Composite ecological filler for enhancing in-situ denitrification of river water body, percolation system and application

Abstract

The invention relates to a composite ecological filler for enhancing in-situ denitrification of a river water body, a percolation system and application. The composite ecological filler is composed of an anoxic denitrification filler and a transition regulation filler or composed of an aerobic nitrification filler, an anoxic denitrification filler and a transition regulation filler; the aerobic nitrification filler comprises an inorganic mineral matrix denitrification filler, biological ceramsite, a mineral-based slow-release functional material and a microbial immobilization functional carrier; the anoxic denitrification filler comprises a sulfur-based composite electron donor material, a slow-release organic carbon source material, a zero-valent iron-based environmental remediation material and denitrifying bacterium embedding gel; the transition regulation and control filler comprises a multifunctional water treatment filter material, activated carbon and an environment response type functional microbial carrier. The invention also provides application of the composite ecological filler and a percolation system, solves the problem that the traditional denitrification filler cannot cooperatively support nitrification / denitrification due to single function, and also solves the problem that the fixed ratio of the traditional denitrification filler is difficult to adapt to dynamic fluctuation of water quality.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a composite ecological filler for enhancing in-situ denitrification of river water, a percolation system and applications. Background Art

[0002] Biological denitrification technology is widely used for its cost-effectiveness in the treatment of nitrogen pollution in water bodies, particularly in wastewater treatment and constructed wetlands. The essence of this technology lies in the precise execution of two biochemical steps, nitrification and denitrification, by microorganisms under specific conditions, effectively converting nitrogenous pollutants into harmless nitrogen gas. The performance of the filler, which serves as a carrier for microbial attachment and a platform for the reaction, directly impacts the system's denitrification efficiency and operational stability.

[0003] Currently, traditional denitrification fillers, such as volcanic rock and zeolite, exhibit significant limitations in their application. Their relatively limited functionality, often limited to excellent physical adsorption capacity or specific chemical properties (e.g., ion exchangeability in zeolite), makes them incapable of meeting the dynamic microenvironmental requirements of aerobic nitrification and anoxic denitrification. Nitrification requires an adequate dissolved oxygen (DO) environment, while denitrification requires anoxic or even anaerobic conditions. Traditional fillers are unable to effectively regulate or adapt to this dynamically changing DO environment, limiting their overall denitrification efficiency. Due to the adaptability limitations of fixed mixes, multiple fillers are often combined in fixed volume or mass ratios in an attempt to address different processes. However, in real water bodies, DO levels often fluctuate significantly (e.g., from a low oxygen state of 0.5 mg / L to a high oxygen state of 8 mg / L), and the forms of nitrogen pollutants in the influent (e.g., the relative ratio of NH₃-N to NO₃-N) can also change frequently. Faced with these dynamically changing water quality conditions (DO fluctuations, varying nitrogen form ratios), fixed-ratio filler systems exhibit significant adaptability issues, with denitrification efficiency typically dropping significantly by 30% to 50% compared to ideal or stable conditions. This results in unstable effluent quality and makes operational effectiveness difficult to guarantee. Constructed wetland fillers lack empirical reliance and control. In constructed wetland systems, filler selection and ratios rely heavily on engineering experience and limited experimental data, lacking a scientific and precise dynamic control mechanism based on real-time or periodic monitoring of water quality parameters (such as DO, NH3-N, NO3-N, pH, and temperature). This "static" filler configuration model is unable to respond to the complex and changing hydraulic conditions within the wetland, pollutant load fluctuations, and seasonal changes in environmental parameters. This leads to significant fluctuations in treatment efficiency and makes it difficult to achieve stable and efficient denitrification goals.

[0004] In summary, the main problems faced by existing denitrification filler technologies, especially when applied to dynamic water environments, are: single functionality leading to an inability to synergistically support nitrification / denitrification; fixed ratios making it difficult to adapt to dynamic fluctuations in water quality (DO, nitrogen form); direct addition of liquid carbon sources easily leading to COD exceeding standards; and a lack of intelligent control capabilities based on water quality feedback. These shortcomings significantly hinder the efficient operation, stable performance, and adaptability of denitrification systems. Therefore, there is an urgent need to develop a new type of composite filler with multifunctional synergy, the ability to adapt to environmental changes, or the ability to be intelligently and dynamically controlled based on water quality parameters, as well as its application method, to significantly improve denitrification performance and operational stability under complex dynamic water conditions and meet increasingly stringent ecological restoration requirements. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a composite ecological filler, a filtration system and an application for enhancing in-situ denitrification of river water bodies, so as to solve the problem that traditional denitrification fillers have a single function and cannot synergistically support nitrification / denitrification. It can also solve the problem that the fixed ratio of traditional denitrification fillers is difficult to adapt to the dynamic fluctuations of water quality (DO, nitrogen form). It can also solve the problem that the direct addition of liquid carbon source to traditional denitrification fillers easily leads to COD exceeding the standard and lacks intelligent control capabilities based on water quality feedback.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A composite ecological filler for enhancing in-situ denitrification of river water bodies, consisting of anoxic denitrification filler (Type B filler) and transition control filler (Type C filler) or consisting of aerobic nitrification filler (Type A filler), anoxic denitrification filler (Type B filler) and transition control filler (Type C filler); The aerobic nitrification filler includes an inorganic mineral matrix denitrification filler, biological ceramsite, a mineral-based slow-release functional material and a microbial immobilization functional carrier; The anoxic denitrification filler comprises a sulfur-based composite electron donor material, a slow-release organic carbon source material, a zero-valent iron-based environmental remediation material, and a denitrifying bacteria embedding gel; The transition control filler includes multifunctional water treatment filter material, activated carbon and environmentally responsive functional microbial carrier.

[0007] According to the above technical means, by cleverly selecting inorganic mineral matrix denitrification fillers, biological ceramsite, mineral-based slow-release functional materials and microbial immobilization functional carriers as aerobic nitrification fillers, sulfur-based composite electron donor materials, slow-release organic carbon source materials, zero-valent iron-based environmental remediation materials and denitrifying bacteria embedded gels as anoxic denitrification fillers, sulfur-based composite electron donor materials, slow-release organic carbon source materials, zero-valent iron-based environmental remediation materials and denitrifying bacteria embedded gels as transitional control fillers, thereby mixing to form a composite ecological filler for in situ denitrification of river water bodies, through the synergistic effect of aerobic nitrification fillers, anoxic denitrification fillers and transitional control fillers or anoxic denitrification fillers and transitional control fillers, anoxic zones are formed under high DO, thereby achieving efficient connection between nitrification and denitrification processes and solving the problem of single function of traditional fillers. Moreover, through the synergy of transition control fillers and anoxic denitrification fillers, it can automatically adjust the microbial community and organic carbon source supply according to the dynamic changes of water quality (such as dissolved oxygen, nitrogen form, etc.), adapt to water quality fluctuations, and have intelligent control capabilities based on water quality feedback, avoiding the COD exceeding the standard problem caused by the fixed ratio and direct addition of liquid carbon source of traditional fillers, thereby significantly improving the denitrification efficiency and the stability and adaptability of the system.

[0008] Among them, traditional denitrification materials fail to meet the following requirements simultaneously: 1) Construction of anoxic microenvironment: It is difficult to form the anoxic zone required for denitrification under high dissolved oxygen conditions; 2) Slow-release carbon source supply: Direct addition of liquid carbon source can easily lead to COD exceeding the standard; 3) Targeted enrichment of functional bacteria: The synergistic effect of nitrification / denitrification bacteria requires differentiated carrier support.

[0009] The present invention systematically solves the above three technical problems through the following innovative designs, as follows: 1. Strategy for constructing a hypoxic microenvironment (forming a hypoxic zone under high DO) Oxidative oxygen consumption mechanism of zero-valent iron-based environmental remediation materials: When zero-valent iron-based environmental remediation materials [such as sponge iron (FeO)] are added to the anoxic denitrification filler, they undergo an oxidation reaction with dissolved oxygen in the water (4FeO + 3O2+ 6H2O → 4Fe(OH)3). This process rapidly consumes local DO (0.43 mg DO can be consumed per gram of FeO), forming anoxic micro-zones with DO ≤ 0.5 mg / L between the filler particles.

[0010] Synergistic effect of sulfur autotrophic denitrification: Sulfur-based composite electron donor materials [such as sulfur particles (S)] and denitrifying bacteria constitute a sulfur autotrophic denitrification system (55S + 20NO3⁻ + 38H2O → 5S2O3²⁻ + 4N2 + 76H + ), this reaction does not require an organic carbon source and can achieve an anoxic environment through micro-area isolation in high DO mainstream water bodies.

[0011] Particle size gradient design: Sulfur-based composite electron donor materials [sulfur particles (0.5-1mm)] and zero-valent iron-based environmental remediation materials [sponge iron (2-3mm)] form a layered stacking structure. The pores inside the large particles form a diffusion-restricted anoxic zone. Actual measurements have shown that this structure can reduce the DO concentration in the micro-area by 80% compared to the main water body.

[0012] 2. Accurate supply of slow-release carbon source (to avoid COD exceeding the standard) Multi-stage sustained-release technology: Physical slow release: Slow-release organic carbon source materials [such as lignin carbon source balls] control the release rate through pore diffusion (release half-life 15 to 20 days), and their surface hydroxyl and carboxyl functional groups can adsorb excess carbon sources.

[0013] Chemical slow release: Slow-release organic carbon source materials [such as polycaprolactone (PCL)] gradually release small molecular organic matter through ester bond hydrolysis, and the release rate is ≤0.2mg C / (g·h) at a water temperature of 10°C.

[0014] Bioresponsive release: The α-1,4 glycosidic bonds in slow-release organic carbon source materials [such as starch-based gels] are specifically decomposed by amylases secreted by denitrifying bacteria, achieving on-demand release of the carbon source.

[0015] Dynamic C / N control: For example, when COD / N is less than 4, by increasing the proportion of slow-release carbon sources (30-40%) and selecting C / N adjustable starch-based gel (C / N=5-8), the carbon source required for denitrification can be ensured while controlling the COD increase to ≤15%.

[0016] 3. Targeted enrichment technology of functional bacteria Differentiated carrier design: Aerobic zone filled with aerobic nitrifying filler: microbial immobilization functional carrier, such as polyurethane foam (porosity > 90%) loaded with nitrifying bacteria immobilization carrier, the surface amino modification can specifically adsorb Nitrosomonas (adsorption capacity up to 10^8 CFU / g).

[0017] Filling anoxic zone with anoxic denitrification filler: denitrifying bacteria embedding gel adopts sodium alginate-Ca 2+ The cross-linked network and the reducing environment within the gel (ORP < -100 mV) promoted the enrichment of Pseudomonas denitrificans (abundance increased 3-fold).

[0018] The transition zone of the transition control filler is filled: the redox potential (ORP) sensitive bacterial agent carrier, such as Fe3O4 / magnetic biochar carrier, realizes the directional fixation of ORP sensitive bacterial agent through magnetic response, and activates the sulfur autotrophic denitrification function when ORP>200mV.

[0019] Cross-module collaboration mechanism: ORP signal conduction: Fe3O4 in the transition control filler can sense ORP changes in real time (sensitivity ±10mV). 2+ / Fe 3+ Valence state transitions trigger functional activation of adjacent modules.

[0020] Quorum sensing regulation: The C6-HSL signaling molecules (threshold concentration 10nM) released by nitrifying bacteria can induce the activation of the quorum sensing system of denitrifying bacteria, thereby achieving metabolic synchronization of the bacterial community.

[0021] A / B / C type fillers achieve cross-module synergy through ORP and microbial signal molecules Cross-module transmission and response of ORP signals (1) ORP sensing and control of type C fillers The redox potential (ORP) sensitive carriers in the C-type filler (such as Fe3O4 / magnetic biochar, pyrite) can sense the ORP value of the water in real time. For example: When ORP>200mV (aerobic conditions), Fe 3+ The valence state conversion of / Fe²⁺ triggers the release of electron acceptors (such as Mn 4 ⁺), activate the short-range nitrifying bacteria (such as Nitrosomonas) in Class A filler, and quickly convert NH3-N into NO2⁻-N instead of completely oxidizing it to NO3⁻-N (saving 60% of oxygen consumption).

[0022] When ORP < 0mV (anoxic conditions), the oxidation reaction of pyrite (FeS2) (FeS2 + 7H2O → Fe²⁺ + 2SO4²⁻ + 14H⁺ + 14e⁻) releases electrons, driving the sulfur autotrophic denitrification (Thiobacillus denitrificans) in the B-type filler to directly reduce NO3⁻-N to N2, bypassing the carbon source dependence of traditional denitrification.

[0023] (2) ORP feedback adjustment of A / B type packing Steel slag in type A filler (releasing Fe 3+ ) and B-type filler sponge iron (Fe 0 ) forms a redox gradient: In the Class A area, Fe³⁺ consumes local DO through the Fenton reaction (Fe²⁺ + H2O2 → Fe³⁺ + OH⁻ + ·OH), reduces the ORP, and creates a pre-anoxic environment for the adjacent Class B area (DO drops from 4 mg / L to 1.5 mg / L).

[0024] In the Class B region, Fe 0 Fe produced by corrosion 2+ (Fe0 + 2H2O → Fe 2+ + H2↑ + 2OH - ) further reduces the ORP to below -150mV, activating the nitrate reductase activity of denitrifying bacteria.

[0025] 2. Quorum sensing and metabolic coordination of microbial signaling molecules Signal molecule release from type A fillers Nitrifying bacteria (such as Nitrosomonas) in type A fillers secrete acyl homoserine lactones (AHLs, such as C6-HSL) during metabolism. When the concentration reaches 10 -8 When the concentration of nitrate is too high, the denitrifying bacteria (such as Pseudomonas) in the B-type filler are triggered to activate the quorum sensing system, upregulating the expression of nitrate reductase (narG) and nitrite reductase (nirS) genes, thereby increasing the denitrification rate. Simultaneously, ORP-sensitive bacteria (such as Thiobacillus) in the C-type filler are induced to secrete extracellular polymeric substances (EPS), enhancing the ability of the bacteria to adhere to the carrier surface.

[0026] Metabolite feedback of B / C type fillers The N2O and CO2 produced during the denitrification process of the B-type filler will diffuse into the C-type filler. N2O acts as a signal molecule to activate the anaerobic ammonia-oxidizing bacteria (Anammox) in the C-type carrier, prompting it to utilize NH4⁺ and NO2 - Directly generate N2 (NH4⁺ + NO2⁻ → N2↑ + 2H2O), reducing the accumulation of intermediate products. CO2 stimulates the proton-coupled electron transfer reaction of C-type manganese sand (MnO2) by reducing the local pH (from 7.5 to 6.8) (MnO2 + 4H⁺ + 2e⁻ → Mn 2 ⁺ + 2H2O), accelerating the oxidation and removal of NO2⁻-N.

[0027] The final effect achieved is as follows: Nitrogen removal efficiency increased: the total nitrogen removal rate increased from 45% of traditional fillers to 92%, of which short-range nitrification-anaerobic ammonium oxidation (PD / A) contributed 35% and sulfur-iron autotrophic denitrification contributed 57%.

[0028] Enhanced dynamic adaptability: When DO suddenly changes (e.g., 4→1 mg / L), the metabolic pathway switches from full nitrification to short-range denitrification within 30 minutes through the ORP signal; when COD / N fluctuates, the enzyme response release of the starch-based gel increases the carbon source addition accuracy to ±5%, reducing the risk of COD exceeding the standard by 90%.

[0029] Optimization of functional bacterial community stability: nitrifying bacteria biofilm density reaches 1.2×10 10CFU / g (traditional carriers only 3×10 9 CFU / g), and the ability to resist hydraulic erosion increased by 4 times; the interspecific electron transfer efficiency of denitrifying bacteria increased by 60%, avoiding the accumulation of intermediate products (NO2⁻, N2O), and the N2 selectivity reached 98%.

[0030] Preferably, the inorganic mineral matrix denitrification filler is selected from at least one of volcanic rock, zeolite, diatomaceous earth and steel slag.

[0031] Among them, zeolite has the advantage of adsorbing NH3-N compared with volcanic rocks; diatomaceous earth has the advantage of high specific surface area compared with volcanic rocks; steel slag has the advantage of releasing Fe compared with volcanic rocks. 3+ The advantage of promoting nitrification.

[0032] Preferably, the volcanic rock is selected from porous basalt.

[0033] Preferably, the mineral-based sustained-release functional material is selected from at least one of magnesium ammonium phosphate sustained-release spheres, calcium carbonate-coated sustained-release particles (pH buffering) and hydroxyapatite (simultaneous phosphorus control).

[0034] Among them, ammonium magnesium phosphate slow-release balls are a type of slow-release fertilizer with ammonium magnesium phosphate (NH4MgPO4·6H2O) as the core ingredient. They are usually made into spherical particles. By controlling the nutrient release rate, they improve fertilizer utilization and reduce environmental pollution.

[0035] Preferably, the microorganism immobilization functional carrier is selected from at least one of a nitrifying bacteria immobilization carrier, polyurethane foam (porosity>90%) and sodium alginate-montmorillonite composite gel (low temperature resistant).

[0036] Preferably, the sulfur-based composite electron donor material is selected from sulfur particles, pyrite (FeS2, which also provides Fe 2+ ) and sodium thiosulfate sustained-release balls (suitable for low temperatures).

[0037] Preferably, the slow-release organic carbon source material is selected from at least one of lignin carbon source balls, polycaprolactone (PCL, a degradable polymer carbon source) and starch-based gel (C / N adjustable).

[0038] Preferably, the zero-valent iron-based environmental remediation material is selected from at least one of sponge iron, zero-valent iron powder (with a larger specific surface area) and iron-carbon micro-electrolysis filler (Fe / C mass ratio of 1:2).

[0039] Sponge iron, a type of direct reduced iron (DRI), is a porous iron product obtained by removing oxygen from iron ore (such as hematite or magnetite) using a reducing gas (such as hydrogen, carbon monoxide, or natural gas) or a solid reducing agent (such as coal) at high temperatures (usually below the melting point of iron). Its porous, sponge-like structure gives it the name "sponge iron."

[0040] Preferably, the zero-valent iron powder is selected from nano zero-valent iron.

[0041] Preferably, the multifunctional water treatment filter material is selected from at least one of manganese sand, titanium dioxide coated ceramsite (photocatalytically assisted denitrification) and aluminum oxide (NH3-N adsorption).

[0042] Among them, manganese sand is often expressed as MnO2·xH2O (containing crystal water), where x is a positive integer. The main components of manganese sand are manganese dioxide (MnO2), iron oxide (Fe2O3) and silicate minerals. Manganese dioxide (MnO2): The content is usually ≥35% (high-quality manganese sand can reach more than 45%), which is the active component for oxidizing and removing iron and manganese ions. Iron oxide (Fe2O3): A natural accompanying component (5~15%) that assists in catalysis. Silicate minerals: such as quartz (SiO2), feldspar, etc. (20~40%), provide structural support. Manganese sand is regenerated through periodic aeration treatment (Mn 2+ Converted to Mn 4+ ), this mechanism extends its service life by more than 3 times.

[0043] Preferably, the environmentally responsive functional microbial carrier is selected from at least one of an oxidation-reduction potential (ORP)-sensitive bacterial agent carrier, a pH-responsive bacterial community (such as Nitrosomonas activated when pH>7) carrier, and a DO gradient-sensing biofilm carrier.

[0044] Preferably, the aerobic nitrification filler comprises, by mass percentage, 50-70% of volcanic rock, 20-30% of biological ceramsite, 5-10% of magnesium ammonium phosphate slow-release balls and 5-10% of nitrifying bacteria immobilization carriers.

[0045] By cleverly setting the composition and ratio of aerobic nitrification fillers, the conversion of NH3-N to NO3⁻-N can be effectively promoted under high DO conditions, and magnesium ammonium phosphate provides alkalinity buffering.

[0046] Preferably, the anoxic denitrification filler comprises, by mass percentage, 30-45% sulfur particles, 15-30% lignin carbon source balls, 35-45% sponge iron and 5-15% denitrifying bacteria embedding gel.

[0047] Among them, sponge iron creates a low DO environment and effectively drives the conversion of NO3⁻-N→N2.

[0048] Preferably, the transition control filler comprises, by mass percentage, 50% manganese sand, 30% coconut shell activated carbon and 20% oxidation-reduction potential (ORP) sensitive bacterial agent carrier.

[0049] Dynamic adjustment of NH3-N / NO3 according to ORP - -N ratio, thus effectively adapting to DO mutation scenarios.

[0050] Preferably, when DO≥4 mg / L and NH3-N / NO3 - When -N>1, the composite ecological filler consists of 70-80% aerobic nitrification filler, 10-15% anoxic denitrification filler and 5-10% transition control filler.

[0051] Preferably, when DO≤2 mg / L and NO3 - When -N≥5 mg / L, the composite ecological filler consists of 10-20% aerobic nitrification filler, 60-70% anoxic denitrification filler and 15-20% transition control filler.

[0052] Preferably, when the DO change per hour is greater than 2 mg / L, the composite ecological filler is composed of 25% aerobic nitrification filler, 25% anoxic denitrification filler and 50% transition control filler.

[0053] Among them, when the composite ecological filler is composed of aerobic nitrification filler, anoxic denitrification filler and transition control filler, it is suitable for river water bodies with a temperature greater than or equal to 10°C.

[0054] Preferably, when the water temperature of the river is less than 10°C and NO3 - When -N≥5 mg / L, the composite ecological filler consists of anoxic denitrification filler and transition control filler, and the mass percentage of the anoxic denitrification filler in the composite ecological filler is 10-15%.

[0055] Preferably, when the COD / N ratio of the river water body is less than 4, the mass percentage of the slow-release organic carbon source material in the anoxic denitrification filler is 30-40%.

[0056] By comprehensively considering the concentrations of DO, NH3-N, NO3-N and temperature conditions, the filler ratio is carefully selected, thereby significantly improving the denitrification efficiency.

[0057] Preferably, the bioceramic pellets are selected from at least one of clay ceramic pellets, fly ash ceramic pellets, shale ceramic pellets, coal gangue ceramic pellets and bio-sludge ceramic pellets.

[0058] Preferably, the nitrifying bacteria immobilization carrier is selected from at least one of clay ceramsite, shale ceramsite, natural zeolite, activated zeolite, pyrolysis biochar, polyvinyl alcohol immobilization beads, modified polyvinyl alcohol, open-cell PU foam and bacterial cellulose membrane.

[0059] Nitrifying bacteria immobilization carrier is a functional material specially used to fix and enrich nitrifying bacteria (such as Nitrosomonas, Nitrobacter, etc.). Its core function is to provide a stable attachment environment for nitrifying bacteria and optimize their growth and metabolic conditions, thereby improving the efficiency of biological denitrification.

[0060] The preparation method of modified polyvinyl alcohol (PVA) comprises the following steps: ① Prepare a PVA / SA mixed aqueous solution with a mass ratio of 7:3. The total concentration of PVA and SA in the mixed aqueous solution is 8%. Then, stir the mixed aqueous solution at a constant temperature of 60°C for 10 minutes. ② The mixed aqueous solution was dripped into a CaCl2 solution with a step-by-step concentration through a microfluidic device. The step-by-step concentration of the CaCl2 solution included 0.5 mol / L, 1.0 mol / L, and 2.0 mol / L, respectively. Each step was cured for 15 minutes to form a heterogeneous structure with a dense shell and a loose core, thereby obtaining modified polyvinyl alcohol.

[0061] By adopting the sodium alginate (SA) blend-calcium chloride gradient solidification method, namely the gradient Ca²⁺ diffusion solidification technology, the bacterial loading capacity was effectively increased. According to experimental measurements, the adsorption capacity of modified polyvinyl alcohol for nitrifying bacteria (Nitrosomonas) reached 4.8×10 8 CFU / g, 3 times higher than that of homogeneous carrier.

[0062] Preferably, the lignin carbon source balls are selected from at least one of enzymatically hydrolyzed lignin carbon balls, lignin sulfonate carbon balls and industrial lignin carbon balls.

[0063] Lignin carbon source spheres are porous carbon spheres made from lignin (a natural polymer found in plant cell walls) through a specialized process. These materials possess a high surface area, a controllable pore structure, and a rich array of surface functional groups, making them suitable for a wide range of applications in energy storage, environmental remediation, and catalytic conversion.

[0064] Preferably, the denitrifying bacteria embedding gel is at least one selected from sodium alginate (SA)-calcium chloride gel, chitosan-based gel, starch-PVA composite gel, polyvinyl alcohol (PVA)-boric acid gel and polyurethane (PU) hydrogel.

[0065] Denitrifying bacteria embedded gel is a functional material that fixes denitrifying bacteria (such as Pseudomonas, Paracoccus, etc.) in a polymer gel network through microencapsulation technology. It aims to improve denitrification efficiency and solve problems such as carbon source utilization and bacterial loss in traditional biological denitrification.

[0066] Preferably, the oxidation-reduction potential (ORP) sensitive bacterial agent carrier is selected from at least one of Fe3O4 / Fe2O3 gel, magnetic biochar and iron-sulfur minerals (such as pyrite).

[0067] Oxidation-reduction potential (ORP)-sensitive bacterial agent carriers are intelligent biomaterial carriers that can respond to changes in the environmental ORP and dynamically regulate the activity of functional microorganisms. Through material design, these carriers sense and respond to the redox potential in water or soil, thereby optimizing the metabolic environment of microorganisms (such as denitrifiers and anaerobic ammonium oxidizers) and improving pollutant removal efficiency.

[0068] Preferably, the particle size of the sulfur particles is 0.5-1 mm.

[0069] Preferably, the particle size of the sponge iron is 2-3 mm.

[0070] Through the design of the particle size gradient of sulfur particles and sponge iron, that is, the difference in particle size between sulfur particles (0.5-1mm) and sponge iron (2-3mm), a pore gradient structure and a layered reaction zone are formed. Small-sized sulfur particles provide a high specific surface area, accelerating the electron transfer of sulfur autotrophic denitrification; large-sized sponge iron particles form a micro-electrolysis environment (Fe 0 →Fe 2+ ), while its loose accumulation reduces water short-circuiting and prolongs hydraulic retention time (HRT).

[0071] The particle size gradient design of sulfur particles and sponge iron has the following advantages: Co-denitrification: Sulfur (S 0 ) as an electron donor with sponge iron (Fe 0 ) is coupled with the micro-electrolysis reaction (S / Fe molar ratio 1:2) to simultaneously drive chemical denitrification (S 0 →SO4 2- ) and biological denitrification (Fe 2+ →Fe 3+ ), the total nitrogen removal rate increased by 30%-45%.

[0072] DO regulation: Sponge iron corrosion consumes dissolved oxygen (DO), forming anoxic micro-zones with ORP < -50mV on the sulfur surface, overcoming the inhibition of high dissolved oxygen (>4 mg / L) on denitrification.

[0073] Anti-clogging: The particle size gradient forms multi-level pores (sulfur fills the gaps between large particles), increasing the flux by 2.3 times.

[0074] A / B type filler combined replacement: Type A filler surface loaded with Fe 3+ (Promote short-range nitrification), specifically: immerse the biological ceramsite in a FeCl3 solution with a concentration of 0.1 mol / L, and calcine it at 400°C for 2 hours to form an Fe2O3 coating on the surface with a loading capacity of 5%~8% (w / w), thereby directional adsorption of ammonia oxidizing bacteria (AOB) and shortening the nitrification startup period by 40%.

[0075] Adding anaerobic ammonium-oxidizing bacteria (Anammox) to Class B fillers can achieve low-carbon denitrification: Anammox bacteria use NH4⁺ as an electron donor and NO2⁻ as an electron acceptor to directly generate N2 without the need for an additional carbon source, reducing the COD / N requirement from 4~6 of traditional denitrification to 0.5.

[0076] Co-metabolism: coupled with sulfur autotrophic denitrification (S 0 →SO4 2- Provide part of NO2⁻), the total nitrogen removal load is increased to 1kg N / (m 3 ·d).

[0077] Function extension of type C filler: Molybdate (to promote nitrate reductase activity) is added. Molybdate (e.g., Na₂MoO₄) is added during the preparation of an environmentally responsive functional microbial carrier with transition-regulated fillers. The specific method involves blending molybdate (0.05%-0.1% w / w) with magnetic biochar (carrier) and high-temperature activation at 600°C in a nitrogen atmosphere to form a Mo-Fe oxide complex. After loading the carrier with denitrifying bacteria (e.g., Pseudomonas), molybdenum acts as a cofactor for nitrate reductase (Nap / Nar), increasing enzyme activity by 2.5-fold. Even at low temperatures (10°C), the denitrification rate reaches 0.8 mg N / (g·h).

[0078] The present invention also provides an application of a composite ecological filler for strengthening in-situ denitrification of river water bodies to in-situ denitrification of river water bodies.

[0079] Among them, when the composite ecological filler is aerobic nitrification filler, anoxic denitrification filler or transitional control filler, it is used to treat river water with high ammonia nitrogen and low nitrate nitrogen. When the composite ecological filler is anoxic denitrification filler or transitional control filler, it is used to treat river water with low temperature and high nitrate nitrogen.

[0080] The present invention also provides a river water infiltration system, comprising the composite ecological filler and filler device for enhancing in-situ denitrification of river water according to the present invention; The packing device comprises a first packing unit, a second packing unit and a third packing unit which are independent of each other; The first filler unit is filled with aerobic nitrification filler, the second filler unit is filled with anoxic denitrification filler, and the third filler unit is filled with transition control filler.

[0081] Beneficial effects of the present invention: The composite ecological filler for enhancing in-situ denitrification of river water bodies of the present invention cleverly combines aerobic nitrification fillers, anoxic denitrification fillers and transition control fillers, and is therefore suitable for both normal temperature and low temperature conditions and can efficiently denitrify surface water with high dissolved oxygen content, low organic pollutant content and nitrate nitrogen as the main pollution characteristic. It has promotion and application value in the field of river water body restoration technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 It is a structural diagram of the packing device; Among them, 1 is the first packing unit; 2 is the second packing unit; 3 is the third packing unit. DETAILED DESCRIPTION

[0083] The following will describe the embodiments of the present invention with reference to preferred embodiments. Those skilled in the art will readily appreciate the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are intended only to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0084] The purpose of the present invention is to provide a composite ecological filler, a filtration system and its application for enhancing in-situ denitrification of river water bodies, so as to solve the problem that traditional denitrification fillers have a single function and cannot synergistically support nitrification / denitrification. It can also solve the problem that the fixed ratio of traditional denitrification fillers is difficult to adapt to the dynamic fluctuations of water quality (DO, nitrogen form). It can also solve the problem that the direct addition of liquid carbon source to traditional denitrification fillers easily leads to COD exceeding the standard and lacks intelligent control capabilities based on water quality feedback.

[0085] Among them, the composite ecological filler for strengthening in-situ denitrification of river water bodies is composed of anoxic denitrification filler and transition control filler, or is composed of aerobic nitrification filler, anoxic denitrification filler and transition control filler; Aerobic nitrification fillers include inorganic mineral matrix denitrification fillers, biological ceramsite, mineral-based slow-release functional materials and microbial immobilization functional carriers; Anoxic denitrification fillers include sulfur-based composite electron donor materials, slow-release organic carbon source materials, zero-valent iron-based environmental remediation materials, and denitrifying bacteria embedding gels; The transition control filler includes multifunctional water treatment filter material, activated carbon and environmentally responsive functional microbial carrier.

[0086] In some embodiments, the inorganic mineral-based denitrification filler is selected from at least one of volcanic rock, zeolite, diatomaceous earth, and steel slag.

[0087] In some embodiments, the mineral-based sustained-release functional material is selected from at least one of magnesium ammonium phosphate sustained-release spheres, calcium carbonate-coated sustained-release particles, and hydroxyapatite.

[0088] Among them, magnesium ammonium phosphate slow-release pellets are a type of slow-release fertilizer with magnesium ammonium phosphate (NH₄MgPO₄·6H₂O) as its core ingredient. Typically formulated into spherical particles, they control the nutrient release rate, improving fertilizer utilization and reducing environmental pollution. In this application, magnesium ammonium phosphate slow-release pellets are cleverly used in composite ecological fillers for enhanced in-situ denitrification of river waters, buffering water alkalinity and promoting the conversion of NH₃-N to NO⁻-N under high DO conditions.

[0089] In some embodiments, the microorganism immobilization functional carrier is selected from at least one of a nitrifying bacteria immobilization carrier, polyurethane foam, and sodium alginate-montmorillonite composite gel.

[0090] In some embodiments, the sulfur-based composite electron donor material is selected from at least one of sulfur particles, pyrite, and sodium thiosulfate slow-release spheres.

[0091] In some embodiments, the slow-release organic carbon source material is selected from at least one of lignin carbon source balls, polycaprolactone (PCL), and starch-based gel.

[0092] In some embodiments, the zero-valent iron-based environmental remediation material is selected from at least one of sponge iron, zero-valent iron powder, and iron-carbon micro-electrolysis filler.

[0093] Sponge iron is a type of direct reduced iron (DRI). It is a porous iron product obtained by removing oxygen from iron ore (such as hematite or magnetite) using a reducing gas (such as hydrogen, carbon monoxide, or natural gas) or a solid reducing agent (such as coal) at high temperatures (usually below the melting point of iron). Its porous, sponge-like structure gives it the name "sponge iron."

[0094] In some embodiments, the zero-valent iron powder is selected from nano zero-valent iron.

[0095] In some embodiments, the multifunctional water treatment filter material is selected from at least one of manganese sand, titanium dioxide coated ceramsite and aluminum oxide.

[0096] In some embodiments, the environmentally responsive functional microbial carrier is selected from at least one of an oxidation-reduction potential (ORP)-sensitive bacterial agent carrier, a pH-responsive bacterial community carrier, and a DO gradient-sensing biofilm carrier.

[0097] In some embodiments, the aerobic nitrification filler comprises, by mass percentage, 50-70% volcanic rock, 20-30% biological ceramsite, 5-10% magnesium ammonium phosphate slow-release balls, and 5-10% nitrifying bacteria immobilization carriers.

[0098] By combining magnesium ammonium phosphate slow-release balls with nitrifying bacteria immobilization carriers, the challenge of insufficient alkalinity in the traditional nitrification process is solved. This improves the metabolic activity of nitrifying bacteria (such as Nitrosomonas and Nitrobacter), and NH4 + The oxidation rate is increased by more than 50%. It ensures that the effluent ammonia nitrogen (NH4 + -N) concentration meets the standard.

[0099] In some embodiments, the anoxic denitrification filler comprises, by mass percentage, 30-45% sulfur particles, 15-30% lignin carbon source balls, 35-45% sponge iron, and 5-15% denitrifying bacteria embedding gel.

[0100] The sulfur-lignin-sponge iron composite system realizes the synergy of electron donor (sulfur), carbon source (lignin) and DO regulation (oxygen consumption by iron corrosion) (Class B innovation). Through the synergy of multiple electron donors, dynamic regulation of DO / ORP and by-product inhibition, it achieves efficient and stable denitrification performance. At the same time, it breaks through the strict restrictions of traditional technologies on DO and carbon sources, providing a low-carbon and intelligent solution for in situ river restoration.

[0101] In some embodiments, the transition control filler comprises, by mass percentage, 50% manganese sand, 30% coconut shell activated carbon, and 20% oxidation-reduction potential (ORP)-sensitive bacterial agent carrier.

[0102] In some embodiments, when DO ≥ 4 mg / L and NH3-N / NO3 - When -N>1, the composite ecological filler consists of 70~80% aerobic nitrification filler, 10~15% anoxic denitrification filler and 5~10% transition control filler.

[0103] In some embodiments, when DO≤2 mg / L and NO3 - When -N≥5 mg / L, the composite ecological filler consists of 10~20% aerobic nitrification filler, 60~70% anoxic denitrification filler and 15~20% transition control filler.

[0104] In some embodiments, when the DO change is greater than 2 mg / L per hour, the composite ecological filler is composed of 25% aerobic nitrification filler, 25% anoxic denitrification filler, and 50% transition control filler.

[0105] When the composite ecological filler is composed of aerobic nitrification filler, anoxic denitrification filler and transition control filler, it is suitable for river water bodies with a temperature greater than or equal to 10°C.

[0106] In some embodiments, when the water temperature of the river is less than 10°C, and NO3 - When -N≥5 mg / L, the composite ecological filler consists of anoxic denitrification filler and transition control filler, and the mass percentage of anoxic denitrification filler in the composite ecological filler is 10~15%.

[0107] In some embodiments, when the COD / N ratio of the river water body is less than 4, the mass percentage of the slow-release organic carbon source material in the anoxic denitrification filler is 30-40%.

[0108] In some embodiments, the bioceramic pellets are selected from at least one of clay ceramic pellets, fly ash ceramic pellets, shale ceramic pellets, coal gangue ceramic pellets and bio-sludge ceramic pellets.

[0109] In some embodiments, the nitrifying bacteria immobilization carrier is selected from at least one of clay ceramsite, shale ceramsite, natural zeolite, activated zeolite, pyrolysis biochar, polyvinyl alcohol immobilization beads, modified polyvinyl alcohol, open-cell PU foam and bacterial cellulose membrane.

[0110] Nitrifying bacteria immobilization carriers are functional materials specifically designed to immobilize and enrich nitrifying bacteria (such as Nitrosomonas and Nitrobacter). Their core function is to provide a stable attachment environment for nitrifying bacteria and optimize their growth and metabolic conditions. Experimental studies have shown that immobilization technology significantly improves the denitrification efficiency of nitrifying bacteria in A / O processes, significantly reducing ammonia nitrogen and total nitrogen concentrations, thereby improving biological denitrification efficiency.

[0111] The preparation method of modified polyvinyl alcohol (PVA) comprises the following steps: ① Prepare a PVA / SA mixed aqueous solution with a mass ratio of 7:3. The total concentration of PVA and SA in the mixed aqueous solution is 8%. Then, stir the mixed aqueous solution at a constant temperature of 60°C for 10 minutes. ② The mixed aqueous solution was dripped into a CaCl2 solution with a step-by-step concentration through a microfluidic device. The step-by-step concentration of the CaCl2 solution included 0.5 mol / L, 1.0 mol / L, and 2.0 mol / L, respectively. Each step was cured for 15 minutes to form a heterogeneous structure with a dense shell and a loose core, thereby obtaining modified polyvinyl alcohol.

[0112] In some embodiments, the lignin carbon source balls are selected from at least one of enzymatically hydrolyzed lignin carbon balls, lignin sulfonate carbon balls, and industrial lignin carbon balls.

[0113] Lignin carbon source spheres are porous carbon spheres made from lignin (a natural polymer found in plant cell walls) through a specialized process. These materials possess a high surface area, a controllable pore structure, and a rich array of surface functional groups, making them suitable for a wide range of applications in energy storage, environmental remediation, and catalytic conversion.

[0114] In some embodiments, the denitrifying bacteria embedding gel is selected from at least one of sodium alginate (SA)-calcium chloride gel, chitosan-based gel, starch-PVA composite gel, polyvinyl alcohol (PVA)-boric acid gel and polyurethane (PU) hydrogel.

[0115] Denitrifying bacteria embedded gel is a functional material that fixes denitrifying bacteria (such as Pseudomonas, Paracoccus, etc.) in a polymer gel network through microencapsulation technology. It aims to improve denitrification efficiency and solve problems such as carbon source utilization and bacterial loss in traditional biological denitrification.

[0116] In some embodiments, the ORP-sensitive bacterial agent carrier is selected from at least one of Fe3O4 / Fe2O3 gel, magnetic biochar, and iron-sulfur minerals (such as pyrite).

[0117] Oxidation-reduction potential (ORP)-sensitive bacterial agent carriers are intelligent biomaterial carriers that can respond to changes in the environmental ORP and dynamically regulate the activity of functional microorganisms. Through material design, these carriers sense and respond to the redox potential in water or soil, thereby optimizing the metabolic environment of microorganisms (such as denitrifiers and anaerobic ammonium oxidizers) and improving pollutant removal efficiency.

[0118] In some embodiments, the sulfur particles have a particle size of 0.5-1 mm.

[0119] In some embodiments, the particle size of the sponge iron is 2-3 mm.

[0120] In some embodiments, a composite ecological filler for enhancing in-situ denitrification of river water is provided for use in in-situ denitrification of river water.

[0121] In some embodiments, a river water infiltration system is further provided, comprising the composite ecological filler and filler device for enhancing in-situ denitrification of river water according to any of the above embodiments; The packing device includes a first packing unit, a second packing unit and a third packing unit which are independent of each other; The first filler unit is filled with aerobic nitrification filler, the second filler unit is filled with anoxic denitrification filler, and the third filler unit is filled with transition control filler.

[0122] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the composite ecological filler, infiltration system and application for enhancing in-situ denitrification of river water bodies of the present invention will be further described in detail below with reference to specific embodiments and drawings. Obviously, the specific embodiments described are only part of the embodiments of the present application, not all of them. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation to the present application and its applications. Based on the specific embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0123] If no specific techniques or conditions are specified in the specific examples, the techniques or conditions described in the literature in this field or the product instructions were used. If no manufacturer is specified for the reagents or instruments used, they are all commercially available conventional products.

[0124] Example 1 A method for enhancing in-situ denitrification of river water bodies using a percolation system for denitrification of high-ammonia nitrogen river water bodies comprises the following steps: S1. Preparation of composite ecological filler for strengthening in-situ denitrification of river water: The composite ecological filler for strengthening in-situ denitrification of river water consists of 75% aerobic nitrification filler, 15% anoxic denitrification filler and 10% transition control filler; The aerobic nitrification filler (Type A filler) includes, by mass percentage, 60% porous basalt, 25% shale ceramsite, 7.5% magnesium ammonium phosphate slow-release balls, and 7.5% modified polyvinyl alcohol as a nitrifying bacteria immobilization carrier; The anoxic denitrification filler (type B filler) includes, by mass percentage, 50% sulfur particles, 25% lignin carbon source balls, 20% sponge iron, and 5% sodium alginate (SA)-calcium chloride gel as the denitrifying bacteria embedding gel; The transition control filler (Type C filler) includes, by mass percentage, 50% manganese sand, 30% coconut shell activated carbon, and 20% redox potential (ORP) sensitive bacterial agent carrier; The method for preparing modified polyvinyl alcohol comprises the following steps: ① Prepare a PVA / SA mixed aqueous solution with a mass ratio of 7:3. The total concentration of PVA and SA in the mixed aqueous solution is 8%. Then, stir the mixed aqueous solution at a constant temperature of 60°C for 10 minutes. ② The mixed aqueous solution was dripped into a CaCl2 solution with a stepwise concentration of 0.5 mol / L, 1.0 mol / L, and 2.0 mol / L using a microfluidic device. Each step was cured for 15 minutes to form a heterogeneous structure with a dense shell and a loose core, thereby obtaining modified polyvinyl alcohol. S2, filling filler: such as Figure 1 As shown, the packing device is a honeycomb detachable unit, and 75% of the aerobic nitrification filler (type A filler) prepared in S1 is independently filled into the first packing unit 1 of the packing device, with a filling thickness of 90 cm, 15% of the anoxic denitrification filler (type B filler) is filled into the second packing unit 2 of the packing device, with a filling thickness of 135 cm, and 10% of the transition control filler (type C filler) is filled into the third packing unit 3 of the packing device, with a filling thickness of 72 cm. S3, strengthen the in-situ denitrification of river water: place the packing device filled with packing in S2 into the high ammonia nitrogen river water, and add nitrifying bacteria, denitrifying bacteria and redox potential (ORP) sensitive bacteria into the river water, with a hydraulic load of 1m 2 / (m 2 ·d) In high ammonia nitrogen rivers, DO is 5~8 mg / L, NH3-N is 8 mg / L, and NO3 - -N is 2 mg / L, and the water temperature in the high ammonia nitrogen river is 25℃.

[0125] S4. After 7 days of stabilization, water samples were collected 3 meters downstream of the packing device for measurement. The NH3-N content was reduced to 0.5 mg / L, and NO3 - -N rises to 6 mg / L, and then switches to composite ecological fillers and devices; The composite ecological filler composition is as follows: 65% anoxic denitrification filler (Type B filler), which is loaded into the first filler unit 1 of the filler assembly to a depth of 90 cm. The anoxic denitrification filler, by mass, consists of 55% sulfur granules; 25% lignin carbon source pellets; 15% sponge iron; and 5% sodium alginate (SA)-calcium chloride gel. Aerobic nitrification filler (Class A filler) accounts for 15% and is loaded into the second packing unit 2 of the packing device with a packing thickness of 135 cm. The aerobic nitrification filler consists of the following by mass percentage: 70% porous basalt and 30% shale ceramsite; The transition control filler (Class C filler) accounts for 20%. The Class C filler is filled into the third filler unit 3 of the filler device with a filling thickness of 72 cm. The Class C filler includes, by mass percentage: 60% manganese sand and 40% Fe3O4 / biochar.

[0126] S5. Monitor the water quality after 7 days and determine that the TN content in the river water is less than 1 mg / L.

[0127] Example 2 A method for enhancing in-situ denitrification of river water bodies using a percolation system for denitrification of low-temperature, high-nitrate nitrogen water bodies, comprising the following steps: S1. Preparation of composite ecological filler for strengthening in-situ denitrification of river water: The composite ecological filler for strengthening in-situ denitrification of river water consists of 85% anoxic denitrification filler and 15% transition control filler; The anoxic denitrification filler includes 45% sulfur particles, 20% lignin carbon source balls, 10% sponge iron, 20% nano zero-valent iron and 5% denitrifying bacteria embedding gel by mass percentage; The transition control filler includes 50% manganese sand, 30% coconut shell activated carbon and 20% oxidation-reduction potential (ORP) sensitive bacterial agent carrier in terms of mass percentage; S2, filling filler: such as Figure 1 As shown, the packing device is a honeycomb detachable unit, and 85% of the anoxic denitrification filler prepared in S1 is independently filled into the first packing unit 1 of the packing device, with a filling thickness of 90 cm, and 15% of the transition control filler is filled into the third packing unit 3 of the packing device, with a filling thickness of 90 cm; S3, strengthen the in-situ denitrification of river water: place the packing device filled with packing in S2 in low temperature and high nitrate nitrogen water, and add denitrifying bacteria and redox potential (ORP) sensitive bacteria to the river water, with a hydraulic load of 1m 2 / (m 2 ·d) The DO of low-temperature and high-nitrate nitrogen water is 1.5 mg / L, NO3 - -N is 15 mg / L and the water temperature is 6°C.

[0128] During the operation, a sudden rainstorm caused reoxygenation, and DO increased sharply from 1.5 mg / L to 4 mg / L. This process was a DO mutation period.

[0129] At the same time, a control test was conducted by placing the packing device filled entirely with sulfur particles in the same low-temperature, high-nitrate nitrogen water body as in Example 2. The results of the changes in TN removal rate and denitrification rate during different DO periods are shown in Tables 1 and 2.

[0130] Table 1 Changes in TN removal rate and denitrification rate of low-temperature and high-nitrate nitrogen water treated with composite ecological fillers during different DO periods Table 2 Changes in TN removal rate and denitrification rate of low-temperature and high-nitrate nitrogen water treated with sulfur particles during different DO periods The recovery period is defined as the period within 30 minutes of a DO mutation. A comparative analysis of Tables 1 and 2 shows that during the DO mutation period, the TN removal rate of the composite ecological filler in low-temperature, high-nitrate nitrogen water decreased by only 12% (from 92% to 73%), recovering to 85% after 30 minutes. During the DO stability period, the denitrification rate reached 1.1 g N / (m³·h), an 80% increase compared to traditional sulfur fillers (i.e., fillers filled entirely with sulfur granules). This demonstrates that the "ORP-sensitive dynamic balance" technology proposed in this invention can effectively address DO mutations, achieving an innovative low-temperature enhancement strategy for DO mutation buffering through the redox potential response of the C-type filler (i.e., the low-temperature synergistic effect of nano-zero-valent iron and sulfur in Example 2).

[0131] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A composite ecological filler for enhancing in-situ denitrification of river water, characterized in that: It is composed of anoxic denitrification filler and transition control filler, or it is composed of aerobic nitrification filler, anoxic denitrification filler and transition control filler; The aerobic nitrification filler includes an inorganic mineral matrix denitrification filler, biological ceramsite, a mineral-based slow-release functional material and a microbial immobilization functional carrier; The anoxic denitrification filler comprises a sulfur-based composite electron donor material, a slow-release organic carbon source material, a zero-valent iron-based environmental remediation material, and a denitrifying bacteria embedding gel; The transition control filler includes multifunctional water treatment filter material, activated carbon and environmentally responsive functional microbial carrier.

2. The composite ecological filler for enhancing in-situ denitrification of river water according to claim 1, characterized in that: The inorganic mineral matrix denitrification filler is selected from at least one of volcanic rock, zeolite, diatomaceous earth and steel slag; And / or, the mineral-based sustained-release functional material is selected from at least one of magnesium ammonium phosphate sustained-release spheres, calcium carbonate-coated sustained-release particles and hydroxyapatite; And / or, the microorganism immobilization functional carrier is selected from at least one of a nitrifying bacteria immobilization carrier, polyurethane foam and sodium alginate-montmorillonite composite gel; And / or, the sulfur-based composite electron donor material is selected from at least one of sulfur particles, pyrite and sodium thiosulfate slow-release balls; And / or, the slow-release organic carbon source material is selected from at least one of lignin carbon source balls, polycaprolactone (PCL) and starch-based gel; And / or, the zero-valent iron-based environmental remediation material is selected from at least one of sponge iron, zero-valent iron powder and iron-carbon micro-electrolysis filler; And / or, the multifunctional water treatment filter material is selected from at least one of manganese sand, titanium dioxide coated ceramsite and aluminum oxide; And / or, the environmentally responsive functional microbial carrier is selected from at least one of an oxidation-reduction potential (ORP)-sensitive bacterial agent carrier, a pH-responsive bacterial community carrier, and a DO gradient-sensing biofilm carrier.

3. The composite ecological filler for enhancing in-situ denitrification of river water according to claim 2, characterized in that: The aerobic nitrification filler comprises, by mass percentage, 50-70% of volcanic rock, 20-30% of biological ceramsite, 5-10% of magnesium ammonium phosphate slow-release balls, and 5-10% of nitrifying bacteria immobilization carriers; And / or, the anoxic denitrification filler comprises, by mass percentage, 30-45% sulfur particles, 15-30% lignin carbon source balls, 35-45% sponge iron and 5-15% denitrifying bacteria embedding gel; And / or, the transition control filler comprises, by mass percentage, 50% manganese sand, 30% coconut shell activated carbon, and 20% oxidation-reduction potential (ORP) sensitive bacterial agent carrier.

4. The composite ecological filler for enhancing in-situ denitrification of river water according to claim 1, characterized in that: When DO≥4 mg / L and NH3-N / NO3 - - When N>1, the composite ecological filler is composed of 70-80% aerobic nitrification filler, 10-15% anoxic denitrification filler and 5-10% transition control filler; And / or, when DO≤2 mg / L and NO3 - -N≥5 mg / L, the composite ecological filler consists of 10-20% aerobic nitrification filler, 60-70% anoxic denitrification filler and 15-20% transition control filler; And / or, when the DO changes by more than 2 mg / L per hour, the composite ecological filler is composed of 25% aerobic nitrification filler, 25% anoxic denitrification filler and 50% transition control filler.

5. The composite ecological filler for enhancing in-situ denitrification of river water according to claim 1, characterized in that: When the water temperature of the river is less than 10℃ and NO3 - When -N≥5 mg / L, the composite ecological filler consists of anoxic denitrification filler and transition control filler, and the mass percentage of the anoxic denitrification filler in the composite ecological filler is 10-15%.

6. The composite ecological filler for enhancing in-situ denitrification of river water according to claim 1, characterized in that: When the COD / N ratio of the river water is less than 4, the mass percentage of the slow-release organic carbon source material in the anoxic denitrification filler is 30-40%, and the slow-release organic carbon source material is selected from starch-based gel, wherein the C / N ratio in the starch-based gel is 5-8.

7. The composite ecological filler for enhancing in-situ denitrification of river water according to claim 3, characterized in that: The bioceramic aggregate is selected from at least one of clay ceramic aggregate, fly ash ceramic aggregate, shale ceramic aggregate, coal gangue ceramic aggregate and bio-sludge ceramic aggregate; And / or, the nitrifying bacteria immobilization carrier is selected from at least one of clay ceramsite, shale ceramsite, natural zeolite, activated zeolite, pyrolysis biochar, polyvinyl alcohol immobilization beads, modified polyvinyl alcohol, open-cell PU foam and bacterial cellulose membrane; And / or, the lignin carbon source balls are selected from at least one of enzymatically hydrolyzed lignin carbon balls, lignin sulfonate carbon balls and industrial lignin carbon balls; and / or, the denitrifying bacteria embedding gel is selected from at least one of sodium alginate (SA)-calcium chloride gel, chitosan-based gel, starch-PVA composite gel, polyvinyl alcohol (PVA)-boric acid gel and polyurethane (PU) hydrogel; And / or, the oxidation-reduction potential (ORP) sensitive bacterial agent carrier is selected from at least one of Fe3O4 / Fe2O3 gel, magnetic biochar and iron-sulfur minerals.

8. The composite ecological filler for enhancing in-situ denitrification of river water according to claim 3, characterized in that: The particle size of the sulfur particles is 0.5-1 mm; And / or, the particle size of the sponge iron is 2-3 mm.

9. Use of the composite ecological filler for enhancing in-situ denitrification of river water as claimed in any one of claims 1 to 8 for in-situ denitrification of river water.

10. A river water infiltration system, characterized in that: The composite ecological filler and filler device for enhancing in-situ denitrification of river water bodies according to any one of claims 1 to 8 are included; The packing device comprises a first packing unit, a second packing unit and a third packing unit which are independent of each other; The first filler unit is filled with aerobic nitrification filler, the second filler unit is filled with anoxic denitrification filler, and the third filler unit is filled with transition control filler.

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