Artificial wetland iron-carbon-manganese composite filler capable of efficiently removing nitrogen and phosphorus

Abstract

The invention relates to the technical field of constructed wetlands, in particular to a constructed wetland iron-carbon-manganese composite filler capable of efficiently removing nitrogen and phosphorus. According to the filler, the manganese ore layer is arranged behind the iron-carbon micro-electrolysis layer, the microenvironment in the iron-carbon micro-electrolysis constructed wetland is adjusted through manganese ore, iron and manganese exist at the same time and can serve as electron donors for microbial denitrification, the effect is better than that of single use of iron, meanwhile, the oxidation capacity of high-valence manganese ions is utilized, and the denitrification efficiency is improved. The ammonia nitrogen in the iron oxide carbon wetland is inhibited or re-oxidized, so that the total nitrogen removal capability of the wetland is enhanced, and efficient nitrogen removal is realized; the manganese ore is large in specific surface area and can adsorb iron ions in water, iron and manganese separated out of the water are effectively removed, and the problem that the dissolution concentration of the iron ions is high is solved; phosphate radicals are adsorbed and removed mainly through ligand exchange with hydroxyl on the surface of manganese nodule, iron ions and ferrous ions dissolved out from the scrap iron are combined with influent phosphate to form precipitates such as iron phosphate, and a very good effect on removal of total phosphorus is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of artificial wetlands, and in particular to an iron-carbon-manganese composite filler for artificial wetlands for efficient nitrogen and phosphorus removal. Background Art

[0002] The denitrification performance of artificial wetlands is closely related to the C / N ratio of sewage. When the C / N ratio drops below 3, the denitrification effect decreases significantly. This is because heterotrophic denitrifying bacteria cannot obtain sufficient carbon sources and electron donors to complete denitrification. Therefore, strengthening the autotrophic denitrifying bacteria in the wetland becomes a very promising solution.

[0003] At present, the enrichment of autotrophic denitrifying bacteria is promoted by filling the wetland with functional fillers such as zero-valent iron and elemental sulfur, which significantly helps the denitrification performance of artificial wetlands. By strengthening the autotrophic denitrifying bacteria, the denitrification performance of artificial wetlands can be improved to more than 80%. However, the use of fillers such as iron and sulfur at this stage will cause the concentration of iron ions and sulfate ions in the effluent to increase, which will have an adverse effect on the receiving water body. At the same time, artificial wetlands based mainly on autotrophic denitrification have a good removal ability for nitrate nitrogen during operation, but the ammonia nitrogen contained in the effluent is relatively high, becoming the main component of the total nitrogen in the effluent.

[0004] Therefore, an artificial wetland filler that can solve the high concentration of iron ion dissolution in the effluent and effectively remove ammonia nitrogen in the effluent, thereby enhancing the total nitrogen removal rate in the effluent, is a problem that needs to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide an artificial wetland iron carbon manganese composite filler for efficient nitrogen and phosphorus removal, so as to solve the problem of high iron ion dissolution concentration and high ammonia nitrogen concentration in effluent caused by iron and other fillers at present.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: an artificial wetland iron-carbon-manganese composite filler for efficient nitrogen and phosphorus removal, which only includes a gravel layer, an iron-carbon layer and a manganese ore layer; the gravel layer is only located below the iron-carbon layer in the direction of water flow, and the manganese ore layer is located above the iron-carbon layer in the direction of water flow.

[0007] Furthermore, the particle size of the gravel in the gravel layer is 1 to 3 cm.

[0008] Furthermore, the iron-carbon layer is a compound of iron filings and activated carbon.

[0009] Furthermore, the particle size of the manganese ore in the manganese ore layer is 4 to 8 mm.

[0010] Furthermore, the volume ratio of iron filings to activated carbon in the iron-carbon layer is 1:1; the iron filings are 2 to 3 cm long and 0.4 to 0.6 cm wide; the activated carbon is cylindrical, with a bottom diameter of 0.4 to 0.6 cm and a height of 1 to 3 cm.

[0011] Furthermore, the iron filings need to be soaked in 10% sodium hydroxide solution to remove grease before use, and then dilute sulfuric acid is used to remove rust on the surface of the iron filings.

[0012] Furthermore, the gravel, activated carbon and manganese ore need to be washed and dried before use.

[0013] Furthermore, the artificial wetland filler can remove 94.76% of the total nitrogen in sewage and 95.9% of ammonia nitrogen; the proportion of ammonia nitrogen in the total nitrogen in the effluent is only 26.08%.

[0014] Furthermore, when the artificial wetland filler is used, the total phosphorus concentration of the effluent is 0.02-0.1 mg / L, and the total phosphorus removal efficiency is stabilized at 90%.

[0015] Furthermore, when the artificial wetland filler is in use, the iron ion content in the effluent is stabilized below 1 mg / L, and the manganese ion content is stabilized below 10 μg / L.

[0016] Beneficial effects of the present invention:

[0017] 1. Improve the removal efficiency of ammonia nitrogen and total nitrogen; the removal rate of ammonia nitrogen can reach 95.9%, the removal rate of total nitrogen can reach 94.76%, and the proportion of ammonia nitrogen in total nitrogen is only 26.08%; this is mainly due to the role of manganese ore in regulating the internal microenvironment of the wetland and optimizing the structure of the microbial community, which provides favorable conditions for the transformation of ammonia nitrogen. Under the action of manganese ore, the total nitrogen removal rate of the CW-Fe artificial wetland has increased by 61.08%;

[0018] 2. Solve the problem of iron ion dissolution; During the experiment, the total iron ion concentration in the effluent of the artificial wetland with manganese ore added was maintained below 1 mg / L. This result shows the effectiveness of manganese ore in adsorbing iron ions and preventing their excessive dissolution, which helps to solve the problem of high iron ion dissolution concentration in the early stage of iron-carbon wetland operation;

[0019] 3. Through SEM image analysis of the manganese ore surface, it was found that a large amount of Fe2O3 was attached to its surface, and the iron adsorption capacity of the manganese ore surface increased from 0.012 mg / g to 0.88 mg / g; compared with CW-Fe, the total iron concentration of the effluent from CW-Mn decreased by 96% in the initial operation, and the total manganese concentration of the effluent was maintained below 10 μg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a schematic diagram of the structure of an artificial wetland and a packing layer in Example 1 of the present invention;

[0021] Figure 2 It is a graph showing the change of nitrogen concentration in various forms in the effluent of the two wetlands CW-Fe and CW-Mn in the first and second stages of water inflow of the present invention;

[0022] Figure 3 This is a diagram showing the removal effect of the composite filler of the present invention on total phosphorus at different hydraulic retention times;

[0023] Figure 4 The graphs of ammonia nitrogen concentration changes in water samples along the CW-Fe and CW-Mn wetlands at different stages; (a)-(d) are ammonia nitrogen concentrations along the wetlands at different stages, (a)(b) are CW-Fe wetlands; (c)(d) are CW-Mn wetlands; (e)-(h) are changes in pollutant concentrations in typical effluents at different stages, (e)(g) are effluents from CW-Fe wetlands; (f)(h) are effluents from CW-Mn wetlands;

[0024] Figure 5 The XRD, surface iron XPS and surface manganese XPS analysis diagrams of the manganese ore before and after use of the present invention; wherein, the XRD analysis of the manganese ore before (a) and after (b); the surface iron XPS analysis of the manganese ore before (c) and after (e); the surface manganese XPS analysis of the manganese ore before (d) and after (f);

[0025] Figure 6 The SEM images of the manganese ore of the present invention before and after use, wherein the SEM images of the manganese ore before use (a)-(c), and after use (d)-(f); (g) the change of total iron concentration in wetland effluent; (h) the total manganese ion concentration in CW-Mn effluent; (i) the surface adsorption capacity of iron before and after use of manganese ore;

[0026] Figure 7 It is an analysis diagram of microbial diversity at different positions of the artificial wetland involved in the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0028] Example 1

[0029] like Figure 1 As shown, an artificial wetland environment is simulated in the laboratory. The shell of the artificial wetland is made of plexiglass with a diameter of 20 cm, a height of 80 cm, and an effective water depth of 70 cm. The upper water inlet and underwater water outlet are adopted.

[0030] The filler (CW-Mn) of the present invention is filled in an artificial wetland, which is a gravel layer, an iron-carbon layer and a manganese ore layer from top to bottom; the gravel layer is 40 cm thick and has a particle size of 1 to 3 cm, serving as a supporting layer at the bottom of the wetland; the iron-carbon layer is 20 cm thick, the length of iron filings is 2 to 3 cm, and the width is about 0.5 cm; the activated carbon is cylindrical, with a bottom diameter of about 0.5 cm and a length of about 2 cm; the iron-carbon materials are mixed in a volume ratio of 1:1 to form an iron-carbon layer; a 5 cm thick manganese ore layer is filled below the iron-carbon layer; the iron-carbon layer and the manganese ore layer form an iron-carbon-manganese composite filler layer; valves are installed every 10 cm on the side of the artificial wetland to study the changes in pollutant concentration along the way.

[0031] In this embodiment, the gravel is washed and dried before use. The porous structure on the surface of the gravel layer is suitable for the survival of microorganisms. The dissolved oxygen content on the surface and inside of the filler gradually decreases, providing a suitable ecological niche for nitrifying and denitrifying microorganisms at the same time, and realizing the simultaneous nitrification and denitrification process inside the filler; before using iron filings, they must first be soaked in 10% sodium hydroxide solution to remove grease, and then dilute sulfuric acid is used to remove rust on the surface of the iron filings; before using activated carbon, rinse the surface stains with tap water and dry it for use; before using manganese ore, rinse the surface stains with tap water.

[0032] An experiment was conducted on the filler of this embodiment, and two groups of controls, zeolite wetland and iron-carbon wetland (CW-Fe), were set up; the outer shells of the artificial wetlands of zeolite wetland and iron-carbon wetland were consistent with those of this embodiment; in the zeolite wetland, a 10 cm thick gravel was placed at the bottom as a supporting layer with a particle size of 1 to 3 cm, and a 60 cm thick zeolite was laid under the gravel layer with a particle size of 1 to 3 cm; in the iron-carbon wetland, a 10 cm thick gravel was placed at the bottom as a supporting layer with a particle size of 1 to 3 cm, and a 20 cm thick iron-carbon layer was laid under the gravel layer with a volume ratio of iron to carbon of 1:1, and a 40 cm thick zeolite was laid on the bottom layer with a particle size of 1 to 3 cm.

[0033] The sludge required for the start-up of the artificial wetland was taken from the secondary sedimentation tank area of ​​a sewage treatment plant in Zhengzhou City. The sludge concentration was about 10,000 mg / L. After the sludge was retrieved, it was aerated for one day to activate the sludge, and then the concentrated sludge was diluted to 400 mg / L with prepared water (C:N:P=100:20:1). The diluted sludge was added to three artificial wetlands, and the culture sewage was introduced at the same time. The culture was continued for one month, the hydraulic retention time was 2 days, and then the experiment was started.

[0034] The experimental water inlet was divided into two stages. The first stage, Stage I, had nitrate nitrogen 15 mg / L, total phosphorus 0.5 mg / L, and COD 7.5 mg / L. The second stage, Stage II, had ammonia nitrogen 5 mg / L, nitrate nitrogen 10 mg / L, and total phosphorus and COD remained unchanged.

[0035] The experimental results are as follows Figure 2-6 shown.

[0036] Figure 2 The changes in the concentrations of various forms of nitrogen in the effluent of the two wetlands CW-Fe and CW-Mn in the first and second stages of water inflow. Among them, for ammonia nitrogen, in the second stage, the average effluent concentration of the CW-Fe wetland was 1.04 mg / L, and the average effluent concentration of the CW-Mn wetland was 0.205 mg / L, and the ammonia nitrogen removal rate of the CW-Mn wetland could reach 95.9%. After adding manganese ore, the ammonia nitrogen concentration in the effluent of the CW-Mn wetland was significantly reduced; for the CW-Fe wetland, the increase in the ammonia nitrogen concentration in the influent led to an increase in the ammonia nitrogen concentration in the effluent, but the ammonia nitrogen concentration in the CW-Mn effluent remained stable, indicating that the addition of manganese ore (manganese oxide) has a good treatment effect on ammonia nitrogen loads at high concentrations.

[0037] from Figure 2 It can also be found that the nitrate nitrogen concentration in the effluent of CW-Mn is lower than that of CW-Fe; although the introduction of manganese ore shows that it has an impact on certain steps of denitrification from the perspective of nitrite nitrogen reduction, the valence state conversion process of manganese ions can provide certain electrons for denitrification, that is, it can be considered that the presence of iron and manganese is equivalent to multiple electron donors, so this may be the reason why CW-Mn has a lower nitrate nitrogen concentration.

[0038] Ammonia nitrogen in the wetland will be oxidized by tetravalent manganese, resulting in an increase in the concentration of divalent manganese, so the two electron donors, iron and manganese, ensure that the nitrate nitrogen concentration in the CW-Mn effluent is reduced; in the second stage, the total nitrogen concentrations in the effluents of both CW-Fe and CW-Mn wetlands decreased, with the average total nitrogen concentration in the effluent of CW-Fe wetland being 2.02 mg / L, and the average total nitrogen concentration in the effluent of CW-Mn wetland being 0.786 mg / L; ammonia nitrogen accounted for 51.48% of the total nitrogen in the effluent of CW-Fe wetland, while that in CW-Mn wetland was only 26.08%. The low total nitrogen concentration in the effluent of CW-Mn wetland was contributed by the decrease of ammonia nitrogen and nitrate nitrogen. The addition of manganese ore can increase the denitrification capacity of CW-Fe wetland by 61.08%, and the total nitrogen removal rate of CW-Mn wetland reached 94.76%, and the problem of high ammonia nitrogen concentration in the effluent was solved.

[0039] Figure 3The present invention shows the removal effect of the composite filler on total phosphorus at different hydraulic retention times. The total phosphorus concentration of the effluent from the zeolite wetland and CW-Fe wetland at different hydraulic retention times does not change much, fluctuating between 0.2 and 0.3 mg / L. In the early stage of the experiment, the wetland filler can partially adsorb the total phosphorus in the influent, but the shortening of the hydraulic retention time is not conducive to the adsorption process. Therefore, the total phosphorus concentration of the effluent from the zeolite wetland and CW-Fe wetland increased after the HRT was shortened. The total phosphorus concentration of the effluent from the CW-Mn wetland fluctuated between 0.02 and 0.1 mg / L, and the removal efficiency was stable at 90%. It was found that phosphate was mainly adsorbed and removed by ligand exchange with the hydroxyl groups on the surface of manganese nodules. The iron ions and ferrous ions dissolved from the iron filings combined with the phosphate in the influent to form precipitations such as iron phosphate, which had a very good effect on the removal of total phosphorus.

[0040] Figure 4 The following is a graph showing the changes in ammonia nitrogen concentration in water samples along the CW-Fe and CW-Mn wetlands at different stages. The changes in ammonia nitrogen concentration along the CW-Mn wetland were similar in the two stages. The ammonia nitrogen concentration dropped to a low point of less than 0.35 mg / L at a depth of 0 to 40 cm, and the CW-Fe wetland also had a similar performance. However, in the iron-carbon layer at a depth of 40 to 60 cm, the ammonia nitrogen concentrations of the two wetlands differed. In the middle layer of the iron-carbon layer at a depth of 50 cm, the average ammonia nitrogen concentrations of the CW-Fe wetland in the two stages were 2.22 mg / L and 1.73 mg / L, respectively, and the average concentrations of the CW-Mn wetland were 0.515 mg / L and 0.428 mg / L, respectively. At the same location, the ammonia nitrogen concentration in the CW-Mn wetland decreased by 76.8% and 75.3%. Since the ammonia nitrogen concentration in the water was low before entering the iron-carbon layer, the iron-carbon layer increased the ammonia nitrogen concentration. Then, adding manganese ore could inhibit the generation of ammonia nitrogen in the iron-carbon layer, and the inhibition effect was above 75%. At the same time, the DO, ORP and pH along the way were measured (see Table 1). Compared with the CW-Fe wetland, the CW-Mn wetland had higher DO and ORP.

[0041] Table 1 Physical and chemical indicators of wetland effluent at different stages

[0042]

[0043]

[0044] Figure 5 XRD, surface iron XPS and surface manganese XPS analysis diagrams of manganese ore before and after use; Figure 5 It can be seen that a large amount of iron ions are adsorbed on the surface of manganese ore, Fe 3+The concentration increased by nearly 88 times; the iron ions dissolved from the iron-carbon layer were intercepted, adsorbed and oxidized by the manganese ore, thereby reducing the consumption of oxygen and increasing the DO concentration; the strong oxidizing property of manganese ore also increased the ORP, thereby inhibiting the over-reduction of nitrate nitrogen.

[0045] The experimental results of each stage are shown in Figure 4 In stage I, ammonia nitrogen was present in the effluents of both wetlands, which was reduced from nitrate nitrogen. The peak ammonia nitrogen concentration in the effluent of CW-Fe wetland was 2.08 mg / L and remained stable; however, in CW-Mn wetland, the effluent ammonia nitrogen concentration was always below 0.3 mg / L, with a peak of 0.283 mg / L, indicating that the addition of manganese ore had a significant inhibitory effect on the over-reduction of nitrate nitrogen to ammonia nitrogen.

[0046] The rate of decrease of nitrate nitrogen concentration in the effluent of CW-Mn wetland was slower than that of CW-Fe wetland, which may be because its internal reducibility was weaker than that of CW-Fe wetland. This destroyed high reducibility may be the main reason for inhibiting the formation of ammonia nitrogen. Ammonia nitrogen was added to the influent in Stage II, and the ammonia nitrogen concentration in the effluent of CW-Fe wetland increased significantly. After 24 hours, the effluent concentration was 1.64 mg / L, while the ammonia nitrogen concentration in the effluent of CW-Mn wetland dropped to 0.196 mg / L in the 4th hour. In both stages, the ammonia nitrogen concentration in the effluent of CW-Mn wetland remained at a low concentration for most of the period, indicating that manganese ore is more likely to achieve low ammonia nitrogen concentration in the effluent by inhibiting the formation of ammonia nitrogen.

[0047] The change of nitrite nitrogen concentration in the effluent of CW-Mn wetland was similar to that of stage I, with a peak of 2.505 mg / L at the 8th hour. The nitrate nitrogen concentration continued to decline throughout the cycle, while the CW-Fe wetland reached a stable value of about 0.65 mg / L at the 12th hour. By performing first-order kinetic fitting on the changes in nitrate nitrogen concentration in the effluent of the two stages, it was found that the kinetic constants of the CW-Mn wetland were smaller than those of the CW-Fe wetland, but the nitrate nitrogen concentration in the effluent of the CW-Mn wetland could reach a low concentration at the end of the cycle, indicating that although the nitrate nitrogen reduction rate of the CW-Mn wetland decreased, the nitrate nitrogen concentration in the effluent could still be maintained at a low concentration.

[0048] Figure 6 The SEM images of manganese ore before and after use are shown. Before use, the surface of manganese ore was mainly blocky and layered. After use, the surface morphology of manganese ore was mainly flake-like, with a flower-like shape, as shown in Table 2. Through XDR analysis, it was detected that it was mainly iron oxide, and some manganese oxides. BioMnO x ) has stronger oxidizing ability than chemical manganese oxide.

[0049] Table 2 XRD analysis of manganese ore before and after use

[0050]

[0051] After operation, iron-manganese-oxygen compounds were formed on the surface of the manganese ore, indicating that the manganese ore can effectively adsorb the iron ions in the effluent. The total iron adsorbed by the manganese ore in the wetland was measured, and the adsorption amount increased from 0.012 mg / g to 0.88 mg / g. In addition, the total iron concentration of the effluent from the two wetlands CW-Fe and CW-Mn was measured during the experiment. It was found that manganese ore can effectively solve the problem of high iron ion dissolution concentration in the early stage of the experiment, and the effluent concentration is stabilized below 1 mg / L.

[0052] It is worth noting that the matrices of gravel layer (S1, S4), iron-carbon layer (S2, S5) and manganese layer (S3) of CW-Mn wetland and CW-Fe wetland were taken, ultrasonically shaken, and filtered with 0.2 μm filter membrane. The microbial samples were subjected to qPCR and microbial diversity analysis. The results are shown in Figure 7 shown.

[0053] Figure 7 (a)-(b) are the results of qPCR of nitrification and denitrification functional genes of S1-S5 samples. Regarding the content of AOB, the number of S1 is 5.8 times that of S4. Although the ammonia nitrogen concentration along the long-term operation of the two wetlands is close at the sampling points S1 and S4 during the stable stage, the higher AOB content in S1 indicates that it may have a higher ammonia oxidation capacity, which means that when the influent ammonia nitrogen concentration is higher or there is a shock load of ammonia nitrogen, the CW-Mn wetland can maintain the stability of the effluent ammonia nitrogen concentration, while the CW-Fe wetland cannot guarantee it. narG is a functional gene for reducing nitrate nitrogen to nitrite nitrogen. The number in S2 is higher than that in S5, and the content in S3 is 77 and 282 times that of the two. The higher narG content ensures that the concentration of nitrate nitrogen in the effluent of CW-Mn wetland is lower than that of CW-Fe wetland.

[0054] like Figure 7 As shown in (c), the ratios of nosZ / (nirs+nirK) in the three samples S2, S3, and S5 were 0.091, 0.082, and 0.073, respectively, indicating that S5 released more nitrous oxide than S2 and S3. This result shows that the CW-Mn wetland has a lower nitrous oxide release. Considering the number of functional genes and the structure of the microbial community together, it can be inferred that the addition of manganese ore to the CW-Fe wetland can promote the enrichment of front-end ammonia oxidizing microorganisms and back-end denitrifying microorganisms in the wetland, achieving the purpose of removing ammonia nitrogen and nitrate nitrogen at the same time, solving the problem of high ammonia nitrogen in the effluent during the use of the CW-Fe wetland.

[0055] It can be seen that in S3, the content of manganese oxidizing bacteria is not dominant, and the abundance of iron oxidizing bacteria is relatively high. The analysis results of XRD show that more iron-containing compounds may be attached to the surface of manganese ore, which leads to the increase in the abundance of iron oxidizing bacteria. As shown in Table 3, through XPS analysis, it is found that the content of divalent manganese and trivalent iron on the surface of manganese ore increases, indicating that there may be high-valent manganese oxidizing low-valent iron ions. This oxidation process is the result of the joint action of chemical reactions and microorganisms. Figure 7 The results shown in (a) show that the functional gene content of denitrification in S3 is the highest, which may be related to the redox reaction on the surface of manganese ore. At the same time, the total manganese ion content of the effluent from the CW-Mn wetland was measured, and it was found that as the experiment progressed, the total manganese content in the effluent gradually decreased from 11±0.6μg / L to 6.1±0.4μg / L.

[0056] The decrease in concentration may be due to the adhesion of adsorbed iron compounds, which hindered the dissolution of manganese ions. High concentrations of manganese ions have an adverse effect on microorganisms. However, the iron compounds adsorbed by manganese ore hindered the dissolution of manganese ions, which in turn ensured the activity of microorganisms in the wetland. In addition, the loose structure of iron oxide ensured that the surface of manganese ore would not be densely covered, which to a certain extent ensured the continuous redox reaction of manganese and iron ions on the surface, thus maintaining a high denitrification performance.

[0057] Table 3 XPS analysis of manganese ore before and after use

[0058]

[0059]

[0060] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. An iron-carbon-manganese composite filler for artificial wetlands with high efficiency in nitrogen and phosphorus removal, characterized in that: It only includes a gravel layer, an iron-carbon layer and a manganese ore layer; the gravel layer is only located below the iron-carbon layer in the direction of water flow, and the manganese ore layer is located above the iron-carbon layer in the direction of water flow.

2. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to claim 1, characterized in that: The particle size of the gravel in the gravel layer is 1 to 3 cm.

3. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to claim 1, characterized in that: The iron-carbon layer is a compound of iron filings and activated carbon.

4. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to claim 1, characterized in that: The particle size of the manganese ore in the manganese ore layer is 4 to 8 mm.

5. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to claim 3, characterized in that: The volume ratio of iron filings to activated carbon in the iron-carbon layer is 1:1; the iron filings are 2-3 cm long and 0.4-0.6 cm wide; the activated carbon is cylindrical, with a bottom diameter of 0.4-0.6 cm and a height of 1-3 cm.

6. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to claim 3, characterized in that: The iron filings must be soaked in 10% sodium hydroxide solution before use to remove grease, and then diluted sulfuric acid is used to remove rust on the surface of the iron filings.

7. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to claim 3, characterized in that: The gravel, activated carbon and manganese ore must be washed and dried before use.

8. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to any one of claims 1 to 7, characterized in that: The artificial wetland filler can remove 94.76% of the total nitrogen in sewage and 95.9% of ammonia nitrogen; the proportion of ammonia nitrogen in the total nitrogen in the effluent is only 26.08%.

9. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to any one of claims 1 to 7, characterized in that: When the artificial wetland filler is in use, the total phosphorus concentration of the effluent is 0.02-0.1 mg / L, and the total phosphorus removal efficiency is stabilized at 90%.

10. The iron-carbon-manganese composite filler for artificial wetland with high efficiency in nitrogen and phosphorus removal according to any one of claims 1 to 7, characterized in that: When the artificial wetland filler is used, the content of iron ions in the effluent water is stabilized below 1 mg / L, and the content of manganese ions is stabilized below 10 μg / L.

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