A rural ditch nitrogen and phosphorus interception system and method

Abstract

The application discloses an ecological rural ditch nitrogen and phosphorus interception system and method, belongs to the technical field of agricultural non-point source pollution control and water environment treatment, and provides an innovative "buffer-purification-interception" composite ecological rural ditch nitrogen and phosphorus interception technology. Under the premise of not interfering with normal production activities of farmland, the ecological function of the ditch is enhanced through optimization of ditch design and ecological structure, and nitrogen and phosphorus are removed through multiple levels, so that efficient interception and purification of nitrogen, phosphorus and other pollutants in farmland drainage are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of agricultural non-point source pollution control and water environment management, and particularly relates to a rural ditch nitrogen and phosphorus interception system and method. BACKGROUND

[0002] Ecological ditch technology is a wastewater treatment method that mimics natural wetlands. Its core principle is to effectively intercept and degrade nutrients such as nitrogen and phosphorus in farmland drainage through physical, chemical, and biological processes in the ditch. In this process, aquatic plants and microbial communities in sediments play a crucial role. The root system of aquatic plants can not only directly absorb pollutants such as ammonia nitrogen, nitrate nitrogen, and phosphorus, but also accelerate the transfer of pollutants to sediments by promoting interfacial exchange reactions, thereby improving the interception capacity of the ditch. In China, with the large number of new construction and reconstruction of ecological ditches, their role in non-point source wastewater interception and treatment is increasingly prominent.

[0003] However, the existing technology also has the following problems: 1. Limited removal efficiency, the removal efficiency of ordinary ecological ditches for nitrogen and phosphorus pollutants is usually around 70%, which is mainly limited by the biomass, contact area, reaction efficiency of plants, and the residence time of water in the ditch; when the adsorption in the ditch reaches saturation state, the treatment efficiency will decrease accordingly; 2. Risk of secondary pollution, in ordinary ecological ditches, adsorbed and absorbed pollutants have not been completely treated, in extreme weather conditions such as heavy rain or flood, pollutants may be released in reverse through leaching or dissimilation, causing secondary pollution of water bodies and farmland; 3. Ecological function not fully utilized, ordinary ecological ditches have not been organically integrated with elements such as farmland, ridge, pond, and road, and have not fully played their ecological function in the construction of beautiful countryside and green ecological corridor.

[0004] The Chinese patent document CN111573975A discloses a farmland drainage ecological ditch with purification of nitrogen and phosphorus, comprising an ecological ditch body and a wetland, one side of the ecological ditch body is provided with an artificial drainage channel one, the other side of the ecological ditch body is provided with an artificial drainage channel two, one side of the ecological ditch body is provided with a filter dam one, the other side of the ecological ditch body is provided with a filter dam two, and the beneficial effect is that the ecological ditch can be transferred according to the actual situation, the use mode is flexible, and the practicality is good. The patent mainly utilizes aquatic plants and Myriophyllum verticillatum to remove nitrogen and phosphorus in a single level, and the removal efficiency of aquatic plants and Myriophyllum verticillatum is affected by climate, environment, nutrient supply and other factors, which cannot guarantee sufficient adsorption and conversion of nitrogen and phosphorus in farmland wastewater. SUMMARY

[0005] The main purpose of the present application is to solve the problems of insufficient function of existing farmland ecological system and limited interception and purification capacity of ditch, and to provide an innovative "buffer-purification-interception" composite ecological rural ditch nitrogen and phosphorus interception technology. Under the premise of not interfering with the normal production activities of farmland, the ecological function of the ditch is enhanced by optimizing the design and ecological structure of the ditch, and the nitrogen and phosphorus are removed in multiple levels to achieve efficient interception and purification of nitrogen, phosphorus and other pollutants in farmland drainage.

[0006] To achieve the above purpose, the present application provides an ecological rural ditch nitrogen and phosphorus interception system, which comprises a ditch arranged along the water flow direction, wherein the ditch comprises a first ditch bottom, a second ditch bottom, a third ditch bottom and a bank on both sides, and a sediment buffer zone, a purification unit, a interception conversion pool and a gravel fence are sequentially and communicatively arranged on the ditch; farmland drainage is preliminarily treated and deposited after passing through the sediment buffer zone, then enters the purification unit to remove nitrogen and phosphorus pollutants in the water, then flows through the interception conversion pool for deep treatment to reduce the content of nitrogen and phosphorus in the water, and finally flows through the gravel fence to achieve the final interception and removal of nitrogen and phosphorus pollutants.

[0007] Preferably, the sediment buffer zone comprises a slope falling water area, a buffer flow regulating wall and flow holes, the slope falling water area is arranged at the front end of the ditch and connected with the first ditch bottom, the buffer flow regulating wall is fixed on the first ditch bottom, and the buffer flow regulating wall is provided with a plurality of flow holes.

[0008] Further preferably, the thickness of the buffer flow regulating wall is 20-30 cm, and the number thereof is ≥1.

[0009] Preferably, the purification unit comprises a nitrification-denitrification-phosphorus removal treatment device and an aquatic plant community unit, the nitrification-denitrification-phosphorus removal treatment device is installed on the second ditch bottom; the aquatic plant community unit is located downstream of the nitrification-denitrification-phosphorus removal treatment device.

[0010] Further preferably, the nitrification-denitrification-phosphorus removal treatment device is sequentially provided with a plant growth bag module, an iron-manganese composite oxidation film module, a denitrification module, and a phosphorus adsorption medium module.

[0011] Further preferably, the phosphorus adsorption medium module is provided with a phosphorus adsorption medium, and the preparation method of the phosphorus adsorption medium is as follows:

[0012] (1) The straw is naturally air-dried, cleaned of non-biological impurities, and then crushed to pass through a 40-80 mesh sieve; the crushed and sieved straw and montmorillonite are dispersed in water, lanthanum nitrate pentahydrate is added, and after uniform mixing and stirring, a hydrothermal reaction is carried out, and after the reaction is completed, it is cooled to room temperature, filtered and immersed in dilute sulfuric acid to obtain a composite biochar;

[0013] (2) The composite biochar is dispersed in an ethanol aqueous solution, mercaptopropyltrimethoxysilane is added, and stirring is carried out at room temperature for 2-4 h, then filtered and dried to obtain mercaptobiochar;

[0014] (3) The mercaptobiochar is dispersed in water, guar hydroxypropyltrimethyl ammonium chloride is added, and the pH value is adjusted to 3-4 with hydrochloric acid aqueous solution, and heated for 4-6 h, after the reaction is completed, it is cooled to room temperature, filtered, washed, dried, and ground to obtain a phosphorus adsorption medium.

[0015] Preferably, in step (1), the mass ratio of straw, montmorillonite, and lanthanum nitrate pentahydrate is 30-50:15-25:5-10; the hydrothermal reaction temperature is 200-300°C.

[0016] Preferably, in step (2), the mass ratio of composite biochar and mercaptopropyltrimethoxysilane is 30-50:1-5.

[0017] Preferably, in step (3), the mass ratio of mercaptobiochar and guar hydroxypropyltrimethyl ammonium chloride is 15-25:3-8, and the reaction temperature is 50-80°C.

[0018] Further preferably, the aquatic plant community unit comprises a slope support and a support net, and emerging plants are planted on the bank on both sides of the aquatic plant community unit, and submerged plants are planted at the bottom of the aquatic plant community unit; the slope support is located on the ditch, and the support net is arranged on the slope support; the emerging plants are mixed with multiple species selected from the group consisting of water celery, water dropwort, Bermuda, Manila, tall fescue, and Yulong grass.

[0019] Preferably, the interception conversion pool is sequentially provided with a water collecting area, an adsorption interception area and a water storage and drainage area along the water flow direction.

[0020] Preferably, the pebble fence is arranged at the end of the ditch.

[0021] Preferably, the pebble fence is arranged at the end of the ditch.

[0022] Compared with the prior art, the application has the advantages and beneficial effects:

[0023] 1. The application fully excavates and enhances the ecological potential of the farmland without interfering with the normal production of the farmland, and makes the farmland into an effective assimilation center of environmental nitrogen and phosphorus. Through this innovative approach, we aim to purify the farmland drainage water quality and comprehensively improve the ecological environment of the farmland. In the face of the challenges of insufficient farmland ecological system function and limited ditch purification capacity, the present application optimizes and upgrades the "field-ridge-ditch-pool-road" system, which not only enriches the biodiversity and ecological buffer capacity of the farmland, but also improves the beautification effect and economic value of the field ridge.

[0024] 2. The application particularly focuses on improving the environmental landscape effect and self-purification capacity of the water body to meet the needs of beautiful countryside construction. By constructing a green ecological corridor, new vitality is injected into the sustainable development of agriculture, and the harmonious coexistence of agricultural production and ecological environment protection is realized.

[0025] 3. The application can realize efficient chemical adsorption removal of phosphorus by adding special phosphorus adsorption medium in the nitrification-denitrification-phosphorus removal treatment device, thereby improving the nitrogen and phosphorus pollutant interception capacity of the ecological type rural ditch nitrogen and phosphorus interception system in farmland drainage. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other related drawings can also be obtained without creative labor.

[0027] Figure 1 It is a structural schematic diagram of the ecological type rural ditch nitrogen and phosphorus interception system of the application.

[0028] Figure 2 It is a plan schematic diagram of the ecological type rural ditch nitrogen and phosphorus interception system of the application.

[0029] Figure 3 It is a sectional view of the aquatic plant community unit 1-1 of the application.

[0030] Figure 4 A cross-sectional view of the trapping and converting pool 2-2 of the present application;

[0031] Figure 5 A cross-sectional view of the pebble fence 3-3 of the present application.

[0032] The figure legend: 1 - ditch; 11 - first ditch bottom; 12 - second ditch bottom; 13 - third ditch bottom; 14 - revetment; 2 - sediment buffer zone; 21 - slope drop-off area; 22 - buffer flow regulating wall; 23 - through-flow hole; 3 - purification unit; 31 - nitrification-denitrification-phosphorus removal treatment device; 32 - aquatic plant community unit; 321 - emerging plant; 322 - slope support; 323 - support net; 324 - submerged plant; 4 - trapping and converting pool; 41 - water collecting area; 42 - adsorption interception area; 421 - carbon-based filler wall; 43 - water storage and drainage area; 5 - pebble fence; 51 - pebble belt. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased in the market. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that the combination of the technical solutions can be realized by the ordinary skilled in the art. When the combination of the technical solutions appears to be contradictory or unachievable, it should be considered that the combination of the technical solutions does not exist and is not within the protection scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by the ordinary skilled in the art without making creative efforts are within the protection scope of the present application.

[0034] The technical solutions of the present application will be further described in detail below in combination with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present application and not used to limit the present application.

[0035] In view of the technical problems in the prior art that the ecological ditch has low removal efficiency of nitrogen and phosphorus pollutants, and there is secondary pollution and the ecological function is not fully utilized, the present application provides an ecological type rural ditch nitrogen and phosphorus trapping system and method, which refers to Figures 1-5 , Figure 1 A structural schematic diagram of the ecological type rural ditch nitrogen and phosphorus trapping system of the present application; Figure 2 A plan schematic diagram of the ecological type rural ditch nitrogen and phosphorus trapping system of the present application; Figure 3 A cross-sectional view of the aquatic plant community unit 1-1 of the present application; Figure 4 A cross-sectional view of the trapping and converting pool 2-2 of the present application;

[0036] A cross-sectional view of the trapping and converting pool 2-2 of the present application;Figure 5 This is a cross-sectional view of the pebble fence 3-3 of the present invention. The following will describe in detail the ecological rural ditch nitrogen and phosphorus interception system and method with reference to the accompanying drawings.

[0037] Example 1

[0038] like Figure 1 and Figure 3 As shown, an ecological rural ditch nitrogen and phosphorus interception system includes a ditch 1 set along the water flow direction. The ditch 1 includes a first ditch bottom 11, a second ditch bottom 12, a third ditch bottom 13, and revetments 14 on both sides. A sediment buffer zone 2, a purification unit 3, an interception and conversion pond 4, and a pebble fence 5 are sequentially connected to the ditch 1. After preliminary treatment and sedimentation in the sediment buffer zone 2, farmland drainage enters the purification unit 3 for further treatment to remove nitrogen and phosphorus pollutants from the water. Then, it flows through the interception and conversion pond 4 for deep treatment to reduce the nitrogen and phosphorus content in the water. Finally, it flows through the pebble fence 5 to achieve the final interception and removal of nitrogen and phosphorus pollutants.

[0039] To address the shortcomings of existing technologies in farmland ecosystem function and the limited interception and purification capacity of ditches, this invention proposes an eco-friendly rural ditch nitrogen and phosphorus interception technology. By setting up a sediment buffer zone 2, water flow can be initially treated, sediment can be deposited, and the load of solid particles and pollutants in the water can be effectively reduced. By setting up a purification unit 3, nitrogen and phosphorus pollutants in the water are further removed through the synergistic effect of microorganisms and plants. By setting up an interception and conversion pond 4, farmland drainage is further treated to reduce nitrogen and phosphorus content in the water. By setting up a pebble fence 5, unsedimented or untreated nitrogen and phosphorus pollutants are further removed, ensuring the quality of the water before it flows out. This invention enhances the ecological function of ditches by optimizing their design and ecological structure, and achieves efficient interception and purification of nitrogen, phosphorus, and other pollutants in farmland drainage through multi-level nitrogen and phosphorus removal.

[0040] The sediment buffer zone 2 includes a sloping drainage area 21, a buffer flow regulating wall 22, and flow passage holes 23. The sloping drainage area 21 is located at the front end of the ditch 1 and connected to the first ditch bottom 11. The buffer flow regulating wall 22 is fixed on the first ditch bottom 11 and can effectively slow down the water flow speed and promote sediment settling. The buffer flow regulating wall 22 is provided with multiple flow passage holes 23. The pore density of the flow passage holes 23 decreases from top to bottom, which is used for fine control of water flow. The sediment buffer zone 2 is also planted with submerged plants 324. The submerged plants 324 are a mixture of various species such as Hydrilla verticillata, Vallisneria natans, Potamogeton crispus, and Ceratophyllum demersum.

[0041] Further preferably, the buffer flow regulating wall 22 has a thickness of 20-30 cm and a height of one-half to three-fourths of the height from the first ditch bottom 11 to the top of the ditch, and the number of walls is ≥1, to ensure sufficient strength and effective flow regulation, and multiple walls can form multiple levels of filtration, increasing the treatment area and improving the sedimentation effect, to ensure effective flow regulation.

[0042] Preferably, the purification unit 3 comprises a nitrification-denitrification-dephosphorization treatment device 31 and an aquatic plant community unit 32, the nitrification-denitrification-dephosphorization treatment device 31 is installed on the second ditch bottom 12 and used for removing nitrogen and phosphorus pollutants, and the aquatic plant community unit 32 is located downstream of the nitrification-denitrification-dephosphorization treatment device 31.

[0043] The combination of the nitrification-denitrification-dephosphorization treatment device 31 and the aquatic plant community unit 32 not only greatly improves the removal efficiency of nitrogen and phosphorus, but also promotes the overall stability and biodiversity of the ecosystem, providing an effective solution for water quality protection and improvement.

[0044] Further preferably, the nitrification-denitrification-dephosphorization treatment device 31 is provided with a water inlet and a water outlet, the water inlet is arranged at the joint with the sediment buffer area 2 and is flush with the second ditch bottom 12, the water outlet is arranged at the joint with the aquatic plant community unit 32 and is flush with the second ditch bottom 12, and the nitrification-denitrification-dephosphorization treatment device 31 is sequentially provided with a plant growth bag module, an iron-manganese composite oxidation film module, a denitrification module, and a phosphorus adsorption medium module, to achieve multi-level removal of pollutants.

[0045] Preferably, the plant growth bag module is composed of ecological concrete, gravel, and emergent landscape plants placed in ecological bags. The emergent landscape plants absorb organic matter and nutrient salts in farmland drainage as nutrients, and the plant roots release oxygen to make the surrounding microenvironment present in an order of aerobic-anoxic-anaerobic, to remove part of nitrogen and phosphorus pollutants through nitrification-denitrification and microbial excessive accumulation of phosphorus. The emergent landscape plants are one or more mixed species selected from the group consisting of reed, cattail, water onion, lotus, water lily, water celery, and water fern.

[0046] Preferably, the iron-manganese composite oxidation film module is composed of a plurality of hollow spheres with iron-manganese oxidation film attached thereon and gravel placed in ecological bags. The iron-manganese composite oxidation film has oxidation performance and adsorption capacity, and can catalyze and oxidize ammonia nitrogen in water, to further remove ammonia nitrogen. The adsorbed ammonia nitrogen is subsequently oxidized into nitrate and nitrite in water.

[0047] Preferably, the denitrification module is composed of multi-faceted hollow spheres and gravel, wherein the multi-faceted hollow spheres are attached or filled with denitrification substrate.

[0048] Preferably, the phosphorus adsorption medium module is composed of multi-faceted hollow spheres and gravel, wherein the multi-faceted hollow spheres are attached or filled with phosphorus adsorption medium.

[0049] Preferably, the preparation method of the phosphorus adsorption medium is as follows:

[0050] (1) The straw is naturally dried, cleaned of non-biological impurities, and then crushed to pass through a 60-mesh sieve; 80 g of the crushed and sieved straw and 40 g of montmorillonite are dispersed in 500 mL of water, 16 g of lanthanum nitrate pentahydrate is added, and after uniform mixing and stirring, a hydrothermal reaction is carried out at 250℃ for 20 h; after the reaction is completed, the temperature is cooled to room temperature, and after filtration, the solid is collected, washed with water until the filtrate is neutral, and dried to obtain a composite biochar;

[0051] (2) 80 g of the composite biochar is dispersed in 500 mL of 50wt% ethanol aqueous solution, 6.2 g of mercaptopropyl trimethoxysilane is added, and the mixture is stirred at room temperature for 3 h; after filtration, the solid is collected and dried to obtain a thiolated biochar;

[0052] (3) 60 g of the thiolated biochar is dispersed in 500 mL of water, 15 g of guar gum hydroxypropyltrimethyl ammonium chloride is added, and the pH value is adjusted to 3.5 with 1 mol / L hydrochloric acid; the mixture is heated at 60℃ for 5 h; after the reaction is completed, the temperature is cooled to room temperature, and the mixture is filtered, washed, dried, and ground to obtain a phosphorus adsorption medium.

[0053] The preparation of the phosphorus adsorption medium of the present application first involves a reaction of straw, montmorillonite, and lanthanum nitrate pentahydrate under hydrothermal conditions; the lanthanum nitrate can generate lanthanum oxide in situ in the montmorillonite and the biochar generated from the straw, which has the function of adsorbing organic phosphorus; compared with direct physical mixing, the lanthanum oxide has better distribution and better binding force in the composite biochar, which is conducive to improving the adsorption performance of the composite biochar for phosphorus; then the functional groups are activated under acidic conditions, and thiol groups are introduced onto the composite biochar to further improve the reactivity; through the reaction of the thiol groups with guar gum hydroxypropyltrimethyl ammonium chloride, the guar gum hydroxypropyltrimethyl ammonium chloride is grafted onto the surface of the composite biochar and is not easy to fall off; on the one hand, the hydrophilicity of the biochar is improved, and on the other hand, the positive charge of the guar gum hydroxypropyltrimethyl ammonium chloride can adsorb the negatively charged phosphate and organic phosphorus in water, further improving the interception effect of the phosphorus adsorption medium for phosphorus, and without causing secondary pollution.

[0054] By setting different modules, the nitrification-denitrification-phosphorus removal treatment device 31 can remove nitrogen, phosphorus and other pollutants in water in stages, improving the overall water quality purification effect. The plant growth bag module provides a good growing environment for aquatic plants, and the plant roots can further absorb nutrients in the water, promoting the self-purification function of the water body, while providing habitat for organisms and improving ecological diversity; the iron-manganese composite oxidation film can undergo oxidation-reduction reaction with harmful substances in the water, promoting the removal of pollutants, while providing a larger surface area for reaction to proceed, thereby improving the overall reaction efficiency; the denitrification module reduces nitrate to nitrogen, achieving nitrogen removal; and the phosphorus adsorption medium effectively removes phosphorus in the water body; The design of the water inlet and the water outlet flush with the bottom of the ditch can achieve a relatively stable flow, avoid the impact of severe fluctuations on the treatment effect, and make the water flow evenly distributed in the treatment device.

[0055] Further preferably, Figure 2 The 1-1 cross-sectional view of the aquatic plant community unit 32 in Figure 3 is shown, the aquatic plant community unit 32 includes slope support 322 and support net 323, and emerging plants 321 are planted on the two sides of the revetment 14 of the aquatic plant community unit 32, and submerged plants 324 are planted at the bottom of the aquatic plant community unit 32; the slope support 322 is located on the revetment 14, and the support net 323 is provided on the slope support 322, which provides a stable growth foundation for the emerging plants 321 through the support of the slope support 322 and the dense support net 323; the emerging plants 321 are mixed with multiple species of water celery, water dropwort, Bermuda, Manila, tall fescue, and Yulong grass.

[0056] Preferably, the bottom of the aquatic plant community unit 32 is higher than the second ditch bottom 12, so that the nitrification-denitrification-phosphorus removal treatment device 31 forms a "sedimentation tank" effect, which is beneficial to the sedimentation of suspended solids in the water, which can not only purify the water quality, but also prevent the emerging plants 321 from being damaged by silt covering.

[0057] Further preferably, the support net 323 is woven with environmentally friendly materials, and the support grid edge length is 20-30 cm, which provides stable support for the emerging plants 321.

[0058] Preferably, as shown in Figure 1 , the interception conversion tank 4 is provided with a water inlet, a water collection area 41, an adsorption interception area 42, a water storage and drainage area 43, and a water outlet in sequence along the water flow direction; the water inlet is provided at the joint of the interception conversion tank 4 and the purification unit 3 and flushes with the third ditch bottom 13; the water outlet is provided at the tail end of the interception conversion tank 4 and flushes with the third ditch bottom 13; the water collection area 41, the adsorption interception area 42, and the water storage and drainage area 43 are sequentially provided between the water inlet and the water outlet.

[0059] In order to further remove nitrogen and phosphorus pollutants in farmland drainage, a retention conversion tank 4 is arranged in the ecological rural ditch nitrogen and phosphorus interception system, wherein the water collecting area 41 can accumulate a large amount of water, adjust the water flow speed, reduce the flood peak flow, and avoid the erosion and damage of the purification unit 3; the adsorption interception area 42 can effectively adsorb the pollutants in the water, reduce water pollution, and improve the water quality; the water storage and drainage area 43 can make the heavier solid particles precipitate, to a certain extent, separate the solid substances in the water, and further purify the water; and the water inlet and outlet flush with the bottom of the ditch can ensure the smooth entry and discharge of the water flow.

[0060] Further preferably, the volume of the retention conversion tank 4 is 1.5-3 cubic meters; the retention conversion tank 4 with the volume range can promote the deceleration of the water flow, increase the precipitation time, improve the precipitation efficiency of the suspended matter and sediment in the water, and improve the water treatment effect.

[0061] More preferably, the third ditch bottom 13 is lower than the bottom of the aquatic plant community unit 32, which can improve the working efficiency of the retention conversion tank 4, is conducive to the effective flow of the water flow by using the gravity of the water flow itself, and promotes the settlement and adsorption of the pollutants.

[0062] Further preferably, the adsorption interception area 42 is provided with a carbon-based filler wall 421; the carbon-based filler has good adsorption performance, can effectively remove organic matter, heavy metals and other pollutants in the water, and can promote the growth of aerobic and anaerobic microorganisms, thereby enhancing the nitrogen and phosphorus interception effect in the water.

[0063] Further preferably, the carbon-based filler wall 421 is designed as a porous frame and a sponge layer, the porous frame structure and the sponge design enhance the stability and pressure resistance of the overall structure, can effectively retain the water flow, and the pollutants have enough time to be adsorbed and degraded during the flow process.

[0064] More preferably, the thickness of the carbon-based filler wall 421 is 40-60 cm, and the top is higher than the bottom of the ditch to ensure sufficient contact and removal of the pollutants.

[0065] More preferably, Figure 2 The 2-2 sectional view of the retention conversion tank 4 in Figure 4 is shown in

[0066] Preferably, according to the 3-3 sectional view of the pebble fence 5 in Figure 2 Figure 5 The bottom of the pebble fence 5 is provided with a pebble belt 51 and planted with emerging plants 321 and submerged plants 324, which not only enhances the ecological function, but also adds beauty to the rural landscape.​

[0067] Preferably, the width of the pebble belt 51 is 0.3-0.5 meters, the pebbles with a particle size of 3-10 cm are laid, and a slope of 3-10% is maintained to enhance the self-purification ability of the water flow.

[0068] Example 2

[0069] A water purification method using the above-mentioned ecological rural ditch nitrogen and phosphorus interception system, the specific steps are as follows:

[0070] The farmland drainage first passes through the sediment buffer zone 2, uses the slope falling water area 21 and the buffer flow adjusting wall 22 to slow down the flow rate, promotes the sediment settlement, and carries out preliminary purification of the drainage through the through-flow hole 23 arranged on the buffer flow adjusting wall 22 and the submerged plants 324; then the drainage enters the purification unit 3, the biological and chemical removal of nitrogen and phosphorus pollutants is carried out through the plant growth bag module, the iron and manganese composite oxidation film module, the denitrification module and the phosphorus adsorption medium module in the nitrification-denitrification-phosphorus removal treatment device 31, and the nitrogen and phosphorus pollutants in the water body are absorbed by the emerging plants 321 and the submerged plants 324 in the aquatic plant community unit 32; the treated water flow enters the interception conversion tank 4 again, the adsorption settlement is carried out through the carbon-based filler wall 421, and further removal of the pollutants is realized; the clean water flow leaves the interception conversion tank 4 and continues to flow to the pebble fence 5, and the nitrogen and phosphorus pollutants are finally removed by the emerging plants 321 and the submerged plants 324.

[0071] Comparative Example 1

[0072] An ecological rural ditch nitrogen and phosphorus interception system, similar to Example 1, the difference lies in that the phosphorus adsorption medium used is a composite biochar reacted with guar hydroxypropyltrimethyl ammonium chloride, and the specific preparation method is as follows:

[0073] (1) The straw is naturally dried, the non-biological impurities are cleaned, and then it is crushed to pass through a 60-mesh sieve; 80 g of the crushed and sieved straw and 40 g of montmorillonite are dispersed in 500 mL of water, 16 g of lanthanum nitrate pentahydrate is added, and after uniform mixing and stirring, a hydrothermal reaction is carried out at 250°C for 20 h; after the reaction is completed, it is cooled to room temperature, filtered, immersed in 500 mL of 15wt% dilute sulfuric acid for 8 h, filtered, and the solid is collected; after washing with water until the filtrate is neutral, drying is carried out to obtain the composite biochar;

[0074] (2) 60 g of the composite biochar is dispersed in 500 mL of water, 15 g of guar hydroxypropyltrimethyl ammonium chloride is added, the pH value is adjusted to 3.5 with 1 mol / L hydrochloric acid, and a heating reaction is carried out at 60°C for 5 h; after the reaction is completed, it is cooled to room temperature, filtered, washed, dried, and ground to obtain the phosphorus adsorption medium.

[0075] Comparative Example 2

[0076] An ecological rural ditch nitrogen and phosphorus interception system, similar to Example 1, is disclosed, except that the phosphorus adsorbent medium used is composite biochar, and its preparation method is as follows:

[0077] Straw was air-dried naturally, and non-biological impurities were removed. Then, it was crushed and passed through a 60-mesh sieve. 80g of crushed and sieved straw and 40g of montmorillonite were dispersed in 500mL of water, and 16g of lanthanum nitrate pentahydrate was added. After mixing and stirring evenly, a hydrothermal reaction was carried out at 250℃ for 20h. After the reaction was completed, it was cooled to room temperature, filtered, and then soaked in 500mL of 15wt% dilute sulfuric acid for 8h. After filtration, the solid was collected, washed with water until the filtrate was neutral, and dried to obtain composite biochar.

[0078] Test case

[0079] 10 g of each of the phosphorus adsorption media prepared in Example 1, Comparative Example 1, and Comparative Example 2 were added to 50 mL of a phosphorus standard solution (pH = 5.8) with a phosphorus elemental concentration of 10 mg / L. The solutions were then shaken at 25 °C for 4 h at a shaking frequency of 140 r / min. The phosphorus removal rate was calculated, and the experimental results are shown in Table 1.

[0080] Table 1. Test results of phosphorus removal rate of phosphorus adsorption medium

[0081] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A nitrogen and phosphorus interception system for rural ditches, comprising ditches (1) arranged along the direction of water flow, characterized in that: The ditch (1) includes a first ditch bottom (11), a second ditch bottom (12), a third ditch bottom (13), and revetments (14) on both sides. A sediment buffer zone (2), a purification unit (3), an interception and conversion pond (4), and a pebble fence (5) are sequentially connected to the ditch (1). After the farmland drainage undergoes preliminary treatment and sedimentation in the sediment buffer zone (2), it enters the purification unit (3) to remove nitrogen and phosphorus pollutants from the water. Then, it flows through the interception and conversion pond (4) for further treatment to reduce the nitrogen and phosphorus content in the water. Finally, it flows through the pebble fence (5) to achieve the final interception and removal of nitrogen and phosphorus pollutants. The purification unit (3) includes a nitrification-denitrification-phosphorus removal treatment device (31) and an aquatic plant community unit (32); The nitrification-denitrification-phosphorus removal device (31) is sequentially equipped with a plant growth bag module, an iron-manganese composite oxide film module, a denitrification module, and a phosphorus adsorption medium module; The phosphorus adsorption medium module is provided with a phosphorus adsorption medium, and the preparation method of the phosphorus adsorption medium is as follows: (1) The straw is air-dried naturally, non-biological impurities are removed, and then it is crushed and passed through a 40-80 mesh sieve; the crushed and sieved straw and montmorillonite are dispersed in water, lanthanum nitrate pentahydrate is added, and after mixing and stirring evenly, a hydrothermal reaction is carried out. After the reaction is completed, it is cooled to room temperature, filtered, and then impregnated in dilute sulfuric acid to obtain composite biochar. (2) Disperse the composite biochar in an aqueous ethanol solution, add mercaptopropyltrimethoxysilane, stir and react at room temperature for 2-4 h, filter, and dry to obtain mercaptoized biochar; (3) Disperse the thiolized biochar in water, add guar hydroxypropyltrimethylammonium chloride, adjust the pH to 3-4 with dilute hydrochloric acid, heat the reaction for 4-6 hours, cool to room temperature after the reaction is completed, filter, wash, dry and grind to obtain phosphorus adsorption medium.

2. The interception system according to claim 1, characterized in that: The sediment buffer zone (2) includes a slope drainage area (21), a buffer flow regulating wall (22), and flow passage holes (23). The slope drainage area (21) is located at the front end of the ditch (1) and connected to the bottom of the first ditch (11). The buffer flow regulating wall (22) is fixed on the bottom of the first ditch (11). The buffer flow regulating wall (22) is provided with multiple flow passage holes (23).

3. The interception system according to claim 1, characterized in that: The nitrification-denitrification-phosphorus removal treatment device (31) is installed on the bottom of the second ditch (12); the aquatic plant community unit (32) is located downstream of the nitrification-denitrification-phosphorus removal treatment device (31).

4. The interception system according to claim 3, characterized in that: The aquatic plant community unit (32) includes a slope protection support (322) and a support net (323), and new plants (321) are planted on the bank protection (14) on both sides of the aquatic plant community unit (32), and submerged plants (324) are planted at its bottom; the slope protection support (322) is located on the bank protection (14), and a support net (323) is set on the slope protection support (322); the new plants (321) are a mixture of various species among water celery, watercress, Bermuda grass, Manila grass, tall fescue, and gypsum.

5. The interception system according to claim 1, characterized in that: The interception and conversion pool (4) is provided with a water collection area (41), an adsorption and interception area (42), and a water storage and drainage area (43) in sequence along the water flow direction.

6. The interception system according to claim 5, characterized in that: The adsorption interception zone (42) is provided with a carbon-based filler wall (421).

7. The interception system according to claim 1, characterized in that: The pebble fence (5) is arranged along the end of the ditch (1).

8. The interception system according to claim 7, characterized in that: The bottom of the pebble fence (5) is provided with a pebble strip (51) and planted with emerging plants (321) and submerged plants (324).

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