system for strengthening the nitrogen and phosphorus removal of wetland matrix in improving the quality of tail water of sewage treatment plants.

[0026] Furthermore, sewage is first introduced into the artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal to promote microbial growth. After successful biofilm formation, soil is covered and plants are planted, and the artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal is continuously operated.

[0027] Furthermore, the removal effects of ammonia nitrogen and organic matter were used as evaluation indicators for successful biofilm formation.

[0028] Furthermore, the sewage first passes through the pre-distribution area, which can effectively reduce SS, and then passes through the artificial wetland reaction area, and finally the water is discharged from the catchment area. The influent concentration range basically meets the surface Class V water, and the types of pollutants that can be removed include conventional pollutants and new pollutants, including ammonia nitrogen, total phosphorus, organic matter and tetracycline.

[0029] Furthermore, the incoming water flow can rely on gravity flow to save energy, or it can use a pump to improve efficiency.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] (1) The artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal disclosed in the present invention uses three common matrix types mixed in different volume ratios, which has a synergistic enhancement effect. By changing the filling order of the wetland matrix, the microbial diversity and the removal capacity of conventional and new pollutants are greatly improved, which is beneficial to improving the quality of polluted water bodies.

[0032] (2) The sewage treatment system of the present invention adopts a left-right segmented, multi-segment matrix structure, which has a higher removal rate for COD (Chemical Oxygen Demand) and TSS (Total Soluble Solids) than a wetland system with a single matrix structure, and can form a complementary relationship between the matrices, which has a better effect on the removal of different pollutants. The artificial wetland based on the segmented filling matrix structure improves the uniformity of flow field distribution, can effectively reduce the volume of the retention area and dead zone, reduce the number of matrix replacements, save costs and increase service life. Improve the matrix retention performance, and at the same time avoid short-flow or overflow caused by organic matter directly flushing out of the system without being filtered by the matrix filler.

[0033] (3) The present invention can carry out targeted pollution removal and quality improvement for water with different characteristics by changing the mixing ratio and filling mode of the wetland matrix, and can also effectively alleviate the adsorption saturation of the wetland matrix and reduce the number of times the wetland matrix is ​​cleaned or replaced. In addition, the artificial wetland simulation reactor device used in the present invention is simple, occupies a small area, and the selected matrix type is low-cost and the filling mode is highly operable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0035] Figure 1 It is a front view of an artificial wetland sewage treatment system for enhancing nitrogen and phosphorus removal in a wetland matrix according to an embodiment of the present invention;

[0036] Figure 2A top view of an artificial wetland sewage treatment system for enhancing nitrogen and phosphorus removal in a wetland matrix according to an embodiment of the present invention;

[0037] Figure 3 It is a schematic structural diagram of a water inlet baffle and a water collection baffle in a constructed wetland sewage treatment system for enhancing nitrogen and phosphorus removal in a wetland matrix in an embodiment of the present invention;

[0038] Among them, 1 is the water inlet; 2-5 are water outlets with different height differences; 6 is the overflow pipe; 7 is the drain pipe; 8 is the water storage tank; 9 is the front water distribution area; 10 is the filling area; 11 is the rear water collection area; 12 is the water inlet baffle; 13 is the water collection baffle; 14 is limestone; 15 is zeolite; 16 is modified expanded clay; 17 is farmland soil; 18 is aquatic plants; 19 is the water hole. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] An embodiment of the present invention provides an artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal, including an artificial wetland reaction zone, wherein the artificial wetland reaction zone is a left-right segmented structure, and is filled with limestone, zeolite and modified ceramsite matrix from front to back along the water flow direction according to a filling pattern of x:y:z in a volume ratio, wherein (x+y):z=3:1.

[0045] In a preferred embodiment of the present invention, when the mass ratio of nitrogen and phosphorus in the influent water is 60 or above, x:y=1:2; when the mass ratio of nitrogen and phosphorus in the influent water is between 40-60 (excluding 40 and 60), x:y=1:1; when the mass ratio of nitrogen and phosphorus in the influent water is 40 or below, x:y=2:1.

[0046] In a preferred embodiment of the present invention, the pore sizes of the limestone, zeolite and modified ceramsite matrix are all 1 μm-100 μm.

[0047] In a preferred embodiment of the present invention, the ratio of the filling volume of the matrix to the working volume of the artificial wetland reaction zone reactor is (60-70):100, and the effective filling height is 0.6-1.0 m.

[0048] In a preferred embodiment of the present invention, the modified ceramsite is prepared by soaking the biological ceramsite in 3-6 mol / L NaOH solution and 2-5 mol / L AlCl3 solution for 48 hours. More specifically, the modified ceramsite used in the embodiment of the present invention is prepared by soaking the biological ceramsite in 5 mol / L NaOH solution and 4 mol / L AlCl3 solution for 48 hours.

[0049] In a preferred embodiment of the present invention, it also includes a front water distribution area and a rear water collection area. The sewage enters the treatment system through the front water distribution area. The water inlet end of the artificial wetland reaction zone is connected to the front water distribution area, and the water outlet end of the artificial wetland reaction zone is connected to the rear water collection area.

[0050] In a preferred embodiment of the present invention, a water inlet baffle is provided between the water inlet end of the artificial wetland reaction zone and the front water distribution interval, and a water collection baffle is provided between the water outlet end of the artificial wetland reaction zone and the rear water collection interval. The water inlet baffle and the water collection baffle are both transparent acrylic plates, and the use of the baffle can prevent the matrix from being dispersed by water and allow water to pass through.

[0051] In a preferred embodiment of the present invention, the artificial wetland sewage treatment system is further provided with an overflow device, and the overflow water is directly returned to the previous stage through a hose and enters the front water distribution area again.

[0052] The embodiment of the present invention also proposes the application of the artificial wetland sewage treatment system for enhancing the nitrogen and phosphorus removal of wetland matrix in improving the quality of tail water from a sewage treatment plant.

[0053] In a preferred embodiment of the present invention, sewage is first introduced into the artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal to promote microbial growth. After successful biofilm formation, soil is covered and plants are planted, and the artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal is continuously operated.

[0054] In a preferred embodiment of the present invention, the removal effect of ammonia nitrogen and organic matter is used as an evaluation index for successful biofilm formation.

[0055] In the preferred embodiment of the present invention, the sewage first passes through the pre-distribution area, which can effectively reduce SS, and then passes through the artificial wetland reaction area, and finally the water is discharged from the water collection area. The influent concentration range basically meets the surface Class V water, and the types of pollutants that can be removed include conventional pollutants and new pollutants, including ammonia nitrogen, total phosphorus, organic matter and tetracycline.

[0056] In a preferred embodiment of the present invention, the inlet water flow can rely on gravity flow to save energy, and can also use a pump to improve efficiency.

[0057] The physical properties of the modified ceramsite, zeolite and limestone used in the following examples of the present invention are as follows: the pore size of the modified ceramsite is 107.4 μm, and the average specific surface area is 27.88 m 2 / g, the average porosity is 60%, and the average pore volume is 0.15cm 3 / g, the pore size of zeolite is 83.6μm, and the average specific surface area is 19.02m 2 / g, the average porosity is 45%, and the average pore volume is 0.08cm 3 / g, the pore size of limestone is 42.2μm, and the average specific surface area is 15.95m 2 / g, the average porosity is 37%, and the average pore volume is 0.03cm 3 / g.

[0058] The structural schematic diagrams of the artificial wetland sewage treatment system for enhancing nitrogen and phosphorus removal in the wetland matrix according to the embodiment of the present invention are shown in Figure 1 and Figure 2 , Figure 1 For the main view, Figure 2 It is a top view, in which 1 is the water inlet; 2-5 are water outlets with different height differences; 6 is the overflow pipe; 7 is the drain pipe; 8 is the water storage tank; 9 is the front water distribution area; 10 is the filling area; 11 is the rear water collection area; 12 is the water inlet baffle; 13 is the water collection baffle; 14 is limestone; 15 is zeolite; 16 is modified expanded clay; 17 is farmland soil; and 18 is aquatic plants.

[0059] The structural schematic diagram of the water inlet baffle and the water collection baffle of the artificial wetland sewage treatment system for enhancing the nitrogen and phosphorus removal of the wetland matrix in the embodiment of the present invention is shown in Figure 3, among which 19 are water holes (all with a diameter of 1 cm).

[0060] The technical solution of the present invention is further illustrated by the following embodiments.

[0061] The sewage used in the following embodiments of the present invention is the effluent from the Beiyuhe Village Sewage Treatment Station of Beijing Bihai Environmental Technology Co., Ltd. After testing, the nitrogen-phosphorus mass ratio in the sewage used in Examples 1-3 of the present invention and Comparative Examples 1-4 is 73:1 (mass ratio is 60 or above), the nitrogen-phosphorus mass ratio in the sewage used in Example 4 is 92:2 (mass ratio is between 40-60), and the nitrogen-phosphorus mass ratio in the sewage used in Example 5 is 74:2 (mass ratio is 40 or below).

[0062] Example 1

[0063] An artificial wetland sewage treatment system for strengthening wetland matrix denitrification and phosphorus removal comprises a front water distribution area, an artificial wetland reaction area and a rear water collection area, the water inlet end of the artificial wetland reaction area is connected with the front water distribution area, the water outlet end of the artificial wetland reaction area is connected with the rear water collection area, a water inlet baffle is arranged between the water inlet end of the artificial wetland reaction area and the front water distribution area, a water collection baffle is arranged between the water outlet end of the artificial wetland reaction area and the rear water collection area, the water inlet baffle and the water collection baffle are both transparent acrylic plates, so that the matrix will not be dispersed by water and water can pass through, sewage enters the artificial wetland reaction area through the front water distribution area, and the outlet water overflows out of the sewage treatment system through the rear water collection area, the dimensions of the front water distribution area and the rear water collection area are length×width×depth=0.15m×0.35m×0.9m, and the dimensions of the artificial wetland reaction area are length×width×depth=1.4m×0.35m×0.9m;

[0064] Among them, the artificial wetland reaction zone is filled with a mixture of limestone, zeolite and modified expanded clay matrix, wherein the matrix filling height is 0.6m, the pore sizes of the limestone, zeolite and modified expanded clay matrix are all 1μm-100μm, and 6 mixed matrix volume ratios are set, namely limestone: zeolite: modified expanded clay (1:2:1, 1:1:2, 2:1:1, 1:3:1, 1:1:3, 3:1:1), and filling is carried out after complete mixing.

[0065] The reactor was designed to have a total volume of 0.441 m 3 The total volume of the matrix layer is 0.287m 3 The removal effect of the combined matrix on ammonia nitrogen, total nitrogen, total phosphorus and COD in sewage was studied when the HRT (hydraulic retention time) was 2 days. The pollutant removal rate was calculated by the changes in the initial and final ammonia nitrogen, total nitrogen, total phosphorus and COD contents of the test, and the DO, ORP, PH and other indicators were measured at the same time.

[0066] The results show that the above mixed matrix has little effect on the removal of ammonia nitrogen and total phosphorus at different ratios. The two indicators in the effluent basically meet the standards of surface Class III water, and the removal rate can reach more than 85%. The combination with a high volume ratio of zeolite has better ammonia nitrogen removal effect, and the combination with a high volume ratio of limestone and modified ceramsite has better total phosphorus and organic matter removal effect. For tetracycline, limestone: zeolite: modified ceramsite (volume ratio of 1:2:1) can achieve an 80% removal effect, which is much higher than the mixed matrix under the other five volume ratios. Therefore, the volume ratio of limestone: zeolite: modified ceramsite is determined to be 1:2:1 as the mixed matrix filling ratio of artificial wetland device.

[0067] It was found that the mixed matrix of limestone: zeolite: modified expanded clay in a volume ratio of 1:2:1 had a removal effect on ammonia nitrogen that was 1.5 times that of a volume ratio of 1:1:1, a total phosphorus removal effect that was 1.4 times that of the organic matter removal effect that was 2 times that of the tetracycline removal effect that was 1.63 times that of the mixed matrix of limestone: zeolite: modified expanded clay in a volume ratio of 1:2:1.

[0068] Example 2

[0069] An artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal is the same as Example 1, except that the volume ratio of limestone: zeolite: modified ceramsite is set to 1:2:1, and the matrix is ​​set to a filling mode from left to right, with a total of 6 different filling sequences (from front to back along the water flow direction: modified ceramsite, zeolite, limestone; modified ceramsite, limestone, zeolite; zeolite, modified ceramsite, limestone; zeolite, limestone, modified ceramsite; limestone, modified ceramsite, zeolite; limestone, zeolite, modified ceramsite), sampling is taken when passing through two matrices and after three matrices to determine the optimal filling sequence of the mixed matrix.

[0070] The results show that, under different filling orders, the better the removal effect of the matrix type that passes through zeolite first, the better the removal effect of ammonia nitrogen, the removal rate can reach more than 90%, and the effluent basically meets the requirements of surface water type II. The adsorption of ammonia nitrogen by FTS (where F is zeolite, T is modified ceramsite, and S is limestone, that is, zeolite, modified ceramsite, and limestone from front to back along the water flow direction) remains unchanged or slightly decreases when passing through three matrices compared with passing through two matrices. Although zeolite has better removal effect on ammonia nitrogen than other matrices, it is unstable in combination with ammonium ions and is easily affected by the surrounding environment. The matrix combination that passes through modified ceramsite and limestone first has a better total phosphorus removal effect, and the removal rate of phosphorus pollutants is more than 85%. The matrix combination that passes through limestone first has a better organic matter removal effect, and the removal rate is 4 times that of the matrix combination that passes through zeolite first. For tetracycline, limestone-zeolite-modified ceramsite can achieve a removal effect of 78%, which is much higher than the mixed matrix under the other five filling orders. Therefore, the filling order of the mixed matrix in the artificial wetland sewage treatment system is determined to be limestone, zeolite and modified ceramsite.

[0071] When the volume ratio of limestone: zeolite: modified expanded clay is 1:2:1, it is found that the removal effect of ammonia nitrogen by the mixed matrix in the segmented filling mode is 1.5 times that in the complete mixing mode (Example 1), the total phosphorus removal effect is 1.17 times, the organic matter removal effect is 1.14 times, and the tetracycline removal effect is 1.3 times.

[0072] Example 3

[0073] An artificial wetland sewage treatment system for strengthening wetland matrix denitrification and phosphorus removal comprises a front water distribution area, an artificial wetland reaction area and a rear water collection area, the water inlet end of the artificial wetland reaction area is connected with the front water distribution area, the water outlet end of the artificial wetland reaction area is connected with the rear water collection area, a water inlet baffle is arranged between the water inlet end of the artificial wetland reaction area and the front water distribution area, a water collection baffle is arranged between the water outlet end of the artificial wetland reaction area and the rear water collection area, the water inlet baffle and the water collection baffle are both transparent acrylic plates, so that the matrix will not be dispersed by water and water can pass through, sewage enters the artificial wetland reaction area through the front water distribution area, and the outlet water overflows out of the sewage treatment system through the rear water collection area, the dimensions of the front water distribution area and the rear water collection area are length×width×depth=0.15m×0.35m×0.9m, and the dimensions of the artificial wetland reaction area are length×width×depth=1.4m×0.35m×0.9m;

[0074] Among them, the artificial wetland reaction zone is mixed and filled with limestone, zeolite and modified ceramsite matrix, wherein the matrix filling height is 0.6m, the pore sizes of limestone, zeolite and modified ceramsite matrix are all 1μm-100μm, and the volume ratio of limestone: zeolite: modified ceramsite is set to 1:2:1, and the matrix filling order from front to back along the water flow direction is limestone, zeolite and modified ceramsite.

[0075] The above-mentioned artificial wetland sewage treatment system with enhanced wetland matrix denitrification and phosphorus removal is used for sewage treatment. The sewage treatment process is a long-term continuous operation and involves the removal of pollutants by plants and microorganisms. It is divided into two stages:

[0076] (1) Start the reactor by natural biofilm formation. Use valve control and the height difference between the water storage tank and the pilot plant to continuously feed water. Try to keep the water inflow uniform. Before starting, set the flow rate to 14 mL / min. After the reactor is full and stable, take samples (take samples every two days) and detect the COD and ammonia nitrogen concentrations of the effluent. When the removal rates of COD and ammonia nitrogen in the effluent are basically stable and obvious biofilm can be observed on the surface of the filler with the naked eye, the startup is considered successful.

[0077] (2) After entering the stable operation stage, young plants with good growth were planted to explore the removal effect of conventional and new pollutants by the artificial wetland sewage treatment system under high temperatures in summer. Water samples were collected and tested on the same day.

[0078] The results show that during the operation of the reactor in steps (1) and (2), the concentrations of ammonia nitrogen, total phosphorus, organic matter and tetracycline in the effluent gradually decreased, and the removal rates were 77%, 87%, 56% and 66%, respectively. After long-term operation, the matrix filler was not replaced or cleaned, and the adsorption of pollutants by the matrix gradually became saturated at about 155 days, but no obvious clogging occurred. It can be seen that the proportion of mixed matrix added and the matrix filling sequence adopted in the present invention can effectively delay the decline of adsorption saturation and reduce the frequency of replacing the matrix. In the subsequent operation, the concentrations of ammonia nitrogen, total phosphorus and tetracycline in the effluent of the reactor were almost undetectable, and the decontamination effect was twice that of the sewage treatment plant process. The community structure of microorganisms was analyzed. Proteobacteria belonged to the largest phylum in the bacterial domain (43.58%), and its members were all Gram-negative bacteria, including many nitrogen-fixing bacteria, which can play an important role in the removal of nitrogen-containing pollutants in wetlands. γ-Proteobacteria can improve the denitrification capacity of wetlands and are the dominant proteobacteria. Analyzing the differences in the relative abundance of microorganisms at the genus level, it was found that Nitrospira (Nitrospira), Hydrogenophaga (Hydrogenophaga) and Candidatus_Nitrotoga (nitrite oxidizing bacteria) can play a nitrification role in the sample, accounting for 41%. Among them, Hydrogenophaga and Candidatus_Nitrotoga are β-proteobacteria (Betaproteobacteria), which can oxidize nitrite accounting for 39%. Denitratisoma (estradiol nitrifying meat bacteria), Thiobacillus (sulfur oxidizing bacteria) and Ferritrophicum (iron-eating bacteria) play a denitrification role, accounting for 30%. It shows that the coupling effect of the mixed matrix filling order and different volume ratios used in the present invention effectively promotes the removal of pollutants by changing the structure and abundance of different functional bacterial communities.

[0079] Comparative Example 1

[0080] The same as Example 3, except that limestone, zeolite and modified ceramsite are mixed in a volume ratio of 1:2:1 as a mixed matrix in the artificial wetland sewage treatment system for enhancing nitrogen and phosphorus removal in the wetland matrix.

[0081] The results showed that the concentrations of ammonia nitrogen, total phosphorus, organic matter and tetracycline in the effluent gradually decreased, with removal rates of 50%, 52%, 35% and 45% respectively. After long-term operation, the matrix filler was not replaced or cleaned, and the adsorption of pollutants by the matrix gradually became saturated, and no obvious blockage occurred. The community structure of microorganisms was analyzed. Proteobacteria is still the largest phylum in the bacterial domain (40.19%). γ-Proteobacteria can improve the denitrification capacity of wetlands and is the dominant proteobacteria. Analysis of the differences in the relative abundance of microorganisms at the genus level found that Nitrospira (Nitrospira), Hydrogenophaga (Hydrogenophaga) and Candidatus_Nitrotoga (nitrite oxidizing bacteria) can play a nitrification role in the samples, accounting for 35%. Denitratisoma (estradiol-eating nitrifying meat bacteria), Thiobacillus (sulfur oxidizing bacteria) and Ferritrophicum (iron-loving bacteria) play a denitrification role, accounting for 25%.

[0082] Compared with the results of Example 3, it was found that the removal rate of ammonia nitrogen in the long-term operation of the mixed matrix in the segmented filling mode was 1.54 times that in the complete mixing mode, the total phosphorus removal rate was 1.67 times, the organic matter removal rate was 1.6 times, and the tetracycline removal rate was 1.46 times. In comparison, the technical solution of Example 3 using segmented filling of limestone, zeolite and modified ceramsite (volume ratio of 1:2:1) is significantly better than the pollution removal efficiency of Comparative Example 1 in the complete mixing mode.

[0083] Comparative Example 2

[0084] Same as Example 3, except that the mixed matrix is ​​replaced by limestone in equal volume.

[0085] The results show that compared with Example 3, after the mixed matrix is ​​replaced with limestone in equal volume, the removal rate of ammonia nitrogen is only 36% after long-term operation, the removal rate of total phosphorus is 94%, the removal rate of organic matter is 57%, and the removal rate of tetracycline is 55%. In contrast, the removal efficiency of ammonia nitrogen in the technical scheme of Example 3 is significantly better than the removal efficiency of Comparative Example 2 (about 2.1 times); the removal efficiency of total phosphorus in Comparative Example 2 is significantly better than the removal efficiency of Example 3 (about 1.08 times); and the removal effect of organic matter and tetracycline is not much different. After long-term operation, the matrix filler is not replaced and cleaned, and the adsorption of pollutants by the matrix gradually becomes saturated at about 77d. The community structure of microorganisms is analyzed, and a series of microorganisms that play a nitrifying role account for a low proportion, especially Nitrospira (Nitrospira), which accounts for only 9%. Comprehensive analysis shows that the technical scheme of Example 3, which uses segmented filling of limestone, zeolite and modified ceramsite (volume ratio of 1:2:1), is significantly better than the removal efficiency of Comparative Example 2 in which the mixed matrix is ​​replaced with limestone in equal volume.

[0086] Comparative Example 3

[0087] Same as Example 3, except that the mixed matrix is ​​replaced by zeolite in equal volume.

[0088] The results show that compared with Example 3, after the mixed matrix was replaced with zeolite in equal volume, the removal rate of ammonia nitrogen was 98%, the removal rate of total phosphorus was 20%, the removal rate of organic matter was 44%, and the removal rate of tetracycline was 50% after long-term operation. In contrast, the removal efficiency of ammonia nitrogen by the technical scheme of comparative example 3 is significantly better than the removal efficiency of Example 3 (about 1.3 times), and the effluent ammonia nitrogen index can stably maintain the standard of surface Class I water; but the removal efficiency of total phosphorus by the technical scheme of Example 3 is significantly better than the removal efficiency of comparative example 1 (about 4.1 times); and the removal effect of organic matter and tetracycline is not much different. After long-term operation, the matrix filler was not replaced or cleaned, and the adsorption of pollutants by the matrix gradually became saturated at about 80 days. The community structure of microorganisms was analyzed, and a series of microorganisms that play a nitrifying role accounted for a high proportion, especially Nitrospira (Nitrospira) and Hydrogenophaga (Hydrogenophaga), accounting for 91%. Comprehensive analysis shows that the technical solution of Example 3 using segmented filling of limestone, zeolite and modified ceramsite (volume ratio of 1:2:1) is significantly better than the decontamination efficiency of Comparative Example 3 in which the mixed matrix is ​​replaced with limestone in equal volume. For water samples with seriously excessive ammonia nitrogen, the technical solution of Comparative Example 3 is more suitable.

[0089] Comparative Example 4

[0090] Same as Example 3, except that an equal volume of the mixed matrix is ​​replaced by modified ceramsite.

[0091] The results show that compared with Example 3, after the mixed matrix is ​​replaced with modified ceramsite in equal volume, the removal rate of ammonia nitrogen is 75%, the removal rate of total phosphorus is 87%, the removal rate of organic matter is 47%, and the removal rate of tetracycline is 55% after long-term operation. In contrast, the removal efficiency of ammonia nitrogen, organic matter and tetracycline in the technical scheme of Example 3 is significantly better than the removal efficiency of Comparative Example 4 (about 1.02, 1.19 and 1.2 times respectively); while the removal effect of ammonia nitrogen and total phosphorus is not much different. After long-term operation, the matrix filler is not replaced and cleaned, and the adsorption of pollutants by the matrix gradually becomes saturated at about 94d. The community structure of microorganisms is analyzed, and the abundance of microorganisms is high. A series of microorganisms that play a nitrifying role account for the majority, especially Nitrospira (Nitrospira), accounting for 87%. Comprehensive analysis shows that the technical scheme of Example 3 using segmented filling of limestone, zeolite and modified ceramsite (volume ratio of 1:2:1) is significantly better than the removal efficiency of Comparative Example 4 in which the mixed matrix is ​​replaced with limestone in equal volume.

[0092] Example 4

[0093] The same as Example 3, except that the volume ratio of limestone:zeolite:modified ceramsite is set to 1:1:1.

[0094] The results showed that during the operation of the reactor, the concentrations of ammonia nitrogen, total phosphorus, organic matter and tetracycline in the effluent gradually decreased, and the removal rates were 70%, 77%, 59% and 67%, respectively. After long-term operation, the matrix filler was not replaced or cleaned. The adsorption of pollutants by the matrix gradually became saturated around 127 days, but no obvious blockage occurred. The difference in the relative abundance of microorganisms at the genus level was analyzed and it was found that Nitrospira (Nitrospira), Hydrogenophaga (Hydrogenophaga) and Candidatus_Nitrotoga (nitrite oxidizing bacteria) in the samples could play a nitrification role, accounting for 31%. Denitratisoma (estradiol nitrifying bacteria), Thiobacillus (sulfur oxidizing bacteria) and Ferritrophicum (iron-loving bacteria) played a denitrification role, accounting for 28%. It shows that the coupling effect of the mixed matrix volume ratio of 1:1:1 used in Example 4 can effectively promote the removal of various pollutants by adjusting the structure and abundance of different functional bacterial communities. However, it is not possible to carry out targeted removal of characteristic pollutants in the water body after one of the nitrogen and phosphorus indicators in the water body exceeds the standard.

[0095] Example 5

[0096] The same as Example 3, except that the volume ratio of limestone:zeolite:modified ceramsite is set to 2:1:1.

[0097] The results showed that during the operation of the reactor, the concentrations of ammonia nitrogen, total phosphorus, organic matter and tetracycline in the effluent gradually decreased, and the removal rates were 65%, 90%, 60% and 66%, respectively. After long-term operation, the matrix filler was not replaced or cleaned, and the adsorption of pollutants by the matrix gradually became saturated around 135 days, but no obvious blockage occurred. Analysis of the differences in the relative abundance of microorganisms at the genus level found that the proportion of microorganisms that can play a nitrifying role in the samples was 29%. Among them, β-proteobacteria (Betaproteobacteria) such as Hydrogenophaga (hydrogen cytophaga) and Candidatus_Nitrotoga (nitrite oxidizing bacteria) were the main ones. Denitratisoma (estradiol-eating nitrifying meat bacteria), Thiobacillus (sulfur oxidizing bacteria) and Ferritrophicum (iron-eating bacteria) played a denitrifying role, accounting for 25%. It shows that the coupling effect of the mixed matrix volume ratio of 2:1:1 used in Example 5 can effectively promote the removal of various pollutants, especially high-phosphorus wastewater, by adjusting the structure and abundance of different functional bacterial communities.

[0098] It can be seen from Examples 3-5 that in the process of improving the tail water quality of the sewage treatment plant in the artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal of the present invention, when the mass ratio of nitrogen and phosphorus in the influent is 60 or above, the volume ratio of limestone: zeolite: modified ceramsite is set to 1:2:1; when the mass ratio of nitrogen and phosphorus in the influent is between 40-60 (excluding 40 and 60), the volume ratio of limestone: zeolite: modified ceramsite is set to 1:1:1; when the mass ratio of nitrogen and phosphorus in the influent is 40 or below, the volume ratio of limestone: zeolite: modified ceramsite is set to 2:1:1.

[0099] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An artificial wetland sewage treatment system for strengthening nitrogen and phosphorus removal in wetland matrix, characterized in that: The invention comprises an artificial wetland reaction zone, wherein the artificial wetland reaction zone is a left-right segmented structure, and limestone, zeolite and modified ceramsite are filled as a matrix from front to back along the water flow direction according to a filling mode of x:y:z in volume ratio, wherein (x+y):z=3:1; When the mass ratio of nitrogen and phosphorus in the influent is ≥60, x:y=1:2; when the mass ratio of nitrogen and phosphorus in the influent is >40 and <60, x:y=1:1; when the mass ratio of nitrogen and phosphorus in the influent is ≤40, x:y=2:

1.

2. The artificial wetland sewage treatment system for enhancing wetland matrix nitrogen and phosphorus removal according to claim 1 is characterized in that: The pore sizes of the limestone, zeolite and modified ceramsite are all 1 μm-100 μm.

3. The artificial wetland sewage treatment system for enhancing wetland matrix nitrogen and phosphorus removal according to claim 1 is characterized in that: The ratio of the filling volume of the matrix to the working volume of the reactor in the artificial wetland reaction zone is (60-70):

100.

4. The artificial wetland sewage treatment system for enhancing wetland matrix nitrogen and phosphorus removal according to claim 2 is characterized in that: The modified ceramsite is prepared by soaking the biological ceramsite in NaOH solution and AlCl3 solution in sequence.

5. The artificial wetland sewage treatment system for enhancing wetland matrix nitrogen and phosphorus removal according to claim 1 is characterized in that: It also includes a front water distribution area and a rear water collection area. Sewage enters the treatment system through the front water distribution area. The water inlet end of the artificial wetland reaction area is connected to the front water distribution area, and the water outlet end of the artificial wetland reaction area is connected to the rear water collection area.

6. The artificial wetland sewage treatment system for enhancing wetland matrix nitrogen and phosphorus removal according to claim 5 is characterized in that: A water inlet baffle is arranged between the water inlet end of the artificial wetland reaction zone and the front water distribution area, and a water collection baffle is arranged between the water outlet end of the artificial wetland reaction zone and the rear water collection area.

7. The artificial wetland sewage treatment system for enhancing wetland matrix nitrogen and phosphorus removal according to claim 5 is characterized in that: The artificial wetland sewage treatment system is also provided with an overflow device.

8. Use of the artificial wetland sewage treatment system for enhanced wetland matrix nitrogen and phosphorus removal as described in any one of claims 1 to 7 in improving the quality of tail water from a sewage treatment plant.

9. The use according to claim 8, characterized in that: The artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal is first introduced with sewage to promote microbial growth, and after successful biofilm formation, soil is covered and plants are planted, and the artificial wetland sewage treatment system for enhanced wetland matrix denitrification and phosphorus removal is continuously operated.

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