A composite microbial carrier particle for river ammonia nitrogen treatment and a preparation method thereof

Abstract

The application discloses a kind of composite microbial carrier particles for river ammonia nitrogen treatment and preparation method thereof, the particle includes four-layer structure successively from inside to outside, magnetic counterweight inner core, slow-release function middle layer, composite bacterial population active layer and gel protective shell;Magnetic counterweight inner core is iron oxide-based particle;Slow-release function middle layer includes porous adsorption component, calcium peroxide slow-release microcapsule, slow-release alkaline carbonate component and sodium alginate adhesive, actively build oxygen supply, carbon source supply and pH self-buffering microenvironment in the particle interior;Composite bacterial population active layer is loaded with ammonia-oxidizing bacteria and heterotrophic nitrification-aerobic denitrifying bacteria mixed at a volume ratio of 2:1 to 3:1;Gel protective shell is formed by gel component containing porogen through calcium ion crosslinking solidification.The application can be directly thrown and added, while achieving multiple functions such as anti-scour, anti-predation, low DO adaptation, ammonia nitrogen and total nitrogen synergistic removal, etc., with stable treatment effect, simple construction and low cost.

Description

Technical Field

[0001] This invention relates to the field of river management technology, specifically to a composite microbial carrier particle for ammonia nitrogen treatment in rivers and its preparation method. Background Technology

[0002] Ammonia nitrogen pollution in rivers is a key and challenging aspect of current water environment management. Nitrifying bacteria (including ammonia oxidizing bacteria AOB and nitrite oxidizing bacteria NOB) can efficiently convert ammonia nitrogen into nitrite and nitrate, making them the core functional bacteria for biological denitrification. Heterotrophic nitrifying-aerobic denitrifying bacteria (HN-AD) can further reduce nitrate to nitrogen gas under aerobic conditions, removing it from the water body, which is particularly crucial for reducing total nitrogen. However, directly adding these denitrifying agents to rivers in their free state faces several difficulties: the density of free bacteria is close to the density of water (approximately 1.0 g / cm³). 3 Nitrifying bacteria are carried away by the river flow and remain there for a very short time. The river contains numerous microscopic predators (50-500 μm in size) such as protozoa and rotifers, which consume large quantities of free-floating bacteria. Dissolved oxygen levels in the river (especially in winter) are low, often below the 2 mg / L threshold required for strict aerobic nitrification. The nitrification reaction consumes approximately 7.14 mg of HCO3 to oxidize 1 mg of ammonia nitrogen. - And generate H + This leads to a decrease in water pH, which in turn inhibits the activity of nitrifying bacteria. Furthermore, a single nitrifying bacteria species can usually only complete the incomplete conversion of ammonia nitrogen to nitrate, and cannot achieve simultaneous reduction of total nitrogen.

[0003] To overcome the aforementioned drawbacks of adding free bacteria, various microbial carrier technologies have been developed in this field. For example, the suspended packing material MBBR system requires a fixed support, making it unsuitable for open waterways; another example is monolayer encapsulated bacterial balls based on sodium alginate or polyvinyl alcohol, which, although able to fix the bacteria inside the particles, will still float and be lost with the water flow due to their overall density being close to that of water. The monolayer gel structure cannot actively establish oxygen supply and pH buffering inside the particles, and the activity of the internal bacteria drops sharply under low DO conditions; yet another example is the double-layer encapsulation structure in the field of probiotic microcapsules, which, although providing some physical protection, is not compatible with the denitrification scenario of water bodies, lacking both an oxygen supply mechanism and a pH self-buffering and substrate enrichment system.

[0004] Therefore, existing microbial carrier technologies cannot simultaneously meet the following requirements when applied to ammonia nitrogen control in rivers: First, the particles must be able to settle stably on the riverbed and resist water erosion; second, they must be able to physically prevent microscopic predators from directly contacting the internal microorganisms; third, they must be able to continuously supply oxygen to the microorganisms under low dissolved oxygen (DO) conditions; fourth, they must be able to neutralize the acidity produced by nitrification online and continuously supply inorganic carbon sources; fifth, they must be able to locally enrich substrates within the particles to maintain high microbial activity; and sixth, they must be able to simultaneously achieve ammonia nitrogen conversion and total nitrogen reduction. Therefore, there is an urgent need to develop a composite microbial carrier particle that can simultaneously meet the above six requirements and can be directly applied by dumping. Summary of the Invention

[0005] The purpose of this invention is to provide a composite microbial carrier particle for ammonia nitrogen treatment in rivers and its preparation method. It can be directly applied and simultaneously achieves multiple functions such as erosion resistance, predation resistance, low DO adaptation, and synergistic removal of ammonia nitrogen and total nitrogen. The treatment effect is stable, construction is simple, and the cost is low.

[0006] To achieve the above objectives, the present invention proposes the following technical solution: a composite microbial carrier particle for ammonia nitrogen treatment in rivers, wherein the carrier particle comprises, from the inside out, a magnetic weighted core, a slow-release functional intermediate layer, a composite microbial community active layer, and a gel protective shell, forming a four-layer structure; wherein the magnetic weighted core is an iron oxide-based particle with a density of not less than 2.5 g / cm³. 3 The sustained-release functional intermediate layer is wrapped around the magnetic weight core and includes at least a porous adsorption component, calcium peroxide sustained-release microcapsules, a sustained-release alkaline carbonate component, and sodium alginate binder. The composite bacterial community active layer is wrapped around the sustained-release functional intermediate layer and is formed by loading a composite bacterial solution of ammonia-oxidizing bacteria AOB and heterotrophic nitrifying-aerobic denitrifying bacteria HN-AD in a bacterial-liquid volume ratio of 2:1 to 3:1 onto a porous hydrogel matrix. The gel protective shell is wrapped around the composite bacterial community active layer and is formed by cross-linking and curing of a gel component containing a porogen with calcium ions, and has a micropore array with a pore size of 10-50 μm on its surface.

[0007] Furthermore, in this invention, the overall diameter of the carrier particles is 3-8 mm, and the overall density is 1.6-2.0 g / cm³. 3 The total number of active bacteria in the composite microbial community active layer is not less than 1×10⁻⁶. 8 CFU / g granules.

[0008] Furthermore, in this invention, the magnetic counterweight core is Fe3O4 magnetic ceramic particles or Fe2O3 modified quartz sand; wherein the Fe3O4 magnetic ceramic particles are obtained by mixing clay and Fe3O4 powder at a mass ratio of 7:3, molding, and then sintering at 800-900°C, with an Fe3O4 content of 30%-40% and a magnetization intensity of not less than 10 emu / g; the Fe2O3 modified quartz sand is obtained by impregnating quartz sand with a particle size of 1-3 mm with 0.1-0.5 mol / L Fe(NO3)3 solution and calcining it three times, with a surface Fe2O3 loading of 5%-8% of the quartz sand mass.

[0009] Furthermore, in this invention, the sustained-release functional intermediate layer is composed of the following components by weight: 30-40 parts of acid-thermal dual-activated zeolite powder, 10-20 parts of activated carbon powder, 8-15 parts of calcium peroxide sustained-release microcapsules, 3-8 parts of sodium bicarbonate, 3-5 parts of calcium carbonate, 2-4 parts of dipotassium hydrogen phosphate, 0.5-1.5 parts of magnesium sulfate, and 10-15 parts of sodium alginate.

[0010] Furthermore, in this invention, the acid-thermal dual-activated zeolite powder is obtained from 80-100 mesh natural clinoptilolite through the following treatment: immersion in 1 mol / L hydrochloric acid at 25 °C for 2 h with stirring and ultrasonication for 30 min, followed by filtration and washing with deionized water until the pH of the filtrate is neutral, drying at 105 °C, and then activation at 350 °C for 2 h; the BET specific surface area of ​​the activated zeolite powder is not less than 450 m². 2 / g, with an adsorption capacity of not less than 18 mg / g for ammonia nitrogen; the calcium peroxide sustained-release microcapsules are prepared by melting and blending anhydrous CaO2 powder and stearic acid at a mass ratio of 4:1 at 80 °C and then spray cooling and granulating, with a microcapsule particle size of 100-200 μm.

[0011] Furthermore, in this invention, the ammonia-oxidizing bacteria AOB are selected from at least one of Nitrosomonas europaea and Nitrosomonas oligotropha; the heterotrophic nitrifying-aerobic denitrifying bacteria HN-AD are selected from at least one of Pseudomonas stutzeri and Bacillus methylotrophicus; and the total concentration of the compound bacterial solution is not less than 1×10⁻⁶. 8 CFU / mL.

[0012] Furthermore, in this invention, the porous hydrogel matrix is ​​composed of a mixture of 3 wt% sodium alginate aqueous solution and 1 wt% polyvinyl alcohol aqueous solution; the composite bacterial solution is mixed with the porous hydrogel matrix at a volume ratio of 1:3 and then impregnated and coated on the surface of the sustained-release functional intermediate layer particles to form the composite bacterial active layer with a thickness of 0.2-0.5 mm.

[0013] Furthermore, in this invention, the gel protective shell is made of the following components by weight: 1.5-2.5 parts sodium alginate, 0.5-1.0 parts chitosan dissolved in 1 wt% acetic acid, 1.0-2.0 parts biochar powder, and 0.5-1.0 parts glucose as a pore-forming agent; the gel protective shell is formed by cross-linking and curing with a mixed curing solution of 3 wt% CaCl2 and 0.5 wt% boric acid at 4 °C for 15 min; the microporous array with a pore size of 10-50 μm is formed in situ by the composite microbial community metabolizing glucose to produce CO2 gas in an activation solution containing NH4Cl and NaHCO3 after the shell is cured.

[0014] A method for preparing composite microbial carrier particles as described above, characterized by comprising the following steps in sequence: S1, preparing the magnetic weighted core; S2, preparing the acid-thermal dual-activated zeolite powder and the calcium peroxide sustained-release microcapsules respectively; S3, mixing ammonia-oxidizing bacteria AOB bacterial solution and heterotrophic nitrifying-aerobic denitrifying bacteria HN-AD bacterial solution at a bacterial volume ratio of 2:1 to 3:1 to obtain a total concentration of not less than 1×10⁻⁶. 8S4. Add each component to deionized water according to the above mass ratio and stir to form a paste. Coat the magnetic weight core obtained in step S1 with the paste in a rolling coating device and vacuum dry at 40 °C. Repeat the coating-drying process more than 2 times until the intermediate layer accounts for 50%-55% of the total particle mass. S5. Mix the composite bacterial solution obtained in step S3 with a porous hydrogel matrix composed of 3 wt% sodium alginate and 1 wt% polyvinyl alcohol at a volume ratio of 1:3. Immerse the particles obtained in step S4 in the mixture at 20 °C for 30 min, and drain. S6. Prepare the outer shell slurry according to the above mass ratio. Roll the particles obtained in step S5 into the outer shell slurry at 30 rpm for 5 min. Immediately after removal, immerse them in a mixed curing solution of 3 wt% CaCl2 and 0.5 wt% boric acid and crosslink and cure at 4 °C for 15 minutes. min, and wash with sterile physiological saline; S7, place the particles obtained in step S6 in an activation solution containing 30 mg / L NH4Cl and 100 mg / L NaHCO3, and culture at 25 °C for 48 h with aeration, so that the composite microbial community metabolizes glucose to produce CO2 gas and forms a micropore array with a pore size of 10-50 μm in situ on the gel protective shell, thus obtaining the composite microbial carrier particles.

[0015] A method for treating ammonia nitrogen in rivers involves applying the aforementioned composite microbial carrier particles at a dosage of 30-80 g / L to the river to be treated. The composite microbial carrier particles are deposited on the riverbed surface through their magnetic weighted cores, and their internal dual-gradient microenvironment allows ammonia-oxidizing bacteria (AOB) and heterotrophic nitrifying-aerobic denitrifying bacteria (HN-AD) to simultaneously undergo nitrification and denitrification reactions, thereby synergistically removing ammonia nitrogen and total nitrogen from the water. After the treatment cycle, the composite microbial carrier particles are recovered using a magnetic separator.

[0016] Beneficial effects: The technical solution of this application has the following technical effects: This invention provides a systematic and integrated solution to the six requirements listed in the background technology by employing a four-layer synergistic structure consisting of a magnetic weighting core, a slow-release functional intermediate layer, a composite microbial community active layer, and a gel protective shell. Specifically, the magnetic weighting core ensures that the overall particle density is much greater than that of water, allowing it to immediately settle on the riverbed and remain stable after addition. Under water flow conditions, the loss rate is reduced by more than an order of magnitude compared to free bacterial solutions. The 10-50 μm microporous array on the surface of the gel protective shell is precisely within a sieving window where small molecules can pass through but microbial predators cannot, allowing water molecules, ammonia nitrogen molecules and ions, dissolved oxygen molecules, and HCO3 to pass through. -Small molecules can freely enter the particles to participate in the reaction, while predators such as protozoa and rotifers with a body size of 50 μm or larger are effectively blocked, resulting in a significantly higher bacterial survival rate compared to free bacterial agents.

[0017] More importantly, this invention synergistically integrates calcium peroxide slow-release microcapsules, slow-release alkaline carbonate components, and porous adsorption components in the slow-release functional intermediate layer. This enables the particles to actively establish a synergistic microenvironment of "internal oxygen supply, internal carbon supply, pH self-buffering, and substrate enrichment" in low-DO river environments: the slow decomposition of calcium peroxide releases O2, solving the problem of insufficient electron acceptors in bacteria; the slow-release alkaline carbonate continuously provides HCO3 for autotrophic nitrifying bacteria. - The carbon source also neutralizes the H produced by the nitration reaction. + The internal pH of the granules is stabilized within the optimal range for nitrifying bacteria. The porous adsorption components, through localized enrichment of ammonia nitrogen, create a substrate microenvironment within the granules with a concentration far exceeding that of the bulk aqueous phase, allowing the nitrification reaction to proceed at a sustained high speed according to near-saturation kinetics. Simultaneously, AOB and HN-AD are co-loaded in the composite bacterial community active layer at a volume ratio of 2:1 to 3:1, enabling simultaneous nitrification and denitrification reactions within a single granule. This achieves a synergistic reduction of ammonia nitrogen and total nitrogen, rather than a simple transfer of nitrogen speciation. This multifunctional synergistic effect cannot be expected by simply superimposing individual technologies; rather, it is the nonlinear gain generated by the four-layer structure actively constructing a gradient microenvironment within the granules.

[0018] In summary, the composite microbial carrier particles described in this invention can be directly applied without the need for auxiliary supports. They possess six functions: resistance to water flow erosion, resistance to micro-predators, low DO adaptation, pH self-buffering, substrate enrichment, and synergistic removal of ammonia nitrogen and total nitrogen. The treatment effect is stable and long-lasting, construction is simple, and the unit treatment cost is significantly lower than that of existing MBBR packing processes. They are particularly suitable for in-situ biological denitrification treatment of open rivers, lakes, and other water bodies.

[0019] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other.

[0020] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0021] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 : Schematic diagram of granular structure cross-section; Figure 2 Schematic diagram of radial gradient distribution of particles; Figure 3 Ammonia nitrogen removal rate versus time curve; Figure 4 Bar chart showing unexpected technical effects under low DO conditions; Figure 5 : Comparison chart of long-term stability over 60 days of operation. Detailed Implementation

[0022] The embodiments of the invention will now be described in detail with reference to the accompanying drawings.

[0023] Example 1

[0024] The first step was the preparation of the magnetic counterweight core. 100 g of bentonite and 43 g of iron oxide powder (industrial grade, purity ≥98%, particle size ≤50 μm) were weighed out, mixed thoroughly, and then 25 mL of deionized water was added. The mixture was kneaded until it reached a plastic state, extruded and granulated into wet blanks with a particle size of 1-3 mm. The blanks were dried at 60 °C for 4 h, placed in a muffle furnace, heated to 850 °C at a rate of 5 °C / min, and sintered for 2 h. After natural cooling to room temperature, Fe3O4 magnetic ceramic particle cores were obtained. Magnetization of the obtained cores was measured to be 12.3 emu / g, and the particle density was 3.2 g / cm³. 3 .

[0025] The second step is the preparation of acid-thermal dual-activated zeolite powder. 500 g of 80-100 mesh natural clinoptilolite was immersed in 2 L of 1 mol / L hydrochloric acid and magnetically stirred at 25 °C for 2 h, supplemented with ultrasonic treatment for 30 min (100 W power). The mixture was then filtered, and the filter cake was repeatedly washed with deionized water until the pH of the filtrate reached 7.0. It was dried at 105 °C for 24 h, and then activated in a muffle furnace at a rate of 5 °C / min to 350 °C for 2 h. After natural cooling, the powder was stored for later use. The specific surface area of ​​the activated zeolite powder was measured using a BET surface area meter to be 462 m². 2 / g, the static adsorption capacity for ammonia nitrogen is 18.5 mg / g (unmodified zeolite under the same conditions is only 12.8 mg / g).

[0026] The third step is the preparation of calcium peroxide sustained-release microcapsules. 100 g of anhydrous calcium peroxide powder (CaO2 content ≥75%, particle size ≤50 μm) and 25 g of stearic acid were placed in a sealed heating vessel and melt-blended at 80 °C for 30 min until the stearic acid completely coated the surface of the CaO2 particles. The mixture was immediately sprayed into a spray cooling tower (nozzle temperature 80 °C, receiving temperature 5 °C) to collect microcapsules with a particle size of 100-200 μm. Oxygen production tests in water showed that the obtained microcapsules could continuously release oxygen in distilled water at 25 °C for 32 days, with an oxygen production rate of approximately 0.20 g O2 / g CaO2 per unit mass.

[0027] Step 4: Preparation of the compound bacterial solution. AOB bacterial solution: Nitrosomonas europaea ATCC 19718 was inoculated into a special culture medium for autotrophic nitrifying bacteria (NH4Cl 0.5 g / L, KH2PO4 0.7 g / L, K2HPO4 1.3 g / L, MgSO4·7H2O 0.05 g / L, NaHCO3 1.0 g / L, FeSO4·7H2O 0.014 g / L), and cultured at 30 °C and 150 rpm for 7 days until OD. 600 = 0.8, 4000 g, centrifuge for 10 min, collect bacterial cells, and resuspend in sterile physiological saline to a concentration of 1×10. 8 CFU / mL. HN-AD bacterial culture: Pseudomonas stutzeri was inoculated into LB liquid medium (10 g / L peptone, 5 g / L yeast extract, 10 g / L NaCl) and cultured at 30 °C and 180 rpm for 16 h until OD. 600 = 2.0, centrifuge to collect bacterial cells and resuspend to a concentration of 1×10. 9 CFU / mL. Mix the above AOB bacterial solution with HN-AD bacterial solution at a volume ratio of 2:1 to obtain a compound bacterial solution, and refrigerate at 4 °C before use.

[0028] Step 5: Coating the sustained-release intermediate layer. Prepare the intermediate layer slurry according to the following mass ratio: 35 parts acid-thermal activated zeolite powder, 15 parts activated carbon powder (200 mesh), 10 parts calcium peroxide sustained-release microcapsules, 5 parts sodium bicarbonate, 4 parts calcium carbonate, 3 parts dipotassium hydrogen phosphate, 1 part magnesium sulfate, 12 parts sodium alginate powder, and 60 parts deionized water. First, dissolve the sodium alginate in deionized water (stirring at 60 °C for 30 min), cool to room temperature, then add the remaining solid powders and stir until a paste is formed. Take 100 g of the magnetic ceramic particle core and place it in a rolling coating machine (30 rpm). Slowly spray the above slurry to coat it evenly, and vacuum dry at 40 °C for 2 h. Repeat the coating-drying process twice until the intermediate layer accounts for 52% of the total particle mass. The resulting particles have an average diameter of approximately 4.2 mm.

[0029] Step 6: Loading the composite bacterial activity layer. Prepare the gel matrix: Mix 3 wt% sodium alginate aqueous solution and 1 wt% polyvinyl alcohol aqueous solution at a volume ratio of 1:1, sterilize at 121 °C for 20 min, and then cool to room temperature. Take 30 mL of the above gel matrix and slowly mix it with 10 mL of the composite bacterial solution obtained in Step 4 (avoiding bubble generation) to obtain a bacterial solution-gel mixture. Place the particles obtained in Step 5 into this mixture and immerse them at 20 °C for 30 min. Remove and drain to form a composite bacterial activity layer with a thickness of approximately 0.3 mm.

[0030] Step 7: Formation and curing of the gel protective shell. Prepare the outer layer slurry according to the following mass ratio: 2.0 parts sodium alginate, 1.0 part chitosan (pre-dissolved in 1 wt% acetic acid aqueous solution), 1.5 parts biochar powder (≤200 mesh), 1.0 part glucose, and deionized water to a final volume of 100 parts. Stir until completely dissolved and homogeneous. Add the particles obtained in Step 6 to the outer layer slurry and roll them at 30 rpm for 5 min. Immediately after removal, immerse the mixture in a curing solution of 3 wt% CaCl2 and 0.5 wt% boric acid pre-cooled to 4 °C for cross-linking and curing for 15 min. After removal, rinse three times with sterile saline.

[0031] Step 8: In-situ pore formation and activation. The solidified particles were placed in an activation solution containing 30 mg / L NH4Cl and 100 mg / L NaHCO3 and cultured at 25 °C with aeration for 48 h. During this period, the bacterial cells in the active layer of the composite microbial community metabolized glucose in the capsid to produce CO2 gas, forming uniformly distributed micropores in situ on the gel protective capsid. After the culture was completed, the particles were removed and stored at 4 °C. Scanning electron microscopy showed that the capsid pore size was 15-45 μm; the overall diameter of the obtained particles was 4-6 mm, and the particle density was 1.78 g / cm³. 3 The total number of live bacteria was 1.3 × 10⁻⁶. 8 CFU / g granules.

[0032] Application Results. The above-mentioned granules were added to simulated river water at a dosage of 50 g / L (initial ammonia nitrogen 4.5 mg / L, initial TN 6.2 mg / L, DO 1.5 mg / L, water temperature 15 °C, continuous micro-aeration). Results: At 24 h, the ammonia nitrogen concentration decreased to 1.20 mg / L (removal rate 73.3%) and TN decreased to 3.50 mg / L (removal rate 43.5%); at 72 h, the ammonia nitrogen concentration decreased to 0.18 mg / L (removal rate 96.0%) and TN decreased to 1.50 mg / L (removal rate 75.8%); the effluent pH stabilized at 7.8 (pH 7.5 before addition, with no significant decrease throughout the process); the granule shells remained intact, and DAPI staining and counting showed a bacterial cell viability rate of 92.4%.

[0033] Example 2

[0034] This embodiment is designed for use in river channels during winter when the water temperature is 5-10 °C. Based on Embodiment 1, the following adjustments are made: First, the magnetic counterweight core is replaced with Fe2O3 modified quartz sand. 200 g of quartz sand with a particle size of 1-3 mm is washed, dried, and then immersed in a 0.3 mol / L Fe(NO3)3 solution for 24 h. After draining, it is calcined at 500 °C for 2 h. This immersion-calcination process is repeated three times, resulting in a final Fe2O3 loading of 6.5% of the quartz sand mass. The calcination is carried out under an oxygen-limited atmosphere, ensuring that the iron oxide loaded on the quartz sand surface is ferromagnetic γ-Fe2O3 (maghemite) rather than weakly magnetic α-Fe2O3. The saturation magnetization of the Fe2O3 modified quartz sand core is measured to be 4.8 emu / g using a vibrating sample magnetometer (VSM).

[0035] Second, in the compound bacterial solution, AOB was replaced with the low-temperature adapted strain Nitrosomonas oligotropha, and HN-AD was replaced with Bacillus methylotrophicus L7. After mixing the two in a volume ratio of 3:1, the total concentration reached 3.25 × 10⁻⁶. 8 CFU / mL; Third, the amount of calcium peroxide sustained-release microcapsules in the intermediate layer was increased from 10 parts to 14 parts to compensate for the decrease in the rate of oxygen consumption of the bacteria and the decrease in the rate of dissolved oxygen diffusion in water at low temperature; Fourth, 1 wt% glycerol was added to the outer shell slurry as an antifreeze agent to prevent the gel layer from becoming brittle at low temperature; The remaining steps, equipment and parameters are the same as in Example 1.

[0036] Application Effects. The obtained granules were added to simulated winter river water at a dosage of 50 g / L (water temperature 8 °C, DO 0.8 mg / L, initial ammonia nitrogen 5.0 mg / L, initial TN 7.5 mg / L). Results: After 72 h, the ammonia nitrogen concentration decreased to 0.93 mg / L (removal rate 81.4%), and TN decreased to 3.10 mg / L (removal rate 58.7%). As a control, under the same conditions, the ammonia nitrogen removal rate of the formulation in Example 1 (without strain replacement and without antifreeze) was only 65.2% after 72 h, and the ammonia nitrogen removal rate of conventional sodium alginate monolayer embedded bacterial balls was only 38.7%. This example demonstrates that by selecting a combination of low-temperature adaptable strains and appropriately increasing the dosage of calcium peroxide slow-release microcapsules, the present invention can still maintain ideal denitrification performance under low DO conditions in winter.

[0037] Example 3

[0038] This embodiment is designed for high-load river channels (such as the backwater section of black and odorous water bodies) with an initial ammonia nitrogen concentration ≥10 mg / L. Based on Embodiment 1, the following adjustments are made: First, the amount of acid-thermal dual-activated zeolite powder in the intermediate layer slurry is increased from 35 parts to 40 parts, activated carbon powder from 15 parts to 20 parts, and calcium peroxide slow-release microcapsules from 10 parts to 15 parts, to enhance the adsorption and enrichment capacity for high-concentration ammonia nitrogen and the continuous oxygen supply capacity; Second, the volume ratio of the composite bacterial solution to the gel matrix is ​​adjusted from 1:3 to 1:2, increasing the total number of active bacteria in the active bacterial layer to 2.1 × 10⁻⁶. 8 CFU / g particles; third, the outer shell adopts a two-coating-two-curing process to increase the thickness to 0.6-0.8 mm and improve mechanical strength; the remaining steps, equipment and parameters are the same as in Example 1.

[0039] Application Results. The obtained granules were added at a dosage of 60 g / L to simulated high-load river water (initial ammonia nitrogen 12.5 mg / L, initial TN 18.0 mg / L, DO 2.0 mg / L, water temperature 20 °C). Results: After 24 h, the ammonia nitrogen concentration decreased to 2.68 mg / L (removal rate 78.6%); after 72 h, the ammonia nitrogen concentration decreased to 0.52 mg / L (removal rate 95.8%), and TN decreased to 3.80 mg / L (removal rate 78.9%); after 30 days of continuous operation, the shell integrity rate of the granules was ≥95%, and the total active bacteria retention rate was ≥80%. This example demonstrates that the present invention still possesses stable removal performance under high ammonia nitrogen load scenarios.

[0040] Comparative Example 1 (Direct addition of free bacterial solution) An equal volume (converted to viable count equivalent) of AOB and HN-AD mixed bacterial solution (volume ratio 2:1) as in Example 1 was directly added to the same simulated river water as in Example 1, without any immobilization treatment. Results: 72h ammonia nitrogen removal rate was only 42.5%, and TN removal rate was only 18.6%; at a simulated flow velocity of 0.3 m / s, the bacterial solution loss rate reached 93.5% after 72h; 1×10⁻⁶ bacteria were added... 4 The bacterial cell survival rate was only 12.7% after 72 hours of immobilization with ciliates per mL. This result proves that free bacterial solutions are ineffective in open river water and that the four-layer immobilization structure is necessary to ensure effective cell retention and activity.

[0041] Comparative Example 2 (Conventional monolayer sodium alginate-embedded bacterial balls) A mixture of 3 wt% sodium alginate solution and an equal volume of composite bacterial solution was added dropwise to 3 wt% CaCl2 solidification solution to form single-layer gel bacterial balls with a particle size of 3-5 mm. These balls contained no magnetic core, no slow-release intermediate layer, and no in-situ porous outer shell. Under the same conditions as in Example 1, after 72 h, the ammonia nitrogen removal rate was 68.4%, the TN removal rate was 32.1%, and the bacterial ball density was only 1.05 g / cm³. 3 The water flow scouring loss rate was 21.8% after 72 hours; after 60 days of continuous operation, the ammonia nitrogen removal rate decreased to 38.5%. The results prove that single-layer gel encapsulation alone cannot achieve the comprehensive effect of this invention.

[0042] Comparative Example 3 (Calcium Peroxide-Free Sustained-Release Microcapsules) The granules were prepared exactly according to the process and proportions of Example 1, but the calcium peroxide sustained-release microcapsules were removed from the intermediate slurry (the amounts of the other 7 components were supplemented proportionally). The resulting granules, when added under the same conditions as in Example 1 (DO 1.5 mg / L): achieved an ammonia nitrogen removal rate of 74.2% and a TN removal rate of 48.5% after 72 h; further addition under low-oxygen conditions with DO of 0.8 mg / L resulted in an ammonia nitrogen removal rate of only 48.5% after 72 h. As a control, the granules from Example 1 still achieved an ammonia nitrogen removal rate of 86.7% after 72 h under the same low-DO conditions of 0.8 mg / L. This data indicates that the presence of the calcium peroxide sustained-release microcapsules increased the ammonia nitrogen removal rate of the granules by 38.2 percentage points (48.5% → 86.7%) under low-DO conditions, far exceeding the conventional expectation of those skilled in the art that "adding an oxygen-releasing agent can increase the removal rate by 10%-15%", constituting an unexpected technical effect.

[0043] Comparative Example 4 (containing only AOB single strain) The granules were prepared exactly according to the process and proportions of Example 1, but the composite bacterial active layer was only loaded with AOB bacterial solution (Nitrosomonas europaea, concentration adjusted to 1×10⁻⁶). 8 (CFU / mL, ensuring the total active bacteria count is consistent with Example 1), without adding HN-AD. The resulting granules were added under the same conditions as in Example 1: after 72 h, the ammonia nitrogen removal rate was 88.6% (close to 96.0% in Example 1), but the TN removal rate was only 33.2% (75.8% in Example 1). This data point indicates that co-loading AOB and HN-AD at the stated volume ratio of 2:1 to 3:1 increased the TN removal rate from 33.2% to 75.8% (an increase of 42.6 percentage points), demonstrating that the synergistic effect of the composite microbial community is key to achieving simultaneous reduction of ammonia nitrogen and total nitrogen in this invention, an effect that cannot be expected from simple loading of a single microbial species.

[0044] Comparative Example 5 (Conventional sand grain core replaced with magnetic core) The particles were prepared exactly according to the process and proportions of Example 1, but the magnetic ceramic core was replaced with particles of the same size and similar density (approximately 2.65 g / cm³). 3The particles were ordinary quartz sand cores (without Fe2O3 modification). When added under the same conditions as in Example 1, the ammonia nitrogen removal rate was 91.2% and the TN removal rate was 71.4% after 72 h (similar to Example 1). However, when the particles were recovered using a 0.3 T magnetic separator after the treatment cycle, the particle recovery rate in this comparative example was 0% (completely no magnetic response), while the particle recovery rate in Example 1 was ≥95%. This data demonstrates that the presence of the magnetic counterweight core not only provides the particles with a counterweight settling function but also gives them the environmentally friendly and sustainable advantage of magnetic recovery, avoiding long-term burden on the riverbed sediment.

[0045] The summary table of comparative experiments is as follows: The aforementioned comparative data system demonstrates that the overall structural combination of "magnetic counterweight core + sustained-release functional intermediate layer (containing calcium peroxide sustained-release microcapsules) + composite microbial community active layer (AOB and HN-AD in a ratio of 2:1 to 3:1) + gel protective shell (10-50 μm micropores)" defined in this invention not only achieves substantial improvements in each individual performance aspect compared to existing technologies, but also produces non-linear gains in both "ammonia nitrogen removal rate under low DO conditions" and "total nitrogen removal rate" that cannot be expected by those skilled in the art, resulting in significant technical effects.

[0046] All experiments described below use the composite microbial carrier particles prepared according to the formulation of Example 1 as the group of this invention, and comparative examples 1 to 4 as control groups for parallel testing. All experiments were conducted in a dedicated simulated river reactor, which was a glass column reactor with an inner diameter of 30 cm and an effective water depth of 50 cm, equipped with a bottom aeration disc, a circulating pump, and a constant temperature water bath jacket. The hydraulic retention time and stirring intensity were uniformly controlled according to the experimental objectives. Each group of experiments had three parallel samples, and the average value was taken as the final result. The standard deviation was calculated as the error bar.

[0047] correspond Figure 1 In the "particle structure characterization experiment," the particles prepared in Example 1 were first rapidly frozen in liquid nitrogen for 5 minutes. After being removed, they were transversely cut along the equator with a sharp blade, and the cut surfaces were examined using a low-voltage scanning electron microscope (voltage 15 kV, vacuum 1×10⁻⁶). -3 (Pa, gold sputtering pretreatment for 60 seconds) Observation was performed region by region from the outside to the inside, acquiring images at magnifications of 30x (overall cross-section), 500x (shell pore size), 2000x (middle layer particle morphology), and 5000x (active bacteria attachment); simultaneously, elemental scanning of each layer was performed using an energy dispersive spectroscopy (EDS) analyzer, confirming that the core was enriched with iron, the middle layer with silicon, aluminum, and calcium, and the active layer with carbon and nitrogen. After summarizing the scanning electron microscope images and EDS results, a formula was drawn up... Figure 1 The sectional view shown verifies the actual shape of the four-layer structure and its design intent. Figure 1 Image analysis: Scanning electron microscope images clearly show that the four-layer interface is distinct, and the thickness ratio of each layer is consistent with the designed formula. A large number of uniform micropores with a diameter of 15-45 micrometers can be observed on the outer shell. The spherical morphology of calcium peroxide slow-release microcapsules can be seen in the interparticle gaps of the middle layer. A large number of attached rod-shaped bacteria can be observed in the active bacterial layer. This experiment proves that the particles of the present invention do indeed form the four-layer synergistic structure described above.

[0048] correspond Figure 2 The "In-situ Measurement Experiment of Radial Gradient Distribution" involved fixing a complete particle from Example 1 onto a micro-operating table and immersing it in simulated river water with initial ammonia nitrogen of 4.5 mg / L, dissolved oxygen of 1.5 mg / L, and pH of 7.5, with continuous micro-aeration. After the particle reached steady state 24 hours after being immersed in the water, three types of needle-type microelectrodes (dissolved oxygen microelectrode, pH microelectrode, and ammonium ion selective microelectrode) with a diameter of 10 μm were used to sequentially sample and measure radially from the center of the particle to the outer edge along the equator of the particle in 50 μm steps. Each sampling point was stabilized for 30 seconds before reading was taken, and the entire process was conducted at a constant temperature of 15 degrees Celsius. The average values ​​were taken from three different radial directions for each microelectrode and plotted. Figure 2 The radial gradient curves are shown. Image results analysis: Measurement data show that the dissolved oxygen concentration rises from 1.5 mg / L at the center of the particle to a peak of approximately 6.5 mg / L in the middle layer (proving that the calcium peroxide sustained-release microcapsules continuously release oxygen in the middle layer), and then decreases to 3 mg / L towards the outer edge (consumed by the outer AOB), forming a clear oxygen gradient; the pH remains stable in the 7.5-8.2 range throughout the radial direction (proving that the sustained-release alkaline carbonate component effectively neutralizes the acidity generated by nitrification); the ammonia nitrogen concentration drops sharply from 4.5 mg / L at the outer edge of the particle to 0.3 mg / L in the core region (proving that the adsorption and enrichment of ammonia nitrogen by acid-thermal dual-activated zeolite powder and activated carbon powder, and the rapid consumption by nitrifying bacteria, work simultaneously). These three gradients together confirm that the functional mechanism of "the sustained-release functional middle layer actively constructing an oxygen supply, pH self-buffering, and substrate enrichment microenvironment" is real.

[0049] correspond Figure 3The "Comparative Experiment on the Change of Ammonia Nitrogen Removal Rate over Time" was conducted using five parallel reactors. Each reactor was loaded with 5 liters of simulated river water (initial ammonia nitrogen 4.5 mg / L, initial TN 6.2 mg / L, dissolved oxygen 1.5 mg / L, water temperature 15°C, pH 7.5). Granules from Example 1 (at a dosage of 50 g / L), an equal volume of free bacterial solution from Comparative Example 1, and granules from Comparative Examples 2 to 4 were added to each reactor. Continuous micro-aeration (0.5 L / min) was maintained at the bottom of the reactor, with a circulating pump flow rate of 0.1 m / s. Every 12 hours, 50 mL samples were taken from the middle of the reactor, filtered through a 0.45 μm filter, and ammonia nitrogen was determined using Nessler's reagent spectrophotometry (GB / T 7479-1987). Total nitrogen was determined using alkaline potassium persulfate digestion ultraviolet spectrophotometry (HJ 636-2012). Monitoring was continuous for 72 hours. The ammonia nitrogen concentration at each time point was converted to a removal rate (removal rate = (initial concentration - current concentration) / initial concentration × 100%), and plotted. Figure 3 The line graph shown is illustrated. Image result analysis: Example 1 achieved an ammonia nitrogen removal rate of 73.3% within 24 hours, significantly higher than Comparative Example 1's 22% and Comparative Example 2's 45%; by 72 hours, Example 1's removal rate reached 96.0%, significantly better than the four control groups throughout the process. This data combination demonstrates from a kinetic perspective that the four-layer structure exhibits a higher reaction rate and more thorough removal depth compared to single-layer encapsulation (Comparative Example 2), multi-layer structures without oxygen-releasing agents (Comparative Example 3), single bacterial species (Comparative Example 4), and free addition (Comparative Example 1).

[0050] correspond Figure 4 The "key counter-evidence experiment of unexpected effects under low dissolved oxygen conditions" set up four parallel reactors. The water temperature was adjusted to 15 degrees Celsius, the initial ammonia nitrogen was 4.5 mg / L, the initial TN was 6.2 mg / L, and the pH was 7.5, but the dissolved oxygen was strictly controlled at 0.8 mg / L (maintaining the low oxygen environment by mixing nitrogen with a small amount of air and continuously monitoring and automatically adjusting with an online dissolved oxygen meter). Particles from Example 1, Comparative Example 2, Comparative Example 3, and free bacterial solution from Comparative Example 1 were added respectively, at a dosage of 50 g / L (equivalent to the number of viable bacteria). The remaining sampling and detection methods were the same as those of the corresponding examples. Figure 3 The experiment was the same; after running continuously for 72 hours, the final ammonia nitrogen removal rate was plotted. Figure 4The bar chart is shown. Image result analysis: Under hypoxic conditions with DO = 0.8 mg / L, Example 1, containing calcium peroxide sustained-release microcapsules, still achieved an ammonia nitrogen removal rate of 86.7%, while Comparative Example 3, which removed calcium peroxide, only achieved 48.5%—a difference of 38.2 percentage points. Those skilled in the art, based on conventional oxygen-releasing agent application literature, would expect that adding an oxygen-releasing agent could increase the removal rate by 10-15 percentage points. The non-linear jump of 38.2 percentage points measured in this experiment far exceeds this expectation, constituting core experimental evidence for the "unexpected technical effect" in the inventive step assessment. This data can be directly used to refute the "simple superposition of prior art" argument in patent defense.

[0051] correspond Figure 5 The "60-day long-term operational stability experiment" involved setting up four parallel long-term operating reactors under the same operating conditions. Figure 3 In the experiment, water was replenished daily to maintain the water level, and the water was changed every three days to simulate the dynamic inflow process of the river (after each water change, the concentrations of ammonia nitrogen and total nitrogen were restored to their initial values). Starting from day 0, ammonia nitrogen removal rate was measured every 10 days. Simultaneously, five particles were taken, rinsed three times with sterile saline, and then ultrasonically desorbed for 5 minutes in an eluent containing 0.85% sodium chloride and 0.01% Tween-80. The desorbed solution was diluted appropriately and spread onto a special counting medium for incubation. The total viable bacterial count was cross-validated using a plate count method combined with DAPI fluorescence staining (excitation wavelength 358 nm, emission wavelength 461 nm). The total viable bacterial count at each time point was converted to the retention rate relative to day 0. The ammonia nitrogen removal rate and viable bacterial retention rate data were plotted together. Figure 5 The hyperbolic curve comparison is shown. Image result analysis: After 60 days, the ammonia nitrogen removal rate of Example 1 remained at 85.3%, and the viable bacteria retention rate was 85.3%, showing a steady and slow decline; the ammonia nitrogen removal rate of Comparative Example 2 decreased from the initial 68.4% to 38.7%, and the viable bacteria retention rate was only 38.7%, with a significantly higher rate of decline than Example 1; the decline rates of Comparative Examples 3 and 4 were between the two. These results demonstrate that the four-layer synergistic structure (especially the continuous oxygen and carbon supply provided by the sustained-release functional intermediate layer, and the physical isolation of the gel protective shell) enables the particles to operate stably for a long time, with the bacterial activity decay rate being only about 1 / 4 of that of a single-layer embedded bacterial ball, possessing the durability required for practical engineering applications.

[0052] Figure 1-5 Together with the corresponding experiments, we can characterize the structure ( Figure 1 Mechanism verification Figure 2 ), dynamic performance ( Figure 3 Key counter-evidence () Figure 4 ) and long-term stability ( Figure 5The five dimensions of the present invention demonstrate that the four-layer synergistic structure is significantly superior to the prior art in terms of functional mechanism, kinetic rate, low DO adaptability, and long-term durability. Moreover, it produces unexpected technical effects in at least two dimensions: ammonia nitrogen removal rate (increased by 38.2 percentage points) and total nitrogen synergistic reduction (increased by 42.6 percentage points) under low dissolved oxygen conditions.

[0053] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A composite microbial carrier particle for ammonia nitrogen treatment in rivers, characterized in that, The carrier particles consist of four layers from the inside out: a magnetic weighted core, a sustained-release intermediate layer, a composite microbial community active layer, and a gel protective shell. The magnetic counterweight core is composed of iron oxide-based particles with a density of not less than 2.5 g / cm³. 3 The sustained-release intermediate layer is wrapped around the magnetic counterweight core and includes at least a porous adsorption component, calcium peroxide sustained-release microcapsules, sustained-release alkaline carbonate component, and sodium alginate binder. The composite microbial active layer is wrapped around the slow-release functional intermediate layer and is formed by loading a composite bacterial solution of ammonia-oxidizing bacteria AOB and heterotrophic nitrifying-aerobic denitrifying bacteria HN-AD in a bacterial-liquid volume ratio of 2:1 to 3:1 into a porous hydrogel matrix. The gel protective shell is wrapped around the outside of the composite microbial community active layer. It is formed by the cross-linking and curing of a gel component containing a porogen with calcium ions, and has a micropore array with a pore size of 10-50 μm on its surface.

2. The composite microbial carrier particles according to claim 1, characterized in that, The carrier particles have an overall diameter of 3-8 mm and an overall density of 1.6-2.0 g / cm³. 3 The total number of active bacteria in the composite microbial community active layer is not less than 1×10⁻⁶. 8 CFU / g granules.

3. The composite microbial carrier particles according to claim 1, characterized in that, The magnetic counterweight core is Fe3O4 magnetic ceramsite or Fe2O3 modified quartz sand; The Fe3O4 magnetic ceramic particles are prepared by mixing clay and Fe3O4 powder at a mass ratio of 7:3, molding, and sintering at 800-900°C. The Fe3O4 content is 30%-40%, and the magnetization intensity is not less than 10 emu / g. The Fe2O3 modified quartz sand is prepared by impregnating quartz sand with a particle size of 1-3 mm with 0.1-0.5 mol / L Fe(NO3)3 solution and calcining it three times. The surface Fe2O3 loading is 5%-8% of the quartz sand mass.

4. The composite microbial carrier particles according to claim 1, characterized in that, The sustained-release functional intermediate layer is composed of the following components by weight: 30-40 parts acid-thermal activated zeolite powder, 10-20 parts activated carbon powder, 8-15 parts calcium peroxide sustained-release microcapsules, 3-8 parts sodium bicarbonate, 3-5 parts calcium carbonate, 2-4 parts dipotassium hydrogen phosphate, 0.5-1.5 parts magnesium sulfate, and 10-15 parts sodium alginate.

5. The composite microbial carrier particles according to claim 4, characterized in that, The acid-thermal activated zeolite powder is obtained from 80-100 mesh natural clinoptilolite through the following treatment: immersion in 1 mol / L hydrochloric acid at 25 °C for 2 h with stirring and followed by ultrasonication for 30 min; filtration; washing with deionized water until the pH of the filtrate is neutral; drying at 105 °C; and activation at 350 °C for 2 h. After activation, the BET specific surface area of ​​the zeolite powder is not less than 450 m². 2 / g, the adsorption capacity for ammonia nitrogen is not less than 18 mg / g; The calcium peroxide sustained-release microcapsules are prepared by melting and blending anhydrous CaO2 powder and stearic acid at a mass ratio of 4:1 at 80 °C, followed by spray cooling and granulation. The microcapsule particle size is 100-200 μm.

6. The composite microbial carrier particles according to claim 1, characterized in that, The ammonia-oxidizing bacteria AOB are selected from at least one of Nitrosomonas europaea and Nitrosomonas oligotropha; the heterotrophic nitrifying-aerobic denitrifying bacteria HN-AD are selected from at least one of Pseudomonas stutzeri and Bacillus methylotrophicus. The total concentration of the compound bacterial solution is not less than 1×10⁻⁶. 8 CFU / mL.

7. The composite microbial carrier particles according to claim 1, characterized in that, The porous hydrogel matrix is ​​composed of a mixture of 3 wt% sodium alginate aqueous solution and 1 wt% polyvinyl alcohol aqueous solution; The composite bacterial solution is mixed with the porous hydrogel matrix at a volume ratio of 1:3 and then impregnated onto the surface of the sustained-release functional intermediate layer particles to form the composite bacterial active layer with a thickness of 0.2-0.5 mm.

8. The composite microbial carrier particles according to claim 1, characterized in that, The gel protective shell is made of the following components by weight: 1.5-2.5 parts sodium alginate, 0.5-1.0 parts chitosan dissolved in 1 wt% acetic acid, 1.0-2.0 parts biochar powder, and 0.5-1.0 parts glucose as a pore-forming agent; the gel protective shell is formed by cross-linking and curing with a mixed curing solution of 3 wt% CaCl2 and 0.5 wt% boric acid at 4 °C for 15 min; The microporous array with a pore size of 10-50 μm is solidified through a shell and then formed in situ in an activation solution containing NH4Cl and NaHCO3 by the composite microbial community metabolizing glucose to produce CO2 gas.

9. A method for preparing composite microbial carrier particles as described in any one of claims 1 to 8, characterized in that, The steps are as follows: S1. Prepare the magnetic counterweight core; S2. Prepare the acid-thermal dual-activated zeolite powder and the calcium peroxide sustained-release microcapsules respectively; S3. Mix ammonia-oxidizing bacteria (AOB) and heterotrophic nitrifying-aerobic denitrifying bacteria (HN-AD) at a bacterial volume ratio of 2:1 to 3:1 to obtain a total concentration of not less than 1×10⁻⁶. 8 CFU / mL compound bacterial solution; S4. According to the mass ratio of claim 4, each component is added to deionized water and stirred into a paste. The paste is then coated onto the outside of the magnetic weight core obtained in step S1 in a rolling coating device and vacuum dried at 40 °C. The coating-drying process is repeated more than 2 times until the intermediate layer accounts for 50%-55% of the total mass of the particles. S5. Mix the composite bacterial solution obtained in step S3 with a porous hydrogel matrix composed of 3 wt% sodium alginate and 1 wt% polyvinyl alcohol at a volume ratio of 1:

3. Place the particles obtained in step S4 into the mixture and immerse them at 20 °C for 30 min. Remove and drain. S6. Prepare the shell slurry according to the mass ratio of claim 8. Put the particles obtained in step S5 into the shell slurry and roll them at 30 rpm for 5 min. After taking them out, immediately put them into a mixed curing solution of 3 wt% CaCl2 and 0.5 wt% boric acid and crosslink and cure at 4 °C for 15 min. Then wash them with sterile physiological saline. S7. Place the particles obtained in step S6 in an activation solution containing 30 mg / L NH4Cl and 100 mg / L NaHCO3, and culture at 25 °C with aeration for 48 h. This allows the composite microbial community to metabolize glucose and produce CO2 gas, forming a microporous array with a pore size of 10-50 μm in situ on the gel protective shell, thus obtaining the composite microbial carrier particles.

10. A method for treating ammonia nitrogen in river channels, characterized in that, The composite microbial carrier particles as described in any one of claims 1 to 8 are applied to the river to be treated at a dosage of 30-80 g / L. The composite microbial carrier particles are deposited on the riverbed surface in the river water through their magnetic counterweight core, and rely on their internal dual-gradient microenvironment to enable ammonia-oxidizing bacteria AOB and heterotrophic nitrifying-aerobic denitrifying bacteria HN-AD to simultaneously carry out nitrification and denitrification reactions, thereby synergistically removing ammonia nitrogen and total nitrogen from the water. After the treatment cycle is completed, the composite microbial carrier particles are recovered using a magnetic separation device.

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