Combined filler for nitrogen and phosphorus removal of constructed wetland, nitrogen and phosphorus removal device for constructed wetland and application of nitrogen and phosphorus removal device

Abstract

The invention belongs to the technical field of sewage treatment, and provides a constructed wetland nitrogen and phosphorus removal combined filler, a constructed wetland nitrogen and phosphorus removal device and application of the constructed wetland nitrogen and phosphorus removal device, and the combined filler comprises the following components in parts by mass: 7.5-8 parts of a sulfur autotrophic synthetic material, 2-4 parts of wheat straw, 8-12 parts of zeolite and 4-6 parts of a phosphorus removal synthetic material. The invention further provides a nitrogen and phosphorus removal device for the constructed wetland. The nitrogen and phosphorus removal device comprises a plant layer, a nitrogen removal layer, a phosphorus removal layer and a supporting layer from top to bottom in sequence, the denitrification layer and the dephosphorization layer are filled with the combined filler for denitrification and dephosphorization of the constructed wetland. When the filler is added into the constructed wetland, a sulfur autotrophy and heterotrophy synergistic denitrification system can be formed, and an efficient effect is achieved on nitrogen and phosphorus removal of wastewater. The combined filler is introduced for filling, so that deep treatment of nitrogen and phosphorus in secondary effluent by the wetland can be effectively improved, and compared with artificial wetlands purely added with gravels and filled in a mixed manner, the constructed wetland has remarkable advantages.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a combined filler for artificial wetland denitrification and dephosphorization, an artificial wetland denitrification and dephosphorization device and applications thereof. Background Art

[0002] Secondary effluent is a large amount of sewage generated during the sewage treatment process. There are still certain concentrations of nitrogen and phosphorus pollutants in the secondary effluent. The discharge of untreated secondary effluent will lead to eutrophication of lakes and rivers. This will continue to pollute the water environment and have an impact on human life. In order to avoid the destruction of the ecosystem caused by nitrogen and phosphorus pollutants, more efficient and low-energy technology is needed to deeply treat the nitrogen and phosphorus pollutants in the secondary effluent.

[0003] At present, there are many application scenarios for treating secondary effluent, such as artificial wetlands, biological filters, etc. Artificial wetland treatment technology is currently a common secondary effluent deep water treatment technology. It has certain ecological landscape value while deeply treating secondary effluent. In addition, artificial wetlands have good and stable treatment effects, low investment costs, and are easy to maintain and manage, so they are widely used. Artificial wetlands are artificially constructed and controlled, and sewage and sludge are controlled and distributed to artificial wetlands. A technology that uses the physical, chemical, and biological synergistic effects of substrates, plants, and microorganisms to treat sewage and sludge. Artificial wetlands are mainly divided into surface flow, horizontal flow, vertical flow, and composite artificial wetlands. Among them, vertical flow artificial wetlands are widely used due to their high efficiency and convenience.

[0004] However, there are still some difficult problems in artificial wetlands, especially in treating nitrogen and phosphorus pollutants in secondary effluent. In the process of deep denitrification and phosphorus removal, problems such as insufficient carbon source, filler setting, and insufficient electron donors lead to low denitrification and phosphorus removal efficiency. These all limit the performance of artificial wetlands in denitrification and phosphorus removal.

[0005] Studies have shown that Wang et al. (Hong-cheng W, Ying L, Yu-meng Y, et al. Elementsulfur-based autotrophic denitrification constructed wetland as an efficientapproach for nitrogen removal from low C / N wastewater[J]. Water Research, 2022, 226119258-119258.) explored the effects of nitrogen removal and phosphorus removal under different C / N conditions by constructing sulfur-based artificial wetlands (SCW) and traditional artificial wetlands (CW). It was found that the sulfur autotrophic denitrification in SCW is stronger than the denitrification capacity of CW, and it is proved that the CW-SCW combined system is an efficient operation mode for the simultaneous removal of total ammonia nitrogen and nitrate. However, sulfur autotrophic denitrification dominated by elemental sulfur will cause the pH of the effluent to be in an acidic environment, which inhibits the denitrification process involving microorganisms. The simple sulfur autotrophic denitrification produces SO4 2-More, it will cause certain damage to the water environment and is not suitable for the deep treatment of secondary effluent. Wang et al. (Wang H, Li Y, Zhang S, et al. Effect of influent feeding pattern on municipal tailwater treatment during a sulfur-based denitrification constructed wetland [J]. Bioresource Technology, 2020, 315 (prepublish): 123807-123807.) filled the constructed artificial wetland (CW) reactor with a volume ratio of 1:1:1:1:1 of elemental sulfur, limestone, zeolite and volcanic rock, and found that the vertical flow artificial wetland can achieve a nitrate removal rate of 96.10%, and the pH acidity increases due to the presence of limestone. However, it ignores the production of by-products, and the consumption of sulfur sources is also a problem that needs to be solved today. Si et al. (Si Z, Song X, Wang Y, et al. Intensified heterotrophic denitrification inconstructed wetlands using four solid carbon sources: Denitrification efficiency and bacterial community structure [J]. Bioresource Technology, 2018, 267416-425.) used wheat straw, cotton, polybutylene succinate and newspaper as carbon sources, and compared the denitrification efficiency and bacterial community of constructed wetlands under low and high temperature conditions. The study showed that newspaper can participate in biological heterotrophic denitrification, and wheat straw has a higher denitrification efficiency, proving that solid carbon sources play an advantage in heterotrophic denitrification. However, straw-based solid carbon sources will produce a certain color, which will have a certain impact on the effluent, and the excessive addition of carbon sources will increase the amount of microorganisms, resulting in excessive sludge, increasing the system's processing load and affecting the treatment effect. The invention patent "A method for enhancing denitrification in artificial wetlands using modified biochar with strong carbon secretion" (patent number: CN106927571A) mixes modified biochar with strong carbon secretion with a matrix as a filler and fills it into the artificial wetland bed, realizing the iron-carbon redox cycle. However, the preparation process of the filler is relatively complicated, the mixed filling method is too simple, and the mixing method of the filler may cause clogging of the artificial wetland.The invention patent "An artificial wetland denitrification system and its sewage denitrification method" (patent number: CN113511728A) improves the denitrification effect of sewage by sequentially arranging a soil layer, a limestone filler layer, a rice bran heterotrophic and siderite autotrophic synergistic filler layer, and a zeolite filler layer from top to bottom. This method demonstrates the advantages of autotrophic and heterotrophic synergy. However, this filling method will increase the difficulty of subsequent filler replacement and limit its application in actual production. In addition, the iron content in iron autotrophic denitrification will directly affect the denitrification effect. Excessive iron will inhibit the activity of microorganisms and thus affect the denitrification effect.

[0006] Therefore, sulfur autotrophic and heterotrophic synergistic denitrification is still the mainstream process, and it is urgent to find more efficient and safe sulfur autotrophic denitrification materials. For artificial wetlands, the filling method of a single denitrification and phosphorus removal filler is not as efficient as the filling method of a combination of multiple fillers. At present, the filling method of multiple combination fillers is still a problem that needs to be overcome. Therefore, while looking for efficient and safe denitrification and phosphorus removal fillers, the choice of filling method is also the key.

[0007] Those skilled in the art are in urgent need of disclosing a device and method for enhancing nitrogen and phosphorus removal in artificial wetlands by using sulfur autotrophic and synergistic heterotrophic technologies, so as to solve the current problems of insufficient carbon sources in artificial wetlands and low efficiency of deep nitrogen and phosphorus removal. Summary of the invention

[0008] The purpose of the present invention is to overcome the problems in the prior art and to provide a combined filler for denitrification and dephosphorization in an artificial wetland, a denitrification and dephosphorization device in an artificial wetland and applications thereof.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0010] The invention provides a composite filler for denitrification and phosphorus removal in an artificial wetland, comprising the following components in parts by mass: 7.5 to 8 parts of sulfur autotrophic synthetic material, 2 to 4 parts of wheat straw, 8 to 12 parts of zeolite, and 4 to 6 parts of phosphorus removal synthetic material.

[0011] Preferably, the sulfur autotrophic synthetic material comprises elemental sulfur and calcium carbonate; the mass ratio of the elemental sulfur to calcium carbonate is 1.25 to 3:1;

[0012] The particle size of the sulfur autotrophic synthetic material is 3 to 5 mm.

[0013] Preferably, the synthetic phosphorus removal material comprises dolomite, montmorillonite, starch and aluminum sulfate;

[0014] The mass ratio of dolomite, montmorillonite, starch and aluminum sulfate is 1-3:1-3:2:2;

[0015] The particle size of the phosphorus removal synthetic material is 3 to 5 mm.

[0016] Preferably, the length of the wheat straw is 0.5 to 1 cm, and the particle size of the zeolite is 2 to 4 mm.

[0017] The present invention also provides a constructed wetland denitrification and dephosphorization device, wherein the device comprises a plant layer, a denitrification layer, a dephosphorization layer and a support layer from top to bottom;

[0018] The combined filler for denitrification and phosphorus removal in artificial wetlands is filled in the denitrification layer and the phosphorus removal layer.

[0019] Preferably, the denitrification layer comprises sulfur autotrophic synthetic material, wheat straw and a first portion of zeolite;

[0020] The mass of the first part of zeolite is 60-70% of the mass of the zeolite.

[0021] Preferably, the sulfur autotrophic synthetic material, wheat straw and the first part of zeolite in the denitrification layer are filled in a mixed manner or in a layered manner;

[0022] The layered fillings are sulfur autotrophic synthetic material, upper layer zeolite, wheat straw, and lower layer zeolite from top to bottom; or;

[0023] Wheat straw, upper layer zeolite, sulfur autotrophic synthetic material, lower layer zeolite;

[0024] The mass ratio of the upper layer zeolite to the lower layer zeolite is 5-6:6-7.

[0025] Preferably, the phosphorus removal layer comprises a phosphorus removal synthetic material and residual zeolite;

[0026] The filling method in the dephosphorization layer is mixed filling.

[0027] The present invention also provides the application of the artificial wetland denitrification and phosphorus removal device in deep treatment of secondary effluent, and the application method is as follows:

[0028] Sulfur autotrophic denitrification sludge is inoculated into the constructed wetland nitrogen and phosphorus removal device, and then the secondary effluent is treated.

[0029] Preferably, the dosage ratio of the sulfur autotrophic denitrification sludge and the combined filler for artificial wetland denitrification and phosphorus removal in the artificial wetland denitrification and phosphorus removal device is 1-3 mL: 1-11 g;

[0030] The water inlet of the secondary effluent is 10-14 L / d;

[0031] The treatment temperature is 25-30° C. and the treatment time is 1-40 days.

[0032] The present invention provides a combined filler for denitrification and phosphorus removal in an artificial wetland, comprising the following components by mass: 7.5 to 8 parts of sulfur autotrophic synthetic material, 2 to 4 parts of wheat straw, 8 to 12 parts of zeolite, and 4 to 6 parts of phosphorus removal synthetic material. The present invention also provides a device for denitrification and phosphorus removal in an artificial wetland, wherein the device comprises a plant layer, a denitrification layer, a phosphorus removal layer, and a support layer from top to bottom; the combined filler for denitrification and phosphorus removal in an artificial wetland is filled in the denitrification layer and the phosphorus removal layer. By adding the filler in the artificial wetland, a system of sulfur autotrophic heterotrophic synergistic denitrification can be formed, and different filling methods have a strong effect on denitrification, and the filling of zeolite can prevent a certain degree of blockage. This produces a highly efficient effect on the denitrification and phosphorus removal of wastewater. The invention introduces a combined filler for filling, which can effectively improve the deep treatment of nitrogen and phosphorus in the secondary effluent by the wetland, and has significant advantages over the artificial wetland with the simple addition of gravel and mixed filling. In addition, the addition of wheat straw is conducive to the resource utilization of agricultural waste.

[0033] The present invention adopts a combined filler for denitrification and phosphorus removal in artificial wetlands, which can efficiently treat nitrogen and phosphorus pollutants in secondary effluent. While sulfur autotrophic denitrification produces acid, wheat straw participates in heterotrophic denitrification to produce alkali, thereby neutralizing pH and solving the problem of excessive acid or alkalinity in the water environment; zeolite, as an inert material, can undergo adsorption and fully adsorb ammonia nitrogen in the secondary effluent. Wheat straw and sulfur autotrophic synthetic materials participate in synergistic denitrification as microbial carriers, providing sufficient sulfur source and carbon source for the entire system, promoting the progress of denitrification, and the filling method of wheat straw in the upper layer can be replaced in time while ensuring the occurrence of synergistic denitrification, ensuring the resource utilization of agricultural waste. The sulfur autotrophic synthetic material and wheat straw are combined with zeolite for filling, which, on the one hand, promotes the removal of nitrogen pollutants and, on the other hand, can prevent clogging. The combination of phosphorus removal synthetic material and zeolite also ensures the secondary removal of residual ammonia nitrogen in the denitrification layer while removing phosphate.

[0034] The raw material cost adopted by the present invention is low, the material combination method is simple, the operation is simple and convenient, and the problems of low utilization rate of existing fillers, insufficient carbon source and inability to utilize agricultural resources can be further solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the artificial wetland denitrification and phosphorus removal device of the present invention;

[0036] Among them, 1 is the plant layer, 2 is the denitrification layer, 3 is the phosphorus removal layer, 4 is the supporting layer, 5 is the windmill grass, and 6 is the base;

[0037] Figure 2 The line graph of the treatment of nitrate in secondary effluent in Examples 1 to 3;

[0038] Figure 3The line graph of the treatment of ammonia nitrogen in secondary effluent in Examples 1 to 3 is shown;

[0039] Figure 4 The line graph of the treatment of phosphate in secondary effluent in Examples 1 to 3 is as follows;

[0040] Figure 5 This is a line graph of the treatment of nitrate in secondary effluent by Application Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0041] The invention provides a composite filler for denitrification and phosphorus removal in an artificial wetland, comprising the following components in parts by mass: 7.5 to 8 parts of sulfur autotrophic synthetic material, 2 to 4 parts of wheat straw, 8 to 12 parts of zeolite, and 4 to 6 parts of phosphorus removal synthetic material.

[0042] In the present invention, the weight fraction of the sulfur autotrophic synthetic material is preferably 7.6 to 7.9 parts, more preferably 7.7 to 7.8 parts, and even more preferably 7.74 to 7.76 parts.

[0043] In the present invention, the mass fraction of the wheat straw is preferably 2.3 to 3.7 parts, more preferably 2.6 to 3.4 parts, and even more preferably 2.8 to 3.2 parts.

[0044] In the present invention, the mass fraction of the zeolite is preferably 8.5 to 11.5 parts, more preferably 9 to 11 parts, and even more preferably 9.5 to 10.5 parts.

[0045] In the present invention, the weight fraction of the phosphorus removal synthetic material is preferably 4.5 to 5.5 parts, more preferably 4.6 to 5.4 parts, and even more preferably 4.8 to 5.2 parts.

[0046] In the present invention, the sulfur autotrophic synthetic material comprises elemental sulfur and calcium carbonate; the mass ratio of the elemental sulfur to calcium carbonate is preferably 1.25 to 3:1, more preferably 1.5 to 2.5:1, and more preferably 1.8 to 2.2:1.

[0047] In the present invention, the particle size of the sulfur autotrophic synthetic material is preferably 3 to 5 mm, more preferably 3.5 to 4.5 mm, and even more preferably 3.8 to 4.2 mm.

[0048] In the present invention, the synthetic phosphorus removal material comprises dolomite, montmorillonite, starch and aluminum sulfate.

[0049] In the present invention, the mass ratio of dolomite, montmorillonite, starch and aluminum sulfate is preferably 1-3:1-3:2:2, more preferably 1.5-2.5:1.5-2.5:2:2, and more preferably 1.8-2.2:1.8-2.2:2:2.

[0050] In the present invention, the particle size of the phosphorus removal synthetic material is preferably 3 to 5 mm, more preferably 3.5 to 4.5 mm, and even more preferably 3.8 to 4.2 mm.

[0051] In the present invention, the length of the wheat straw is preferably 0.5-1 cm, more preferably 0.6-0.9 cm, and more preferably 0.7-0.8 cm; the particle size of the zeolite is preferably 2-4 mm, more preferably 2.5-3.5 mm, and more preferably 2.8-3.2 mm.

[0052] The present invention also provides an artificial wetland denitrification and phosphorus removal device, which comprises a plant layer, a denitrification layer, a phosphorus removal layer and a supporting layer from top to bottom.

[0053] The combined filler for denitrification and phosphorus removal in artificial wetlands is filled in the denitrification layer and the phosphorus removal layer.

[0054] In the present invention, windmill grass is planted in the plant layer, and the organic matter secreted by the root system penetrates into the denitrification layer, and the roots can fully absorb the nitrogen and phosphorus pollutants in the water.

[0055] In the present invention, the filling matrix in the plant layer is gravel, and the particle size of the gravel is preferably 4 to 6 mm, and more preferably 5 mm.

[0056] In the present invention, the denitrification layer comprises sulfur autotrophic synthetic material, wheat straw and a first portion of zeolite.

[0057] In the present invention, the mass of the first part of zeolite is preferably 60 to 70% of the mass of the zeolite, more preferably 62 to 68%, and even more preferably 64 to 66%.

[0058] In the present invention, the sulfur autotrophic synthetic material, wheat straw and the first part of zeolite in the denitrification layer are filled in a mixed manner or in a layered manner.

[0059] The layered fillings are sulfur autotrophic synthetic material, upper layer zeolite, wheat straw, and lower layer zeolite from top to bottom; or;

[0060] Wheat straw, upper layer zeolite, sulfur autotrophic synthetic material, lower layer zeolite.

[0061] The mass ratio of the upper layer zeolite to the lower layer zeolite is preferably 5 to 6:6 to 7, more preferably 5.2 to 5.8:6.2 to 6.8, and even more preferably 5.4 to 5.6:6.4 to 6.6.

[0062] In the present invention, the phosphorus removal layer contains the phosphorus removal synthetic material and the remaining zeolite.

[0063] The filling method in the dephosphorization layer is mixed filling.

[0064] In the present invention, the filling matrix in the supporting layer is gravel, and the particle size of the gravel is preferably 4 to 6 mm, and more preferably 5 mm.

[0065] The present invention also provides an application of an artificial wetland denitrification and phosphorus removal device in deep treatment of secondary effluent, and the application method is as follows:

[0066] Sulfur autotrophic denitrification sludge is inoculated into the constructed wetland nitrogen and phosphorus removal device, and then the secondary effluent is treated.

[0067] In the present invention, the dosage ratio of the sulfur autotrophic denitrification sludge and the combined filler for artificial wetland denitrification and phosphorus removal in the artificial wetland denitrification and phosphorus removal device is preferably 1-3 mL: 1-11 g, more preferably 1.5-2.5 mL: 2-10 g, and more preferably 1.8-2.2 mL: 4-6 g.

[0068] In the present invention, biofilm formation is required after inoculation of sulfur autotrophic denitrification sludge, and the biofilm formation time is preferably 1 to 3 days, more preferably 2 days.

[0069] In the present invention, the water inlet volume of the secondary effluent is preferably 10 to 14 L / d, more preferably 11 to 13 L / d, and more preferably 12 L / d.

[0070] In the present invention, the nitrate concentration in the secondary effluent is preferably 10-15 mg / L, more preferably 11-14 mg / L, more preferably 12-13 mg / L; the ammonia nitrogen concentration is preferably 8-10 mg / L, more preferably 8.5-9.5 mg / L, more preferably 8.8-9.2 mg / L; the phosphate concentration is preferably 1-1.5 mg / L, more preferably 1.1-1.4 mg / L, more preferably 1.2-1.3 mg / L.

[0071] In the present invention, the treatment temperature is preferably 25 to 30° C., more preferably 26 to 29° C., and more preferably 27 to 28° C.; the treatment time is preferably 1 to 40 days, more preferably 10 to 30 days, and more preferably 15 to 25 days.

[0072] The schematic diagram of the artificial wetland denitrification and phosphorus removal device of the present invention is as follows Figure 1 As shown, 1 is the plant layer, 2 is the denitrification layer, 3 is the phosphorus removal layer, 4 is the supporting layer, 5 is windmill grass, 6 is the base, and A, B, C, D, E, and F are all water outlets for sampling and testing of water bodies.

[0073] In the present invention, the whole system of the artificial wetland denitrification and phosphorus removal device firstly takes in water and discharges water from the secondary stage. The operation mode is to take in water from the top to the bottom, and when passing through the plant layer, the plant stems and roots will absorb pollutants while contacting the gravel and the secondary discharge water; then enter the denitrification layer, and the sulfur autotrophic denitrification led by the sulfur autotrophic synthetic material and the heterotrophic denitrification led by the wheat straw will drive the process of sulfur autotrophic and heterotrophic synergistic denitrification, and the zeolite can play the role of absorbing ammonia, so that the effect of double denitrification can be achieved; then enter the phosphorus removal layer, the phosphorus removal synthetic material reacts with the phosphate to form a precipitate to achieve the effect of removing phosphorus pollutants, and the supplement of zeolite will prevent the whole system from being blocked, and the residual ammonia nitrogen in the upper layer will be deeply removed. This can achieve the triple synergistic effect of plants, fillers and microorganisms.

[0074] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0075] Example 1

[0076] 8 parts of sulfur autotrophic synthetic material, 3 parts of wheat straw, 10 parts of zeolite, and 5 parts of phosphorus removal synthetic material (the mass ratio of elemental sulfur and calcium carbonate in the sulfur autotrophic synthetic material is 2:1, and the particle size of the sulfur autotrophic synthetic material is 4 mm; the mass ratio of dolomite, montmorillonite, starch and aluminum sulfate in the phosphorus removal synthetic material is 2:2:2:2, and the particle size of the phosphorus removal synthetic material is 2 mm; the length of the wheat straw is 1 cm, and the particle size of the zeolite is 3 mm).

[0077] A simulated vertical flow artificial wetland was constructed, which consisted of a plant layer, a denitrification layer, a phosphorus removal layer and a support layer from top to bottom. Five windmill grasses were planted in the plant layer, and the filling matrix was gravel with a particle size of 4 to 6 mm; the mass of the first part of zeolite in the denitrification layer was 66% of the mass of the zeolite; sulfur autotrophic synthetic materials, wheat straw and the first part of zeolite were mixed and filled; the phosphorus removal synthetic materials and the remaining zeolite were mixed and filled in the phosphorus removal layer; the particle size of the gravel in the support layer was 4 to 6 mm. Water is introduced through a peristaltic pump and inoculated with sulfur autotrophic denitrification sludge. The dosage ratio of sulfur autotrophic denitrification sludge and the combined filler for artificial wetland denitrification and phosphorus removal in the artificial wetland denitrification and phosphorus removal device is 2mL:5g, and the biofilm formation time is 2 days. The water inlet of the secondary effluent is 12L / d, and the nitrate concentration of the secondary effluent is 12mg / L, the ammonia nitrogen concentration is 10mg / L, and the phosphate concentration is 1.5mg / L. The six outlets are sampled and tested every day and treated at 28°C for 40 days.

[0078] Example 2

[0079] 7.6 parts of sulfur autotrophic synthetic material, 2.7 parts of wheat straw, 11.4 parts of zeolite, and 5 parts of phosphorus removal synthetic material (the mass ratio of elemental sulfur and calcium carbonate in the sulfur autotrophic synthetic material is 1.8:1, and the particle size of the sulfur autotrophic synthetic material is 3 mm; the mass ratio of dolomite, montmorillonite, starch and aluminum sulfate in the phosphorus removal synthetic material is 1.8:2.5:2:2, and the particle size of the phosphorus removal synthetic material is 2 mm; the length of the wheat straw is 0.8 cm, and the particle size of the zeolite is 2.6 mm).

[0080] A simulated vertical flow artificial wetland was constructed, which consisted of a plant layer, a denitrification layer, a phosphorus removal layer and a support layer from top to bottom. Three windmill grasses were planted in the plant layer, and the filling matrix was gravel with a particle size of 4 to 6 mm; the mass of the first part of zeolite in the denitrification layer was 65% of the mass of zeolite; it was filled from top to bottom in the manner of sulfur autotrophic synthetic material, upper zeolite, wheat straw, and lower zeolite, with the mass ratio of the upper zeolite to the lower zeolite being 5.5:6.5; the phosphorus removal layer was filled with a mixture of phosphorus removal synthetic material and the remaining zeolite; the particle size of the gravel in the support layer was 4 to 6 mm. Water is introduced through a peristaltic pump and inoculated with sulfur autotrophic denitrification sludge. The dosage ratio of sulfur autotrophic denitrification sludge and the combined filler for artificial wetland denitrification and phosphorus removal in the artificial wetland denitrification and phosphorus removal device is 2mL:5g, and the biofilm formation time is 2 days. The water inlet of the secondary effluent is 12L / d, and the nitrate concentration of the secondary effluent is 12mg / L, the ammonia nitrogen concentration is 10mg / L, and the phosphate concentration is 1.5mg / L. The six outlets are sampled and tested every day and treated at 28°C for 40 days.

[0081] Example 3

[0082] 7.8 parts of sulfur autotrophic synthetic material, 3.8 parts of wheat straw, 9.6 parts of zeolite, and 5 parts of phosphorus removal synthetic material (the mass ratio of elemental sulfur and calcium carbonate in the sulfur autotrophic synthetic material is 2.7:1, and the particle size of the sulfur autotrophic synthetic material is 3 mm; the mass ratio of dolomite, montmorillonite, starch and aluminum sulfate in the phosphorus removal synthetic material is 2.8:1.1:2:2, and the particle size of the phosphorus removal synthetic material is 2 mm; the length of the wheat straw is 0.5 cm, and the particle size of the zeolite is 3.8 mm).

[0083] A simulated vertical flow artificial wetland was constructed, which consisted of a plant layer, a denitrification layer, a phosphorus removal layer and a support layer from top to bottom. Five windmill grasses were planted in the plant layer, and the filling matrix was gravel with a particle size of 4 to 6 mm; the mass of the first part of zeolite in the denitrification layer was 68% of the mass of zeolite; it was filled from top to bottom in the manner of wheat straw, upper zeolite, sulfur autotrophic synthetic material, and lower zeolite, with the mass ratio of the upper zeolite to the lower zeolite being 5:6; the phosphorus removal layer was filled with a mixture of phosphorus removal synthetic material and the remaining zeolite; the particle size of the gravel in the support layer was 4 to 6 mm. Water is introduced through a peristaltic pump and inoculated with sulfur autotrophic denitrification sludge. The dosage ratio of sulfur autotrophic denitrification sludge and the combined filler for artificial wetland denitrification and phosphorus removal in the artificial wetland denitrification and phosphorus removal device is 2mL:5g, and the biofilm formation time is 2 days. The water inlet of the secondary effluent is 12L / d, and the nitrate concentration of the secondary effluent is 12mg / L, the ammonia nitrogen concentration is 10mg / L, and the phosphate concentration is 1.5mg / L. The six outlets are sampled and tested every day and treated at 28°C for 40 days.

[0084] The treatment of nitrate in secondary effluent in Examples 1 to 3 is as follows Figure 2 As shown in Figure 2, the treatment of ammonia nitrogen in the secondary effluent is as follows: Figure 3 As shown in Figure 2, the treatment of phosphate in the secondary effluent is as follows: Figure 4 As shown, Influent represents secondary effluent, H represents Example 1, F-1 represents Example 2, and F-2 represents Example 3. Figure 2 to Figure 4 It can be seen that the nitrate nitrogen concentration in the effluent of the denitrification layer of Example 1 with mixed filling is between 0.5 and 4 mg / L. Due to the presence of zeolite, the removal effect of ammonia nitrogen is better, and the effluent concentration is between 3 and 8 mg / L. This shows that the method of combined fillers can achieve efficient denitrification, but the removal of ammonia nitrogen still requires the adsorption of zeolite in the phosphorus removal layer. In Example 2, the nitrate nitrogen concentration in the effluent of the denitrification layer is between 0.5 and 2 mg / L. Due to the presence of zeolite, the removal effect of ammonia nitrogen is better, and the effluent concentration is between 2 and 8 mg / L. Zeolite in the phosphorus removal layer is still required for ammonia absorption. Because the sulfur autotrophic synthetic material is in the upper layer, sulfur autotrophic denitrification occurs first, followed by heterotrophic denitrification, which not only shows a synergistic effect, but also performs its respective duties. In Example 3, the nitrate nitrogen concentration in the effluent of the denitrification layer is between 0.5 and 1 mg / L. The ammonia nitrogen removal effect is better due to the presence of zeolite, and the effluent concentration is between 0.5 and 1 mg / L. This filling method has a better denitrification effect. Because the wheat straw is in the upper layer, heterotrophic denitrification occurs first, and then sulfur autotrophic denitrification occurs. Therefore, it is easier to denitrify under the condition of sufficient carbon source, and then synergistic denitrification is carried out, and the removal effect is better.

[0085] Application Example 1

[0086] According to the method of Example 3, a traditional vertical flow artificial wetland was built, the secondary effluent design water volume was 14 L / d, sampling was performed once a day for water quality analysis, and the operation time was 30 days.

[0087] Comparative Example 1

[0088] A traditional vertical flow artificial wetland was built according to the method of Application Example 1, with the following differences: each layer of filler is gravel, the secondary effluent design water volume is 14L / d, sampling is carried out once a day for water quality analysis, and the operation time is 30 days.

[0089] The treatment of nitrate in the secondary effluent of Application Example 1 and Comparative Example 1 is as follows: Figure 5 As shown, Influent represents secondary effluent, CW represents Application Example 1, and CW-0 represents Comparative Example 1. Figure 5 It can be seen that Application Example 1 shows that the system can achieve efficient nitrogen removal. As time goes by, the nitrogen removal efficiency is stable. Due to the coordinated denitrification, the pH can be kept stable and the output of sulfate ions is low. Comparative Example 1 shows that the system can denitrify, but the nitrogen removal effect is poor. The nitrate nitrogen concentration in the effluent is 6-8 mg / L. Compared with Application Example 1, the effect is not outstanding.

[0090] As can be seen from the above embodiments, the present invention provides a composite filler that can achieve efficient synergistic denitrification and realize the resource recycling of agricultural waste. This is an innovation in the filler setting for treating secondary effluent in artificial wetlands, and will provide a broader application scenario for the resource recycling of agricultural waste.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite filler for denitrification and phosphorus removal in artificial wetlands, characterized in that: The invention comprises the following components in parts by weight: 7.5 to 8 parts of sulfur autotrophic synthetic material, 2 to 4 parts of wheat straw, 8 to 12 parts of zeolite and 4 to 6 parts of phosphorus removal synthetic material.

2. The combined filler for denitrification and phosphorus removal in artificial wetlands according to claim 1, characterized in that: The sulfur autotrophic synthetic material comprises elemental sulfur and calcium carbonate; the mass ratio of the elemental sulfur to calcium carbonate is 1.25 to 3:1; The particle size of the sulfur autotrophic synthetic material is 3 to 5 mm.

3. The combined filler for denitrification and phosphorus removal in artificial wetlands according to claim 1 or 2, characterized in that: The synthetic phosphorus removal material comprises dolomite, montmorillonite, starch and aluminum sulfate; The mass ratio of dolomite, montmorillonite, starch and aluminum sulfate is 1-3:1-3:2:2; The particle size of the phosphorus removal synthetic material is 3 to 5 mm.

4. The combined filler for denitrification and phosphorus removal in artificial wetlands according to claim 3, characterized in that: The length of the wheat straw is 0.5-1 cm, and the particle size of the zeolite is 2-4 mm.

5. An artificial wetland denitrification and phosphorus removal device, characterized in that: The device comprises a plant layer, a nitrogen removal layer, a phosphorus removal layer and a support layer from top to bottom; The combined filler for denitrification and phosphorus removal in an artificial wetland according to any one of claims 1 to 4 is filled in the denitrification layer and the phosphorus removal layer.

6. The artificial wetland denitrification and phosphorus removal device according to claim 5, characterized in that: The denitrification layer comprises sulfur autotrophic synthetic material, wheat straw and a first portion of zeolite; The mass of the first part of zeolite is 60-70% of the mass of the zeolite in claim 1.

7. The artificial wetland denitrification and phosphorus removal device according to claim 5 or 6, characterized in that: The filling method of the sulfur autotrophic synthetic material, wheat straw and the first part of zeolite in the denitrification layer is mixed filling or layered filling; The layered fillings are sulfur autotrophic synthetic material, upper layer zeolite, wheat straw, and lower layer zeolite from top to bottom; or; Wheat straw, upper layer zeolite, sulfur autotrophic synthetic material, lower layer zeolite; The mass ratio of the upper layer zeolite to the lower layer zeolite is 5-6:6-7.

8. The artificial wetland denitrification and phosphorus removal device according to claim 7, characterized in that: The phosphorus removal layer contains phosphorus removal synthetic materials and residual zeolite; The filling method in the dephosphorization layer is mixed filling.

9. Application of the artificial wetland denitrification and phosphorus removal device according to claims 5 to 8 in deep treatment of secondary effluent, characterized in that: The method of the application is as follows: Sulfur autotrophic denitrification sludge is inoculated into the constructed wetland nitrogen and phosphorus removal device, and then the secondary effluent is treated.

10. The use according to claim 9, characterized in that The dosage ratio of the sulfur autotrophic denitrification sludge and the combined filler for artificial wetland denitrification and phosphorus removal in the artificial wetland denitrification and phosphorus removal device is 1-3 mL: 1-11 g; The water inlet of the secondary effluent is 10-14 L / d; The treatment temperature is 25-30° C. and the treatment time is 1-40 days.

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