A method for direct ammonia oxidation denitrification suitable for ecological ditch of slope farmland

Abstract

The present application relates to the technical field of agricultural non-point source pollution treatment, and specifically discloses a method for ammonia direct oxidation denitrification suitable for ecological ditch of slope farmland. The method arranges one or more AMAO reaction units along the longitudinal slope of the ditch in the ecological ditch system. In the AMAO reaction unit, based on the microbial acetone-mediated ammonia oxidation (AMAO, acetone + ammonia -> acetone oxime -> acetone + nitrogen) pathway, AMAO functional flora is used to directly convert ammonia nitrogen into nitrogen in the ecological ditch system. The system uses widely distributed AMAO functional microorganisms to directly convert ammonia nitrogen into nitrogen in a single reaction unit, breaking through the limitations of the traditional nitrification-denitrification path. Through the modular ladder-type drop structure, composite functional filler layer and precise microenvironment regulation, the present application realizes efficient and stable removal of ammonia nitrogen in slope farmland drainage under low energy consumption and low cost conditions, and provides a new technical paradigm for solving the problem of nitrogen pollution in slope farmland.

Description

Technical Field

[0001] This invention belongs to the field of agricultural non-point source pollution control and ecological environment protection technology, specifically relating to a direct ammonia oxidation denitrification method suitable for ecological ditches on sloping farmland. Background Technology

[0002] In the upper reaches of the Yangtze River and other areas with complex terrain, steep slopes, and fragmented plots of sloping farmland, agricultural production heavily relies on fertilizer application, leading to severe exceedances of ammonia nitrogen concentrations in farmland runoff. This region experiences concentrated and intense rainfall, and the steep terrain of sloping farmland results in rapid drainage flow and strong hydraulic scouring. Traditional ecological ditches have short hydraulic retention times, leading to low ammonia nitrogen removal efficiency and even problems such as ditch destruction and accelerated soil erosion. Ammonia nitrogen, as a major form of nitrogen from agricultural non-point source pollution, easily causes eutrophication when directly discharged into water bodies, making it a crucial factor in controlling agricultural non-point source pollution.

[0003] Currently, the mainstream technology for removing ammonia nitrogen from ecological ditches on sloping farmland is the circuitous "nitrification-denitrification" process (ammonia → nitrite → nitrate → nitrite → nitrogen). This process typically requires completion in two separate physical spaces or time periods, one aerobic and the other anaerobic, resulting in a long process, large land area, and high energy consumption. In the context of sloping farmland, this multi-step process is difficult to implement effectively within the limited space of ditches. Furthermore, the denitrification process requires additional carbon sources, increasing operating costs and management complexity. In recent years, significant progress has been made in fundamental research on the nitrogen cycle, revealing and confirming for the first time a novel microbial pathway hidden in nature that can directly oxidize ammonia to nitrogen—acetone-mediated ammonia oxidation (AMAO, acetone + ammonia → acetone oxime → acetone + nitrogen). This discovery not only breaks through the traditional nitrogen cycle understanding framework of the past century but also provides a completely new theoretical basis and technological weapon for solving the nitrogen removal problem on sloping farmland. AMAO functional microorganisms are widely distributed in natural ecosystems and are mostly dominant bacteria in the environment. They involve the vast majority of bacterial phyla, including common Proteobacteria, Bacteroidetes, Firmicutes, Acidobacteria, Actinobacteria, etc., which makes in situ enrichment of AMAO bacteria feasible.

[0004] Combining the AMAO pathway with ecological ditch engineering on sloping farmland can overcome the limitations of traditional methods, achieving one-step ammonia nitrogen removal, significantly shortening the path, reducing energy consumption, and improving adaptability. However, there is currently no engineering application scheme for AMAO specifically designed for the unique hydraulic conditions of sloping farmland (steep slopes, rapid flow, intermittent drainage). Traditional ditches lack structural optimization for AMAO, resulting in insufficient utilization of AMAO activity. Existing technologies struggle to achieve efficient and stable nitrogen removal under low-cost, low-energy conditions, necessitating an innovative ditch structure that couples the AMAO pathway to solve the challenge of ammonia nitrogen pollution control on sloping farmland. Summary of the Invention

[0005] In view of this, the purpose of this invention is to solve the above problems and provide a direct ammonia oxidation denitrification method suitable for ecological ditches on sloping farmland.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A direct ammonia oxidation denitrification method suitable for ecological ditches on sloping farmland is proposed. One or more AMAO reaction units are arranged in a stepped manner along the longitudinal slope of the ecological ditch system. In the AMAO reaction units, based on the microbial acetone-mediated ammonia oxidation pathway, the AMAO functional bacteria directly convert ammonia nitrogen into nitrogen gas in the ecological ditch system.

[0007] Furthermore, the AMAO reaction unit includes an inlet buffer zone, an AMAO main reaction zone, and an outlet flow stabilization zone arranged sequentially along the water flow direction; The inlet buffer zone is used for homogenization and initial rate reduction; the AMAO main reaction zone contains a composite functional packing layer with a layered structure, the upper layer being an immobilized carrier loaded with AMAO functional microorganisms; the effluent stabilization zone is used for energy dissipation and stabilizing the effluent flow.

[0008] Furthermore, the AMAO main reaction zone utilizes O2 and NO2. - NO3 - It can act as an electron acceptor for any one or more of Fe(III), thereby maintaining denitrification activity in aerobic, hypoxic or microaerobic environments.

[0009] Furthermore, the bottom layer of the composite functional filler layer is a composite material layer, which is a mixture of iron hydroxide, sulfur and limestone in a mass ratio of 3:3:1, used to activate AMAO functional bacteria and provide potential electron acceptors.

[0010] Furthermore, the inlet buffer zone, AMAO main reaction zone, and outlet flow stabilization zone are arranged in a stepped manner, utilizing the falling and impacting water flow to achieve natural reoxygenation and provide electron acceptors for the acetone-mediated ammonia oxidation pathway of microorganisms.

[0011] Furthermore, the immobilization carrier is polyvinyl alcohol-calcium alginate microspheres.

[0012] Furthermore, the upper layer of the composite functional filler layer is formed by mixing the immobilized carrier and the original soil volume ratio at 1:(2~3) and filling it to a thickness of 0.3~0.5m, and forms an active infiltration layer in the AMAO main reaction zone to ensure permeability and biofilm adhesion.

[0013] Furthermore, before the ecological ditch system is started, acetone stimulates the growth of AMAO bacteria in the AMAO main reaction zone, enriching microorganisms with AMAO function in situ. After the biofilm on the immobilized carrier is formed and the ammonia nitrogen effluent is stable, the entire system is started. After entering the stable period, there is no need to add acetone. During the reaction process, the microorganisms convert organic carbon in the water into acetone and achieve recycling.

[0014] Furthermore, before the ecological ditch system is started, 10~100mg / L of acetone is added to the AMAO main reaction zone to stimulate the growth of AMAO bacteria.

[0015] Furthermore, the AMAO reaction unit is suitable for ditches with a longitudinal slope greater than 5%, and each step constitutes an independent AMAO reaction module.

[0016] The beneficial effects of this invention are as follows: 1. Revolutionary improvement in nitrogen removal efficiency: The AMAO one-step method of this invention significantly shortens the steps of converting ammonia nitrogen into nitrogen gas, breaking through the limitations of the traditional nitrification-denitrification pathway, and the total nitrogen removal rate is expected to increase from about 60% to more than 90%.

[0017] 2. Reduced energy consumption and cost: Due to the shortened path, oxygen consumption can theoretically be reduced by about 50%, and no external denitrification carbon source is required. The overall operating cost is expected to be reduced by 40% to 60%.

[0018] 3. Excellent environmental friendliness: The method in this invention does not accumulate intermediate harmful nitrogen oxides, significantly reducing the emission risk of the strong greenhouse gas N2O.

[0019] 4. Excellent adaptability to slopes: The AMAO reaction unit in this invention adopts a modular design and stepped structure to perfectly adapt to steep slopes, solving the contradiction between fast flow rate and long residence time.

[0020] 5. Strong technical applicability: The AMAO functional microorganisms used in this invention are widely distributed in nature, far exceeding any known ammonia-oxidizing bacteria, making the system easy to quickly establish and operate stably on sloping farmland in different regions.

[0021] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a top view of the ecological ditch system in this invention.

[0023] Figure 2 This is a side sectional view of the ecological ditch system in this invention.

[0024] Figure 3 A cross-sectional view of the AMAO reaction unit in this invention.

[0025] Figure 4 This is a graph showing the change in ammonia nitrogen concentration in the influent and effluent in an embodiment of the present invention.

[0026] Attached diagram labels: 1-Farmland planting area; 2-Inlet buffer zone; 3-AMAO main reaction zone; 4-Outlet flow stabilization zone. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0028] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0029] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0030] Example 1 like Figures 1-3As shown, this embodiment provides a direct ammonia oxidation denitrification method suitable for ecological ditches on sloping farmland. An AMAO reaction unit is arranged in a stepped manner along the longitudinal slope of the ditch in the ecological ditch system. In the AMAO reaction unit, based on the microbial acetone-mediated ammonia oxidation pathway, the AMAO functional bacteria directly convert ammonia nitrogen into nitrogen gas in the ecological ditch system.

[0031] The ecological ditch system comprises a farmland planting area 1, an inlet buffer zone 2, an AMAO main reaction zone 3, and an outlet flow stabilization zone 4. Drainage from the farmland planting area 1 enters the ditch system, first flowing through the inlet buffer zone 2, which has an enlarged cross-section structure to homogenize the flow and initially reduce the water velocity; then it enters the AMAO main reaction zone 3, which utilizes O2 and NO2. - NO3 - It can use any one or more of Fe(III) as electron acceptors, thus maintaining denitrification activity in aerobic, hypoxic, or microaerobic environments. A composite functional packing layer is placed in the AMAO main reaction zone 3. This composite functional packing layer adopts a layered structure: the bottom layer is a mixture of iron hydroxide, sulfur, and limestone in a mass ratio of 3:3:1, which is used to activate AMAO functional bacteria and provide potential electron acceptors; the upper layer is an immobilized polyvinyl alcohol-calcium alginate microsphere loaded with AMAO functional microorganisms, which is mixed with the original volume of soil at a ratio of 1:(2~3) and then filled to form an active infiltration layer with a thickness of 0.3~0.5m to ensure water permeability and biofilm adhesion; finally, it enters the effluent stabilization zone 4, which is used to dissipate energy and stabilize the effluent flow.

[0032] Among them, the inlet buffer zone 2, AMAO main reaction zone 3, and outlet flow stabilization zone 4 in the AMAO reaction unit are arranged in a stepped manner, and the natural longitudinal slope of the ditch (slope greater than 5%) is used to form a waterfall structure, and the falling and impact of the water flow achieves natural reoxygenation.

[0033] Before system startup, 10-100 mg / L of acetone is added to the AMAO main reaction zone 3 to stimulate the growth of AMAO functional bacteria, thereby enriching microorganisms with acetone-mediated ammonia oxidation function in situ. After 7-14 days of enrichment, a mature biofilm forms on the immobilized carrier, and the entire system is started after the ammonia nitrogen effluent stabilizes. Once the system enters a stable operating period, no further acetone addition is required. During the reaction, the microorganisms convert organic carbon in the ditch water into acetone, achieving acetone media recycling.

[0034] For specific implementation, please refer to Figure 4 An ecological ditch on a sloping farmland was selected as the test object. The influent ammonia nitrogen concentration ranged from 5 to 15 mg / L. After treatment by the method in this embodiment, the ammonia nitrogen removal rate reached more than 90% during the monitoring period, and the total nitrogen removal rate was significantly improved.

[0035] Example 2 This embodiment adds multiple AMAO reaction units arranged in a stepped manner based on the length and slope of the ditch, according to the previous embodiment 1. Each AMAO reaction unit forms an independent AMAO reaction module, thereby treating ammonia nitrogen more efficiently.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for direct ammonia oxidation denitrification suitable for ecological ditches on sloping farmland, characterized in that, In the ecological ditch system, one or more AMAO reaction units are arranged in a stepped manner along the longitudinal slope of the ditch. In the AMAO reaction unit, based on the microbial acetone-mediated ammonia oxidation pathway, the AMAO functional bacteria directly convert ammonia nitrogen into nitrogen gas in the ecological ditch system. The AMAO reaction unit includes an inlet buffer zone, an AMAO main reaction zone, and an outlet flow stabilization zone arranged sequentially along the water flow direction. The inlet buffer zone is used for homogenization and initial rate reduction; the AMAO main reaction zone contains a composite functional packing layer with a layered structure, the upper layer being an immobilized carrier loaded with AMAO functional microorganisms; the effluent stabilization zone is used for energy dissipation and stabilizing the effluent flow. The AMAO main reaction zone utilizes O2 and NO2. - NO3 - Or any one or more of Fe(III) can act as electron acceptors, thereby maintaining denitrification activity in aerobic, hypoxic or microaerobic environments; The bottom layer of the composite functional filler layer is a composite material layer, which is a mixture of iron hydroxide, sulfur and limestone in a mass ratio of 3:3:1, used to activate AMAO functional bacteria and provide potential electron acceptors. The inlet buffer zone, AMAO main reaction zone, and outlet flow stabilization zone are arranged in a stepped manner, utilizing the falling and impacting of water flow to achieve natural reoxygenation and provide electron acceptors for the acetone-mediated ammonia oxidation pathway of microorganisms. The immobilized carrier is polyvinyl alcohol-calcium alginate microspheres; the upper layer of the composite functional filler layer is formed by mixing the immobilized carrier and the original volume of soil at a ratio of 1:(2~3) and filling it to a thickness of 0.3~0.5m, and forming an active infiltration layer in the AMAO main reaction zone to ensure permeability and biofilm adhesion.

2. The method according to claim 1, characterized in that, Before the ecological ditch system is started, acetone stimulates the growth of AMAO bacteria in the AMAO main reaction zone, enriching microorganisms with AMAO function in situ. After the biofilm on the immobilized carrier is formed and the ammonia nitrogen effluent is stable, the entire system is started. After entering the stable period, there is no need to add acetone. During the reaction process, the microorganisms convert organic carbon in the water into acetone and achieve recycling.

3. The method according to claim 2, characterized in that, Before starting the ecological ditch system, add 10~100mg / L of acetone to the AMAO main reaction zone to stimulate the growth of AMAO bacteria.

4. The method according to claim 1, characterized in that, The AMAO reaction unit is suitable for ditches with a longitudinal slope greater than 5%, and each step constitutes an independent AMAO reaction module.

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