Composite ecological filler for strengthening in-situ denitrification of river water body, infiltration system and application thereof

Abstract

The present application relates to a kind of composite ecological filler of river water body in situ denitrification strengthening, percolation system and application.The composite ecological filler is composed of anoxic denitrification filler and transition control filler or composed of aerobic nitrification filler, anoxic denitrification filler and transition control filler;Aerobic nitrification filler includes inorganic mineral substrate denitrification filler, biological ceramsite, mineral base slow-release functional material and microbial immobilized functional carrier;Anoxic denitrification filler includes sulfur-based composite electron donor material, slow-release organic carbon source material, zero-valent iron-based environmental remediation material and denitrifying bacteria embedding gel;Transition control filler includes multifunctional water treatment filter material, activated carbon and environmental response type functional microbial carrier.The present application also provides the application of composite ecological filler and percolation system, the present application solves the problem that traditional denitrification filler is single in function, which leads to the inability to support nitrification / denitrification in coordination, also solves the problem that fixed ratio of traditional denitrification filler is difficult to adapt to dynamic fluctuation of water quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a composite ecological filler for enhancing in-situ denitrification of river water, a filtration system and application. BACKGROUND

[0002] In the field of water body nitrogen pollution control, especially in the application scenarios of sewage treatment and constructed wetlands, biological denitrification technology is widely used due to its economic efficiency. The essence of this technology lies in the precise execution of nitrification and denitrification by microorganisms under specific conditions, thereby efficiently converting nitrogen-containing pollutants into harmless nitrogen gas. As the carrier for microbial attachment and the site for reaction, the performance of the filler directly affects the denitrification efficiency and operational stability of the system.

[0003] Currently, traditional denitrification fillers, such as volcanic rock and zeolite, have obvious limitations in application: relatively single function, often limited to excellent physical adsorption capacity or specific chemical properties (e.g. ion exchange of zeolite), making it difficult to meet the dynamic changes in microenvironmental requirements during aerobic nitrification and anoxic denitrification. The nitrification process requires sufficient dissolved oxygen (DO) environment, while the denitrification process needs to be carried out under anoxic or even anaerobic conditions. Traditional fillers cannot effectively regulate or adapt to this dynamic change in dissolved oxygen environment, limiting their overall denitrification efficiency. The fixed ratio of adaptability defects often uses a fixed volume or mass ratio combination of multiple fillers in practice to try to take into account different processes. However, in actual water bodies, the DO level often fluctuates significantly (e.g. from a low oxygen state of 0.5 mg / L to a high oxygen state of 8 mg / L), and the form of incoming nitrogen pollutants (such as the relative proportion of NH3-N and NO3-N) also changes frequently. In the face of such dynamic changes in water quality conditions (DO fluctuation, nitrogen form ratio difference), the fixed ratio of filler system shows obvious lack of adaptability, and its denitrification efficiency is usually significantly reduced by 30%~50% compared to the ideal state or stable conditions, resulting in unstable effluent water quality and difficult to guarantee the running effect. The experience dependence and lack of regulation of constructed wetland fillers, in the constructed wetland system, the selection and ratio of fillers largely depend on engineering experience and limited experimental data, lacking scientific and precise dynamic regulation mechanism based on real-time or periodic monitoring of water quality parameters (such as DO, NH3-N, NO3-N, pH, temperature, etc.). This "static" filler configuration mode cannot respond to the complex and variable hydraulic conditions inside the wetland, the fluctuation of pollutant load and the changes in environmental parameters brought by seasonal changes, resulting in large fluctuations in treatment efficiency and difficulty in achieving stable and efficient denitrification.

[0004] In summary, the existing denitrification filler technology, especially when applied to dynamic water environment, faces the main problems that single function leads to the inability to support nitrification / denitrification, fixed ratio is difficult to adapt to dynamic fluctuations of water quality (DO, nitrogen form), direct addition of liquid carbon source is easy to lead to COD exceeding the standard, and lack of intelligent control ability based on water quality feedback. These defects significantly hinder the efficient operation, stable performance and adaptability of the denitrification system. Therefore, it is urgent to develop a new type of composite filler with multifunctional synergistic effect, which can adapt to environmental changes or can be intelligently dynamically regulated according to water quality parameters, and its application method, to significantly improve the denitrification performance and operation stability under complex dynamic water conditions, and meet the increasingly stringent ecological restoration requirements. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a composite ecological filler for enhancing in-situ denitrification of river water, a filtration system and an application, so as to solve the problem of single function of traditional denitrification filler leading to the inability to support nitrification / denitrification, and also solve the problem of fixed ratio of traditional denitrification filler being difficult to adapt to dynamic fluctuations of water quality (DO, nitrogen form), and also solve the problem of direct addition of liquid carbon source of traditional denitrification filler being easy to lead to COD exceeding the standard and lack of intelligent control ability based on water quality feedback.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A composite ecological filler for enhancing in-situ denitrification of river water is composed of anoxic denitrification filler (B type filler) and transition regulation filler (C type filler), or composed of aerobic nitrification filler (A type filler), anoxic denitrification filler (B type filler) and transition regulation filler (C type filler);

[0008] The aerobic nitrification filler includes inorganic mineral substrate denitrification filler, biological ceramic, mineral-based slow-release functional material and microbial immobilized functional carrier;

[0009] The anoxic denitrification filler includes sulfur-based composite electron donor material, slow-release organic carbon source material, zero-valent iron-based environmental remediation material and denitrifying bacteria embedded gel;

[0010] The transition regulation filler includes multifunctional water treatment filler, activated carbon and environment-responsive functional microbial carrier.

[0011] According to the above technical means, by skillfully selecting inorganic mineral matrix denitrification filler, biological ceramic, mineral matrix slow-release functional material and microbial immobilized functional carrier as aerobic nitrification filler, selecting sulfur-based composite electron donor material, slow-release organic carbon source material, zero-valent iron-based environmental remediation material and denitrifying bacteria embedded gel as anoxic denitrification filler, and selecting sulfur-based composite electron donor material, slow-release organic carbon source material, zero-valent iron-based environmental remediation material and denitrifying bacteria embedded gel as transition control filler, thereby mixed to form a composite ecological filler, which is used for in-situ denitrification of river water, and through the synergistic effect of aerobic nitrification filler, anoxic denitrification filler and transition control filler or anoxic denitrification filler and transition control filler, an anoxic zone is formed under high DO, efficient connection of nitrification and denitrification process is realized, and the problem of single function of traditional filler is solved. And through the cooperation of transition control filler and anoxic denitrification filler, the microbial community and organic carbon source supply can be automatically adjusted according to the dynamic change of water quality (such as dissolved oxygen, nitrogen form, etc.), adapt to water quality fluctuation, and have intelligent control ability based on water quality feedback, thereby avoiding the problem of COD exceeding standard caused by fixed proportion and direct addition of liquid carbon source of traditional filler, thereby significantly improving the denitrification efficiency and stability and adaptability of the system.

[0012] Among them, the traditional denitrification material cannot meet the following requirements at the same time: 1) anoxic microenvironment construction: it is difficult to form an anoxic zone required for denitrification under high dissolved oxygen conditions; 2) slow-release carbon source supply: direct addition of liquid carbon source is easy to cause COD exceeding standard; 3) directional enrichment of functional bacteria: the synergistic effect of nitrifying bacteria / denitrifying bacteria needs differential carrier support.

[0013] And the present application solves the above three technical problems systematically through the following innovative design, specifically as follows:

[0014] 1. Anoxic microenvironment construction strategy (formation of anoxic zone under high DO)

[0015] Oxidation oxygen consumption mechanism of zero-valent iron-based environmental remediation material: adding zero-valent iron-based environmental remediation material [such as sponge iron (FeO)] in the anoxic denitrification filler, which has an oxidation reaction with dissolved oxygen in water (4FeO + 3O2+ 6H2O → 4Fe(OH)3), which quickly consumes local DO (0.43 mg DO per gram of FeO), and forms an anoxic microzone with DO≤0.5 mg / L between filler particles.

[0016] Synergistic effect of sulfur autotrophic denitrification: sulfur-based composite electron donor material [such as sulfur granules (S)] and denitrifying bacteria form a sulfur autotrophic denitrification system (55S + 20NO3⁻ + 38H2O → 5S2O3²⁻ + 4N2 + 76H +), which can be achieved by micro-zone isolation in high-DO mainstream water bodies without organic carbon source.

[0017] Particle size gradient design: Sulfur-based composite electron donor material [sulfur particles (0.5-1mm)] and zero-valent iron-based environmental remediation material [sponge iron (2-3mm)] form a layered accumulation structure. The internal pores of large particles form a diffusion-limited anoxic zone. Actual measurements show that this structure can reduce the DO concentration in the micro-zone by 80% compared to the main water body.

[0018] 2. Precise supply of slow-release carbon source (avoiding COD over-standard)

[0019] Multi-stage slow-release technology:

[0020] Physical slow-release: Slow-release organic carbon source material [such as lignin carbon source ball] controls the release rate (release half-life of 15-20 days) through pore diffusion. Its surface hydroxyl and carboxyl functional groups can adsorb excess carbon source.

[0021] Chemical slow-release: Slow-release organic carbon source material [such as polycaprolactone (PCL)] gradually releases small molecule organic matter through ester bond hydrolysis. The release rate is ≤0.2mg C / (g·h) at a water temperature of 10℃.

[0022] Biological response type release: Slow-release organic carbon source material [such as starch-based gel] has α-1,4 glycosidic bonds that are specifically broken by starch amylase secreted by denitrifying bacteria, achieving on-demand release of carbon source.

[0023] Dynamic C / N control: For example, when COD / N <4, by increasing the proportion of slow-release carbon source (30-40%) and selecting C / N adjustable starch-based gel (C / N=5-8), the required carbon source for denitrification is ensured while the COD increase is controlled to ≤15%.

[0024] 3. Functional bacterial community directional enrichment technology

[0025] Differential carrier design:

[0026] Oxygen zone filled with aerobic nitrification filler: Microbial immobilized functional carrier, such as polyurethane foam (porosity >90%) loaded with nitrifying bacteria immobilized carrier, its surface amino modification can specifically adsorb Nitrosomonas (adsorption capacity up to 10^8 CFU / g).

[0027] Anoxic zone filled with anoxic denitrification filler: Denitrifying bacteria embedded gel uses sodium alginate-Ca 2+ Crosslinked network, the reducing environment (ORP <-100mV) in the gel promotes the enrichment of Pseudomonas denitrificans (abundance increases by 3 times).

[0028] Transition zone filled with transition-regulated fillers: ORP-sensitive bacteria carrier, such as Fe3O4 / magnetic biochar carrier, realizes directional fixation of ORP-sensitive bacteria by magnetic response, and activates sulfur autotrophic denitrification function when ORP>200mV.

[0029] Cross-module coordination mechanism:

[0030] ORP signal transmission: Fe3O4 in transition-regulated fillers can sense ORP changes in real time (sensitivity ±10mV), and trigger the conversion of Fe 2+ / Fe 3+ Valence state to activate the function of adjacent modules.

[0031] Quorum sensing regulation: C6-HSL signal molecules released by nitrifying bacteria (threshold concentration 10nM) can induce the quorum sensing system of denitrifying bacteria to start, realizing metabolic synchronization of bacterial flora.

[0032] A / B / C type fillers realize cross-module coordination through ORP and microbial signal molecules

[0033] Cross-module transmission and response of ORP signal

[0034] (1) ORP sensing and regulation of C type fillers

[0035] The ORP-sensitive carrier (such as Fe3O4 / magnetic biochar, pyrite) in C type fillers can sense the ORP value of the water body in real time. For example:

[0036] When ORP>200mV (aerobic conditions), the conversion of Fe 3+ / Fe²⁺ valence state will trigger the release of electron acceptors (such as Mn 4 ⁺) by C type fillers, activating short-range nitrifying bacteria (such as Nitrosomonas) in A type fillers, rapidly converting NH3-N into NO2⁻-N, rather than completely oxidizing it into NO3⁻-N (saving 60% oxygen consumption).

[0037] When ORP<0mV (anaerobic conditions), the oxidation reaction of pyrite (FeS2) (FeS2 + 7H2O → Fe²⁺ + 2SO4²⁻ + 14H⁺ + 14e⁻) releases electrons, driving sulfur autotrophic denitrification (Thiobacillus denitrificans) in B type fillers to directly reduce NO3⁻-N to N2, bypassing the traditional carbon source-dependent denitrification.

[0038] (2) ORP feedback regulation of A / B type fillers

[0039] Steel slag (releasing Fe 3+ ) in A type fillers and sponge iron (Fe0 A redox gradient is formed:

[0040] In region A, Fe³⁺ consumes local DO through the Fenton reaction (Fe²⁺ + H₂O₂ → Fe³⁺ + OH⁻ + ·OH), reducing ORP and creating a pre-hypoxic environment for the adjacent region B (DO decreases from 4 mg / L to 1.5 mg / L).

[0041] In region B, Fe 0 Fe produced by corrosion 2+ (Fe) 0 + 2H2O → Fe 2+ + H2↑ + 2OH - Further reducing the ORP to below -150mV activates the nitrate reductase activity of denitrifying bacteria.

[0042] 2. Quorum sensing and metabolic synergy of microbial signaling molecules

[0043] Class A packing material releases signal molecules.

[0044] Nitrifying bacteria (such as Nitrosomonas) in type A packing materials secrete acylhomoserine lactones (AHLs, such as C6-HSL) during metabolism. When the concentration reaches 10... -8 During phase M, the denitrifying bacteria (such as Pseudomonas) in type B packing material 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 type C packing material are induced to secrete extracellular polymers (EPS), enhancing the adhesion ability of the bacteria to the carrier surface.

[0045] Metabolic product feedback of B / C type packing materials

[0046] The N2O and CO2 produced during denitrification in type B packing material diffuse into type C packing material. N2O acts as a signaling molecule, activating the anaerobic ammonia-oxidizing bacteria (Anammox) in type C carriers, prompting them to utilize NH4⁺ and NO2. - Direct N2 generation (NH4⁺ + NO2⁻ → N2↑ + 2H2O) reduces the accumulation of intermediate products. CO2 stimulates the proton-coupled electron transfer reaction of C-type manganese sand (MnO2) (MnO2 + 4H⁺ + 2e⁻ → Mn) by lowering the local pH (from 7.5 to 6.8). 2 (⁺ + 2H2O), which accelerates the oxidative removal of NO2⁻-N.

[0047] The final result achieved is as follows:

[0048] Nitrogen removal efficiency: total nitrogen removal efficiency increased from 45% for traditional fillers to 92%, of which short-cut nitrification-anammox (PD / A) contributed 35%, and sulfur-iron autotrophic denitrification contributed 57%.

[0049] Dynamic adaptability enhancement: when DO mutates (e.g., 4→1 mg / L), the metabolic path switching from complete nitrification to short-cut denitrification is completed within 30 minutes through ORP signals; when COD / N fluctuates, the enzyme response release of starch-based gel improves the carbon source dosing accuracy to ±5%, and the risk of COD exceeding the standard is reduced by 90%.

[0050] Optimization of functional bacterial community stability: the nitrifying bacteria biofilm density reached 1.2×10 10 CFU / g (only 3×10 9 CFU / g for traditional carriers), and the resistance to hydraulic flushing was increased by 4 times; the interspecies electron transfer efficiency of denitrifying bacteria was increased by 60%, avoiding the accumulation of intermediate products (NO2⁻, N2O), and the selectivity of N2 reached 98%.

[0051] Preferably, the inorganic mineral substrate denitrification filler is selected from at least one of volcanic rock, zeolite, diatomite, and steel slag.

[0052] Among them, zeolite also has the advantage of adsorbing NH3-N compared to volcanic rock; diatomite also has the advantage of high specific surface area compared to volcanic rock; steel slag also has the advantage of releasing Fe 3+ to promote nitrification.

[0053] Preferably, the volcanic rock is selected from porous basalt.

[0054] Preferably, the mineral-based slow-release functional material is selected from at least one of magnesium ammonium phosphate slow-release balls, calcium carbonate-coated slow-release particles (pH buffer), and hydroxyapatite (phosphorus control).

[0055] Among them, magnesium ammonium phosphate slow-release balls are a slow-release fertilizer with magnesium ammonium phosphate (NH4MgPO4·6H2O) as the core component, usually in the form of spherical particles, which can control the release rate of nutrients, improve fertilizer utilization, and reduce environmental pollution.

[0056] Preferably, the microbial immobilization functional carrier is selected from at least one of nitrifying bacteria immobilization carriers, polyurethane foam (porosity > 90%), and sodium alginate-montmorillonite composite gel (low temperature resistance).

[0057] Preferably, the sulfur-based composite electron donor material is selected from at least one of sulfur particles, pyrite (FeS2, providing Fe 2+ ) and sodium thiosulfate slow-release balls (low temperature suitable).

[0058] Preferably, the slow-release organic carbon source material is selected from at least one of lignin carbon source spheres, polycaprolactone (PCL, a biodegradable polymer carbon source), and starch-based gel (C / N adjustable).

[0059] 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 1:2).

[0060] Among them, sponge iron (Sponge Iron) is a direct reduced iron (DRI, Direct Reduced Iron), which is a porous iron product obtained by removing oxygen in iron ore (such as hematite, magnetite) with a reducing gas (such as hydrogen, carbon monoxide or natural gas) or a solid reducing agent (such as coal) at high temperature (usually below the melting point of iron). Due to its loose and porous internal structure, it is named "sponge iron".

[0061] Preferably, the zero-valent iron powder is selected from nano zero-valent iron.

[0062] Preferably, the multifunctional water treatment filter material is selected from at least one of manganese sand, titanium dioxide coated ceramsite (photocatalytic auxiliary denitrification), and aluminum oxide (adsorption of NH3-N).

[0063] Among them, manganese sand is often represented as MnO2·xH2O (containing crystal water), and 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 removing iron and manganese ions. Iron oxide (Fe2O3): Natural accompanying component (5~15%), auxiliary catalytic effect. Silicate minerals: such as quartz (SiO2), feldspar, etc. (20~40%), providing structural support. Manganese sand is regenerated through periodic aeration treatment (Mn 2+ converted to Mn 4+ ), which extends its service life by more than 3 times.

[0064] Preferably, the environmental response type functional microorganism carrier is selected from at least one of oxidation-reduction potential (ORP) sensitive bacteria agent carrier, pH responsive bacterial population (such as nitrosomonas activated when pH>7) carrier, and DO gradient sensing bacteria membrane carrier.

[0065] Preferably, the aerobic nitrification filler includes 50~70% of volcanic rock, 20~30% of biological ceramsite, 5~10% of magnesium ammonium phosphate slow-release ball, and 5~10% of nitrifying bacteria immobilized carrier by mass percentage.

[0066] By setting the composition and ratio of aerobic nitrification filler skillfully, NH3-N→NO3⁻-N conversion can be effectively promoted under high DO conditions, and magnesium ammonium phosphate provides alkalinity buffer.

[0067] Preferably, the anoxic denitrification filler comprises 30-45% sulfur particles, 15-30% lignin carbon source balls, 35-45% sponge iron and 5-15% denitrifying bacteria embedding gel by mass percentage.

[0068] Among them, sponge iron creates a low DO environment, effectively driving NO3⁻-N→N2 conversion.

[0069] Preferably, the transition regulation filler comprises 50% manganese sand, 30% coconut shell activated carbon and 20% oxidation-reduction potential (ORP) sensitive bacteria agent carrier by mass percentage.

[0070] According to the ORP dynamic adjustment of NH3-N / NO3 - -N ratio, thereby effectively adapting to the DO mutation scene.

[0071] Preferably, when DO≥4 mg / L and NH3-N / NO3 - -N>1, the composite ecological filler is composed of 70-80% aerobic nitrification filler, 10-15% anoxic denitrification filler and 5-10% transition regulation filler.

[0072] Preferably, when DO≤2 mg / L and NO3 - -N≥5 mg / L, the composite ecological filler is composed of 10-20% aerobic nitrification filler, 60-70% anoxic denitrification filler and 15-20% transition regulation filler.

[0073] Preferably, when the DO changes 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 regulation filler.

[0074] Among them, when the composite ecological filler is composed of aerobic nitrification filler, anoxic denitrification filler and transition regulation filler, it is suitable for river water bodies with temperature greater than or equal to 10℃.

[0075] Preferably, when the water temperature of the river water body is less than 10℃, and NO3 - -N≥5 mg / L, the composite ecological filler is composed of anoxic denitrification filler and transition regulation filler, and the mass percentage of anoxic denitrification filler in the composite ecological filler is 10-15%.

[0076] Preferably, when the COD / N of the river water body is less than 4, the mass percentage of slow-release type organic carbon source material in the anoxic denitrification filler is 30-40%.

[0077] By comprehensively considering the concentrations of DO, NH3-N, NO3-N and temperature conditions, and carefully selecting the filler ratio, the denitrification efficiency is significantly improved.

[0078] Preferably, the biological ceramsite is selected from at least one of clay ceramsite, fly ash ceramsite, shale ceramsite, coal gangue ceramsite and biological sludge ceramsite.

[0079] Preferably, the nitrifying bacteria immobilized carrier is selected from at least one of clay ceramsite, shale ceramsite, natural zeolite, activated zeolite, pyrolysis biomass carbon, polyvinyl alcohol immobilized small ball, modified polyvinyl alcohol, open-cell PU foam and bacterial cellulose membrane.

[0080] The nitrifying bacteria immobilized carrier is a functional material specially used for fixing and enriching nitrifying bacteria (such as Nitrosomonas, Nitrobacter, etc.), and its core function is to provide a stable adhesion environment for nitrifying bacteria and optimize its growth and metabolism conditions, thereby improving the biological denitrification efficiency.

[0081] The modified polyvinyl alcohol (PVA) preparation method comprises the following steps:

[0082] ① A PVA / SA mixed aqueous solution with a mass ratio of 7:3 is prepared, the total concentration of PVA and SA in the mixed aqueous solution is 8%, and then the mixed aqueous solution is stirred at a constant temperature of 60℃ for 10min;

[0083] ② The mixed aqueous solution is sequentially dropped into CaCl2 solutions with gradient concentrations through a microfluidic device, wherein the gradient concentrations of the CaCl2 solutions include 0.5mol / L, 1.0mol / L and 2.0mol / L in sequence, and gradually increase; each level is solidified for 15min to form a heterogeneous structure with dense shell and loose core, and the modified polyvinyl alcohol is obtained.

[0084] By adopting the sodium alginate (SA) blending-calcium chloride gradient solidification method, i.e. gradient Ca²⁺ diffusion solidification technology, the bacterial load is effectively improved, and the experimental determination shows that the adsorption capacity of the modified polyvinyl alcohol for nitrifying bacteria (Nitrosomonas) reaches 4.8×10 8 CFU / g, which is 3 times higher than that of homogeneous carriers.

[0085] Preferably, the lignin carbon source ball is selected from at least one of enzymatic hydrolysis lignin carbon ball, lignin sulfonate carbon ball and industrial lignin carbon ball.

[0086] Lignin carbon source spheres are a kind of porous carbon sphere materials prepared by specific process with lignin (a natural high molecular polymer in plant cell walls) as raw material. This kind of material has high specific surface area, controllable pore structure and rich surface functional groups, and has wide application in energy storage, environmental remediation, catalytic conversion and other fields.

[0087] Preferably, the denitrifying bacteria-embedded 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.

[0088] The denitrifying bacteria-embedded gel is a functional material that fixes denitrifying bacteria (such as Pseudomonas, Paracoccus, etc.) in a high molecular gel network through microencapsulation technology, aiming to improve denitrification efficiency and solve problems such as carbon source utilization and bacterial population loss in traditional biological denitrification.

[0089] Preferably, the oxidation-reduction potential (ORP) sensitive bacteria agent carrier is selected from at least one of Fe3O4 / Fe2O3 gel, magnetic biochar and iron-sulfur minerals (such as pyrite).

[0090] The oxidation-reduction potential (ORP) sensitive bacteria agent carrier is an intelligent biological material carrier that can respond to changes in environmental ORP and dynamically regulate the activity of functional microorganisms. This kind of carrier realizes the perception and response to the oxidation-reduction potential in water or soil through material design, thereby optimizing the metabolic environment of microorganisms (such as denitrifying bacteria, anaerobic ammonia oxidation bacteria, etc.) and improving the efficiency of pollutant removal.

[0091] Preferably, the particle size of the sulfur particles is 0.5-1mm.

[0092] Preferably, the particle size of the sponge iron is 2-3mm.

[0093] Through the particle size gradient design of sulfur particles and sponge iron, that is, the particle size difference between sulfur particles (0.5-1mm) and sponge iron (2-3mm), a pore gradient structure and layered reaction zone are formed. Small particle size sulfur provides high specific surface area, accelerating the electron transfer of sulfur autotrophic denitrification; large particle size sponge iron forms a micro-electrolysis environment (Fe 0 →Fe 2+ ) through slow corrosion, while its loose accumulation reduces water flow short-circuiting and prolongs hydraulic retention time (HRT).

[0094] The particle size gradient design of sulfur particles and sponge iron has the following advantages:

[0095] Synergistic denitrification: sulfur (S 0 ) as an electron donor and sponge iron (Fe 0micro-electrolysis reaction (S / Fe molar ratio 1:2) coupling, can simultaneously drive chemical denitrification (S 0 →SO4 2- ) and biological denitrification (Fe 2+ →Fe 3+ ), total nitrogen removal rate increased by 30%-45%.

[0096] DO regulation: sponge iron corrosion consumes dissolved oxygen (DO), forming an ORP <-50 mV anoxic microzone on the surface of sulfur, overcoming the inhibition of high dissolved oxygen (>4 mg / L) on denitrification.

[0097] Anti-clogging: particle size gradient forms multi-stage pores (sulfur fills the gap between large particles), flux increases by 2.3 times.

[0098] A / B type filler combination replacement:

[0099] A type filler surface loaded with Fe 3+ (promote short-range nitrification), specifically: biological ceramic is immersed in a 0.1 mol / L FeCl3 solution, calcined at a temperature of 400°C for 2h, forming a Fe2O3 coating on the surface, with a loading capacity of 5%-8% (w / w), thereby directional adsorption of ammonia-oxidizing bacteria (AOB), shortening the nitrification start-up period by 40%.

[0100] B type filler added anaerobic ammonia oxidation bacteria (Anammox), can realize low-carbon denitrification: Anammox bacteria use NH4⁺ as electron donor and NO2⁻ as electron acceptor, directly generating N2 without additional carbon source, COD / N demand is reduced from 4-6 to 0.5.

[0101] Synergistic metabolism: coupled with sulfur autotrophic denitrification (S 0 →SO4 2- provides part of NO2⁻), total nitrogen removal load increases to 1 kg N / (m 3 ·d).

[0102] C type filler function extension:

[0103] Add molybdate (promote nitrate reductase activity), molybdate (such as Na2MoO4) is added in the preparation stage of the environmental response type functional microorganism carrier of the transition control filler. Specific method: blend molybdate (0.05%-0.1% w / w) with magnetic biochar (carrier), and form Mo-Fe oxide complex by high-temperature activation in N2 atmosphere at a temperature of 600°C. After the carrier is loaded with denitrifying bacteria (such as Pseudomonas), molybdenum acts as a cofactor for nitrate reductase (Nap / Nar), making enzyme activity increase by 2.5 times, and denitrification rate still reaches 0.8 mg N / (g·h) at low temperature (10°C).

[0104] The application also provides application of the composite ecological filler for in-situ denitrification of river water bodies to in-situ denitrification of river water bodies.

[0105] When the composite ecological filler is aerobic nitrification filler, anoxic denitrification filler and transition control filler, it is used for treating water bodies in rivers with high ammonia nitrogen and low nitrate nitrogen.

[0106] The application also provides a river water body infiltration system comprising the composite ecological filler for in-situ denitrification of river water bodies and a filler device.

[0107] The filler device comprises a first filler unit, a second filler unit and a third filler unit which are independent of each other.

[0108] 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.

[0109] The application has the following advantages:

[0110] The composite ecological filler for in-situ denitrification of river water bodies ingeniously combines aerobic nitrification filler, anoxic denitrification filler and transition control filler, and is suitable for efficient denitrification of surface water with high dissolved oxygen content, low organic pollutant content and nitrate nitrogen as the main pollution characteristic under normal temperature and low temperature conditions, and has promotional application value in the field of river water body restoration technology. BRIEF DESCRIPTION OF DRAWINGS

[0111] Figure 1 Figure 1 is a structural schematic diagram of the filler device.

[0112] 1- first filler unit; 2- second filler unit; 3- third filler unit. DETAILED DESCRIPTION

[0113] The application can also be implemented or applied in other different specific embodiments, and each detail in the specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the application. It should be understood that the preferred embodiments are only for illustrating the application, and are not intended to limit the protection scope of the application.

[0114] The application aims to provide a composite ecological filler for in-situ denitrification of river water bodies, a filtration system and an application, to solve the problem of single function of traditional denitrification fillers, which cannot support nitrification and denitrification simultaneously, and to solve the problem of fixed ratio of traditional denitrification fillers, which cannot adapt to dynamic fluctuations of water quality (DO, nitrogen form), and to solve the problem of direct addition of liquid carbon source to traditional denitrification fillers, which is easy to cause COD to exceed the standard, and to solve the problem of lack of intelligent control ability based on water quality feedback.

[0115] The composite ecological filler for in-situ denitrification of river water bodies is composed of anoxic denitrification filler and transition regulation filler, or composed of aerobic nitrification filler, anoxic denitrification filler and transition regulation filler.

[0116] The aerobic nitrification filler includes inorganic mineral substrate denitrification filler, biological ceramic, mineral-based slow-release functional material and microbial immobilized functional carrier.

[0117] The anoxic denitrification filler includes sulfur-based composite electron donor material, slow-release organic carbon source material, zero-valent iron-based environmental remediation material and denitrifying bacteria embedded gel.

[0118] The transition regulation filler includes multifunctional water treatment filler, activated carbon and environment-responsive functional microbial carrier.

[0119] In some embodiments, the inorganic mineral substrate denitrification filler is selected from at least one of volcanic rock, zeolite, diatomite and steel slag.

[0120] In some embodiments, the mineral-based slow-release functional material is selected from at least one of magnesium ammonium phosphate slow-release ball, calcium carbonate-coated slow-release particle and hydroxyapatite.

[0121] The magnesium ammonium phosphate slow-release ball is a slow-release fertilizer with magnesium ammonium phosphate (NH4MgPO4·6H2O) as the core component, which is usually made into spherical particles, and can control the release rate of nutrients, improve the utilization rate of fertilizer and reduce environmental pollution. In this application, the magnesium ammonium phosphate slow-release ball is ingeniously used in the composite ecological filler for in-situ denitrification of river water bodies, which is used to buffer the alkalinity of the water body, and promotes the conversion of NH3-N to NO3⁻-N under high DO.

[0122] In some embodiments, the microbial immobilized functional carrier is selected from at least one of nitrifying bacteria immobilized carrier, polyurethane foam and sodium alginate-montmorillonite composite gel.

[0123] In some embodiments, the sulfur-based composite electron donor material is selected from at least one of sulfur granules, pyrite and sodium thiosulfate slow-release ball.

[0124] In some embodiments, the slow-release organic carbon source material is selected from at least one of lignin carbon source ball, polycaprolactone (PCL) and starch-based gel.

[0125] 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.

[0126] Sponge iron is a kind of direct reduced iron (DRI), which is a porous iron product obtained by removing oxygen in iron ore (such as hematite, magnetite) at high temperature (usually below the melting point of iron) with a reducing gas (such as hydrogen, carbon monoxide or natural gas) or a solid reducing agent (such as coal). Due to its loose and porous internal structure, it is named "sponge iron".

[0127] In some embodiments, the zero-valent iron powder is selected from nano zero-valent iron.

[0128] 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.

[0129] In some embodiments, the environment-responsive functional microbial carrier is selected from at least one of an oxidation-reduction potential (ORP) sensitive bacterial agent carrier, a pH responsive bacterial population carrier, and a DO gradient sensing bacterial membrane carrier.

[0130] In some embodiments, the aerobic nitrification filler includes 50-70% of volcanic rock, 20-30% of biological ceramsite, 5-10% of magnesium ammonium phosphate slow-release ball, and 5-10% of nitrifying bacteria immobilization carrier by mass percentage.

[0131] By combining the magnesium ammonium phosphate slow-release ball with the nitrifying bacteria immobilization carrier, the challenge of insufficient alkalinity in the traditional nitrification process is solved. The metabolic activity of nitrifying bacteria (such as Nitrosomonas and Nitrobacter) is improved, and the NH4 + The oxidation rate is increased by more than 50%. The concentration of effluent ammonia nitrogen (NH4 + -N) meets the standard.

[0132] In some embodiments, the anoxic denitrification filler includes 30-45% of sulfur particles, 15-30% of lignin carbon source balls, 35-45% of sponge iron, and 5-15% of denitrifying bacteria embedding gel by mass percentage.

[0133] The sulfur-lignin-sponge iron composite system realizes the synergy of electron donor (sulfur), carbon source (lignin), and DO regulation (iron corrosion oxygen consumption) (Class B innovation). Through multi-electron donor synergy, DO / ORP dynamic regulation, and byproduct inhibition, high-efficiency and stable denitrification performance is achieved, and the strict limitations on DO and carbon source in traditional technology are broken. A low-carbon and intelligent solution is provided for in-situ remediation of rivers.

[0134] In some embodiments, the transition regulation filler comprises 50% manganese sand, 30% coconut shell activated carbon, and 20% oxidation-reduction potential (ORP) sensitive bacterial agent carrier by mass percentage.

[0135] In some embodiments, when DO≥4 mg / L and NH3-N / NO3 - -N>1, the composite ecological filler is composed of 70-80% aerobic nitrification filler, 10-15% anoxic denitrification filler, and 5-10% transition regulation filler.

[0136] In some embodiments, when DO≤2 mg / L and NO3 - -N≥5 mg / L, the composite ecological filler is composed of 10-20% aerobic nitrification filler, 60-70% anoxic denitrification filler, and 15-20% transition regulation filler.

[0137] In some embodiments, when 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 regulation filler.

[0138] When the composite ecological filler is composed of aerobic nitrification filler, anoxic denitrification filler, and transition regulation filler, the suitable temperature of the river water body is greater than or equal to 10℃.

[0139] In some embodiments, when the water temperature of the river water body is less than 10℃, and NO3 - -N≥5 mg / L, the composite ecological filler is composed of anoxic denitrification filler and transition regulation filler, and the mass percentage of the anoxic denitrification filler in the composite ecological filler is 10-15%.

[0140] In some embodiments, when the COD / N 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%.

[0141] In some embodiments, the biological ceramsite is selected from at least one of clay ceramsite, fly ash ceramsite, shale ceramsite, coal gangue ceramsite, and biological sludge ceramsite.

[0142] In some embodiments, the nitrifying bacteria immobilization carrier is selected from at least one of clay ceramsite, shale ceramsite, natural zeolite, activated zeolite, pyrolytic biomass charcoal, polyvinyl alcohol immobilization small ball, modified polyvinyl alcohol, open-cell PU foam, and bacterial cellulose membrane.

[0143] The immobilized carrier of nitrifying bacteria is a functional material specially used for fixing and enriching nitrifying bacteria (such as Nitrosomonas, Nitrobacter, etc.), and its core function is to provide a stable attachment environment for nitrifying bacteria and optimize its growth and metabolism conditions. Experiments show that through the immobilization technology, the denitrification efficiency of nitrifying bacteria in the A / O process is significantly improved, and the concentrations of ammonia nitrogen and total nitrogen are significantly reduced, thereby improving the biological denitrification efficiency.

[0144] The preparation method of the modified polyvinyl alcohol (PVA) comprises the following steps:

[0145] ① A mixed aqueous solution of PVA / SA with a mass ratio of 7:3 is prepared, the total concentration of PVA and SA in the mixed aqueous solution is 8%, and then the mixed aqueous solution is stirred at a constant temperature of 60°C for 10 min;

[0146] ② The mixed aqueous solution is sequentially dropped into CaCl2 solutions with ladder concentrations through a microfluidic device, wherein the ladder concentrations of the CaCl2 solutions include 0.5 mol / L, 1.0 mol / L and 2.0 mol / L in sequence, and gradually increase; each stage is solidified for 15 min to form a heterogeneous structure with a dense shell and a loose core, thereby obtaining the modified polyvinyl alcohol.

[0147] In some embodiments, the lignin carbon source spheres are selected from at least one of an enzymatic hydrolysis lignin carbon sphere, a lignosulfonate carbon sphere, and an industrial lignin carbon sphere.

[0148] The lignin carbon source sphere is a porous carbon sphere material prepared by using lignin (a natural high-molecular polymer in plant cell walls) as raw material through a specific process. This material has high specific surface area, controllable pore structure, and rich surface functional groups, and has wide application in the fields of energy storage, environmental remediation, and catalytic conversion.

[0149] In some embodiments, the denitrifying bacteria embedding gel is selected from at least one of a sodium alginate (SA)-calcium chloride gel, a chitosan-based gel, a starch-PVA composite gel, a polyvinyl alcohol (PVA)-boric acid gel, and a polyurethane (PU) hydrogel.

[0150] The denitrifying bacteria embedding gel is a functional material that fixes denitrifying bacteria (such as Pseudomonas and Paracoccus) in a high-molecular gel network through microencapsulation technology, aiming to improve the denitrification efficiency and solve the problems of carbon source utilization and bacterial population loss in traditional biological denitrification.

[0151] In some embodiments, the oxidation-reduction potential (ORP) sensitive bacteria agent carrier is selected from at least one of Fe3O4 / Fe2O3 gel, magnetic biochar, and iron-sulfur minerals (such as pyrite).

[0152] Oxidation-reduction potential (ORP) sensitive bacteria agent carrier is an intelligent biological material carrier capable of responding to environmental ORP changes and dynamically regulating the activity of functional microorganisms. This kind of carrier realizes the perception and response to the oxidation-reduction potential in water body or soil through material design, so as to optimize the metabolic environment of microorganisms (such as denitrifying bacteria, anaerobic ammonia oxidation bacteria, etc.) and improve the pollutant removal efficiency.

[0153] In some embodiments, the particle size of the sulfur particles is 0.5-1 mm.

[0154] In some embodiments, the particle size of the sponge iron is 2-3 mm.

[0155] In some embodiments, the application of the composite ecological filler for strengthening in-situ denitrification of river water body is also provided.

[0156] In some embodiments, the application of the composite ecological filler for strengthening in-situ denitrification of river water body is also provided.

[0157] The filler device comprises a first filler unit, a second filler unit and a third filler unit which are independent of each other;

[0158] 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.

[0159] In order to make the technical problems, technical solutions and beneficial effects solved by the present application more clear, the composite ecological filler for strengthening in-situ denitrification of river water body, the infiltration system and the application will be further described in detail below in combination with specific embodiments and drawings. Obviously, the specific embodiments described are only part of the embodiments of the present application, not all. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application. Based on the specific embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0160] Unless otherwise specified in the specific embodiments, the technology or conditions are carried out according to the technology or conditions described in the literature in the art or according to the product manual. Unless otherwise specified, the reagents or instruments used are conventional products that can be obtained from the market.

[0161] Embodiment 1

[0162] A filtration system for strengthening in-situ denitrification of river water body is used for a method for denitrification of high ammonia-nitrogen river water body, comprising the following steps:

[0163] S1, a composite ecological filler for preparing a strengthened river water body for in-situ denitrification: the composite ecological filler for preparing a strengthened river water body for in-situ denitrification is composed of 75% of aerobic nitrification filler, 15% of anoxic denitrification filler and 10% of transition regulation filler;

[0164] The aerobic nitrification filler (A-type filler) includes, by mass percentage, 60% of porous basalt, 25% of shale ceramsite, 7.5% of magnesium ammonium phosphate slow-release ball and 7.5% of modified polyvinyl alcohol as a nitrifying bacteria immobilization carrier;

[0165] The anoxic denitrification filler (B-type filler) includes, by mass percentage, 50% of sulfur granules, 25% of lignin carbon source ball, 20% of sponge iron and 5% of sodium alginate (SA)-calcium chloride gel as a denitrifying bacteria embedding gel;

[0166] The transition regulation filler (C-type filler) includes, by mass percentage, 50% of manganese sand, 30% of coconut shell activated carbon and 20% of an oxidation-reduction potential (ORP) sensitive bacteria agent carrier;

[0167] A modified polyvinyl alcohol preparation method, including the following steps:

[0168] 1. preparing 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 being 8%, and then stirring the mixed aqueous solution at a temperature of 60°C for 10 min;

[0169] 2. dropping the mixed aqueous solution into CaCl2 solutions with ladder concentrations through a microfluidic device, wherein the ladder concentrations of the CaCl2 solutions include 0.5 mol / L, 1.0 mol / L and 2.0 mol / L in sequence, gradually increasing; each stage is solidified for 15 min to form a heterogeneous structure with a dense shell and a loose core, thereby obtaining the modified polyvinyl alcohol;

[0170] S2, packing the fillers: as shown in Figure 1 The filler device is a honeycomb-shaped detachable unit, and 75% of the aerobic nitrification filler (A-type filler) prepared in S1 is independently packed into a first filler unit 1 of the filler device with a packing thickness of 90 cm, 15% of the anoxic denitrification filler (B-type filler) is packed into a second filler unit 2 of the filler device with a packing thickness of 135 cm, and 10% of the transition regulation filler (C-type filler) is packed into a third filler unit 3 of the filler device with a packing thickness of 72 cm;

[0171] S3, strengthening a river water body for in-situ denitrification: placing the filler device packed with the fillers in S2 in a high-ammonia-nitrogen river water body, and adding nitrifying bacteria, denitrifying bacteria and oxidation-reduction potential (ORP) sensitive bacteria into the river water body, with a hydraulic load of 1 m 2 / (m 2d), the DO of the water body in the high ammonia-nitrogen river is 5~8 mg / L, the NH3-N is 8 mg / L, the NO3 - -N is 2 mg / L, the water temperature of the water body in the high ammonia-nitrogen river is 25℃.

[0172] S4, after 7 days of stable treatment, the water sample 3 meters downstream of the filler device was collected for determination, and the NH3-N was reduced to 0.5 mg / L, the NO3 - -N was increased to 6 mg / L, and then the composite ecological filler and device were switched;

[0173] The composite ecological filler ratio is as follows: the anaerobic denitrification filler (B type filler) accounts for 65%, the B type filler is loaded into the first filler unit 1 of the filler device, and the loading thickness is 90 cm. The anaerobic denitrification filler includes 55% sulfur granules, 25% lignin carbon source balls, 15% sponge iron, and 5% sodium alginate (SA)-calcium chloride gel according to the mass percentage;

[0174] The aerobic nitrification filler (A type filler) accounts for 15%, the A type filler is loaded into the second filler unit 2 of the filler device, and the loading thickness is 135 cm. The aerobic nitrification filler includes 70% porous basalt and 30% shale ceramsite according to the mass percentage;

[0175] The transition control filler (C type filler) accounts for 20%, the C type filler is loaded into the third filler unit 3 of the filler device, and the loading thickness is 72 cm. The C type filler includes 60% manganese sand and 40% Fe3O4 / biochar according to the mass percentage.

[0176] S5, after 7 days of monitoring, the water quality is determined, and the TN in the river water body is less than 1 mg / L.

[0177] Embodiment 2

[0178] A kind of infiltration system for strengthening river water body in-situ denitrification is used for the method for low temperature high nitrate nitrogen water body denitrification, comprising the following steps:

[0179] S1, preparation of composite ecological filler for strengthening river water body in-situ denitrification: the composite ecological filler for strengthening river water body in-situ denitrification is composed of 85% anaerobic denitrification filler and 15% transition control filler;

[0180] The anaerobic denitrification filler includes 45% sulfur granules, 20% lignin carbon source balls, 10% sponge iron, 20% nano zero-valent iron and 5% denitrifying bacteria embedding gel according to the mass percentage.

[0181] The transition control filler includes 50% manganese sand, 30% activated carbon of coconut shell and 20% oxidation-reduction potential (ORP) sensitive bacteria agent carrier according to the mass percentage.

[0182] S2, filling the filler: as shown in the figure, the filler device is a honeycomb-shaped detachable unit, respectively independently filling 85% of the anoxic denitrification filler prepared in S1 into the first filler unit 1 of the filler device, the filling thickness is 90cm, 15% of the transition control filler is filled into the third filler unit 3 of the filler device, and the filling thickness is 90cm; Figure 1

[0183] S3, strengthening the in-situ denitrification of river water: the filler device filled with the filler in S2 is placed in a low-temperature high-nitrate nitrogen water body, and denitrifying bacteria and oxidation-reduction potential (ORP) sensitive bacteria are added to the river water, the hydraulic load is 1m 2 / (m 2 ·d), the DO of the low-temperature high-nitrate nitrogen water body is 1.5mg / L, the NO3 - -N is 15mg / L, and the water temperature is 6℃.

[0184] During the operation, the sudden rain caused reoxygenation, and the DO increased from 1.5mg / L to 4mg / L, and this process is the DO mutation period.

[0185] At the same time, the filler device filled with all sulfur particles is placed in the same low-temperature high-nitrate nitrogen water body as in Example 2 to perform a control test. The change results of TN removal rate and denitrification rate of the low-temperature high-nitrate nitrogen water body in different DO periods are shown in Table 1 and Table 2.

[0186] Table 1 Change results of TN removal rate and denitrification rate of low-temperature high-nitrate nitrogen water body treated by composite ecological filler in different DO periods

[0187]

[0188] Table 2 Change results of TN removal rate and denitrification rate of low-temperature high-nitrate nitrogen water body treated by sulfur particles in different DO periods

[0189]

[0190] Among them, the recovery period is within 30 minutes of the DO mutation. From the comparative analysis of Table 1 and Table 2, it can be seen that during the DO mutation period, the TN removal rate of the low-temperature high-nitrate nitrogen water body treated by the composite ecological filler only decreases by 12% (from 92% to 73%), and recovers to 85% after 30 minutes. During the stable DO period, the denitrification rate reaches 1.1g N / (m³·h), which is 80% higher than that of the traditional sulfur filler (i.e. the filler device filled with all sulfur particles). Thus, it is proved that the "ORP sensitive dynamic balance" technology proposed in the present application can effectively respond to the DO mutation, and the oxidation-reduction potential response of the C-type filler realizes the innovative low-temperature strengthening strategy (i.e. the low-temperature synergistic effect of nano zero-valent iron and sulfur in Example 2) of DO mutation buffer.

[0191] ​The above embodiments are only the preferred embodiments of the present application for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art based on the present application are within the protection scope of the present application.

Claims

1. A composite ecological filler for enhancing in-situ denitrification of river water, characterized in that, It consists of anoxic denitrification packing and transitional regulating packing, or it consists of aerobic nitrification packing, anoxic denitrification packing and transitional regulating packing; The aerobic nitrification packing material includes inorganic mineral matrix denitrification packing material, bio-ceramic particles, mineral-based slow-release functional materials, and microbial immobilization functional carriers; The anoxic denitrification packing material includes sulfur-based composite electron donor material, slow-release organic carbon source material, zero-valent iron-based environmental remediation material, and denitrifying bacteria encapsulation gel. The transition control packing material includes multifunctional water treatment filter media, activated carbon, and environmentally responsive functional microbial carriers. The inorganic mineral matrix denitrification filler is selected from at least one of volcanic rock, zeolite, diatomite and steel slag; 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. The microbial immobilization functional carrier is selected from at least one of nitrifying bacteria immobilization carrier, polyurethane foam, and sodium alginate-montmorillonite composite gel. The sulfur-based composite electron donor material is selected from at least one of sulfur particles, pyrite, and sodium thiosulfate slow-release spheres. The slow-release organic carbon source material is selected from at least one of lignin carbon source spheres, polycaprolactone and starch-based gel. 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. The multifunctional water treatment filter media is selected from at least one of manganese sand, titanium dioxide coated ceramic particles, and alumina. The environmentally responsive functional microbial carrier is selected from at least one of the following: redox potential-sensitive bacterial agent carrier, pH-responsive bacterial community carrier, and DO gradient-sensing bacterial membrane carrier. The bio-ceramsite is selected from at least one of clay ceramsite, fly ash ceramsite, shale ceramsite, coal gangue ceramsite, and bio-sludge ceramsite; The nitrifying bacteria immobilization carrier is selected from at least one of natural zeolite, activated zeolite, pyrolytic biochar, polyvinyl alcohol immobilized microspheres, modified polyvinyl alcohol, open-cell PU foam, and bacterial cellulose membrane. The lignin carbon source spheres are selected from at least one of enzymatically hydrolyzed lignin carbon spheres, lignin sulfonate carbon spheres, and industrial lignin carbon spheres. The denitrifying bacteria encapsulation gel is selected from at least one of sodium alginate-calcium chloride gel, chitosan-based gel, starch-PVA composite gel, polyvinyl alcohol-boric acid gel and polyurethane hydrogel. The redox potential-sensitive bacterial agent carrier is selected from at least one of Fe3O4 / Fe2O3 gel, magnetic biochar, and iron-sulfur minerals.

2. The composite ecological filler for enhancing in-situ denitrification of river water as described in claim 1, characterized in that, The aerobic nitrification packing material comprises, by weight percentage, 50-70% volcanic rock, 20-30% bio-ceramic particles, 5-10% magnesium ammonium phosphate slow-release balls, and 5-10% nitrifying bacteria immobilization carrier. And / or, the anoxic denitrification packing material, by mass percentage, comprises 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 packing comprises, by weight percentage, 50% manganese sand, 30% coconut shell activated carbon and 20% redox potential sensitive bacterial agent carrier.

3. The composite ecological filler for enhancing in-situ denitrification of river water as described in claim 1, characterized in that, When DO ≥ 4 mg / L and NH3-N / NO3 - When -N>1, the composite ecological packing consists of 70-80% aerobic nitrification packing, 10-15% anoxic denitrification packing, and 5-10% transitional regulating packing. And / or, when DO ≤ 2 mg / L and NO3 - When -N≥5 mg / L, the composite ecological packing consists of 10~20% aerobic nitrification packing, 60~70% anoxic denitrification packing and 15~20% transitional regulating packing. And / or, when the DO change is >2 mg / L per hour, the composite ecological packing consists of 25% aerobic nitrification packing, 25% anoxic denitrification packing and 50% transitional regulating packing.

4. The composite ecological filler for enhancing in-situ denitrification of river water as described in 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 packing consists of anoxic denitrification packing and transitional regulation packing.

5. The composite ecological filler for enhancing in-situ denitrification of river water as described in 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 packing is 30-40%, and the slow-release organic carbon source material is selected from starch-based gel, wherein the C / N ratio of the starch-based gel is 5-8.

6. The composite ecological filler for enhancing in-situ denitrification of river water as described in claim 2, characterized in that, The sulfur particles have a particle size of 0.5~1mm; And / or, the particle size of the sponge iron is 2~3mm.

7. The application of a composite ecological filler for enhancing in-situ denitrification of river water as described in any one of claims 1 to 6 for in-situ denitrification of river water.

8. A river water infiltration system, characterized in that, Includes the composite ecological filler and filler device for enhancing in-situ denitrification of river water as described in any one of claims 1 to 6; The packing device includes a first packing unit, a second packing unit, and a third packing unit that are independent of each other; The first packing unit is filled with aerobic nitrification packing, the second packing unit is filled with anoxic denitrification packing, and the third packing unit is filled with transition control packing.

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