Fluid power response and biochemical partition induced floating island root purification device

Abstract

This invention discloses a floating island root purification device induced by hydrodynamic response and biochemical zoning, comprising a double-cylinder structure connected to the floating island for purifying the roots of floating island plants; the double-cylinder structure includes an inner cylinder, an outer cylinder, and an annular reaction chamber fitted over the roots of the floating island plants; the annular reaction chamber is equipped with a microbial system for denitrifying the roots of the floating island plants and providing a carbon source; the outer cylinder is provided with buffer spikes for mitigating water flow impact and facilitating the transport of substances by the microbial system; this invention, by organically combining structural zoning and microbial colonization, systematically solves the problems of easy loss, difficult colonization, and low efficiency of traditional floating island inoculants.

Description

Technical Field

[0001] This invention relates to the fields of environmental engineering and water pollution control technology, specifically to a floating island root purification device based on fluid dynamic response and biochemical zoning. Background Technology

[0002] Ecological floating island technology is a mature artificial ecosystem that purifies water through the absorption and degradation processes of plants and their root-attached microorganisms, and has been widely applied in various water environment management applications. To enhance specific functions such as nitrogen and phosphorus removal, existing technologies often introduce immobilized functional microorganisms through gel encapsulation. However, current practices have significant limitations: First, immobilized microbial agents are mostly added in dispersed form, making it difficult to efficiently and stably colonize the rhizosphere region of plants with the highest purification efficiency, resulting in weak synergistic effects between the microbial agents and the root system; second, the microbial agents are directly exposed to water, especially in flowing water, making them susceptible to erosion and inactivation, resulting in poor durability, and ineffective dispersed microbial agents are difficult to recover and replace, posing management difficulties and the risk of secondary pollution; if the microbial agents are placed in perforated boxes, they are prone to short-circuiting due to water flow, poor internal mass transfer (especially oxygen), and biofilm blockage, forming new "dead water zones" and "blocked boxes," causing the microbial agents to inactivate due to lack of oxygen and substrate.

[0003] To overcome the aforementioned shortcomings, there is an urgent need for an integrated technical solution that can actively and stably aggregate and maintain functional microorganisms in the rhizosphere region, resist water erosion, and facilitate maintenance. Existing improvements mostly focus on the microbial agent materials themselves, while there is still no mature and effective solution on how to actively regulate the rhizosphere microbial environment through system structure design and utilize environmental energy to achieve system self-sustainability. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a floating island root purification device based on hydrodynamic response and biochemical zoning.

[0005] A hydrodynamic response and biochemical zoning induced floating island root purification device, the floating island root purification device comprising: a double-cylinder structure connected to the floating island for purifying the roots of floating island plants; The double-cylinder structure includes an inner cylinder fitted into the root system of the floating island plants, an outer cylinder fitted into the inner cylinder, and an annular reaction chamber disposed between the inner cylinder and the outer cylinder; the inner cylinder and the outer cylinder are closed at both ends; The annular reaction chamber is filled with a microbial system; the microbial system includes an isolation mesh cylinder, a dense denitrifying bacteria gel carrier filled between the isolation mesh cylinder and the inner cylinder, and a large-particle-size porous nitrifying bacteria gel carrier filled between the isolation mesh cylinder and the outer cylinder. The inner wall of the inner cylinder is provided with multiple capillary guide tubes extending toward the center of the inner cylinder and used to transmit the secretions of the roots of the floating island plants outward through capillary action. The outer cylinder is provided with multiple through holes and buffer spikes for reducing the impact of water flow and facilitating the transport of substances within the microbial system. The buffer spike is hollow inside and has multiple first micropores on one side of its sidewall. The buffer spike has a partition tube inside, and the space between the partition tube and the inner wall of the buffer spike is filled with a slow-release carbon source filler. The separator tube is elliptical in shape. One end of the separator tube is located inside the buffer spikes, and a plurality of second micropores are provided on one side of the sidewall. The second micropores are arranged opposite to the first micropores. The other end of the separator tube is connected to the large-particle-size porous nitrifying bacteria gel carrier. One end of the capillary guide tube is located inside the inner cylinder, and the other end is located inside one end of the separator tube.

[0006] Explanation: The above-mentioned device, through its double-cylinder structure, constructs a spatially ordered and microenvironmentally adapted colonization carrier bed for nitrifying and denitrifying bacteria. The function of the microbial system is to denitrify the roots of floating island plants and provide a carbon source. It also uses capillary tubes to direct root exudates to the denitrification zone, thus physically solving the problems of difficult and easy loss of functional bacteria in the rhizosphere. Biochemically, it achieves the shortening and efficiency of the nitrogen removal path, forming an enhanced rhizosphere purification system that is erosion-resistant, self-sufficient, easy to maintain, and has significantly improved purification efficiency. Through the fluid dynamic design of the buffer spikes and elliptical partition tubes, it realizes water pressure-driven active carbon source addition and internal circulation without external power, transforming the negative factors of environmental water flow impact into positive energy for system operation.

[0007] Furthermore, the buffer spikes are blunt-tipped protrusions, streamlined wing-shaped structures, or cylindrical shapes.

[0008] Explanation: The blunt-nosed structure can form significant pressure accumulation on the water-facing surface during positive impact, forcing water to be injected through micropores; the streamlined airfoil can maintain stable fluid guidance and pressure conversion efficiency under different flow velocities and directions. Both enhance the device's ability to autonomously obtain driving energy from the environment, thereby ensuring the continuous and stable transmission of internal carbon sources and biochemical reactions.

[0009] Furthermore, the double-cylinder structure is installed on the floating material of the floating island via a suspension connector; the suspension connector is a connecting chain with a bayonet, hinge hook, or lifting ring.

[0010] Note: Standardized suspension connectors such as bayonet, hinge hooks, or rings are used, which allows the dual-cylinder purification module to be quickly and flexibly installed on various floating materials of floating islands.

[0011] Furthermore, the dense denitrifying bacteria gel carrier is a composite hydrogel microsphere with polyvinyl alcohol (PVA) and sodium alginate (SA) as the backbone, doped with a conductive medium and solid carbon source powder; the conductive medium is biochar powder or nano-ferric oxide, used to enhance electron transfer in the denitrification process; the solid carbon source powder is polycaprolactone (PCL) powder or polyhydroxybutyrate valerate (PHBV) powder, used to provide endogenous electron donors; its preparation components, by mass percentage, include: 8%~12% PVA, 1%~2% SA, 0.5%~1% conductive medium, 1%~3% solid carbon source powder, and the remainder is denitrifying bacteria suspension and water; the carrier microspheres have a dense surface skin structure with an oxygen diffusion coefficient of less than 10. -9 m 2 / s .

[0012] Explanation: The main advantage of adding a dense denitrifying bacteria gel carrier here is that it constructs a self-sustaining anoxic denitrification microreactor. The carrier's unique dense skin structure significantly increases the mass transfer resistance of oxygen. Even if the device is in an open water body or a high dissolved oxygen environment, the carrier can maintain a stable anoxic or anaerobic state, effectively preventing dissolved oxygen from inhibiting the activity of denitrifying enzymes such as nitrate reductase, thus ensuring high nitrogen removal performance. At the same time, the conductive media such as biochar integrated inside the carrier accelerates the direct electron transfer rate between microbial species. Combined with the internally sealed solid phase slow-release carbon source such as PCL, it can continuously provide electron donors for denitrifying bacteria even when the external influent carbon source is insufficient, solving the problem of low total nitrogen removal rate of traditional floating islands in water bodies with low carbon-to-nitrogen ratios.

[0013] Furthermore, the large-particle-size porous nitrifying bacteria gel carrier is a macroporous network structure hydrogel with polyvinyl alcohol (PVA) and chitosan (CS) as the backbone and coupled with an ammonia nitrogen adsorption material; the ammonia nitrogen adsorption material is modified zeolite powder, attapulgite clay, or cation exchange resin powder, used to form high-concentration micro-regions of ammonia nitrogen inside the carrier; a pore-forming agent (sodium bicarbonate) is added during its preparation process, and the average pore size of the carrier after molding is 50~200 micrometers, with a specific surface area greater than 500 m². 2 / g, containing a community of nitrifying bacteria.

[0014] Note: The main advantage of adding a large-particle-size porous nitrifying bacteria gel carrier here is that it achieves the dual functions of in-situ enrichment and efficient conversion of ammonia nitrogen and physical barrier. The coupled modified zeolite powder and other adsorbent materials can actively capture low concentrations of ammonia nitrogen in the water and lock them in the carrier pores, creating a microenvironment with a high local substrate concentration for the embedded nitrifying bacteria, which significantly improves the kinetic efficiency of the nitrification reaction. At the same time, its unique large-particle-size porous network structure not only provides a huge specific surface area for biological attachment to ensure high bacterial abundance, but also serves as a permeable filter on the outer layer of the device. While intercepting external suspended matter to prevent internal blockage, it effectively buffers water flow erosion and protects the structural integrity and operational stability of the internal biochemical zone.

[0015] Furthermore, the ratio of the filling volume of the dense denitrifying bacteria gel carrier to the filling volume of the large-particle porous nitrifying bacteria gel carrier is 1:1.3 to 1:1.6. This volume ratio is achieved by adjusting the radial position of the isolation mesh cylinder, ensuring that the outer aerobic interception zone has a hydraulic retention time (HRT) sufficient to match the specific growth rate of nitrifying bacteria, while the inner anoxic induction zone maintains a denitrification load matching the nitrification flux under carbon source enhancement conditions.

[0016] Explanation: The above-described device achieves an optimized match between nitrification and denitrification biochemical capacities within a limited space. It ensures that the outer nitrification zone has sufficient volume to complete efficient ammonia nitrogen oxidation, while also ensuring that the inner denitrification zone has the corresponding capacity to promptly process the generated nitrates. This improves the overall continuity and efficiency of nitrogen gradient conversion, while avoiding the problem of excessively large denitrification zones crowding out water flow channels or insufficient nitrification zones leading to ammonia nitrogen accumulation. This achieves synergistic optimization of system structure and purification function.

[0017] Furthermore, the elliptic parameter of the elliptical partition tube is related to the inner diameter of the buffer spike as follows: (1-1) (1-2) The ellipse parameters include the major axis of the ellipse. a minor axis of the ellipse b In equations (1-1) and (1-2), a The major axis of the ellipse This is a correction factor with a value range of 0.7 to 0.9. b The minor axis of the ellipse The inner diameter of the buffer thorn (8) is used for buffering.

[0018] Explanation: The above formula relates the ellipse parameters to the inner diameter of the buffer spike, achieving precise matching of structural parameters and performance optimization. This ensures that after the dynamic pressure conversion, the high-pressure fluid forms a high-speed, concentrated directional jet under the guidance of the elliptical tube, thereby stably and efficiently enhancing the Venturi suction effect and the final internal release disturbance. This makes the entire driving process not only feasible but also has predictable reliability and an optimizable performance foundation.

[0019] Furthermore, the area of ​​the second micropore satisfies: (1-3) In equation (1-3), These are empirical coefficients with values ​​ranging from 0.1 to 0.3. This refers to the area between the outer wall of the separator tube and the inner wall of the buffer spike. n For an exponent with a value range of 0.5 to 1 Explanation: The above formula, by formulating the area of ​​the second micropore, links key hydraulic properties with designable structural parameters; it ensures that the high pressure generated by the water flow impact can be stably and controllably converted into a jet, thereby reliably generating the Venturi effect to actively entrain root secretions and form a directional release flow with sufficient momentum to achieve precise nutrient replenishment and effective physical disturbance of the internal biological packing.

[0020] The slow-release carbon source filler is a porous polycaprolactone (PCL) / modified starch composite particle; it is made by melt blending and extrusion granulation of PCL and modified starch in a mass ratio of 7:3 to 6:4; the modified starch is corn starch that has been pre-treated with alkali gelatinization and cross-linking to regulate the carbon source release rate; the composite particle is prepared with a water-soluble pore-forming agent (sodium bicarbonate), and the pore-forming agent is dissolved by water washing after granulation, thereby forming interconnected micron-level dissolution channels inside the particle, which are used to continuously release small molecule organic carbon through convection-diffusion mechanism under the driving force of water flow stagnation pressure.

[0021] The beneficial effects of this invention are: This invention combines structural zoning and microbial colonization, systematically solving the problems of easy loss, difficult colonization, and low efficiency of traditional floating island microbial agents. Specifically, through a double-layer cylinder and a radial isolation mesh, an orderly aerobic-anoxic biochemical microenvironment is constructed in the rhizosphere region, achieving spatial fixation and precise adaptation of nitrifying and denitrifying functional bacteria. Furthermore, with the help of buffer spikes on the surface of the outer cylinder, the impact energy of water flow is actively captured and converted into internal driving pressure, realizing the directional transport and mixing of carbon sources and root exudates. Thus, under the condition of no external energy supply, the targeted enhancement of microbial agents, erosion stabilization, and continuous nutrient replenishment are completed simultaneously, forming a highly efficient, self-sustaining, and easy-to-maintain integrated rhizosphere purification unit. Attached Figure Description

[0022] Figure 1 This is a longitudinal section schematic diagram of the internal structure of an embodiment of the present invention; Figure 2 This is a top view of the internal structure of an embodiment of the present invention; Figure 3 This is a schematic diagram of the double-cylinder structure being hoisted onto the floating island in an embodiment of the present invention; Figure 4 This is a longitudinal cross-sectional schematic diagram of the internal structure of the buffer spikes in an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the working principle of the buffer spikes in an embodiment of the present invention; Among them, 1-inner cylinder, 2-dense denitrifying bacteria gel carrier, 3-large particle size porous nitrifying bacteria gel carrier, 4-isolation mesh cylinder, 5-outer cylinder, 6-annular reaction chamber, 7-capillary guide tube, 8-buffer spike, 9-through hole, 10-suspension connector, 11-floating island, 12-second micropore, 13-slow-release carbon source filler, 14-first micropore, 15-separator tube. Detailed Implementation

[0023] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0024] Example 1: A floating island root purification device induced by hydrodynamic response and biochemical zoning, the floating island root purification device comprising: a double-cylinder structure connected to the floating island for purifying the roots of floating island plants; like Figure 1 , Figure 2 , Figure 3 As shown, the double-cylinder structure includes an inner cylinder 1 fitted into the root system of the floating island plant, an outer cylinder 5 fitted into the inner cylinder 1, and an annular reaction chamber 6 disposed between the inner cylinder 1 and the outer cylinder 5; the inner cylinder 1 and the outer cylinder 5 are each closed at both ends by an annular plate. The double-cylinder structure is mounted on the floating material of the floating island 11 via a suspension connector 10; the suspension connector 10 is a connecting chain with a bayonet, hinge hook or ring; the floating material is a polymer material, such as high-density polyethylene, polyurethane foam, etc., and this embodiment uses high-density polyethylene floating material; The annular reaction chamber 6 is filled with a microbial system, which is used to denitrify the roots of floating island plants and provide a carbon source. The microbial system includes an isolation net cylinder 4, a dense denitrifying bacteria gel carrier 2 filled between the isolation net cylinder 4 and the inner cylinder 1, and a large-particle-size porous nitrifying bacteria gel carrier 3 filled between the isolation net cylinder 4 and the outer cylinder 5. The inner wall of the inner cylinder 1 is provided with multiple capillary guide tubes 7 extending towards the center of the inner cylinder 1 and used to transport the root secretions of the floating island plants outward through capillary action. For example, the capillary guide tubes 7 with an inner diameter of 1.0±0.2 mm are evenly distributed at a density of 10-15 per square decimeter. The capillary guide tubes 7 are made of hydrophilic modified materials (such as nylon with surface plasma treatment) to ensure a significant wetting and climbing effect on the root secretions. This inner diameter range ensures the capillary driving force while effectively preventing the blockage of rhizosphere particles and biofilms, and ensures the stability of fluid communication with the negative pressure end of the buffer thorn 8. One end of the tube extends into the center of the inner cylinder 1 to actively draw root secretions through capillary action, and the other end is connected to the Venturi effect generation point inside the buffer thorn 8. The outer cylinder 5 is provided with multiple through holes 9 and buffer spikes 8 for reducing the impact of water flow and facilitating the transport of substances within the microbial system; the buffer spikes 8 are streamlined wing-shaped or cylindrical, and in this embodiment, they are cylindrical. like Figure 4 , Figure 5 As shown, the buffer spike 8 is hollow inside, and has multiple first micropores 14 on one side of its sidewall. The buffer spike 8 has a partition tube 15 inside, and the space between the partition tube 15 and the inner wall of the buffer spike 8 is filled with a slow-release carbon source filler 13. The slow-release carbon source filler 13 is a porous polycaprolactone and modified starch composite particle, which is made by melt blending and extruding polycaprolactone and modified starch at a mass ratio of 7:3. After premixing polycaprolactone and modified starch at a mass ratio of 7:3, the mixture is added to a twin-screw extruder. The barrel temperature is controlled at 130℃ and the screw speed is 40 rpm. After melt blending for 10 min, the mixture is extruded into strips through a die and cut into cylindrical particles with a particle size of 3~5 mm by a water-cooled pelletizer. The resulting particles are vacuum dried at 45℃ for 5 h to remove residual moisture.

[0025] The modified starch is corn starch that has undergone pre-gelatinization and cross-linking treatment with alkali solution. Specifically, the corn starch is dispersed in a 2% sodium hydroxide solution (starch to alkali solution mass ratio 1:5), and gelatinized at 85℃ for 35 min. The temperature is then lowered to 50℃, and 3% (by weight) epichlorohydrin is added as a cross-linking agent. The reaction continues for 2 h, followed by neutralization with dilute hydrochloric acid to pH 6.0. After centrifugation, washing, vacuum drying, pulverization, and sieving, cross-linked modified starch is obtained, with the degree of cross-linking controlled at 60% to balance water solubility and structural stability. The modified starch is used to regulate the carbon source release rate. The composite particles contain a water-soluble pore-forming agent, sodium bicarbonate, which is dissolved by water washing after granulation, thereby forming interconnected micron-level dissolution channels within the particles. These channels are used to continuously release small-molecule organic carbon through a convection-diffusion mechanism driven by the pressure of stagnant water flow.

[0026] The separator tube 15 is elliptical in shape. One end of the separator tube 15 is disposed inside the buffer spike 8, and a plurality of second micropores 12 are provided on one side of the sidewall. The second micropores 12 are disposed opposite to the first micropores 14. The other end of the separator tube 15 is connected to the large-particle-size porous nitrifying bacteria gel carrier 3. One end of the capillary guide tube 7 is located inside the inner cylinder 1, and the other end is located inside one end of the separator tube 15.

[0027] The dense denitrifying bacteria gel carrier 2 is prepared by using 10% PVA, 1.5% SA, 0.8% conductive medium, 2% solid carbon source powder, and the balance being denitrifying bacteria suspension as raw materials. The mixture is prepared by physically mixing each component evenly and then dripping it into a composite crosslinking liquid containing 3% boric acid and 2% calcium chloride, followed by a double crosslinking curing method. The conductive medium is biochar powder, and in this embodiment, 0.8% biochar powder is used. The solid carbon source powder is polycaprolactone powder, used to provide an endogenous electron donor; in this embodiment, 1% polycaprolactone powder is used.

[0028] It should be understood that the dense denitrifying bacteria gel carrier 2 is a composite hydrogel microsphere prepared by using polyvinyl alcohol (PVA) and sodium alginate (SA) as a framework, and doping it with conductive medium (biochar powder) and solid carbon source powder (polycaprolactone PCL), with a particle size of 3-5 mm; the carrier microsphere has a dense surface skin structure and an oxygen diffusion coefficient of less than 10. -9 m 2 / s ; The large-particle-size porous nitrifying bacteria gel carrier 3 is prepared by using 10% polyvinyl alcohol, 0.8% chitosan, 3% coupled ammonia nitrogen adsorbent material, and 2% pore-forming agent as raw materials. The process involves physically mixing the components to form a gel solution, then dripping it into an alkaline crosslinking solution containing 15% sodium sulfate and 4% sodium hydroxide to solidify it, followed by soaking in water to dissolve the pore-forming agent. The ammonia nitrogen adsorbent material is modified zeolite powder or attapulgite clay. In this embodiment, modified zeolite powder is used, and the pore-forming agent specifically selected in this embodiment is 1% sodium bicarbonate. It should be understood that sodium bicarbonate can achieve "in-situ pore formation": the solidified gel particles are soaked and washed in water, and the water-soluble pore-forming agent (such as sodium bicarbonate) inside is dissolved by the osmotic pressure difference, thereby forming a connected macroporous network structure in situ inside the carrier.

[0029] It should be understood that the large-particle-size porous nitrifying bacteria gel carrier 3 is a macroporous network structure hydrogel prepared using polyvinyl alcohol (PVA) and chitosan (CS) as the backbone and coupled with ammonia nitrogen adsorption materials (modified zeolite powder, attapulgite clay) as raw materials; the carrier embeds one or more of denitrifying bacteria, phosphorus-removing bacteria, or heavy metal degrading bacteria, and in this embodiment, a composite nitrifying bacteria agent is used; it is composed of Nitrosomonas spp. ( Nitrosomonas sp.) and Nitrifying Bacteria ( Nitrobacter The bacterial suspension (sp.) is prepared by mixing bacterial cells at a 1:1 ratio, and the effective viable count (CFU) of the bacterial suspension before encapsulation is not less than 1.0 × 10⁻⁶. 8 CFU / mL; the Nitrosomonas used in the embodiments of this invention are... Nitrosomonas europaea ATCC 19718, Nitrifying Bacillus is Nitrobacter winogradskyi Both strains, ATCC 25391, were purchased from ATCC. After separate culture expansion of the two strains, they were mixed at a 1:1 ratio to produce an effective viable count of not less than 1.0 × 10⁻⁶. 8 A mixed bacterial suspension of CFU / mL is used for subsequent embedding; the particle size of the large-particle porous nitrifying bacteria gel carrier is 8~12 mm.

[0030] It should be understood that the inner cylinder diameter needs to be determined based on the expected biomass and extension space of the plant roots; the outer cylinder diameter needs to be set in combination with the buoyancy of the floating island and the overall size, while ensuring sufficient purification capacity. The volume ratio of the two functional bacterial carriers (i.e., the installation position of the isolation net cylinder) is a core technical parameter of the device's purification performance, and needs to be independently calculated and set within a certain range according to the water quality purification requirements of the target water body (especially the biochemical reaction kinetics of denitrification).

[0031] The root system condition determines the scale of the reaction, but the volume ratio required for nitrification and denitrification is mainly determined by the influent ammonia nitrogen concentration, the target nitrogen removal efficiency, the hydraulic retention time, and the reaction rates of the two types of microorganisms. For example, if the influent ammonia nitrogen load is high, a larger outer nitrification zone volume is required; if the total nitrogen removal requirement is high and the carbon source is relatively sufficient, the inner denitrification zone volume needs to be expanded accordingly.

[0032] Therefore, when designing the device of this invention, the diameter range of the inner and outer cylinders is first determined according to the root system size to obtain the total usable volume of the annular chamber; then, the required carrier packing volume for each of the nitrification and denitrification processes is calculated according to the water quality target, so as to accurately determine the installation diameter of the isolation net cylinder and ensure that the reserved flow channel can still meet the hydraulic exchange requirements after being filled with sufficient functional bacteria.

[0033] For example, in conventional biological nitrogen removal processes for wastewater, the volume ratio of the anoxic zone to the aerobic zone is a key design parameter. For this device, drawing on this principle and combining it with its internal carbon source supplementation to enhance denitrification, the ratio of the filling volume of the dense denitrifying bacteria gel carrier 2 to the filling volume of the large-particle-size porous nitrifying bacteria gel carrier 3 is 1:1.5.

[0034] The elliptical parameter of the elliptical partition tube 15 is related to the inner diameter of the buffer spike 8 as follows: (1-1) (1-2) The ellipse parameters include the major axis of the ellipse. a minor axis of the ellipse b In equations (1-1) and (1-2), a The major axis of the ellipse This is a correction factor with a value ranging from 0.7 to 0.9; for example, in this embodiment, it is set to 0.8. b The minor axis of the ellipse To accommodate the inner diameter of the 8-inch buffer spike, a diameter of 30mm is chosen.

[0035] The area of ​​the second micropore 12 satisfies: (1-3) In equation (1-3), This is an empirical coefficient with a value range of 0.1 to 0.3; for example, in this embodiment, it is set to 0.2. This refers to the area between the outer wall of the separator tube and the inner wall of the buffer spike. n The value is an exponent with a range of 0.5 to 1; in this embodiment, it is 0.6.

[0036] The working method of the device in this embodiment of the invention is as follows: First, the pre-prepared dense denitrifying bacteria and porous nitrifying bacteria gel carrier are filled into the annular reaction chamber 6 according to the designed ratio; the roots of the ecological floating island plants are passed through the channels of the inner cylinder 1, so that they are physically adjacent to the functional bacterial carrier in the annular reaction chamber 6; then, the device module is securely installed under the floating substrate of the floating island and submerged in the water by the suspension connector 10; the dense skin of the dense denitrifying bacteria gel carrier 2 effectively isolates external dissolved oxygen and constructs a stable anoxic microreactor inside; the large-particle porous nitrifying bacteria gel carrier 3 is formed by polyvinyl alcohol-chitosan skeleton, adding modified zeolite powder and other ammonia nitrogen adsorbents and using pore-forming agents, the large-pore network structure enriches ammonia nitrogen and provides a high specific surface area for biological colonization; Subsequently, when the ambient water flow impacts the buffer spike 8, the kinetic energy of the impact is converted into pressure energy, driving the external water body to actively inject and dissolve the carbon source, generating a high-pressure carbon-rich liquid within the buffer spike 8. The resulting high-pressure carbon-rich liquid flow forms a high-speed jet within the elliptical partition tube 15, actively drawing in and mixing root exudates absorbed by the capillary guide tube 7 through the Venturi effect. The mixed liquid is then directionally released onto the large-particle-size porous nitrifying bacteria gel carrier 3 of the partition. This process achieves precise replenishment of carbon sources and root signaling substances, as well as internal micro-disturbance, activating and enhancing the biological purification function of the partition: in the outer layer, porous nitrification... The carrier (large-particle-size porous nitrifying bacteria gel carrier 3) utilizes its adsorption properties to enrich ammonia nitrogen, significantly improving the conversion efficiency of the encapsulated nitrifying bacteria community. In the inner layer, the dense denitrification carrier, within the anoxic core, relies on the built-in conductive medium to accelerate electron transfer and utilizes a slow-release solid carbon source to continuously drive efficient nitrate reduction. Ultimately, it achieves: 1. precise replenishment of carbon source and root exudates; 2. micro-disturbance of the carrier bed to prevent clogging; 3. enhanced efficient synergy between "plant roots - aerobic nitrifying bacteria - anoxic denitrifying bacteria" in a spatially ordered microenvironment, thereby achieving the cascade degradation of pollutants such as nitrogen.

[0037] Finally, after the treatment cycle is completed, the entire device can be removed via the suspension connector 10, and the bottom cover can be opened to completely remove the functional bacterial carrier for regeneration or harmless treatment, ensuring the environmental friendliness and reusability of the technology throughout its entire lifecycle.

[0038] I. Investigating the influence of the geometric parameters of the buffer spikes and separator tubes on the root system function of the device; Comparative Example 1: This comparative example is largely the same as Example 1, except that no partition tube is provided inside the buffer spike 8.

[0039] Comparative Example 2: This comparative example is largely the same as Example 1, except that the partition tube 15 is replaced with a tube with a perfectly circular cross-section. Right now a = b =0.5D.

[0040] Comparative Example 3: This comparative example is largely the same as Example 1, except that the correction factor in the separator tube 15 is 1, i.e. a =D, b =0.5 a The area of ​​the second micropore is equal to 0.5A.

[0041] Experiment 1: The root exudate transport efficiency was determined using a fluorescence tracer method. After culturing canna roots in a 0.1% sodium fluorescein solution for 72 hours, the roots were placed inside an inner tube and run for 2 hours under a water flow of 0.2 m / s. The fluorescence intensity at the outlet of the dividing tube was measured, and the fluorescein transport amount per unit root dry weight was calculated. The results showed that the transport amount in Example 1 was 28.6 μg / g / h, in Comparative Example 1 it was 7.2 μg / g / h, in Comparative Example 2 it was 15.4 μg / g / h, and in Comparative Example 3 it was 11.8 μg / g / h. Example 1 showed an improvement of approximately 297%, 86%, and 142% compared to Comparative Examples 1, 2, and 3, respectively, confirming that the Venturi negative pressure effect of the elliptical dividing tube can increase the active root exudate uptake efficiency to 3.97 times that of the tube without a dividing tube structure.

[0042] Experiment 2: Continuous operation to determine total nitrogen removal rate; The system was operated for 15 days under conditions of C / N = 3.5, TN = 45 mg / L, and a flow rate of 0.2 m / s. The total nitrogen concentration in the effluent was measured daily, and the average removal rate was calculated. Experimental results: The total nitrogen removal rate in Example 1 was 91.3%, compared to 52.6% in Comparative Example 1, 71.4% in Comparative Example 2, and 68.2% in Comparative Example 3. The carbon source utilization efficiency in Example 1 was correspondingly increased by 153%, 55%, and 85%, verifying the crucial role of geometric parameter optimization in nitrogen removal.

[0043] II. Investigating the effects of functional bacterial carrier materials on the root function of the device; Comparative Example 4: This comparative example is largely the same as Example 1, except that only a large-particle-size porous nitrifying bacteria gel carrier is used. Comparative Example 5: This comparative example is largely the same as Example 1, except that the dense denitrifying bacteria gel carrier is prepared using only polyvinyl alcohol denitrifying bacteria suspension, and the preparation method is the same as in Example 1.

[0044] Experiment 3: Dissolved Oxygen Distribution Measurement and Denitrification Rate Verification; The radial dissolved oxygen distribution in the annular reaction chamber 6 was measured using microelectrodes, and the nitrate removal rate was also measured. In Example 1, the dissolved oxygen concentration in the inner layer was 0.15 mg / L, under a stable anoxic state, and the denitrification rate was 18.6 mg nitrate removed per gram of carrier per hour. In Comparative Example 4, because it used entirely aerobic nitrification carriers, the dissolved oxygen concentration in the inner layer was 4.2 mg / L, and the denitrification rate was only 2.1 mg nitrate removed per gram of carrier per hour, a decrease of 88.7% compared to Example 1. In Comparative Example 5, the dissolved oxygen in the inner layer was 0.18 mg / L, but the denitrification rate was 11.3 mg nitrate removed per gram of carrier per hour, a decrease of 39.2% compared to Example 1, confirming the synergistic enhancing effect of biochar electron transfer and the carbon source within the PCL on denitrification efficiency.

[0045] Experiment 2: Verification of Total Nitrogen Removal Rate under Low C / N Ratio Conditions; The experiment was conducted continuously for 12 days under the following conditions: influent C / N = 3.0, ammonia nitrogen 25 mg / L, nitrate nitrogen 20 mg / L, and total nitrogen 45 mg / L. The total nitrogen removal rate and nitrate nitrogen accumulation in the effluent were measured. Example 1 achieved a total nitrogen removal rate of 89.4%, with the effluent nitrate nitrogen concentration remaining stable below 3.2 mg / L. Comparative Example 4, lacking a denitrification zone, had a total nitrogen removal rate of only 46.8%, with an effluent nitrate nitrogen concentration as high as 28.6 mg / L, indicating severe nitrate nitrogen accumulation. Comparative Example 5 achieved a total nitrogen removal rate of 72.5%, with an effluent nitrate nitrogen concentration of 12.4 mg / L. After 8 days of operation, the denitrification rate decreased by 35%, indicating depletion of the internal carbon source due to the absence of PCL. Example 1 showed a total nitrogen removal rate 42.6 percentage points and 16.9 percentage points higher than Comparative Examples 4 and 5, respectively, and its operational stability was significantly better than Comparative Example 5.

[0046] Example 2: The dense denitrifying bacteria gel carrier 2 is prepared by using 8% PVA, 1% SA, 0.5% conductive medium, 1% solid carbon source powder, and the balance being denitrifying bacteria suspension as raw materials. The mixture is prepared by physically mixing each component evenly and then dripping it into a composite crosslinking liquid containing 3% boric acid and 2% calcium chloride, followed by a double crosslinking curing method. The conductive medium is nano-iron oxide (Fe3O4), and in this example, it is 0.8% biochar powder by mass. The solid carbon source powder is polyhydroxybutyrate valerate powder, used to provide an endogenous electron donor; in this example, it is 1% polycaprolactone powder.

[0047] The large-particle-size porous nitrifying bacteria gel carrier 3 is prepared by using 8% polyvinyl alcohol, 0.5% chitosan, 4% coupled ammonia nitrogen adsorbent material, and 1% porogen as raw materials. The process involves physically mixing the components to form a gel solution, then dripping it into an alkaline crosslinking solution containing 10% sodium sulfate and 2% sodium hydroxide for curing. The porogen is then dissolved by immersion in water. The ammonia nitrogen adsorbent material is modified zeolite powder and cation exchange resin powder. In this embodiment, modified zeolite powder is used, and the porogen specifically selected in this embodiment is 1% sodium bicarbonate. It should be understood that sodium bicarbonate can achieve "in-situ pore formation": the cured gel particles are immersed and washed in water, and the water-soluble porogen inside is dissolved by the osmotic pressure difference, thereby forming a connected macroporous network structure in situ inside the carrier. The slow-release carbon source filler is obtained by granulation of porous polycaprolactone and modified starch in a 6:4 mass ratio. The ratio of the filling volume of the dense denitrifying bacteria gel carrier 2 to the filling volume of the large-particle-size porous nitrifying bacteria gel carrier 3 is 1:1.

[0048] Example 3: The dense denitrifying bacteria gel carrier 2 is prepared by using 12% PVA, 2% SA, 1% conductive medium, 3% solid carbon source powder, and the balance being denitrifying bacteria suspension as raw materials. The mixture is prepared by physically mixing each component evenly and then dripping it into a composite crosslinking liquid containing 3% boric acid and 2% calcium chloride, followed by a double crosslinking curing method. The conductive medium is nano-iron oxide (Fe3O4), and in this example, it is 0.8% biochar powder by mass. The solid carbon source powder is polyhydroxybutyrate valerate powder, used to provide an endogenous electron donor; in this example, it is 1% polycaprolactone powder.

[0049] The large-particle-size porous nitrifying bacteria gel carrier 3 is prepared by using 12% polyvinyl alcohol, 1.5% chitosan, 4% coupled ammonia nitrogen adsorbent material, and 3% porogen as raw materials. The process involves physically mixing the components to form a gel solution, then dripping it into an alkaline crosslinking solution containing 20% ​​sodium sulfate and 5% sodium hydroxide to solidify it. The porogen is then dissolved by immersion in water. The ammonia nitrogen adsorbent material is cation exchange resin powder. In this embodiment, modified zeolite powder is used. Specifically, 1% sodium bicarbonate is selected as the porogen in this embodiment. It should be understood that sodium bicarbonate can achieve "in-situ pore formation": the solidified gel particles are immersed and washed in water, and the water-soluble porogen inside is dissolved by the osmotic pressure difference, thereby forming a connected macroporous network structure in situ inside the carrier. The slow-release carbon source filler is obtained by granulation of porous polycaprolactone and modified starch in a 6:3 mass ratio; the ratio of the filling volume of the dense denitrifying bacteria gel carrier 2 to the filling volume of the large-particle-size porous nitrifying bacteria gel carrier 3 is 1:2.

[0050] In summary, this invention achieves efficient and directional colonization of functional bacteria on the root surface through an inner cylinder guiding structure, solving the problem of difficult adhesion of traditional bacterial agents. Furthermore, the innovative buffer spike design effectively resists water erosion, providing physical protection against erosion for the bacterial agent and significantly improving its environmental retention rate and service life. Moreover, the modular suspension and detachable packaging structure makes the installation, recycling, and bacterial agent replacement of the device exceptionally convenient, ensuring the long-term maintainability and environmental safety of the system. Finally, all these design features work synergistically to construct a stable, efficient, and easily managed rhizosphere bioreactor around the roots, thereby significantly improving the synergistic purification efficiency of the floating island system for pollutants such as nitrogen and phosphorus.

Claims

1. A floating island root purification device induced by hydrodynamic response and biochemical zoning, characterized in that, The floating island root purification device includes: a double-cylinder structure connected to the floating island (11) for purifying the roots of the floating island plants; The double-cylinder structure includes an inner cylinder (1) fitted onto the root system of the floating island plant, an outer cylinder (5) fitted onto the inner cylinder (1), and an annular reaction chamber (6) disposed between the inner cylinder (1) and the outer cylinder (5); the inner cylinder (1) and the outer cylinder (5) are closed at both ends; The annular reaction chamber (6) is filled with a microbial system; the microbial system includes an isolation mesh cylinder (4), a dense denitrifying bacteria gel carrier (2) filled between the isolation mesh cylinder (4) and the inner cylinder (1), and a large-particle-size porous nitrifying bacteria gel carrier (3) filled between the isolation mesh cylinder (4) and the outer cylinder (5). The inner wall of the inner cylinder (1) is provided with a plurality of capillary guide tubes (7) extending toward the center of the inner cylinder (1) and used to transmit the secretions of the roots of the floating island plants outward through capillary action. The outer cylinder (5) is provided with multiple through holes (9) and buffer spikes (8) for reducing water flow impact and facilitating the transport of substances within the microbial system. The buffer spike (8) is hollow inside and has multiple first micropores (14) on one side of its sidewall. The buffer spike (8) has a partition tube (15) inside, and the space between the partition tube (15) and the inner wall of the buffer spike (8) is filled with a slow-release carbon source filler (13). The separator tube (15) is elliptical. One end of the separator tube (15) is located inside the buffer spike (8), and a plurality of second micropores (12) are provided on one side of the sidewall. The second micropores (12) are arranged opposite to the first micropores (14). The other end of the separator tube (15) is connected to the large-particle-size porous nitrifying bacteria gel carrier (3). One end of the capillary guide tube (7) is located inside the inner cylinder (1), and the other end is located inside the separator tube (15).

2. The floating island root purification device based on hydrodynamic response and biochemical zoning as described in claim 1, characterized in that, The buffer spike (8) is streamlined wing-shaped or cylindrical.

3. The floating island root purification device based on hydrodynamic response and biochemical zoning as described in claim 1, characterized in that, The double-cylinder structure is installed on the floating material of the floating island (11) via a suspension connector (10); the suspension connector (10) is a connecting chain with a bayonet, hinge hook or shackle.

4. The floating island root purification device based on hydrodynamic response and biochemical zoning as described in claim 1, characterized in that, The dense denitrifying bacteria gel carrier (2) is prepared from raw materials with a mass percentage of 8%~12% PVA, 1%~2% SA, 0.5%~1% conductive medium, 1%~3% solid carbon source powder, and the balance being denitrifying bacteria suspension; the particle size is 3~5mm; wherein, the conductive medium is biochar powder or nano-iron oxide; the solid carbon source powder is polycaprolactone powder or polyhydroxybutyrate valerate powder, used to provide endogenous electron donors.

5. The floating island root purification device based on hydrodynamic response and biochemical zoning as described in claim 1, characterized in that, The large-particle-size porous nitrifying bacteria gel carrier (3) is prepared from raw materials with a mass percentage of 8%~12% polyvinyl alcohol, 0.5%~1.5% chitosan, 2%~4% coupled ammonia nitrogen adsorbent material, and 1%~3% pore-forming agent; the particle size is 8~12mm; the ammonia nitrogen adsorbent material is modified zeolite powder, attapulgite clay or cation exchange resin powder.

6. The floating island root purification device induced by hydrodynamic response and biochemical zoning as described in claim 1, characterized in that, The ratio of the filling volume of the dense denitrifying bacteria gel carrier (2) to the filling volume of the large-particle-size porous nitrifying bacteria gel carrier (3) is 1:1.3 ~ 1:1.

6.

7. The floating island root purification device based on hydrodynamic response and biochemical zoning as described in claim 1, characterized in that, The elliptical parameters of the elliptical separator tube (15) and the inner diameter of the buffer spike (8) satisfy the following: （1-1） （1-2） The ellipse parameters include the major axis of the ellipse. a minor axis of the ellipse b In equations (1-1) and (1-2), a The major axis of the ellipse This is a correction factor with a value range of 0.7 to 0.

9. b The minor axis of the ellipse The inner diameter of the buffer thorn (8) is used for buffering.

8. The floating island root purification device based on hydrodynamic response and biochemical zoning as described in claim 7, characterized in that, The area of ​​the second micropore (12) satisfies: （1-3） In equation (1-3), These are empirical coefficients with values ​​ranging from 0.1 to 0.

3. This refers to the area between the outer wall of the separator tube and the inner wall of the buffer spike. n It is an exponent with a value range of 0.5 to 1.

9. The floating island root purification device induced by hydrodynamic response and biochemical zoning as described in claim 1, characterized in that, The slow-release carbon source filler is obtained by granulation of porous polycaprolactone and modified starch in a mass ratio of 6~7:3~4; the modified starch is starch that has undergone alkali gelatinization and cross-linking treatment.

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